A novel (ex situ) method to quantify oxygen diffusion coefficient of polymer fuel cells backing and catalyst layers

NASA Astrophysics Data System (ADS)

Baricci, Andrea; Casalegno, Andrea

2016-09-01

Limiting current density of oxygen reduction reaction in polymer electrolyte fuel cells is determined by several mass transport resistances that lower the concentration of oxygen on the catalyst active site. Among them, diffusion across porous media plays a significant role. Despite the extensive experimental activity documented in PEMFC literature, only few efforts have been dedicated to the measurement of the effective transport properties in porous layers. In the present work, a methodology for ex situ measurement of the effective diffusion coefficient and Knudsen radius of porous layers for polymer electrolyte fuel cells (gas diffusion layer, micro porous layer and catalyst layer) is described and applied to high temperature polymer fuel cells State of Art materials. Regression of the measured quantities by means of a quasi 2D physical model is performed to quantify the Knudsen effect, which is reported to account, respectively, for 30% and 50% of the mass transport resistance in micro porous layer and catalyst layer. On the other side, the model reveals that pressure gradient consequent to permeation in porous layers of high temperature polymer fuel cells has a negligible effect on oxygen concentration in relevant operating conditions.

An Investigation of the Coefficient of Discharge of Liquids Through Small Round Orifices

NASA Technical Reports Server (NTRS)

Joachim, W F

1926-01-01

The work covered by this report was undertaken in connection with a general investigation of fuel injection engine principles as applied to engines for aircraft propulsion, the specific purpose being to obtain information on the coefficient of discharge of small round orifices suitable for use as fuel injection nozzles. Values for the coefficient were determined for the more important conditions of engine service such as discharge under pressures up to 8,000 pounds per square inch, at temperatures between 80 degrees and 180 degrees F. And into air compressed to pressures up to 1,000 pounds per square inch. The results show that the coefficient ranges between 0.62 and 0.88 for the different test conditions between 1,000 and 8,000 pounds per square inch hydraulic pressure. At lower pressures the coefficient increases materially. It is concluded that within the range of these tests and for hydraulic pressures above 1,000 pound per square inch the coefficient does not change materially with pressure or temperature; that it depends considerably upon the liquid, decreases with increase in orifice size, and increases in the case of discharge into compressed air until the compressed-air pressure equals approximately three-tenths of the hydraulic pressure, beyond which pressure ratio it remains practically constant.

Validation of DRAGON4/DONJON4 simulation methodology for a typical MNSR by calculating reactivity feedback coefficient and neutron flux

NASA Astrophysics Data System (ADS)

Al Zain, Jamal; El Hajjaji, O.; El Bardouni, T.; Boukhal, H.; Jaï, Otman

2018-06-01

The MNSR is a pool type research reactor, which is difficult to model because of the importance of neutron leakage. The aim of this study is to evaluate a 2-D transport model for the reactor compatible with the latest release of the DRAGON code and 3-D diffusion of the DONJON code. DRAGON code is then used to generate the group macroscopic cross sections needed for full core diffusion calculations. The diffusion DONJON code, is then used to compute the effective multiplication factor (keff), the feedback reactivity coefficients and neutron flux which account for variation in fuel and moderator temperatures as well as the void coefficient have been calculated using the DRAGON and DONJON codes for the MNSR research reactor. The cross sections of all the reactor components at different temperatures were generated using the DRAGON code. These group constants were used then in the DONJON code to calculate the multiplication factor and the neutron spectrum at different water and fuel temperatures using 69 energy groups. Only one parameter was changed where all other parameters were kept constant. Finally, Good agreements between the calculated and measured have been obtained for every of the feedback reactivity coefficients and neutron flux.

Effects of cooling system parameters on heat transfer in PAFC stack. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali A.

1985-01-01

Analytical and experimental study for the effects of cooling system parameters on the heat transfer and temperature distribution in the electrode plates of a phosphoric acid fuel-cell has been conducted. An experimental set-up that simulates the operating conditions prevailing in a phosphoric-acid fuel-cell stack was designed and constructed. The set-up was then used to measure the overall heat transfer coefficient, the thermal contact resistance, and the electrode temperature distribution for two different cooling plate configurations. Two types of cooling plate configurations, serpentine and straight, were tested. Air, water, and oil were used as coolants. Measurements for the heat transfer coefficient and the thermal contact resistance were made for various flow rates ranging from 16 to 88 Kg/hr, and stack clamping pressure ranging from O to 3448 Kpa. The experimental results for the overall heat transfer coefficient were utilized to derive mathematical relations for the overall heat transfer coefficient as a function of stack clamping pressure and Reynolds number for the three coolants. The empirically derived formulas were incorporated in a previously developed computer program to predict electrodes temperature distribution and the performance of the stack cooling system. The results obtained were then compared with those available in the literature. The comparison showed maximum deviation of +/- 11%.

Fuels Performance | Transportation Research | NREL

Science.gov Websites

Chemistry. (2014) Saturated Monoglyceride Effects on Low-Temperature Performance of Biodiesel Blends. G.M more energy-efficient vehicles on the road to displace oil consumption, decrease greenhouse gas . (2013) Ignition Quality Tester (IQT) Investigation of the Negative Temperature Coefficient Region of

MOLTEN FLUORIDE NUCLEAR REACTOR FUEL

DOEpatents

Barton, C.J.; Grimes, W.R.

1960-01-01

Molten-salt reactor fuel compositions consisting of mixtures of fluoride salts are reported. In its broadest form, the composition contains an alkali fluoride such as sodium fluoride, zirconium tetrafluoride, and a uranium fluoride, the latter being the tetrafluoride or trifluoride or a mixture of the two. An outstanding property of these fuel compositions is a high coeffieient of thermal expansion which provides a negative temperature coefficient of reactivity in reactors in which they are used.

Forest fire danger index based on modifying Nesterov Index, fuel, and anthropogenic activities using MODIS TERRA, AQUA and TRMM satellite datasets

NASA Astrophysics Data System (ADS)

Suresh Babu, K. V.; Roy, Arijit; Ramachandra Prasad, P.

2016-05-01

Forest fire has been regarded as one of the major causes of degradation of Himalayan forests in Uttarakhand. Forest fires occur annually in more than 50% of forests in Uttarakhand state, mostly due to anthropogenic activities and spreads due to moisture conditions and type of forest fuels. Empirical drought indices such as Keetch-Byram drought index, the Nesterov index, Modified Nesterov index, the Zhdanko index which belongs to the cumulative type and the Angstrom Index which belongs to the daily type have been used throughout the world to assess the potential fire danger. In this study, the forest fire danger index has been developed from slightly modified Nesterov index, fuel and anthropogenic activities. Datasets such as MODIS TERRA Land Surface Temperature and emissivity (MOD11A1), MODIS AQUA Atmospheric profile product (MYD07) have been used to determine the dew point temperature and land surface temperature. Precipitation coefficient has been computed from Tropical Rainfall measuring Mission (TRMM) product (3B42RT). Nesterov index has been slightly modified according to the Indian context and computed using land surface temperature, dew point temperature and precipitation coefficient. Fuel type danger index has been derived from forest type map of ISRO based on historical fire location information and disturbance danger index has been derived from disturbance map of ISRO. Finally, forest fire danger index has been developed from the above mentioned indices and MODIS Thermal anomaly product (MOD14) has been used for validating the forest fire danger index.

TEMperature Pressure ESTimation of a homogeneous boiling fuel-steel mixture in an LMFBR core. [TEMPEST code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pyun, J.J.; Majumdar, D.

The paper describes TEMPEST, a simple computer program for the temperature and pressure estimation of a boiling fuel-steel pool in an LMFBR core. The time scale of interest of this program is large, of the order of ten seconds. Further, the vigorous boiling in the pool will generate a large contact, and hence a large heat transfer between fuel and steel. The pool is assumed to be a uniform mixture of fuel and steel, and consequently vapor production is also assumed to be uniform throughout the pool. The pool is allowed to expand in volume if there is steel meltingmore » at the walls. In this program, the total mass of liquid and vapor fuel is always kept constant, but the total steel mass in the pool may change by steel wall melting. Because of a lack of clear understanding of the physical phenomena associated with the progression of a fuel-steel mixture at high temperature, various input options have been built-in to enable one to perform parametric studies. For example, the heat transfer from the pool to the surrounding steel structure may be controlled by input values for the heat transfer coefficients, or, the heat transfer may be calculated by a correlation obtained from the literature. Similarly, condensation of vapor on the top wall can be specified by input values of the condensation coefficient; the program can otherwise calculate condensation according to the non-equilibrium model predictions. Meltthrough rates of the surrounding steel walls can be specified by a fixed melt-rate or can be determined by a fraction of the heat loss that goes to steel-melting. The melted steel is raised to the pool temperature before it is joined with the pool material. Several applications of this program to various fuel-steel pools in the FFTF and the CRBR cores are discussed.« less

A fission gas release correlation for uranium nitride fuel pins

NASA Technical Reports Server (NTRS)

Weinstein, M. B.; Davison, H. W.

1973-01-01

A model was developed to predict fission gas releases from UN fuel pins clad with various materials. The model was correlated with total release data obtained by different experimentors, over a range of fuel temperatures primarily between 1250 and 1660 K, and fuel burnups up to 4.6 percent. In the model, fission gas is transported by diffusion mechanisms to the grain boundaries where the volume grows and eventually interconnects with the outside surface of the fuel. The within grain diffusion coefficients are found from fission gas release rate data obtained using a sweep gas facility.

Experimental investigations of heat transfer and temperature fields in models simulating fuel assemblies used in the core of a nuclear reactor with a liquid heavy-metal coolant

NASA Astrophysics Data System (ADS)

Belyaev, I. A.; Genin, L. G.; Krylov, S. G.; Novikov, A. O.; Razuvanov, N. G.; Sviridov, V. G.

2015-09-01

The aim of this experimental investigation is to obtain information on the temperature fields and heat transfer coefficients during flow of liquid-metal coolant in models simulating an elementary cell in the core of a liquid heavy metal cooled fast-neutron reactor. Two design versions for spacing fuel rods in the reactor core were considered. In the first version, the fuel rods were spaced apart from one another using helical wire wound on the fuel rod external surface, and in the second version spacer grids were used for the same purpose. The experiments were carried out on the mercury loop available at the Moscow Power Engineering Institute National Research University's Chair of Engineering Thermal Physics. Two experimental sections simulating an elementary cell for each of the fuel rod spacing versions were fabricated. The temperature fields were investigated using a dedicated hinged probe that allows temperature to be measured at any point of the studied channel cross section. The heat-transfer coefficients were determined using the wall temperature values obtained at the moment when the probe thermocouple tail end touched the channel wall. Such method of determining the wall temperature makes it possible to alleviate errors that are unavoidable in case of measuring the wall temperature using thermocouples placed in slots milled in the wall. In carrying out the experiments, an automated system of scientific research was applied, which allows a large body of data to be obtained within a short period of time. The experimental investigations in the first test section were carried out at Re = 8700, and in the second one, at five values of Reynolds number. Information about temperature fields was obtained by statistically processing the array of sampled probe thermocouple indications at 300 points in the experimental channel cross section. Reach material has been obtained for verifying the codes used for calculating velocity and temperature fields in channels with an intricately shaped cross section simulating the flow pass sections for liquid-metal coolants cooling the core of nuclear reactors.

Apparatus and method for controlling the secondary injection of fuel

DOEpatents

Martin, Scott M.; Cai, Weidong; Harris, Jr., Arthur J.

2013-03-05

A combustor (28) for a gas turbine engine is provided comprising a primary combustion chamber (30) for combusting a first fuel to form a combustion flow stream (50) and a transition piece (32) located downstream from the primary combustion chamber (30). The transition piece (32) comprises a plurality of injectors (66) located around a circumference of the transition piece (32) for injecting a second fuel into the combustion flow stream (50). The injectors (66) are effective to create a radial temperature profile (74) at an exit (58) of the transition piece (32) having a reduced coefficient of variation relative to a radial temperature profile (64) at an inlet (54) of the transition piece (32). Methods for controlling the temperature profile of a secondary injection are also provided.

Thermal Aspects of Using Alternative Nuclear Fuels in Supercritical Water-Cooled Reactors

NASA Astrophysics Data System (ADS)

Grande, Lisa Christine

A SuperCritical Water-cooled Nuclear Reactor (SCWR) is a Generation IV concept currently being developed worldwide. Unique to this reactor type is the use of light-water coolant above its critical point. The current research presents a thermal-hydraulic analysis of a single fuel channel within a Pressure Tube (PT)-type SCWR with a single-reheat cycle. Since this reactor is in its early design phase many fuel-channel components are being investigated in various combinations. Analysis inputs are: steam cycle, Axial Heat Flux Profile (AHFP), fuel-bundle geometry, and thermophysical properties of reactor coolant, fuel sheath and fuel. Uniform and non-uniform AHFPs for average channel power were applied to a variety of alternative fuels (mixed oxide, thorium dioxide, uranium dicarbide, uranium nitride and uranium carbide) enclosed in an Inconel-600 43-element bundle. The results depict bulk-fluid, outer-sheath and fuel-centreline temperature profiles together with the Heat Transfer Coefficient (HTC) profiles along the heated length of fuel channel. The objective is to identify the best options in terms of fuel, sheath material and AHFPS in which the outer-sheath and fuel-centreline temperatures will be below the accepted temperature limits of 850°C and 1850°C respectively. The 43-element Inconel-600 fuel bundle is suitable for SCWR use as the sheath-temperature design limit of 850°C was maintained for all analyzed cases at average channel power. Thoria, UC2, UN and UC fuels for all AHFPs are acceptable since the maximum fuel-centreline temperature does not exceed the industry accepted limit of 1850°C. Conversely, the fuel-centreline temperature limit was exceeded for MOX at all AHFPs, and UO2 for both cosine and downstream-skewed cosine AHFPs. Therefore, fuel-bundle modifications are required for UO2 and MOX to be feasible nuclear fuels for SCWRs.

Numerical Study on Influence of Cross Flow on Rewetting of AHWR Fuel Bundle

PubMed Central

Kumar, Mithilesh; Mukhopadhyay, D.; Ghosh, A. K.; Kumar, Ravi

2014-01-01

Numerical study on AHWR fuel bundle has been carried out to assess influence of circumferential and cross flow rewetting on the conduction heat transfer. The AHWR fuel bundle quenching under accident condition is designed primarily with radial jets at several axial locations. A 3D (r, θ, z) transient conduction fuel pin model has been developed to carry out the study with a finite difference method (FDM) technique with alternating direction implicit (ADI) scheme. The single pin has been considered to study effect of circumferential conduction and multipins have been considered to study the influence of cross flow. Both analyses are carried out with the same fluid temperature and heat transfer coefficients as boundary conditions. It has been found from the analyses that, for radial jet, the circumferential conduction is significant and due to influence of overall cross flow the reductions in fuel temperature in the same quench plane in different rings are different with same initial surface temperature. Influence of cross flow on rewetting is found to be very significant. Outer fuel pins rewetting time is higher than inner. PMID:24672341

Theoretical performance of liquid hydrogen and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid hydrogen and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion-chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ration of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 364.6 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Theoretical performance of liquid ammonia and liquid fluorine as a rocket propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Huff, Vearl N

1953-01-01

Theoretical values of performance parameters for liquid ammonia and liquid fluorine as a rocket propellant were calculated on the assumption of equilibrium composition during the expansion process for a wide range of fuel-oxidant and expansion ratios. The parameters included were specific impulse, combustion chamber temperature, nozzle-exit temperature, equilibrium composition, mean molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, coefficient of viscosity, and coefficient of thermal conductivity. The maximum value of specific impulse was 311.5 pound-seconds per pound for a chamber pressure of 300 pounds per square inch absolute (20.41 atm) and an exit pressure of 1 atmosphere.

Temperature sensitivity study of eddy current and digital gauge probes for nuclear fuel rod oxide measurement

NASA Astrophysics Data System (ADS)

Beck, Faith R.; Lind, R. Paul; Smith, James A.

2018-04-01

Novel fuels are part of the nationwide effort to reduce the enrichment of Uranium for energy production. Performance of such fuels is determined by irradiating their surfaces. To test irradiated samples, the instrumentation must operate remotely. The plate checker used in this experiment at Idaho National Lab (INL) performs non-destructive testing on fuel rod and plate geometries with two different types of sensors: eddy current and digital thickness gauges. The sensors measure oxide growth and total sample thickness on research fuels, respectively. Sensor measurement accuracy is crucial because even 10 microns of error is significant when determining the viability of an experimental fuel. One parameter known to affect the eddy current and thickness gauge sensors is temperature. Since both sensor accuracies depend on the ambient temperature of the system, the plate checker has been characterized for these sensitivities. The manufacturer of the digital gauge probes has noted a rather large coefficient of thermal expansion for their linear scale. It should also be noted that the accuracy of the digital gauge probes are specified at 20°C, which is approximately 7°C cooler than the average hot-cell temperature. In this work, the effect of temperature on the eddy current and digital gauge probes is studied, and thickness measurements are given as empirical functions of temperature.

Measuring air core characteristics of a pressure-swirl atomizer via a transparent acrylic nozzle at various Reynolds numbers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Eun J.; Oh, Sang Youp; Kim, Ho Y.

2010-11-15

Because of thermal fluid-property dependence, atomization stability (or flow regime) can change even at fixed operating conditions when subject to temperature change. Particularly at low temperatures, fuel's high viscosity can prevent a pressure-swirl (or simplex) atomizer from sustaining a centrifugal-driven air core within the fuel injector. During disruption of the air core inside an injector, spray characteristics outside the nozzle reflect a highly unstable, nonlinear mode where air core length, Sauter mean diameter (SMD), cone angle, and discharge coefficient variability. To better understand injector performance, these characteristics of the pressure-swirl atomizer were experimentally investigated and data were correlated to Reynoldsmore » numbers (Re). Using a transparent acrylic nozzle, the air core length, SMD, cone angle, and discharge coefficient are observed as a function of Re. The critical Reynolds numbers that distinguish the transition from unstable mode to transitional mode and eventually to a stable mode are reported. The working fluids are diesel and a kerosene-based fuel, referred to as bunker-A. (author)« less

The Reduced Effectiveness of EGR to Mitigate Knock at High Loads in Boosted SI Engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szybist, James P.; Wagnon, Scott W.; Splitter, Derek A.

Numerous studies have demonstrated that exhaust gas recirculation (EGR) can attenuate knock propensity in spark ignition (SI) engines at naturally aspirated or lightly boosted conditions. In this paper, we investigate the role of cooled EGR under higher load conditions with multiple fuel compositions, where highly retarded combustion phasing typical of modern SI engines was used. It was found that under these conditions, EGR attenuation of knock is greatly reduced, where EGR doesn’t allow significant combustion phasing advance as it does under lighter load conditions. Detailed combustion analysis shows that when EGR is added, the polytropic coefficient increases causing the compressivemore » pressure and temperature to increase. At sufficiently highly boosted conditions, the increase in polytropic coefficient and additional trapped mass from EGR can sufficiently reduce fuel ignition delay to overcome knock attenuation effects. Kinetic modeling demonstrates that the effectiveness of EGR to mitigate knock is highly dependent on the pressure-temperature condition. Experiments at 2000 rpm have confirmed reduced fuel ignition delay under highly boosted conditions relevant to modern downsized boosted SI engines, where in-cylinder pressure is higher and the temperature is cooler. Finally, at these conditions, charge reactivity increases compared to naturally aspirated conditions, and attenuation of knock by EGR is reduced.« less

The Reduced Effectiveness of EGR to Mitigate Knock at High Loads in Boosted SI Engines

DOE PAGES

Szybist, James P.; Wagnon, Scott W.; Splitter, Derek A.; ...

2017-09-04

Numerous studies have demonstrated that exhaust gas recirculation (EGR) can attenuate knock propensity in spark ignition (SI) engines at naturally aspirated or lightly boosted conditions. In this paper, we investigate the role of cooled EGR under higher load conditions with multiple fuel compositions, where highly retarded combustion phasing typical of modern SI engines was used. It was found that under these conditions, EGR attenuation of knock is greatly reduced, where EGR doesn’t allow significant combustion phasing advance as it does under lighter load conditions. Detailed combustion analysis shows that when EGR is added, the polytropic coefficient increases causing the compressivemore » pressure and temperature to increase. At sufficiently highly boosted conditions, the increase in polytropic coefficient and additional trapped mass from EGR can sufficiently reduce fuel ignition delay to overcome knock attenuation effects. Kinetic modeling demonstrates that the effectiveness of EGR to mitigate knock is highly dependent on the pressure-temperature condition. Experiments at 2000 rpm have confirmed reduced fuel ignition delay under highly boosted conditions relevant to modern downsized boosted SI engines, where in-cylinder pressure is higher and the temperature is cooler. Finally, at these conditions, charge reactivity increases compared to naturally aspirated conditions, and attenuation of knock by EGR is reduced.« less

Effects of iso-octane/ethanol blend ratios on the observance of negative temperature coefficient behavior within the Ignition Quality Tester

DOE PAGES

Bogin, Jr., Gregory E.; Luecke, Jon; Ratcliff, Matthew A.; ...

2016-08-21

Here, an ignition delay study investigating the reduction in low temperature heat release (LTHR) and negative temperature coefficient (NTC) region with increasing ethanol concentration in binary blends of ethanol/isooctane was conducted in the Ignition Quality Tester (IQT). The IQT is advantageous for studying multi-component fuels such as iso-octane/ethanol which are difficult to study at lower temperatures covering the NTC region in traditional systems (e.g., shock tubes, rapid compression machines, etc.). The high octane numbers and concomitant long ignition delay times of ethanol and iso-octane are ideal for study in the IQT allowing the system to reach a quasi-homogeneous mixture; allowingmore » the effect of fuel chemistry on ignition delay to be investigated with minimal impact from the fuel spray due to the relatively long ignition times. NTC behavior from iso-octane/ethanol blends was observed for the first time using an IQT. Temperature sweeps of iso-octane/ethanol volumetric blends (100/0, 90/10, 80/20, 50/50, and 0/100) were conducted from 623 to 993 K at 0.5, 1.0 and 1.5 MPa and global equivalence ratios ranging from 0.7 to 1.0. Ignition of the iso-octane/ethanol blends in the IQT was also modeled using a 0-D homogeneous batch reactor model. Significant observations include: (1) NTC behavior was observed for ethanol/ iso-octane fuel blends up to 20% ethanol. (2) Ethanol produced shorter ignition delay times than iso-octane in the high temperature region. (3) The initial increase in ethanol from 0% to 10% had a lesser impact on ignition delay than increasing ethanol from 10% to 20%. (4) The 0-D model predicts that at 0.5 and 1.0 MPa ethanol produces the shortest ignition time in the high-temperature regime, as seen experimentally.« less

Effects of iso-octane/ethanol blend ratios on the observance of negative temperature coefficient behavior within the Ignition Quality Tester

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bogin, Jr., Gregory E.; Luecke, Jon; Ratcliff, Matthew A.

Here, an ignition delay study investigating the reduction in low temperature heat release (LTHR) and negative temperature coefficient (NTC) region with increasing ethanol concentration in binary blends of ethanol/isooctane was conducted in the Ignition Quality Tester (IQT). The IQT is advantageous for studying multi-component fuels such as iso-octane/ethanol which are difficult to study at lower temperatures covering the NTC region in traditional systems (e.g., shock tubes, rapid compression machines, etc.). The high octane numbers and concomitant long ignition delay times of ethanol and iso-octane are ideal for study in the IQT allowing the system to reach a quasi-homogeneous mixture; allowingmore » the effect of fuel chemistry on ignition delay to be investigated with minimal impact from the fuel spray due to the relatively long ignition times. NTC behavior from iso-octane/ethanol blends was observed for the first time using an IQT. Temperature sweeps of iso-octane/ethanol volumetric blends (100/0, 90/10, 80/20, 50/50, and 0/100) were conducted from 623 to 993 K at 0.5, 1.0 and 1.5 MPa and global equivalence ratios ranging from 0.7 to 1.0. Ignition of the iso-octane/ethanol blends in the IQT was also modeled using a 0-D homogeneous batch reactor model. Significant observations include: (1) NTC behavior was observed for ethanol/ iso-octane fuel blends up to 20% ethanol. (2) Ethanol produced shorter ignition delay times than iso-octane in the high temperature region. (3) The initial increase in ethanol from 0% to 10% had a lesser impact on ignition delay than increasing ethanol from 10% to 20%. (4) The 0-D model predicts that at 0.5 and 1.0 MPa ethanol produces the shortest ignition time in the high-temperature regime, as seen experimentally.« less

Performance Charts for a Turbojet System

NASA Technical Reports Server (NTRS)

Karp, Irving M.

1947-01-01

Convenient charts are presented for computing the thrust, fuel consumption, and other performance values of a turbojet system. These charts take into account the effects of ram pressure, compressor pressure ratio, ratio of combustion-chamber-outlet temperature to atmospheric temperature, compressor efficiency, turbine efficiency, combustion efficiency, discharge-nozzle coefficient, losses in total pressure in the inlet to the jet-propulsion unit and in the combustion chamber, and variation in specific heats with temperature. The principal performance charts show clearly the effects of the primary variables and correction charts provide the effects of the secondary variables. The performance of illustrative cases of turbojet systems is given. It is shown that maximum thrust per unit mass rate of air flow occurs at a lower compressor pressure ratio than minimum specific fuel consumption. The thrust per unit mass rate of air flow increases as the combustion-chamber discharge temperature increases. For minimum specific fuel consumption, however, an optimum combustion-chamber discharge temperature exists, which in some cases may be less than the limiting temperature imposed by the strength temperature characteristics of present materials.

ICP-MS measurement of silver diffusion coefficient in graphite IG-110 between 1048K and 1284K

NASA Astrophysics Data System (ADS)

Carter, L. M.; Seelig, J. D.; Brockman, J. D.; Robertson, J. D.; Loyalka, S. K.

2018-01-01

Silver-110m has been shown to permeate intact silicon carbide and pyrolytic carbon coating layers of the TRISO fuel particles during normal High Temperature Gas-Cooled Reactor (HTGR) operational conditions. The diffusion coefficients for silver in graphite IG-110 measured using a release method designed to simulate HTGR conditions of high temperature and flowing helium in the temperature range 1048-1253 K are reported. The measurements were made using spheres milled from IG-110 graphite that were infused with silver using a pressure vessel technique. The Ag diffusion was measured using a time release technique with an ICP-MS instrument for detection. The results of this work are:

Effect of Reynolds number variation on aerodynamics of a hydrogen-fueled transport concept at Mach 6

NASA Technical Reports Server (NTRS)

Penland, Jim A.; Marcum, Don C., Jr.

1987-01-01

Two separate tests have been made on the same blended wing-body hydrogen-fueled transport model at a Mach number of about 6 and a range of Reynolds number (based on theoretical body length) of 1.577 to 55.36 X 10 to the 6th power. The results of these tests, made in a conventional hypersonic blowdown tunnel and a hypersonic shock tunnel, are presented through a range of angle of attack from -1 to 8 deg, with an extended study at a constant angle of attack of 3 deg. The model boundary layer flow appeared to be predominately turbulent except for the low Reynolds number shock tunnel tests. Model wall temperatures varied considerably; the blowdown tunnel varied from about 255 F to 340 F, whereas the shock tunnel had a constant 70 F model wall temperature. The experimental normal-force coefficients were essentially independent of Reynolds number. A current theoretical computer program was used to study the effect of Reynolds number. Theoretical predictions of normal-force coefficients were good, particularly at anticipated cruise angles of attack, that is 2 to 5 deg. Axial-force coefficients were generally underestimated for the turbulent skin friction conditions, and pitching-moment coefficients could not be predicted reliably.

Deposit formation and heat transfer in hydrocarbon rocket fuels

NASA Technical Reports Server (NTRS)

Giovanetti, A. J.; Spadaccini, L. J.; Szetela, E. J.

1983-01-01

An experimental research program was undertaken to investigate the thermal stability and heat transfer characteristics of several hydrocarbon fuels under conditions that simulate high-pressure, rocket engine cooling systems. The rates of carbon deposition in heated copper and nickel-plated copper tubes were determined for RP-1, propane, and natural gas using a continuous flow test apparatus which permitted independent variation and evaluation of the effect on deposit formation of wall temperature, fuel pressure, and fuel velocity. In addition, the effects of fuel additives and contaminants, cryogenic fuel temperatures, and extended duration testing with intermittent operation were examined. Parametric tests to map the thermal stability characteristics of RP-1, commercial-grade propane, and natural gas were conducted at pressures of 6.9 to 13.8 MPa, bulk fuel velocities of 30 to 90 m/s, and tube wall temperatures in the range of 230 to 810 K. Also, tests were run in which propane and natural gas fuels were chilled to 230 and 160 K, respectively. Corrosion of the copper tube surface was detected for all fuels tested. Plating the inside of the copper tubes with nickel reduced deposit formation and eliminated tube corrosion in most cases. The lowest rates of carbon deposition were obtained for natural gas, and the highest rates were obtained for propane. For all fuels tested, the forced-convection heat transfer film coefficients were satisfactorily correlated using a Nusselt-Reynolds-Prandtl number equation.

An experimental study of the autoignition characteristics of conventional jet fuel/oxidizer mixtures: Jet-A and JP-8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Kamal; Sung, Chih-Jen

2010-04-15

Ignition delay times of Jet-A/oxidizer and JP-8/oxidizer mixtures are measured using a heated rapid compression machine at compressed charge pressures corresponding to 7, 15, and 30 bar, compressed temperatures ranging from 650 to 1100 K, and equivalence ratios varying from 0.42 to 2.26. When using air as the oxidant, two oxidizer-to-fuel mass ratios of 13 and 19 are investigated. To achieve higher compressed temperatures for fuel lean mixtures (equivalence ratio of {proportional_to}0.42), argon dilution is also used and the corresponding oxidizer-to-fuel mass ratio is 84.9. For the conditions studied, experimental results show two-stage ignition characteristics for both Jet-A and JP-8.more » Variations of both the first-stage and overall ignition delays with compressed temperature, compressed pressure, and equivalence ratio are reported and correlated. It is noted that the negative temperature coefficient phenomenon becomes more prominent at relatively lower pressures. Furthermore, the first-stage-ignition delay is found to be less sensitive to changes in equivalence ratio and primarily dependent on temperature. (author)« less

Wall-temperature effects on the aerodynamics of a hydrogen-fueled transport concept in Mach 8 blowdown and shock tunnels

NASA Technical Reports Server (NTRS)

Penland, J. A.; Marcum, D. C., Jr.; Stack, S. H.

1983-01-01

Results are presented from two separate tests on the same blended wing-body hydrogen fueled transport model at a Mach number of about 8 and a range of Reynolds numbers (based on theoretical body length) of 0.597 x 10 to the 6th power to about 156.22 x 10 to the 6th power. Tests were made in conventional hypersonic blowdown tunnel and a hypersonic shock tunnel at angles of attack of -2 deg to about 8 deg, with an extensive study made at a constant angle of attack of 3 deg. The model boundary-layer flow varied from laminar at the lower Reynolds numbers to predominantly turbulent at the higher Reynolds numbers. Model wall temperatures and stream static temperatures varied widely between the two tests, particularly at the lower Reynolds numbers. These temperature differences resulted in marked variations of the axial-force coefficients between the two tests, due in part to the effects of induced pressure and viscous interaction variations. The normal-force coefficient was essentially independent of Reynolds number. Analysis of results utilized current theoretical computer programs and basic boundary-layer theory.

Pressure and temperature effects on fuels with varying octane sensitivity at high load in SI engines

DOE PAGES

Szybist, James P.; Splitter, Derek A.

2017-01-06

The octane sensitivity (S), defined as the difference between the Research Octane Number (RON) and the Motor Octane Number (MON), is of increasing interest in spark ignition (SI) engines because of its relevance to knock resistance at boosted high load conditions. In this study, three fuels with nearly constant RON (99.2-100) and varying S (S = 0, 6.5, and 12) are operated at the knock limited spark advance (KLSA) at nominal engine loads of 10, 15, and 20 bar IMEP in a single cylinder SI engine with side-mount direct injection fueling, at λ =1 stoichiometry. At each load condition, themore » intake manifold temperature is swept from 35 °C to 95 °C to alter the temperature and pressure history of the charge. Results show that at the 10 bar IMEP condition, knock resistance is inversely proportional to fuel S where the S=0 fuel is the most knock resist, but as load increases the trend reverses and knock resistance becomes proportional to fuel S, and the S=12 fuel is the most knock resistant. The reversal of knock resistance as a function of S with load it is attributed to changing fuel ignition delay, as bulk gas intermediate temperature heat release (ITHR) is observed for the S = 0 several crank angles prior to the spark command and ITHR magnitude is a function of increasing intake temperature. As intake temperature continued to increase, the S=0 fuel transitioned from ITHR to low-temperature heat release (LTHR) prior to the spark event. At the highest load and intake temperature, 95 C, the S=0 fuel exhibits distinct LTHR and negative temperature coefficient (NTC), and the intermediate S value fuel (S=6.5) exhibited distinct ITHR behavior several crank angles prior to the spark command. However, for the tested conditions, the S=12 fuel exhibits neither ITHR nor LTHR. To understand the measured trends, chemical kinetic modeling is used to elucidate the fuel specific dependencies on in-cylinder temperature and pressure history. Lastly, the bulk gas composition change that occurs for fuels and conditions exhibiting ITHR and LTHR is analyzed in the modeling, including their implications on flame speed and combustion stability at late phasing. Furthermore, the combined findings illustrate the commonality and utility of fuel S, ITHR, LTHR, and NTC across a wide range of conditions, and the associated implications of fuel S in highly boosted modern GDI SI engines relative to the RON and MON tests.« less

Factors influencing indoor PM2.5 concentration in rural houses of northern China

NASA Astrophysics Data System (ADS)

Zhang, Xueyan; Chen, Bin

2018-02-01

In traditional houses in rural areas of Northern China, most traditional heating systems, heated by mini-stove in the kitchen, usually take agricultural residues as fuels resources. Besides, burning cave under the ground-floor of a rural house is also widely used. The higher PM2.5 concentration is crisis for human health. In this study, PM2.5 concentration, temperature, relative humidity inside and outside the houses have been measured, moreover the factors impact on I/O rate coefficient has been discussed. The results show that the I/O rate coefficient in the evening is 2.5 times greater than the I/O rate coefficient in the daytime. I/O rate coefficient of PM2.5 concentration is positive related to air temperature difference between indoor and outdoor. In addition, the impact of outdoor wind speed and predominant wind direction on the PM2.5 emission has been studied.

Pebble Bed Reactors Design Optimization Methods and their Application to the Pebble Bed Fluoride Salt Cooled High Temperature Reactor (PB-FHR)

NASA Astrophysics Data System (ADS)

Cisneros, Anselmo Tomas, Jr.

The Fluoride salt cooled High temperature Reactor (FHR) is a class of advanced nuclear reactors that combine the robust coated particle fuel form from high temperature gas cooled reactors, direct reactor auxillary cooling system (DRACS) passive decay removal of liquid metal fast reactors, and the transparent, high volumetric heat capacitance liquid fluoride salt working fluids---flibe (33%7Li2F-67%BeF)---from molten salt reactors. This combination of fuel and coolant enables FHRs to operate in a high-temperature low-pressure design space that has beneficial safety and economic implications. In 2012, UC Berkeley was charged with developing a pre-conceptual design of a commercial prototype FHR---the Pebble Bed- Fluoride Salt Cooled High Temperature Reactor (PB-FHR)---as part of the Nuclear Energy University Programs' (NEUP) integrated research project. The Mark 1 design of the PB-FHR (Mk1 PB-FHR) is 236 MWt flibe cooled pebble bed nuclear heat source that drives an open-air Brayton combine-cycle power conversion system. The PB-FHR's pebble bed consists of a 19.8% enriched uranium fuel core surrounded by an inert graphite pebble reflector that shields the outer solid graphite reflector, core barrel and reactor vessel. The fuel reaches an average burnup of 178000 MWt-d/MT. The Mk1 PB-FHR exhibits strong negative temperature reactivity feedback from the fuel, graphite moderator and the flibe coolant but a small positive temperature reactivity feedback of the inner reflector and from the outer graphite pebble reflector. A novel neutronics and depletion methodology---the multiple burnup state methodology was developed for an accurate and efficient search for the equilibrium composition of an arbitrary continuously refueled pebble bed reactor core. The Burnup Equilibrium Analysis Utility (BEAU) computer program was developed to implement this methodology. BEAU was successfully benchmarked against published results generated with existing equilibrium depletion codes VSOP and PEBBED for a high temperature gas cooled pebble bed reactor. Three parametric studies were performed for exploring the design space of the PB-FHR---to select a fuel design for the PB-FHR] to select a core configuration; and to optimize the PB-FHR design. These parametric studies investigated trends in the dependence of important reactor performance parameters such as burnup, temperature reactivity feedback, radiation damage, etc on the reactor design variables and attempted to understand the underlying reactor physics responsible for these trends. A pebble fuel parametric study determined that pebble fuel should be designed with a carbon to heavy metal ratio (C/HM) less than 400 to maintain negative coolant temperature reactivity coefficients. Seed and thorium blanket-, seed and inert pebble reflector- and seed only core configurations were investigated for annular FHR PBRs---the C/HM of the blanket pebbles and discharge burnup of the thorium blanket pebbles were additional design variable for core configurations with thorium blankets. Either a thorium blanket or graphite pebble reflector is required to shield the outer graphite reflector enough to extend its service lifetime to 60 EFPY. The fuel fabrication costs and long cycle lengths of the thorium blanket fuel limit the potential economic advantages of using a thorium blanket. Therefore, the seed and pebble reflector core configuration was adopted as the baseline core configuration. Multi-objective optimization with respect to economics was performed for the PB-FHR accounting for safety and other physical design constraints derived from the high-level safety regulatory criteria. These physical constraints were applied along in a design tool, Nuclear Application Value Estimator, that evaluated a simplified cash flow economics model based on estimates of reactor performance parameters calculated using correlations based on the results of parametric design studies for a specific PB-FHR design and a set of economic assumptions about the electricity market to evaluate the economic implications of design decisions. The optimal PB-FHR design---Mark 1 PB-FHR---is described along with a detailed summary of its performance characteristics including: the burnup, the burnup evolution, temperature reactivity coefficients, the power distribution, radiation damage distributions, control element worths, decay heat curves and tritium production rates. The Mk1 PB-FHR satisfies the PB-FHR safety criteria. The fuel, moderator (pebble core, pebble shell, graphite matrix, TRISO layers) and coolant have global negative temperature reactivity coefficients and the fuel temperatures are well within their limits.

Feasibility study on AFR-100 fuel conversion from uranium-based fuel to thorium-based fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heidet, F.; Kim, T.; Grandy, C.

2012-07-30

Although thorium has long been considered as an alternative to uranium-based fuels, most of the reactors built to-date have been fueled with uranium-based fuel with the exception of a few reactors. The decision to use uranium-based fuels was initially made based on the technology maturity compared to thorium-based fuels. As a result of this experience, lot of knowledge and data have been accumulated for uranium-based fuels that made it the predominant nuclear fuel type for extant nuclear power. However, following the recent concerns about the extent and availability of uranium resources, thorium-based fuels have regained significant interest worldwide. Thorium ismore » more abundant than uranium and can be readily exploited in many countries and thus is now seen as a possible alternative. As thorium-based fuel technologies mature, fuel conversion from uranium to thorium is expected to become a major interest in both thermal and fast reactors. In this study the feasibility of fuel conversion in a fast reactor is assessed and several possible approaches are proposed. The analyses are performed using the Advanced Fast Reactor (AFR-100) design, a fast reactor core concept recently developed by ANL. The AFR-100 is a small 100 MW{sub e} reactor developed under the US-DOE program relying on innovative fast reactor technologies and advanced structural and cladding materials. It was designed to be inherently safe and offers sufficient margins with respect to the fuel melting temperature and the fuel-cladding eutectic temperature when using U-10Zr binary metal fuel. Thorium-based metal fuel was preferred to other thorium fuel forms because of its higher heavy metal density and it does not need to be alloyed with zirconium to reduce its radiation swelling. The various approaches explored cover the use of pure thorium fuel as well as the use of thorium mixed with transuranics (TRU). Sensitivity studies were performed for the different scenarios envisioned in order to determine the best core performance characteristics for each of them. With the exception of the fuel type and enrichment, the reference AFR-100 core design characteristics were kept unchanged, including the general core layout and dimensions, assembly dimensions, materials and power rating. In addition, the mass of {sup 235}U required was kept within a reasonable range from that of the reference AFR-100 design. The core performance characteristics, kinetics parameters and reactivity feedback coefficients were calculated using the ANL suite of fast reactor analysis code systems. Orifice design calculations and the steady-state thermal-hydraulic analyses were performed using the SE2-ANL code. The thermal margins were evaluated by comparing the peak temperatures to the design limits for parameters such as the fuel melting temperature and the fuel-cladding eutectic temperature. The inherent safety features of AFR-100 cores proposed were assessed using the integral reactivity parameters of the quasi-static reactivity balance analysis. The design objectives and requirements, the computation methods used as well as a description of the core concept are provided in Section 2. The three major approaches considered are introduced in Section 3 and the neutronics performances of those approaches are discussed in the same section. The orifice zoning strategies used and the steady-state thermal-hydraulic performance are provided in Section 4. The kinetics and reactivity coefficients, including the inherent safety characteristics, are provided in Section 5, and the Conclusions in Section 6. Other scenarios studied and sensitivity studies are provided in the Appendix section.« less

Compositional effects on the ignition of FACE gasolines [Compositional effects on the ignition of FACE gasoline fuels: experiments, surrogate fuel formulation, and chemical kinetic modeling

DOE PAGES

Sarathy, S. Mani; Kukkadapu, Goutham; Mehl, Marco; ...

2016-05-08

As regulatory measures for improved fuel economy and decreased emissions are pushing gasoline engine combustion technologies towards extreme conditions (i.e., boosted and intercooled intake with exhaust gas recirculation), fuel ignition characteristics become increasingly important for enabling stable operation. Here, this study explores the effects of chemical composition on the fundamental ignition behavior of gasoline fuels. Two well-characterized, high-octane, non-oxygenated FACE (Fuels for Advanced Combustion Engines) gasolines, FACE F and FACE G, having similar antiknock indices but different octane sensitivities and chemical compositions are studied. Ignition experiments were conducted in shock tubes and a rapid compression machine (RCM) at nominal pressuresmore » of 20 and 40 atm, equivalence ratios of 0.5 and 1.0, and temperatures ranging from 650 to 1270 K. Results at temperatures above 900 K indicate that ignition delay time is similar for these fuels. However, RCM measurements below 900 K demonstrate a stronger negative temperature coefficient behavior for FACE F gasoline having lower octane sensitivity. In addition, RCM pressure profiles under two-stage ignition conditions illustrate that the magnitude of low-temperature heat release (LTHR) increases with decreasing fuel octane sensitivity. However, intermediate-temperature heat release is shown to increase as fuel octane sensitivity increases. Various surrogate fuel mixtures were formulated to conduct chemical kinetic modeling, and complex multicomponent surrogate mixtures were shown to reproduce experimentally observed trends better than simpler two- and three-component mixtures composed of n-heptane, iso-octane, and toluene. Measurements in a Cooperative Fuels Research (CFR) engine demonstrated that the multicomponent surrogates accurately captured the antiknock quality of the FACE gasolines. Simulations were performed using multicomponent surrogates for FACE F and G to reveal the underlying chemical kinetics linking fuel composition with ignition characteristics. Finally, a key discovery of this work is the kinetic coupling between aromatics and naphthenes, which affects the radical pool population and thereby controls ignition.« less

Compositional effects on the ignition of FACE gasolines [Compositional effects on the ignition of FACE gasoline fuels: experiments, surrogate fuel formulation, and chemical kinetic modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarathy, S. Mani; Kukkadapu, Goutham; Mehl, Marco

As regulatory measures for improved fuel economy and decreased emissions are pushing gasoline engine combustion technologies towards extreme conditions (i.e., boosted and intercooled intake with exhaust gas recirculation), fuel ignition characteristics become increasingly important for enabling stable operation. Here, this study explores the effects of chemical composition on the fundamental ignition behavior of gasoline fuels. Two well-characterized, high-octane, non-oxygenated FACE (Fuels for Advanced Combustion Engines) gasolines, FACE F and FACE G, having similar antiknock indices but different octane sensitivities and chemical compositions are studied. Ignition experiments were conducted in shock tubes and a rapid compression machine (RCM) at nominal pressuresmore » of 20 and 40 atm, equivalence ratios of 0.5 and 1.0, and temperatures ranging from 650 to 1270 K. Results at temperatures above 900 K indicate that ignition delay time is similar for these fuels. However, RCM measurements below 900 K demonstrate a stronger negative temperature coefficient behavior for FACE F gasoline having lower octane sensitivity. In addition, RCM pressure profiles under two-stage ignition conditions illustrate that the magnitude of low-temperature heat release (LTHR) increases with decreasing fuel octane sensitivity. However, intermediate-temperature heat release is shown to increase as fuel octane sensitivity increases. Various surrogate fuel mixtures were formulated to conduct chemical kinetic modeling, and complex multicomponent surrogate mixtures were shown to reproduce experimentally observed trends better than simpler two- and three-component mixtures composed of n-heptane, iso-octane, and toluene. Measurements in a Cooperative Fuels Research (CFR) engine demonstrated that the multicomponent surrogates accurately captured the antiknock quality of the FACE gasolines. Simulations were performed using multicomponent surrogates for FACE F and G to reveal the underlying chemical kinetics linking fuel composition with ignition characteristics. Finally, a key discovery of this work is the kinetic coupling between aromatics and naphthenes, which affects the radical pool population and thereby controls ignition.« less

Numerical study of radiative heat transfer and effects of thermal boundary conditions on CLC fuel reactor

NASA Astrophysics Data System (ADS)

Ben-Mansour, R.; Li, H.; Habib, M. A.; Hossain, M. M.

2018-02-01

Global warming has become a worldwide concern due to its severe impacts and consequences on the climate system and ecosystem. As a promising technology proving good carbon capture ability with low-efficiency penalty, Chemical Looping Combustion technology has risen much interest. However, the radiative heat transfer was hardly studied, nor its effects were clearly declared. The present work provides a mathematical model for radiative heat transfer within fuel reactor of chemical looping combustion systems and conducts a numerical research on the effects of boundary conditions, solid particles reflectivity, particles size, and the operating temperature. The results indicate that radiative heat transfer has very limited impacts on the flow pattern. Meanwhile, the temperature variations in the static bed region (where solid particles are dense) brought by radiation are also insignificant. However, the effects of radiation on temperature profiles within free bed region (where solid particles are very sparse) are obvious, especially when convective-radiative (mixed) boundary condition is applied on fuel reactor walls. Smaller oxygen carrier particle size results in larger absorption & scattering coefficients. The consideration of radiative heat transfer within fuel reactor increases the temperature gradient within free bed region. On the other hand, the conversion performance of fuel is nearly not affected by radiation heat transfer within fuel reactor. However, the consideration of radiative heat transfer enhances the heat transfer between the gas phase and solid phase, especially when the operating temperature is low.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, C. S.; Zhang, Hongbin

Uncertainty quantification and sensitivity analysis are important for nuclear reactor safety design and analysis. A 2x2 fuel assembly core design was developed and simulated by the Virtual Environment for Reactor Applications, Core Simulator (VERA-CS) coupled neutronics and thermal-hydraulics code under development by the Consortium for Advanced Simulation of Light Water Reactors (CASL). An approach to uncertainty quantification and sensitivity analysis with VERA-CS was developed and a new toolkit was created to perform uncertainty quantification and sensitivity analysis with fourteen uncertain input parameters. Furthermore, the minimum departure from nucleate boiling ratio (MDNBR), maximum fuel center-line temperature, and maximum outer clad surfacemore » temperature were chosen as the selected figures of merit. Pearson, Spearman, and partial correlation coefficients were considered for all of the figures of merit in sensitivity analysis and coolant inlet temperature was consistently the most influential parameter. We used parameters as inputs to the critical heat flux calculation with the W-3 correlation were shown to be the most influential on the MDNBR, maximum fuel center-line temperature, and maximum outer clad surface temperature.« less

Uncertainty quantification and sensitivity analysis with CASL Core Simulator VERA-CS

DOE PAGES

Brown, C. S.; Zhang, Hongbin

2016-05-24

Uncertainty quantification and sensitivity analysis are important for nuclear reactor safety design and analysis. A 2x2 fuel assembly core design was developed and simulated by the Virtual Environment for Reactor Applications, Core Simulator (VERA-CS) coupled neutronics and thermal-hydraulics code under development by the Consortium for Advanced Simulation of Light Water Reactors (CASL). An approach to uncertainty quantification and sensitivity analysis with VERA-CS was developed and a new toolkit was created to perform uncertainty quantification and sensitivity analysis with fourteen uncertain input parameters. Furthermore, the minimum departure from nucleate boiling ratio (MDNBR), maximum fuel center-line temperature, and maximum outer clad surfacemore » temperature were chosen as the selected figures of merit. Pearson, Spearman, and partial correlation coefficients were considered for all of the figures of merit in sensitivity analysis and coolant inlet temperature was consistently the most influential parameter. We used parameters as inputs to the critical heat flux calculation with the W-3 correlation were shown to be the most influential on the MDNBR, maximum fuel center-line temperature, and maximum outer clad surface temperature.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szybist, James P.; Splitter, Derek A.

The octane sensitivity (S), defined as the difference between the Research Octane Number (RON) and the Motor Octane Number (MON), is of increasing interest in spark ignition (SI) engines because of its relevance to knock resistance at boosted high load conditions. In this study, three fuels with nearly constant RON (99.2-100) and varying S (S = 0, 6.5, and 12) are operated at the knock limited spark advance (KLSA) at nominal engine loads of 10, 15, and 20 bar IMEP in a single cylinder SI engine with side-mount direct injection fueling, at λ =1 stoichiometry. At each load condition, themore » intake manifold temperature is swept from 35 °C to 95 °C to alter the temperature and pressure history of the charge. Results show that at the 10 bar IMEP condition, knock resistance is inversely proportional to fuel S where the S=0 fuel is the most knock resist, but as load increases the trend reverses and knock resistance becomes proportional to fuel S, and the S=12 fuel is the most knock resistant. The reversal of knock resistance as a function of S with load it is attributed to changing fuel ignition delay, as bulk gas intermediate temperature heat release (ITHR) is observed for the S = 0 several crank angles prior to the spark command and ITHR magnitude is a function of increasing intake temperature. As intake temperature continued to increase, the S=0 fuel transitioned from ITHR to low-temperature heat release (LTHR) prior to the spark event. At the highest load and intake temperature, 95 C, the S=0 fuel exhibits distinct LTHR and negative temperature coefficient (NTC), and the intermediate S value fuel (S=6.5) exhibited distinct ITHR behavior several crank angles prior to the spark command. However, for the tested conditions, the S=12 fuel exhibits neither ITHR nor LTHR. To understand the measured trends, chemical kinetic modeling is used to elucidate the fuel specific dependencies on in-cylinder temperature and pressure history. Lastly, the bulk gas composition change that occurs for fuels and conditions exhibiting ITHR and LTHR is analyzed in the modeling, including their implications on flame speed and combustion stability at late phasing. Furthermore, the combined findings illustrate the commonality and utility of fuel S, ITHR, LTHR, and NTC across a wide range of conditions, and the associated implications of fuel S in highly boosted modern GDI SI engines relative to the RON and MON tests.« less

Square lattice honeycomb reactor for space power and propulsion

NASA Astrophysics Data System (ADS)

Gouw, Reza; Anghaie, Samim

2000-01-01

The most recent nuclear design study at the Innovative Nuclear Space Power and Propulsion Institute (INSPI) is the Moderated Square-Lattice Honeycomb (M-SLHC) reactor design utilizing the solid solution of ternary carbide fuels. The reactor is fueled with solid solution of 93% enriched (U,Zr,Nb)C. The square-lattice honeycomb design provides high strength and is amenable to the processing complexities of these ultrahigh temperature fuels. The optimum core configuration requires a balance between high specific impulse and thrust level performance, and maintaining the temperature and strength limits of the fuel. The M-SLHC design is based on a cylindrical core that has critical radius and length of 37 cm and 50 cm, respectively. This design utilized zirconium hydrate to act as moderator. The fuel sub-assemblies are designed as cylindrical tubes with 12 cm in diameter and 10 cm in length. Five fuel subassemblies are stacked up axially to form one complete fuel assembly. These fuel assemblies are then arranged in the circular arrangement to form two fuel regions. The first fuel region consists of six fuel assemblies, and 18 fuel assemblies for the second fuel region. A 10-cm radial beryllium reflector in addition to 10-cm top axial beryllium reflector is used to reduce neutron leakage from the system. To perform nuclear design analysis of the M-SLHC design, a series of neutron transport and diffusion codes are used. To optimize the system design, five axial regions are specified. In each axial region, temperature and fuel density are varied. The axial and radial power distributions for the system are calculated, as well as the axial and radial flux distributions. Temperature coefficients of the system are also calculated. A water submersion accident scenario is also analyzed for these systems. Results of the nuclear design analysis indicate that a compact core can be designed based on ternary uranium carbide square-lattice honeycomb fuel, which provides a relatively high thrust to weight ratio. .

Bio-energy generation in an affordable, single-chamber microbial fuel cell integrated with adsorption hybrid system: effects of temperature and comparison study.

PubMed

Tee, Pei-Fang; Abdullah, Mohammad Omar; Tan, Ivy A W; Amin, Mohamed A M; Nolasco-Hipolito, Cirilo; Bujang, Kopli

2018-04-01

A microbial fuel cell (MFC) integrated with adsorption system (MFC-AHS) is tested under various operating temperatures with palm oil mill effluent as the substrate. The optimum operating temperature for such system is found to be at ∼35°C with current, power density, internal resistance (R in ), Coulombic efficiency (CE) and maximum chemical oxygen demand (COD) removal of 2.51 ± 0.2 mA, 74 ± 6 mW m -3 , 25.4 Ω, 10.65 ± 0.5% and 93.57 ± 1.2%, respectively. Maximum current density increases linearly with temperature at a rate of 0.1772 mA m -2  °C -1 , whereas maximum power density was in a polynomial function. The temperature coefficient (Q 10 ) is found to be 1.20 between 15°C and 35°C. Present studies have demonstrated better CE performance when compared to other MFC-AHSs. Generally, MFC-AHS has demonstrated higher COD removals when compared to standalone MFC regardless of operating temperatures. ACFF: activated carbon fiber felt; APHA: American Public Health Association; CE: Coulombic efficiency; COD: chemical oxygen demand; ECG: electrocardiogram; GAC: granular activated carbon; GFB: graphite fiber brush; MFC: microbial fuel cell; MFC-AHS: microbial fuel cell integrated with adsorption hybrid system; MFC-GG: microbial fuel cell integrated with graphite granules; POME: palm oil mill effluent; PTFE: polytetrafluoroethylene; SEM: scanning electron microscope.

THE FUEL ELEMENT GRAPHITE. Project DRAGON.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, L.W.; Price, M.S.T.

1963-01-15

The main requirements of a fuel element graphite for reactors based on the Dragon concept are low transmission coefficient for fission products, dimensional stability under service conditions, high strength, high thermal conductivity, high purity, and high resistance to oxidation. Since conclusions reached in early 1960, a considerable amount of information has accumulated concerning the likely behaviour of graphites in high temperature reactor systems, particularly data on dimensional stability under irradiation. The influence of this new knowledge on the development of fuel element graphite with the Dragon Project is discussed in detail in the final section of this paper.

An experimental and modeling study investigating the ignition delay in a military diesel engine running hexadecane (cetane) fuel

DOE PAGES

Cowart, Jim S.; Fischer, Warren P.; Hamilton, Leonard J.; ...

2013-02-01

In an effort aimed at predicting the combustion behavior of a new fuel in a conventional diesel engine, cetane (n-hexadecane) fuel was used in a military engine across the entire speed–load operating range. The ignition delay was characterized for this fuel at each operating condition. A chemical ignition delay was also predicted across the speed–load range using a detailed chemical kinetic mechanism with a constant pressure reactor model. At each operating condition, the measured in-cylinder pressure and predicted temperature at the start of injection were applied to the detailed n-hexadecane kinetic mechanism, and the chemical ignition delay was predicted withoutmore » any kinetic mechanism calibration. The modeling results show that fuel–air parcels developed from the diesel spray with an equivalence ratio of 4 are the first to ignite. The chemical ignition delay results also showed decreasing igntion delays with increasing engine load and speed, just as the experimental data revealed. At lower engine speeds and loads, the kinetic modeling results show the characteristic two-stage negative temperature coefficient behavior of hydrocarbon fuels. However, at high engine speeds and loads, the reactions do not display negative temperature coefficient behavior, as the reactions proceed directly into high-temperature pathways due to higher temperatures and pressure at injection. A moderate difference between the total and chemical ignition delays was then characterized as a phyical delay period that scales inversely with engine speed. This physical delay time is representative of the diesel spray development time and is seen to become a minority fraction of the total igntion delay at higher engine speeds. In addition, the approach used in this study suggests that the ignition delay and thus start of combustion may be predicted with reasonable accuracy using kinetic modeling to determine the chemical igntion delay. Then, in conjunction with the physical delay time (experimental or modeling based), a new fuel’s acceptability in a conventional engine could be assessed by determining that the total ignition delay is not too short or too long.« less

Mathematical Storage-Battery Models

NASA Technical Reports Server (NTRS)

Chapman, C. P.; Aston, M.

1985-01-01

Empirical formula represents performance of electrical storage batteries. Formula covers many battery types and includes numerous coefficients adjusted to fit peculiarities of each type. Battery and load parameters taken into account include power density in battery, discharge time, and electrolyte temperature. Applications include electric-vehicle "fuel" gages and powerline load leveling.

Demonstration of optimum fuel-to-moderator ratio in a PWR unit fuel cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feltus, M.A.; Pozsgai, C.

1992-01-01

Nuclear engineering students at The Pennsylvania State University develop scaled-down [[approx]350 MW(thermal)] pressurized water reactors (PWRs) using actual plants as references. The design criteria include maintaining the clad temperature below 2200[degree]F, fuel temperature below melting point, sufficient departure from nucleate boiling ratio (DNBR) margin, a beginning-of-life boron concentration that yields a negative moderator temperature coefficient, an adequate cycle power production (330 effective full-power days), and a batch loading scheme that is economical. The design project allows for many degrees of freedom (e.g., assembly number, pitch and height and batch enrichments) so that each student's result is unique. The iterative naturemore » of the design process is stressed in the course. The LEOPARD code is used for the unit cell depletion, critical boron, and equilibrium xenon calculations. Radial two-group diffusion equations are solved with the TWIDDLE-DEE code. The steady-state ZEBRA thermal-hydraulics program is used for calculating DNBR. The unit fuel cell pin radius and pitch (fuel-to-moerator ratio) for the scaled-down design, however, was set equal to the already optimized ratio for the reference PWR. This paper describes an honors project that shows how the optimum fuel-to-moderator ratio is found for a unit fuel cell shown in terms of neutron economics. This exercise illustrates the impact of fuel-to-moderator variations on fuel utilization factor and the effect of assuming space and energy separability.« less

Development and applications of methodologies for the neutronic design of the Pebble Bed Advanced High Temperature Reactor (PB-AHTR)

NASA Astrophysics Data System (ADS)

Fratoni, Massimiliano

This study investigated the neutronic characteristics of the Pebble Bed Advanced High Temperature Reactor (PB-AHTR), a novel nuclear reactor concept that combines liquid salt (7LiF-BeF2---flibe) cooling and TRISO coated-particle fuel technology. The use of flibe enables operation at high power density and atmospheric pressure and improves passive decay-heat removal capabilities, but flibe, unlike conventional helium coolant, is not transparent to neutrons. The flibe occupies 40% of the PB-AHTR core volume and absorbs ˜8% of the neutrons, but also acts as an effective neutron moderator. Two novel methodologies were developed for calculating the time dependent and equilibrium core composition: (1) a simplified single pebble model that is relatively fast; (2) a full 3D core model that is accurate and flexible but computationally intensive. A parametric analysis was performed spanning a wide range of fuel kernel diameters and graphite-to-heavy metal atom ratios to determine the attainable burnup and reactivity coefficients. Using 10% enriched uranium ˜130 GWd/tHM burnup was found to be attainable, when the graphite-to-heavy metal atom ratio (C/HM) is in the range of 300 to 400. At this or smaller C/HM ratio all reactivity coefficients examined---coolant temperature, coolant small and full void, fuel temperature, and moderator temperature, were found to be negative. The PB-AHTR performance was compared to that of alternative options for HTRs, including the helium-cooled pebble-bed reactor and prismatic fuel reactors, both gas-cooled and flibe-cooled. The attainable burnup of all designs was found to be similar. The PB-AHTR generates at least 30% more energy per pebble than the He-cooled pebble-bed reactor. Compared to LWRs the PB-AHTR requires 30% less natural uranium and 20% less separative work per unit of electricity generated. For deep burn TRU fuel made from recycled LWR spent fuel, it was found that in a single pass through the core ˜66% of the TRU can be transmuted; this burnup is slightly superior to that attainable in helium-cooled reactors. A preliminary analysis of the modular variant for the PB-AHTR investigated the triple heterogeneity of this design and determined its performance characteristics.

Fabrication and thermophysical property characterization of UN/U 3Si 2 composite fuel forms

DOE PAGES

White, Joshua Taylor; Travis, Austin William; Dunwoody, John Tyler; ...

2017-09-21

High uranium density composite fuels composed of UN and U 3Si 2 have been fabricated using a liquid phase sintering route at temperatures between 1873 K and 1973 K and spanning compositions of 10 vol% to 40 vol% U 3Si 2. Microstructural analysis and phase characterization revealed the formation of an U-Si-N phase of unknown structure. Microcracking was observed in the U-Si portion of the composite microstructure that likely originates from the mismatched coefficient of thermal expansion between the UN and U 3Si 2 leading to stresses on heating and cooling of the composite. Thermal expansion coefficient, thermal diffusivity, andmore » thermal conductivity were characterized for each of the compositions as a function of temperature to 1673 K. Hysteresis is observed in the thermal diffusivity for the 20 vol% through 40 vol% specimens between room temperature and 1273 K, which is attributed to the microcracking in the U-Si phase. Thermal conductivity of the composites was modeled using the MOOSE framework based on the collected microstructure data. In conclusion, the impact of irradiation on thermal conductivity was also simulated for this class of composite materials.« less

Fabrication and thermophysical property characterization of UN/U 3Si 2 composite fuel forms

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, Joshua Taylor; Travis, Austin William; Dunwoody, John Tyler

High uranium density composite fuels composed of UN and U 3Si 2 have been fabricated using a liquid phase sintering route at temperatures between 1873 K and 1973 K and spanning compositions of 10 vol% to 40 vol% U 3Si 2. Microstructural analysis and phase characterization revealed the formation of an U-Si-N phase of unknown structure. Microcracking was observed in the U-Si portion of the composite microstructure that likely originates from the mismatched coefficient of thermal expansion between the UN and U 3Si 2 leading to stresses on heating and cooling of the composite. Thermal expansion coefficient, thermal diffusivity, andmore » thermal conductivity were characterized for each of the compositions as a function of temperature to 1673 K. Hysteresis is observed in the thermal diffusivity for the 20 vol% through 40 vol% specimens between room temperature and 1273 K, which is attributed to the microcracking in the U-Si phase. Thermal conductivity of the composites was modeled using the MOOSE framework based on the collected microstructure data. In conclusion, the impact of irradiation on thermal conductivity was also simulated for this class of composite materials.« less

An Aurivillius Oxide Based Cathode with Excellent CO2 Tolerance for Intermediate-Temperature Solid Oxide Fuel Cells.

PubMed

Zhu, Yinlong; Zhou, Wei; Chen, Yubo; Shao, Zongping

2016-07-25

The Aurivillius oxide Bi2 Sr2 Nb2 MnO12-δ (BSNM) was used as a cobalt-free cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). To the best of our knowledge, the BSNM oxide is the only alkaline-earth-containing cathode material with complete CO2 tolerance that has been reported thus far. BSNM not only shows favorable activity in the oxygen reduction reaction (ORR) at intermediate temperatures but also exhibits a low thermal expansion coefficient, excellent structural stability, and good chemical compatibility with the electrolyte. These features highlight the potential of the new BSNM material as a highly promising cathode material for IT-SOFCs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactor physics behavior of transuranic-bearing TRISO-particle fuel in a pressurized water reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pope, M. A.; Sen, R. S.; Ougouag, A. M.

2012-07-01

Calculations have been performed to assess the neutronic behavior of pins of Fully-Ceramic Micro-encapsulated (FCM) fuel in otherwise-conventional Pressurized Water Reactor (PWR) fuel pins. The FCM fuel contains transuranic (TRU) - only oxide fuel in tri-isotropic (TRISO) particles with the TRU loading coming from the spent fuel of a conventional LWR after 5 years of cooling. Use of the TRISO particle fuel would provide an additional barrier to fission product release in the event of cladding failure. Depletion calculations were performed to evaluate reactivity-limited burnup of the TRU-only FCM fuel. These calculations showed that due to relatively little space availablemore » for fuel, the achievable burnup with these pins alone is quite small. Various reactivity parameters were also evaluated at each burnup step including moderator temperature coefficient (MTC), Doppler, and soluble boron worth. These were compared to reference UO{sub 2} and MOX unit cells. The TRU-only FCM fuel exhibits degraded MTC and Doppler coefficients relative to UO{sub 2} and MOX. Also, the reactivity effects of coolant voiding suggest that the behavior of this fuel would be similar to a MOX fuel of very high plutonium fraction, which are known to have positive void reactivity. In general, loading of TRU-only FCM fuel into an assembly without significant quantities of uranium presents challenges to the reactor design. However, if such FCM fuel pins are included in a heterogeneous assembly alongside LEU fuel pins, the overall reactivity behavior would be dominated by the uranium pins while attractive TRU destruction performance levels in the TRU-only FCM fuel pins is retained. From this work, it is concluded that use of heterogeneous assemblies such as these appears feasible from a preliminary reactor physics standpoint. (authors)« less

Reactor Physics Behavior of Transuranic-Bearing TRISO-Particle Fuel in a Pressurized Water Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael A. Pope; R. Sonat Sen; Abderrafi M. Ougouag

2012-04-01

Calculations have been performed to assess the neutronic behavior of pins of Fully-Ceramic Micro-encapsulated (FCM) fuel in otherwise-conventional Pressurized Water Reactor (PWR) fuel pins. The FCM fuel contains transuranic (TRU)-only oxide fuel in tri-isotropic (TRISO) particles with the TRU loading coming from the spent fuel of a conventional LWR after 5 years of cooling. Use of the TRISO particle fuel would provide an additional barrier to fission product release in the event of cladding failure. Depletion calculations were performed to evaluate reactivity-limited burnup of the TRU-only FCM fuel. These calculations showed that due to relatively little space available for fuel,more » the achievable burnup with these pins alone is quite small. Various reactivity parameters were also evaluated at each burnup step including moderator temperature coefficient (MTC), Doppler, and soluble boron worth. These were compared to reference UO{sub 2} and MOX unit cells. The TRU-only FCM fuel exhibits degraded MTC and Doppler coefficients relative to UO{sub 2} and MOX. Also, the reactivity effects of coolant voiding suggest that the behavior of this fuel would be similar to a MOX fuel of very high plutonium fraction, which are known to have positive void reactivity. In general, loading of TRU-only FCM fuel into an assembly without significant quantities of uranium presents challenges to the reactor design. However, if such FCM fuel pins are included in a heterogeneous assembly alongside LEU fuel pins, the overall reactivity behavior would be dominated by the uranium pins while attractive TRU destruction performance levels in the TRU-only FCM fuel pins is. From this work, it is concluded that use of heterogeneous assemblies such as these appears feasible from a preliminary reactor physics standpoint.« less

Sensitivity Analysis of Fuel Centerline Temperatures in SuperCritical Water-cooled Reactors (SCWRs)

NASA Astrophysics Data System (ADS)

Abdalla, Ayman

SuperCritical Water-cooled Reactors (SCWRs) are one of the six nuclear-reactor concepts currently being developed under the Generation-IV International Forum (GIF). A main advantage of SCW Nuclear Power Plants (NPPs) is that they offer higher thermal efficiencies compared to those of current conventional NPPs. Unlike today's conventional NPPs, which have thermal efficiencies between 30 - 35%, SCW NPPs will have thermal efficiencies within a range of 45 - 50%, owing to high operating temperatures and pressures (i.e., coolant temperatures as high as 625°C at 25 MPa pressure). The use of current fuel bundles with UO2 fuel at the high operating parameters of SCWRs may cause high fuel centerline temperatures, which could lead to fuel failure and fission gas release. Studies have shown that when the Variant-20 (43-element) fuel bundle was examined at SCW conditions, the fuel centerline temperature industry limit of 1850°C for UO2 and the sheath temperature design limit of 850°C might be exceeded. Therefore, new fuel-bundle designs, which comply with the design requirements, are required for future use in SCWRs. The main objective of this study to conduct a sensitivity analysis in order to identify the main factors that leads to fuel centerline temperature reduction. Therefore, a 54-element fuel bundle with smaller diameter of fuel elements compared to that of the 43-element bundle was designed and various nuclear fuels are examined for future use in a generic Pressure Tube (PT) SCWR. The 54-element bundle consists of 53 heated fuel elements with an outer diameter of 9.5 mm and one central unheated element of 20-mm outer diameter which contains burnable poison. The 54-element fuel bundle has an outer diameter of 103.45 mm, which is the same as the outer diameter of the 43-element fuel bundle. After developing the 54-element fuel bundle, one-dimensional heat-transfer analysis was conducted using MATLAB and NIST REFPROP programs. As a result, the Heat Transfer Coefficient (HTC), bulk-fluid, sheath and fuel centerline temperature profiles were generated along the heated length of 5.772 m for a generic fuel channel. The fuel centerline and sheath temperature profiles have been determined at four Axial Heat Flux Profiles (AHFPs) using an average thermal power per channel of 8.5 MWth. The four examined AHFPs are the uniform, cosine, upstream-skewed and downstream-skewed profiles. Additionally, this study focuses on investigating a possibility of using low, enhanced and high thermal-conductivity fuels. The low thermal-conductivity fuels, which have been examined in this study, are uranium dioxide (UO 2), Mixed Oxide (MOX) and Thoria (ThO2) fuels. The examined enhanced thermal-conductivity fuels are uranium dioxide - silicon carbide (UO2 - SiC) and uranium dioxide - beryllium oxide (UO2 - BeO). Lastly, uranium carbide (UC), uranium dicarbide (UC2) and uranium nitride (UN) are the selected high thermal-conductivity fuels, which have been proposed for use in SCWRs. A comparison has been made between the low, enhanced and high thermal-conductivity fuels in order to identify the fuel centerline temperature behaviour when different nuclear fuels are used. Also, in the process of conducting the sensitivity analysis, the HTC was calculated using the Mokry et al. correlation, which is the most accurate supercritical water heat-transfer correlation so far. The sheath and the fuel centerline temperature profiles were determined for two cases. In Case 1, the HTC was calculated based on the Mokry et al. correlation, while in Case 2, the HTC values calculated for Case 1 were multiplied by a factor of 2. This factor was used in order to identify the amount of decrease in temperatures if the heat transfer is enhanced with appendages. Results of this analysis indicate that the use of the newly developed 54-element fuel bundle along with the proposed fuels is promising when compared with the Variant-20 (43-element) fuel bundle. Overall, the fuel centerline and sheath temperatures were below the industry and design limits when most of the proposed fuels were examined in the 54-element fuel bundle, however, the fuel centerline temperature limit was exceeded while MOX fuel was examined. Keywords: SCWRs, Fuel Centerline Temperature, Sheath Temperature, High Thermal Conductivity Fuels, Low Thermal Conductivity Fuels, HTC.

Characterization of microstructural, mechanical and thermophysical properties of Th-52U alloy

NASA Astrophysics Data System (ADS)

Das, Santanu; Kaity, S.; Kumar, R.; Banerjee, J.; Roy, S. B.; Chaudhari, G. P.; Daniel, B. S. S.

2016-11-01

Th-52 wt.% U alloy has a microstructure featuring interspersed networks of uranium rich and thorium rich phases. Room temperature hardness of the alloy is more than twice that of unalloyed thorium. The alloy age hardens (550 °C) only slightly (peak hardness/hardness of solution heated and quenched = 1.05). Room temperature thermal conductivity (25.6 W m-1 °C-1) is close to that of uranium and most of the binary and ternary metallic alloy fuel materials. Average linear coefficient of thermal expansion (CTE) of Th-52 wt.% U alloy [11.2 × 10-06 °C-1 (27-290 °C) and 16.75 × 10-06 °C-1 (27-600 °C)] are comparable with that of many metallic alloy fuel candidates. Th-52 wt.% U alloy with non-age hardenable microstructure, appreciable thermal conductivity, moderate thermal expansion may find metallic fuel applications in nuclear reactors.

Sensitivity analysis of FeCrAl cladding and U3Si2 fuel under accident conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamble, Kyle Allan Lawrence; Hales, Jason Dean

2016-08-01

The purpose of this milestone report is to highlight the results of sensitivity analyses performed on two accident tol- erant fuel concepts: U3Si2 fuel and FeCrAl cladding. The BISON fuel performance code under development at Idaho National Laboratory was coupled to Sandia National Laboratories’ DAKOTA software to perform the sensitivity analyses. Both Loss of Coolant (LOCA) and Station blackout (SBO) scenarios were analyzed using main effects studies. The results indicate that for FeCrAl cladding the input parameters with greatest influence on the output metrics of interest (fuel centerline temperature and cladding hoop strain) during the LOCA were the isotropic swellingmore » and fuel enrichment. For U3Si2 the important inputs were found to be the intergranular diffusion coefficient, specific heat, and fuel thermal conductivity. For the SBO scenario, Young’s modulus was found to be influential in FeCrAl in addition to the isotropic swelling and fuel enrichment. Contrarily to the LOCA case, the specific heat of U3Si2 was found to have no effect during the SBO. The intergranular diffusion coefficient and fuel thermal conductivity were still found to be of importance. The results of the sensitivity analyses have identified areas where further research is required including fission gas behavior in U3Si2 and irradiation swelling in FeCrAl. Moreover, the results highlight the need to perform the sensitivity analyses on full length fuel rods for SBO scenarios.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konyashov, Vadim V.; Krasnov, Alexander M.

Results are provided of the experimental investigation of radioactive fission product (RFP) release, i.e., krypton, xenon, and iodine radionuclides from fuel elements with initial defects during long-term (3 to 5 yr) irradiation under low linear power (5 to 12 kW/m) and during special experiments in the VK-50 vessel-type boiling water reactor.The calculation model for the RFP release from the fuel-to-cladding gap of the defective fuel element into coolant was developed. It takes into account the convective transport in the fuel-to-cladding gap and RFP sorption on the internal cladding surface and is in good agreement with the available experimental data. Anmore » approximate analytical solution of the transport equation is given. The calculation dependencies of the RFP release coefficients on the main parameters such as defect size, fuel-to-cladding gap, temperature of the internal cladding surface, and radioactive decay constant were analyzed.It is shown that the change of the RFP release from the fuel elements with the initial defects during long-term irradiation is, mainly, caused by fuel swelling followed by reduction of the fuel-to-cladding gap and the fuel temperature. The calculation model for the RFP release from defective fuel elements applicable to light water reactors (LWRs) was developed. It takes into account the change of the defective fuel element parameters during long-term irradiation. The calculation error according to the program does not exceed 30% over all the linear power change range of the LWR fuel elements (from 5 to 26 kW/m)« less

PROPULSION AND POWER RAPID RESPONSE RESEARCH AND DEVELOPMENT (R&D) SUPPORT. Deliver Order 0002: Power-Dense, Solid Oxide Fuel Cell Systems: High-Performance, High-Power-Density Solid Oxide Fuel Cells - Materials and Load Control

DTIC Science & Technology

2010-04-01

aluminum titanate has evolved from a coefficient of thermal expansion (CTE) lowering additive in traditional nickel/YSZ cermets to an anchoring...provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently...volumetric concentrations well below percolation for traditional cermets . The coarsening of nickel after high temperature thermal treatment poses

Study of method for reducing fuel consumption and amount of specific emissions of harmful substances with exhaust gases of passenger cars when using “climate control” system

NASA Astrophysics Data System (ADS)

Burakova, L. N.; Anisimov, I. A.; Burakova, A. D.; Burakova, O. D.

2018-05-01

The article deals with the issue of improving fuel efficiency and the ecological nature of passenger cars, servicing the administrative and management personnel of the oil and gas complex. It is established that fuel consumption and the amount of specific emissions of harmful substances with exhaust gases of cars when using the “climate control” system depend on the effective ambient temperature, the color of the opaque car body elements, the power of the car engine and the interior volume. However, the simplest controlled factor is the color of the opaque car body elements, which is characterized by the coefficient of light reflection. In the course of experimental studies, the authors established the dependences of a change in fuel consumption and a share of reducing emissions of harmful substances with exhaust gases of passenger cars with the “climate control” system on the coefficient of light reflection. A method has been developed to reduce fuel consumption and the amount of specific emissions of harmful substances with the exhaust gases of passenger cars using the “climate control” system, which involves painting the vehicle roof white and allows reducing fuel consumption by 5.5-10.3%, and the amount of specific emissions of harmful substances by 0.8-2.3%.

Study of a method for reducing fuel consumption and the amount of specific emissions of harmful substances with exhaust gases of passenger cars when using the “climate control” system

NASA Astrophysics Data System (ADS)

Burakova, L. N.; Anisimov, I. A.; Burakova, A. D.; Burakova, O. D.

2018-05-01

The article deals with the issue of improving the fuel economy and environmental friendliness of motor vehicles which serve the administrative and management personnel of the oil and gas industry. It is established that fuel consumption and the amount of specific emissions of harmful substances with exhaust gases of cars when using the “climate control” system depend on the effective ambient temperature, the color of the opaque car body elements, the power of the car engine and the interior volume. However, the simplest controlled factor is the color of the opaque car body elements, which is characterized by the coefficient of light reflection. In the course of experimental studies, we established the dependences of a change in fuel consumption and a share of reducing emissions of harmful substances with exhaust gases of passenger cars with the “climate control” system on the coefficient of light reflection. A method has been developed to reduce fuel consumption and the amount of specific emissions of harmful substances with the exhaust gases of passenger cars using the “climate control” system, which involves painting the vehicle roof white and allows reducing fuel consumption by 5.5-10.3%, and the amount of specific emissions of harmful substances by 0.8-2.3%.

Gap Size Uncertainty Quantification in Advanced Gas Reactor TRISO Fuel Irradiation Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pham, Binh T.; Einerson, Jeffrey J.; Hawkes, Grant L.

The Advanced Gas Reactor (AGR)-3/4 experiment is the combination of the third and fourth tests conducted within the tristructural isotropic fuel development and qualification research program. The AGR-3/4 test consists of twelve independent capsules containing a fuel stack in the center surrounded by three graphite cylinders and shrouded by a stainless steel shell. This capsule design enables temperature control of both the fuel and the graphite rings by varying the neon/helium gas mixture flowing through the four resulting gaps. Knowledge of fuel and graphite temperatures is crucial for establishing the functional relationship between fission product release and irradiation thermal conditions.more » These temperatures are predicted for each capsule using the commercial finite-element heat transfer code ABAQUS. Uncertainty quantification reveals that the gap size uncertainties are among the dominant factors contributing to predicted temperature uncertainty due to high input sensitivity and uncertainty. Gap size uncertainty originates from the fact that all gap sizes vary with time due to dimensional changes of the fuel compacts and three graphite rings caused by extended exposure to high temperatures and fast neutron irradiation. Gap sizes are estimated using as-fabricated dimensional measurements at the start of irradiation and post irradiation examination dimensional measurements at the end of irradiation. Uncertainties in these measurements provide a basis for quantifying gap size uncertainty. However, lack of gap size measurements during irradiation and lack of knowledge about the dimension change rates lead to gap size modeling assumptions, which could increase gap size uncertainty. In addition, the dimensional measurements are performed at room temperature, and must be corrected to account for thermal expansion of the materials at high irradiation temperatures. Uncertainty in the thermal expansion coefficients for the graphite materials used in the AGR-3/4 capsules also increases gap size uncertainty. This study focuses on analysis of modeling assumptions and uncertainty sources to evaluate their impacts on the gap size uncertainty.« less

Computed tomography measurement of gaseous fuel concentration by infrared laser light absorption

NASA Astrophysics Data System (ADS)

Kawazoe, Hiromitsu; Inagaki, Kazuhisa; Emi, Y.; Yoshino, Fumio

1997-11-01

A system to measure gaseous hydrocarbon distributions was devised, which is based on IR light absorption by C-H stretch mode of vibration and computed tomography method. It is called IR-CT method in the paper. Affection of laser light power fluctuation was diminished by monitoring source light intensity by the second IR light detector. Calibration test for methane fuel was carried out to convert spatial data of line absorption coefficient into quantitative methane concentration. This system was applied to three flow fields. The first is methane flow with lifted flame which is generated by a gourd-shaped fuel nozzle. Feasibility of the IR-CT method was confirmed through the measurement. The second application is combustion field with diffusion flame. Calibration to determine absorptivity was undertaken, and measured line absorption coefficient was converted spatial fuel concentration using corresponding temperature data. The last case is modeled in cylinder gas flow of internal combustion engine, where gaseous methane was led to the intake valve in steady flow state. The fuel gas flow simulates behavior of gaseous gasoline which is evaporated at intake valve tulip. Computed tomography measurement of inner flow is essentially difficult because of existence of surrounding wall. In this experiment, IR laser beam was led to planed portion by IR light fiber. It is found that fuel convection by airflow takes great part in air-fuel mixture formation and the developed IR-CT system to measure fuel concentration is useful to analyze air-fuel mixture formation process and to develop new combustors.

Neutronics calculations on the impact of burnable poisons to safety and non-proliferation aspects of inert matrix fuel

NASA Astrophysics Data System (ADS)

Pistner, C.; Liebert, W.; Fujara, F.

2006-06-01

Inert matrix fuels (IMF) with plutonium may play a significant role to dispose of stockpiles of separated plutonium from military or civilian origin. For reasons of reactivity control of such fuels, burnable poisons (BP) will have to be used. The impact of different possible BP candidates (B, Eu, Er and Gd) on the achievable burnup as well as on safety and non-proliferation aspects of IMF are analyzed. To this end, cell burnup calculations have been performed and burnup dependent reactivity coefficients (boron worth, fuel temperature and moderator void coefficient) were calculated. All BP candidates were analyzed for one initial BP concentration and a range of different initial plutonium-concentrations (0.4-1.0 g cm-3) for reactor-grade plutonium isotopic composition as well as for weapon-grade plutonium. For the two most promising BP candidates (Er and Gd), a range of different BP concentrations was investigated to study the impact of BP concentration on fuel burnup. A set of reference fuels was identified to compare the performance of uranium-fuels, MOX and IMF with respect to (1) the fraction of initial plutonium being burned, (2) the remaining absolute plutonium concentration in the spent fuel and (3) the shift in the isotopic composition of the remaining plutonium leading to differences in the heat and neutron rate produced. In the case of IMF, the remaining Pu in spent fuel is unattractive for a would be proliferator. This underlines the attractiveness of an IMF approach for disposal of Pu from a non-proliferation perspective.

An assessment on convective and radiative heat transfer modelling in tubular solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Sánchez, D.; Muñoz, A.; Sánchez, T.

Four models of convective and radiative heat transfer inside tubular solid oxide fuel cells are presented in this paper, all of them applicable to multidimensional simulations. The work is aimed at assessing if it is necessary to use a very detailed and complicated model to simulate heat transfer inside this kind of device and, for those cases when simple models can be used, the errors are estimated and compared to those of the more complex models. For the convective heat transfer, two models are presented. One of them accounts for the variation of film coefficient as a function of local temperature and composition. This model gives a local value for the heat transfer coefficients and establishes the thermal entry length. The second model employs an average value of the transfer coefficient, which is applied to the whole length of the duct being studied. It is concluded that, unless there is a need to calculate local temperatures, a simple model can be used to evaluate the global performance of the cell with satisfactory accuracy. For the radiation heat transfer, two models are presented again. One of them considers radial radiation exclusively and, thus, radiative exchange between adjacent cells is neglected. On the other hand, the second model accounts for radiation in all directions but increases substantially the complexity of the problem. For this case, it is concluded that deviations between both models are higher than for convection. Actually, using a simple model can lead to a not negligible underestimation of the temperature of the cell.

Thermal analysis of regenerative-cooled pylon in multi-mode rocket based combined cycle engine

NASA Astrophysics Data System (ADS)

Yan, Dekun; He, Guoqiang; Li, Wenqiang; Zhang, Duo; Qin, Fei

2018-07-01

Combining pylon injector with rocket is an effective method to achieve efficient mixing and combustion in the RBCC engine. This study designs a fuel pylon with active cooling structure, and numerically investigates the coupled heat transfer between active cooling process in the pylon and combustion in the combustor in different modes. Effect of the chemical reaction of the fuel on the flow, heat transfer and physical characteristics is also discussed. The numerical results present a good agreement with the experimental data. Results indicate that drastic supplementary combustion caused by rocket gas and secondary combustion caused by the fuel injection from the pylon result in severe thermal load on the pylon. Although regenerative cooling without cracking can reduce pylon's temperature below the allowable limit, a high-temperature area appears in the middle and nail section of the pylon due to the coolant's insufficient convective heat transfer coefficient. Comparatively, endothermic cracking can provide extra chemical heat sink for the coolant and low velocity contributes to prolong the reaction time to increase the heat absorption from chemical reaction, which further lowers and unifies the pylon surface temperature.

Uncertainty Analysis on Heat Transfer Correlations for RP-1 Fuel in Copper Tubing

NASA Technical Reports Server (NTRS)

Driscoll, E. A.; Landrum, D. B.

2004-01-01

NASA is studying kerosene (RP-1) for application in Next Generation Launch Technology (NGLT). Accurate heat transfer correlations in narrow passages at high temperatures and pressures are needed. Hydrocarbon fuels, such as RP-1, produce carbon deposition (coke) along the inside of tube walls when heated to high temperatures. A series of tests to measure the heat transfer using RP-1 fuel and examine the coking were performed in NASA Glenn Research Center's Heated Tube Facility. The facility models regenerative cooling by flowing room temperature RP-1 through resistively heated copper tubing. A Regression analysis is performed on the data to determine the heat transfer correlation for Nusselt number as a function of Reynolds and Prandtl numbers. Each measurement and calculation is analyzed to identify sources of uncertainty, including RP-1 property variations. Monte Carlo simulation is used to determine how each uncertainty source propagates through the regression and an overall uncertainty in predicted heat transfer coefficient. The implications of these uncertainties on engine design and ways to minimize existing uncertainties are discussed.

The O2 reduction at the IFC modified O2 fuel cell electrode

NASA Technical Reports Server (NTRS)

Fielder, William L.; Singer, Joseph; Baldwin, Richard S.; Johnson, Richard E.

1992-01-01

The International Fuel Corporation (IFC) state of the art (SOA) O2 electrode (Au-10 percent Pt electrocatalyst by weight) is currently being used in the alkaline H2-O2 fuel cell in the NASA Space Shuttle. Recently, IFC modified O2 electrode, as a possible replacement for the SOA electrode. In the present study, O2 reduction data were obtained for the modified electrode at temperatures between 23.3 and 91.7 C. BET measurements gave an electrode BET surface area of about 2070 sq. cm/sq. cm of geometric surface area. The Tafel data could be fitted to two straight line regions. The slope for the lower region, designated as the 0.04 V/decade region, was temperature dependent, and the transfer coefficient was about 1.5. The 'apparent' energy of activation for this region was about 19 kcal/mol. An O2 reduction mechanism for this 0.04 region is presented. In the upper region, designated as the 0.08 V/decade region, diffusion may be the controlling process. Tafel data are presented to illustrate the increase in performance with increasing temperature.

Investigation of Thermophysical Properties of Thermal Degraded Biodiesels

NASA Astrophysics Data System (ADS)

Regatieri, H. R.; Savi, E. L.; Lukasievicz, G. V. B.; Sehn, E.; Herculano, L. S.; Astrath, N. G. C.; Malacarne, L. C.

2018-06-01

Biofuels are an alternative to fossil fuels and can be made from many different raw materials. The use of distinct catalyst and production processes, feedstocks, and types of alcohol results in biofuels with different physical and chemical properties. Even though these diverse options for biodiesel production are considered advantageous, they may pose a setback when quality specifications are considered, since different properties are subject to different reactions during usage, storage and handling. In this work, we present a systematic characterization of biodiesels to investigate how accelerated thermal degradation affects fuel properties. Two different types of biodiesel, commercially obtained from distinct feedstocks, were tested. The thermal degradation process was performed by maintaining the temperature of the sample at 140°C under constant air flux for different times: 0 h, 3 h, 6 h, 9 h, 12 h, 24 h and 36 h. Properties such as density, viscosity, activation energy, volumetric thermal expansion coefficient, gross caloric value, acid value, infrared absorption, and temperature coefficient of the refractive index were used to study the thermal degradation of the biodiesel samples. The results show a significant difference in fuel properties before and after the thermal degradation process suggesting the formation of undesirable compounds. All the properties mentioned above were found to be useful to determine whether a biodiesel sample underwent thermal degradation. Moreover, viscosity and acid value were found to be the most sensitive characteristics to detect the thermal degradation process.

Improved spectral absorption coefficient grouping strategy of wide band k-distribution model used for calculation of infrared remote sensing signal of hot exhaust systems

NASA Astrophysics Data System (ADS)

Hu, Haiyang; Wang, Qiang

2018-07-01

A new strategy for grouping spectral absorption coefficients, considering the influences of both temperature and species mole ratio inhomogeneities on correlated-k characteristics of the spectra of gas mixtures, has been deduced to match the calculation method of spectral overlap parameter used in multiscale multigroup wide band k-distribution model. By comparison with current spectral absorption coefficient grouping strategies, for which only the influence of temperature inhomogeneity on the correlated-k characteristics of spectra of single species was considered, the improvements in calculation accuracies resulting from the new grouping strategy were evaluated using a series of 0D cases in which radiance under 3-5-μm wave band emitted by hot combustion gas of hydrocarbon fuel was attenuated by atmosphere with quite different temperature and mole ratios of water vapor and carbon monoxide to carbon dioxide. Finally, evaluations are presented on the calculation of remote sensing thermal images of transonic hot jet exhausted from a chevron ejecting nozzle with solid wall cooling system.

Numerical Simulation and Chaotic Analysis of an Aluminum Holding Furnace

NASA Astrophysics Data System (ADS)

Wang, Ji-min; Zhou, Yuan-yuan; Lan, Shen; Chen, Tao; Li, Jie; Yan, Hong-jie; Zhou, Jie-min; Tian, Rui-jiao; Tu, Yan-wu; Li, Wen-ke

2014-12-01

To achieve high heat efficiency, low pollutant emission and homogeneous melt temperature during thermal process of secondary aluminum, taking into account the features of aluminum alloying process, a CFD process model was developed and integrated with heat load and aluminum temperature control model. This paper presented numerical simulation of aluminum holding furnaces using the customized code based on FLUENT packages. Thermal behaviors of aluminum holding furnaces were investigated by probing into main physical fields such as flue gas temperature, velocity, and concentration, and combustion instability of aluminum holding process was represented by chaos theory. The results show that aluminum temperature uniform coefficient firstly decreases during heating phase, then increases and reduces alternately during holding phase, lastly rises during standing phase. Correlation dimension drops with fuel velocity. Maximal Lyapunov exponent reaches to a maximum when air-fuel ratio is close to 1. It would be a clear comprehension about each phase of aluminum holding furnaces to find new technology, retrofit furnace design, and optimize parameters combination.

Experimental and numerical studies of burning velocities and kinetic modeling for practical and surrogate fuels

NASA Astrophysics Data System (ADS)

Zhao, Zhenwei

To help understand the fuel oxidation process in practical combustion environments, laminar flame speeds and high temperature chemical kinetic models were studied for several practical fuels and "surrogate" fuels, such as propane, dimethyl ether (DME), and primary reference fuel (PRF) mixtures, gasoline and n-decane. The PIV system developed for the present work is described. The general principles for PIV measurements are outlined and the specific considerations are also reported. Laminar flame speeds were determined for propane/air over a range of equivalence ratios at initial temperature of 298 K, 500 K and 650 K and atmospheric pressure. Several data sets for propane/air laminar flame speeds with N 2 dilution are also reported. These results are compared to the literature data collected at the same conditions. The propane flame speed is also numerically calculated with a detailed kinetic model and multi component diffusion, including Soret effects. This thesis also presents experimentally determined laminar flame speeds for primary reference fuel (PRF) mixtures of n-heptane/iso-octane and real gasoline fuel at different initial temperature and at atmospheric pressure. Nitrogen dilution effects on the laminar flame speed are also studied for selected equivalence ratios at the same conditions. A minimization of detailed kinetic model for PRF mixtures on laminar flame speed conditions was performed and the measured flame speeds were compared with numerical predictions using this model. The measured laminar flame speeds of n-decane/air mixtures at 500 K and at atmospheric pressure with and without dilution were determined. The measured flame speeds are significantly different that those predicted using existing published kinetic models, including a model validated previously against high temperature data from flow reactor, jet-stirred reactor, shock tube ignition delay, and burner stabilized flame experiments. A significant update of this model is described which continues to predict the earlier validation experiments as well as the newly acquired laminar flame speed data and other recently published shock tube ignition delay measurements. A high temperature decomposition and oxidation model based on a hierarchical nature of reacting systems to reflect the new development in the small molecule and radical kinetics and thermochemistry and to evaluate recent measurements of DME laminar flame speeds is developed. The, thermal decomposition of DME was studied theoretically by using the RRKM/master equation approach and the high temperature model was then compared with the literature experimental data. The new model predicts well high temperature flow reactor data, high temperature shock tube ignition delays, and the species profiles from the burner-stabilized flames. Predictions of laminar flame speed and jet-stirred reactor data also reasonably agree with the available experimental data. The remaining uncertainties that need to be addressed for further model improvement will also be discussed. This thesis also presents a novel temperature-dependent feature sensitivity analysis methodology for combustion modeling. The obtained information is demonstrated to be of critical relevance in optimizing complex reaction schemes against multiple experimental targets. Applications of the presented approach are not limited to sensitivities with respect to reaction rate coefficients; the method can also be used to investigate any temperature-dependent property of interest (such as binary diffusion coefficients). This application is also demonstrated in this thesis.

Multi-Physics Simulation of TREAT Kinetics using MAMMOTH

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeHart, Mark; Gleicher, Frederick; Ortensi, Javier

With the advent of next generation reactor systems and new fuel designs, the U.S. Department of Energy (DOE) has identified the need for the resumption of transient testing of nuclear fuels. DOE has decided that the Transient Reactor Test Facility (TREAT) at Idaho National Laboratory (INL) is best suited for future testing. TREAT is a thermal neutron spectrum nuclear test facility that is designed to test nuclear fuels in transient scenarios. These specific fuels transient tests range from simple temperature transients to full fuel melt accidents. The current TREAT core is driven by highly enriched uranium (HEU) dispersed in amore » graphite matrix (1:10000 U-235/C atom ratio). At the center of the core, fuel is removed allowing for the insertion of an experimental test vehicle. TREAT’s design provides experimental flexibility and inherent safety during neutron pulsing. This safety stems from the graphite in the driver fuel having a strong negative temperature coefficient of reactivity resulting from a thermal Maxwellian shift with increased leakage, as well as graphite acting as a temperature sink. Air cooling is available, but is generally used post-transient for heat removal. DOE and INL have expressed a desire to develop a simulation capability that will accurately model the experiments before they are irradiated at the facility, with an emphasis on effective and safe operation while minimizing experimental time and cost. At INL, the Multi-physics Object Oriented Simulation Environment (MOOSE) has been selected as the model development framework for this work. This paper describes the results of preliminary simulations of a TREAT fuel element under transient conditions using the MOOSE-based MAMMOTH reactor physics tool.« less

Autoignition Studies of Diesel Alternative Biofuels

NASA Astrophysics Data System (ADS)

Wang, Weijing

The autoignition of biofuel compounds that offer potential as diesel fuel alternatives was studied under high-pressure engine-like conditions using the shock tube technique. Ignition delay times were determined in reflected shock experiments using measured pressure and electronically-excited OH emission. Measurements were made at conditions ranging from 650 to 1350 K, pressures from 6 to 50 atm, and for fuel/air/diluent mixtures at equivalence ratios from 0.5 to 2. The wide range of temperatures examined provides observation of autoignition in three reactivity regimes, including the negative temperature coefficient (NTC) regime which is characteristic of fuels containing alkyl functionalities. Compounds studied include biodiesel-related compounds and real biodiesel fuels, dimethyl ether, and 3-methylheptane which is representative of compounds found in synthetic diesel fuels produced using the Fischer-Tropsch and hydrotreatment processes. Biodiesel compounds studied include biodiesel surrogates, methyl decanoate, methyl-5-decenoate, and methyl-9-decenoate; compounds found in large quantities in biodiesels, methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate; and soy-based and animal fat based methyl ester biodiesels. Comparison of biodiesel compounds illustrates the influence of molecular structure (e.g., chain length, double bonds, and ester functionality) on reactivity. For methyl decanoate, the effect of high pressure exhaust gas recirculation (EGR) conditions relevant to internal combustion engines was also determined. Results showed that the first-order influence of EGR by displacing fuel and O2 to decrease radical branching. Measurements were compared to kinetic modeling results from models available in the literature providing varying degrees of model validation. Reaction flux analyses were also carried out to further examine the kinetic differences in different temperature regimes for fuel compounds. For example, reaction flux analyses illustrates the importance of the long alkyl chain in controlling the overall reactivity of methyl ester biodiesel compounds and the subtle role the ester group has on inhibiting low-temperature reactivity as well as the influence of branching on reactivity for lightly branched alkanes. This thesis work provides a rich database of kinetic information for biofuel-related compounds at conditions relevant to real engine operations, offering quantitative kinetic targets for the development and evaluation of future kinetic models for important alternative fuel compounds. The results quantify the reactivity variability of biodiesel alternatives and illustrate that at temperature greater than 900 to 1000 K fuel structure has little influence on reactivity, as fuel fragmentation results in an intermediate pool that is largely the same for the fuels studied. On the other hand at temperature lower than 900 K, where fuel-specific low-temperature chemistry plays a role, different fuel structures can result in vast differences in reactivity, up to factors of three or more in ignition delay.

Non-equilibrium diffusion combustion of a fuel droplet

NASA Astrophysics Data System (ADS)

Tyurenkova, Veronika V.

2012-06-01

A mathematical model for the non-equilibrium combustion of droplets in rocket engines is developed. This model allows to determine the divergence of combustion rate for the equilibrium and non-equilibrium model. Criterion for droplet combustion deviation from equilibrium is introduced. It grows decreasing droplet radius, accommodation coefficient, temperature and decreases on decreasing diffusion coefficient. Also divergence from equilibrium increases on reduction of droplet radius. Droplet burning time essentially increases under non-equilibrium conditions. Comparison of theoretical and experimental data shows that to have adequate solution for small droplets it is necessary to use the non-equilibrium model.

Increasing fuel efficiency of passenger cars with the “climate-control” system as a method of improving the ecological safety of the urban infrastructure

NASA Astrophysics Data System (ADS)

Burakova, L. N.; Burakova, A. D.; Burakova, O. D.; Dovbysh, V. O.

2018-01-01

Motor vehicle should provide safety and a high ecological standard of living for the population. One of the methods to improve the ecological friendliness of motor vehicles in particular passenger cars (cars), which are considered in this article, is the growth of their fuel economy. It is established that fuel consumption and the amount of specific emissions of harmful substances with exhaust gases of cars when using the “climate control” system depend on the effective ambient temperature, the color of the opaque car body elements, the power of the car engine and the interior volume. However, the simplest controlled factor is the color of the opaque car body elements, which is characterized by the coefficient of light reflection. In the course of experimental studies, we established the dependences of a change in fuel consumption and a share of reducing emissions of harmful substances with exhaust gases of passenger cars with the “climate control” system on the coefficient of light reflection. A method has been developed to reduce fuel consumption and the amount of specific emissions of harmful substances with the exhaust gases of passenger cars when using the “climate control” system, which involves painting the vehicle roof white and allows reducing fuel consumption by 5.5-10.3% and the amount of specific emissions of harmful substances by 0.37-1.13% (CO) and 0.47-1.08% (CH).

Correlation tests of the engine performance parameter by using the detrended cross-correlation coefficient

NASA Astrophysics Data System (ADS)

Dong, Keqiang; Gao, You; Jing, Liming

2015-02-01

The presence of cross-correlation in complex systems has long been noted and studied in a broad range of physical applications. We here focus on an aero-engine system as an example of a complex system. By applying the detrended cross-correlation (DCCA) coefficient method to aero-engine time series, we investigate the effects of the data length and the time scale on the detrended cross-correlation coefficients ρ DCCA ( T, s). We then show, for a twin-engine aircraft, that the engine fuel flow time series derived from the left engine and the right engine exhibit much stronger cross-correlations than the engine exhaust-gas temperature series derived from the left engine and the right engine do.

Cross-Correlations and Structures of Aero-Engine Gas Path System Based on DCCA Coefficient and Rooted Tree

NASA Astrophysics Data System (ADS)

Dong, Keqiang; Fan, Jie; Gao, You

2015-12-01

Identifying the mutual interaction is a crucial problem that facilitates the understanding of emerging structures in complex system. We here focus on aero-engine dynamic as an example of complex system. By applying the detrended cross-correlation analysis (DCCA) coefficient method to aero-engine gas path system, we find that the low-spool rotor speed (N1) and high-spool rotor speed (N2) fluctuation series exhibit cross-correlation characteristic. Further, we employ detrended cross-correlation coefficient matrix and rooted tree to investigate the mutual interactions of other gas path variables. The results can infer that the exhaust gas temperature (EGT), N1, N2, fuel flow (WF) and engine pressure ratio (EPR) are main gas path parameters.

Sensitivity Analysis of OECD Benchmark Tests in BISON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swiler, Laura Painton; Gamble, Kyle; Schmidt, Rodney C.

2015-09-01

This report summarizes a NEAMS (Nuclear Energy Advanced Modeling and Simulation) project focused on sensitivity analysis of a fuels performance benchmark problem. The benchmark problem was defined by the Uncertainty Analysis in Modeling working group of the Nuclear Science Committee, part of the Nuclear Energy Agency of the Organization for Economic Cooperation and Development (OECD ). The benchmark problem involv ed steady - state behavior of a fuel pin in a Pressurized Water Reactor (PWR). The problem was created in the BISON Fuels Performance code. Dakota was used to generate and analyze 300 samples of 17 input parameters defining coremore » boundary conditions, manuf acturing tolerances , and fuel properties. There were 24 responses of interest, including fuel centerline temperatures at a variety of locations and burnup levels, fission gas released, axial elongation of the fuel pin, etc. Pearson and Spearman correlatio n coefficients and Sobol' variance - based indices were used to perform the sensitivity analysis. This report summarizes the process and presents results from this study.« less

Influence of the cooling degree upon performances of internal combustion engine

NASA Astrophysics Data System (ADS)

Grǎdinariu, Andrei Cristian; Mihai, Ioan

2016-12-01

Up to present, air cooling systems still raise several unsolved problems due to conditions imposed by the environment in terms of temperature and pollution levels. The present paper investigates the impact of the engine cooling degree upon its performances, as important specific power is desired for as low as possible fuel consumption. A technical solution advanced by the authors[1], consists of constructing a bi-flux compressor, which can enhance the engine's performances. The bi-flux axial compressor accomplishes two major functions, that is it cools down the engine and it also turbocharges it. The present paper investigates the temperature changes corresponding to the fresh load, during the use of a bi-flux axial compressor. This compressor is economically simple, compact, and offers an optimal response at low rotational speeds of the engine, when two compression steps are used. The influence of the relative coefficient of air temperature drop upon working agent temperature at the intercooler exit is also investigated in the present work. The variation of the thermal load coefficient by report to the working agent temperature is also investigated during engine cooling. The variation of the average combustion temperature is analyzed in correlation to the thermal load coefficient and the temperatures of the working fluid at its exit from the cooling system. An exergetic analysis was conducted upon the influence of the cooling degree on the motor fluid and the gases resulted from the combustion process.

Gasification Characteristics of Coal/Biomass Mixed Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell, Reginald

2014-09-01

A research project was undertaken that had the overall objective of developing the models needed to accurately predict conversion rates of coal/biomass mixtures to synthesis gas under conditions relevant to a commercially-available coal gasification system configured to co-produce electric power as well as chemicals and liquid fuels. In our efforts to accomplish this goal, experiments were performed in an entrained flow reactor in order to produce coal and biomass chars at high heating rates and temperatures, typical of the heating rates and temperatures fuel particles experience in real systems. Mixed chars derived from coal/biomass mixtures containing up to 50% biomassmore » and the chars of the pure coal and biomass components were subjected to a matrix of reactivity tests in a pressurized thermogravimetric analyzer (TGA) in order to obtain data on mass loss rates as functions of gas temperature, pressure and composition as well as to obtain information on the variations in mass specific surface area during char conversion under kinetically-limited conditions. The experimental data were used as targets when determining the unknown parameters in the chemical reactivity and specific surface area models developed. These parameters included rate coefficients for the reactions in the reaction mechanism, enthalpies of formation and absolute entropies of adsorbed species formed on the carbonaceous surfaces, and pore structure coefficients in the model used to describe how the mass specific surface area of the char varies with conversion. So that the reactivity models can be used at high temperatures when mass transport processes impact char conversion rates, Thiele modulus – effectiveness factor relations were also derived for the reaction mechanisms developed. In addition, the reactivity model and a mode of conversion model were combined in a char-particle gasification model that includes the effects of chemical reaction and diffusion of reactive gases through particle pores and energy exchange between the particle and its environment. This char-particle gasification model is capable of predicting the average mass loss rates, sizes, apparent densities, specific surface areas, and temperatures of the char particles produced when co-firing coal and biomass to the type environments established in entrained flow gasifiers operating at high temperatures and elevated pressures.« less

Modelling oxygen self-diffusion in UO 2 under pressure

DOE PAGES

Cooper, Michael William D.; Grimes, R. W.; Fitzpatrick, M. E.; ...

2015-10-22

Access to values for oxygen self-diffusion over a range of temperatures and pressures in UO 2 is important to nuclear fuel applications. Here, elastic and expansivity data are used in the framework of a thermodynamic model, the cBΩ model, to derive the oxygen self-diffusion coefficient in UO 2 over a range of pressures (0–10 GPa) and temperatures (300–1900 K). Furthermore, the significant reduction in oxygen self-diffusion as a function of increasing hydrostatic pressure, and the associated increase in activation energy, is identified.

Fundamental Studies of Droplet Interactions in Dense Sprays

DTIC Science & Technology

1992-12-31

correlations for the drag coefficients, Nusselt numbers, and Sherwood numbers for hydrocarbon fuel droplets in dense sprays were obtained. 14. SUBJECYTEM...tions for the drag coefficients, Nusselt numbers, and Sherwood numbers for hydrocarbon fuel droplets in dense sprays were obtained. Nomenclature a...the drag coefficient, lift coefficient, moment coefficient, Nusselt number, Sherwood number, and vaporization rates are different from those of an

Physical, mechanical and electrochemical characterization of all-perovskite intermediate temperature solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Mohammadi, Alidad

Strontium- and magnesium-doped lanthanum gallate (LSGM) has been considered as a promising electrolyte for solid oxide fuel cell (SOFC) systems in recent years due to its high ionic conductivity and chemical stability over a wide range of oxygen partial pressures and temperatures. This research describes synthesis, physical and mechanical behavior, electrochemical properties, phase evolution, and microstructure of components of an all-perovskite anode-supported intermediate temperature solid oxide fuel cell (ITSOFC), based on porous La 0.75Sr0.25Cr0.5Mn0.5O3 (LSCM) anode, La0.8Sr0.2Ga0.8Mg0.2O 2.8 (LSGM) electrolyte, and porous La0.6Sr0.4Fe 0.8Co0.2O3 (LSCF) cathode. The phase evolution of synthesized LSGM and LSCM powders has been investigated, and it has been confirmed that there is no reaction between LSGM and LSCM at sintering temperature. Using different amounts of poreformers and binders as well as controlling firing temperature, porosity of the anode was optimized while still retaining good mechanical integrity. The effect of cell operation conditions under dry hydrogen fuel on the SOFC open circuit voltage (OCV) and cell performance were also investigated. Characterization study of the synthesized LSGM indicates that sintering at 1500°C obtains higher electrical conductivity compared to the currently published results, while conductivity of pellets sintered at 1400°C and 1450°C would be slightly lower. The effect of sintering temperature on bulk and grain boundary resistivities was also discussed. The mechanical properties, such as hardness, Young's modulus, fracture toughness and modulus of rupture of the electrolyte were determined and correlated with scanning electron microscopy (SEM) morphological characterization. Linear thermal expansion and thermal expansion coefficient of LSGM were also measured.

High Temperature Reactor (HTR) Deep Burn Core and Fuel Analysis: Design Selection for the Prismatic Block Reactor With Results from FY-2011 Activities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael A. Pope

2011-10-01

The Deep Burn (DB) Project is a U.S. Department of Energy sponsored feasibility study of Transuranic Management using high burnup fuel in the high temperature helium cooled reactor (HTR). The DB Project consists of seven tasks: project management, core and fuel analysis, spent fuel management, fuel cycle integration, TRU fuel modeling, TRU fuel qualification, and HTR fuel recycle. In the Phase II of the Project, we conducted nuclear analysis of TRU destruction/utilization in the HTR prismatic block design (Task 2.1), deep burn fuel/TRISO microanalysis (Task 2.3), and synergy with fast reactors (Task 4.2). The Task 2.1 covers the core physicsmore » design, thermo-hydraulic CFD analysis, and the thermofluid and safety analysis (low pressure conduction cooling, LPCC) of the HTR prismatic block design. The Task 2.3 covers the analysis of the structural behavior of TRISO fuel containing TRU at very high burnup level, i.e. exceeding 50% of FIMA. The Task 4.2 includes the self-cleaning HTR based on recycle of HTR-generated TRU in the same HTR. Chapter IV contains the design and analysis results of the 600MWth DB-HTR core physics with the cycle length, the average discharged burnup, heavy metal and plutonium consumptions, radial and axial power distributions, temperature reactivity coefficients. Also, it contains the analysis results of the 450MWth DB-HTR core physics and the analysis of the decay heat of a TRU loaded DB-HTR core. The evaluation of the hot spot fuel temperature of the fuel block in the DB-HTR (Deep-Burn High Temperature Reactor) core under full operating power conditions are described in Chapter V. The investigated designs are the 600MWth and 460MWth DB-HTRs. In Chapter VI, the thermo-fluid and safety of the 600MWth DB-HTRs has been analyzed to investigate a thermal-fluid design performance at the steady state and a passive safety performance during an LPCC event. Chapter VII describes the analysis results of the TRISO fuel microanalysis of the 600MWth and 450MWth DB-HTRs. The TRISO fuel microanalysis covers the gas pressure buildup in a coated fuel particle including helium production, the thermo-mechanical behavior of a CFP, the failure probabilities of CFPs, the temperature distribution in a CPF, and the fission product (FP) transport in a CFP and a graphite. In Chapter VIII, it contains the core design and analysis of sodium cooled fast reactor (SFR) with deep burn HTR reactor. It considers a synergistic combination of the DB-MHR and an SFR burner for a safe and efficient transmutation of the TRUs from LWRs. Chapter IX describes the design and analysis results of the self-cleaning (or self-recycling) HTR core. The analysis is considered zero and 5-year cooling time of the spent LWR fuels.« less

High Temperature Reactor (HTR) Deep Burn Core and Fuel Analysis: Design Selection for the Prismatic Block Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Francesco Venneri; Chang-Keun Jo; Jae-Man Noh

2010-09-01

The Deep Burn (DB) Project is a U.S. Department of Energy sponsored feasibility study of Transuranic Management using high burnup fuel in the high temperature helium cooled reactor (HTR). The DB Project consists of seven tasks: project management, core and fuel analysis, spent fuel management, fuel cycle integration, TRU fuel modeling, TRU fuel qualification, and HTR fuel recycle. In the Phase II of the Project, we conducted nuclear analysis of TRU destruction/utilization in the HTR prismatic block design (Task 2.1), deep burn fuel/TRISO microanalysis (Task 2.3), and synergy with fast reactors (Task 4.2). The Task 2.1 covers the core physicsmore » design, thermo-hydraulic CFD analysis, and the thermofluid and safety analysis (low pressure conduction cooling, LPCC) of the HTR prismatic block design. The Task 2.3 covers the analysis of the structural behavior of TRISO fuel containing TRU at very high burnup level, i.e. exceeding 50% of FIMA. The Task 4.2 includes the self-cleaning HTR based on recycle of HTR-generated TRU in the same HTR. Chapter IV contains the design and analysis results of the 600MWth DB-HTR core physics with the cycle length, the average discharged burnup, heavy metal and plutonium consumptions, radial and axial power distributions, temperature reactivity coefficients. Also, it contains the analysis results of the 450MWth DB-HTR core physics and the analysis of the decay heat of a TRU loaded DB-HTR core. The evaluation of the hot spot fuel temperature of the fuel block in the DB-HTR (Deep-Burn High Temperature Reactor) core under full operating power conditions are described in Chapter V. The investigated designs are the 600MWth and 460MWth DB-HTRs. In Chapter VI, the thermo-fluid and safety of the 600MWth DB-HTRs has been analyzed to investigate a thermal-fluid design performance at the steady state and a passive safety performance during an LPCC event. Chapter VII describes the analysis results of the TRISO fuel microanalysis of the 600MWth and 450MWth DB-HTRs. The TRISO fuel microanalysis covers the gas pressure buildup in a coated fuel particle including helium production, the thermo-mechanical behavior of a CFP, the failure probabilities of CFPs, the temperature distribution in a CPF, and the fission product (FP) transport in a CFP and a graphite. In Chapter VIII, it contains the core design and analysis of sodium cooled fast reactor (SFR) with deep burn HTR reactor. It considers a synergistic combination of the DB-MHR and an SFR burner for a safe and efficient transmutation of the TRUs from LWRs. Chapter IX describes the design and analysis results of the self-cleaning (or self-recycling) HTR core. The analysis is considered zero and 5-year cooling time of the spent LWR fuels.« less

Analysis of Thermal and Chemical Effets on Negative Valve Overlap Period Energy Recovery for Low-Temperature Gasoline Combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ekoto, Dr Isaac; Peterson, Dr. Brian; Szybist, James P

2015-01-01

A central challenge for efficient auto-ignition controlled low-temperature gasoline combustion (LTGC) engines has been achieving the combustion phasing needed to reach stable performance over a wide operating regime. The negative valve overlap (NVO) strategy has been explored as a way to improve combustion stability through a combination of charge heating and altered reactivity via a recompression stroke with a pilot fuel injection. The study objective was to analyze the thermal and chemical effects on NVO-period energy recovery. The analysis leveraged experimental gas sampling results obtained from a single-cylinder LTGC engine along with cylinder pressure measurements and custom data reduction methodsmore » used to estimate period thermodynamic properties. The engine was fueled by either iso-octane or ethanol, and operated under sweeps of NVO-period oxygen concentration, injection timing, and fueling rate. Gas sampling at the end of the NVO period was performed via a custom dump-valve apparatus, with detailed sample speciation by in-house gas chromatography. The balance of NVO-period input and output energy flows was calculated in terms of fuel energy, work, heat loss, and change in sensible energy. Experiment results were complemented by detailed chemistry single-zone reactor simulations performed at relevant mixing and thermodynamic conditions, with results used to evaluate ignition behavior and expected energy recovery yields. For the intermediate bulk-gas temperatures present during the NVO period (900-1100 K), weak negative temperature coefficient behavior with iso-octane fueling significantly lengthened ignition delays relative to similar ethanol fueled conditions. Faster ethanol ignition chemistry led to lower recovered fuel intermediate yields relative to similar iso-octane fueled conditions due to more complete fuel oxidation. From the energy analysis it was found that increased NVO-period global equivalence ratio, either from lower NVOperiod oxygen concentrations or higher fueling rates, in general led to a greater fraction of net recovered fuel energy and work as heat losses were minimized. These observations were supported by complementary single-zone reactor model results, which further indicated that kinetic time-scales favor chemical energy-consuming exothermic oxidation over slower endothermic reformation. Nonetheless, fuel energy recovery close to the thermodynamic equilibrium solution was achieved for baseline conditions that featured 4% NVO-period oxygen concentration.« less

Investigation of concentration-dependence of thermodynamic properties of lanthanum, yttrium, scandium and terbium in eutectic LiCl-KCl molten salt

NASA Astrophysics Data System (ADS)

Wang, Yafei; Zhou, Wentao; Zhang, Jinsuo

2016-09-01

Thermodynamic properties of rare earth metals in LiCl-KCl molten salt electrolyte are crucial to the development of electrochemical separation for the treatment of used nuclear fuels. In the present study, activity coefficient, apparent potential, and diffusion coefficient of lanthanum, yttrium, scandium, and terbium in the molten salt (58 at% LiCl and 42 at% KCl) were calculated by the method of molecular dynamics simulation up to a concentration around 3 at% at temperatures of 723 K and 773 K. It was found that the activity coefficient and the apparent potential increase with the species concentration while diffusion coefficient shows a trend of increase followed by decrease. The calculated results were validated by available measurement data of dilution cases. This research extends the range of data to a wide component and would provide further insight to the pyroprocessing design and safeguards.

Products from the Oxidation of Linear Isomers of Hexene

PubMed Central

Battin-Leclerc, Frédérique; Rodriguez, Anne; Husson, Benoit; Herbinet, Olivier; Glaude, Pierre-Alexandre; Wang, Zhandong; Cheng, Zhanjun; Qi, Fei

2014-01-01

The experimental study of the oxidation of the three linear isomers of hexene was performed in a quartz isothermal jet-stirred reactor (JSR) at temperatures ranging from 500 to 1100 K including the negative temperature coefficient (NTC) zone, at quasi-atmospheric pressure (1.07 bar), at a residence time of 2 s and with dilute stoichiometric mixtures. The fuel and reaction product mole fractions were measured using online gas chromatography. In the case of 1-hexene, the JSR has also been coupled through a molecular-beam sampling system to a reflectron time-of-flight mass spectrometer combined with tunable synchrotron vacuum ultraviolet photoionization. A difference of reactivity between the three fuels which varies with the temperature range has been observed and is discussed according to the changes in the possible reaction pathways when the double bond is displaced. An enhanced importance of the reactions via the Waddington mechanism and of those of allylic radicals with HO2 radicals can be noted for 2- and 3-hexenes compared to 1-hexene. PMID:24400665

CRITICAL TESTS FOR PRT REACTOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Triplett, J.R.; Anderson, J.K.; Dunn, R.E.

1960-07-01

Critical teste to be performed on the Plutonium Recycle Te st Heactor are described. Exponential, approach-tocritical, critical, and substitution experiments will be carried out. These experiments include: calibration of moderator level; determination of the wori of various fuel loadings; calibration of the shim system including determination of maximum control strength of the entire system; substitution experiments to determine reflector savings, void effects, effects of H/sub 2/O and degraded D/sub 2/O coolants, and effects of loop and other material intsllations; determination of fuel-plus-coolant and moderator temperature coefficients; and kinetic experiments to determine response of the reactor to reactivity changes. (M.C.G.)

Calculation of Heat-Bearing Agent’s Steady Flow in Fuel Bundle

NASA Astrophysics Data System (ADS)

Amosova, E. V.; Guba, G. G.

2017-11-01

This paper introduces the result of studying the heat exchange in the fuel bundle of the nuclear reactor’s fuel magazine. The article considers the fuel bundle of the infinite number of fuel elements, fuel elements are considered in the checkerboard fashion (at the tops of a regular triangle a fuel element is a plain round rod. The inhomogeneity of volume energy release in the rod forms the inhomogeneity of temperature and velocity fields, and pressure. Computational methods for studying hydrodynamics in magazines and cores with rod-shape fuel elements are based on a significant simplification of the problem: using basic (averaged) equations, isobaric section hypothesis, porous body model, etc. This could be explained by the complexity of math description of the three-dimensional fluid flow in the multi-connected area with the transfer coefficient anisotropy, curved boundaries and technical computation difficulties. Thus, calculative studying suggests itself as promising and important. There was developed a method for calculating the heat-mass exchange processes of inter-channel fuel element motions, which allows considering the contribution of natural convection to the heat-mass exchange based on the Navier-Stokes equations and Boussinesq approximation.

Validation of the new code package APOLLO2.8 for accurate PWR neutronics calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santamarina, A.; Bernard, D.; Blaise, P.

2013-07-01

This paper summarizes the Qualification work performed to demonstrate the accuracy of the new APOLLO2.S/SHEM-MOC package based on JEFF3.1.1 nuclear data file for the prediction of PWR neutronics parameters. This experimental validation is based on PWR mock-up critical experiments performed in the EOLE/MINERVE zero-power reactors and on P.I. Es on spent fuel assemblies from the French PWRs. The Calculation-Experiment comparison for the main design parameters is presented: reactivity of UOX and MOX lattices, depletion calculation and fuel inventory, reactivity loss with burnup, pin-by-pin power maps, Doppler coefficient, Moderator Temperature Coefficient, Void coefficient, UO{sub 2}-Gd{sub 2}O{sub 3} poisoning worth, Efficiency ofmore » Ag-In-Cd and B4C control rods, Reflector Saving for both standard 2-cm baffle and GEN3 advanced thick SS reflector. From this qualification process, calculation biases and associated uncertainties are derived. This code package APOLLO2.8 is already implemented in the ARCADIA new AREVA calculation chain for core physics and is currently under implementation in the future neutronics package of the French utility Electricite de France. (authors)« less

Heat Transfer Enhancement By Three-Dimensional Surface Roughness Technique In Nuclear Fuel Rod Bundles

NASA Astrophysics Data System (ADS)

Najeeb, Umair

This thesis experimentally investigates the enhancement of single-phase heat transfer, frictional loss and pressure drop characteristics in a Single Heater Element Loop Tester (SHELT). The heater element simulates a single fuel rod for Pressurized Nuclear reactor. In this experimental investigation, the effect of the outer surface roughness of a simulated nuclear rod bundle was studied. The outer surface of a simulated fuel rod was created with a three-dimensional (Diamond-shaped blocks) surface roughness. The angle of corrugation for each diamond was 45 degrees. The length of each side of a diamond block is 1 mm. The depth of each diamond block was 0.3 mm. The pitch of the pattern was 1.614 mm. The simulated fuel rod had an outside diameter of 9.5 mm and wall thickness of 1.5 mm and was placed in a test-section made of 38.1 mm inner diameter, wall thickness 6.35 mm aluminum pipe. The Simulated fuel rod was made of Nickel 200 and Inconel 625 materials. The fuel rod was connected to 10 KW DC power supply. The Inconel 625 material of the rod with an electrical resistance of 32.3 kO was used to generate heat inside the test-section. The heat energy dissipated from the Inconel tube due to the flow of electrical current flows into the working fluid across the rod at constant heat flux conditions. The DI water was employed as working fluid for this experimental investigation. The temperature and pressure readings for both smooth and rough regions of the fuel rod were recorded and compared later to find enhancement in heat transfer coefficient and increment in the pressure drops. Tests were conducted for Reynold's Numbers ranging from 10e4 to 10e5. Enhancement in heat transfer coefficient at all Re was recorded. The maximum heat transfer co-efficient enhancement recorded was 86% at Re = 4.18e5. It was also observed that the pressure drop and friction factor increased by 14.7% due to the increased surface roughness.

Performance of Transuranic-Loaded Fully Ceramic Micro-Encapsulated Fuel in LWRs Final Report, Including Void Reactivity Evaluation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael A. Pope; R. Sonat Sen; Brian Boer

2011-09-01

The current focus of the Deep Burn Project is on once-through burning of transuranics (TRU) in light-water reactors (LWRs). The fuel form is called Fully-Ceramic Micro-encapsulated (FCM) fuel, a concept that borrows the tri-isotropic (TRISO) fuel particle design from high-temperature reactor technology. In the Deep Burn LWR (DB-LWR) concept, these fuel particles are pressed into compacts using SiC matrix material and loaded into fuel pins for use in conventional LWRs. The TRU loading comes from the spent fuel of a conventional LWR after 5 years of cooling. Unit cell and assembly calculations have been performed using the DRAGON-4 code tomore » assess the physics attributes of TRU-only FCM fuel in an LWR lattice. Depletion calculations assuming an infinite lattice condition were performed with calculations of various reactivity coefficients performed at each step. Unit cells and assemblies containing typical UO2 and mixed oxide (MOX) fuel were analyzed in the same way to provide a baseline against which to compare the TRU-only FCM fuel. Then, assembly calculations were performed evaluating the performance of heterogeneous arrangements of TRU-only FCM fuel pins along with UO2 pins.« less

Testing of an Integrated Reactor Core Simulator and Power Conversion System with Simulated Reactivity Feedback

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Hervol, David S.; Godfroy, Thomas J.

2009-01-01

A Direct Drive Gas-Cooled (DDG) reactor core simulator has been coupled to a Brayton Power Conversion Unit (BPCU) for integrated system testing at NASA Glenn Research Center (GRC) in Cleveland, OH. This is a closed-cycle system that incorporates an electrically heated reactor core module, turbo alternator, recuperator, and gas cooler. Nuclear fuel elements in the gas-cooled reactor design are replaced with electric resistance heaters to simulate the heat from nuclear fuel in the corresponding fast spectrum nuclear reactor. The thermodynamic transient behavior of the integrated system was the focus of this test series. In order to better mimic the integrated response of the nuclear-fueled system, a simulated reactivity feedback control loop was implemented. Core power was controlled by a point kinetics model in which the reactivity feedback was based on core temperature measurements; the neutron generation time and the temperature feedback coefficient are provided as model inputs. These dynamic system response tests demonstrate the overall capability of a non-nuclear test facility in assessing system integration issues and characterizing integrated system response times and response characteristics.

Testing of an Integrated Reactor Core Simulator and Power Conversion System with Simulated Reactivity Feedback

NASA Technical Reports Server (NTRS)

Bragg-Sitton, Shannon M.; Hervol, David S.; Godfroy, Thomas J.

2010-01-01

A Direct Drive Gas-Cooled (DDG) reactor core simulator has been coupled to a Brayton Power Conversion Unit (BPCU) for integrated system testing at NASA Glenn Research Center (GRC) in Cleveland, Ohio. This is a closed-cycle system that incorporates an electrically heated reactor core module, turboalternator, recuperator, and gas cooler. Nuclear fuel elements in the gas-cooled reactor design are replaced with electric resistance heaters to simulate the heat from nuclear fuel in the corresponding fast spectrum nuclear reactor. The thermodynamic transient behavior of the integrated system was the focus of this test series. In order to better mimic the integrated response of the nuclear-fueled system, a simulated reactivity feedback control loop was implemented. Core power was controlled by a point kinetics model in which the reactivity feedback was based on core temperature measurements; the neutron generation time and the temperature feedback coefficient are provided as model inputs. These dynamic system response tests demonstrate the overall capability of a non-nuclear test facility in assessing system integration issues and characterizing integrated system response times and response characteristics.

Effects of non-unity Lewis numbers in diffusion flames

NASA Technical Reports Server (NTRS)

Linan, A.; Orlandi, P.; Verzicco, R.; Higuera, F. J.

1994-01-01

The purpose of this work is to carry out direct numerical simulations of diffusion controlled combustion with non-unity Lewis numbers for the reactants and products, thus accounting for the differential diffusion effects of the temperature and concentration fields. We use a formulation based on combining the conservation equations in a way to eliminate the reaction terms similar to the method used by Burke and Schumann (1928) for unity Lewis numbers. We present calculations for an axisymmetric fuel jet and for a planar, time evolving mixing layer, leaving out the effects of thermal expansion and variations of the transport coefficients due to the heat release. Our results show that the front of the flame shifts toward the fuel or oxygen sides owing to the effect of the differential diffusion and that the location of maximum temperature may not coincide with the flame. The dependence of the distribution of the reaction products on their Lewis number has been investigated.

Laser absorption-scattering technique applied to asymmetric evaporating fuel sprays for simultaneous measurement of vapor/liquid mass distributions

NASA Astrophysics Data System (ADS)

Gao, J.; Nishida, K.

2010-10-01

This paper describes an Ultraviolet-Visible Laser Absorption-Scattering (UV-Vis LAS) imaging technique applied to asymmetric fuel sprays. Continuing from the previous studies, the detailed measurement principle was derived. It is demonstrated that, by means of this technique, cumulative masses and mass distributions of vapor/liquid phases can be quantitatively measured no matter what shape the spray is. A systematic uncertainty analysis was performed, and the measurement accuracy was also verified through a series of experiments on the completely vaporized fuel spray. The results show that the Molar Absorption Coefficient (MAC) of the test fuel, which is typically pressure and temperature dependent, is the major error source. The measurement error in the vapor determination has been shown to be approximately 18% under the assumption of constant MAC of the test fuel. Two application examples of the extended LAS technique were presented for exploring the dynamics and physical insight of the evaporating fuel sprays: diesel sprays injected by group-hole nozzles and gasoline sprays impinging on an inclined wall.

Thermal finite-element analysis of space shuttle main engine turbine blade

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Tong, Michael T.; Kaufman, Albert

1987-01-01

Finite-element, transient heat transfer analyses were performed for the first-stage blades of the space shuttle main engine (SSME) high-pressure fuel turbopump. The analyses were based on test engine data provided by Rocketdyne. Heat transfer coefficients were predicted by performing a boundary-layer analysis at steady-state conditions with the STAN5 boundary-layer code. Two different peak-temperature overshoots were evaluated for the startup transient. Cutoff transient conditions were also analyzed. A reduced gas temperature profile based on actual thermocouple data was also considered. Transient heat transfer analyses were conducted with the MARC finite-element computer code.

Influence of Jet Fuel Composition on Aircraft Engine Emissions: A Synthesis of Aerosol Emissions Data from the NASA APEX, AAFEX, and ACCESS Missions

NASA Astrophysics Data System (ADS)

Moore, R.; Shook, M.; Beyersdorf, A. J.; Corr, C.; Herndon, S. C.; Knighton, W. B.; Miake-Lye, R. C.; Thornhill, K. L., II; Winstead, E.; Yu, Z.; Ziemba, L. D.; Anderson, B. E.

2015-12-01

We statistically analyze the impact of jet fuel properties on aerosols emitted by the NASA McDonnell Douglas DC-8 CFM56-2-C1 engines burning fifteen different aviation fuels. Data were collected for this single engine type during four different, comprehensive ground tests conducted over the past decade, which allow us to clearly link changes in aerosol emissions to fuel compositional changes. It is found that the volatile aerosol fraction dominates the number and volume emissions indices (EIs) over all engine powers, which are driven by changes in fuel aromatic and sulfur content. Meanwhile, the naphthalenic content of the fuel determines the magnitude of the non-volatile number and volume EI as well as the black carbon mass EI. Linear regression coefficients are reported for each aerosol EI in terms of these properties, engine fuel flow rate, and ambient temperature, and show that reducing both fuel sulfur content and napththalenes to near-zero levels would result in roughly a ten-fold decrease in aerosol number emitted per kg of fuel burn. This work informs future efforts to model aircraft emissions changes as the aviation fleet gradually begins to transition toward low-aromatic, low-sulfur alternative jet fuels from bio-based or Fischer-Tropsch production pathways.

Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part II: Loss of gas-tightness, electrical contact and thermal buckling

NASA Astrophysics Data System (ADS)

Nakajo, Arata; Wuillemin, Zacharie; Van herle, Jan; Favrat, Daniel

Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depending on the component. First, the cells accumulate residual stresses due to the sintering phase during the manufacturing process. Further, the load applied during assembly of the stack to ensure electric contact and flatten the cells prevents a completely stress-free expansion of each component during the heat-up. Finally, thermal gradients cause additional stresses in operation. The temperature profile generated by a thermo-electrochemical model implemented in an equation-oriented process modelling tool (gPROMS) was imported into finite-element software (ABAQUS) to calculate the distribution of stress and contact pressure on all components of a standard solid oxide fuel cell repeat unit. The different layers of the cell in exception of the cathode, i.e. anode, electrolyte and compensating layer were considered in the analysis to account for the cell curvature. Both steady-state and dynamic simulations were performed, with an emphasis on the cycling of the electrical load. The study includes two different types of cell, operation under both thermal partial oxidation and internal steam-methane reforming and two different initial thicknesses of the air and fuel compressive sealing gaskets. The results generated by the models are presented in two papers: Part I focuses on cell cracking. In the present paper, Part II, the occurrences of loss of gas-tightness in the compressive gaskets and/or electrical contact in the gas diffusion layer were identified. In addition, the dependence on temperature of both coefficients of thermal expansion and Young's modulus of the metallic interconnect (MIC) were implemented in the finite-element model to compute the plastic deformation, while the possibilities of thermal buckling were analysed in a dedicated and separate model. The value of the minimum stable thickness of the MIC is large, even though significantly affected by the operating conditions. This phenomenon prevents any unconsidered decrease of the thickness to reduce the thermal inertia of the stack. Thermal gradients and the shape of the temperature profile during operation induce significant decreases of the contact pressure on the gaskets near the fuel manifold, at the inlet or outlet, depending on the flow configuration. On the contrary, the electrical contact was ensured independently of the operating point and history, even though plastic strain developed in the gas diffusion layer.

Air Separation Using Hollow Fiber Membranes

NASA Technical Reports Server (NTRS)

Huang, Stephen E.

2004-01-01

The NASA Glenn Research Center in partnership with the Ohio Aerospace Institute provides internship programs for high school and college students in the areas of science, engineering, professional administrative, and other technical areas. During the summer of 2004, I worked with Dr. Clarence T. Chang at NASA Glenn Research Center s combustion branch on air separation using hollow fiber membrane technology. . In light of the accident of Trans World Airline s flight 800, FAA has mandated that a suitable solution be created to prevent the ignition of fuel tanks in aircrafts. In order for any type of fuel to ignite, three important things are needed: fuel vapor, oxygen, and an energy source. Two different ways to make fuel tanks less likely to ignite are reformulating the fuel to obtain a lower vapor pressure for the fuel and or using an On Board Inert Gas Generating System (OBIGGS) to inert the Central Wing Tank. goal is to accomplish the mission, which means that the Air Separation Module (ASM) tends to be bulky and heavy. The primary goal for commercial aviation companies is to transport as much as they can with the least amount of cost and fuel per person, therefore the ASM must be compact and light as possible. The plan is to take bleed air from the aircraft s engines to pass air through a filter first to remove particulates and then pass the air through the ASM containing hollow fiber membranes. In the lab, there will be a heating element provided to simulate the temperature of the bleed air that will be entering the ASM and analysis of the separated air will be analyzed by a Gas Chromatograph/Mass Spectrometer (GC/MS). The GUMS will separate the different compounds in the exit streams of the ASM and provide information on the performance of hollow fiber membranes. Hopefully I can develop ways to improve efficiency of the ASM. different types of jet fuel were analyzed and data was well represented on SAE Paper 982485. Data consisted of the concentrations of over 300 different hydrocarbons commonly found in JP- 8, Jet A, and JP-5 fuels. I researched the major hydrocarbons that has a concentration of greater than 50 parts per million and found the vapor pressure data coefficients for a specific temperature range. The coefficients were applied to Antoine s Equation and Riedel's Equation to calculate the vapor pressures for that specific hydrocarbon in the specific temperature range. With the vapor pressure data scientists can formulate a fuel composition that has a lower vapor pressure profile, therefore making jet fuels less flammable. work, learn how to operate and examine the data from Gas Chromatograph and Mass Spectrometer, and develop new ways in applying hollow fiber membrane technology to other areas of environmental engineering. The United States military currently uses air separation technology and their primary The other side of making air travel safer is to reformulate the fuel. Analyses of three My goal this summer is to learn about hollow fiber membrane technologies and how they

Fuel alcohol biosynthesis by Zymomonas anaerobia: optimization studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kosaric, N.; Ong, S.L.; Davnjak, Z.

1982-03-01

The optimum operating conditions for growth and ethanol production of Zymomonas anaerobia ATCC 29501 were established. The optimum pH range and temperature were found to be 5.0-6.0 and 35/sup 0/C, respectively. Based on the results obtained from the temperature optimization study, an Arrhenius-type temperature relationship for the specific growth rate was developed. The growth and ethanol production of this microbe also have been optimized in terms of concentrations of glucose, essential nutrients, and minerals. With optimum medium and operating conditions, an ethanol concentration of 96 g/L was obtained in 23h. Both growth and ethanol yield coefficients in dependence on initialmore » glucose concentrations were determined.« less

Fuel alcohol biosynthesis by Zymomonas anaerobia: optimization studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kosaric, N.; Ong, S.L.; Duvnjak, Z.

1982-03-01

The optimum operating conditions for growth and ethanol production of Zymomonas anaerobia ATCC 29501 were established. The optimum pH range and temperature were found to be 5.0-6.0 and 35 degrees C, respectively. Based on the results obtained from the temperature optimization study, an Arrhenius-type temperature relationship for the specific growth rate was developed. The growth and ethanol production of this microbe also have been optimized in terms of concentrations of glucose, essential nutrients, and minerals. With optimum medium and operating conditions, an ethanol concentration of 96 g/L was obtained in 23 hours. Both growth and ethanol yield coefficients in dependencemore » on initial glucose concentrations were determined. (Refs. 16).« less

Mesocarbon microbead based graphite for spherical fuel element to inhibit the infiltration of liquid fluoride salt in molten salt reactor

NASA Astrophysics Data System (ADS)

Zhong, Yajuan; Zhang, Junpeng; Lin, Jun; Xu, Liujun; Zhang, Feng; Xu, Hongxia; Chen, Yu; Jiang, Haitao; Li, Ziwei; Zhu, Zhiyong; Guo, Quangui

2017-07-01

Mesocarbon microbeads (MCMB) and quasi-isostatic pressing method were used to prepare MCMB based graphite (MG) for spherical fuel element to inhibit the infiltration of liquid fluoride salt in molten salt reactor (MSR). Characteristics of mercury infiltration and molten salt infiltration in MG were investigated and compared with A3-3 (graphite for spherical fuel element in high temperature gas cooled reactor) to identify the infiltration behaviors. The results indicated that MG had a low porosity about 14%, and an average pore diameter of 96 nm. Fluoride salt occupation of A3-3 (average pore diameter was 760 nm) was 10 wt% under 6.5 atm, whereas salt gain did not infiltrate in MG even up to 6.5 atm. It demonstrated that MG could inhibit the infiltration of liquid fluoride salt effectively. Coefficient of thermal expansion (CTE) of MG lies in 6.01 × 10-6 K-1 (α∥) and 6.15 × 10-6 K-1 (α⊥) at the temperature range of 25-700 °C. The anisotropy factor of MG calculated by CTE maintained below 1.02, which could meet the requirement of the spherical fuel element (below 1.30). The constant isotropic property of MG is beneficial for the integrity and safety of the graphite used in the spherical fuel element for a MSR.

Heat transfer to throat tubes in a square-chambered rocket engine at the NASA Lewis Research Center

NASA Technical Reports Server (NTRS)

Nesbitt, James A.; Brindley, William J.

1989-01-01

A gaseous H2/O2 rocket engine was constructed at the NASA-Lewis to provide a high heat flux source representative of the heat flux to the blades in the high pressure fuel turbopump (HPFTP) during startup of the space shuttle main engines. The high heat flux source was required to evaluate the durability of thermal barrier coatings being investigated for use on these blades. The heat transfer, and specifically, the heat flux to tubes located at the throat of the test rocket engine was evaluated and compared to the heat flux to the blades in the HPFTP during engine startup. Gas temperatures, pressures and heat transfer coefficients in the test rocket engine were measured. Near surface metal temperatures below thin thermal barrier coatings were also measured at various angular orientations around the throat tube to indicate the angular dependence of the heat transfer coefficients. A finite difference model for a throat tube was developed and a thermal analysis was performed using the measured gas temperatures and the derived heat transfer coefficients to predict metal temperatures in the tube. Near surface metal temperatures of an uncoated throat tube were measured at the stagnation point and showed good agreement with temperatures predicted by the thermal model. The maximum heat flux to the throat tube was calculated and compared to that predicted for the leading edge of an HPFTP blade. It is shown that the heat flux to an uncooled throat tube is slightly greater than the heat flux to an HPFTP blade during engine startup.

Study of CO 2 stability and electrochemical oxygen activation of mixed conductors with low thermal expansion coefficient based on the TbBaCo 3ZnO 7+ δ system

NASA Astrophysics Data System (ADS)

Vert, Vicente B.; Serra, José M.

The influence of different application-oriented factors on the electrochemical activity and stability of TbBaCo 3ZnO 7+ δ when used as a solid oxide fuel cell cathode has been studied. Calcination at temperatures above 900 °C (e.g. 1000 °C) leads to a significant increase in the electrode polarization resistance. The effect of the sintering temperature of the TbBaCo 3ZnO 7+ δ cathode seems to be more important than the effect produced by the Tb substitution as observed when compared with 900 °C-sintered YBaCo 3ZnO 7+ δ; and ErBaCo 3ZnO 7+ δ electrode performances. The presence of CO 2 in the air flow leads to an increase of roughly 10% in the polarization resistance for the whole studied temperature range (500-850 °C) while this effect is reversible. Analysis of the impedance spectroscopy measurements shows that the exchange rate constant (k G from Gerischer element) is significantly affected by CO 2 at temperatures below 700 °C, while the diffusion coefficient related parameter is slightly influenced at low temperatures. Electrode degrades with a low constant rate of 1 mΩ cm 2 h -1 after 60 h. This cathode material exhibits high CO 2 tolerance, as shown by temperature programmed treatment under a continuous gas flow of air with 5% CO 2, and a relatively low thermal expansion coefficient.

A method for monitoring nuclear absorption coefficients of aviation fuels

NASA Technical Reports Server (NTRS)

Sprinkle, Danny R.; Shen, Chih-Ping

1989-01-01

A technique for monitoring variability in the nuclear absorption characteristics of aviation fuels has been developed. It is based on a highly collimated low energy gamma radiation source and a sodium iodide counter. The source and the counter assembly are separated by a geometrically well-defined test fuel cell. A computer program for determining the mass attenuation coefficient of the test fuel sample, based on the data acquired for a preset counting period, has been developed and tested on several types of aviation fuel.

Investigations of ash fouling with cattle wastes as reburn fuel in a small-scale boiler burner under transient conditions.

PubMed

Oh, Hyukjin; Annamalai, Kalyan; Sweeten, John M

2008-04-01

Fouling behavior under reburn conditions was investigated with cattle wastes (termed as feedlot biomass [FB]) and coal as reburn fuels under a transient condition and short-time operation. A small-scale (30 kW or 100,000 Btu/hr) boiler burner research facility was used for the reburn experiments. The fuels considered for these experiments were natural gas (NG) for the ashless case, pure coal, pure FB, and blends of coal and FB. Two parameters that were used to characterize the ash "fouling" were (1) the overall heat-transfer coefficient (OHTC) when burning NG and solid fuels as reburn fuels, and (2) the combustible loss through ash deposited on the surfaces of heat exchanger tubes and the bottom ash in the ash port. A new methodology is presented for determining ash-fouling behavior under transient conditions. Results on the OHTCs for solid reburn fuels are compared with the OHTCs for NG. It was found that the growth of the layer of ash depositions over longer periods typically lowers OHTC, and the increased concentration of ash in gas phase promotes radiation in high-temperature zones during initial periods while decreasing the heat transfer in low-temperature zones. The ash analyses indicated that the bottom ash in the ash port contained a smaller percentage of combustibles with a higher FB percentage in the fuels, indicating better performance compared with coal because small particles in FB burn faster and the FB has higher volatile matter on a dry ash-free basis promoting more burn out.

Durability, Performance, and Emission of Diesel Engines Using Carbon Fiber Piston and Liner

NASA Technical Reports Server (NTRS)

Afify, E. M.; Roberts, W. L.

1999-01-01

This report summarizes the research conducted by NC State University in investigating the durability, performance and emission of a carbon fiber piston and liner in our single cylinder research Diesel engine. Both the piston and liner were supplied to NC State University by NASA LaRC and manufactured by C-CAT under a separate contract to NASA LaRC. The carbon-carbon material used to manufacture the piston and liner has significantly lower thermal conductivity, coefficient of thermal expansion, and superior strength characteristics at elevated temperatures when compared to conventional piston materials such as aluminum. The results of the carbon-carbon fiber piston testing were compared to a baseline configuration, which used a conventional aluminum piston in a steel liner. The parameters measured were the brake specific fuel consumption, ignition delay, frictional horsepower, volumetric efficiency, and durability characteristics of the two pistons. Testing was performed using a naturally aspirated Labeco Direct Injection single cylinder diesel engine. Two test cases were performed over a range of loads and speeds. The fixed test condition between the aluminum and carbon-carbon piston configurations was the brake mean effective pressure. The measured data was the fuel consumption rate, volumetric efficiency, load, speed, cylinder pressure, needle lift, and exhaust gas temperature. The cylinder pressure, and fuel consumption, exhaust gas temperature, and needle lift were recorded using a National Instruments DAQ board and a PC. All test cases used Diesel no. 2 for fuel.

Fuel Breeding and Core Behavior Analyses on In Core Fuel Management of Water Cooled Thorium Reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Permana, Sidik; Department of Physics, Bandung Institute of Technology, Gedung Fisika, Jl. Ganesha 10, Bandung 40132; Sekimoto, Hiroshi

2010-12-23

Thorium fuel cycle with recycled U-233 has been widely recognized having some contributions to improve the water-cooled breeder reactor program which has been shown by a feasible area of breeding and negative void reactivity which confirms that fissile of 233U contributes to better fuel breeding and effective for obtaining negative void reactivity coefficient as the main fissile material. The present study has the objective to estimate the effect of whole core configuration as well as burnup effects to the reactor core profile by adopting two dimensional model of fuel core management. About more than 40 months of cycle period hasmore » been employed for one cycle fuel irradiation of three batches fuel system for large water cooled thorium reactors. All position of fuel arrangement contributes to the total core conversion ratio which gives conversion ratio less than unity of at the BOC and it contributes to higher than unity (1.01) at the EOC after some irradiation process. Inner part and central part give the important part of breeding contribution with increasing burnup process, while criticality is reduced with increasing the irradiation time. Feasibility of breeding capability of water-cooled thorium reactors for whole core fuel arrangement has confirmed from the obtained conversion ratio which shows higher than unity. Whole core analysis on evaluating reactivity change which is caused by the change of voided condition has been employed for conservative assumption that 100% coolant and moderator are voided. It obtained always a negative void reactivity coefficient during reactor operation which shows relatively more negative void coefficient at BOC (fresh fuel composition), and it becomes less negative void coefficient with increasing the operation time. Negative value of void reactivity coefficient shows the reactor has good safety properties in relation to the reactivity profile which is the main parameter in term of criticality safety analysis. Therefore, this evaluation has confirmed that breeding condition and negative coefficient can be obtained simultaneously for water-cooled thorium reactor obtains based on the whole core fuel arrangement.« less

High-pressure nuclear magnetic resonance studies of fuel cell membranes

NASA Astrophysics Data System (ADS)

Mananga, Eugene Stephane

This thesis focuses on the use of high pressure NMR to study transport properties in electrolyte membranes used for fuel cells. The main concern is in studying the self-diffusion coefficients of ions and molecules in membranes and solutions, which can be used to characterize electrolytes in fuel cells. For this purpose, a high-pressure fringe field NMR method to study transport properties in material systems useful for fuel cell and battery electrolytes, was designed, developed, and implemented. In this investigation, pressure is the thermodynamic variable to obtain additional information about the ionic transport process, which could yield the crucial parameter, activation volume. Most of the work involves proton NMR, with additional investigations of others nuclei, such as fluorine, phosphorus and lithium. Using the FFG method, two fuel cell membrane types (NAFION-117, SPTES), and different dilutions of phosphoric acid were investigated, as was LiTf salt in Diglyme solution, which is used as a lithium battery electrolyte. In addition to high-pressure NMR diffusion measurements carried out in the fringe field gradient for the investigation of SPTES, pulse field gradient spin echo NMR was also used to characterize the water diffusion, in addition to measuring diffusion rates as a function of temperature. This second method allows us to measure distinct diffusion coefficients in cases where the different nuclear (proton) environments can be resolved in the NMR spectrum. Polymer electrolyte systems, in which the mobility of both cations and anions is probed by NMR self-diffusion measurements using standard pulsed field gradient methods and static gradient measurements as a function of applied hydrostatic pressure, were also investigated. The material investigated is the low molecular weight liquid diglyme/LiCF3SO3 (LiTf) complexes which can be used as electrolytes in lithium batteries. Finally, high-pressure diffusion coefficient measurements of phosphoric acid in water at different concentrations: proton (1H) and phosphorus (31P) nuclei have been performed using the static field gradient spin-echo nuclear magnetic resonance. This study is expected to be helpful in improving the understanding of phosphoric acid fuel cell technology.

Analysis and Implementation of Accident Tolerant Nuclear Fuels

NASA Astrophysics Data System (ADS)

Prewitt, Benjamin Joseph

To improve the reliability and robustness of LWR, accident tolerant nuclear fuels and cladding materials are being developed to possibly replace the current UO2/zirconium system. This research highlights UN and U3Si 2, two of the most favorable accident tolerant fuels being developed. To evaluate the commercial feasiblilty of these fuels, two areas of research were conducted. Chemical fabrication routes for both fuels were investigated in detail, considering UO2 and UF6 as potential starting materials. Potential pathways for industrial scale fabrication using these methods were discussed. Neutronic performance of 70%UN-30%U3Si2 composite was evaluated in MNCP using PWR assembly and core models. The results showed comparable performance to an identical UO2 fueled simulation with the same configuration. The parameters simulated for composite and oxide fuel include the following: fuel to moderator ratio curves; energy dependent flux spectra; temperature coefficients for fuel and moderator; delayed neutron fractions; power peaking factors; axial and radial flux profiles in 2D and 3D; burnup; critical boron concentration; and shutdown margin. Overall, the neutronic parameters suggest that the transition from UO2 to composite in existing nuclear systems will not require significant changes in operating procedures or modifications to standards and regulations.

Performance of PZT stacks under high-field electric cycling at various temperatures in heavy-duty diesel engine fuel injectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hong; Lin, Hua-Tay; Stafford, Mr Randy

2016-01-01

Testing and characterization of large prototype lead zirconate titanate (PZT) stacks present substantial technical challenges to electronic systems. The work in this study shows that an alternative approach can be pursued by using subunits extracted from prototype stacks. Piezoelectric and dielectric integrity was maintained even though the PZT plate specimens experienced an additional loading process involved with the extraction after factory poling. Extracted 10-layer plate specimens were studied by an electric cycle test under an electric field of 3.0/0.0 kV/mm, 100 Hz to 108 cycles, both at room temperature (22 C) and at 50 C. The elevated temperature had amore » defined impact on the fatigue of PZT stacks. About 48 and 28% reductions were observed in the piezoelectric and dielectric coefficients, respectively, after 108 cycles at 50 C, compared with reductions of 25 and 15% in the respective coefficients at 22 C. At the same time, the loss tangent varied to a limited extent. The evolution of PZT electrode interfacial layers or nearby dielectric layers should account for the difference in the fatigue rates of piezoelectric and dielectric coefficients. But the basic contribution to observed fatigue may result from the buildup of a bias field that finally suppressed the motion of the domain walls. Finally, monitoring of dielectric coefficients can be an effective tool for on-line lifetime prediction of PZT stacks in service if a failure criterion is defined properly.« less

Performance of PZT stacks under high-field electric cycling at various temperatures in heavy-duty diesel engine fuel injectors

NASA Astrophysics Data System (ADS)

Wang, Hong; Lee, Sung-Min; Lin, Hua-Tay; Stafford, Randy

2016-04-01

Testing and characterization of large prototype lead zirconate titanate (PZT) stacks present substantial technical challenges to electronic systems. The work in this study shows that an alternative approach can be pursued by using subunits extracted from prototype stacks. Piezoelectric and dielectric integrity was maintained even though the PZT plate specimens experienced an additional loading process involved with the extraction after factory poling. Extracted 10-layer plate specimens were studied by an electric cycle test under an electric field of 3.0/0.0 kV/mm, 100 Hz to 108 cycles, both at room temperature (22°C) and at 50°C. The elevated temperature had a defined impact on the fatigue of PZT stacks. About 48 and 28% reductions were observed in the piezoelectric and dielectric coefficients, respectively, after 108 cycles at 50°C, compared with reductions of 25 and 15% in the respective coefficients at 22°C. At the same time, the loss tangent varied to a limited extent. The evolution of PZT-electrode interfacial layers or nearby dielectric layers should account for the difference in the fatigue rates of piezoelectric and dielectric coefficients. But the basic contribution to observed fatigue may result from the buildup of a bias field that finally suppressed the motion of the domain walls. Finally, monitoring of dielectric coefficients can be an effective tool for on-line lifetime prediction of PZT stacks in service if a failure criterion is defined properly.

Electro-Osmosis and Water Uptake in Polymer Electrolytes in Equilibrium with Water Vapor at Low Temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallagher, K. G.; Pivovar, B. S.; Fuller, T. F.

2009-01-01

Water uptake and electro-osmosis are investigated to improve the understanding and aid the modeling of water transport in proton-exchange membrane fuel cells (PEMFCs) below 0 C. Measurements of water sorption isotherms show a significant reduction in the water capacity of polymer electrolytes below 0 C. This reduced water content is attributed to the lower vapor pressure of ice compared to supercooled liquid water. At -25 C, 1100 equivalent weight Nafion in equilibrium with vapor over ice has 8 moles of water per sulfonic acid group. Measurements of the electro-osmotic drag coefficient for Nafion and both random and multiblock copolymer sulfonatedmore » poly(arylene ether sulfone) (BPSH) chemistries are reported for vapor equilibrated samples below 0 C. The electro-osmotic drag coefficient of BPSH chemistries is found to be {approx}0.4, and that of Nafion is {approx}1. No significant temperature effect on the drag coefficient is found. The implication of an electro-osmotic drag coefficient less than unity is discussed in terms of proton conduction mechanisms. Simulations of the ohmically limited current below 0 C show that a reduced water uptake below 0 C results in a significant decrease in PEMFC performance.« less

A high-fidelity Monte Carlo evaluation of CANDU-6 safety parameters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Y.; Hartanto, D.

2012-07-01

Important safety parameters such as the fuel temperature coefficient (FTC) and the power coefficient of reactivity (PCR) of the CANDU-6 (CANada Deuterium Uranium) reactor have been evaluated by using a modified MCNPX code. For accurate analysis of the parameters, the DBRC (Doppler Broadening Rejection Correction) scheme was implemented in MCNPX in order to account for the thermal motion of the heavy uranium nucleus in the neutron-U scattering reactions. In this work, a standard fuel lattice has been modeled and the fuel is depleted by using the MCNPX and the FTC value is evaluated for several burnup points including the mid-burnupmore » representing a near-equilibrium core. The Doppler effect has been evaluated by using several cross section libraries such as ENDF/B-VI, ENDF/B-VII, JEFF, JENDLE. The PCR value is also evaluated at mid-burnup conditions to characterize safety features of equilibrium CANDU-6 reactor. To improve the reliability of the Monte Carlo calculations, huge number of neutron histories are considered in this work and the standard deviation of the k-inf values is only 0.5{approx}1 pcm. It has been found that the FTC is significantly enhanced by accounting for the Doppler broadening of scattering resonance and the PCR are clearly improved. (authors)« less

Mechanics based model for predicting structure-induced rolling resistance (SRR) of the tire-pavement system

NASA Astrophysics Data System (ADS)

Shakiba, Maryam; Ozer, Hasan; Ziyadi, Mojtaba; Al-Qadi, Imad L.

2016-11-01

The structure-induced rolling resistance of pavements, and its impact on vehicle fuel consumption, is investigated in this study. The structural response of pavement causes additional rolling resistance and fuel consumption of vehicles through deformation of pavement and various dissipation mechanisms associated with inelastic material properties and damping. Accurate and computationally efficient models are required to capture these mechanisms and obtain realistic estimates of changes in vehicle fuel consumption. Two mechanistic-based approaches are currently used to calculate vehicle fuel consumption as related to structural rolling resistance: dissipation-induced and deflection-induced methods. The deflection-induced approach is adopted in this study, and realistic representation of pavement-vehicle interactions (PVIs) is incorporated. In addition to considering viscoelastic behavior of asphalt concrete layers, the realistic representation of PVIs in this study includes non-uniform three-dimensional tire contact stresses and dynamic analysis in pavement simulations. The effects of analysis type, tire contact stresses, pavement viscoelastic properties, pavement damping coefficients, vehicle speed, and pavement temperature are then investigated.

Measurements of the effects of thermal contact resistance on steady state heat transfer in phosphoric-acid fuel cell stack

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Alkasab, Kalil A.

1991-01-01

The influence of the thermal contact resistance on the heat transfer between the electrode plates, and the cooling system plate in a phosphoric-acid fuel-cell stack was experimentally investigated. The investigation was conducted using a set-up that simulates the operating conditions prevailing in a phosphoric acid fuel-cell stack. The fuel-cell cooling system utilized three types of coolants, water, engine oil, and air, to remove excess heat generated in the cell electrode and to maintain a reasonably uniform temperature distribution in the electrode plate. The thermal contact resistance was measured as a function of pressure at the interface between the electrode plate and the cooling system plate. The interface pressure range was from 0 kPa to 3448 kPa, while the Reynolds number for the cooling limits varied from 15 to 79 for oil, 1165 to 6165 for water, and 700 to 6864 for air. Results showed that increasing the interface pressure resulted in a higher heat transfer coefficient.

Non-isothermal two-phase transport in the polymer electrolyte membrane fuel cell microporous layer

NASA Astrophysics Data System (ADS)

Ge, Nan

This thesis investigates the water transport mechanisms in the crack-free microporous layer (MPL) of a polymer electrolyte membrane (PEM) fuel cell. Synchrotron X-ray radiography was used to visualize and quantify the in situ liquid water in the gas diffusion layers (GDLs) of an operating fuel cell. A methodology was developed to correct the artefact of imaging sample movement. Furthermore, to address inaccuracies due to the scattering effect and higher harmonics at the synchrotron beamline, a calibration technique was introduced in order to experimentally determine the liquid water X-ray attenuation coefficient. Through in situ radiography, liquid water breakthrough events were observed in the MPL, and measured water thicknesses were used as inputs into a one-dimensional (1D) heat and mass transport model. The 1D model was used to describe the coupled relationship between liquid and vapour transport through the cathode MPL and the temperature distributions in the operating fuel cell.

BISON Modeling of Reactivity-Initiated Accident Experiments in a Static Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Folsom, Charles P.; Jensen, Colby B.; Williamson, Richard L.

2016-09-01

In conjunction with the restart of the TREAT reactor and the design of test vehicles, modeling and simulation efforts are being used to model the response of Accident Tolerant Fuel (ATF) concepts under reactivity insertion accident (RIA) conditions. The purpose of this work is to model a baseline case of a 10 cm long UO2-Zircaloy fuel rodlet using BISON and RELAP5 over a range of energy depositions and with varying reactor power pulse widths. The results show the effect of varying the pulse width and energy deposition on both thermal and mechanical parameters that are important for predicting failure ofmore » the fuel rodlet. The combined BISON/RELAP5 model captures coupled thermal and mechanical effects on the fuel-to-cladding gap conductance, cladding-to-coolant heat transfer coefficient and water temperature and pressure that would not be capable in each code individually. These combined effects allow for a more accurate modeling of the thermal and mechanical response in the fuel rodlet and thermal-hydraulics of the test vehicle.« less

Simplified Two-Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydorgen/Oxygen

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2005-01-01

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two-time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (> 1 x 10(exp -20) moles/cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T4). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/air fuel and for the H2/O2. A similar correlation is also developed using data from NASA s Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T4) as a function of overall fuel/air ratio, pressure and initial temperature (T3). High values of the regression coefficient R2 are obtained.

Summary of Simplified Two Time Step Method for Calculating Combustion Rates and Nitrogen Oxide Emissions for Hydrogen/Air and Hydrogen/Oxygen

NASA Technical Reports Server (NTRS)

Marek, C. John; Molnar, Melissa

2005-01-01

A simplified single rate expression for hydrogen combustion and nitrogen oxide production was developed. Detailed kinetics are predicted for the chemical kinetic times using the complete chemical mechanism over the entire operating space. These times are then correlated to the reactor conditions using an exponential fit. Simple first order reaction expressions are then used to find the conversion in the reactor. The method uses a two time step kinetic scheme. The first time averaged step is used at the initial times with smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, temperature, and pressure. The second instantaneous step is used at higher water concentrations (greater than l x 10(exp -20)) moles per cc) in the mixture which gives the chemical kinetic time as a function of the instantaneous fuel and water mole concentrations, pressure and temperature (T(sub 4)). The simple correlations are then compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. This time is regressed over the complete initial conditions using the Excel regression routine. Chemical kinetic time equations for H2 and NOx are obtained for H2/Air fuel and for H2/O2. A similar correlation is also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium temperature (T(sub 4)) as a function of overall fuel/air ratio, pressure and initial temperature (T(sub 3)). High values of the regression coefficient R squared are obtained.

Combustion Characteristics in a Non-Premixed Cool-Flame Regime of n-Heptane in Microgravity

NASA Technical Reports Server (NTRS)

Takahashi, Fumiaki; Katta, Viswanath R.; Hicks, Michael C.

2015-01-01

A series of distinct phenomena have recently been observed in single-fuel-droplet combustion tests performed on the International Space Station (ISS). This study attempts to simulate the observed flame behavior numerically using a gaseous n-heptane fuel source in zero gravity and a time-dependent axisymmetric (2D) code, which includes a detailed reaction mechanism (127 species and 1130 reactions), diffusive transport, and a radiation model (for CH4, CO, CO2, H2O, and soot). The calculated combustion characteristics depend strongly on the air velocity around the fuel source. In a near-quiescent air environment (< or = 2 mm/s), with a sufficiently large fuel injection velocity (1 cm/s), a growing spherical diffusion flame extinguishes at ˜1200 K due to radiative heat losses. This is typically followed by a transition to the low-temperature (cool-flame) regime with a reaction zone (at ˜700 K) in close proximity to the fuel source. The 'cool flame' regime is formed due to the negative temperature coefficient in the low-temperature chemistry. After a relatively long period (˜18 s) of the cool flame regime, a flash re-ignition occurs, associated with flame-edge propagation and subsequent extinction of the re-ignited flame. In a low-speed (˜3 mm/s) airstream (which simulates the slight droplet movement), the diffusion flame is enhanced upstream and experiences a local extinction downstream at ˜1200 K, followed by steady flame pulsations (˜0.4 Hz). At higher air velocities (4-10 mm/s), the locally extinguished flame becomes steady state. The present axisymmetric computational approach helps in revealing the non-premixed 'cool flame' structure and 2D flame-flow interactions observed in recent microgravity droplet combustion experiments.

Performance and operational improvements made to the Waukesha AT27-GL engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinbold, E.O.

1996-12-31

This paper presents the results of combustion and engine performance studies performed on the AT27GL lean burn engine. One study was to evaluate the effect of the pre-combustion chamber cup geometry on engine performance under several operating conditions including: Air-Fuel Ratio (AFR), ignition timing, and engine load. The study examined several combustion parameters; including IMEP, coefficient of variation of IMEP, heat release rates, and maximum combustion pressures. The study also examined engine thermal efficiency, and brake specific emissions of Oxides of Nitrogen, Carbon Monoxide, and Total Hydrocarbons (gaseous). Studies were also performed on different spark plug designs, comparing firing voltages,more » and electrode temperatures while operating under conditions of varying AFR, and ignition timing. In addition an Air-Fuel-Ratio controller was recently tested and released on the engine. The controller was tested under conditions of varying fuel quality, along with a detonation control system.« less

An improved heat transfer configuration for a solid-core nuclear thermal rocket engine

NASA Technical Reports Server (NTRS)

Clark, John S.; Walton, James T.; Mcguire, Melissa L.

1992-01-01

Interrupted flow, impingement cooling, and axial power distribution are employed to enhance the heat-transfer configuration of a solid-core nuclear thermal rocket engine. Impingement cooling is introduced to increase the local heat-transfer coefficients between the reactor material and the coolants. Increased fuel loading is used at the inlet end of the reactor to enhance heat-transfer capability where the temperature differences are the greatest. A thermal-hydraulics computer program for an unfueled NERVA reactor core is employed to analyze the proposed configuration with attention given to uniform fuel loading, number of channels through the impingement wafers, fuel-element length, mass-flow rate, and wafer gap. The impingement wafer concept (IWC) is shown to have heat-transfer characteristics that are better than those of the NERVA-derived reactor at 2500 K. The IWC concept is argued to be an effective heat-transfer configuration for solid-core nuclear thermal rocket engines.

Impact of the electric compressor for automotive air conditioning system on fuel consumption and performance analysis

NASA Astrophysics Data System (ADS)

Zulkifli, A. A.; Dahlan, A. A.; Zulkifli, A. H.; Nasution, H.; Aziz, A. A.; Perang, M. R. M.; Jamil, H. M.; Misseri, M. N.

2015-12-01

Air conditioning system is the biggest auxiliary load in a vehicle where the compressor consumed the largest. Problem with conventional compressor is the cooling capacity cannot be control directly to fulfill the demand of thermal load inside vehicle cabin. This study is conducted experimentally to analyze the difference of fuel usage and air conditioning performance between conventional compressor and electric compressor of the air conditioning system in automobile. The electric compressor is powered by the car battery in non-electric vehicle which the alternator will recharge the battery. The car is setup on a roller dynamometer and the vehicle speed is varied at 0, 30, 60, 90 and 110 km/h at cabin temperature of 25°C and internal heat load of 100 and 400 Watt. The results shows electric compressor has better fuel consumption and coefficient of performance compared to the conventional compressor.

Oxygen diffusion model of the mixed (U,Pu)O2 ± x: Assessment and application

NASA Astrophysics Data System (ADS)

Moore, Emily; Guéneau, Christine; Crocombette, Jean-Paul

2017-03-01

The uranium-plutonium (U,Pu)O2 ± x mixed oxide (MOX) is used as a nuclear fuel in some light water reactors and considered for future reactor generations. To gain insight into fuel restructuring, which occurs during the fuel lifetime as well as possible accident scenarios understanding of the thermodynamic and kinetic behavior is crucial. A comprehensive evaluation of thermo-kinetic properties is incorporated in a computational CALPHAD type model. The present DICTRA based model describes oxygen diffusion across the whole range of plutonium, uranium and oxygen compositions and temperatures by incorporating vacancy and interstitial migration pathways for oxygen. The self and chemical diffusion coefficients are assessed for the binary UO2 ± x and PuO2 - x systems and the description is extended to the ternary mixed oxide (U,Pu)O2 ± x by extrapolation. A simulation to validate the applicability of this model is considered.

Development of burnup dependent fuel rod model in COBRA-TF

NASA Astrophysics Data System (ADS)

Yilmaz, Mine Ozdemir

The purpose of this research was to develop a burnup dependent fuel thermal conductivity model within Pennsylvania State University, Reactor Dynamics and Fuel Management Group (RDFMG) version of the subchannel thermal-hydraulics code COBRA-TF (CTF). The model takes into account first, the degradation of fuel thermal conductivity with high burnup; and second, the fuel thermal conductivity dependence on the Gadolinium content for both UO2 and MOX fuel rods. The modified Nuclear Fuel Industries (NFI) model for UO2 fuel rods and Duriez/Modified NFI Model for MOX fuel rods were incorporated into CTF and fuel centerline predictions were compared against Halden experimental test data and FRAPCON-3.4 predictions to validate the burnup dependent fuel thermal conductivity model in CTF. Experimental test cases from Halden reactor fuel rods for UO2 fuel rods at Beginning of Life (BOL), through lifetime without Gd2O3 and through lifetime with Gd 2O3 and a MOX fuel rod were simulated with CTF. Since test fuel rod and FRAPCON-3.4 results were based on single rod measurements, CTF was run for a single fuel rod surrounded with a single channel configuration. Input decks for CTF were developed for one fuel rod located at the center of a subchannel (rod-centered subchannel approach). Fuel centerline temperatures predicted by CTF were compared against the measurements from Halden experimental test data and the predictions from FRAPCON-3.4. After implementing the new fuel thermal conductivity model in CTF and validating the model with experimental data, CTF model was applied to steady state and transient calculations. 4x4 PWR fuel bundle configuration from Purdue MOX benchmark was used to apply the new model for steady state and transient calculations. First, one of each high burnup UO2 and MOX fuel rods from 4x4 matrix were selected to carry out single fuel rod calculations and fuel centerline temperatures predicted by CTF/TORT-TD were compared against CTF /TORT-TD /FRAPTRAN predictions. After confirming that the new fuel thermal conductivity model in CTF worked and provided consistent results with FRAPTRAN predictions for a single fuel rod configuration, the same type of analysis was carried out for a bigger system which is the 4x4 PWR bundle consisting of 15 fuel pins and one control guide tube. Steady- state calculations at Hot Full Power (HFP) conditions for control guide tube out (unrodded) were performed using the 4x4 PWR array with CTF/TORT-TD coupled code system. Fuel centerline, surface and average temperatures predicted by CTF/TORT-TD with and without the new fuel thermal conductivity model were compared against CTF/TORT-TD/FRAPTRAN predictions to demonstrate the improvement in fuel centerline predictions when new model was used. In addition to that constant and CTF dynamic gap conductance model were used with the new thermal conductivity model to show the performance of the CTF dynamic gap conductance model and its impact on fuel centerline and surface temperatures. Finally, a Rod Ejection Accident (REA) scenario using the same 4x4 PWR array was run both at Hot Zero Power (HZP) and Hot Full Power (HFP) condition, starting at a position where half of the control rod is inserted. This scenario was run using CTF/TORT-TD coupled code system with and without the new fuel thermal conductivity model. The purpose of this transient analysis was to show the impact of thermal conductivity degradation (TCD) on feedback effects, specifically Doppler Reactivity Coefficient (DRC) and, eventually, total core reactivity.

Theoretical Rocket Performance of Liquid Methane with Several Fluorine-Oxygen Mixtures Assuming Frozen Composition

NASA Technical Reports Server (NTRS)

Gordon, Sanford; Kastner, Michael E

1958-01-01

Theoretical rocket performance for frozen composition during expansion was calculated for liquid methane with several fluorine-oxygen mixtures for a range of pressure ratios and oxidant-fuel ratios. The parameters included are specific impulse, combustion-chamber temperature, nozzle-exit temperature molecular weight, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, isentropic exponent, viscosity, and thermal conductivity. The maximum calculated value of specific impulse for a chamber pressure of 600 pounds per square inch absolute (40.827atm) and an exit pressure of 1 atmosphere is 315.3 for 79.67 percent fluorine in the oxidant.

A comprehensive iso-octane combustion model with improved thermochemistry and chemical kinetics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atef, Nour; Kukkadapu, Goutham; Mohamed, Samah Y.

Iso-Octane (2,2,4-trimethylpentane) is a primary reference fuel and an important component of gasoline fuels. Furthermore, it is a key component used in surrogates to study the ignition and burning characteristics of gasoline fuels. This paper presents an updated chemical kinetic model for iso-octane combustion. Specifically, the thermodynamic data and reaction kinetics of iso-octane have been re-assessed based on new thermodynamic group values and recently evaluated rate coefficients from the literature. The adopted rate coefficients were either experimentally measured or determined by analogy to theoretically calculated values. New alternative isomerization pathways for peroxy-alkyl hydroperoxide (more » $$\\dot{O}$$OQOOH) radicals were added to the reaction mechanism. The updated kinetic model was compared against new ignition delay data measured in rapid compression machines (RCM) and a high-pressure shock tube. Our experiments were conducted at pressures of 20 and 40 atm, at equivalence ratios of 0.4 and 1.0, and at temperatures in the range of 632–1060 K. The updated model was further compared against shock tube ignition delay times, jet-stirred reactor oxidation speciation data, premixed laminar flame speeds, counterflow diffusion flame ignition, and shock tube pyrolysis speciation data available in the literature. Finally, the updated model was used to investigate the importance of alternative isomerization pathways in the low temperature oxidation of highly branched alkanes. When compared to available models in the literature, the present model represents the current state-of-the-art in fundamental thermochemistry and reaction kinetics of iso-octane; and thus provides the best prediction of wide ranging experimental data and fundamental insights into iso-octane combustion chemistry.« less

A comprehensive iso-octane combustion model with improved thermochemistry and chemical kinetics

DOE PAGES

Atef, Nour; Kukkadapu, Goutham; Mohamed, Samah Y.; ...

2017-02-05

Iso-Octane (2,2,4-trimethylpentane) is a primary reference fuel and an important component of gasoline fuels. Furthermore, it is a key component used in surrogates to study the ignition and burning characteristics of gasoline fuels. This paper presents an updated chemical kinetic model for iso-octane combustion. Specifically, the thermodynamic data and reaction kinetics of iso-octane have been re-assessed based on new thermodynamic group values and recently evaluated rate coefficients from the literature. The adopted rate coefficients were either experimentally measured or determined by analogy to theoretically calculated values. New alternative isomerization pathways for peroxy-alkyl hydroperoxide (more » $$\\dot{O}$$OQOOH) radicals were added to the reaction mechanism. The updated kinetic model was compared against new ignition delay data measured in rapid compression machines (RCM) and a high-pressure shock tube. Our experiments were conducted at pressures of 20 and 40 atm, at equivalence ratios of 0.4 and 1.0, and at temperatures in the range of 632–1060 K. The updated model was further compared against shock tube ignition delay times, jet-stirred reactor oxidation speciation data, premixed laminar flame speeds, counterflow diffusion flame ignition, and shock tube pyrolysis speciation data available in the literature. Finally, the updated model was used to investigate the importance of alternative isomerization pathways in the low temperature oxidation of highly branched alkanes. When compared to available models in the literature, the present model represents the current state-of-the-art in fundamental thermochemistry and reaction kinetics of iso-octane; and thus provides the best prediction of wide ranging experimental data and fundamental insights into iso-octane combustion chemistry.« less

Why do proton conducting polybenzimidazole phosphoric acid membranes perform well in high-temperature PEM fuel cells?

PubMed

Melchior, Jan-Patrick; Majer, Günter; Kreuer, Klaus-Dieter

2016-12-21

Transport properties and hydration behavior of phosphoric acid/(benz)imidazole mixtures are investigated by diverse NMR techniques, thermogravimetric analysis (TGA) and conductivity measurements. The monomeric systems can serve as models for phosphoric acid/poly-benzimidazole membranes which are known for their exceptional performance in high temperature PEM fuel cells. 1 H- and 31 P-NMR data show benzimidazole acting as a strong Brønsted base with respect to neat phosphoric acid. Since benzimidazole's nitrogens are fully protonated with a low rate for proton exchange with phosphate species, proton diffusion and conduction processes must take place within the hydrogen bond network of phosphoric acid only. The proton exchange dynamics between phosphate and benzimidazole species pass through the intermediate exchange regime (with respect to NMR line separations) with exchange times being close to typical diffusion times chosen in PFG-NMR diffusion measurements (ms regime). The resulting effects, as described by the Kärger equation, are included into the evaluation of PFG-NMR data for obtaining precise proton diffusion coefficients. The highly reduced proton diffusion coefficient within the phosphoric acid part of the model systems compared to neat phosphoric acid is suggested to be the immediate consequence of proton subtraction from phosphoric acid. This reduces hydrogen bond network frustration (imbalance of the number of proton donors and acceptors) and therefore also the rate of structural proton diffusion, phosphoric acid's acidity and hygroscopicity. Reduced water uptake, shown by TGA, goes along with reduced electroosmotic water drag which is suggested to be the reason for PBI-phosphoric acid membranes performing better in fuel cells than other phosphoric-acid-containing electrolytes with higher protonic conductivity.

Performance evaluation of Mn and Fe doped SrCo0.9Nb0.1O3-δ cathode for IT-SOFC application

NASA Astrophysics Data System (ADS)

Bele, Lokesh; Lenka, R. K.; Patro, P. K.; Muhmood, L.; Mahata, T.; Sinha, P. K.

2018-02-01

Cathode materials of Mn and Fe doped SrCo0.9Nb0.1O3-δ, are synthesized by solid state route for intermediate temperature fuel cell applications. Phase pure material is obtained after calcining the precursors at 1100 °C. Phase compatibility is observed between this novel cathode material with gadolinia doped ceria (GDC) electrolyte material as reflected in the diffraction pattern. The state of art YSZ electrolyte is not compatible with this cathode material. Average thermal expansion coefficient of the material varies between 17 to 22 X 10-6 K-1 on doping, from room temperature to 800 °C. Increase in thermal expansion coefficient is observed with Mn and Fe doping associated with the loss of oxygen from the crystal. The electrical conductivity of the cathode material decreases with Fe and Mn doping. Mn doped samples show lowest conductivity. From the symmetric cell measurement lower area specific resistance (0.16 Ω-cm2) is obtained for un-doped samples, at 850 °C. From the initial results it can be inferred that Mn/Fe doping improves neither the thermal expansion co-efficient nor the electrochemical activity.

Gas-phase rate coefficients for the OH + n-, i-, s-, and t-butanol reactions measured between 220 and 380 K: non-Arrhenius behavior and site-specific reactivity.

PubMed

McGillen, Max R; Baasandorj, Munkhbayar; Burkholder, James B

2013-06-06

Butanol (C4H9OH) is a potential biofuel alternative in fossil fuel gasoline and diesel formulations. The usage of butanol would necessarily lead to direct emissions into the atmosphere; thus, an understanding of its atmospheric processing and environmental impact is desired. Reaction with the OH radical is expected to be the predominant atmospheric removal process for the four aliphatic isomers of butanol. In this work, rate coefficients, k, for the gas-phase reaction of the n-, i-, s-, and t-butanol isomers with the OH radical were measured under pseudo-first-order conditions in OH using pulsed laser photolysis to produce OH radicals and laser induced fluorescence to monitor its temporal profile. Rate coefficients were measured over the temperature range 221-381 K at total pressures between 50 and 200 Torr (He). The reactions exhibited non-Arrhenius behavior over this temperature range and no dependence on total pressure with k(296 K) values of (9.68 ± 0.75), (9.72 ± 0.72), (8.88 ± 0.69), and (1.04 ± 0.08) (in units of 10(-12) cm(3) molecule(-1) s(-1)) for n-, i-, s-, and t-butanol, respectively. The quoted uncertainties are at the 2σ level and include estimated systematic errors. The observed non-Arrhenius behavior is interpreted here to result from a competition between the available H-atom abstraction reactive sites, which have different activation energies and pre-exponential factors. The present results are compared with results from previous kinetic studies, structure-activity relationships (SARs), and theoretical calculations and the discrepancies are discussed. Results from this work were combined with available high temperature (1200-1800 K) rate coefficient data and room temperature reaction end-product yields, where available, to derive a self-consistent site-specific set of reaction rate coefficients of the form AT(n) exp(-E/RT) for use in atmospheric and combustion chemistry modeling.

Formulations for Stronger Solid Oxide Fuel-Cell Electrolytes

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Goldsby, John C.; Choi, Sung R.

2004-01-01

Tests have shown that modification of chemical compositions can increase the strengths and fracture toughnesses of solid oxide fuel-cell (SOFC) electrolytes. Heretofore, these solid electrolytes have been made of yttria-stabilized zirconia, which is highly conductive for oxygen ions at high temperatures, as needed for operation of fuel cells. Unfortunately yttria-stabilized zirconia has a high coefficient of thermal expansion, low resistance to thermal shock, low fracture toughness, and low mechanical strength. The lack of strength and toughness are especially problematic for fabrication of thin SOFC electrolyte membranes needed for contemplated aeronautical, automotive, and stationary power-generation applications. The modifications of chemical composition that lead to increased strength and fracture toughness consist in addition of alumina to the basic yttria-stabilized zirconia formulations. Techniques for processing of yttria-stabilized zirconia/alumina composites containing as much as 30 mole percent of alumina have been developed. The composite panels fabricated by these techniques have been found to be dense and free of cracks. The only material phases detected in these composites has been cubic zirconia and a alumina: this finding signifies that no undesired chemical reactions between the constituents occurred during processing at elevated temperatures. The flexural strengths and fracture toughnesses of the various zirconia-alumina composites were measured in air at room temperature as well as at a temperature of 1,000 C (a typical SOFC operating temperature). The measurements showed that both flexural strength and fracture toughness increased with increasing alumina content at both temperatures. In addition, the modulus of elasticity and the thermal conductivity were found to increase and the density to decrease with increasing alumina content. The oxygen-ion conductivity at 1,000 C was found to be unchanged by the addition of alumina.

Investigations of ash fouling with cattle wastes as reburn fuel in a small-scale boiler burner under transient conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hyukjin Oh; Kalyan Annamalai; John M. Sweeten

2008-04-15

Fouling behavior under reburn conditions was investigated with cattle wastes (termed as feedlot biomass, FB) and coal as reburn fuels under a transient condition and short-time operation. A small-scale (30 kW or 100,000 Btu/hr) boiler burner research facility was used for the reburn experiments. The fuels considered for these experiments were natural gas (NG) for the ashless case, pure coal, pure FB, and blends of coal and FB. Two parameters that were used to characterize the ash 'fouling' were (1) the overall heat-transfer coefficient (OHTC) when burning NG and solid fuels as reburn fuels, and (2) the combustible loss throughmore » ash deposited on the surfaces of heat exchanger tubes and the bottom ash in the ash port. A new methodology is presented for determining ash fouling behavior under transient conditions. Results on the OHTCs for solid reburn fuels are compared with the OHTCs for NG. It was found that the growth of the layer of ash depositions over longer periods typically lowers OHTC, and the increased concentration of ash in gas phase promotes radiation in high-temperature zones during initial periods while decreasing the heat transfer in low-temperature zones. The ash analyses indicated that the bottom ash in the ash port contained a smaller percentage of combustibles with a higher FB percentage in the fuels, indicating better performance compared with coal because small particles in FB burn faster and the FB has higher volatile matter on a dry ash-free basis promoting more burn out. 16 refs., 12 figs., 6 tabs.« less

Synthesis and characterization of La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} oxide as cathode for Intermediate Temperature Solid Oxide Fuel Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vázquez, Santiago; Davyt, Sebastián; Basbus, Juan F.

2015-08-15

Nanocrystalline La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} (LSFCu) material was synthetized by combustion method using EDTA as fuel/chelating agent and NH{sub 4}NO{sub 3} as combustion promoter. Structural characterization using thermodiffraction data allowed to determine a reversible phase transition at 425 °C from a low temperature R-3c phase to a high temperature Pm-3m phase and to calculate the thermal expansion coefficient (TEC) of both phases. Important characteristics for cathode application as electronic conductivity and chemical compatibility with Ce{sub 0.9}Gd{sub 0.1}O{sub 2−δ} (CGO) electrolyte were evaluated. LSFCu presented a p-type conductor behavior with maximum conductivity of 135 S cm{sup −1} at 275more » °C and showed a good stability with CGO electrolyte at high temperatures. This work confirmed that as prepared LSFCu has excellent microstructural characteristics and an electrical conductivity between 100 and 60 S cm{sup −1} in the 500–700 °C range which is sufficiently high to work as intermediate temperature Solid Oxide Fuel Cells (IT-SOFCs) cathode. However a change in the thermal expansion coefficient consistent with a small oxygen loss process may affect the electrode-electrolyte interface during fabrication and operation of a SOFC. - Graphical abstract: Nanocrystalline La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Cu{sub 0.2}O{sub 3−δ} was prepared by gel combustion and characterized by X-ray thermodiffraction and its conductivity was determined. The phase shows a reversible rhombohedral to cubic structural phase transition at 425 °C and a semiconductor to metallic phase transition at 275 °C. - Highlights: • LSFCu was prepared by gel combustion route using EDTA and NH{sub 4}NO{sub 3}. • LSFCu shows a reversible phase transition at 425 °C from R-3c to Pm-3m phase. • The sample has a maximum conductivity value of 135 S cm{sup −1} at 275 °C. • LSFCu shows a good chemical compatibility with CGO at 900 °C.« less

Cool-Flame Burning and Oscillations of Envelope Diffusion Flames in Microgravity

NASA Astrophysics Data System (ADS)

Takahashi, Fumiaki; Katta, Viswanath R.; Hicks, Michael C.

2018-05-01

The two-stage combustion, local extinction, and flame-edge oscillations have been observed in single-droplet combustion tests conducted on the International Space Station. To understand such dynamic behavior of initially enveloped diffusion flames in microgravity, two-dimensional (axisymmetric) computation is performed for a gaseous n-heptane flame using a time-dependent code with a detailed reaction mechanism (127 species and 1130 reactions), diffusive transport, and a simple radiation model (for CO2, H2O, CO, CH4, and soot). The calculated combustion characteristics vary profoundly with a slight movement of air surrounding a fuel source. In a near-quiescent environment (≤ 2 mm/s), with a sufficiently large fuel injection velocity (1 cm/s), extinction of a growing spherical diffusion flame due to radiative heat losses is predicted at the flame temperature at ≈ 1200 K. The radiative extinction is typically followed by a transition to the "cool flame" burning regime (due to the negative temperature coefficient in the low-temperature chemistry) with a reaction zone (at ≈ 700 K) in close proximity to the fuel source. By contrast, if there is a slight relative velocity (≈ 3 mm/s) between the fuel source and the air, a local extinction of the envelope diffusion flame is predicted downstream at ≈ 1200 K, followed by periodic flame-edge oscillations. At higher relative velocities (4 to 10 mm/s), the locally extinguished flame becomes steady state. The present 2D computational approach can help in understanding further the non-premixed "cool flame" structure and flame-flow interactions in microgravity environments.

Diffusion coefficient of hydrogen in a cast gamma titanium aluminide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sundaram, P.A.; Wessel, E.; Ennis, P.J.

1999-06-04

Gamma titanium aluminides have the potential for high temperature applications because of their high specific strength and specific modulus. Their oxidation resistance is good, especially at intermediate temperatures and with suitable alloying additions, good oxidation resistance can be obtained up to 800 C. One critical area of application is in combustion engines in aero-space vehicles such as hypersonic airplanes and high speed civil transport airplanes. This entails the use of hydrogen as a fuel component and hence the effect of hydrogen on the mechanical properties of gamma titanium aluminides is of significant scientific and technological utility. The purpose of thismore » short investigation is to use an electrochemical method under galvanostatic conditions to determine the diffusion coefficient of hydrogen in a cast gamma titanium aluminide, a typical technical alloy with potential application in gas turbines under creep conditions. This result will be then compared with that obtained by microhardness profiling of electrolytically hydrogen precharged material.« less

Performance and Thrust-to-Weight Optimization of the Dual-Expander Aerospike Nozzle Upper Stage Rocket Engine

DTIC Science & Technology

2012-06-01

calculates a constant convection heat transfer coefficient on the hot and cold side of the cooling jacket wall. The calculated maximum wall temperature for...regeneratively cools the combustion chamber and nozzle. The heat transferred to the fuel from cooling provides enough power to the turbine to power both... heat transfer at the throat compared to a bell nozzle. This increase in heat transfer surface area means more power to the turbine, increased chamber

Analysis and experimental investigation of ceramic powder coating on aluminium piston

NASA Astrophysics Data System (ADS)

Pal, S.; Deore, A.; Choudhary, A.; Madhwani, V.; Vijapuri, D.

2017-11-01

Energy conservation and efficiency have always been the quest of engineers concerned with internal combustion engines. The diesel engine generally offers better fuel economy than its counterpart petrol engine. Even the diesel engine rejects about two thirds of the heat energy of the fuel, one-third to the coolant, and one third to the exhaust, leaving only about one-third as useful power output. Theoretically if the heat rejected could be reduced, then the thermal efficiency would be improved, at least up to the limit set by the second law of thermodynamics. Low Heat Rejection engines aim to do this by reducing the heat lost to the coolant. Thermal Barrier Coatings (TBCs) in diesel engines lead to advantages including higher power density, fuel efficiency, and multifuel capacity due to higher combustion chamber temperature. Using TBC can increase engine power by 8%, decrease the specific fuel consumption by 15-20% and increase the exhaust gas temperature by 200K. Although several systems have been used as TBC for different purposes, yttria stabilized zirconia with 7-8 wt.% yttria has received the most attention. Several factors playing important role in TBC life include thermal conductivity, thermo chemical stability at the service temperature, high thermo mechanical stability to the maximum service temperature and thermal expansion coefficient (TEC). This work mainly concentrates on the behaviour of three TBC powders under the same diesel engine conditions. This work finds out the best powder among yttria, alumina and zirconia to be used as a piston coating material i.e., the one resulting in lowest heat flux and low side skirt and bottom temperature has been chosen for the coating purpose. This work then analyses the coated sample for its surface properties such as hardness, roughness, corrosion resistance and microstructural study. This work aims at making it easier for the manufacturers choose the coating material for engine coating purposes and surface properties for operating them in their service period.

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

DOE PAGES

Goldsborough, S. Scott; Hochgreb, Simone; Vanhove, Guillaume; ...

2017-07-10

Rapid compression machines (RCMs) are widely-used to acquire experimental insights into fuel autoignition and pollutant formation chemistry, especially at conditions relevant to current and future combustion technologies. RCM studies emphasize important experimental regimes, characterized by low- to intermediate-temperatures (600–1200 K) and moderate to high pressures (5–80 bar). At these conditions, which are directly relevant to modern combustion schemes including low temperature combustion (LTC) for internal combustion engines and dry low emissions (DLE) for gas turbine engines, combustion chemistry exhibits complex and experimentally challenging behaviors such as the chemistry attributed to cool flame behavior and the negative temperature coefficient regime. Challengesmore » for studying this regime include that experimental observations can be more sensitive to coupled physical-chemical processes leading to phenomena such as mixed deflagrative/autoignitive combustion. Experimental strategies which leverage the strengths of RCMs have been developed in recent years to make RCMs particularly well suited for elucidating LTC and DLE chemistry, as well as convolved physical-chemical processes. Specifically, this work presents a review of experimental and computational efforts applying RCMs to study autoignition phenomena, and the insights gained through these efforts. A brief history of RCM development is presented towards the steady improvement in design, characterization, instrumentation and data analysis. Novel experimental approaches and measurement techniques, coordinated with computational methods are described which have expanded the utility of RCMs beyond empirical studies of explosion limits to increasingly detailed understanding of autoignition chemistry and the role of physical-chemical interactions. Fundamental insight into the autoignition chemistry of specific fuels is described, demonstrating the extent of knowledge of low-temperature chemistry derived from RCM studies, from simple hydrocarbons to multi-component blends and full-boiling range fuels. In conclusion, emerging needs and further opportunities are suggested, including investigations of under-explored fuels and the implementation of increasingly higher fidelity diagnostics.« less

Advances in rapid compression machine studies of low- and intermediate-temperature autoignition phenomena

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldsborough, S. Scott; Hochgreb, Simone; Vanhove, Guillaume

Rapid compression machines (RCMs) are widely-used to acquire experimental insights into fuel autoignition and pollutant formation chemistry, especially at conditions relevant to current and future combustion technologies. RCM studies emphasize important experimental regimes, characterized by low- to intermediate-temperatures (600–1200 K) and moderate to high pressures (5–80 bar). At these conditions, which are directly relevant to modern combustion schemes including low temperature combustion (LTC) for internal combustion engines and dry low emissions (DLE) for gas turbine engines, combustion chemistry exhibits complex and experimentally challenging behaviors such as the chemistry attributed to cool flame behavior and the negative temperature coefficient regime. Challengesmore » for studying this regime include that experimental observations can be more sensitive to coupled physical-chemical processes leading to phenomena such as mixed deflagrative/autoignitive combustion. Experimental strategies which leverage the strengths of RCMs have been developed in recent years to make RCMs particularly well suited for elucidating LTC and DLE chemistry, as well as convolved physical-chemical processes. Specifically, this work presents a review of experimental and computational efforts applying RCMs to study autoignition phenomena, and the insights gained through these efforts. A brief history of RCM development is presented towards the steady improvement in design, characterization, instrumentation and data analysis. Novel experimental approaches and measurement techniques, coordinated with computational methods are described which have expanded the utility of RCMs beyond empirical studies of explosion limits to increasingly detailed understanding of autoignition chemistry and the role of physical-chemical interactions. Fundamental insight into the autoignition chemistry of specific fuels is described, demonstrating the extent of knowledge of low-temperature chemistry derived from RCM studies, from simple hydrocarbons to multi-component blends and full-boiling range fuels. In conclusion, emerging needs and further opportunities are suggested, including investigations of under-explored fuels and the implementation of increasingly higher fidelity diagnostics.« less

CHAP-2 heat-transfer analysis of the Fort St. Vrain reactor core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kotas, J.F.; Stroh, K.R.

1983-01-01

The Los Alamos National Laboratory is developing the Composite High-Temperature Gas-Cooled Reactor Analysis Program (CHAP) to provide advanced best-estimate predictions of postulated accidents in gas-cooled reactor plants. The CHAP-2 reactor-core model uses the finite-element method to initialize a two-dimensional temperature map of the Fort St. Vrain (FSV) core and its top and bottom reflectors. The code generates a finite-element mesh, initializes noding and boundary conditions, and solves the nonlinear Laplace heat equation using temperature-dependent thermal conductivities, variable coolant-channel-convection heat-transfer coefficients, and specified internal fuel and moderator heat-generation rates. This paper discusses this method and analyzes an FSV reactor-core accident thatmore » simulates a control-rod withdrawal at full power.« less

Theoretical and Experimental Flow Cell Studies of a Hydrogen-Bromine Fuel Cell, Part 1. M.S. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Savinell, R. F.; Fritts, S. D.

1986-01-01

There is increasing interest in hydrogen-bromine fuel cells as both primary and regenerative energy storage systems. One promising design for a hydrogen-bromine fuel cell is a negative half cell having only a gas phase, which is separated by a cationic exchange membrane from a positive half cell having an aqueous electrolyte. The hydrogen gas and the aqueous bromide solution are stored external to the cell. In order to calculate the energy storage capacity and to predict and assess the performance of a single cell, the open circuit potential (OCV) must be estimated for different states of change, under various conditions. Theoretical expressions were derived to estimate the OCV of a hydrogen-bromine fuel cell. In these expressions temperature, hydrogen pressure, and bromine and hydrobromic acid concentrations were taken into consideration. Also included are the effects of the Nafion membrance separator and the various bromide complex species. Activity coefficients were taken into account in one of the expressions. The sensitivity of these parameters on the calculated OCV was studied.

Analysis and design of an ultrahigh temperature hydrogen-fueled MHD generator

NASA Technical Reports Server (NTRS)

Moder, Jeffrey P.; Myrabo, Leik N.; Kaminski, Deborah A.

1993-01-01

A coupled gas dynamics/radiative heat transfer analysis of partially ionized hydrogen, in local thermodynamic equilibrium, flowing through an ultrahigh temperature (10,000-20,000 K) magnetohydrodynamic (MHD) generator is performed. Gas dynamics are modeled by a set of quasi-one-dimensional, nonlinear differential equations which account for friction, convective and radiative heat transfer, and the interaction between the ionized gas and applied magnetic field. Radiative heat transfer is modeled using nongray, absorbing-emitting 2D and 3D P-1 approximations which permit an arbitrary variation of the spectral absorption coefficient with frequency. Gas dynamics and radiative heat transfer are coupled through the energy equation and through the temperature- and density-dependent absorption coefficient. The resulting nonlinear elliptic problem is solved by iterative methods. Design of such MHD generators as onboard, open-cycle, electric power supplies for a particular advanced airbreathing propulsion concept produced an efficient and compact 128-MWe generator characterized by an extraction ratio of 35.5 percent, a power density of 10,500 MWe/cu m, and a specific (extracted) energy of 324 MJe/kg of hydrogen. The maximum wall heat flux and total wall heat load were 453 MW/sq m and 62 MW, respectively.

Determination of activity coefficient of lanthanum chloride in molten LiCl-KCl eutectic salt as a function of cesium chloride and lanthanum chloride concentrations using electromotive force measurements

NASA Astrophysics Data System (ADS)

Bagri, Prashant; Simpson, Michael F.

2016-12-01

The thermodynamic behavior of lanthanides in molten salt systems is of significant scientific interest for the spent fuel reprocessing of Generation IV reactors. In this study, the apparent standard reduction potential (apparent potential) and activity coefficient of LaCl3 were determined in a molten salt solution of eutectic LiCl-KCl as a function of concentration of LaCl3. The effect of adding up to 1.40 mol % CsCl was also investigated. These properties were determined by measuring the open circuit potential of the La-La(III) redox couple in a high temperature molten salt electrochemical cell. Both the apparent potential and activity coefficient exhibited a strong dependence on concentration. A low concentration (0.69 mol %) of CsCl had no significant effect on the measured properties, while a higher concentration (1.40 mol %) of CsCl caused an increase (become more positive) in the apparent potential and activity coefficient at the higher range of LaCl3 concentrations.

Sliding wear and friction behaviour of zircaloy-4 in water

NASA Astrophysics Data System (ADS)

Sharma, Garima; Limaye, P. K.; Jadhav, D. T.

2009-11-01

In water cooled nuclear reactors, the sliding of fuel bundles in fuel channel handling system can lead to severe wear and it is an important topic to study. In the present study, sliding wear behaviour of zircaloy-4 was investigated in water (pH ˜ 10.5) using ball-on-plate sliding wear tester. Sliding wear resistance zircaloy-4 against SS 316 was examined at room temperature. Sliding wear tests were carried out at different load and sliding frequencies. The coefficient of friction of zircaloy-4 was also measured during each tests and it was found to decrease slightly with the increase in applied load. The micro-mechanisms responsible for wear in zircaloy-4 were identified to be microcutting, micropitting and microcracking of deformed subsurface zones in water.

Evaluation of Ca3Co2O6 as cathode material for high-performance solid-oxide fuel cell

PubMed Central

Wei, Tao; Huang, Yun-Hui; Zeng, Rui; Yuan, Li-Xia; Hu, Xian-Luo; Zhang, Wu-Xing; Jiang, Long; Yang, Jun-You; Zhang, Zhao-Liang

2013-01-01

A cobalt-based thermoelectric compound Ca3Co2O6 (CCO) has been developed as new cathode material with superior performance for intermediate-temperature (IT) solid-oxide fuel cell (SOFC). Systematic evaluation has been carried out. Measurement of thermal expansion coefficient (TEC), thermal-stress (σ) and interfacial shearing stress (τ) with the electrolyte show that CCO matches well with several commonly-used IT electrolytes. Maximum power density as high as 1.47 W cm−2 is attained at 800°C, and an additional thermoelectric voltage of 11.7 mV is detected. The superior electrochemical performance, thermoelectric effect, and comparable thermal and mechanical behaviors with the electrolytes make CCO to be a promising cathode material for SOFC. PMID:23350032

Doppler Temperature Coefficient Calculations Using Adjoint-Weighted Tallies and Continuous Energy Cross Sections in MCNP6

NASA Astrophysics Data System (ADS)

Gonzales, Matthew Alejandro

The calculation of the thermal neutron Doppler temperature reactivity feedback co-efficient, a key parameter in the design and safe operation of advanced reactors, using first order perturbation theory in continuous energy Monte Carlo codes is challenging as the continuous energy adjoint flux is not readily available. Traditional approaches of obtaining the adjoint flux attempt to invert the random walk process as well as require data corresponding to all temperatures and their respective temperature derivatives within the system in order to accurately calculate the Doppler temperature feedback. A new method has been developed using adjoint-weighted tallies and On-The-Fly (OTF) generated continuous energy cross sections within the Monte Carlo N-Particle (MCNP6) transport code. The adjoint-weighted tallies are generated during the continuous energy k-eigenvalue Monte Carlo calculation. The weighting is based upon the iterated fission probability interpretation of the adjoint flux, which is the steady state population in a critical nuclear reactor caused by a neutron introduced at that point in phase space. The adjoint-weighted tallies are produced in a forward calculation and do not require an inversion of the random walk. The OTF cross section database uses a high order functional expansion between points on a user-defined energy-temperature mesh in which the coefficients with respect to a polynomial fitting in temperature are stored. The coefficients of the fits are generated before run- time and called upon during the simulation to produce cross sections at any given energy and temperature. The polynomial form of the OTF cross sections allows the possibility of obtaining temperature derivatives of the cross sections on-the-fly. The use of Monte Carlo sampling of adjoint-weighted tallies and the capability of computing derivatives of continuous energy cross sections with respect to temperature are used to calculate the Doppler temperature coefficient in a research version of MCNP6. Temperature feedback results from the cross sections themselves, changes in the probability density functions, as well as changes in the density of the materials. The focus of this work is specific to the Doppler temperature feedback which result from Doppler broadening of cross sections as well as changes in the probability density function within the scattering kernel. This method is compared against published results using Mosteller's numerical benchmark to show accurate evaluations of the Doppler temperature coefficient, fuel assembly calculations, and a benchmark solution based on the heavy gas model for free-gas elastic scattering. An infinite medium benchmark for neutron free gas elastic scattering for large scattering ratios and constant absorption cross section has been developed using the heavy gas model. An exact closed form solution for the neutron energy spectrum is obtained in terms of the confluent hypergeometric function and compared against spectra for the free gas scattering model in MCNP6. Results show a quick increase in convergence of the analytic energy spectrum to the MCNP6 code with increasing target size, showing absolute relative differences of less than 5% for neutrons scattering with carbon. The analytic solution has been generalized to accommodate piecewise constant in energy absorption cross section to produce temperature feedback. Results reinforce the constraints in which heavy gas theory may be applied resulting in a significant target size to accommodate increasing cross section structure. The energy dependent piecewise constant cross section heavy gas model was used to produce a benchmark calculation of the Doppler temperature coefficient to show accurate calculations when using the adjoint-weighted method. Results show the Doppler temperature coefficient using adjoint weighting and cross section derivatives accurately obtains the correct solution within statistics as well as reduce computer runtimes by a factor of 50.

Characteristics of Subfreezing Operation of Polymer Electrolyte Membrane Fuel Cells

NASA Astrophysics Data System (ADS)

Mishler, Jeffrey Harris

Polymer Electrolyte Membrane (PEM) Fuel Cells are capable of high efficiency operation, and are free of NOx, SOx, and CO2 emissions when using hydrogen fuel, and ideally suited for use in transportation applications due to their high power density and low operating temperatures. However, under subfreezing conditions which may be encountered during winter seasons in some areas, product water will freeze within the membrane, cathode side catalyst layer and gas diffusion media, leading to voltage loss and operation failure. Experiments were undertaken in order to characterize the amount and location of water during fuel cell operation. First, in-situ neutron radiography was undertaken on the fuel cells at a normal operating temperature for various operating current densities, inlet relative humidities, and diffusion media hydrophobicities. It was found that more hydrophobic cathode microporous layer (MPL) or hydrophilic anode MPL may result in a larger amount of water transporting back to the anode. The water profiles along the channels were measured and the point of liquid water emergence, where two phase flow begins, was compared to previous models. Secondly, under subfreezing temperatures, neutron imaging showed that water ice product accumulates because of lack of a water removal mechanism. Water was observed under both the lands and channels, and increased almost linearly with time. It is found that most ice exists in the cathode side. With evidence from experimental observation, a cold start model was developed and explained, following existing approaches in the literature. Three stages of cold start are explained: membrane saturation, ice storage in catalyst layer pores, and then ice melting. The voltage losses due to temperature change, increased transport resistance, and reduced electrochemical surface area. The ionic conductivity of the membrane at subfreezing temperatures was modeled. Voltage evolution over time for isothermal cold starts was predicted and validated against experimental data. The ice coverage coefficient was shown to be a key variable in matching with experimental data. From model analysis, it appears that the coulombs of charge passed before operation failure is an important parameter characterizing PEM fuel cell cold start. To investigate the coulombs of charge and its determining factors, PEM fuel cells were constructed to measure the effects of membrane configuration (thickness and initial state), catalyst layer configuration (thickness and ionomer-carbon ratio), current density, and temperature on the quantity. It was found that subfreezing temperature, ionomer-catalyst ratio, and catalyst-layer thickness significantly affect the amount of charge transferred before operational failure, whereas the membrane thickness and initial hydration level have limited effect for the considered cases. In addition, degradation of the catalyst layer was observed and quantified. These results improve the fundamental understanding of characteristics of subfreezing operation and thus are valuable for automobile applications of PEM fuel cells. The model directly relates the material properties to voltage loss, and predicts voltage evolution, thus providing a way for material optimization and diagnostics. Additionally, insights into component design and operating conditions can be used to better optimize the fuel cell for cold start-up of the vehicle.

Investigation of polycyclic aromatic hydrocarbon content in fly ash and bottom ash of biomass incineration plants in relation to the operating temperature and unburned carbon content.

PubMed

Košnář, Zdeněk; Mercl, Filip; Perná, Ivana; Tlustoš, Pavel

2016-09-01

The use of biomass fuels in incineration power plants is increasing worldwide. The produced ashes may pose a serious threat to the environment due to the presence of polycyclic aromatic hydrocarbons (PAHs), because some PAHs are potent carcinogens, mutagens and teratogens. The objective of this study was to investigate the content of total and individual PAHs in fly and bottom ash derived from incineration of phytomass and dendromass, because the data on PAH content in biomass ashes is limited. Various operating temperatures of incineration were examined and the relationship between total PAH content and unburned carbon in ashes was also considered. The analysis of PAHs was carried out in fly and bottom ash samples collected from various biomass incineration plants. PAH determination was performed using gas chromatography coupled with mass spectrometry. The correlations between the low, medium and high molecular weight PAHs and each other in ashes were conducted. The relationship between PAH content and unburned carbon, determined as a loss on ignition (L.O.I.) in biomass ashes, was performed using regression analysis. The PAH content in biomass ashes varied from 41.1±1.8 to 53,800.9±13,818.4ng/g dw. This variation may be explained by the differences in boiler operating conditions and biomass fuel composition. The correlation coefficients for PAHs in ash ranged from 0.8025 to 0.9790. The regression models were designed and the coefficients of determination varied from 0.908 to 0.980. The PAH content in ash varied widely with fuel type and the effect of operating temperature on PAH content in ash was evident. Fly ashes contained higher amounts of PAHs than bottom ashes. The low molecular weight PAHs prevailed in tested ashes. The exponential relationship between the PAH content and L.O.I. for fly ashes and the linear for bottom ashes was observed. Copyright © 2016 Elsevier B.V. All rights reserved.

Estimating the neutrally buoyant energy density of a Rankine-cycle/fuel-cell underwater propulsion system

NASA Astrophysics Data System (ADS)

Waters, Daniel F.; Cadou, Christopher P.

2014-02-01

A unique requirement of underwater vehicles' power/energy systems is that they remain neutrally buoyant over the course of a mission. Previous work published in the Journal of Power Sources reported gross as opposed to neutrally-buoyant energy densities of an integrated solid oxide fuel cell/Rankine-cycle based power system based on the exothermic reaction of aluminum with seawater. This paper corrects this shortcoming by presenting a model for estimating system mass and using it to update the key findings of the original paper in the context of the neutral buoyancy requirement. It also presents an expanded sensitivity analysis to illustrate the influence of various design and modeling assumptions. While energy density is very sensitive to turbine efficiency (sensitivity coefficient in excess of 0.60), it is relatively insensitive to all other major design parameters (sensitivity coefficients < 0.15) like compressor efficiency, inlet water temperature, scaling methodology, etc. The neutral buoyancy requirement introduces a significant (∼15%) energy density penalty but overall the system still appears to offer factors of five to eight improvements in energy density (i.e., vehicle range/endurance) over present battery-based technologies.

Dynamic Response Testing in an Electrically Heated Reactor Test Facility

NASA Astrophysics Data System (ADS)

Bragg-Sitton, Shannon M.; Morton, T. J.

2006-01-01

Non-nuclear testing can be a valuable tool in the development of a space nuclear power or propulsion system. In a non-nuclear test bed, electric heaters are used to simulate the heat from nuclear fuel. Standard testing allows one to fully assess thermal, heat transfer, and stress related attributes of a given system, but fails to demonstrate the dynamic response that would be present in an integrated, fueled reactor system. The integration of thermal hydraulic hardware tests with simulated neutronic response provides a bridge between electrically heated testing and fueled nuclear testing. By implementing a neutronic response model to simulate the dynamic response that would be expected in a fueled reactor system, one can better understand system integration issues, characterize integrated system response times and response characteristics, and assess potential design improvements at a relatively small fiscal investment. Initial system dynamic response testing was demonstrated on the integrated SAFE-100a heat pipe (HP) cooled, electrically heated reactor and heat exchanger hardware, utilizing a one-group solution to the point kinetics equations to simulate the expected neutronic response of the system. Reactivity feedback calculations were then based on a bulk reactivity feedback coefficient and measured average core temperature. This paper presents preliminary results from similar dynamic testing of a direct drive gas cooled reactor system (DDG), demonstrating the applicability of the testing methodology to any reactor type and demonstrating the variation in system response characteristics in different reactor concepts. Although the HP and DDG designs both utilize a fast spectrum reactor, the method of cooling the reactor differs significantly, leading to a variable system response that can be demonstrated and assessed in a non-nuclear test facility. Planned system upgrades to allow implementation of higher fidelity dynamic testing are also discussed. Proposed DDG testing will utilize a higher fidelity point kinetics model to control core power transients, and reactivity feedback will be based on localized feedback coefficients and several independent temperature measurements taken within the core block. This paper presents preliminary test results and discusses the methodology that will be implemented in follow-on DDG testing and the additional instrumentation required to implement high fidelity dynamic testing.

Internal Nozzle Flow Simulations of Gasoline-Like Fuels under Diesel Operating Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Torelli, R.; Som, S.; Pei, Y.

Spray formation in internal combustion engines with direct injection is strictly correlated with internal nozzle flow characteristics, which are in turn influenced by fuel physical properties and injector needle motion. This paper pre-sents a series of 3D simulations that model the in-nozzle flow in a 5-hole mini-sac diesel injector. Two gasoline-like naphtha fuels, namely full-range and light naphtha, were tested under operating conditions typical of diesel applica-tions and were compared with n-dodecane, selected from a palette used as diesel surrogates. Validated methodolo-gies from our previous work were employed to account for realistic needle motion. The multi-phase nature of the problemmore » was described by the mixture model assumption with the Volume of Fluid method. Cavitation effects were included by means of the Homogeneous Relaxation Model and turbulence closure was achieved with the Standard k-ε model in an Unsteady Reynolds-Averaged Navier-Stokes formulation. The results revealed that injector perfor-mance and propensity to cavitation are influenced by the fuel properties. Analyses of several physical quantities were carried out to highlight the fuel-to-fuel differences in terms of mass flow rate, discharge coefficients, and fuel vapor volume fraction inside the orifices. A series of parametric investigations was also performed to assess the fuel response to varied fuel injection temperature, injection pressure, and cross-sectional orifice area. For all cases, the strict correlation between cavitation magnitude and saturation pressure was confirmed. Owing to their higher volatil-ity, the two gasoline-like fuels were characterized by higher cavitation across all the simulated conditions. Occur-rence of cavitation was mostly found at the needle seat and at the orifice inlets during the injection event’s transient, when very small gaps exist between the needle and its seat. This behavior tended to disappear at maximum needle lift, where cavitation was absent for all fuels. Differences in mass flow rate between the naphtha fuels and n-dodecane were measured and ascribed to the different densities of the three fuels. Nevertheless, they were found to be smaller than expected, owing to the lower viscosity of the gasoline-like fuels. This beneficial influence of the lower viscosity was shown to be less effective at higher temperature, where the relative viscosity differences de-creased.« less

Measuring Thermal Conductivity and Moisture Absorption of Cryo-Insulation Materials

NASA Technical Reports Server (NTRS)

Lambert, Michael A.

1998-01-01

NASA is seeking to develop thermal insulation material systems suitable for withstanding both extremely high temperatures encountered during atmospheric re-entry heating and aero- braking maneuvers, as well as extremely low temperatures existing in liquid fuel storage tanks. Currently, materials used for the high temperature insulation or Thermal Protection System (TPS) are different from the low temperature, or cryogenic insulation. Dual purpose materials are necessary to the development of reusable launch vehicles (RLV). The present Space Shuttle (or Space Transportation System, STS) employs TPS materials on the orbiter and cryo-insulation materials on the large fuel tank slung under the orbiter. The expensive fuel tank is jettisoned just before orbit is achieved and it burns up while re-entering over the Indian Ocean. A truly completely reusable launch vehicle must store aR cryogenic fuel internally. The fuel tanks will be located close to the outer surface. In fact the outer skin of the craft will probably also serve as the fuel tank enclosure, as in jet airliners. During a normal launch the combined TPS/cryo-insulation system will serve only as a low temperature insulator, since aerodynamic heating is relatively minimal during ascent to orbit. During re-entry, the combined TPS/cryo-insulation system will serve only as a high temperature insulator, since all the cryogenic fuel will have been expended in orbit. However, in the event of an.aborted launch or a forced/emergency early re-entry, the tanks will still contain fuel, and the TPS/cryo-insulation will have to serve as both low and high temperature insulation. Also, on long duration missions, such as to Mars, very effective cryo-insulation materials are needed to reduce bod off of liquid propellants, thereby reducing necessary tankage volume, weight, and cost. The conventional approach to obtaining both low and high temperature insulation, such as is employed for the X-33 and X-34 spacecraft, is to use separate TPS and cryo-insulation materials, which are connected by means of adhesives or stand-offs (spacers). Three concepts are being considered: (1) the TPS is bonded directly to the cryo-insulation which, in turn, is bonded to the exterior of the tank, (2) stand-offs are used to make a gap between the TPS and the cryo-insulation, which is bonded externally to the tank, (3) TPS is applied directly or with stand-offs to the exterior so the tank, and cryo-insulation is applied directly to the interior of the tank. Many potential problems are inherent in these approaches. For example, mismatch between coefficients of thermal expansion of the TPS and cryo-insulation, as well as aerodynamic loads, could lead to failure of the bond. Internal cryo-insulation must be prevent from entering the sump of the fuel turbo-pump. The mechanical integrity of the stand-off structure (if used) must withstand multiple missions. During ground hold (i.e., prior to launch) moisture condensation must be minimized in the gap between the cryo-insulation and the TPS. The longer term solution requires the development of a single material to act as cryo- insulation during ground hold and as TPS during re-entry. Such a material minimizes complexity and weight while improving reliability and reducing cost.

Neutronics Analyses of the Minimum Original HEU TREAT Core

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kontogeorgakos, D.; Connaway, H.; Yesilyurt, G.

2014-04-01

This work was performed to support the feasibility study on the potential conversion of the Transient Reactor Test Facility (TREAT) at Idaho National Laboratory from the use of high-enriched uranium (HEU) fuel to the use of low-enriched uranium (LEU) fuel. The analyses were performed by the GTRI Reactor Conversion staff at the Argonne National Laboratory (ANL). The objective of this study was to validate the MCNP model of the TREAT reactor with the well-documented measurements which were taken during the start-up and early operation of TREAT. Furthermore, the effect of carbon graphitization was also addressed. The graphitization level was assumedmore » to be 100% (ANL/GTRI/TM-13/4). For this purpose, a set of experiments was chosen to validate the TREAT MCNP model, involving the approach to criticality procedure, in-core neutron flux measurements with foils, and isothermal temperature coefficient and temperature distribution measurements. The results of this study extended the knowledge base for the TREAT MCNP calculations and established the credibility of the MCNP model to be used in the core conversion feasibility analysis.« less

The oxidation resistance optimization of titanium carbide/hastelloy (Ni-based alloy) composites applied for intermediate-temperature solid oxide fuel cell interconnects

NASA Astrophysics Data System (ADS)

Qi, Qian; Liu, Yan; Wang, Lujie; Huang, Jian; Xin, Xianshuang; Gai, Linlin; Huang, Zhengren

2017-08-01

Titanium carbide/hastelloy (TiC/hastelloy) composites are potential candidates for intermediate-temperature solid oxide fuel cell interconnects. In this work, TiC/hastelloy composites with suitable coefficient of thermal expansion are fabricated by in-situ reactive infiltration method, and their properties are optimized by adjusting TiC particle size (dTiC). The oxidation process of TiC/hastelloy composites is comprehensive performance of TiC and Ni-Cr alloy and determined by outward diffusion of Ti and Ni atoms and internal diffusion of O2. The oxidation resistance of composites could be improved by the decrease of dTiC through accelerating the formation of continuous and dense TiO2/Cr2O3 oxide scale. Moreover, the electrical conductivity of composites at 800 °C for 100 h is 5600-7500 S cm-1 and changes little with the prolongation of oxidation time. The decrease of dTiC is favorable for the properties optimization, and composites with 2.16 μm TiC exhibits good integrated properties.

Cerium and niobium doped SrCoO3-δ as a potential cathode for intermediate temperature solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Huang, Shouguo; Feng, Shuangjiu; Lu, Qiliang; Li, Yide; Wang, Hong; Wang, Chunchang

2014-04-01

Sr0.9Ce0.1Co0.9Nb0.1O3-δ (SCCN) has been synthesized using solid state reaction, and investigated as a new cathode material for intermediate temperature solid oxide fuel cells (ITSOFCs). SCCN material exhibits sufficiently high electronic conductivity and excellent chemical compatibility with SDC electrolyte. Highly charged Ce4+ and Nb5+ successfully stabilize the perovskite structure to avoid order-disorder phase transition. The electrical conductivity reaches a high value of 516 S cm-1 at 300 °C in air. The area specific resistances of the SCCN-50 wt.% Ce0.8Sm0.2O1.9 (SDC) cathode are as low as 0.027, 0.049, and 0.094 Ω cm2 at 700, 650, and 600 °C, respectively, with the corresponding peak power densities of 1074, 905, and 589 mW cm-2. A relatively low thermal expansion coefficient of SCCN-SDC is 14.3 × 10-6 K-1 in air. All these results imply that SCCN holds tremendous promise as a cathode material for ITSOFCs.

Fuel-conservation evaluation of US Army helicopters. Part 6. Performance calculator evaluation. Final report for period ending January 1981

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dominick, F.; Lockwood, R.A.

1986-07-01

The US Army Aviation Engineering Flight Activity conducted an evaluation of Flight Management Calculator for the UH-1H. The calculator was a Hewlett-Packard HP-41CV. The performance calculator was evaluated for flight planning and in-flight use during 14 mission flights simulating operational conditions. The calculator was much easier to use in-flight than the operator's manual data. The calculator program needs improvement in the areas of pre-flight planning and execution speed. The mission flights demonstrated a 19% fuel saving using optimum over normal flight profiles in warm temperatures (15/sup 0/C above standard). Savings would be greater at colder temperatures because of increasing compressibilitymore » effects. Acceptable accuracy for individual aircraft under operational conditions may require a regressive analog model in which individual aircraft data are used to update the program. The performance data base for the UH-1H was expanded with level flight and hover data to thrust coefficients and Mach numbers to the practical limits of aircraft operation.« less

Hybrid Propulsion In-Situ Resource Utilization Test Facility Results

NASA Technical Reports Server (NTRS)

Karp, Ashley Chandler; Nakazono, Barry; Vaughan, David; Warner, William N.

2015-01-01

Hybrid rockets present a promising alternative to conventional chemical propulsion systems for In-Situ Resource Utilization (ISRU) and in-space applications. While they have many benefits for these applications, there are still many small details that require research before they can be adopted into flight systems. A flexible test facility was developed at JPL to test operation of hybrid motors at small scale (5 cm outer diameter fuel grains) over a range of conditions. Specifically, this paper studies two of the major advantages: low temperature performance and throttling. Paraffin-based hybrid rockets are predicted to have good performance at low temperatures. This could significantly decrease the overall system mass by minimizing the thermal conditioning required for Mars or outer planet applications. Therefore, the coefficient of thermal expansion and glass transition of paraffin are discussed. Additionally, deep throttling has been considered for several applications. This was a natural starting point for hotfire testing using the hybrid propulsion ISRU test facility. Additionally, short length to diameter ratio (L/D) fuel grains are tested to determine if these systems can be packaged into geometrically constrained spaces.

Effect of carbon ion irradiation on Ag diffusion in SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leng, Bin; Ko, Hyunseok; Gerczak, Tyler J.

Transport of Ag fission product through the silicon-carbide (SiC) diffusion barrier layer in TRISO fuel particles is of considerable interest given the application of this fuel type in high temperature gas-cooled reactor (HTGR) and other future reactor concepts. The reactor experiments indicate that radiation may play an important role in release of Ag; however so far the isolated effect of radiation on Ag diffusion has not been investigated in controlled laboratory experiments. In this study, we investigate the diffusion couples of Ag and polycrystalline 3C–SiC, as well as Ag and single crystalline 4H–SiC samples before and after irradiation with Cmore » 2+ ions. The diffusion couple samples were exposed to temperatures of 1500 °C, 1535 °C, and 1569 °C, and the ensuing diffusion profiles were analyzed by secondary ion mass spectrometry (SIMS). We found that diffusion coefficients calculated from these measurements indicate that Ag diffusion was greatly enhanced by carbon irradiation due to a combined effect of radiation damage on diffusion and the presence of grain boundaries in polycrystalline SiC samples.« less

Effect of carbon ion irradiation on Ag diffusion in SiC

DOE PAGES

Leng, Bin; Ko, Hyunseok; Gerczak, Tyler J.; ...

2015-11-14

Transport of Ag fission product through the silicon-carbide (SiC) diffusion barrier layer in TRISO fuel particles is of considerable interest given the application of this fuel type in high temperature gas-cooled reactor (HTGR) and other future reactor concepts. The reactor experiments indicate that radiation may play an important role in release of Ag; however so far the isolated effect of radiation on Ag diffusion has not been investigated in controlled laboratory experiments. In this study, we investigate the diffusion couples of Ag and polycrystalline 3C–SiC, as well as Ag and single crystalline 4H–SiC samples before and after irradiation with Cmore » 2+ ions. The diffusion couple samples were exposed to temperatures of 1500 °C, 1535 °C, and 1569 °C, and the ensuing diffusion profiles were analyzed by secondary ion mass spectrometry (SIMS). We found that diffusion coefficients calculated from these measurements indicate that Ag diffusion was greatly enhanced by carbon irradiation due to a combined effect of radiation damage on diffusion and the presence of grain boundaries in polycrystalline SiC samples.« less

Thermal Analysis of ZPPR High Pu Content Stored Fuel

DOE PAGES

Solbrig, Charles W.; Pope, Chad L.; Andrus, Jason P.

2014-09-17

The Zero Power Physics Reactor (ZPPR) operated from April 18, 1969, until 1990. ZPPR operated at low power for testing nuclear reactor designs. This paper examines the temperature of Pu content ZPPR fuel while it is in storage. Heat is generated in the fuel due to Pu and Am decay and is a concern for possible cladding damage. Damage to the cladding could lead to fuel hydriding and oxidizing. A series of computer simulations were made to determine the range of temperatures potentially occuring in the ZPPR fuel. The maximum calculated fuel temperature is 292°C (558°F). Conservative assumptions in themore » model intentionally overestimate temperatures. The stored fuel temperatures are dependent on the distribution of fuel in the surrounding storage compartments, the heat generation rate of the fuel, and the orientation of fuel. Direct fuel temperatures could not be measured but storage bin doors, storage sleeve doors, and storage canister temperatures were measured. Comparison of these three temperatures to the calculations indicates that the temperatures calculated with conservative assumptions are, as expected, higher than the actual temperatures. The maximum calculated fuel temperature with the most conservative assumptions is significantly below the fuel failure criterion of 600°C (1,112°F).« less

Methods for determining the internal thrust of scramjet engine modules from experimental data

NASA Technical Reports Server (NTRS)

Voland, Randall T.

1990-01-01

Methods for calculating zero-fuel internal drag of scramjet engine modules from experimental measurements are presented. These methods include two control-volume approaches, and a pressure and skin-friction integration. The three calculation techniques are applied to experimental data taken during tests of a version of the NASA parametric scramjet. The methods agree to within seven percent of the mean value of zero-fuel internal drag even though several simplifying assumptions are made in the analysis. The mean zero-fuel internal drag coefficient for this particular engine is calculated to be 0.150. The zero-fuel internal drag coefficient when combined with the change in engine axial force with and without fuel defines the internal thrust of an engine.

Theoretical Performance of Liquid Hydrogen with Liquid Oxygen as a Rocket Propellant

NASA Technical Reports Server (NTRS)

Gordon, Sanford; McBride, Bonnie J.

1959-01-01

Theoretical rocket performance for both equilibrium and frozen composition during expansion was calculated for the propellant combination liquid hydrogen and liquid oxygen at four chamber pressures (60, 150, 300, and 600 lb/sq in. abs) and a wide range of pressure ratios (1 to 4000) and oxidant-fuel ratios (1.190 to 39.683). Data are given to estimate performance parameters at chamber pressures other than those for which data are tabulated. The parameters included are specific impulse, specific impulse in vacuum, combustion-chamber temperature, nozzle-exit temperature, molecular weight, molecular-weight derivatives, characteristic velocity, coefficient of thrust, ratio of nozzle-exit area to throat area, specific heat at constant pressure, isentropic exponent, viscosity, thermal conductivity, Mach number, and equilibrium gas compositions.

Oxygen self-diffusion in ThO 2 under pressure: Connecting point defect parameters with bulk properties

DOE PAGES

Cooper, Michael William D.; Fitzpatrick, M. E.; Tsoukalas, L. H.; ...

2016-06-06

ThO 2 is a candidate material for use in nuclear fuel applications and as such it is important to investigate its materials properties over a range of temperatures and pressures. In the present study molecular dynamics calculations are used to calculate elastic and expansivity data. These are used in the framework of a thermodynamic model, the cBΩ model, to calculate the oxygen self-diffusion coefficient in ThO 2 over a range of pressures (–10–10 GPa) and temperatures (300–1900 K). As a result, increasing the hydrostatic pressure leads to a significant reduction in oxygen self-diffusion. Conversely, negative hydrostatic pressure significantly enhances oxygenmore » self-diffusion.« less

Self-similar solutions for multi-species plasma mixing by gradient driven transport

NASA Astrophysics Data System (ADS)

Vold, E.; Kagan, G.; Simakov, A. N.; Molvig, K.; Yin, L.

2018-05-01

Multi-species transport of plasma ions across an initial interface between DT and CH is shown to exhibit self-similar species density profiles under 1D isobaric conditions. Results using transport theory from recent studies and using a Maxwell–Stephan multi-species approximation are found to be in good agreement for the self-similar mix profiles of the four ions under isothermal and isobaric conditions. The individual ion species mass flux and molar flux profile results through the mixing layer are examined using transport theory. The sum over species mass flux is confirmed to be zero as required, and the sum over species molar flux is related to a local velocity divergence needed to maintain pressure equilibrium during the transport process. The light ion species mass fluxes are dominated by the diagonal coefficients of the diffusion transport matrix, while for the heaviest ion species (C in this case), the ion flux with only the diagonal term is reduced by about a factor two from that using the full diffusion matrix, implying the heavy species moves more by frictional collisions with the lighter species than by its own gradient force. Temperature gradient forces were examined by comparing profile results with and without imposing constant temperature gradients chosen to be of realistic magnitude for ICF experimental conditions at a fuel-capsule interface (10 μm scale length or greater). The temperature gradients clearly modify the relative concentrations of the ions, for example near the fuel center, however the mixing across the fuel-capsule interface appears to be minimally influenced by the temperature gradient forces within the expected compression and burn time. Discussion considers the application of the self-similar profiles to specific conditions in ICF.

Thermocouple Probe Orientation Affects Prescribed Fire Behavior Estimation.

PubMed

Coates, T Adam; Chow, Alex T; Hagan, Donald L; Waldrop, Thomas A; Wang, G Geoff; Bridges, William C; Rogers, Mary-Frances; Dozier, James H

2018-01-01

Understanding the relationship between fire intensity and fuel mass is essential information for scientists and forest managers seeking to manage forests using prescribed fires. Peak burning temperature, duration of heating, and area under the temperature profile are fire behavior metrics obtained from thermocouple-datalogger assemblies used to characterize prescribed burns. Despite their recurrent usage in prescribed burn studies, there is no simple protocol established to guide the orientation of thermocouple installation. Our results from dormant and growing season burns in coastal longleaf pine ( Mill.) forests in South Carolina suggest that thermocouples located horizontally at the litter-soil interface record significantly higher estimates of peak burning temperature, duration of heating, and area under the temperature profile than thermocouples extending 28 cm vertically above the litter-soil interface ( < 0.01). Surprisingly, vertical and horizontal estimates of these measures did not show strong correlation with one another ( ≤ 0.14). The horizontal duration of heating values were greater in growing season burns than in dormant season burns ( < 0.01), but the vertical values did not indicate this difference ( = 0.52). Field measures of fuel mass and depth before and after fire showed promise as significant predictive variables ( ≤ 0.05) for the fire behavior metrics. However, all correlation coefficients were less than or equal to = 0.41. Given these findings, we encourage scientists, researchers, and managers to carefully consider thermocouple orientation when investigating fire behavior metrics, as orientation may affect estimates of fire intensity and the distinction of fire treatment effects, particularly in forests with litter-dominated surface fuels. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Next-Generation Electrochemical Energy Materials for Intermediate Temperature Molten Oxide Fuel Cells and Ion Transport Molten Oxide Membranes.

PubMed

Belousov, Valery V

2017-02-21

High temperature electrochemical devices such as solid oxide fuel cells (SOFCs) and oxygen separators based on ceramic materials are used for efficient energy conversion. These devices generally operate in the temperature range of 800-1000 °C. The high operating temperatures lead to accelerated degradation of the SOFC and oxygen separator materials. To solve this problem, the operating temperatures of these electrochemical devices must be lowered. However, lowering the temperature is accompanied by decreasing the ionic conductivity of fuel cell electrolyte and oxygen separator membrane. Therefore, there is a need to search for alternative electrolyte and membrane materials that have high ionic conductivity at lower temperatures. A great many opportunities exist for molten oxides as electrochemical energy materials. Because of their unique electrochemical properties, the molten oxide innovations can offer significant benefits for improving energy efficiency. In particular, the newly developed electrochemical molten oxide materials show high ionic conductivities at intermediate temperatures (600-800 °C) and could be used in molten oxide fuel cells (MOFCs) and molten oxide membranes (MOMs). The molten oxide materials containing both solid grains and liquid channels at the grain boundaries have advantages compared to the ceramic materials. For example, the molten oxide materials are ductile, which solves a problem of thermal incompatibility (difference in coefficient of thermal expansion, CTE). Besides, the outstanding oxygen selectivity of MOM materials allows us to separate ultrahigh purity oxygen from air. For their part, the MOFC electrolytes show the highest ionic conductivity at intermediate temperatures. To evaluate the potential of molten oxide materials for technological applications, the relationship between the microstructure of these materials and their transport and mechanical properties must be revealed. This Account summarizes the latest results on oxygen ion transport in potential MOM materials and MOFC electrolytes. In addition, we consider the rapid oxygen transport in a molten oxide scale formed on a metal surface during catastrophic oxidation and show that the same transport could be used beneficially in MOMs and MOFCs. A polymer model explaining the oxygen transport in molten oxides is also considered. Understanding the oxygen transport mechanisms in oxide melts is important for the development of new generation energy materials, which will contribute to more efficient operation of electrochemical devices at intermediate temperatures. Here we highlight the progress made in developing this understanding. We also show the latest advances made in search of alternative molten oxide materials having high mixed ion electronic and ionic conductivities for use in MOMs and MOFCs, respectively. Prospects for further research are presented.

Upgraded bio-oil production via catalytic fast co-pyrolysis of waste cooking oil and tea residual.

PubMed

Wang, Jia; Zhong, Zhaoping; Zhang, Bo; Ding, Kuan; Xue, Zeyu; Deng, Aidong; Ruan, Roger

2017-02-01

Catalytic fast co-pyrolysis (co-CFP) offers a concise and effective process to achieve an upgraded bio-oil production. In this paper, co-CFP experiments of waste cooking oil (WCO) and tea residual (TR) with HZSM-5 zeolites were carried out. The influences of pyrolysis reaction temperature and H/C ratio on pyrolytic products distribution and selectivities of aromatics were performed. Furthermore, the prevailing synergetic effect of target products during co-CFP process was investigated. Experimental results indicated that H/C ratio played a pivotal role in carbon yields of aromatics and olefins, and with H/C ratio increasing, the synergetic coefficient tended to increase, thus led to a dramatic growth of aromatics and olefins yields. Besides, the pyrolysis temperature made a significant contribution to carbon yields, and the yields of aromatics and olefins increased at first and then decreased at the researched temperature region. Note that 600°C was an optimum temperature as the maximum yields of aromatics and olefins could be achieved. Concerning the transportation fuel dependence and security on fossil fuels, co-CFP of WCO and TR provides a novel way to improve the quality and quantity of pyrolysis bio-oil, and thus contributes bioenergy accepted as a cost-competitive and promising alternative energy. Copyright © 2016 Elsevier Ltd. All rights reserved.

Trench fast reactor design using the microcomputer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rohach, A.F.; Sankoorikal, J.T.; Schmidt, R.R.

1987-01-01

This project is a study of alternative liquid-metal-cooled fast power reactor system concepts. Specifically, an unconventional primary system is being conceptually designed and evaluated. The project design is based primarily on microcomputer analysis through the use of computational modules. The reactor system concept is a long, narrow pool with a long, narrow reactor called a trench-type pool reactor in it. The reactor consists of five core-blanket modules in a line. Specific power is to be modest, permitting long fuel residence time. Two fuel cycles are currently being considered. The reactor design philosophy is that of the inherently safe concept. Thismore » requires transient analysis dependent on reactivity coefficients: prompt fuel, including Doppler and expansion, fuel expansion, sodium temperature and void, and core expansion. Conceptual reactor design is done on a microcomputer. A part of the trench reactor project is to develop a microcomputer-based system that can be used by the user for scoping studies and design. Current development includes the neutronics and fuel management aspects of the design. Thermal-hydraulic analysis and economics are currently being incorporated into the microcomputer system. The system is menu-driven including preparation of program input data and of output data for displays in graphics form.« less

Ion conduction mechanisms and thermal properties of hydrated and anhydrous phosphoric acids studied with 1H, 2H, and 31P NMR.

PubMed

Aihara, Yuichi; Sonai, Atsuo; Hattori, Mineyuki; Hayamizu, Kikuko

2006-12-14

To understand the behaviors of phosphoric acids in fuel cells, the ion conduction mechanisms of phosphoric acids in condensed states without free water and in a monomer state with water were studied by measuring the ionic conductivity (sigma) using AC impedance, thermal properties, and self-diffusion coefficients (D) and spin-lattice relaxation times (T1) with multinuclear NMR. The self-diffusion coefficient of the protons (H+ or H3O+), H2O, and H located around the phosphate were always larger than the diffusion coefficients of the phosphates and the disparity increased with increasing phosphate concentration. The diffusion coefficients of the samples containing D2O paralleled those in the protonated samples. Since the 1H NMR T1 values exhibited a minimum with temperature, it was possible to determine the correlation times and they were found to be of nanosecond order for a distance of nanometer order for a flip. The agreement of the ionic conductivities measured directly and those calculated from the diffusion coefficients indicates that the ion conduction obeys the Nernst-Einstein equation in the condensed phosphoric acids. The proton diffusion plays a dominant role in the ion conduction, especially in the condensed phosphoric acids.

Thorium-based mixed oxide fuel in a pressurized water reactor: A feasibility analysis with MCNP

NASA Astrophysics Data System (ADS)

Tucker, Lucas Powelson

This dissertation investigates techniques for spent fuel monitoring, and assesses the feasibility of using a thorium-based mixed oxide fuel in a conventional pressurized water reactor for plutonium disposition. Both non-paralyzing and paralyzing dead-time calculations were performed for the Portable Spectroscopic Fast Neutron Probe (N-Probe), which can be used for spent fuel interrogation. Also, a Canberra 3He neutron detector's dead-time was estimated using a combination of subcritical assembly measurements and MCNP simulations. Next, a multitude of fission products were identified as candidates for burnup and spent fuel analysis of irradiated mixed oxide fuel. The best isotopes for these applications were identified by investigating half-life, photon energy, fission yield, branching ratios, production modes, thermal neutron absorption cross section and fuel matrix diffusivity. 132I and 97Nb were identified as good candidates for MOX fuel on-line burnup analysis. In the second, and most important, part of this work, the feasibility of utilizing ThMOX fuel in a pressurized water reactor (PWR) was first examined under steady-state, beginning of life conditions. Using a three-dimensional MCNP model of a Westinghouse-type 17x17 PWR, several fuel compositions and configurations of a one-third ThMOX core were compared to a 100% UO2 core. A blanket-type arrangement of 5.5 wt% PuO2 was determined to be the best candidate for further analysis. Next, the safety of the ThMOX configuration was evaluated through three cycles of burnup at several using the following metrics: axial and radial nuclear hot channel factors, moderator and fuel temperature coefficients, delayed neutron fraction, and shutdown margin. Additionally, the performance of the ThMOX configuration was assessed by tracking cycle length, plutonium destroyed, and fission product poison concentration.

The effects of temperatures on the pebble flow in a pebble bed high temperature reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sen, R. S.; Cogliati, J. J.; Gougar, H. D.

2012-07-01

The core of a pebble bed high temperature reactor (PBHTR) moves during operation, a feature which leads to better fuel economy (online refueling with no burnable poisons) and lower fuel stress. The pebbles are loaded at the top and trickle to the bottom of the core after which the burnup of each is measured. The pebbles that are not fully burned are recirculated through the core until the target burnup is achieved. The flow pattern of the pebbles through the core is of importance for core simulations because it couples the burnup distribution to the core temperature and power profiles,more » especially in cores with two or more radial burnup 'zones '. The pebble velocity profile is a strong function of the core geometry and the friction between the pebbles and the surrounding structures (other pebbles or graphite reflector blocks). The friction coefficient for graphite in a helium environment is inversely related to the temperature. The Thorium High Temperature Reactor (THTR) operated in Germany between 1983 and 1989. It featured a two-zone core, an inner core (IC) and outer core (OC), with different fuel mixtures loaded in each zone. The rate at which the IC was refueled relative to the OC in THTR was designed to be 0.56. During its operation, however, this ratio was measured to be 0.76, suggesting the pebbles in the inner core traveled faster than expected. It has been postulated that the positive feedback effect between inner core temperature, burnup, and pebble flow was underestimated in THTR. Because of the power shape, the center of the core in a typical cylindrical PBHTR operates at a higher temperature than the region next to the side reflector. The friction between pebbles in the IC is lower than that in the OC, perhaps causing a higher relative flow rate and lower average burnup, which in turn yield a higher local power density. Furthermore, the pebbles in the center region have higher velocities than the pebbles next to the side reflector due to the interaction between the pebbles and the immobile graphite reflector as well as the geometry of the discharge conus near the bottom of the core. In this paper, the coupling between the temperature profile and the pebble flow dynamics was analyzed by using PEBBED/THERMIX and PEBBLES codes by modeling the HTR-10 reactor in China. Two extreme and opposing velocity profiles are used as a starting point for the iterations. The PEBBED/THERMIX code is used to calculate the burnup, power and temperature profiles with one of the velocity profiles as input. The resulting temperature profile is then passed to PEBBLES code to calculate the updated pebble velocity profile taking the new temperature profile into account. If the aforementioned hypothesis is correct, the strong temperature effect upon the friction coefficients would cause the two cases to converge to different final velocity and temperature profiles. The results of this analysis indicates that a single zone pebble bed core is self-stabilizing in terms of the pebble velocity profile and the effect of the temperature profile on the pebble flow is insignificant. (authors)« less

Fuel cell-fuel cell hybrid system

DOEpatents

Geisbrecht, Rodney A.; Williams, Mark C.

2003-09-23

A device for converting chemical energy to electricity is provided, the device comprising a high temperature fuel cell with the ability for partially oxidizing and completely reforming fuel, and a low temperature fuel cell juxtaposed to said high temperature fuel cell so as to utilize remaining reformed fuel from the high temperature fuel cell. Also provided is a method for producing electricity comprising directing fuel to a first fuel cell, completely oxidizing a first portion of the fuel and partially oxidizing a second portion of the fuel, directing the second fuel portion to a second fuel cell, allowing the first fuel cell to utilize the first portion of the fuel to produce electricity; and allowing the second fuel cell to utilize the second portion of the fuel to produce electricity.

An experimental and modeling study of the autoignition of 3-methylheptane

DOE PAGES

Wang, Weijing; Li, Zhenhua; Oehlschlaeger, Matthew A.; ...

2013-01-01

An experimental and kinetic modeling study of the autoignition of 3-methylheptane, a compound representative of the high molecular weight lightly branched alkanes found in large quantities in conventional and synthetic aviation kerosene and diesel fuels, is reported. Shock tube and rapid compression machine ignition delay time measurements are reported over a wide range of conditions of relevance to combustion engine applications: temperatures from 678 to 1356 K; pressures of 6.5, 10, 20, and 50 atm; and equivalence ratios of 0.5, 1.0, and 2.0. The wide range of temperatures examined provides observation of autoignition in three reactivity regimes, including the negativemore » temperature coefficient (NTC) regime characteristic of paraffinic fuels. Comparisons made between the current ignition delay measurements for 3-methylheptane and previous results for n-octane and 2-methylheptane quantifies the influence of a single methyl substitution and its location on the reactivity of alkanes. It is found that the three C8 alkane isomers have indistinguishable high-temperature ignition delay but their ignition delay times deviate in the NTC and low-temperature regimes in correlation with their research octane numbers. The experimental results are compared with the predictions of a proposed kinetic model that includes both high- and low-temperature oxidation chemistry. The model mechanistically explains the differences in reactivity for n-octane, 2-methylheptane, and 3-methylheptane in the NTC through the influence of the methyl substitution on the rates of isomerization reactions in the low-temperature chain branching pathway, that ultimately leads to ketohydroperoxide species, and the competition between low-temperature chain branching and the formation of cyclic ethers, in a chain propagating pathway.« less

Low temperature chemical processing of graphite-clad nuclear fuels

DOEpatents

Pierce, Robert A.

2017-10-17

A reduced-temperature method for treatment of a fuel element is described. The method includes molten salt treatment of a fuel element with a nitrate salt. The nitrate salt can oxidize the outer graphite matrix of a fuel element. The method can also include reduced temperature degradation of the carbide layer of a fuel element and low temperature solubilization of the fuel in a kernel of a fuel element.

High-freezing-point fuels used for aviation turbine engines

NASA Technical Reports Server (NTRS)

Friedman, R.

1979-01-01

Broadened-specification aviation fuels could be produced from a greater fraction of crude source material with improvements in fuel supply and price. These fuels, particularly those with increased final boiling temperatures, would have higher freezing temperatures than current aviation turbine fuels. The higher-freezing-point fuels can be substituted in the majority of present commercial flights, since temperature data indicate that in-flight fuel temperatures are relatively mild. For the small but significant fraction of commercial flights where low fuel temperatures make higher freezing-point fuel use unacceptable, adaptations to the fuel or fuel system may be made to accommodate this fuel. Several techniques are discussed. Fuel heating is the most promising concept. One simple system design uses existing heat rejection from the fuel-lubricating oil cooler, another uses an engine-driven generator for electrical heating. Both systems offer advantages that outweigh the obvious penalties.

Influence of fuel temperature on atomization performance of pressure-swirl atomizers

NASA Astrophysics Data System (ADS)

Wang, X. F.; Lefebvre, A. H.

The influence of fuel temperature on mean drop size and drop-size distribution is examined for aviation gasoline and diesel oil, using three pressure-swirl simplex nozzles. Spray characteristics are measured over wide ranges of fuel injection pressure and ambient air pressure using a Malvern spray analyzer. Fuel temperatures are varied from -20 C to +50 C. Over this range of temperature, the overall effect of an increase in fuel temperature is to reduce the mean drop size and broaden the distribution of drop sizes in the spray. Generally, it is found that the influence of fuel temperature on mean drop size is far more pronounced for diesel oil than for gasoline. For both fuels the beneficial effect of higher fuel temperatures on atomization quality is sensibly independent of ambient air pressure.

Partitioning of Aromatic Constituents into Water from Jet Fuels.

PubMed

Tien, Chien-Jung; Shu, Youn-Yuen; Ciou, Shih-Rong; Chen, Colin S

2015-08-01

A comprehensive study of the most commonly used jet fuels (i.e., Jet A-1 and JP-8) was performed to properly assess potential contamination of the subsurface environment from a leaking underground storage tank occurred in an airport. The objectives of this study were to evaluate the concentration ranges of the major components in the water-soluble fraction of jet fuels and to estimate the jet fuel-water partition coefficients (K fw) for target compounds using partitioning experiments and a polyparameter linear free-energy relationship (PP-LFER) approach. The average molecular weight of Jet A-1 and JP-8 was estimated to be 161 and 147 g/mole, respectively. The density of Jet A-1 and JP-8 was measured to be 786 and 780 g/L, respectively. The distribution of nonpolar target compounds between the fuel and water phases was described using a two-phase liquid-liquid equilibrium model. Models were derived using Raoult's law convention for the activity coefficients and the liquid solubility. The observed inverse, log-log linear dependence of the K fw values on the aqueous solubility were well predicted by assuming jet fuel to be an ideal solvent mixture. The experimental partition coefficients were generally well reproduced by PP-LFER.

Chemical interactions in complex matrices: Determination of polar impurities in biofuels and fuel contaminants in building materials

NASA Astrophysics Data System (ADS)

Baglayeva, Ganna

The solutions to several real-life analytical and physical chemistry problems, which involve chemical interactions in complex matrices are presented. The possible interferences due to the analyte-analyte and analyte-matrix chemical interactions were minimized on each step of the performed chemical analysis. Concrete and wood, as major construction materials, typically become contaminated with fuel oil hydrocarbons during their spillage. In the catastrophic scenarios (e.g., during floods), fuel oil mixes with water and then becomes entrained within the porous structure of wood or concrete. A strategy was proposed for the efficient extraction of fuel oil hydrocarbons from concrete to enable their monitoring. The impacts of sample aging and inundation with water on the extraction efficiency were investigated to elucidate the nature of analytematrix interactions. Two extraction methods, 4-days cold solvent extraction with shaking and 24-hours Soxhlet extraction with ethylacetate, methanol or acetonitrile yielded 95-100 % recovery of fuel oil hydrocarbons from concrete. A method of concrete remediation after contamination with fuel oil hydrocarbons using activated carbon as an adsorbent was developed. The 14 days remediation was able to achieve ca. 90 % of the contaminant removal even from aged water-submerged concrete samples. The degree of contamination can be qualitatively assessed using transport rates of the contaminants. Two models were developed, Fickian and empirical, to predict long-term transport behavior of fuel oil hydrocarbons under flood representative scenarios into wood. Various sorption parameters, including sorption rate, penetration degree and diffusion coefficients were obtained. The explanations to the observed three sorption phases are provided in terms of analyte-matrix interactions. The detailed simultaneous analysis of intermediate products of the cracking of triacylglycerol oils, namely monocarboxylic acids, triacyl-, diacyl- and monoacylglycerols was developed. The identification and quantification of analytes were performed using a 15-m high temperature capillary column (DB-1HT) with a GC coupled to both flame ionization and mass spectrometric detectors. To eliminate discrimination of low or high molecular weight species, programmed temperature vaporization (PTV) injection parameters were optimized using design of experiments methodology. Evaluation of the column temperature program and MS parameters allowed achieving separation of majority of target compounds based on their total number of carbon atoms, regioisomerization and, to some extent, degree of unsaturation.

Rotating disk electrode study of borohydride oxidation in a molten eutectic electrolyte and advancements in the intermediate temperature borohydride battery

NASA Astrophysics Data System (ADS)

Wang, Andrew; Gyenge, Előd L.

2017-08-01

The electrode kinetics of the NaBH4 oxidation reaction (BOR) in a molten NaOH-KOH eutectic mixture is investigated by rotating disk electrode (RDE) voltammetry on electrochemically oxidized Ni at temperatures between 458 K and 503 K. The BH4- diffusion coefficient in the molten alkali eutectic together with the BOR activation energy, exchange current density, transfer coefficient and number of electrons exchanged, are determined. Electrochemically oxidized Ni shows excellent BOR electrocatalytic activity with a maximum of seven electrons exchanged and a transfer coefficient up to one. X-ray photoelectron spectroscopy (XPS) reveals the formation of NiO as the catalytically active species. The high faradaic efficiency and BOR rate on oxidized Ni anode in the molten electrolyte compared to aqueous alkaline electrolytes is advantageous for power sources. A novel molten electrolyte battery design is investigated using dissolved NaBH4 at the anode and immobilized KIO4 at the cathode. This battery produces a stable open-circuit cell potential of 1.04 V, and a peak power density of 130 mW cm-2 corresponding to a superficial current density of 160 mA cm-2 at 458 K. With further improvements and scale-up borohydride molten electrolyte batteries and fuel cells could be integrated with thermal energy storage systems.

Development of Optimized Core Design and Analysis Methods for High Power Density BWRs

NASA Astrophysics Data System (ADS)

Shirvan, Koroush

Increasing the economic competitiveness of nuclear energy is vital to its future. Improving the economics of BWRs is the main goal of this work, focusing on designing cores with higher power density, to reduce the BWR capital cost. Generally, the core power density in BWRs is limited by the thermal Critical Power of its assemblies, below which heat removal can be accomplished with low fuel and cladding temperatures. The present study investigates both increases in the heat transfer area between ~he fuel and coolant and changes in operating parameters to achieve higher power levels while meeting the appropriate thermal as well as materials and neutronic constraints. A scoping study is conducted under the constraints of using fuel with cylindrical geometry, traditional materials and enrichments below 5% to enhance its licensability. The reactor vessel diameter is limited to the largest proposed thus far. The BWR with High power Density (BWR-HD) is found to have a power level of 5000 MWth, equivalent to 26% uprated ABWR, resulting into 20% cheaper O&M and Capital costs. This is achieved by utilizing the same number of assemblies, but with wider 16x16 assemblies and 50% shorter active fuel than that of the ABWR. The fuel rod diameter and pitch are reduced to just over 45% of the ABWR values. Traditional cruciform form control rods are used, which restricts the assembly span to less than 1.2 times the current GE14 design due to limitation on shutdown margin. Thus, it is possible to increase the power density and specific power by 65%, while maintaining the nominal ABWR Minimum Critical Power Ratio (MCPR) margin. The plant systems outside the vessel are assumed to be the same as the ABWR-Il design, utilizing a combination of active and passive safety systems. Safety analyses applied a void reactivity coefficient calculated by SIMULA TE-3 for an equilibrium cycle core that showed a 15% less negative coefficient for the BWR-HD compared to the ABWR. The feedwater temperature was kept the same for the BWR-HD and ABWR which resulted in 4 °K cooler core inlet temperature for the BWR-HD given that its feedwater makes up a larger fraction of total core flow. The stability analysis using the STAB and S3K codes showed satisfactory results for the hot channel, coupled regional out-of-phase and coupled core-wide in-phase modes. A RELAPS model of the ABWR system was constructed and applied to six transients for the BWR-HD and ABWR. The 6MCPRs during all the transients were found to be equal or less for the new design and the core remained covered for both. The lower void coefficient along with smaller core volume proved to be advantages for the simulated transients. Helical Cruciform Fuel (HCF) rods were proposed in prior MIT studies to enhance the fuel surface to volume ratio. In this work, higher fidelity models (e.g. CFD instead of subchannel methods for the hydraulic behaviour) are used to investigate the resolution needed for accurate assessment of the HCF design. For neutronics, conserving the fuel area of cylindrical rods results in a different reactivity level with a lower void coefficient for the HCF design. In single-phase flow, for which experimental results existed, the friction factor is found to be sensitive to HCF geometry and cannot be calculated using current empirical models. A new approach for analysis of flow crisis conditions for HCF rods in the context of Departure from Nucleate Boiling (DNB) and dryout using the two phase interface tracking method was proposed and initial results are presented. It is shown that the twist of the HCF rods promotes detachment of a vapour bubble along the elbows which indicates no possibility for an early DNB for the HCF rods and in fact a potential for a higher DNB heat flux. Under annular flow conditions, it was found that the twist suppressed the liquid film thickness on the HCF rods, at the locations of the highest heat flux, which increases the possibility of reaching early dryout. It was also shown that modeling the 3D heat and stress distribution in the HCF rods is necessary for accurate steady state and transient analyses. (Abstract shortened by UMI.) (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

The structure and propagation of laminar flames under autoignitive conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krisman, Alex; Hawkes, Evatt R.; Chen, Jacqueline H.

Tmore » he laminar flame speed s l is an important reference quantity for characterising and modelling combustion. Experimental measurements of laminar flame speed require the residence time of the fuel/air mixture (τ f) to be shorter than the autoignition delay time (τ). his presents a considerable challenge for conditions where autoignition occurs rapidly, such as in compression ignition engines. As a result, experimental measurements in typical compression ignition engine conditions do not exist. Simulations of freely propagating premixed flames, where the burning velocity is found as an eigenvalue of the solution, are also not well posed in such conditions, since the mixture ahead of the flame can autoignite, leading to the so called “cold boundary problem”. In this paper, a numerical method for estimating a reference flame speed, s R, is proposed that is valid for laminar flame propagation at autoignitive conditions. wo isomer fuels are considered to test this method: ethanol, which in the considered conditions is a single-stage ignition fuel; and dimethyl ether, which has a temperature-dependent single- or two-stage ignition and a negative temperature coefficient regime for τ. Calculations are performed for the flame position in a one-dimensional computational domain with inflow-outflow boundary conditions, as a function of the inlet velocity U I and for stoichiometric fuel–air premixtures. he response of the flame position, L F, to U I shows distinct stabilisation regimes. For single-stage ignition fuels, at low U I the flame speed exceeds U I and the flame becomes attached to the inlet. Above a critical U I value, the flame detaches from the inlet and L f becomes extremely sensitive to U I until, for sufficiently high U I, the sensitivity decreases and L f corresponds to the location expected from a purely autoignition stabilised flame. he transition from the attached to the autoignition regimes has a corresponding peak dL f/dU I value which is proposed to be a unique reference flame speed s R for single-stage ignition fuels. For two-stage ignition fuels, there is an additional stable regime where a high-temperature flame propagates into a pool of combustion intermediates generated by the first stage of autoignition. his results in two peaks in dL f/dU I and therefore two reference flame speed values. he lower value corresponds to the definition of s R for single-stage ignition fuels, while the higher value exists only for two-stage ignition fuels and corresponds to a high temperature flame propagating into the first stage of autoignition and is denoted s R ' . Finally, a transport budget analysis for low- and high-temperature radical species is also performed, which confirms that the flame structures at U I = s R and U I = s R ' do indeed correspond to premixed flames (deflagrations), as opposed to spontaneous ignition fronts which do not have a unique propagation speed.« less

The structure and propagation of laminar flames under autoignitive conditions

DOE PAGES

Krisman, Alex; Hawkes, Evatt R.; Chen, Jacqueline H.

2017-11-05

Tmore » he laminar flame speed s l is an important reference quantity for characterising and modelling combustion. Experimental measurements of laminar flame speed require the residence time of the fuel/air mixture (τ f) to be shorter than the autoignition delay time (τ). his presents a considerable challenge for conditions where autoignition occurs rapidly, such as in compression ignition engines. As a result, experimental measurements in typical compression ignition engine conditions do not exist. Simulations of freely propagating premixed flames, where the burning velocity is found as an eigenvalue of the solution, are also not well posed in such conditions, since the mixture ahead of the flame can autoignite, leading to the so called “cold boundary problem”. In this paper, a numerical method for estimating a reference flame speed, s R, is proposed that is valid for laminar flame propagation at autoignitive conditions. wo isomer fuels are considered to test this method: ethanol, which in the considered conditions is a single-stage ignition fuel; and dimethyl ether, which has a temperature-dependent single- or two-stage ignition and a negative temperature coefficient regime for τ. Calculations are performed for the flame position in a one-dimensional computational domain with inflow-outflow boundary conditions, as a function of the inlet velocity U I and for stoichiometric fuel–air premixtures. he response of the flame position, L F, to U I shows distinct stabilisation regimes. For single-stage ignition fuels, at low U I the flame speed exceeds U I and the flame becomes attached to the inlet. Above a critical U I value, the flame detaches from the inlet and L f becomes extremely sensitive to U I until, for sufficiently high U I, the sensitivity decreases and L f corresponds to the location expected from a purely autoignition stabilised flame. he transition from the attached to the autoignition regimes has a corresponding peak dL f/dU I value which is proposed to be a unique reference flame speed s R for single-stage ignition fuels. For two-stage ignition fuels, there is an additional stable regime where a high-temperature flame propagates into a pool of combustion intermediates generated by the first stage of autoignition. his results in two peaks in dL f/dU I and therefore two reference flame speed values. he lower value corresponds to the definition of s R for single-stage ignition fuels, while the higher value exists only for two-stage ignition fuels and corresponds to a high temperature flame propagating into the first stage of autoignition and is denoted s R ' . Finally, a transport budget analysis for low- and high-temperature radical species is also performed, which confirms that the flame structures at U I = s R and U I = s R ' do indeed correspond to premixed flames (deflagrations), as opposed to spontaneous ignition fronts which do not have a unique propagation speed.« less

Effect of increased fuel temperature on emissions of oxides of nitrogen from a gas turbine combustor burning ASTM jet-A fuel

NASA Technical Reports Server (NTRS)

Marchionna, N. R.

1974-01-01

An annular gas turbine combustor was tested with heated ASTM Jet-A fuel to determine the effect of increased fuel temperature on the formation of oxides of nitrogen. Fuel temperature ranged from ambient to 700 K. The NOx emission index increased at a rate of 6 percent per 100 K increase in fuel temperature.

Analysis of fuel options for the breakeven core configuration of the Advanced Recycling Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stauff, N.E.; Klim, T.K.; Taiwo, T.A.

2013-07-01

A trade-off study is performed to determine the impacts of various fuel forms on the core design and core physics characteristics of the sodium-cooled Toshiba- Westinghouse Advanced Recycling Reactor (ARR). The fuel forms include oxide, nitride, and metallic forms of U and Th. The ARR core configuration is redesigned with driver and blanket regions in order to achieve breakeven fissile breeding performance with the various fuel types. State-of-the-art core physics tools are used for the analyses. In addition, a quasi-static reactivity balance approach is used for a preliminary comparison of the inherent safety performances of the various fuel options. Thorium-fueledmore » cores exhibit lower breeding ratios and require larger blankets compared to the U-fueled cores, which is detrimental to core compactness and increases reprocessing and manufacturing requirements. The Th cores also exhibit higher reactivity swings through each cycle, which penalizes reactivity control and increases the number of control rods required. On the other hand, using Th leads to drastic reductions in void and coolant expansion coefficients of reactivity, with the potential for enhancing inherent core safety. Among the U-fueled ARR cores, metallic and nitride fuels result in higher breeding ratios due to their higher heavy metal densities. On the other hand, oxide fuels provide a softer spectrum, which increases the Doppler effect and reduces the positive sodium void worth. A lower fuel temperature is obtained with the metallic and nitride fuels due to their higher thermal conductivities and compatibility with sodium bonds. This is especially beneficial from an inherent safety point of view since it facilitates the reactor cool-down during loss of power removal transients. The advantages in terms of inherent safety of nitride and metallic fuels are maintained when using Th fuel. However, there is a lower relative increase in heavy metal density and in breeding ratio going from oxide to metallic or nitride Th fuels relative to the U counterpart fuels. (authors)« less

Evaluation and Prediction of Henry’s Law Constants and Aqueous Solubilities for Solvents and Hydrocarbon Fuel Components. Volume 2. Experimental Henry’s Law Data

DTIC Science & Technology

1987-09-01

Pollutants by Gas Chromatographic Headspace Analysis. J. Chrom . 260:23-32. Miller, R. E. 1984. Confidence Intervals and Hypothesis Tests. Chem. Engr...tabulation of the injection peak areas, Henry’s law constant estimates, and Coefficient of Variation (COV) values for the component at five temperatures...I 15.1897 (4) I 14.5788 I 19.7121 1 16 6428 Injection: (1) 1 16158 I 2596 38628 Peak Area] (2) 1 154846 1 281438 1 261148 (3) 4673 1 64736 1 63322 (4

Inflight fuel tank temperature survey data

NASA Technical Reports Server (NTRS)

Pasion, A. J.

1979-01-01

Statistical summaries of the fuel and air temperature data for twelve different routes and for different aircraft models (B747, B707, DC-10 and DC-8), are given. The minimum fuel, total air and static air temperature expected for a 0.3% probability were summarized in table form. Minimum fuel temperature extremes agreed with calculated predictions and the minimum fuel temperature did not necessarily equal the minimum total air temperature even for extreme weather, long range flights.

In Situ Neutron Diffraction of Rare-Earth Phosphate Proton Conductors Sr/Ca-doped LaPO4 at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Al-Wahish, Amal; Al-Binni, Usama; Bridges, C. A.; Huq, A.; Bi, Z.; Paranthaman, M. P.; Tang, S.; Kaiser, H.; Mandrus, D.

Acceptor-doped lanthanum orthophosphates are potential candidate electrolytes for proton ceramic fuel cells. We combined neutron powder diffraction (NPD) at elevated temperatures up to 800° C , X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) to investigate the crystal structure, defect structure, thermal stability and surface topography. NPD shows an average bond length distortion in the hydrated samples. We employed Quasi-Elastic Neutron Scattering (QENS) and electrochemical impedance spectroscopy (EIS) to study the proton dynamics of the rare-earth phosphate proton conductors 4.2% Sr/Ca-doped LaPO4. We determined the bulk diffusion and the self-diffusion coefficients. Our results show that QENS and EIS are probing fundamentally different proton diffusion processes. Supported by the U.S. Department of Energy.

Reverberatory screen for a radiant burner

DOEpatents

Gray, Paul E.

1999-01-01

The present invention relates to porous mat gas fired radiant burner panels utilizing improved reverberatory screens. The purpose of these screens is to boost the overall radiant output of the burner relative to a burner using no screen and the same fuel-air flow rates. In one embodiment, the reverberatory screen is fabricated from ceramic composite material, which can withstand higher operating temperatures than its metallic equivalent. In another embodiment the reverberatory screen is corrugated. The corrugations add stiffness which helps to resist creep and thermally induced distortions due to temperature or thermal expansion coefficient differences. As an added benefit, it has been unexpectedly discovered that the corrugations further increase the radiant efficiency of the burner. In a preferred embodiment, the reverberatory screen is both corrugated and made from ceramic composite material.

Effect of Particle Size Distribution on Wall Heat Flux in Pulverized-Coal Furnaces and Boilers

NASA Astrophysics Data System (ADS)

Lu, Jun

A mathematical model of combustion and heat transfer within a cylindrical enclosure firing pulverized coal has been developed and tested against two sets of measured data (one is 1993 WSU/DECO Pilot test data, the other one is the International Flame Research Foundation 1964 Test (Beer, 1964)) and one independent code FURN3D from the Argonne National Laboratory (Ahluwalia and IM, 1992). The model called PILC assumes that the system is a sequence of many well-stirred reactors. A char burnout model combining diffusion to the particle surface, pore diffusion, and surface reaction is employed for predicting the char reaction, heat release, and evolution of char. The ash formation model included relates the ash particle size distribution to the particle size distribution of pulverized coal. The optical constants of char and ash particles are calculated from dispersion relations derived from reflectivity, transmissivity and extinction measurements. The Mie theory is applied to determine the extinction and scattering coefficients. The radiation heat transfer is modeled using the virtual zone method, which leads to a set of simultaneous nonlinear algebraic equations for the temperature field within the furnace and on its walls. This enables the heat fluxes to be evaluated. In comparisons with the experimental data and one independent code, the model is successful in predicting gas temperature, wall temperature, and wall radiative flux. When the coal with greater fineness is burnt, the particle size of pulverized coal has a consistent influence on combustion performance: the temperature peak was higher and nearer to burner, the radiation flux to combustor wall increased, and also the absorption and scattering coefficients of the combustion products increased. The effect of coal particle size distribution on absorption and scattering coefficients and wall heat flux is significant. But there is only a small effect on gas temperature and fuel fraction burned; it is speculated that this may be a characteristic special to the test combustor used.

Electric heater for nuclear fuel rod simulators

DOEpatents

McCulloch, Reginald W.; Morgan, Jr., Chester S.; Dial, Ralph E.

1982-01-01

The present invention is directed to an electric cartridge-type heater for use as a simulator for a nuclear fuel pin in reactor studies. The heater comprises an elongated cylindrical housing containing a longitudinally extending helically wound heating element with the heating element radially inwardly separated from the housing. Crushed cold-pressed preforms of boron nitride electrically insulate the heating element from the housing while providing good thermal conductivity. Crushed cold-pressed preforms of magnesia or a magnesia-15 percent boron nitride mixture are disposed in the cavity of the helical heating element. The coefficient of thermal expansion of the magnesia or the magnesia-boron nitride mixture is higher than that of the boron nitride disposed about the heating element for urging the boron nitride radially outwardly against the housing during elevated temperatures to assure adequate thermal contact between the housing and the boron nitride.

Observations of Ag diffusion in ion implanted SiC

DOE PAGES

Gerczak, Tyler J.; Leng, Bin; Sridharan, Kumar; ...

2015-03-17

The nature and magnitude of Ag diffusion in SiC has been a topic of interest in connection with the performance of tristructural isotropic (TRISO) coated particle fuel for high temperature gas-cooled nuclear reactors. Ion implantation diffusion couples have been revisited to continue developing a more complete understanding of Ag fission product diffusion in SiC. Ion implantation diffusion couples fabricated from single crystal 4H-SiC and polycrystalline 3C-SiC substrates and exposed to 1500–1625°C, were investigated in this study by transmission electron microscopy and secondary ion mass spectrometry (SIMS). The high dynamic range of SIMS allowed for multiple diffusion régimes to be investigated,more » including enhanced diffusion by implantation-induced defects and grain boundary (GB) diffusion in undamaged SiC. Lastly, estimated diffusion coefficients suggest GB diffusion in bulk SiC does not properly describe the release observed from TRISO fuel.« less

Fuel Property Determination of Biodiesel-Diesel Blends By Terahertz Spectrum

NASA Astrophysics Data System (ADS)

Zhao, Hui; Zhao, Kun; Bao, Rima

2012-05-01

The frequency-dependent absorption characteristics of biodiesel and its blends with conventional diesel fuel have been researched in the spectral range of 0.2-1.5 THz by the terahertz time-domain spectroscopy (THz-TDS). The absorption coefficient presented a regular increasing with biodiesel content. A nonlinear multivariate model that correlating cetane number and solidifying point of bio-diesel blends with absorption coefficient has been established, making the quantitative analysis of fuel properties simple. The results made the cetane number and solidifying point prediction possible by THz-TDS technology and indicated a bright future in practical application.

Fission Product Appearance Rate Coefficients in Design Basis Source Term Determinations - Past and Present

NASA Astrophysics Data System (ADS)

Perez, Pedro B.; Hamawi, John N.

2017-09-01

Nuclear power plant radiation protection design features are based on radionuclide source terms derived from conservative assumptions that envelope expected operating experience. Two parameters that significantly affect the radionuclide concentrations in the source term are failed fuel fraction and effective fission product appearance rate coefficients. Failed fuel fraction may be a regulatory based assumption such as in the U.S. Appearance rate coefficients are not specified in regulatory requirements, but have been referenced to experimental data that is over 50 years old. No doubt the source terms are conservative as demonstrated by operating experience that has included failed fuel, but it may be too conservative leading to over-designed shielding for normal operations as an example. Design basis source term methodologies for normal operations had not advanced until EPRI published in 2015 an updated ANSI/ANS 18.1 source term basis document. Our paper revisits the fission product appearance rate coefficients as applied in the derivation source terms following the original U.S. NRC NUREG-0017 methodology. New coefficients have been calculated based on recent EPRI results which demonstrate the conservatism in nuclear power plant shielding design.

Low-energy collisions between electrons and BeD+

NASA Astrophysics Data System (ADS)

Niyonzima, S.; Pop, N.; Iacob, F.; Larson, Å; Orel, A. E.; Mezei, J. Zs; Chakrabarti, K.; Laporta, V.; Hassouni, K.; Benredjem, D.; Bultel, A.; Tennyson, J.; Reiter, D.; Schneider, I. F.

2018-02-01

Multichannel quantum defect theory is applied in the treatment of the dissociative recombination and vibrational excitation processes for the BeD+ ion in the 24 vibrational levels of its ground electronic state ({{X}}{}1{{{Σ }}}+,{v}{{i}}+=0\\ldots 23). Three electronic symmetries of BeD** states ({}2{{\\Pi }}, {}2{{{Σ }}}+, and {}2{{Δ }}) are considered in the calculation of cross sections and the corresponding rate coefficients. The incident electron energy range is 10-5-2.7 eV and the electron temperature range is 100-5000 K. The vibrational dependence of these collisional processes is highlighted. The resulting data are useful in magnetic confinement fusion edge plasma modeling and spectroscopy, in devices with beryllium based main chamber materials, such as ITER and JET, and operating with the deuterium-tritium fuel mix. An extensive rate coefficients database is presented in graphical form and also by analytic fit functions whose parameters are tabulated in the supplementary material.

40 CFR 1066.950 - Fuel temperature profile.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Fuel temperature profile. 1066.950 Section 1066.950 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION... Test Procedures for Motor Vehicles § 1066.950 Fuel temperature profile. Develop fuel temperature...

Evaluation of friction heating in cavitating high pressure Diesel injector nozzles

NASA Astrophysics Data System (ADS)

Salemi, R.; Koukouvinis, P.; Strotos, G.; McDavid, R.; Wang, Lifeng; Li, Jason; Marengo, M.; Gavaises, M.

2015-12-01

Variation of fuel properties occurring during extreme fuel pressurisation in Diesel fuel injectors relative to those under atmospheric pressure and room temperature conditions may affect significantly fuel delivery, fuel injection temperature, injector durability and thus engine performance. Indicative results of flow simulations during the full injection event of a Diesel injector are presented. In addition to the Navier-Stokes equations, the enthalpy conservation equation is considered for predicting the fuel temperature. Cavitation is simulated using an Eulerian-Lagrangian cavitation model fully coupled with the flow equations. Compressible bubble dynamics based on the R-P equation also consider thermal effects. Variable fuel properties function of the local pressure and temperature are taken from literature and correspond to a reference so-called summer Diesel fuel. Fuel pressurisation up to 3000bar pressure is considered while various wall temperature boundary conditions are tested in order to compare their effect relative to those of the fuel heating caused during the depressurisation of the fuel as it passes through the injection orifices. The results indicate formation of strong temperature gradients inside the fuel injector while heating resulting from the extreme friction may result to local temperatures above the fuel's boiling point. Predictions indicate bulk fuel temperature increase of more than 100°C during the opening phase of the needle valve. Overall, it is concluded that such effects are significant for the injector performance and should be considered in relevant simulation tools.

Temperature and flow measurements on near-freezing aviation fuels in a wing-tank model

NASA Technical Reports Server (NTRS)

Friedman, R.; Stockemer, F. J.

1980-01-01

Freezing behavior, pumpability, and temperature profiles for aviation turbine fuels were measured in a 190-liter tank chilled to simulate internal temperature gradients encountered in commercial airplane wing tanks. When the bulk of the fuel was above the specification freezing point, pumpout of the fuel removed all fuel except a layer adhering to the bottom chilled surfaces, and the unpumpable fraction depended on the fuel temperature near these surfaces. When the bulk of the fuel was at or below the freezing point, pumpout ceased when solids blocked the pump inlet, and the unpumpable fraction depended on the overall average temperature.

Nuclear fuels for very high temperature applications

NASA Astrophysics Data System (ADS)

Lundberg, L. B.; Hobbins, R. R.

The success of the development of nuclear thermal propulsion devices and thermionic space nuclear power generation systems depends on the successful utilization of nuclear fuel materials at temperatures in the range 2000 to 3500 K. Problems associated with the utilization of uranium bearing fuel materials at these very high temperatures while maintaining them in the solid state for the required operating times are addressed. The critical issues addressed include evaporation, melting, reactor neutron spectrum, high temperature chemical stability, fabrication, fission induced swelling, fission product release, high temperature creep, thermal shock resistance, and fuel density, both mass and fissile atom. Candidate fuel materials for this temperature range are based on UO2 or uranium carbides. Evaporation suppression, such as a sealed cladding, is required for either fuel base. Nuclear performance data needed for design are sparse for all candidate fuel forms in this temperature range, especially at the higher temperatures.

Unravelling the Chemical Complexity of Biomass Burning VOC Emissions via H3O+ ToF-CIMS: Separation of High- and Low-temperature Pyrolysis Products

NASA Astrophysics Data System (ADS)

Sekimoto, K.; Koss, A.; Gilman, J.; Selimovic, V.; Coggon, M.; Zarzana, K. J.; Yuan, B.; Lerner, B. M.; Brown, S. S.; Warneke, C.; Yokelson, R. J.; De Gouw, J. A.

2017-12-01

Biomass burning is a large source of volatile organic compounds (VOCs) and many other trace species to the atmosphere. These VOCs can act as precursors to formation of secondary pollutants such as ozone and fine particles, and some VOCs can also have direct effects on human and ecosystem health. Multiple different and complex processes take place in biomass burning, e.g., distillation, flaming, and smoldering combustion processes. In a given fire, most of these processes occur simultaneously, but the relative importance of each can change over the course of a fire. This gives rise to some of the variability in VOC emissions between different fires. To study gas-phase emissions from biomass burning, an H3O+ ToF-CIMS was deployed during the FIREX 2016 laboratory intensive at the US Forest Service Fire Sciences Laboratory in Missoula, Montana. This instrument has a fast time response and the measurements in stack burns show the varying gas-phase emissions as the mix of distillation, flaming, and smoldering varies. We used positive matrix factorization (PMF) to reduce and explain the observed chemical complexity in the gas phase. Despite the complexity and variability of emissions, we found that a solution including just two emission profiles explained on average 85% of the VOC emissions across 15 different fuel types including pines, firs, spruce, grass, shrubs, chaparrals, and wood wool. We identified the two profiles as resulting from high-temperature and low-temperature pyrolysis processes, and found that the profiles were remarkably similar (correlation coefficient r > 0.9) across nearly all the fuel types described above. Some of the remaining differences in VOC emission profiles between fuel types, and exceptions to the two-profile solution, can be explained by differences in the chemical composition of the fuels.

Improved engine performance via use of nickel ceramic composite coatings (NCC coat)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Funatani, K.; Kurosawa, K.; Fabiyi, P.A.

1994-09-01

In seeking to produce lightweight aluminum block based engines, a variety of metallurgical and surface modification techniques for cylinder bores, pistons and piston rings are available. This paper discusses these various alternative methods while placing particular emphasis on electroplated nickel ceramic composite coatings (NCC). NCC Coating properties are characterized by high hardness, high corrosion resistance, high temperature wear and scuff resistance and low frictional coefficients. The application of NCC Coatings in 2-stroke motorcycle and diesel engines has resulted in benefits in the following areas: elimination of cast iron liners; reduced cylinder wall temperature, engine weight and increased power; lowering ofmore » oil consumption; improved fuel economy; reduction in emissions; improved scuff and wear resistance on cylinder bores, pistons and piston rings; friction reduction; combating of piston ring groove microwelding and pound out; thermal barrier protection on diesel piston domes; reduction in carbon deposition on piston domes; reduced noise from piston slap; and ability to operate in corrosive environments. The sum of the above stated benefits holds much potential for contributing towards greater flexibility in materials selection for the design of lightweight, fuel efficient vehicles based upon the use of aluminum engines. 13 refs., 13 figs.« less

Effect of Fuel Temperature Profile on Eigenvalue Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greifenkamp, Tom E; Clarno, Kevin T; Gehin, Jess C

2008-01-01

Use of an average fuel temperature is a current practice when modeling fuel for eigenvalue (k-inf) calculations. This is an approximation, as it is known from Heat-transfer methods that a fuel pin having linear power q', will have a temperature that varies radially and has a maximum temperature at the center line [1]. This paper describes an investigation into the effects on k-inf and isotopic concentrations of modeling a fuel pin using a single average temperature versus a radially varying fuel temperature profile. The axial variation is not discussed in this paper. A single fuel pin was modeled having 1,more » 3, 5, 8, or 10 regions of equal volumes (areas). Fig. 1 shows a model of a 10-ring fuel pin surrounded by a gap and then cladding.« less

Neutronic analysis of candidate accident-tolerant cladding concepts in pressurized water reactors

DOE PAGES

George, Nathan Michael; Terrani, Kurt A.; Powers, Jeffrey J.; ...

2014-09-29

A study analyzed the neutronics of alternate cladding materials in a pressurized water reactor (PWR) environment. Austenitic type 310 (310SS) and 304 stainless steels, ferritic Fe-20Cr-5Al (FeCrAl) and APMT™ alloys, and silicon carbide (SiC)-based materials were considered and compared with Zircaloy-4. SCALE 6.1 was used to analyze the associated neutronics penalty/advantage, changes in reactivity coefficients, and spectral variations once a transition in the cladding was made. In the cases examined, materials containing higher absorbing isotopes invoked a reduction in reactivity due to an increase in neutron absorption in the cladding. Higher absorbing materials produced a harder neutron spectrum in themore » fuel pellet, leading to a slight increase in plutonium production. A parametric study determined the geometric conditions required to match cycle length requirements for each alternate cladding material in a PWR. A method for estimating the end of cycle reactivity was implemented to compare each model to that of standard Zircaloy-4 cladding. By using a thinner cladding of 350 μm and keeping a constant outer diameter, austenitic stainless steels require an increase of no more than 0.5 wt% enriched 235U to match fuel cycle requirements, while the required increase for FeCrAl was about 0.1%. When modeling SiC (with slightly lower thermal absorption properties than that of Zircaloy), a standard cladding thickness could be implemented with marginally less enriched uranium (~0.1%). Moderator temperature and void coefficients were calculated throughout the depletion cycle. Nearly identical reactivity responses were found when coolant temperature and void properties were perturbed for each cladding material. By splitting the pellet into 10 equal areal sections, relative fission power as a function of radius was found to be similar for each cladding material. FeCrAl and 310SS cladding have a slightly higher fission power near the pellet’s periphery due to the harder neutron spectrum in the system, causing more 239Pu breeding. An economic assessment calculated the change in fuel pellet production costs for use of each cladding. Furthermore, implementing FeCrAl alloys would increase fuel pellet production costs about 15% because of increased 235U enrichment and the additional UO 2 pellet volume enabled by using thinner cladding.« less

Dynamic evaluation of low-temperature metal-supported solid oxide fuel cell oriented to auxiliary power units

NASA Astrophysics Data System (ADS)

Wang, Zhenwei; Berghaus, Jörg Oberste; Yick, Sing; Decès-Petit, Cyrille; Qu, Wei; Hui, Rob; Maric, Radenka; Ghosh, Dave

A metal-supported solid oxide fuel cell (SOFC) composed of a Ni-Ce 0.8Sm 0.2O 2- δ (Ni-SDC) cermet anode and an SDC electrolyte was fabricated by suspension plasma spraying on a Hastelloy X substrate. The cathode, an Sm 0.5Sr 0.5CoO 3 (SSCo)-SDC composite, was screen-printed and fired in situ. The dynamic behaviour of the cell was measured while subjected to complete fuel shutoff and rapid start-up cycles, as typically encountered in auxiliary power units (APU) applications. A promising performance - with a maximum power density (MPD) of 0.176 W cm -2 at 600 °C - was achieved using humidified hydrogen as fuel and air as the oxidant. The cell also showed excellent resistance to oxidation at 600 °C during fuel shutoff, with only a slight drop in performance after reintroduction of the fuel. The Cr and Mn species in the Hastelloy X alloy appeared to be preferentially oxidized while the oxidation of nickel in the metallic substrate was temporarily alleviated. In rapid start-up cycles with a heating rate of 60 °C min -1, noticeable performance deterioration took place in the first two thermal cycles, and then continued at a much slower rate in subsequent cycles. A postmortem analysis of the cell suggested that the degradation was mainly due to the mismatch of the thermal expansion coefficient across the cathode/electrolyte interface.

Effect of sorbed methanol, current, and temperature on multicomponent transport in nafion-based direct methanol fuel cells.

PubMed

Rivera, Harry; Lawton, Jamie S; Budil, David E; Smotkin, Eugene S

2008-07-24

The CO2 in the cathode exhaust of a liquid feed direct methanol fuel cell (DMFC) has two sources: methanol diffuses through the membrane electrode assembly (MEA) to the cathode where it is catalytically oxidized to CO2; additionally, a portion of the CO2 produced at the anode diffuses through the MEA to the cathode. The potential-dependent CO2 exhaust from the cathode was monitored by online electrochemical mass spectrometry (ECMS) with air and with H2 at the cathode. The precise determination of the crossover rates of methanol and CO2, enabled by the subtractive normalization of the methanol/air to the methanol/H2 ECMS data, shows that methanol decreases the membrane viscosity and thus increases the diffusion coefficients of sorbed membrane components. The crossover of CO2 initially increases linearly with the Faradaic oxidation of methanol, reaches a temperature-dependent maximum, and then decreases. The membrane viscosity progressively increases as methanol is electrochemically depleted from the anode/electrolyte interface. The crossover maximum occurs when the current dependence of the diffusion coefficients and membrane CO2 solubility dominate over the Faradaic production of CO2. The plasticizing effect of methanol is corroborated by measurements of the rotational diffusion of TEMPONE (2,2,6,6-tetramethyl-4-piperidone N-oxide) spin probe by electron spin resonance spectroscopy. A linear inverse relationship between the methanol crossover rate and current density confirms the absence of methanol electro-osmotic drag at concentrations relevant to operating DMFCs. The purely diffusive transport of methanol is explained in terms of current proton solvation and methanol-water incomplete mixing theories.

High Power Density Motors

NASA Technical Reports Server (NTRS)

Kascak, Daniel J.

2004-01-01

With the growing concerns of global warming, the need for pollution-free vehicles is ever increasing. Pollution-free flight is one of NASA's goals for the 21" Century. , One method of approaching that goal is hydrogen-fueled aircraft that use fuel cells or turbo- generators to develop electric power that can drive electric motors that turn the aircraft's propulsive fans or propellers. Hydrogen fuel would likely be carried as a liquid, stored in tanks at its boiling point of 20.5 K (-422.5 F). Conventional electric motors, however, are far too heavy (for a given horsepower) to use on aircraft. Fortunately the liquid hydrogen fuel can provide essentially free refrigeration that can be used to cool the windings of motors before the hydrogen is used for fuel. Either High Temperature Superconductors (HTS) or high purity metals such as copper or aluminum may be used in the motor windings. Superconductors have essentially zero electrical resistance to steady current. The electrical resistance of high purity aluminum or copper near liquid hydrogen temperature can be l/lOO* or less of the room temperature resistance. These conductors could provide higher motor efficiency than normal room-temperature motors achieve. But much more importantly, these conductors can carry ten to a hundred times more current than copper conductors do in normal motors operating at room temperature. This is a consequence of the low electrical resistance and of good heat transfer coefficients in boiling LH2. Thus the conductors can produce higher magnetic field strengths and consequently higher motor torque and power. Designs, analysis and actual cryogenic motor tests show that such cryogenic motors could produce three or more times as much power per unit weight as turbine engines can, whereas conventional motors produce only 1/5 as much power per weight as turbine engines. This summer work has been done with Litz wire to maximize the current density. The current is limited by the amount of heat it generates. By increasing the heat transfer out of the wire, the wires can carry a larger current and therefore produce more force. This was done by increasing the surface area of the wire to allow more coolant to flow over it. Litz wire was used because it can carry high frequency current. It also can be deformed into configurations that would increase the surface area. The best configuration was determined by heat transfer and force plots that were generated using Maxwell 2D. Future work will be done by testing and measuring the thrust force produced by the wires in a magnetic field.

Temperatures and Stresses on Hollow Blades For Gas Turbines

NASA Technical Reports Server (NTRS)

Pollmann, Erich

1947-01-01

The present treatise reports on theoretical investigations and test-stand measurements which were carried out in the BMW Flugmotoren GMbH in developing the hollow blade for exhaust gas turbines. As an introduction the temperature variation and the stress on a turbine blade for a gas temperature of 900 degrees and circumferential velocities of 600 meters per second are discussed. The assumptions onthe heat transfer coefficients at the blade profile are supported by tests on an electrically heated blade model. The temperature distribution in the cross section of a blade Is thoroughly investigated and the temperature field determined for a special case. A method for calculation of the thermal stresses in turbine blades for a given temperature distribution is indicated. The effect of the heat radiation on the blade temperature also is dealt with. Test-stand experiments on turbine blades are evaluated, particularly with respect to temperature distribution in the cross section; maximum and minimum temperature in the cross section are ascertained. Finally, the application of the hollow blade for a stationary gas turbine is investigated. Starting from a setup for 550 C gas temperature the improvement of the thermal efficiency and the fuel consumption are considered as well as the increase of the useful power by use of high temperatures. The power required for blade cooling is taken into account.

Use of multi-functional flexible micro-sensors for in situ measurement of temperature, voltage and fuel flow in a proton exchange membrane fuel cell.

PubMed

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 μm-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased.

Composite coatings improve engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Funatani, K.; Kurosawa, K.

1994-12-01

About 40% of the power loss in engine systems is attributed to the adverse effects of friction in reciprocating engine components. Over half of this power loss is caused by friction between pistons, piston rings, and cylinder bores. In addition, engine parts may be attacked by corrosive gasoline substitutes such as liquid propane gas and alcohol/gasoline mixtures. To solve both friction and corrosion problems, Nihon Parkerizing Co. has improved the nickel-phosphorus based ceramic composite (NCC) plating technology that was developed for cylinder bores and pistons by Suzuki Motor Co. in the mid 1970s. Iron and nickel-based composite plating technologies havemore » been investigated since the early 1970s, and a few have been used on small two-stroke motorcycle, outboard marine, snowmobile, and some luxury passenger car engine components. Both nickel- and iron-base plating processes are used on cylinders and pistons because they offer excellent wear and corrosion resistance. Nickel-base films have higher corrosion resistance than those based on iron, and are capable of withstanding the corrosive conditions characteristic of high methanol fuels. Unfortunately, they experience a decrease in hardness as operating temperatures increase. However, NCC coatings with phosphorus additions have high hardness even under severe operating conditions, and hardness increases upon exposure to elevated temperatures. In addition to high hardness and corrosion resistance, NCC coatings provide a low friction coefficient, which contributes to the reduction of friction losses between sliding components. When used in low-quality or alcohol fuels, the corrosion resistance of NCC coatings is far higher than that of Fe-P plating. Additionally, the coatings reduce wall and piston temperature, wear of ring groove and skirt, and carbon deposit formation, and they improve output power and torque. These advantages all contribute to the development of light and efficient engines with better fuel mileage.« less

Planar solid oxide fuel cell with staged indirect-internal air and fuel preheating and reformation

DOEpatents

Geisbrecht, Rodney A; Williams, Mark C

2003-10-21

A solid oxide fuel cell arrangement and method of use that provides internal preheating of both fuel and air in order to maintain the optimum operating temperature for the production of energy. The internal preheat passes are created by the addition of two plates, one on either side of the bipolar plate, such that these plates create additional passes through the fuel cell. This internal preheat fuel cell configuration and method reduce the requirements for external heat exchanger units and air compressors. Air or fuel may be added to the fuel cell as required to maintain the optimum operating temperature through a cathode control valve or an anode control valve, respectively. A control loop comprises a temperature sensing means within the preheat air and fuel passes, a means to compare the measured temperature to a set point temperature and a determination based on the comparison as to whether the control valves should allow additional air or fuel into the preheat or bypass manifolds of the fuel cell.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gardiner, D. P.; Bardon, M. F.; Clark, W.

This study assessed differences in headspace flammability for summertime gasolines and new high-ethanol content fuel blends. The results apply to vehicle fuel tanks and underground storage tanks. Ambient temperature and fuel formulation effects on headspace vapor flammability of ethanol/gasoline blends were evaluated. Depending on the degree of tank filling, fuel type, and ambient temperature, fuel vapors in a tank can be flammable or non-flammable. Pure gasoline vapors in tanks generally are too rich to be flammable unless ambient temperatures are extremely low. High percentages of ethanol blended with gasoline can be less volatile than pure gasoline and can produce flammablemore » headspace vapors at common ambient temperatures. The study supports refinements of fuel ethanol volatility specifications and shows potential consequences of using noncompliant fuels. E85 is flammable at low temperatures; denatured ethanol is flammable at warmer temperatures. If both are stored at the same location, one or both of the tanks' headspace vapors will be flammable over a wide range of ambient temperatures. This is relevant to allowing consumers to splash -blend ethanol and gasoline at fueling stations. Fuels compliant with ASTM volatility specifications are relatively safe, but the E85 samples tested indicate that some ethanol fuels may produce flammable vapors.« less

High freezing point fuels used for aviation turbine engines

NASA Technical Reports Server (NTRS)

Friedman, R.

1979-01-01

Broadened-specification aviation fuels could be produced from a greater fraction of crude source material with improvements in fuel supply and price. These fuels, particularly those with increased final boiling temperatures, would have higher freezing temperatures than current aviation turbine fuels. For the small but significant fraction of commercial flights where low fuel temperatures make higher freezing-point fuel use unacceptable, adaptations to the fuel or fuel system may be made to accommodate this fuel. Several techniques are discussed. Fuel heating is the most promising concept. One simple design uses existing heat rejection from the fuel-lubricating oil cooler, another uses an engine-driven generator for electrical heating.

Effect of increased fuel temperature on emissions of oxides of nitrogen from a gas turbine combustor burning natural gas

NASA Technical Reports Server (NTRS)

Marchionna, N. R.

1973-01-01

An annular gas turbine combustor was tested with heated natural gas fuel to determine the effect of increasing fuel temperature on the formation of oxides of nitrogen. Fuel temperatures ranged from ambient to 800 K (980 F). Combustor pressure was 6 atmospheres and the inlet air temperature ranged from 589 to 894 K (600 to 1150 F). The NOx emission index increased with fuel temperature at a rate of 4 to 9 percent per 100 K (180 F), depending on the inlet air temperature. The rate of increase in NOx was lowest at the highest inlet air temperature tested.

Leaner Lifted-Flame Combustion Enabled by the Use of an Oxygenated Fuel in an Optical CI Engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gehmlich, Ryan K.; Dumitrescu, Cosmin E.; Wang, Yefu

Leaner lifted-flame combustion (LLFC) is a mixing-controlled combustion strategy for compression-ignition engines that does not produce soot because the equivalence ratio at the lift-off length, Φ(H), is less than or equal to approximately two. In addition to preventing soot formation, LLFC can simultaneously control emissions of nitrogen oxides because it is tolerant to the use of exhaust-gas recirculation for lowering in-cylinder temperatures. LLFC can be achieved through the use of oxygenated fuels and enhanced fuel/charge-gas mixing upstream of the lift-off length. Enhanced mixing can be obtained via higher injection pressures, smaller injector orifice diameters, lower intake-manifold and coolant temperatures, and/ormore » more retarded injection timings. This study focuses on the effects of an oxygenated fuel blend (T50) made up of 50% by volume tri-propylene glycol mono-methyl ether with a #2 ULSD emissions-certification fuel (CFA), compared against baseline testing of the CFA fuel without the oxygenate. Experimental measurements include crank-angle resolved natural luminosity (NL) and chemiluminescence (CL) imaging diagnostics. EGR is simulated by adding nitrogen and carbon dioxide to the intake charge to produce a 16% intake-oxygen mole fraction (XO2), and results are compared against cases with no charge dilution (i.e., 21% XO2). Initial experiments with a two-hole tip achieved soot-free LLFC at low loads with the T50 fuel, 240 MPa injection pressure, 50 °C intake-manifold temperature (IMT), 95 °C coolant temperature, and -5 crank-angle degree (CAD) after top-dead-center (ATDC) start of combustion (SOC) timing. The strategy was extended to more moderate loads by employing a 6-hole injector tip, where lowering the IMT to 30 °C, reducing the coolant temperature to 85 °C, and retarding the SOC timing to +5 CAD ATDC resulted in sustained LLFC at both 21% and 16% XO2 at up to 6.2 bar gross indicated mean effective pressure (gIMEP) with T50. The achievement of LLFC was confirmed by independent soot measurements using a smoke meter, spatially integrated natural luminosity from the NL diagnostics, and laser-induced incandescence for measuring soot volume fraction in the exhaust stream. In contrast to the results with T50, LLFC was not achieved under any of the test conditions with CFA. Combustion was stable under LLFC conditions, with a coefficient of variation of gIMEP less than 1.5%. Nitrogen oxides and hydrocarbon emissions were also lowered by up to 25% each for LLFC with T50 relative to using the same operating conditions with CFA. Combustion noise was similarly reduced by 4-6 dBA, and ringing intensity by 60-80%, for LLFC with T50.« less

Leaner Lifted-Flame Combustion Enabled by the Use of an Oxygenated Fuel in an Optical CI Engine

DOE PAGES

Gehmlich, Ryan K.; Dumitrescu, Cosmin E.; Wang, Yefu; ...

2016-04-05

Leaner lifted-flame combustion (LLFC) is a mixing-controlled combustion strategy for compression-ignition engines that does not produce soot because the equivalence ratio at the lift-off length, Φ(H), is less than or equal to approximately two. In addition to preventing soot formation, LLFC can simultaneously control emissions of nitrogen oxides because it is tolerant to the use of exhaust-gas recirculation for lowering in-cylinder temperatures. LLFC can be achieved through the use of oxygenated fuels and enhanced fuel/charge-gas mixing upstream of the lift-off length. Enhanced mixing can be obtained via higher injection pressures, smaller injector orifice diameters, lower intake-manifold and coolant temperatures, and/ormore » more retarded injection timings. This study focuses on the effects of an oxygenated fuel blend (T50) made up of 50% by volume tri-propylene glycol mono-methyl ether with a #2 ULSD emissions-certification fuel (CFA), compared against baseline testing of the CFA fuel without the oxygenate. Experimental measurements include crank-angle resolved natural luminosity (NL) and chemiluminescence (CL) imaging diagnostics. EGR is simulated by adding nitrogen and carbon dioxide to the intake charge to produce a 16% intake-oxygen mole fraction (XO2), and results are compared against cases with no charge dilution (i.e., 21% XO2). Initial experiments with a two-hole tip achieved soot-free LLFC at low loads with the T50 fuel, 240 MPa injection pressure, 50 °C intake-manifold temperature (IMT), 95 °C coolant temperature, and -5 crank-angle degree (CAD) after top-dead-center (ATDC) start of combustion (SOC) timing. The strategy was extended to more moderate loads by employing a 6-hole injector tip, where lowering the IMT to 30 °C, reducing the coolant temperature to 85 °C, and retarding the SOC timing to +5 CAD ATDC resulted in sustained LLFC at both 21% and 16% XO2 at up to 6.2 bar gross indicated mean effective pressure (gIMEP) with T50. The achievement of LLFC was confirmed by independent soot measurements using a smoke meter, spatially integrated natural luminosity from the NL diagnostics, and laser-induced incandescence for measuring soot volume fraction in the exhaust stream. In contrast to the results with T50, LLFC was not achieved under any of the test conditions with CFA. Combustion was stable under LLFC conditions, with a coefficient of variation of gIMEP less than 1.5%. Nitrogen oxides and hydrocarbon emissions were also lowered by up to 25% each for LLFC with T50 relative to using the same operating conditions with CFA. Combustion noise was similarly reduced by 4-6 dBA, and ringing intensity by 60-80%, for LLFC with T50.« less

Experimental Study of Fuel Heating at Low Temperatures in a Wing Tank Model, Volume 1

NASA Technical Reports Server (NTRS)

Stockemer, F. J.

1981-01-01

Scale model fuel heating systems for use with aviation hydrocarbon fuel at low temperatures were investigated. The effectiveness of the heating systems in providing flowability and pumpability at extreme low temperature when some freezing of the fuel would otherwise occur is evaluated. The test tank simulated a section of an outer wing tank, and was chilled on the upper and lower surfaces. Turbine engine lubricating oil was heated, and recirculating fuel transferred the heat. Fuels included: a commercial Jet A; an intermediate freeze point distillate; a higher freeze point distillate blended according to Experimental Referee Broadened Specification guidelines; and a higher freeze point paraffinic distillate used in a preceding investigation. Each fuel was chilled to selected temperature to evaluate unpumpable solid formation (holdup). Tests simulating extreme cold weather flight, without heating, provided baseline fuel holdup data. Heating and recirculating fuel increased bulk temperature significantly; it had a relatively small effect on temperature near the bottom of the tank. Methods which increased penetration of heated fuel into the lower boundary layer improved the capability for reducing holdup.

Measurement and correlation of jet fuel viscosities at low temperatures

NASA Technical Reports Server (NTRS)

Schruben, D. L.

1985-01-01

Apparatus and procedures were developed to measure jet fuel viscosity for eight current and future jet fuels at temperatures from ambient to near -60 C by shear viscometry. Viscosity data showed good reproducibility even at temperatures a few degrees below the measured freezing point. The viscosity-temperature relationship could be correlated by two linear segments when plotted as a standard log-log type representation (ASTM D 341). At high temperatures, the viscosity-temperature slope is low. At low temperatures, where wax precipitation is significant, the slope is higher. The breakpoint between temperature regions is the filter flow temperature, a fuel characteristic approximated by the freezing point. A generalization of the representation for the eight experimental fuels provided a predictive correlation for low-temperature viscosity, considered sufficiently accurate for many design or performance calculations.

Ambient Temperature, Fuel Economy, Emissions, and Trip Length

DOT National Transportation Integrated Search

1979-08-01

This report examines the relationship among automotive fuel economy, ambient temperature, cold-start trip length, and drive-train component temperatures of four 1977 vehicles. Fuel economy, exhaust emission, and drive-train temperatures were measured...

A User Guide to PARET/ANL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olson, A. P.; Dionne, B.; Marin-Lafleche, A.

2015-01-01

PARET was originally created in 1969 at what is now Idaho National Laboratory (INL), to analyze reactivity insertion events in research and test reactor cores cooled by light or heavy water, with fuel composed of either plates or pins. The use of PARET is also appropriate for fuel assemblies with curved fuel plates when their radii of curvatures are large with respect to the fuel plate thickness. The PARET/ANL version of the code has been developed at Argonne National Laboratory (ANL) under the sponsorship of the U.S. Department of Energy/NNSA, and has been used by the Reactor Conversion Program tomore » determine the expected transient behavior of a large number of reactors. PARET/ANL models the various fueled regions of a reactor core as channels. Each of these channels consists of a single flat fuel plate/pin (including cladding and, optionally, a gap) with water coolant on each side. In slab geometry the coolant channels for a given fuel plate are of identical dimensions (mirror symmetry), but they can be of different thickness in each channel. There can be many channels, but each channel is independent and coupled only through reactivity feedback effects to the whole core. The time-dependent differential equations that represent the system are replaced by an equivalent set of finite-difference equations in space and time, which are integrated numerically. PARET/ANL uses fundamentally the same numerical scheme as RELAP5 for the time-integration of the point-kinetics equations. The one-dimensional thermal-hydraulic model includes temperature-dependent thermal properties of the solid materials, such as heat capacity and thermal conductivity, as well as the transient heat production and heat transfer from the fuel meat to the coolant. Temperature- and pressure-dependent thermal properties of the coolant such as enthalpy, density, thermal conductivity, and viscosity are also used in determining parameters such as friction factors and heat transfer coefficients. The code first determines the steady-state solution for the initial state. Then the solution of the transient is obtained by integration in time and space. Multiple heat transfer, DNB and flow instability correlations are available. The code was originally developed to model reactors cooled by an open loop, which was adequate for rapid transients in pool-type cores. An external loop model appropriate for Miniature Neutron Source Reactors (MNSR’s) was also added to PARET/ANL to model natural circulation within the vessel, heat transfer from the vessel to pool and heat loss by evaporation from the pool. PARET/ANL also contains models for decay heat after shutdown, control rod reactivity versus time or position, time-dependent pump flow, and loss-of-flow event with flow reversal as well as logic for trips on period, power, and flow. Feedback reactivity effects from coolant density changes and temperature changes are represented by tables. Feedback reactivity from fuel heat-up (Doppler Effect) is represented by a four-term polynomial in powers of fuel temperature. Photo-neutrons produced in beryllium or in heavy water may be included in the point-kinetics equations by using additional delayed neutron groups.« less

Control apparatus and method for efficiently heating a fuel processor in a fuel cell system

DOEpatents

Doan, Tien M.; Clingerman, Bruce J.

2003-08-05

A control apparatus and method for efficiently controlling the amount of heat generated by a fuel cell processor in a fuel cell system by determining a temperature error between actual and desired fuel processor temperatures. The temperature error is converted to a combustor fuel injector command signal or a heat dump valve position command signal depending upon the type of temperature error. Logic controls are responsive to the combustor fuel injector command signals and the heat dump valve position command signal to prevent the combustor fuel injector command signal from being generated if the heat dump valve is opened or, alternately, from preventing the heat dump valve position command signal from being generated if the combustor fuel injector is opened.

Advanced fuel system technology for utilizing broadened property aircraft fuels

NASA Technical Reports Server (NTRS)

Reck, G. M.

1980-01-01

Factors which will determine the future supply and cost of aviation turbine fuels are discussed. The most significant fuel properties of volatility, fluidity, composition, and thermal stability are discussed along with the boiling ranges of gasoline, naphtha jet fuels, kerosene, and diesel oil. Tests were made to simulate the low temperature of an aircraft fuel tank to determine fuel tank temperatures for a 9100-km flight with and without fuel heating; the effect of N content in oil-shale derived fuels on the Jet Fuel Thermal Oxidation Tester breakpoint temperature was measured. Finally, compatibility of non-metallic gaskets, sealants, and coatings with increased aromatic content jet fuels was examined.

Use of Multi-Functional Flexible Micro-Sensors for in situ Measurement of Temperature, Voltage and Fuel Flow in a Proton Exchange Membrane Fuel Cell

PubMed Central

Lee, Chi-Yuan; Chan, Pin-Cheng; Lee, Chung-Ju

2010-01-01

Temperature, voltage and fuel flow distribution all contribute considerably to fuel cell performance. Conventional methods cannot accurately determine parameter changes inside a fuel cell. This investigation developed flexible and multi-functional micro sensors on a 40 μm-thick stainless steel foil substrate by using micro-electro-mechanical systems (MEMS) and embedded them in a proton exchange membrane fuel cell (PEMFC) to measure the temperature, voltage and flow. Users can monitor and control in situ the temperature, voltage and fuel flow distribution in the cell. Thereby, both fuel cell performance and lifetime can be increased. PMID:22163545

System for controlling the operating temperature of a fuel cell

DOEpatents

Fabis, Thomas R.; Makiel, Joseph M.; Veyo, Stephen E.

2006-06-06

A method and system are provided for improved control of the operating temperature of a fuel cell (32) utilizing an improved temperature control system (30) that varies the flow rate of inlet air entering the fuel cell (32) in response to changes in the operating temperature of the fuel cell (32). Consistent with the invention an improved temperature control system (30) is provided that includes a controller (37) that receives an indication of the temperature of the inlet air from a temperature sensor (39) and varies the heat output by at least one heat source (34, 36) to maintain the temperature of the inlet air at a set-point T.sub.inset. The controller (37) also receives an indication of the operating temperature of the fuel cell (32) and varies the flow output by an adjustable air mover (33), within a predetermined range around a set-point F.sub.set, in order to maintain the operating temperature of the fuel cell (32) at a set-point T.sub.opset.

Comparison of rotational temperature derived from ground-based OH airglow observations with TIMED/SABER to evaluate the Einstein Coefficients

NASA Astrophysics Data System (ADS)

Liu, W.; Xu, J.; Smith, A. K.; Yuan, W.

2017-12-01

Ground-based observations of the OH(9-4, 8-3, 6-2, 5-1, 3-0) band airglows over Xinglong, China (40°24'N, 117°35'E) from December 2011 to 2014 are used to calculate rotational temperatures. The temperatures are calculated using five commonly used Einstein coefficient datasets. The kinetic temperature from TIMED/SABER is completely independent of the OH rotational temperature. SABER temperatures are weighted vertically by weighting functions calculated for each emitting vibrational state from two SABER OH volume emission rate profiles. By comparing the ground-based OH rotational temperature with SABER's, five Einstein coefficient datasets are evaluated. The results show that temporal variations of the rotational temperatures are well correlated with SABER's; the linear correlation coefficients are higher than 0.72, but the slopes of the fit between the SABER and rotational temperatures are not equal to 1. The rotational temperatures calculated using each set of Einstein coefficients produce a different bias with respect to SABER; these are evaluated over each of vibrational levels to assess the best match. It is concluded that rotational temperatures determined using any of the available Einstein coefficient datasets have systematic errors. However, of the five sets of coefficients, the rotational temperature derived with the Langhoff et al.'s (1986) set is most consistent with SABER. In order to get a set of optimal Einstein coefficients for rotational temperature derivation, we derive the relative values from ground-based OH spectra and SABER temperatures statistically using three year data. The use of a standard set of Einstein coefficients will be beneficial for comparing rotational temperatures observed at different sites.

Preliminary analysis of hot spot factors in an advanced reactor for space electric power systems

NASA Technical Reports Server (NTRS)

Lustig, P. H.; Holms, A. G.; Davison, H. W.

1973-01-01

The maximum fuel pin temperature for nominal operation in an advanced power reactor is 1370 K. Because of possible nitrogen embrittlement of the clad, the fuel temperature was limited to 1622 K. Assuming simultaneous occurrence of the most adverse conditions a deterministic analysis gave a maximum fuel temperature of 1610 K. A statistical analysis, using a synthesized estimate of the standard deviation for the highest fuel pin temperature, showed probabilities of 0.015 of that pin exceeding the temperature limit by the distribution free Chebyshev inequality and virtually nil assuming a normal distribution. The latter assumption gives a 1463 K maximum temperature at 3 standard deviations, the usually assumed cutoff. Further, the distribution and standard deviation of the fuel-clad gap are the most significant contributions to the uncertainty in the fuel temperature.

40 CFR 600.107-08 - Fuel specifications.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Exhaust Emission Test Procedures § 600.107-08 Fuel specifications. (a) The test fuel specifications for... given in paragraph (b) of this section. (b)(1) Diesel test fuel used for cold temperature FTP testing... alternative fuel for cold temperature FTP testing. (c) Test fuels representing fuel types for which there are...

40 CFR 600.107-08 - Fuel specifications.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Exhaust Emission Test Procedures § 600.107-08 Fuel specifications. (a) The test fuel specifications for... given in paragraph (b) of this section. (b)(1) Diesel test fuel used for cold temperature FTP testing... alternative fuel for cold temperature FTP testing. (c) Test fuels representing fuel types for which there are...

40 CFR 600.107-08 - Fuel specifications.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Exhaust Emission Test Procedures § 600.107-08 Fuel specifications. (a) The test fuel specifications for... given in paragraph (b) of this section. (b)(1) Diesel test fuel used for cold temperature FTP testing... alternative fuel for cold temperature FTP testing. (c) Test fuels representing fuel types for which there are...

Combustion characteristics of gas turbine alternative fuels

NASA Technical Reports Server (NTRS)

Rollbuhler, R. James

1987-01-01

An experimental investigation was conducted to obtain combustion performance values for specific heavyend, synthetic hydrocarbon fuels. A flame tube combustor modified to duplicate an advanced gas turbine engine combustor was used for the tests. Each fuel was tested at steady-state operating conditions over a range of mass flow rates, fuel-to-air mass ratio, and inlet air temperatures. The combustion pressure, as well as the hardware, were kept nearly constant over the program test phase. Test results were obtained in regards to geometric temperature pattern factors as a function of combustor wall temperatures, the combustion gas temperature, and the combustion emissions, both as affected by the mass flow rate and fuel-to-air ratio. The synthetic fuels were reacted in the combustor such that for most tests their performance was as good, if not better, than the baseline gasoline or diesel fuel tests. The only detrimental effects were that at high inlet air temperature conditions, fuel decomposition occurred in the fuel atomizing nozzle passages resulting in blockage. And the nitrogen oxide emissions were above EPA limits at low flow rate and high operating temperature conditions.

Performance of fuel system at different diesel temperature

NASA Astrophysics Data System (ADS)

Xu, Xiaoyong; Li, Xiaolu; Sun, Zai

2010-08-01

This paper presents the findings about performance of the fuel system of a diesel engine at different diesel temperature obtained through simulation and experiment. It can be seen from these findings that at the same rotational speed of fuel pump, the initial pressure in the fuel pipe remain unchanged as the fuel temperature increases, the peak pressure at the side of fuel pipe near the injector delays, and its largest value of pressure decreases. Meanwhile, at the same temperature, as the rotational speed increases, the initial pressure of fuel pipe is also essentially the same, the arrival of its peaks delays, and its largest value of pressure increases. The maximum fuel pressure at the side of fuel pipe near the injector has an increase of 28.9 %, 22.3%, and 13.9% respectively than the previous ones according to its conditions. At the same rotational speed, as the temperature increases, the injection quantity through the nozzle orifice decreases. At the same temperature, as the rotational speed increases, the injection quantity through the nozzle orifice increases. These experimental results are consistent with simulation results.

An evaporative and engine-cycle model for fuel octane sensitivity prediction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moran, D.P.; Taylor, A.B.

The Motor Octane Number (MON) ranks fuels by their chemical resistance to knock. Evaporative cooling coupled with fuel chemistry determine Research Octane Number (RON) antiknock ratings. It is shown in this study that fuel Octane sensitivity (numerically RON minus MON) is liked to an important difference between the two test methods; the RON test allows each fuel`s evaporative cooling characteristics to affect gas temperature, while the MON test generally eliminates this effect by pre-evaporation. In order to establish RON test charge temperatures, a computer model of fuel evaporation was adapted to Octane Engine conditions, and simulations were compared with realmore » Octane Test Engine measurements including droplet and gas temperatures. A novel gas temperature probe yielded data that corresponded well with model predictions. Tests spanned single component fuels and blends of isomers, n-paraffins, aromatics and alcohols. Commercially available automotive and aviation gasolines were also tested. A good correlation was observed between the computer predictions and measured temperature data across the range of pure fuels and blends. A numerical method to estimate the effect of precombustion temperature differences on Octane sensitivity was developed and applied to analyze these data, and was found to predict the widely disparate sensitivities of the tested fuels with accuracy. Data are presented showing mixture temperature histories of various tested fuels, and consequent sensitivity predictions. It is concluded that a fuel`s thermal-evaporative behavior gives rise to fuel Octane sensitivity as measured by differences between the RON and MON tests. This is demonstrated by the success, over a wide range of fuels, of the sensitivity predictor method describes. Evaporative cooling, must therefore be regarded as an important parameter affecting the general road performance of automobiles.« less

Data Mining Methods Applied to Flight Operations Quality Assurance Data: A Comparison to Standard Statistical Methods

NASA Technical Reports Server (NTRS)

Stolzer, Alan J.; Halford, Carl

2007-01-01

In a previous study, multiple regression techniques were applied to Flight Operations Quality Assurance-derived data to develop parsimonious model(s) for fuel consumption on the Boeing 757 airplane. The present study examined several data mining algorithms, including neural networks, on the fuel consumption problem and compared them to the multiple regression results obtained earlier. Using regression methods, parsimonious models were obtained that explained approximately 85% of the variation in fuel flow. In general data mining methods were more effective in predicting fuel consumption. Classification and Regression Tree methods reported correlation coefficients of .91 to .92, and General Linear Models and Multilayer Perceptron neural networks reported correlation coefficients of about .99. These data mining models show great promise for use in further examining large FOQA databases for operational and safety improvements.

An non-uniformity voltage model for proton exchange membrane fuel cell

NASA Astrophysics Data System (ADS)

Li, Kelei; Li, Yankun; Liu, Jiawei; Guo, Ai

2017-01-01

The fuel cell used in transportation has environmental protection, high efficiency and no line traction power system which can greatly reduce line construction investment. That makes it a huge potential. The voltage uniformity is one of the most important factors affecting the operation life of proton exchange membrane fuel cell (PEMFC). On the basis of principle and classical model of the PEMFC, single cell voltage is calculated and the location coefficients are introduced so as to establish a non-uniformity voltage model. These coefficients are estimated with the experimental datum at stack current 50 A. The model is validated respectively with datum at 60 A and 100 A. The results show that the model reflects the basic characteristics of voltage non-uniformity and provides the beneficial reference for fuel cell control and single cell voltage detection.

Initial fuel temperature effects on burning rate of pool fire.

PubMed

Chen, Bing; Lu, Shou-Xiang; Li, Chang-Hai; Kang, Quan-Sheng; Lecoustre, Vivien

2011-04-15

The influence of the initial fuel temperature on the burning behavior of n-heptane pool fire was experimentally studied at the State Key Laboratory of Fire Science (SKLFS) large test hall. Circular pool fires with diameters of 100mm, 141 mm, and 200 mm were considered with initial fuel temperatures ranging from 290 K to 363 K. Burning rate and temperature distributions in fuel and vessel wall were recorded during the combustion. The burning rate exhibited five typical stages: initial development, steady burning, transition, bulk boiling burning, and decay. The burning rate during the steady burning stage was observed to be relatively independent of the initial fuel temperature. In contrast, the burning rate of the bulk boiling burning stage increases with increased initial fuel temperature. It was also observed that increased initial fuel temperature decreases the duration of steady burning stage. When the initial temperature approaches the boiling point, the steady burning stage nearly disappears and the burning rate moves directly from the initial development stage to the transition stage. The fuel surface temperature increases to its boiling point at the steady burning stage, shortly after ignition, and the bulk liquid reaches boiling temperature at the bulk boiling burning stage. No distinguished cold zone is formed in the fuel bed. However, boiling zone is observed and the thickness increases to its maximum value when the bulk boiling phenomena occurs. Copyright © 2011 Elsevier B.V. All rights reserved.

A novel method for effective diffusion coefficient measurement in gas diffusion media of polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Yang, Linlin; Sun, Hai; Fu, Xudong; Wang, Suli; Jiang, Luhua; Sun, Gongquan

2014-07-01

A novel method for measuring effective diffusion coefficient of porous materials is developed. The oxygen concentration gradient is established by an air-breathing proton exchange membrane fuel cell (PEMFC). The porous sample is set in a sample holder located in the cathode plate of the PEMFC. At a given oxygen flux, the effective diffusion coefficients are related to the difference of oxygen concentration across the samples, which can be correlated with the differences of the output voltage of the PEMFC with and without inserting the sample in the cathode plate. Compared to the conventional electrical conductivity method, this method is more reliable for measuring non-wetting samples.

Effect of hydrocarbon fuel type on fuel

NASA Technical Reports Server (NTRS)

Wong, E. L.; Bittker, D. A.

1982-01-01

A modified jet fuel thermal oxidation tester (JFTOT) procedure was used to evaluate deposit and sediment formation for four pure hydrocarbon fuels over the temperature range 150 to 450 C in 316-stainless-steel heater tubes. Fuel types were a normal alkane, an alkene, a naphthene, and an aromatic. Each fuel exhibited certain distinctive deposit and sediment formation characteristics. The effect of aluminum and 316-stainless-steel heater tube surfaces on deposit formation for the fuel n-decane over the same temperature range was investigated. Results showed that an aluminum surface had lower deposit formation rates at all temperatures investigated. By using a modified JFTOT procedure the thermal stability of four pure hydrocarbon fuels and two practical fuels (Jet A and home heating oil no. 2) was rated on the basis of their breakpoint temperatures. Results indicate that this method could be used to rate thermal stability for a series of fuels.

Applications of high pressure differential scanning calorimetry to aviation fuel thermal stability research

NASA Technical Reports Server (NTRS)

Neveu, M. C.; Stocker, D. P.

1985-01-01

High pressure differential scanning calorimetry (DSC) was studied as an alternate method for performing high temperature fuel thermal stability research. The DSC was used to measure the heat of reaction versus temperature of a fuel sample heated at a programmed rate in an oxygen pressurized cell. Pure hydrocarbons and model fuels were studied using typical DSC operating conditions of 600 psig of oxygen and a temperature range from ambient to 500 C. The DSC oxidation onset temperature was determined and was used to rate the fuels on thermal stability. Kinetic rate constants were determined for the global initial oxidation reaction. Fuel deposit formation is measured, and the high temperature volatility of some tetralin deposits is studied by thermogravimetric analysis. Gas chromatography and mass spectrometry are used to study the chemical composition of some DSC stressed fuels.

Fuel system technology overview

NASA Technical Reports Server (NTRS)

Friedman, R.

1980-01-01

Fuel system research and technology studies are being conducted to investigate the correlations and interactions of aircraft fuel system design and environment with applicable characteristics of the fuel. Topics include: (1) analysis of in-flight fuel temperatures; (2) fuel systems for high freezing point fuels; (3) experimental study of low temperature pumpability; (4) full scale fuel tank simulation; and (5) rapid freezing point measurement.

Modeling of thermal expansion coefficient of perovskite oxide for solid oxide fuel cell cathode

NASA Astrophysics Data System (ADS)

Heydari, F.; Maghsoudipour, A.; Alizadeh, M.; Khakpour, Z.; Javaheri, M.

2015-09-01

Artificial intelligence models have the capacity to eliminate the need for expensive experimental investigation in various areas of manufacturing processes, including the material science. This study investigates the applicability of adaptive neuro-fuzzy inference system (ANFIS) approach for modeling the performance parameters of thermal expansion coefficient (TEC) of perovskite oxide for solid oxide fuel cell cathode. Oxides (Ln = La, Nd, Sm and M = Fe, Ni, Mn) have been prepared and characterized to study the influence of the different cations on TEC. Experimental results have shown TEC decreases favorably with substitution of Nd3+ and Mn3+ ions in the lattice. Structural parameters of compounds have been determined by X-ray diffraction, and field emission scanning electron microscopy has been used for the morphological study. Comparison results indicated that the ANFIS technique could be employed successfully in modeling thermal expansion coefficient of perovskite oxide for solid oxide fuel cell cathode, and considerable savings in terms of cost and time could be obtained by using ANFIS technique.

Assessment of wear coefficients of nuclear zirconium claddings without and with pre-oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Jun; Cooley, Kevin M.; Shaw, Austin H.

In the cores of pressurized water nuclear reactors, water-flow induced vibration is known to cause claddings on the fuel rods to rub against their supporting grids. Such grid-to-rod-fretting (GTRF) may lead to fretting wear-through and the leakage of radioactive species. The surfaces of actual zirconium alloy claddings in a reactor are inevitably oxidized in the high-temperature pressurized water, and some claddings are even pre-oxidized. As a result, the wear process of the surface oxide film is expected to be quite different from the zirconium alloy substrate. In this paper, we attempt to measure the wear coefficients of zirconium claddings withoutmore » and with pre-oxidation rubbing against grid samples using a bench-scale fretting tribometer. Results suggest that the volumetric wear coefficient of the pre-oxidized cladding is 50 to 200 times lower than that of the untreated cladding. In terms of the linear rate of wear depth, the pre-oxidized alloy wears about 15 times more slowly than the untreated cladding. Finally, fitted with the experimentally-determined wear rates, a stage-wise GTRF engineering wear model demonstrates good agreement with in-reactor experience in predicting the trend of cladding lives.« less

Assessment of wear coefficients of nuclear zirconium claddings without and with pre-oxidation

DOE PAGES

Qu, Jun; Cooley, Kevin M.; Shaw, Austin H.; ...

2016-03-16

In the cores of pressurized water nuclear reactors, water-flow induced vibration is known to cause claddings on the fuel rods to rub against their supporting grids. Such grid-to-rod-fretting (GTRF) may lead to fretting wear-through and the leakage of radioactive species. The surfaces of actual zirconium alloy claddings in a reactor are inevitably oxidized in the high-temperature pressurized water, and some claddings are even pre-oxidized. As a result, the wear process of the surface oxide film is expected to be quite different from the zirconium alloy substrate. In this paper, we attempt to measure the wear coefficients of zirconium claddings withoutmore » and with pre-oxidation rubbing against grid samples using a bench-scale fretting tribometer. Results suggest that the volumetric wear coefficient of the pre-oxidized cladding is 50 to 200 times lower than that of the untreated cladding. In terms of the linear rate of wear depth, the pre-oxidized alloy wears about 15 times more slowly than the untreated cladding. Finally, fitted with the experimentally-determined wear rates, a stage-wise GTRF engineering wear model demonstrates good agreement with in-reactor experience in predicting the trend of cladding lives.« less

Temperature correction in conductivity measurements

USGS Publications Warehouse

Smith, Stanford H.

1962-01-01

Electrical conductivity has been widely used in freshwater research but usual methods employed by limnologists for converting measurements to conductance at a given temperature have not given uniformly accurate results. The temperature coefficient used to adjust conductivity of natural waters to a given temperature varies depending on the kinds and concentrations of electrolytes, the temperature at the time of measurement, and the temperature to which measurements are being adjusted. The temperature coefficient was found to differ for various lake and stream waters, and showed seasonal changes. High precision can be obtained only by determining temperature coefficients for each water studied. Mean temperature coefficients are given for various temperature ranges that may be used where less precision is required.

Nuclear fuel alloys or mixtures and method of making thereof

DOEpatents

Mariani, Robert Dominick; Porter, Douglas Lloyd

2016-04-05

Nuclear fuel alloys or mixtures and methods of making nuclear fuel mixtures are provided. Pseudo-binary actinide-M fuel mixtures form alloys and exhibit: body-centered cubic solid phases at low temperatures; high solidus temperatures; and/or minimal or no reaction or inter-diffusion with steel and other cladding materials. Methods described herein through metallurgical and thermodynamics advancements guide the selection of amounts of fuel mixture components by use of phase diagrams. Weight percentages for components of a metallic additive to an actinide fuel are selected in a solid phase region of an isothermal phase diagram taken at a temperature below an upper temperature limit for the resulting fuel mixture in reactor use. Fuel mixtures include uranium-molybdenum-tungsten, uranium-molybdenum-tantalum, molybdenum-titanium-zirconium, and uranium-molybdenum-titanium systems.

Collision and radiative processes in emission of atmospheric carbon dioxide

NASA Astrophysics Data System (ADS)

Smirnov, B. M.

2018-05-01

The peculiarities of the spectroscopic properties of CO2 molecules in air due to vibration-rotation radiative transitions are analyzed. The absorption coefficient due to atmospheric carbon dioxide and other atmospheric components is constructed within the framework of the standard atmosphere model, on the basis of classical molecular spectroscopy and the regular model for the spectroscopy absorption band. The radiative flux from the atmosphere toward the Earth is represented as that of a blackbody, and the radiative temperature for emission at a given frequency is determined with accounting for the local thermodynamic equilibrium, a small gradient of the tropospheric temperature and a high optical thickness of the troposphere for infrared radiation. The absorption band model with an absorption coefficient averaged over the frequency and line-by-line model are used for evaluating the radiative flux from the atmosphere to the Earth which values are nearby for these models and are equal W m‑2 for the contemporary concentration of atmospheric CO2 molecules and W m‑2 at its doubled value. The absorption band model is not suitable to calculate the radiative flux change at doubling of carbon dioxide concentration because averaging over oscillations decreases the range where the atmospheric optical thickness is of the order of one, and just this range determines this change. The line-by-line method gives the change of the global temperature K as a result of doubling the carbon dioxide concentration. The contribution to the global temperature change due to anthropogenic injection of carbon dioxide in the atmosphere, i.e. resulted from combustion of fossil fuels, is approximately 0.02 K now.

40 CFR 86.1231-90 - Vehicle preparation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... recording the temperature of the prescribed test fuel at the approximate mid-volume of the fuel when the... specified test fuel (§ 86.1213) at room temperature. Then drive the vehicle through at least one cycle of... Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and...

40 CFR 86.1231-90 - Vehicle preparation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... recording the temperature of the prescribed test fuel at the approximate mid-volume of the fuel when the... specified test fuel (§ 86.1213) at room temperature. Then drive the vehicle through at least one cycle of... Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and...

40 CFR 86.1231-96 - Vehicle preparation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as described... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be... Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and...

40 CFR 86.1231-96 - Vehicle preparation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as described... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be... Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and...

40 CFR 86.1231-90 - Vehicle preparation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... recording the temperature of the prescribed test fuel at the approximate mid-volume of the fuel when the... specified test fuel (§ 86.1213) at room temperature. Then drive the vehicle through at least one cycle of... Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and...

40 CFR 86.1231-96 - Vehicle preparation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as described... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be... Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and...

40 CFR 86.1231-96 - Vehicle preparation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as described... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be... Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and...

40 CFR 86.1231-90 - Vehicle preparation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... recording the temperature of the prescribed test fuel at the approximate mid-volume of the fuel when the... specified test fuel (§ 86.1213) at room temperature. Then drive the vehicle through at least one cycle of... Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and...

Helium interactions with alumina formed by atomic layer deposition show potential for mitigating problems with excess helium in spent nuclear fuel

NASA Astrophysics Data System (ADS)

Zhang, Shenli; Yu, Erick; Gates, Sean; Cassata, William S.; Makel, James; Thron, Andrew M.; Bartel, Christopher; Weimer, Alan W.; Faller, Roland; Stroeve, Pieter; Tringe, Joseph W.

2018-02-01

Helium gas accumulation from alpha decay during extended storage of spent fuel has potential to compromise the structural integrity the fuel. Here we report results obtained with surrogate nickel particles which suggest that alumina formed by atomic layer deposition can serve as a low volume-fraction, uniformly-distributed phase for retention of helium generated in fuel particles such as uranium oxide. Thin alumina layers may also form transport paths for helium in the fuel rod, which would otherwise be impermeable. Micron-scale nickel particles, representative of uranium oxide particles in their low helium solubility and compatibility with the alumina synthesis process, were homogeneously coated with alumina approximately 3-20 nm by particle atomic layer deposition (ALD) using a fluidized bed reactor. Particles were then loaded with helium at 800 °C in a tube furnace. Subsequent helium spectroscopy measurements showed that the alumina phase, or more likely a related nickel/alumina interface structure, retains helium at a density of at least 1017 atoms/cm3. High resolution transmission electron microscopy revealed that the thermal treatment increased the alumina thickness and generated additional porosity. Results from Monte Carlo simulations on amorphous alumina predict the helium retention concentration at room temperature could reach 1021 atoms/cm3 at 400 MPa, a pressure predicted by others to be developed in uranium oxide without an alumina secondary phase. This concentration is sufficient to eliminate bubble formation in the nuclear fuel for long-term storage scenarios, for example. Measurements by others of the diffusion coefficient in polycrystalline alumina indicate values several orders of magnitude higher than in uranium oxide, which then can also allow for helium transport out of the spent fuel.

Design and analysis of a nuclear reactor core for innovative small light water reactors

NASA Astrophysics Data System (ADS)

Soldatov, Alexey I.

In order to address the energy needs of developing countries and remote communities, Oregon State University has proposed the Multi-Application Small Light Water Reactor (MASLWR) design. In order to achieve five years of operation without refueling, use of 8% enriched fuel is necessary. This dissertation is focused on core design issues related with increased fuel enrichment (8.0%) and specific MASLWR operational conditions (such as lower operational pressure and temperature, and increased leakage due to small core). Neutron physics calculations are performed with the commercial nuclear industry tools CASMO-4 and SIMULATE-3, developed by Studsvik Scandpower Inc. The first set of results are generated from infinite lattice level calculations with CASMO-4, and focus on evaluation of the principal differences between standard PWR fuel and MASLWR fuel. Chapter 4-1 covers aspects of fuel isotopic composition changes with burnup, evaluation of kinetic parameters and reactivity coefficients. Chapter 4-2 discusses gadolinium self-shielding and shadowing effects, and subsequent impacts on power generation peaking and Reactor Control System shadowing. The second aspect of the research is dedicated to core design issues, such as reflector design (chapter 4-3), burnable absorber distribution and programmed fuel burnup and fuel use strategy (chapter 4-4). This section also includes discussion of the parameters important for safety and evaluation of Reactor Control System options for the proposed core design. An evaluation of the sensitivity of the proposed design to uncertainty in calculated parameters is presented in chapter 4-5. The results presented in this dissertation cover a new area of reactor design and operational parameters, and may be applicable to other small and large pressurized water reactor designs.

Calculation of Distribution Dynamics of Inhomogeneous Temperature Field in Range of Fuel Elements by Using FreeFem++

NASA Astrophysics Data System (ADS)

Amosova, E. V.; Shishkin, A. V.

2017-11-01

This article introduces the result of studying the heat exchange in the fuel element of the nuclear reactor fuel magazine. Fuel assemblies are completed as a bundle of cylindrical fuel elements located at the tops of a regular triangle. Uneven distribution of fuel rods in a nuclear reactor’s core forms the inhomogeneity of temperature fields. This article describes the developed method for heat exchange calculation with the account for impact of an inhomogeneous temperature field on the thermal-physical properties of materials and unsteady effects. The acquired calculation results are used for evaluating the tolerable temperature levels in protective case materials.

Towards the reanalysis of void coefficients measurements at proteus for high conversion light water reactor lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hursin, M.; Koeberl, O.; Perret, G.

2012-07-01

High Conversion Light Water Reactors (HCLWR) allows a better usage of fuel resources thanks to a higher breeding ratio than standard LWR. Their uses together with the current fleet of LWR constitute a fuel cycle thoroughly studied in Japan and the US today. However, one of the issues related to HCLWR is their void reactivity coefficient (VRC), which can be positive. Accurate predictions of void reactivity coefficient in HCLWR conditions and their comparisons with representative experiments are therefore required. In this paper an inter comparison of modern codes and cross-section libraries is performed for a former Benchmark on Void Reactivitymore » Effect in PWRs conducted by the OECD/NEA. It shows an overview of the k-inf values and their associated VRC obtained for infinite lattice calculations with UO{sub 2} and highly enriched MOX fuel cells. The codes MCNPX2.5, TRIPOLI4.4 and CASMO-5 in conjunction with the libraries ENDF/B-VI.8, -VII.0, JEF-2.2 and JEFF-3.1 are used. A non-negligible spread of results for voided conditions is found for the high content MOX fuel. The spread of eigenvalues for the moderated and voided UO{sub 2} fuel are about 200 pcm and 700 pcm, respectively. The standard deviation for the VRCs for the UO{sub 2} fuel is about 0.7% while the one for the MOX fuel is about 13%. This work shows that an appropriate treatment of the unresolved resonance energy range is an important issue for the accurate determination of the void reactivity effect for HCLWR. A comparison to experimental results is needed to resolve the presented discrepancies. (authors)« less

DOPPLER CALCULATIONS FOR LARGE FAST CERAMIC REACTORS--EFFECTS OF IMPROVED METHODS AND RECENT CROSS SECTION INFORMATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greebler, P.; Goldman, E.

1962-12-19

Doppler calculations for large fast ceramic reactors (FCR), using recent cross section information and improved methods, are described. Cross sections of U/sup 238/, Pu/sup 239/, and Pu/sup 210/ with fuel temperature variations needed for perturbation calculations of Doppler reactivity changes are tabulated as a function of potential scattering cross section per absorber isotope at energies below 400 kev. These may be used in Doppler calculations for anv fast reactor. Results of Doppler calculations on a large fast ceramic reactor are given to show the effects of the improved calculation methods and of recent cross secrion data on the calculated Dopplermore » coefficient. The updated methods and cross sections used yield a somewhat harder spectrum and accordingly a somewhat smaller Doppler coefficient for a given FCR core size and composition than calculated in earlier work, but they support the essential conclusion derived earlier that the Doppler effect provides an important safety advantage in a large FCR. 28 references. (auth)« less

Thermodynamic analysis of biofuels as fuels for high temperature fuel cells

NASA Astrophysics Data System (ADS)

Milewski, Jarosław; Bujalski, Wojciech; Lewandowski, Janusz

2011-11-01

Based on mathematical modeling and numerical simulations, applicativity of various biofuels on high temperature fuel cell performance are presented. Governing equations of high temperature fuel cell modeling are given. Adequate simulators of both solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC) have been done and described. Performance of these fuel cells with different biofuels is shown. Some characteristics are given and described. Advantages and disadvantages of various biofuels from the system performance point of view are pointed out. An analysis of various biofuels as potential fuels for SOFC and MCFC is presented. The results are compared with both methane and hydrogen as the reference fuels. The biofuels are characterized by both lower efficiency and lower fuel utilization factors compared with methane. The presented results are based on a 0D mathematical model in the design point calculation. The governing equations of the model are also presented. Technical and financial analysis of high temperature fuel cells (SOFC and MCFC) are shown. High temperature fuel cells can be fed by biofuels like: biogas, bioethanol, and biomethanol. Operational costs and possible incomes of those installation types were estimated and analyzed. A comparison against classic power generation units is shown. A basic indicator net present value (NPV) for projects was estimated and commented.

Thermodynamic analysis of biofuels as fuels for high temperature fuel cells

NASA Astrophysics Data System (ADS)

Milewski, Jarosław; Bujalski, Wojciech; Lewandowski, Janusz

2013-02-01

Based on mathematical modeling and numerical simulations, applicativity of various biofuels on high temperature fuel cell performance are presented. Governing equations of high temperature fuel cell modeling are given. Adequate simulators of both solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC) have been done and described. Performance of these fuel cells with different biofuels is shown. Some characteristics are given and described. Advantages and disadvantages of various biofuels from the system performance point of view are pointed out. An analysis of various biofuels as potential fuels for SOFC and MCFC is presented. The results are compared with both methane and hydrogen as the reference fuels. The biofuels are characterized by both lower efficiency and lower fuel utilization factors compared with methane. The presented results are based on a 0D mathematical model in the design point calculation. The governing equations of the model are also presented. Technical and financial analysis of high temperature fuel cells (SOFC and MCFC) are shown. High temperature fuel cells can be fed by biofuels like: biogas, bioethanol, and biomethanol. Operational costs and possible incomes of those installation types were estimated and analyzed. A comparison against classic power generation units is shown. A basic indicator net present value (NPV) for projects was estimated and commented.

Performance of a multiple venturi fuel-air preparation system. [fuel injection for gas turbines

NASA Technical Reports Server (NTRS)

Tacina, R. R.

1979-01-01

Spatial fuel-air distributions, degree of vaporization, and pressure drop were measured 16.5 cm downstream of the fuel injection plane of a multiple Venturi tube fuel injector. Tests were performed in a 12 cm tubular duct. Test conditions were: a pressure of 0.3 MPa, inlet air temperature from 400 to 800K, air velocities of 10 and 20 m/s, and fuel-air ratios of 0.010 and 0.020. The fuel was Diesel #2. Spatial fuel-air distributions were within + or - 20 percent of the mean at inlet air temperatures above 450K. At an inlet air temperature of 400K, the fuel-air distribution was measured when a 50 percent blockage plate was placed 9.2 cm upstream of the fuel injection plane to distort the inlet air velocity fuel injection plane to distort the inlet air velocity profile. Vaporization of the fuel was 50 percent complete at an inlet air temperature of 400K and the percentage increased linearly with temperature to complete vaporization at 600K. The pressure drop was 3 percent at the design point which was three times greater than the designed value and the single tube experiment value. No autoignition or flashback was observed at the conditions tested.

Pm-1 Reactor Core Final Design Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagley, R. O.; Cox, F. H.; Carnasale, A.

1962-01-01

The PM-1 water cooled and moderated core contains 741 highly enriched stainless steel cermet tubular fuel elements and 90 lumped B stainless steel burnable poison elements, and it is controlled by 6 Y-shaped europium titanate movable control rods. The core has a lifetime of 1.95 years when operated at its design power level of 9.37 mw of thermal energy. The control of the core is designed so that there is a positive shutdown margin at all times with either one rod stuck completely out or the core or with two rods stuck in the operating condition. The core power ismore » removed by 2125 gpm of pressurized water at an average temperature of 463 deg F and pressure of 1300 psia. In reactors of this type, the core is stable with a negative temperature coefficient of approximately 2.5 x 10/sup -4/ DELTA K/K/ deg F.« less

Updated Chemical Kinetics and Sensitivity Analysis Code

NASA Technical Reports Server (NTRS)

Radhakrishnan, Krishnan

2005-01-01

An updated version of the General Chemical Kinetics and Sensitivity Analysis (LSENS) computer code has become available. A prior version of LSENS was described in "Program Helps to Determine Chemical-Reaction Mechanisms" (LEW-15758), NASA Tech Briefs, Vol. 19, No. 5 (May 1995), page 66. To recapitulate: LSENS solves complex, homogeneous, gas-phase, chemical-kinetics problems (e.g., combustion of fuels) that are represented by sets of many coupled, nonlinear, first-order ordinary differential equations. LSENS has been designed for flexibility, convenience, and computational efficiency. The present version of LSENS incorporates mathematical models for (1) a static system; (2) steady, one-dimensional inviscid flow; (3) reaction behind an incident shock wave, including boundary layer correction; (4) a perfectly stirred reactor; and (5) a perfectly stirred reactor followed by a plug-flow reactor. In addition, LSENS can compute equilibrium properties for the following assigned states: enthalpy and pressure, temperature and pressure, internal energy and volume, and temperature and volume. For static and one-dimensional-flow problems, including those behind an incident shock wave and following a perfectly stirred reactor calculation, LSENS can compute sensitivity coefficients of dependent variables and their derivatives, with respect to the initial values of dependent variables and/or the rate-coefficient parameters of the chemical reactions.

Effects of the cooling system parameters on heat transfer and performance of the PAFC stack during transient operation. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Ridha, Rabi M. J.

1992-01-01

An experimental investigation for the effects of transient operation of a phosphoric acid fuel-cell stack on heat transfer and temperature distribution in the electrodes has been conducted. The proposed work utilized the experimental setup with modifications, which was designed and constructed under NASA Contract No. NCC-3-17(5). The experimental results obtained from this investigation and the mathematical model obtained under NASA Contract No. NCC3-17(4) after modifications, were utilized to develop mathematical models for transient heat transfer coefficient and temperature distribution in the electrode and to evaluate the performance of the cooling - system under unsteady state conditions. The empirical formulas developed were then implemented to modifying the developed computer code. Two incompressible coolants were used to study experimentally the effect of the thermophysical properties of the cool-ants on the transient heat transfer coefficient and the thermal contact resistance during start-up and shut-down processes. Coolant mass flow rates were verified from 16 to 88.2 Kg/hr during the transient process when the electrical power supply was gradually increased or decreased in the range (O to 3000 W/sq m). The effect of the thermal contact resistance with a range of stack pressure from O to 3500 KPa was studied.

Determination of neutron multiplication coefficients for fuel elements irradiated by spallation neutrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatia, Chitra; Kumar, V.

2010-02-15

A neutron multiplication coefficient, k{sub eff}, has been estimated for spallation neutron flux using the data of spectrum average cross sections of all absorption, fission, and nonelastic reaction channels of {sup 232}Th, {sup 238}U, {sup 235}U, and {sup 233}U fuel elements. It has been revealed that in spallation neutron flux (i) nonfission, nonabsorption reactions play an important role in the calculation of k{sub eff}, (ii) one can obtain a high value of k{sub eff} even for fertile {sup 232}Th fuel, which is hardly possible in a conventional fast reactor, and (iii) spectrum average absorption cross sections of neutron poisons ofmore » a conventional reactor are relatively very small.« less

Study of diffusion coefficient of anhydrous trehalose glasses by using PFG-NMR spectroscopy

NASA Astrophysics Data System (ADS)

Kwon, Hyun-Joung; Takekawa, Reiji; Kawamura, Junichi; Tokuyama, Michio

2013-02-01

We investigated the temperature dependent long time self-diffusion coefficient of the anhydrous trehalose supercooled liquids by using pulsed field gradient nuclear magnetic resonance (PFG-NMR) spectroscopy. At the same temperature ranges, the diffusion coefficient convoluted from the α-relaxation time as Einstein-Smoluchowski relaxation, measured by using the dielectric loss spectroscopy are well overlapped with diffusion coefficients within experimental error. The temperature dependent diffusion coefficients obtained from different methods are normalized by fictive temperature and well satisfied the single master curve, proposed by Tokuyama.

In-cell measurements of smoke backscattering coefficients using a CO2 laser system for application to lidar-dial forest fire detection

NASA Astrophysics Data System (ADS)

Bellecci, Carlo; Gaudio, Pasquale; Gelfusa, Michela; Lo Feudo, Teresa; Murari, Andrea; Richetta, Maria; de Leo, Leonerdo

2010-12-01

In the lidar-dial method, the amount of the water vapor present in the smoke of the vegetable fuel is detected to reduce the number of false alarms. We report the measurements of the smoke backscattering coefficients for the CO2 laser lines 10R20 and 10R18 as determined in an absorption cell for two different vegetable fuels (eucalyptus and conifer). These experimental backscattering coefficients enable us to determine the error to be associated to the water vapor measurements when the traditional first-order approximation is assumed. We find that this first-order approximation is valid for combustion rates as low as 100 g/s.

Analysis of key safety metrics of thorium utilization in LWRs

DOE PAGES

Ade, Brian J.; Bowman, Stephen M.; Worrall, Andrew; ...

2016-04-08

Here, thorium has great potential to stretch nuclear fuel reserves because of its natural abundance and because it is possible to breed the 232Th isotope into a fissile fuel ( 233U). Various scenarios exist for utilization of thorium in the nuclear fuel cycle, including use in different nuclear reactor types (e.g., light water, high-temperature gas-cooled, fast spectrum sodium, and molten salt reactors), along with use in advanced accelerator-driven systems and even in fission-fusion hybrid systems. The most likely near-term application of thorium in the United States is in currently operating light water reactors (LWRs). This use is primarily based onmore » concepts that mix thorium with uranium (UO 2 + ThO 2) or that add fertile thorium (ThO 2) fuel pins to typical LWR fuel assemblies. Utilization of mixed fuel assemblies (PuO 2 + ThO 2) is also possible. The addition of thorium to currently operating LWRs would result in a number of different phenomenological impacts to the nuclear fuel. Thorium and its irradiation products have different nuclear characteristics from those of uranium and its irradiation products. ThO 2, alone or mixed with UO 2 fuel, leads to different chemical and physical properties of the fuel. These key reactor safety–related issues have been studied at Oak Ridge National Laboratory and documented in “Safety and Regulatory Issues of the Thorium Fuel Cycle” (NUREG/CR-7176, U.S. Nuclear Regulatory Commission, 2014). Various reactor analyses were performed using the SCALE code system for comparison of key performance parameters of both ThO 2 + UO 2 and ThO 2 + PuO 2 against those of UO 2 and typical UO 2 + PuO 2 mixed oxide fuels, including reactivity coefficients and power sharing between surrounding UO 2 assemblies and the assembly of interest. The decay heat and radiological source terms for spent fuel after its discharge from the reactor are also presented. Based on this evaluation, potential impacts on safety requirements and identification of knowledge gaps that require additional analysis or research to develop a technical basis for the licensing of thorium fuel are identified.« less

Chemical kinetic modeling of propene oxidation at low and intermediate temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilk, R.D.; Cernansky, N.P.; Pitz, W.J.

1986-01-13

A detailed chemical kinetic mechanism for propene oxidation is developed and used to model reactions in a static reactor at temperatures of 590 to 740/sup 0/K, equivalence ratios of 0.8 to 2.0, and a pressure of 600 torr. Modeling of hydrocarbon oxidation in this temperature range is important for the validation of detailed models to be used for performing calculations related to automotive engine knock. The model predicted induction periods and species concentrations for all the species measured experimentally in a static reactor by Wilk, Cernansky, and Cohen. The detailed model predicted a temperature region of approximately constant induction periodmore » which corresponded very closely to the region of negative temperature coefficient behavior found in the experiment. Overall, the calculated concentrations of acetaldehyde, ethene, and methane were somewhat low compared to the experimental measurements, and the calculated concentrations of formaldehyde and methanol were high. The characteristic s-shape of the fuel concentration history was well predicted. The importance of OH+C/sub 3/H/sub 6/ and related rections in determining product distributions and the importance of consumption reactions for allyl radicals was demonstrated by the modeling calculations. 18 refs., 4 figs., 1 tab.« less

Reference-material system for estimating health and environmental risks of selected material cycles and energy systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowther, M.A.; Moskowitz, P.D.

1981-07-01

Sample analyses and detailed documentation are presented for a Reference Material System (RMS) to estimate health and environmental risks of different material cycles and energy systems. Data inputs described include: end-use material demands, efficiency coefficients, environmental emission coefficients, fuel demand coefficients, labor productivity estimates, and occupational health and safety coefficients. Application of this model permits analysts to estimate fuel use (e.g., Btu), occupational risk (e.g., fatalities), and environmental emissions (e.g., sulfur oxide) for specific material trajectories or complete energy systems. Model uncertainty is quantitatively defined by presenting a range of estimates for each data input. Systematic uncertainty not quantified relatesmore » to the boundaries chosen for analysis and reference system specification. Although the RMS can be used to analyze material system impacts for many different energy technologies, it was specifically used to examine the health and environmental risks of producing the following four types of photovoltaic devices: silicon n/p single-crystal cells produced by a Czochralski process; silicon metal/insulator/semiconductor (MIS) cells produced by a ribbon-growing process; cadmium sulfide/copper sulfide backwall cells produced by a spray deposition process; and gallium arsenide cells with 500X concentrator produced by a modified Czochralski process. Emission coefficients for particulates, sulfur dioxide and nitrogen dioxide; solid waste; total suspended solids in water; and, where applicable, air and solid waste residuals for arsenic, cadmium, gallium, and silicon are examined and presented. Where data are available the coefficients for particulates, sulfur oxides, and nitrogen oxides include both process and on-site fuel-burning emissions.« less

Transparent athermal glass-ceramics in Li2O-Al2O3-SiO2 system

NASA Astrophysics Data System (ADS)

Himei, Yusuke; Nagakane, Tomohiro; Sakamoto, Akihiko; Kitamura, Naoyuki; Fukumi, Kohei; Nishii, Junji; Hirao, Kazuyuki

2005-04-01

An attempt has been conducted to develop multicomponent transparent glass-ceramics which have athermal property better than silica glass. Transparent Li2O-Al2O3-SiO2 (LAS) glass-ceramics with small thermal expansion coefficient was chosen as a candidate. Athermal property of the glass-ceramics was improved by the independent control of temperature coefficients of electronic polarizability and thermal expansion coefficient, both of which govern the temperature coefficient of optical path length. It was found that temperature coefficient of electronic polarizability and thermal expansion coefficient of the LAS glass-ceramics were controllable by the additives and crystallization conditions. The doping of B2O3 and the crystallization under a hydrostatic pressure of 196 MPa were very effective to reduce temperature coefficient of electronic polarizability without a remarkable increase in thermal expansion coefficient. It was deduced that the reduction in temperature coefficient of electronic polarizability by the crystallization under 196 MPa resulted from the inhibition of the precipitation of beta-spodumene solid solution. The relative temperature coefficients of optical path length of B2O3-doped glass-ceramic crystallized under 196 MPa was 11.7 x 10-6/°C, which was slightly larger than that of silica glass. Nevertheless, the thermal expansion coefficient of this glass-ceramic was smaller than that of silica glass.

External tank chill effect on the space transportation system launch pad environment

NASA Technical Reports Server (NTRS)

Ahmad, R. A.; Boraas, S.

1991-01-01

The external tank (ET) of the STS contains liquid oxygen and liquid hydrogen as oxidizer and fuel for the SSMEs. Once the cryogen have been loaded into the ET, the temperature of the air surrounding the STS is chilled by the cold outer surface of the ET. This paper describes a two-dimensional flow and thermal analysis to determine this chill effect on the STS launch pad environment subsequent to the ET loading operation. The analysis was done assuming winter conditions and a northwest wind direction. An existing CFD code, PHOENICS '81, was used in the study. The results are presented as local and average values of the heat transfer coefficient, the Nusselt number, and the surface temperature around the redesigned solid rocket motors (RSRMs) and the ET. The temperature depression caused by the ET chilling of the air in the vicinity of the RSRMs was calculated to be 3 F below the ambient. This compares with the observed 1-2 F RSRM surface temperature depression based upon measurements made prior to the winter flight of STS-29. Since the surface temperature would be expected to be slightly higher than the local air temperature, the predicted temperature depression of the air appears to be substantiated.

Motorcycle waste heat energy harvesting

NASA Astrophysics Data System (ADS)

Schlichting, Alexander D.; Anton, Steven R.; Inman, Daniel J.

2008-03-01

Environmental concerns coupled with the depletion of fuel sources has led to research on ethanol, fuel cells, and even generating electricity from vibrations. Much of the research in these areas is stalling due to expensive or environmentally contaminating processes, however recent breakthroughs in materials and production has created a surge in research on waste heat energy harvesting devices. The thermoelectric generators (TEGs) used in waste heat energy harvesting are governed by the Thermoelectric, or Seebeck, effect, generating electricity from a temperature gradient. Some research to date has featured platforms such as heavy duty diesel trucks, model airplanes, and automobiles, attempting to either eliminate heavy batteries or the alternator. A motorcycle is another platform that possesses some very promising characteristics for waste heat energy harvesting, mainly because the exhaust pipes are exposed to significant amounts of air flow. A 1995 Kawasaki Ninja 250R was used for these trials. The module used in these experiments, the Melcor HT3-12-30, produced an average of 0.4694 W from an average temperature gradient of 48.73 °C. The mathematical model created from the Thermoelectric effect equation and the mean Seebeck coefficient displayed by the module produced an average error from the experimental data of 1.75%. Although the module proved insufficient to practically eliminate the alternator on a standard motorcycle, the temperature data gathered as well as the examination of a simple, yet accurate, model represent significant steps in the process of creating a TEG capable of doing so.

The effects of reduced ambient temperatures on the warm-up fuel consumption behavior of gasoline fueled automobiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pucher, G.R.; Gardiner, D.P.; Mallory, R.W.

Warm-up fuel consumption behavior as affected by ambient temperature was evaluated for five OEM gasoline fueled automobiles. Multiple EPA FTP 75 tests were performed with each vehicle at ambient test cell soak temperatures of 25 C and {minus}7 C. Fuel consumption measured during the warm-up (Bag 1, Cold Transient) test segments at these two temperature conditions was compared to the fully warmed Hot Transient (Bag 3) fuel consumption from the 25 C ambient temperature tests (the Bag 1 and Bag 3 segments involve identical speed curves). Fuel consumption increases over the 25 C Bag 3 tests for the two warm-upmore » test conditions were differentiated as those caused by increased drivetrain losses and those caused by intake charge enrichment. Results show wide variations in warm-up behavior among the five vehicles with respect to the relative increases in fuel consumption, and the proportion of the fuel consumption increases attributable to drivetrain losses and enrichment. It was discovered that the most sophisticated vehicle systems do not necessarily facilitate the least degradation in fuel consumption with respect to baseline conditions for the group of vehicles tested.« less

Alternate-Fueled Combustor-Sector Performance

NASA Technical Reports Server (NTRS)

Thomas, Anna E.; Saxena, Nikita T.; Shouse, Dale T.; Neuroth, Craig; Hendricks, Robert C.; Lynch, Amy; Frayne, Charles W.; Stutrud, Jeffrey S.; Corporan, Edwin; Hankins, Terry

2012-01-01

In order to realize alternative fueling for military and commercial use, the industry has set forth guidelines that must be met by each fuel. These aviation fueling requirements are outlined in MILDTL- 83133F(2008) or ASTM D 7566 Annex (2011) standards, and are classified as drop-in fuel replacements. This paper provides combustor performance data for synthetic-paraffinic-kerosene- (SPK-) type (Fisher-Tropsch (FT)) fuel and blends with JP-8+100, relative to JP-8+100 as baseline fueling. Data were taken at various nominal inlet conditions: 75 psia (0.52 MPa) at 500 F (533 K), 125 psia (0.86 MPa) at 625 F (603 K), 175 psia (1.21 MPa) at 725 F (658 K), and 225 psia (1.55 MPa) at 790 F (694 K). Combustor performance analysis assessments were made for the change in flame temperatures, combustor efficiency, wall temperatures, and exhaust plane temperatures at 3%, 4%, and 5% combustor pressure drop (% delta P) for fuel: air ratios (F/A) ranging from 0.010 to 0.025. Significant general trends show lower liner temperatures and higher flame and combustor outlet temperatures with increases in FT fueling relative to JP-8+100 fueling. The latter affects both turbine efficiency and blade/vane life.

The Low Temperature Oxidation of 2,7-Dimethyloctane in a Pressurized Flow Reactor

NASA Astrophysics Data System (ADS)

Farid, Farinaz

The complexity of real fuels has fostered the use of simple mixtures of hydrocarbons whose combustion behavior approximates that of real fuels in both experimental and computational studies to develop models of the combustion of the real fuel. These simple mixtures have been called surrogates. Lightly branched paraffins are an important class of constituents in gasoline, diesel and aviation turbine fuels and therefore are primary candidates for use as a component in a surrogate. Unfortunately, fundamental studies on combustion characteristics of high molecular weight mono- and di-methylated iso-paraffins are scarce. Therefore, this study was designed to investigate the low-temperature oxidation of 2,7-dimethyloctane (2,7-DMO) (C10H22), a lightly branched isomer of decane. Replicate 2,7-DMO oxidation experiments were conducted in a pressurized flow reactor (PFR) over the temperature range of 550 -- 850 K, at a pressure of 8 atm and an equivalence ratio of 0.3 in 4.21% oxygen / nitrogen. The reactivity was mapped by continuous monitoring of CO, CO 2, and O2 using a non-dispersive infrared (NDIR) carbon monoxide / carbon dioxide analyzer and an electrochemical oxygen sensor. For examining the underlying reaction chemistry, detailed speciation of samples was performed at selected temperatures using a gas chromatograph with a flame ionization detector coupled to a mass spectrometer. Comparable oxidation experiments for n-decane were carried out to examine the unique effects of branching on fuel reactivity and distribution of major stable intermediates. For both isomers, the onset of negative temperature coefficient (NTC) region was observed near 700 K, with the reactivity decreasing with increasing the temperature. The flow reactor study of n-decane oxidation confirmed that the isomerization reduces the amount of CO produced at peak reactivity. In addition to reaction inhibition, branching affected the distribution of C2-C 4 olefin intermediates. While the oxidation of n-decane resulted primarily in the formation of ethene near the NTC start, propene and isobutene were the major olefins produced from 2,7-DMO. A comparative analysis of experimental data with respect to a detailed chemical kinetic model for 2,7-DMO was performed and discrepancies were noted. Based on these results, a collaborative effort with Dr. Charles Westbrook (Lawrence Livermore National Laboratory) was initiated to refine the model predictions in the low temperature and NTC regimes. The effort resulted in an updated version of the 2,7-DMO mechanism, improving some of the key features such as calculated CO2 profile and final yields of iso-butene over the studied range of temperature. Fuel pyrolysis in the intermediate temperature regime, 850 -- 1000 K, also was investigated for the first time in the PFR facility. However, preliminary n-decane experiments measured only a small amount of fuel decomposition, indicating that higher temperature operation would be beneficial. The major species produced from n-decane decomposition, in descending order of molar fraction, were ethene, propene, and 1-butene. These results were compared with the predictions of two existing chemical kinetic models and the sources of variations between the experiments and the models as well as among the mechanisms were investigated. At 1000 K, the mechanisms predicted higher levels of fuel depletion and ethene production. Also, while the mechanisms were similar in their predicted pathways for fuel depletion and formation of ethene, inconsistencies were observed in relative contribution of these pathways to the final yields as well as the rate parameter determination for several sensitive reactions with respect to n-decane and ethene. Overall, the research aided in achieving a data set quantifying the oxidation characteristics of 2,7-DMO (and n-decane for comparison) as well as an elucidation of critical reaction pathways based on experimental results. Preliminary pyrolysis experiments were carried out using n-decane and the limitations on companion 2,7-DMO pyrolysis experiments were established. The data was compared with the predictions of several chemical kinetic mechanisms and, using tools such as rate of production analysis and sensitivity analysis, the sources of deviations from experimental data as well as possible areas of improvement were identified. The findings from 2,7-DMO study was directly used to refine an existing chemical kinetic model for 2,7-DMO, in line with the ultimate goal of feeding the much needed experimental database for validation and refinement of kinetic models of jet fuel surrogates.

Analysis of pellet cladding interaction and creep of U 3SIi2 fuel for use in light water reactors

NASA Astrophysics Data System (ADS)

Metzger, Kathryn E.

Following the accident at the Fukushima plant, enhancing the accident tolerance of the light water reactor (LWR) fleet became a topic of serious discussion. Under the direction of congress, the DOE office of Nuclear Energy added accident tolerant fuel development as a primary component to the existing Advanced Fuels Program. The DOE defines accident tolerant fuels as fuels that "in comparison with the standard UO2- Zircaloy system currently used by the nuclear industry, can tolerate loss of active cooling in the reactor core for a considerably longer time period (depending on the LWR system and accident scenario) while maintaining or improving the fuel performance during normal operations, operational transients, as well as design-basis and beyond design-basis events." To be economically viable, proposed accident tolerant fuels and claddings should be backward compatible with LWR designs, provide significant operating cost improvements such as power uprates, increased fuel burnup, or increased cycle length. In terms of safety, an alternative fuel pellet must have resistance to water corrosion comparable to UO2, thermal conductivity equal to or larger than that of UO2, and a melting temperature that allows the material to remain solid under power reactor conditions. Among the candidates, U3Si2 has a number of advantageous thermophysical properties, including; high density, high thermal conductivity at room temperature, and a high melting temperature. These properties support its use as an accident tolerant fuel while its high uranium density is capable of supporting uprates to the LWR fleet. This research characterizes U3Si2 pellets and analyzes U3Si2 under light water reactor conditions using the fuel performance code BISON. While some thermophysical properties for U3Si2 have been found in the literature, the irradiation behavior is sparse and limited to experience with dispersion fuels. Accordingly, the creep behavior for U3Si2 has been unknown, making it difficult to predict fuel-cladding mechanical behavior. This information is essential for designing accident tolerant fuel systems where ceramic claddings, like silicon carbide (SiC) are proposed. This research provides a model for both the thermal and irradiation creep behavior for U3Si2. This body of research is comprised of both experimental and modeling components. Characterization of the fuel microstructure includes; optical microscopy with pore and grain size analysis, helium pycnometry for density determination, mercury intrusion porosimetry, compositional analysis in the form of XRD, second phase identification using EDX, electrical resistance measurement via four point probe, determination of hardness and toughness through Vickers indentation testing, and determination of elastic properties using the impulse excitation method. Post-sintering grain size data allowed for the determination of grain boundary activation energy and diffusion coefficients, which were used to develop creep models. This was extended to lattice and irradiation enhanced diffusion in order to develop a U3Si2 creep model over thermal and irradiation creep regimes. In addition to the creep model, thermal and swelling behavior models for U3Si2 were implemented into the BISON fuel performance code. A series of simulations evaluated the performance and behavior of U3Si2 under typical light water reactor conditions with advanced SiC ceramic cladding. Simulation results show that fuel creep relieves stress in the ceramic cladding and postpones the. moment of fuel-clad contact. However, the stress reduction to the cladding is minimal because the fuel creep rate is low while the swelling rate is high. Future work should include the investigation of monolithic U3Si2 irradiation swelling since the current model relies upon the swelling data of U3Si2 particles in a metallic dispersion fuel. Additionally, planned thermal creep testing at the University of South Carolina can provide confirmation of the U3Si2 creep model contained herein.

PEBBED Uncertainty and Sensitivity Analysis of the CRP-5 PBMR DLOFC Transient Benchmark with the SUSA Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerhard Strydom

2011-01-01

The need for a defendable and systematic uncertainty and sensitivity approach that conforms to the Code Scaling, Applicability, and Uncertainty (CSAU) process, and that could be used for a wide variety of software codes, was defined in 2008. The GRS (Gesellschaft für Anlagen und Reaktorsicherheit) company of Germany has developed one type of CSAU approach that is particularly well suited for legacy coupled core analysis codes, and a trial version of their commercial software product SUSA (Software for Uncertainty and Sensitivity Analyses) was acquired on May 12, 2010. This report summarized the results of the initial investigations performed with SUSA,more » utilizing a typical High Temperature Reactor benchmark (the IAEA CRP-5 PBMR 400MW Exercise 2) and the PEBBED-THERMIX suite of codes. The following steps were performed as part of the uncertainty and sensitivity analysis: 1. Eight PEBBED-THERMIX model input parameters were selected for inclusion in the uncertainty study: the total reactor power, inlet gas temperature, decay heat, and the specific heat capability and thermal conductivity of the fuel, pebble bed and reflector graphite. 2. The input parameters variations and probability density functions were specified, and a total of 800 PEBBED-THERMIX model calculations were performed, divided into 4 sets of 100 and 2 sets of 200 Steady State and Depressurized Loss of Forced Cooling (DLOFC) transient calculations each. 3. The steady state and DLOFC maximum fuel temperature, as well as the daily pebble fuel load rate data, were supplied to SUSA as model output parameters of interest. The 6 data sets were statistically analyzed to determine the 5% and 95% percentile values for each of the 3 output parameters with a 95% confidence level, and typical statistical indictors were also generated (e.g. Kendall, Pearson and Spearman coefficients). 4. A SUSA sensitivity study was performed to obtain correlation data between the input and output parameters, and to identify the primary contributors to the output data uncertainties. It was found that the uncertainties in the decay heat, pebble bed and reflector thermal conductivities were responsible for the bulk of the propagated uncertainty in the DLOFC maximum fuel temperature. It was also determined that the two standard deviation (2s) uncertainty on the maximum fuel temperature was between ±58oC (3.6%) and ±76oC (4.7%) on a mean value of 1604 oC. These values mostly depended on the selection of the distributions types, and not on the number of model calculations above the required Wilks criteria (a (95%,95%) statement would usually require 93 model runs).« less

A rapid method to extract Seebeck coefficient under a large temperature difference

NASA Astrophysics Data System (ADS)

Zhu, Qing; Kim, Hee Seok; Ren, Zhifeng

2017-09-01

The Seebeck coefficient is one of the three important properties in thermoelectric materials. Since thermoelectric materials usually work under large temperature difference in real applications, we propose a quasi-steady state method to accurately measure the Seebeck coefficient under large temperature gradient. Compared to other methods, this method is not only highly accurate but also less time consuming. It can measure the Seebeck coefficient in both the temperature heating up and cooling down processes. In this work, a Zintl material (Mg3.15Nb0.05Sb1.5Bi0.49Te0.01) was tested to extract the Seebeck coefficient from room temperature to 573 K. Compared with a commercialized Seebeck coefficient measurement device (ZEM-3), there is ±5% difference between those from ZEM-3 and this method.

Fuel properties effect on the performance of a small high temperature rise combustor

NASA Technical Reports Server (NTRS)

Acosta, Waldo A.; Beckel, Stephen A.

1989-01-01

The performance of an advanced small high temperature rise combustor was experimentally determined at NASA-Lewis. The combustor was designed to meet the requirements of advanced high temperature, high pressure ratio turboshaft engines. The combustor featured an advanced fuel injector and an advanced segmented liner design. The full size combustor was evaluated at power conditions ranging from idle to maximum power. The effect of broad fuel properties was studied by evaluating the combustor with three different fuels. The fuels used were JP-5, a blend of Diesel Fuel Marine/Home Heating Oil, and a blend of Suntec C/Home Heating Oil. The fuel properties effect on the performance of the combustion in terms of pattern factor, liner temperatures, and exhaust emissions are documented.

40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120 Fuel...

40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120 Fuel...

40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120 Fuel...

40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120 Fuel...

40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120 Fuel...

Investigations into the low temperature behavior of jet fuels: Visualization, modeling, and viscosity studies

NASA Astrophysics Data System (ADS)

Atkins, Daniel L.

Aircraft operation in arctic regions or at high altitudes exposes jet fuel to temperatures below freeze point temperature specifications. Fuel constituents may solidify and remain within tanks or block fuel system components. Military and scientific requirements have been met with costly, low freeze point specialty jet fuels. Commercial airline interest in polar routes and the use of high altitude unmanned aerial vehicles (UAVs) has spurred interest in the effects of low temperatures and low-temperature additives on jet fuel. The solidification of jet fuel due to freezing is not well understood and limited visualization of fuel freezing existed prior to the research presented in this dissertation. Consequently, computational fluid dynamics (CFD) modeling that simulates jet fuel freezing and model validation were incomplete prior to the present work. The ability to simulate jet fuel freezing is a necessary tool for fuel system designers. An additional impediment to the understanding and simulation of jet fuel freezing has been the absence of published low-temperature thermo-physical properties, including viscosity, which the present work addresses. The dissertation is subdivided into three major segments covering visualization, modeling and validation, and viscosity studies. In the first segment samples of jet fuel, JPTS, kerosene, Jet A and Jet A containing additives, were cooled below their freeze point temperatures in a rectangular, optical cell. Images and temperature data recorded during the solidification process provided information on crystal habit, crystallization behavior, and the influence of the buoyancy-driven flow on freezing. N-alkane composition of the samples was determined. The Jet A sample contained the least n-alkane mass. The cooling of JPTS resulted in the least wax formation while the cooling of kerosene yielded the greatest wax formation. The JPTS and kerosene samples exhibited similar crystallization behavior and crystal habits during cooling. Low-temperature additives modified the crystal habit of the Jet A fuel. Crystal shapes and sizes were recorded for use in future computational modeling. In the second segment, a computational fluid dynamics model was developed that simulates the solidification of jet fuel due to freezing in a buoyancy-driven flow. Flow resistance caused by porous crystal structures that exist in liquid-solid regions is simulated through the use of a momentum resistance source term. (Abstract shortened by UMI.)

Combustion Temperature Measurement by Spontaneous Raman Scattering in a Jet-A Fueled Gas Turbine Combustor Sector

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.; DeGroot, Wilhelmus A.; Locke, Randy J.; Anderson, Robert C.

2002-01-01

Spontaneous vibrational Raman scattering was used to measure temperature in an aviation combustor sector burning jet fuel. The inlet temperature ranged from 670 K (750 F) to 756 K (900 F) and pressures from 13 to 55 bar. With the exception of a discrepancy that we attribute to soot, good agreement was seen between the Raman-derived temperatures and the theoretical temperatures calculated from the inlet conditions. The technique used to obtain the temperature uses the relationship between the N2 anti-Stokes and Stokes signals, within a given Raman spectrum. The test was performed using a NASA-concept fuel injector and Jet-A fuel over a range of fuel/air ratios. This work represents the first such measurements in a high-pressure, research aero-combustor facility.

Highly durable, coking and sulfur tolerant, fuel-flexible protonic ceramic fuel cells.

PubMed

Duan, Chuancheng; Kee, Robert J; Zhu, Huayang; Karakaya, Canan; Chen, Yachao; Ricote, Sandrine; Jarry, Angelique; Crumlin, Ethan J; Hook, David; Braun, Robert; Sullivan, Neal P; O'Hayre, Ryan

2018-05-01

Protonic ceramic fuel cells, like their higher-temperature solid-oxide fuel cell counterparts, can directly use both hydrogen and hydrocarbon fuels to produce electricity at potentially more than 50 per cent efficiency 1,2 . Most previous direct-hydrocarbon fuel cell research has focused on solid-oxide fuel cells based on oxygen-ion-conducting electrolytes, but carbon deposition (coking) and sulfur poisoning typically occur when such fuel cells are directly operated on hydrocarbon- and/or sulfur-containing fuels, resulting in severe performance degradation over time 3-6 . Despite studies suggesting good performance and anti-coking resistance in hydrocarbon-fuelled protonic ceramic fuel cells 2,7,8 , there have been no systematic studies of long-term durability. Here we present results from long-term testing of protonic ceramic fuel cells using a total of 11 different fuels (hydrogen, methane, domestic natural gas (with and without hydrogen sulfide), propane, n-butane, i-butane, iso-octane, methanol, ethanol and ammonia) at temperatures between 500 and 600 degrees Celsius. Several cells have been tested for over 6,000 hours, and we demonstrate excellent performance and exceptional durability (less than 1.5 per cent degradation per 1,000 hours in most cases) across all fuels without any modifications in the cell composition or architecture. Large fluctuations in temperature are tolerated, and coking is not observed even after thousands of hours of continuous operation. Finally, sulfur, a notorious poison for both low-temperature and high-temperature fuel cells, does not seem to affect the performance of protonic ceramic fuel cells when supplied at levels consistent with commercial fuels. The fuel flexibility and long-term durability demonstrated by the protonic ceramic fuel cell devices highlight the promise of this technology and its potential for commercial application.

Low-temperature Ignition-delay Characteristics of Several Rocket Fuels with Mixed Acid in Modified Open-cup-type Apparatus

NASA Technical Reports Server (NTRS)

Miller, Riley O

1950-01-01

Summaries of low-temperature self-ignition data of various rocket fuels with mixed acid (nitric plus sulfuric) are presented. Several fuels are shown to have shorter ignition-delay intervals and less variation in delay intervals at moderate and sub-zero temperatures than crude N-ethylaniline (monoethylaniline),a rocket fuel in current use.

Electrolytes for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Fergus, Jeffrey W.

The high operating temperature of solid oxide fuel cells (SOFCs), as compared to polymer electrolyte membrane fuel cells (PEMFCs), improves tolerance to impurities in the fuel, but also creates challenges in the development of suitable materials for the various fuel cell components. In response to these challenges, intermediate temperature solid oxide fuel cells (IT-SOFCs) are being developed to reduce high-temperature material requirements, which will extend useful lifetime, improve durability and reduce cost, while maintaining good fuel flexibility. A major challenge in reducing the operating temperature of SOFCs is the development of solid electrolyte materials with sufficient conductivity to maintain acceptably low ohmic losses during operation. In this paper, solid electrolytes being developed for solid oxide fuel cells, including zirconia-, ceria- and lanthanum gallate-based materials, are reviewed and compared. The focus is on the conductivity, but other issues, such as compatibility with electrode materials, are also discussed.

Thermal protection performance of opposing jet generating with solid fuel

NASA Astrophysics Data System (ADS)

Shen, Binxian; Liu, Weiqiang

2018-03-01

A light and small gas supply device, which uses fuel gas generating with solid fuel as coolant gas, is introduced for opposing jet thermal protection in hypersonic vehicles. A numerical study on heat flux reduction in hypersonic flow with opposing jet is conducted to investigate the cooling efficiency of fuel gas. Flow field and cooling efficiency at different jet temperatures, as well as the effect of fuel gas, are determined. Detailed results show that shock stand-off distance changes with an increase in jet pressure ratio and remains constant with an increase in jet temperature. Cooling efficiency weakens with an increase in jet temperature and can be strengthened by enhancing jet pressure. Lastly, a remarkable heat flux reduction is observed with fuel gas injection with respect to no fuel gas injection when jet temperature reaches 900 K, thereby proving the positive cooling efficiency of fuel gas.

The pressure coefficient of the Curie temperature of ferromagnetic superconductors

NASA Astrophysics Data System (ADS)

Konno, R.; Hatayama, N.

2012-12-01

The pressure coefficient of the Curie temperature of ferromagnetic superconductors is studied numerically. In our previous study the pressure coefficient of the Curie temperature and that of the superconducting transition temperature were shown based on the Hamiltonian derived by Linder et al. within the mean field approximation about the electron-electron interaction analytically. There have been no numerical results of the pressure coefficient of the Curie temperature derived from the microscopic model. In this study the numerical results are reported. These results are qualitatively consistent with the experimental data in UGe2.

Experimental Study of the Stability of Aircraft Fuels at Elevated Temperatures

NASA Technical Reports Server (NTRS)

Vranos, A.; Marteney, P. J.

1980-01-01

An experimental study of fuel stability was conducted in an apparatus which simulated an aircraft gas turbine fuel system. Two fuels were tested: Jet A and Number 2 Home Heating oil. Jet A is an aircraft gas turbine fuel currently in wide use. No. 2HH was selected to represent the properties of future turbine fuels, particularly experimental Reference Broad Specification, which, under NASA sponsorship, was considered as a possible next-generation fuel. Tests were conducted with varying fuel flow rates, delivery pressures and fuel pretreatments (including preheating and deoxygenation). Simulator wall temperatures were varied between 422K and 672K at fuel flows of 0.022 to 0.22 Kg/sec. Coking rate was determined at four equally-spaced locations along the length of the simulator. Fuel samples were collected for infrared analysis. The dependence of coking rate in Jet A may be correlated with surface temperature via an activation energy of 9 to 10 kcal/mole, although the results indicate that both bulk fluid and surface temperature affect the rate of decomposition. As a consequence, flow rate, which controls bulk temperature, must also be considered. Taken together, these results suggest that the decomposition reactions are initiated on the surface and continue in the bulk fluid. The coking rate data for No. 2 HH oil are very highly temperature dependent above approximately 533K. This suggests that bulk phase reactions can become controlling in the formation of coke.

Calibration test of the temperature and strain sensitivity coefficient in regional reference grating method

NASA Astrophysics Data System (ADS)

Wu, Jing; Huang, Junbing; Wu, Hanping; Gu, Hongcan; Tang, Bo

2014-12-01

In order to verify the validity of the regional reference grating method in solve the strain/temperature cross sensitive problem in the actual ship structural health monitoring system, and to meet the requirements of engineering, for the sensitivity coefficients of regional reference grating method, national standard measurement equipment is used to calibrate the temperature sensitivity coefficient of selected FBG temperature sensor and strain sensitivity coefficient of FBG strain sensor in this modal. And the thermal expansion sensitivity coefficient of the steel for ships is calibrated with water bath method. The calibration results show that the temperature sensitivity coefficient of FBG temperature sensor is 28.16pm/°C within -10~30°C, and its linearity is greater than 0.999, the strain sensitivity coefficient of FBG strain sensor is 1.32pm/μɛ within -2900~2900μɛ whose linearity is almost to 1, the thermal expansion sensitivity coefficient of the steel for ships is 23.438pm/°C within 30~90°C, and its linearity is greater than 0.998. Finally, the calibration parameters are used in the actual ship structure health monitoring system for temperature compensation. The results show that the effect of temperature compensation is good, and the calibration parameters meet the engineering requirements, which provide an important reference for fiber Bragg grating sensor is widely used in engineering.

Aerodynamic study of state transport bus using computational fluid dynamics

NASA Astrophysics Data System (ADS)

Kanekar, Siddhesh; Thakre, Prashant; Rajkumar, E.

2017-11-01

The main purpose of this study was to develop the aerodynamic study of a Maharashtra state road transport bus. The rising fuel price and strict government regulations makes the road transport uneconomical now days. With the objective of increasing fuel efficiency and reducing the emission of harmful exhaust gases. It has been proven experimentally that vehicle consumes almost 40% of the available useful engine power to overcome the drag resistance. This provides us a huge scope to study the influence of aerodynamic drag. The initial of the project was to identify the drag coefficient of the existing ordinary type model called “Parivartan” from ANSYS fluent. After preliminary analysis of the existing model corresponding changes are made in such a way that their implementation should be possible at workshop level. The simulation of the air flow over the bus was performed in two steps: design on SolidWorks CAD and ANSYS (FLUENT) is used as a virtual analysis tool to estimate the drag coefficient of the bus. We have used the turbulence models k-ε Realizable having a better approximation of the actual result. Around 28% improvement in the drag coefficient is achieved by CFD driven changes in the bus design. Coefficient of drag is improved by 28% and fuel efficiency increased by 20% by CFD driven changes.

Low temperature fuel behavior studies

NASA Technical Reports Server (NTRS)

Stockemer, F. J.

1980-01-01

Aircraft fuels at low temperatures near the freezing point. The principal objective was an improved understanding of the flowability and pumpability of the fuels in a facility that simulated the heat transfer and temperature profiles encountered during flight in the long range commercial wing tanks.

The Effect of Weathering on Octane Quality for Winter-Grade and Summer-Grade Gasolines.

DTIC Science & Technology

1987-12-01

the following: 1. Fuels were stored at an ambient temperature 500 F and an initial (fresh fuel’ sample was taken under these conditions. Ŗ. Test...placed in the soak area and heated to a fuel temperature of 1100 F. This fuel temperature was controlled by room ambient temperature throughout the...Carl Borchers , Senior VP - Engineering FSDO #2 AVTEK Corporation 1387 Airport Boulevard S_4680 Calle Carga San Jose, CA 95110 Camarillo, CA 93010

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kwan -Soo; Spendelow, Jacob Schatz; Choe, Yoong -Kee

Here, fuel cells are promising devices for clean power generation in a variety of economically and environmentally significant applications. Low-temperature proton exchange membrane (PEM) fuel cells utilizing Nafion require a high level of hydration, which limits the operating temperature to less than 100°C. In contrast, high-temperature PEM fuel cells utilizing phosphoric acid-doped polybenzimidazole can operate effectively up to 180°C; however, these devices degrade when exposed to water below 140°C. Here we present a different class of PEM fuel cells based on quaternary ammonium-biphosphate ion pairs that can operate under conditions unattainable with existing fuel cell technologies. These fuel cells exhibitmore » stable performance at 80–160°C with a conductivity decay rate more than three orders of magnitude lower than that of a commercial high-temperature PEM fuel cell. By increasing the operational flexibility, this class of fuel cell can simplify the requirements for heat and water management, and potentially reduce the costs associated with the existing fully functional fuel cell systems.« less

Cationic Polymers Developed for Alkaline Fuel Cell Applications

DTIC Science & Technology

2015-01-20

into five categories: proton exchange membrane fuel cell ( PEMFC ), alkaline fuel cell (AFC), molten carbonate fuel cell (MCFC), solid oxide fuel...SOFC and PAFC belong to high temperature fuel cell, which can be applied in stationary power generation. PEMFC and AFC belong to low temperature fuel...function of the polymer electrolyte is to serve as electrolyte to transport ions between electrodes. PEMFC uses a polymer as electrolyte and works

Rejuvenation of automotive fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Yu Seung; Langlois, David A.

A process for rejuvenating fuel cells has been demonstrated to improve the performance of polymer exchange membrane fuel cells with platinum/ionomer electrodes. The process involves dehydrating a fuel cell and exposing at least the cathode of the fuel cell to dry gas (nitrogen, for example) at a temperature higher than the operating temperature of the fuel cell. The process may be used to prolong the operating lifetime of an automotive fuel cell.

High-freezing-point fuel studies

NASA Technical Reports Server (NTRS)

Tolle, F. F.

1980-01-01

Considerable progress in developing the experimental and analytical techniques needed to design airplanes to accommodate fuels with less stringent low temperature specifications is reported. A computer technique for calculating fuel temperature profiles in full tanks was developed. The computer program is being extended to include the case of partially empty tanks. Ultimately, the completed package is to be incorporated into an aircraft fuel tank thermal analyser code to permit the designer to fly various thermal exposure patterns, study fuel temperatures versus time, and determine holdup.

Opposed-Flow Flame Spread Across Propanol Pools: Effect of Liquid Fuel Depth

NASA Technical Reports Server (NTRS)

Kim, Inchul; Sirignano, William A.

1999-01-01

This computational study examines the effect of liquid fuel depth on flame spread across propanol pools with and without forced, opposed air flow. The initial pool temperature is below its closed- cup flash point temperature T(sub cc); so the liquid fuel must be heated sufficiently to create a combustible mixture of fuel vapor before ignition and flame spread can occur. Furthermore, in order for the flame to spread, an approximate rule is that the liquid fuel surface temperature ahead of the flame must be heated above T(sub cc) so that a flammable mixture just above the lean limit exists ahead of the flame. The depth of a liquid fuel pool would affect the heating of the liquid fuel pool and thus the liquid fuel surface temperature ahead of the flame. It has been observed experimentally and numerically that, at normal gravity without forced gas-phase flow and with the initial pool temperature T(sub 0) in a range well below T(sub cc), the flame periodically accelerates and decelerates (pulsates) as it propagates. The depth of a liquid fuel pool would change this range of T(sub 0) since it would affect the heating of the pool.

Sensitivity Analysis of Nuclide Importance to One-Group Neutron Cross Sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sekimoto, Hiroshi; Nemoto, Atsushi; Yoshimura, Yoshikane

The importance of nuclides is useful when investigating nuclide characteristics in a given neutron spectrum. However, it is derived using one-group microscopic cross sections, which may contain large errors or uncertainties. The sensitivity coefficient shows the effect of these errors or uncertainties on the importance.The equations for calculating sensitivity coefficients of importance to one-group nuclear constants are derived using the perturbation method. Numerical values are also evaluated for some important cases for fast and thermal reactor systems.Many characteristics of the sensitivity coefficients are derived from the derived equations and numerical results. The matrix of sensitivity coefficients seems diagonally dominant. However,more » it is not always satisfied in a detailed structure. The detailed structure of the matrix and the characteristics of coefficients are given.By using the obtained sensitivity coefficients, some demonstration calculations have been performed. The effects of error and uncertainty of nuclear data and of the change of one-group cross-section input caused by fuel design changes through the neutron spectrum are investigated. These calculations show that the sensitivity coefficient is useful when evaluating error or uncertainty of nuclide importance caused by the cross-section data error or uncertainty and when checking effectiveness of fuel cell or core design change for improving neutron economy.« less

Impact of hydrogen SAE J2601 fueling methods on fueling time of light-duty fuel cell electric vehicles

DOE PAGES

Reddi, Krishna; Elgowainy, Amgad; Rustagi, Neha; ...

2017-05-16

Hydrogen fuel cell electric vehicles (HFCEVs) are zero-emission vehicles (ZEVs) that can provide drivers a similar experience to conventional internal combustion engine vehicles (ICEVs), in terms of fueling time and performance (i.e. power and driving range). The Society of Automotive Engineers (SAE) developed fueling protocol J2601 for light-duty HFCEVs to ensure safe vehicle fills while maximizing fueling performance. This study employs a physical model that simulates and compares the fueling performance of two fueling methods, known as the “lookup table” method and the “MC formula” method, within the SAE J2601 protocol. Both the fueling methods provide fast fueling of HFCEVsmore » within minutes, but the MC formula method takes advantage of active measurement of precooling temperature to dynamically control the fueling process, and thereby provides faster vehicle fills. Here, the MC formula method greatly reduces fueling time compared to the lookup table method at higher ambient temperatures, as well as when the precooling temperature falls on the colder side of the expected temperature window for all station types. Although the SAE J2601 lookup table method is the currently implemented standard for refueling hydrogen fuel cell vehicles, the MC formula method provides significant fueling time advantages in certain conditions; these warrant its implementation in future hydrogen refueling stations for better customer satisfaction with fueling experience of HFCEVs.« less

Impact of hydrogen SAE J2601 fueling methods on fueling time of light-duty fuel cell electric vehicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddi, Krishna; Elgowainy, Amgad; Rustagi, Neha

Hydrogen fuel cell electric vehicles (HFCEVs) are zero-emission vehicles (ZEVs) that can provide drivers a similar experience to conventional internal combustion engine vehicles (ICEVs), in terms of fueling time and performance (i.e. power and driving range). The Society of Automotive Engineers (SAE) developed fueling protocol J2601 for light-duty HFCEVs to ensure safe vehicle fills while maximizing fueling performance. This study employs a physical model that simulates and compares the fueling performance of two fueling methods, known as the “lookup table” method and the “MC formula” method, within the SAE J2601 protocol. Both the fueling methods provide fast fueling of HFCEVsmore » within minutes, but the MC formula method takes advantage of active measurement of precooling temperature to dynamically control the fueling process, and thereby provides faster vehicle fills. Here, the MC formula method greatly reduces fueling time compared to the lookup table method at higher ambient temperatures, as well as when the precooling temperature falls on the colder side of the expected temperature window for all station types. Although the SAE J2601 lookup table method is the currently implemented standard for refueling hydrogen fuel cell vehicles, the MC formula method provides significant fueling time advantages in certain conditions; these warrant its implementation in future hydrogen refueling stations for better customer satisfaction with fueling experience of HFCEVs.« less

Mechanisms and kinetics of granulated sewage sludge combustion.

PubMed

Kijo-Kleczkowska, Agnieszka; Środa, Katarzyna; Kosowska-Golachowska, Monika; Musiał, Tomasz; Wolski, Krzysztof

2015-12-01

This paper investigates sewage sludge disposal methods with particular emphasis on combustion as the priority disposal method. Sewage sludge incineration is an attractive option because it minimizes odour, significantly reduces the volume of the starting material and thermally destroys organic and toxic components of the off pads. Additionally, it is possible that ashes could be used. Currently, as many as 11 plants use sewage sludge as fuel in Poland; thus, this technology must be further developed in Poland while considering the benefits of co-combustion with other fuels. This paper presents the results of experimental studies aimed at determining the mechanisms (defining the fuel combustion region by studying the effects of process parameters, including the size of the fuel sample, temperature in the combustion chamber and air velocity, on combustion) and kinetics (measurement of fuel temperature and mass changes) of fuel combustion in an air stream under different thermal conditions and flow rates. The combustion of the sludge samples during air flow between temperatures of 800 and 900°C is a kinetic-diffusion process. This process determines the sample size, temperature of its environment, and air velocity. The adopted process parameters, the time and ignition temperature of the fuel by volatiles, combustion time of the volatiles, time to reach the maximum temperature of the fuel surface, maximum temperature of the fuel surface, char combustion time, and the total process time, had significant impacts. Copyright © 2015 Elsevier Ltd. All rights reserved.

Study of ceria-carbonate nanocomposite electrolytes for low-temperature solid oxide fuel cells.

PubMed

Fan, L; Wang, C; Di, J; Chen, M; Zheng, J; Zhu, B

2012-06-01

Composite and nanocomposite samarium doped ceria-carbonates powders were prepared by solid-state reaction, citric acid-nitrate combustion and modified nanocomposite approaches and used as electrolytes for low temperature solid oxide fuel cells. X-ray Diffraction, Scanning Electron Microscope, low-temperature Nitrogen Adsorption/desorption Experiments, Electrochemical Impedance Spectroscopy and fuel cell performance test were employed in characterization of these materials. All powders are nano-size particles with slight aggregation and carbonates are amorphous in composites. Nanocomposite electrolyte exhibits much lower impedance resistance and higher ionic conductivity than those of the other electrolytes at lower temperature. Fuel cell using the electrolyte prepared by modified nanocomposite approach exhibits the best performance in the whole operation temperature range and achieves a maximum power density of 839 mW cm(-2) at 600 degrees C with H2 as fuel. The excellent physical and electrochemical performances of nanocomposite electrolyte make it a promising candidate for low-temperature solid oxide fuel cells.

Alternate-Fueled Combustor-Sector Performance

NASA Technical Reports Server (NTRS)

Thomas, Anna E.; Saxena, Nikita T.; Shouse, Dale T.; Neuroth, Craig; Hendricks, Robert C.; Lynch, Amy; Frayne, Charles W.; Stutrud, Jeffrey S.; Corporan, Edwin; Hankins, Terry

2013-01-01

In order to realize alternative fueling for military and commercial use, the industry has set forth guidelines that must be met by each fuel. These aviation fueling requirements are outlined in MIL-DTL-83133F(2008) or ASTM D 7566 Annex (2011) standards, and are classified as "drop-in" fuel replacements. This report provides combustor performance data for synthetic-paraffinic-kerosene- (SPK-) type (Fischer-Tropsch (FT)) fuel and blends with JP-8+100, relative to JP-8+100 as baseline fueling. Data were taken at various nominal inlet conditions: 75 psia (0.52 MPa) at 500 degF (533 K), 125 psia (0.86 MPa) at 625 degF (603 K), 175 psia (1.21 MPa) at 725 degF (658 K), and 225 psia (1.55 MPa) at 790 degF (694 K). Combustor performance analysis assessments were made for the change in flame temperatures, combustor efficiency, wall temperatures, and exhaust plane temperatures at 3, 4, and 5 percent combustor pressure drop (DP) for fuel:air ratios (F/A) ranging from 0.010 to 0.025. Significant general trends show lower liner temperatures and higher flame and combustor outlet temperatures with increases in FT fueling relative to JP-8+100 fueling. The latter affects both turbine efficiency and blade and vane lives.

Detailed studies of aviation fuel flowability

NASA Technical Reports Server (NTRS)

Mehta, H. K.; Armstrong, R. S.

1985-01-01

Six Jet A fuels, with varying compositions, were tested for low temperature flowability in a 190-liter simulator tank that modeled a section of a wing tank of a wide-body commercial airplane. The insulated tank was chilled by circulating coolant through the upper and lower surfaces. Flow-ability was determined as a function of fuel temperature by holdup, the fraction of unflowable fuel remaining in the tank after otherwise complete withdrawal. In static tests with subfreezing tank conditions, hold up varied with temperature and fuel composition. However, a general correlation of two or three classes of fuel type was obtained by plotting holdup as a function of the difference between freezing point and boundary-layer temperature, measured 0.6 cm above the bottom tank surface. Dynamic conditions of vibrations and slosh or rate of fuel withdrawal had very minor effects on holdup. Tests with cooling schedules to represent extreme, cold-day flights showed, at most, slight holdup for any combination of fuel type or dynamic conditions. Tests that superimposed external fuel heating and recirculation during the cooldown period indicates reduced hold up by modification of the low-temperature boundary layer. Fuel heating was just as effective when initiated during the later times of the tests as when applied continuously.

An operationally flexible fuel cell based on quaternary ammonium-biphosphate ion pairs

DOE PAGES

Lee, Kwan -Soo; Spendelow, Jacob Schatz; Choe, Yoong -Kee; ...

2016-08-22

Here, fuel cells are promising devices for clean power generation in a variety of economically and environmentally significant applications. Low-temperature proton exchange membrane (PEM) fuel cells utilizing Nafion require a high level of hydration, which limits the operating temperature to less than 100°C. In contrast, high-temperature PEM fuel cells utilizing phosphoric acid-doped polybenzimidazole can operate effectively up to 180°C; however, these devices degrade when exposed to water below 140°C. Here we present a different class of PEM fuel cells based on quaternary ammonium-biphosphate ion pairs that can operate under conditions unattainable with existing fuel cell technologies. These fuel cells exhibitmore » stable performance at 80–160°C with a conductivity decay rate more than three orders of magnitude lower than that of a commercial high-temperature PEM fuel cell. By increasing the operational flexibility, this class of fuel cell can simplify the requirements for heat and water management, and potentially reduce the costs associated with the existing fully functional fuel cell systems.« less

An operationally flexible fuel cell based on quaternary ammonium-biphosphate ion pairs

NASA Astrophysics Data System (ADS)

Lee, Kwan-Soo; Spendelow, Jacob S.; Choe, Yoong-Kee; Fujimoto, Cy; Kim, Yu Seung

2016-09-01

Fuel cells are promising devices for clean power generation in a variety of economically and environmentally significant applications. Low-temperature proton exchange membrane (PEM) fuel cells utilizing Nafion require a high level of hydration, which limits the operating temperature to less than 100 ∘C. In contrast, high-temperature PEM fuel cells utilizing phosphoric acid-doped polybenzimidazole can operate effectively up to 180 ∘C however, these devices degrade when exposed to water below 140 ∘C. Here we present a different class of PEM fuel cells based on quaternary ammonium-biphosphate ion pairs that can operate under conditions unattainable with existing fuel cell technologies. These fuel cells exhibit stable performance at 80-160 ∘C with a conductivity decay rate more than three orders of magnitude lower than that of a commercial high-temperature PEM fuel cell. By increasing the operational flexibility, this class of fuel cell can simplify the requirements for heat and water management, and potentially reduce the costs associated with the existing fully functional fuel cell systems.

A method for monitoring the variability in nuclear absorption characteristics of aviation fuels

NASA Technical Reports Server (NTRS)

Sprinkle, Danny R.; Shen, Chih-Ping

1988-01-01

A technique for monitoring variability in the nuclear absorption characteristics of aviation fuels has been developed. It is based on a highly collimated low energy gamma radiation source and a sodium iodide counter. The source and the counter assembly are separated by a geometrically well-defined test fuel cell. A computer program for determining the mass attenuation coefficient of the test fuel sample, based on the data acquired for a preset counting period, has been developed and tested on several types of aviation fuel.

Monolithic Solid Oxide Fuel Cell development

NASA Technical Reports Server (NTRS)

Myles, K. M.; Mcpheeters, C. C.

1989-01-01

The Monolithic Solid Oxide Fuel Cell (MSOFC) is an oxide-ceramic structure in which appropriate electronic and ionic conductors are fabricated in a honeycomb shape similar to a block of corrugated paperboard. These electronic and ionic conductors are arranged to provide short conduction paths to minimize resistive losses. The power density achievable with the MSOFC is expected to be about 8 kW/kg or 4 kW/L, at fuel efficienceis over 50 percent, because of small cell size and low resistive losses in the materials. The MSOFC operates in the range of 700 to 1000 C, at which temperatures rapid reform of hydrocarbon fuels is expected within the nickel-YSZ fuel channels. Tape casting and hot roll calendering are used to fabricate the MSOFC structure. The performance of the MSOFC has improved significantly during the course of development. The limitation of this system, based on materials resistance alone without interfacial resistances, is 0.093 ohm-sq cm area-specific resistance (ASR). The current typical performance of MSOFC single cells is characterized by ASRs of about 0.4 to 0.5 ohm-sq cm. With further development the ASR is expected to be reduced below 0.2 ohm-sq cm, which will result in power levels greater than 1.4 W/sq cm. The feasibility of the MSOFC concept was proven, and the performance was dramatically improved. The differences in thermal expansion coefficients and firing shrinkages among the fuel cell materials were minimized. As a result of good matching of these properties, the MSOFC structure was successfully fabricated with few defects, and the system shows excellent promise for development into a practical power source.

A perspective on the range of gasoline compression ignition combustion strategies for high engine efficiency and low NOx and soot emissions: Effects of in-cylinder fuel stratification

DOE PAGES

Dempsey, Adam B.; Curran, Scott J.; Wagner, Robert M.

2016-01-14

Many research studies have shown that low temperature combustion in compression ignition engines has the ability to yield ultra-low NOx and soot emissions while maintaining high thermal efficiency. To achieve low temperature combustion, sufficient mixing time between the fuel and air in a globally dilute environment is required, thereby avoiding fuel-rich regions and reducing peak combustion temperatures, which significantly reduces soot and NOx formation, respectively. It has been demonstrated that achieving low temperature combustion with diesel fuel over a wide range of conditions is difficult because of its properties, namely, low volatility and high chemical reactivity. On the contrary, gasolinemore » has a high volatility and low chemical reactivity, meaning it is easier to achieve the amount of premixing time required prior to autoignition to achieve low temperature combustion. In order to achieve low temperature combustion while meeting other constraints, such as low pressure rise rates and maintaining control over the timing of combustion, in-cylinder fuel stratification has been widely investigated for gasoline low temperature combustion engines. The level of fuel stratification is, in reality, a continuum ranging from fully premixed (i.e. homogeneous charge of fuel and air) to heavily stratified, heterogeneous operation, such as diesel combustion. However, to illustrate the impact of fuel stratification on gasoline compression ignition, the authors have identified three representative operating strategies: partial, moderate, and heavy fuel stratification. Thus, this article provides an overview and perspective of the current research efforts to develop engine operating strategies for achieving gasoline low temperature combustion in a compression ignition engine via fuel stratification. In this paper, computational fluid dynamics modeling of the in-cylinder processes during the closed valve portion of the cycle was used to illustrate the opportunities and challenges associated with the various fuel stratification levels.« less

A perspective on the range of gasoline compression ignition combustion strategies for high engine efficiency and low NOx and soot emissions: Effects of in-cylinder fuel stratification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dempsey, Adam B.; Curran, Scott J.; Wagner, Robert M.

Many research studies have shown that low temperature combustion in compression ignition engines has the ability to yield ultra-low NOx and soot emissions while maintaining high thermal efficiency. To achieve low temperature combustion, sufficient mixing time between the fuel and air in a globally dilute environment is required, thereby avoiding fuel-rich regions and reducing peak combustion temperatures, which significantly reduces soot and NOx formation, respectively. It has been demonstrated that achieving low temperature combustion with diesel fuel over a wide range of conditions is difficult because of its properties, namely, low volatility and high chemical reactivity. On the contrary, gasolinemore » has a high volatility and low chemical reactivity, meaning it is easier to achieve the amount of premixing time required prior to autoignition to achieve low temperature combustion. In order to achieve low temperature combustion while meeting other constraints, such as low pressure rise rates and maintaining control over the timing of combustion, in-cylinder fuel stratification has been widely investigated for gasoline low temperature combustion engines. The level of fuel stratification is, in reality, a continuum ranging from fully premixed (i.e. homogeneous charge of fuel and air) to heavily stratified, heterogeneous operation, such as diesel combustion. However, to illustrate the impact of fuel stratification on gasoline compression ignition, the authors have identified three representative operating strategies: partial, moderate, and heavy fuel stratification. Thus, this article provides an overview and perspective of the current research efforts to develop engine operating strategies for achieving gasoline low temperature combustion in a compression ignition engine via fuel stratification. In this paper, computational fluid dynamics modeling of the in-cylinder processes during the closed valve portion of the cycle was used to illustrate the opportunities and challenges associated with the various fuel stratification levels.« less

Evidence for a high temperature differentiation in a molten earth: A preliminary appraisal

NASA Technical Reports Server (NTRS)

Murthy, V. Rama

1992-01-01

If the earth were molten during its later stages of accretion as indicated by the present understanding of planetary accretion process, the differentiation that led to the formation of the core and mantle must have occurred at high temperatures in the range of 3000-5000 K because of the effect of pressure on the temperature of melting in the interior of the earth. This calls into question the use of low-temperature laboratory measurements of partition coefficients of trace elements to make inferences about earth accretion and differentiation. The low temperature partition coefficients cannot be directly applied to high temperature fractionations because partition coefficients refer to an equilibrium specific to a temperature for a given reaction, and must change in some proportion to exp 1/RT. There are no laboratory data on partition coefficients at the high temperatures relevant to differentiation in the interior of the earth, and an attempt to estimate high temperature distribution coefficients of siderophile elements was made by considering the chemical potential of a given element at equilibrium and how this potential changes with temperature, under some specific assumptions.

Dynamic, Hot Surface Ignition of Aircraft Fuels and Hydraulic Fluids

DTIC Science & Technology

1980-10-01

fuels on a heated stainless steel surface. Higher local surface air speeds necessitated higher surface temperatures for ignition of an applied fluid._-7...Aircraft Fuels ( stainless steel surface) 8. Air Speed and Surface Material Effects on Hot Surface 21 Ignition Temperature of Aircraft Fuels (Titanium...Material Effects on Hot Surface 26 Ignition Temperature of Aircraft Hydraulic Fluids ( Stainless steel surface) 11. Air Speed and Surface Material

Strength and Fracture Toughness of Solid Oxide Fuel Cell Electrolyte Material Improved

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Choi, Sung R.

2002-01-01

Solid oxide fuel cells (SOFC) are being developed for various applications in the automobile, power-generation, and aeronautics industries. Recently, the NASA Glenn Research Center has been exploring the possibility of using SOFC's for aeropropulsion under its Zero Carbon Dioxide Emission Technology (ZCET) Program. 10-mol% yttriastabilized zirconia (10YSZ) is a very good anionic conductor at high temperatures and is, therefore, used as an oxygen solid electrolyte in SOFC. However, it has a high thermal expansion coefficient, low thermal shock resistance, low fracture toughness, and poor mechanical strength. For aeronautic applications, the thin ceramic electrolyte membrane of the SOFC needs to be strong and tough. Therefore, we have been investigating the possibility of enhancing the strength and fracture toughness of the 10YSZ electrolyte without degrading its electrical conductivity to an appreciable extent. We recently demonstrated that the addition of alumina to zirconia electrolyte increases its strength as well as its fracture toughness. Zirconia-alumina composites containing 0 to 30 mol% of alumina were fabricated by hot pressing. The hot pressing procedure was developed and various hot pressing parameters were optimized, resulting in dense, crackfree panels of composite materials. Cubic zirconia and a-alumina were the only phases detected, indicating that there was no chemical reaction between the constituents during hot pressing at elevated temperatures. Flexure strength sf and fracture toughness K(sub IC) of the various zirconia-alumina composites were measured at room temperature as well as at 1000 C in air. Both properties showed systematic improvement with increased alumina addition at room temperature and at 1000 C. Use of these modified electrolytes with improved strength and fracture toughness should prolong the life and enhance the performance of SOFC in aeronautics and other applications.

Combustion studies of coal derived solid fuels by thermogravimetric analysis. III. Correlation between burnout temperature and carbon combustion efficiency

USGS Publications Warehouse

Rostam-Abadi, M.; DeBarr, J.A.; Chen, W.T.

1990-01-01

Burning profiles of 35-53 ??m size fractions of an Illinois coal and three partially devolatilized coals prepared from the original coal were obtained using a thermogravimetric analyzer. The burning profile burnout temperatures were higher for lower volatile fuels and correlated well with carbon combustion efficiencies of the fuels when burned in a laboratory-scale laminar flow reactor. Fuels with higher burnout temperatures had lower carbon combustion efficiencies under various time-temperature conditions in the laboratory-scale reactor. ?? 1990.

Propellant vaporization as a criterion for rocket-engine design : experimental effect of fuel temperature on liquid-oxygen - heptane performance

NASA Technical Reports Server (NTRS)

Heidmann, M F

1957-01-01

Characteristic exhaust velocity of a 200-pound-thrust rocket engine was evaluated for fuel temperatures of -90 degrees, and 200 degrees f with a spray formed by two impinging heptane jets reacting in a highly atomized oxygen atmosphere. Tests covered a range of mixture ratios and chamber lengths. The characteristic exhaust-velocity efficiency increased 2 percent for a 290 degree f increase in fuel temperature. This increase in performance can be compared with that obtained by increasing chamber length by about 1/2 inch. The result agrees with the fuel-temperature effect predicted from an analysis based on droplet evaporation theory. Mixture ratio markedly affected characteristic exhaust velocity efficiency, but total flow rate and fuel temperature did not.

Nuclear fuel elements made from nanophase materials

DOEpatents

Heubeck, Norman B.

1998-01-01

A nuclear reactor core fuel element is composed of nanophase high temperature materials. An array of the fuel elements in rod form are joined in an open geometry fuel cell that preferably also uses such nanophase materials for the cell structures. The particular high temperature nanophase fuel element material must have the appropriate mechanical characteristics to avoid strain related failure even at high temperatures, in the order of about 3000.degree. F. Preferably, the reactor type is a pressurized or boiling water reactor and the nanophase material is a high temperature ceramic or ceramic composite. Nanophase metals, or nanophase metals with nanophase ceramics in a composite mixture, also have desirable characteristics, although their temperature capability is not as great as with all-ceramic nanophase material. Combinations of conventional or nanophase metals and conventional or nanophase ceramics can be employed as long as there is at least one nanophase material in the composite. The nuclear reactor so constructed has a number of high strength fuel particles, a nanophase structural material for supporting a fuel rod at high temperature, a configuration to allow passive cooling in the event of a primary cooling system failure, an ability to retain a coolable geometry even at high temperatures, an ability to resist generation of hydrogen gas, and a configuration having good nuclear, corrosion, and mechanical characteristics.

Nuclear fuel elements made from nanophase materials

DOEpatents

Heubeck, N.B.

1998-09-08

A nuclear reactor core fuel element is composed of nanophase high temperature materials. An array of the fuel elements in rod form are joined in an open geometry fuel cell that preferably also uses such nanophase materials for the cell structures. The particular high temperature nanophase fuel element material must have the appropriate mechanical characteristics to avoid strain related failure even at high temperatures, in the order of about 3000 F. Preferably, the reactor type is a pressurized or boiling water reactor and the nanophase material is a high temperature ceramic or ceramic composite. Nanophase metals, or nanophase metals with nanophase ceramics in a composite mixture, also have desirable characteristics, although their temperature capability is not as great as with all-ceramic nanophase material. Combinations of conventional or nanophase metals and conventional or nanophase ceramics can be employed as long as there is at least one nanophase material in the composite. The nuclear reactor so constructed has a number of high strength fuel particles, a nanophase structural material for supporting a fuel rod at high temperature, a configuration to allow passive cooling in the event of a primary cooling system failure, an ability to retain a coolable geometry even at high temperatures, an ability to resist generation of hydrogen gas, and a configuration having good nuclear, corrosion, and mechanical characteristics. 5 figs.

--No Title--

Science.gov Websites

$stitle set definition sets G Power Generators /gen1*gen2/ F Fuels /oil,gas/ K Constants in Fuel better TABLE A(G,F,K) Coefficients in the fuel consumption equations 0 1 gen1.oil 1.4609 .18223 gen1.gas 1.5742 .19572 gen2.oil 0.8008 .24372 gen2.gas 0.7266 .27072; PARAMETER PMAX(G) Maximum power outputs of

Real Time Monitoring of Temperature of a Micro Proton Exchange Membrane Fuel Cell

PubMed Central

Lee, Chi-Yuan; Lee, Shuo-Jen; Hu, Yuh-Chung; Shih, Wen-Pin; Fan, Wei-Yuan; Chuang, Chih-Wei

2009-01-01

Silicon micro-hole arrays (Si-MHA) were fabricated as a gas diffusion layer (GDL) in a micro fuel cell using the micro-electro-mechanical-systems (MEMS) fabrication technique. The resistance temperature detector (RTD) sensor was integrated with the GDL on a bipolar plate to measure the temperature inside the fuel cell. Experimental results demonstrate that temperature was generally linearly related to resistance and that accuracy and sensitivity were within 0.5 °C and 1.68×10−3/°C, respectively. The best experimental performance was 9.37 mW/cm2 at an H2/O2 dry gas flow rate of 30/30 SCCM. Fuel cell temperature during operation was 27 °C, as measured using thermocouples in contact with the backside of the electrode. Fuel cell operating temperature measured in situ was 30.5 °C. PMID:22573963

POWER BREEDER REACTOR

DOEpatents

Monson, H.O.

1960-11-22

An arrangement is offered for preventing or minimizing the contraction due to temperature rise, of a reactor core comprising vertical fuel rods in sodium. Temperature rise of the fuel rods would normally make them move closer together by inward bowing, with a resultant undesired increase in reactivity. According to the present invention, assemblies of the fuel rods are laterally restrained at the lower ends of their lower blanket sections and just above the middle of the fuel sections proper of the rods, and thus the fuel sections move apart, rather than together, with increase in temperature.

Effect of Dissolved Oxygen on the Filterability of Jet Fuels for Temperatures Between 300 Degrees and 400 Degrees F

NASA Technical Reports Server (NTRS)

Mckeown, Anderson B; Hibbard, Robert R

1955-01-01

The effect of dissolved oxygen in the filter-clogging characteristics of three JP-4 and two JP-5 fuels was studied at 300 degrees to 400 degrees F in a bench- scale rig, employing filter paper as the filter medium. The residence time of the fuel at the high temperature was approximately 6 seconds. For these conditions, the clogging characteristics of the fuels increased with both increasing temperature and increasing concentration of dissolved oxygen. The amount of insoluble material formed at high temperatures necessary to produce clogging of filters was very small, of the order of 1 milligram per gallon of fuel.

Additional experiments on flowability improvements of aviation fuels at low temperatures, volume 2

NASA Technical Reports Server (NTRS)

Stockemer, F. J.; Deane, R. L.

1982-01-01

An investigation was performed to study flow improver additives and scale-model fuel heating systems for use with aviation hydrocarbon fuel at low temperatures. Test were performed in a facility that simulated the heat transfer and temperature profiles anticipated in wing fuel tanks during flight of long-range commercial aircraft. The results are presented of experiments conducted in a test tank simulating a section of an outer wing integral fuel tank approximately full-scale in height, chilled through heat exchange panels bonded to the upper and lower horizontal surfaces. A separate system heated lubricating oil externally by a controllable electric heater, to transfer heat to fuel pumped from the test tank through an oil-to-fuel heat exchanger, and to recirculate the heated fuel back to the test tank.

Quartz tuning-fork oscillations in He II and drag coefficient

NASA Astrophysics Data System (ADS)

Gritsenko, I. A.; Zadorozhko, A. A.; Neoneta, A. S.; Chagovets, V. K.; Sheshin, G. A.

2011-07-01

The temperature dependencies of drag coefficient for quartz tuning forks of various geometric dimensions, immersed in the He II, were determined experimentally in the temperature range 0.1-3 K. It is identified, that these dependencies are similar, but the values of drag coefficient are different for tuning forks with different geometric dimensions. It is shown, that the obtained specific drag coefficient depends only on the temperature and frequency of vibrations, when the value of drag coefficient is normalized to the surface area of moving tuning-fork prong. The temperature dependencies of normalized drag coefficient for the tuning forks of various dimensions, wire, and microsphere, oscillating in the Не II, are compared. It is shown, that in the ballistic regime of scattering of quasiparticles, these dependencies are identical and have a slope proportional to T4, which is determined by the density of thermal excitations. In the hydrodynamic regime at T > 0.5 K, the behavior of the temperature dependence of specific drag coefficient is affected by the size and frequency of vibrating body. The empirical relation, which allows to describe the behavior of specific drag coefficient for vibrating tuning forks, microsphere, and wire everywhere over the temperature region and at various frequencies, is proposed.

Method for cold stable biojet fuel

DOEpatents

Seames, Wayne S.; Aulich, Ted

2015-12-08

Plant or animal oils are processed to produce a fuel that operates at very cold temperatures and is suitable as an aviation turbine fuel, a diesel fuel, a fuel blendstock, or any fuel having a low cloud point, pour point or freeze point. The process is based on the cracking of plant or animal oils or their associated esters, known as biodiesel, to generate lighter chemical compounds that have substantially lower cloud, pour, and/or freeze points than the original oil or biodiesel. Cracked oil is processed using separation steps together with analysis to collect fractions with desired low temperature properties by removing undesirable compounds that do not possess the desired temperature properties.

Cryogenic fiber optic temperature sensor and method of manufacturing the same

NASA Technical Reports Server (NTRS)

Kochergin, Vladimir (Inventor)

2012-01-01

This invention teaches the fiber optic sensors temperature sensors for cryogenic temperature range with improved sensitivity and resolution, and method of making said sensors. In more detail, the present invention is related to enhancement of temperature sensitivity of fiber optic temperature sensors at cryogenic temperatures by utilizing nanomaterials with a thermal expansion coefficient that is smaller than the thermal expansion coefficient of the optical fiber but larger in absolute value than the thermal expansion coefficient of the optical fiber at least over a range of temperatures.

Thermal Analysis of a TREAT Fuel Assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Papadias, Dionissios; Wright, Arthur E.

2014-07-09

The objective of this study was to explore options as to reduce peak cladding temperatures despite an increase in peak fuel temperatures. A 3D thermal-hydraulic model for a single TREAT fuel assembly was benchmarked to reproduce results obtained with previous thermal models developed for a TREAT HEU fuel assembly. In exercising this model, and variants thereof depending on the scope of analysis, various options were explored to reduce the peak cladding temperatures.

An experimental approach to determine the heat transfer coefficient in directional solidification furnaces

NASA Technical Reports Server (NTRS)

Banan, Mohsen; Gray, Ross T.; Wilcox, William R.

1992-01-01

The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was experimentally determined using in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zone to a lower temperature zone. The temperature-time history was used in a lumped-capacity cooling model to evaluate the heat transfer coefficient between the charge and the furnace. The experimentally determined heat transfer coefficient was of the same order of magnitude as the theoretical value estimated by standard heat transfer calculations.

Detailed Multi-dimensional Modeling of Direct Internal Reforming Solid Oxide Fuel Cells.

PubMed

Tseronis, K; Fragkopoulos, I S; Bonis, I; Theodoropoulos, C

2016-06-01

Fuel flexibility is a significant advantage of solid oxide fuel cells (SOFCs) and can be attributed to their high operating temperature. Here we consider a direct internal reforming solid oxide fuel cell setup in which a separate fuel reformer is not required. We construct a multidimensional, detailed model of a planar solid oxide fuel cell, where mass transport in the fuel channel is modeled using the Stefan-Maxwell model, whereas the mass transport within the porous electrodes is simulated using the Dusty-Gas model. The resulting highly nonlinear model is built into COMSOL Multiphysics, a commercial computational fluid dynamics software, and is validated against experimental data from the literature. A number of parametric studies is performed to obtain insights on the direct internal reforming solid oxide fuel cell system behavior and efficiency, to aid the design procedure. It is shown that internal reforming results in temperature drop close to the inlet and that the direct internal reforming solid oxide fuel cell performance can be enhanced by increasing the operating temperature. It is also observed that decreases in the inlet temperature result in smoother temperature profiles and in the formation of reduced thermal gradients. Furthermore, the direct internal reforming solid oxide fuel cell performance was found to be affected by the thickness of the electrochemically-active anode catalyst layer, although not always substantially, due to the counter-balancing behavior of the activation and ohmic overpotentials.

Effect of in-pile degradation of the meat thermal conductivity on the maximum temperature of the plate-type U-Mo dispersion fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavel G. Medvedev

2009-11-01

Effect of in-pile degradation of thermal conductivity on the maximum temperature of the plate-type research reactor fuels has been assessed using the steady-state heat conduction equation and assuming convection cooling. It was found that due to very low meat thickness, characteristic for this type of fuel, the effect of thermal conductivity degradation on the maximum fuel temperature is minor. For example, the fuel plate featuring 0.635 mm thick meat operating at heat flux of 600 W/cm2 would experience only a 20oC temperature rise if the meat thermal conductivity degrades from 0.8 W/cm-s to 0.3 W/cm-s. While degradation of meat thermalmore » conductivity in dispersion-type U-Mo fuel can be very substantial due to formation of interaction layer between the particles and the matrix, and development of fission gas filled porosity, this simple analysis demonstrates that this phenomenon is unlikely to significantly affect the temperature-based safety margin of the fuel during normal operation.« less

Direct Numerical Simulation of Turbulent Multi-Stage Autoignition Relevant to Engine Conditions

NASA Astrophysics Data System (ADS)

Chen, Jacqueline

2017-11-01

Due to the unrivaled energy density of liquid hydrocarbon fuels combustion will continue to provide over 80% of the world's energy for at least the next fifty years. Hence, combustion needs to be understood and controlled to optimize combustion systems for efficiency to prevent further climate change, to reduce emissions and to ensure U.S. energy security. In this talk I will discuss recent progress in direct numerical simulations of turbulent combustion focused on providing fundamental insights into key `turbulence-chemistry' interactions that underpin the development of next generation fuel efficient, fuel flexible engines for transportation and power generation. Petascale direct numerical simulation (DNS) of multi-stage mixed-mode turbulent combustion in canonical configurations have elucidated key physics that govern autoignition and flame stabilization in engines and provide benchmark data for combustion model development under the conditions of advanced engines which operate near combustion limits to maximize efficiency and minimize emissions. Mixed-mode combustion refers to premixed or partially-premixed flames propagating into stratified autoignitive mixtures. Multi-stage ignition refers to hydrocarbon fuels with negative temperature coefficient behavior that undergo sequential low- and high-temperature autoignition. Key issues that will be discussed include: 1) the role of mixing in shear driven turbulence on the dynamics of multi-stage autoignition and cool flame propagation in diesel environments, 2) the role of thermal and composition stratification on the evolution of the balance of mixed combustion modes - flame propagation versus spontaneous ignition - which determines the overall combustion rate in autoignition processes, and 3) the role of cool flames on lifted flame stabilization. Finally prospects for DNS of turbulent combustion at the exascale will be discussed in the context of anticipated heterogeneous machine architectures. sponsored by DOE Office of Basic Energy Sciences and computing resources provided by the Oakridge Leadership Computing Facility through the DOE INCITE Program.

ECAS Phase I fuel cell results. [Energy Conservation Alternatives Study

NASA Technical Reports Server (NTRS)

Warshay, M.

1978-01-01

This paper summarizes and discusses the fuel cell system results of Phase I of the Energy Conversion Alternatives Study (ECAS). Ten advanced electric powerplant systems for central-station baseload generation using coal were studied by NASA in ECAS. Three types of low-temperature fuel cells (solid polymer electrolyte, SPE, aqueous alkaline, and phosphoric acid) and two types of high-temperature fuel cells (molten carbonate, MC, and zirconia solid electrolyte, SE) were studied. The results indicate that (1) overall efficiency increases with fuel cell temperature, and (2) scale-up in powerplant size can produce a significant reduction in cost of electricity (COE) only when it is accompanied by utilization of waste fuel cell heat through a steam bottoming cycle and/or integration with a gasifier. For low-temperature fuel cell systems, the use of hydrogen results in the highest efficiency and lowest COE. In spite of higher efficiencies, because of higher fuel cell replacement costs integrated SE systems have higher projected COEs than do integrated MC systems. Present data indicate that life can be projected to over 30,000 hr for MC fuel cells, but data are not yet sufficient for similarly projecting SE fuel cell life expectancy.

The effect of azeotropism on combustion characteristics of blended fuel pool fire.

PubMed

Ding, Yanming; Wang, Changjian; Lu, Shouxiang

2014-04-30

The effect of azeotropism on combustion characteristics of blended fuel pool fire was experimentally studied in an open fire test space of State Key Laboratory of Fire Science. A 30 cm × 30 cm square pool filled with n-heptane and ethanol blended fuel was employed. Flame images, burning rate and temperature distribution were collected and recorded in the whole combustion process. Results show that azeotropism obviously dominates the combustion behavior of n-heptane/ethanol blended fuel pool fire. The combustion process after ignition exhibits four typical stages: initial development, azeotropic burning, single-component burning and decay stage. Azeotropism appears when temperature of fuel surface reaches azeotropic point and blended fuel burns at azeotropic ratio. Compared with individual pure fuel, the effect of azeotropism on main fire parameters, such as flame height, burning rate, flame puffing frequency and centerline temperature were analyzed. Burning rate and centerline temperature of blended fuel are higher than that of individual pure fuel respectively at azeotropic burning stage, and flame puffing frequency follows the empirical formula between Strouhal and Froude number for pure fuel. Copyright © 2014 Elsevier B.V. All rights reserved.

Fuel temperature counter

Treesearch

John R. Murray; Charles W. Philpot

1963-01-01

Fuel temperature is and has always been difficult to measure. To understand better the problem of fire and fire weather behavior, it is important to measure this variable. We have developed for field use a new fuel temperature counter which can be used to obtain such measurements quickly and easily. This electronic recording instrument is easy to construct and operate...

Heating and Efficiency Comparison of a Fischer-Tropsch (FT) Fuel, JP-8+100, and Blends in a Three-Cup Combustor Sector

NASA Technical Reports Server (NTRS)

Thomas, Anna E.; Shouse, Dale T.; Neuroth, Craig; Lynch, Amy; Frayne, Charles W.; Stutrud, Jeffrey S.; Corporan, Edwin; Hankins, Terry; Saxena, Nikita T.; Hendricks, Robert C.

2012-01-01

In order to realize alternative fueling for military and commercial use, the industry has set forth guidelines that must be met by each fuel. These aviation fueling requirements are outlined in MIL-DTL-83133F(2008) or ASTM D 7566-Annex standards and are classified as drop-in fuel replacements. This paper provides combustor performance data for synthetic-paraffinic-kerosene- (SPK-) type (Fisher-Tropsch (FT)) fuel and blends with JP-8+100, relative to JP-8+100 as baseline fueling. Data were taken at various nominal inlet conditions: 75 psia (0.52 MPa) at 500 aF (533 K), 125 psia (0.86 MPa) at 625 aF (603 K), 175 psia (1.21 MPa) at 725 aF (658 K), and 225 psia (1.55 MPa) at 790 aF (694 K). Combustor performance analysis assessments were made for the change in flame temperatures, combustor efficiency, wall temperatures, and exhaust plane temperatures at 3%, 4%, and 5% combustor pressure drop (% P) for fuel:air ratios (F/A) ranging from 0.010 to 0.025. Significant general trends show lower liner temperatures and higher flame and combustor outlet temperatures with increases in FT fueling relative to JP-8+100 fueling. The latter affects both turbine efficiency and blade/vane life. In general, 100% SPK-FT fuel and blends with JP-8+100 produce less particulates and less smoke and have lower thermal impact on combustor hardware.

Experimental investigation on circumferential and axial temperature gradient over fuel channel under LOCA

NASA Astrophysics Data System (ADS)

Yadav, Ashwini Kumar; kumar, Ravi; Gupta, Akhilesh; Chatterjee, Barun; Mukhopadhyay, Deb; Lele, H. G.

2014-06-01

In a nuclear reactor temperature rises drastically in fuel channels under loss of coolant accident due to failure of primary heat transportation system. Present investigation has been carried out to capture circumferential and axial temperature gradients during fully and partially voiding conditions in a fuel channel using 19 pin fuel element simulator. A series of experiments were carried out by supplying power to outer, middle and center rods of 19 pin fuel simulator in ratio of 1.4:1.1:1. The temperature at upper periphery of pressure tube (PT) was slightly higher than at bottom due to increase in local equivalent thermal conductivity from top to bottom of PT. To simulate fully voided conditions PT was pressurized at 2.0 MPa pressure with 17.5 kW power injection. Ballooning initiated from center and then propagates towards the ends and hence axial temperature difference has been observed along the length of PT. For asymmetric heating, upper eight rods of fuel simulator were activated and temperature difference up-to 250 °C has been observed from top to bottom periphery of PT. Such situation creates steep circumferential temperature gradient over PT and could lead to breaching of PT under high pressure.

Improving Prompt Temperature Feedback by Stimulating Doppler Broadening in Heterogeneous Composite Nuclear Fuel Forms

NASA Astrophysics Data System (ADS)

Morrison, Christopher

Nuclear fuels with similar aggregate material composition, but with different millimeter and micrometer spatial configurations of the component materials can have very different safety and performance characteristics. This research focuses on modeling and attempting to engineer heterogeneous combinations of nuclear fuels to improve negative prompt temperature feedback in response to reactivity insertion accidents. Improvements in negative prompt temperature feedback are proposed by developing a tailored thermal resistance in the nuclear fuel. In the event of a large reactivity insertion, the thermal resistance allows for a faster negative Doppler feedback by temporarily trapping heat in material zones with strong absorption resonances. A multi-physics simulation framework was created that could model large reactivity insertions. The framework was then used to model a comparison of a heterogeneous fuel with a tailored thermal resistance and a homogeneous fuel without the tailored thermal resistance. The results from the analysis confirmed the fundamental premise of prompt temperature feedback and provide insights into the neutron spectrum dynamics throughout the transient process. A trade study was conducted on infinite lattice fuels to help map a design space to study and improve prompt temperature feedback with many results. A multi-scale fuel pin analysis was also completed to study more realistic geometries. The results of this research could someday allow for novel nuclear fuels that would behave differently than current fuels. The idea of having a thermal barrier coating in the fuel is contrary to most current thinking. Inherent resistance to reactivity insertion accidents could enable certain reactor types once considered vulnerable to reactivity insertion accidents to be reevaluated in light of improved negative prompt temperature feedback.

40 CFR 86.213-11 - Fuel specifications.

Code of Federal Regulations, 2011 CFR

2011-07-01

...-Duty Passenger Vehicles; Cold Temperature Test Procedures § 86.213-11 Fuel specifications. (a) Gasoline... the text in this section follows: Table—Cold CO Fuel Specifications Item ASTM test Cold CO low octane.... Diesel test fuel used for cold temperature FTP testing under part 600 of this chapter must be a winter...

40 CFR 86.213-11 - Fuel specifications.

Code of Federal Regulations, 2013 CFR

2013-07-01

...-Duty Passenger Vehicles; Cold Temperature Test Procedures § 86.213-11 Fuel specifications. (a) Gasoline... the text in this section follows: Table—Cold CO Fuel Specifications Item ASTM test Cold CO low octane.... Diesel test fuel used for cold temperature FTP testing under part 600 of this chapter must be a winter...

40 CFR 86.213-11 - Fuel specifications.

Code of Federal Regulations, 2010 CFR

2010-07-01

...-Duty Passenger Vehicles; Cold Temperature Test Procedures § 86.213-11 Fuel specifications. (a) Gasoline... the text in this section follows: Table—Cold CO Fuel Specifications Item ASTM test Cold CO low octane.... Diesel test fuel used for cold temperature FTP testing under part 600 of this chapter must be a winter...

40 CFR 86.131-96 - Vehicle preparation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Heavy-Duty Vehicles; Test Procedures § 86.131-96 Vehicle preparation. (a) For gasoline- and methanol-fueled vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be...

40 CFR 86.131-96 - Vehicle preparation.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Heavy-Duty Vehicles; Test Procedures § 86.131-96 Vehicle preparation. (a) For gasoline- and methanol-fueled vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be...

40 CFR 86.131-96 - Vehicle preparation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Heavy-Duty Vehicles; Test Procedures § 86.131-96 Vehicle preparation. (a) For gasoline- and methanol-fueled vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be...

40 CFR 86.131-96 - Vehicle preparation.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Heavy-Duty Vehicles; Test Procedures § 86.131-96 Vehicle preparation. (a) For gasoline- and methanol-fueled vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be...

40 CFR 86.213-11 - Fuel specifications.

Code of Federal Regulations, 2012 CFR

2012-07-01

...-Duty Passenger Vehicles; Cold Temperature Test Procedures § 86.213-11 Fuel specifications. (a) Gasoline... the text in this section follows: Table—Cold CO Fuel Specifications Item ASTM test Cold CO low octane.... Diesel test fuel used for cold temperature FTP testing under part 600 of this chapter must be a winter...

40 CFR 86.131-96 - Vehicle preparation.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Heavy-Duty Vehicles; Test Procedures § 86.131-96 Vehicle preparation. (a) For gasoline- and methanol-fueled vehicles prepare the fuel tank(s) for recording the temperature of the prescribed test fuel, as... optional during the running loss test. If vapor temperature is not measured, fuel tank pressure need not be...

Solid oxide fuel cell operable over wide temperature range

DOEpatents

Baozhen, Li; Ruka, Roswell J.; Singhal, Subhash C.

2001-01-01

Solid oxide fuel cells having improved low-temperature operation are disclosed. In one embodiment, an interfacial layer of terbia-stabilized zirconia is located between the air electrode and electrolyte of the solid oxide fuel cell. The interfacial layer provides a barrier which controls interaction between the air electrode and electrolyte. The interfacial layer also reduces polarization loss through the reduction of the air electrode/electrolyte interfacial electrical resistance. In another embodiment, the solid oxide fuel cell comprises a scandia-stabilized zirconia electrolyte having high electrical conductivity. The scandia-stabilized zirconia electrolyte may be provided as a very thin layer in order to reduce resistance. The scandia-stabilized electrolyte is preferably used in combination with the terbia-stabilized interfacial layer. The solid oxide fuel cells are operable over wider temperature ranges and wider temperature gradients in comparison with conventional fuel cells.

Temperature dependence of damage coefficient in electron irradiated solar cells

NASA Technical Reports Server (NTRS)

Faith, T. J.

1973-01-01

Measurements of light-generated current vs cell temperature on electron-irradiated n/p silicon solar cells show the temperature coefficient of this current to increase with increasing fluence for both 10-ohm and 20-ohm cells. A relationship between minority-carrier diffusion length and light-generated current was derived by combining measurements of these two parameters: vs fluence at room temperature, and vs cell temperature in cells irradiated to a fluence of 1 x 10 to the 15th power e/sq cm. This relationship was used, together with the light-generated current data, to calculate the temperature dependence of the diffusion-length damage coefficient. The results show a strong decrease in the damage coefficient with increasing temperature in the range experienced by solar panels in synchronous earth orbit.

Steady-State Thermal-Hydraulics Analyses for the Conversion of BR2 to Low Enriched Uranium Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Licht, J.; Bergeron, A.; Dionne, B.

The code PLTEMP/ANL version 4.2 was used to perform the steady-state thermal-hydraulic analyses of the BR2 research reactor for conversion from Highly-Enriched to Low Enriched Uranium fuel (HEU and LEU, respectively). Calculations were performed to evaluate different fuel assemblies with respect to the onset of nucleate boiling (ONB), flow instability (FI), critical heat flux (CHF) and fuel temperature at beginning of cycle conditions. The fuel assemblies were characteristic of fresh fuel (0% burnup), highest heat flux (16% burnup), highest power (32% burnup) and highest burnup (46% burnup). Results show that the high heat flux fuel element is limiting for ONB,more » FI, and CHF, for both HEU and LEU fuel, but that the high power fuel element produces similar margin in a few cases. The maximum fuel temperature similarly occurs in both the high heat flux and high power fuel assemblies for both HEU and LEU fuel. A sensitivity study was also performed to evaluate the variation in fuel temperature due to uncertainties in the thermal conductivity degradation associated with burnup.« less

Irradiation effects on thermal properties of LWR hydride fuel

NASA Astrophysics Data System (ADS)

Terrani, Kurt; Balooch, Mehdi; Carpenter, David; Kohse, Gordon; Keiser, Dennis; Meyer, Mitchell; Olander, Donald

2017-04-01

Three hydride mini-fuel rods were fabricated and irradiated at the MIT nuclear reactor with a maximum burnup of 0.31% FIMA or ∼5 MWd/kgU equivalent oxide fuel burnup. Fuel rods consisted of uranium-zirconium hydride (U (30 wt%)ZrH1.6) pellets clad inside a LWR Zircaloy-2 tubing. The gap between the fuel and the cladding was filled with lead-bismuth eutectic alloy to eliminate the gas gap and the large temperature drop across it. Each mini-fuel rod was instrumented with two thermocouples with tips that are axially located halfway through the fuel centerline and cladding surface. In-pile temperature measurements enabled calculation of thermal conductivity in this fuel as a function of temperature and burnup. In-pile thermal conductivity at the beginning of test agreed well with out-of-pile measurements on unirradiated fuel and decreased rapidly with burnup.

High Temperature Fuel Cladding Chemical Interactions Between TRIGA Fuels and 304 Stainless Steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perez, Emmanuel; Keiser, Jr., Dennis D.; Forsmann, Bryan

High-temperature fuel-cladding chemical interactions (FCCI) between TRIGA (Training, Research, Isotopes, General Atomics) fuel elements and the 304 stainless steel (304SS) are of interest to develop an understanding of the fuel behavior during transient reactor scenarios. TRIGA fuels are composed of uranium (U) particles dispersed in a zirconium-hydride (Zr-H) matrix. In reactor, the fuel is encased in 304-stainless-steel (304SS) or Incoloy 800 clad tubes. At high temperatures, the fuel can readily interact with the cladding, resulting in FCCI. A number of FCCI can take place in this system. Interactions can be expected between the cladding and the Zr-H matrix, and/or betweenmore » the cladding and the U-particles. Other interactions may be expected between the Zr-H matrix and the U-particles. Furthermore, the fuel contains erbium-oxide (Er-O) additions. Interactions can also be expected between the Er-O, the cladding, the Zr-H and the U-particles. The overall result is that very complex interactions may take place as a result of fuel and cladding exposures to high temperatures. This report discusses the characterization of the baseline fuel microstructure in the as-received state (prior to exposure to high temperature), characterization of the fuel after annealing at 950C for 24 hours and the results from diffusion couple experiments carries out at 1000C for 5 and 24 hours. Characterization was carried out via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) with sample preparation via focused ion beam in situ-liftout-technique.« less

The irradiation behavior of atomized U-Mo alloy fuels at high temperature

NASA Astrophysics Data System (ADS)

Park, Jong-Man; Kim, Ki-Hwan; Kim, Chang-Kyu; Meyer, M. K.; Hofman, G. L.; Strain, R. V.

2001-04-01

Post-irradiation examinations of atomized U-10Mo, U-6Mo, and U-6Mo-1.7Os dispersion fuels from the RERTR-3 experiment irradiated in the Advanced Test Reactor (ATR) were carried out in order to investigate the fuel behavior of high uranium loading (8 gU/cc) at a high temperature (higher than 200°C). It was observed after about 40 at% BU that the U-Mo alloy fuels at a high temperature showed similar irradiation bubble morphologies compared to those at a lower temperature found in the RERTR-1 irradiation result, but there was a thick reaction layer with the aluminum matrix which was found to be greatly affected by the irradiation temperature and to a lesser degree by the fuel composition. In addition, the chemical analysis for the irradiated U-Mo fuels using the Electron Probe Micro Analysis (EPMA) method were conducted to investigate the compositional changes during the formation of the reaction product.

The MSFR as a flexible CR reactor: the viewpoint of safety

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fiorina, C.; Cammi, A.; Franceschini, F.

2013-07-01

In this paper, the possibility has first been discussed of using the liquid-fuelled Molten Salt Fast Reactor (MSFR) as a flexible conversion ratio (CR) reactor without design modification. By tuning the reprocessing rate it is possible to determine the content of fission products in the core, which in turn can significantly affect the neutron economy without incurring in solubility problems. The MSFR can thus be operated as U-233 breeder (CR>1), iso-breeder (CR=1) and burner reactor (CR<1). In particular a 40 year doubling time can be achieved, as well as a considerable Transuranics and MA (minor actinide) burning rate equal tomore » about 150 kg{sub HN}/GWE-yr. The safety parameters of the MSFR have then been evaluated for different fuel cycle strategies. Th use and a softer spectrum combine to give a strong Doppler coefficient, one order of magnitude higher compared to traditional fast reactors (FRs). The fuel expansion coefficient is comparable to the Doppler coefficient and is only mildly affected by core compositions, thus assisting the fuel cycle flexibility of the MSFR. βeff and generation time are comparable to the case of traditional FRs, if a static fuel is assumed. A notable reduction of βeff is caused by salt circulation, but a low value of this parameter is a limited concern in the MSFR thanks to the lack of a burnup reactivity swing and of positive feedbacks. A simple approach has also been developed to evaluate the MSFR capabilities to withstand all typical double-fault accidents, for different fuel cycle options.« less

Feasibility of Renewable Energy Technology at the Afghanistan National Security University: A Site-Specific Study Focused on Potential Renewable Energy Technologies in Northwest Kabul, Afghanistan

DTIC Science & Technology

2011-04-26

70% H2, O2 Proton exchange membrane fuel cell ( PEMFC ) Proton exchange membrane Rm temp to 80 °C 40–60% H2, O2, Air Direct methanol fuel cell...Cell PEMFC Proton Exchange Membrane Fuel Cell PV Photovoltaic SHGC Solar Heat Gain Coefficient SIR savings to investment ratio SOFC Solid Oxide

Monolithic solid oxide fuel cell development

NASA Technical Reports Server (NTRS)

Myles, K. M.; Mcpheeters, C. C.

1989-01-01

The feasibility of the monolithic solid oxide fuel cell (MSOFC) concept has been proven, and the performance has been dramatically improved. The differences in thermal expansion coefficients and firing shrinkages among the fuel cell materials have been minimized, thus allowing successful fabrication of the MSOFC with few defects. The MSOFC shows excellent promise for development into a practical power source for many applications from stationary power, to automobile propulsion, to space pulsed power.

Analytical evaluation of effect of equivalence ratio inlet-air temperature and combustion pressure on performance of several possible ram-jet fuels

NASA Technical Reports Server (NTRS)

Tower, Leonard K; Gammon, Benson E

1953-01-01

The results of an analytical investigation of the theoretical air specific impulse performance and adiabatic combustion temperatures of several possible ram-jet fuels over a range of equivalence ratios, inlet-air temperatures, and combustion pressures, is presented herein. The fuels include octane-1, 50-percent-magnesium slurry, boron, pentaborane, diborane, hydrogen, carbon, and aluminum. Thermal effects from high combustion temperatures were found to effect considerably the combustion performance of all the fuels. An increase in combustion pressure was beneficial to air specific impulse at high combustion temperatures. The use of these theoretical data in engine operation and in the evaluation of experimental data is described.

Fuel retention under elevated wall temperature in KSTAR with a carbon wall

NASA Astrophysics Data System (ADS)

Cao, B.; Hong, S. H.

2018-03-01

The fuel retention during KSTAR discharges with elevated wall temperature (150 °C) has been studied by using the method of global particle balance. The results show that the elevated wall temperature could reduce the dynamic retention via implantation and absorption, especially for the short pulse shots with large injected fuel particles. There is no signature changing of long-term retention, which related to co-deposition, under elevated wall temperature. For soft-landing shots (normal shots), the exhausted fuel particles during discharges is larger with elevated wall temperature than without, but the exhausted particles after discharges within 90 s looks similar. The outgassing particles because of disruption could be exhausted within 15 s.

High-temperature sorbent method for removal of sulfur-containing gases from gaseous mixtures

DOEpatents

Young, J.E.; Jalan, V.M.

1982-07-07

A copper oxide-zinc oxide mixture is used as a sorbent for removing hydrogen sulfide and other sulfur containing gases at high temperatures from a gaseous fuel mixture. This high-temperature sorbent is especially useful for preparing fuel gases for high temperature fuel cells. The copper oxide is initially reduced in a preconditioning step to elemental copper and is present in a highly dispersed state throughout the zinc oxide which serves as a support as well as adding to the sulfur sorbtion capacity. The spent sorbent is regenerated by high-temperature treatment with an air fuel, air steam mixture followed by hydrogen reduction to remove and recover the sulfur.

High-temperature sorbent method for removal of sulfur containing gases from gaseous mixtures

DOEpatents

Young, J.E.; Jalan, V.M.

1984-06-19

A copper oxide-zinc oxide mixture is used as a sorbent for removing hydrogen sulfide and other sulfur containing gases at high temperatures from a gaseous fuel mixture. This high-temperature sorbent is especially useful for preparing fuel gases for high temperature fuel cells. The copper oxide is initially reduced in a preconditioning step to elemental copper and is present in a highly dispersed state throughout the zinc oxide which serves as a support as well as adding to the sulfur sorption capacity. The spent sorbent is regenerated by high-temperature treatment with an air fuel, air steam mixture followed by hydrogen reduction to remove and recover the sulfur.

High-temperature sorbent method for removal of sulfur containing gases from gaseous mixtures

DOEpatents

Young, John E.; Jalan, Vinod M.

1984-01-01

A copper oxide-zinc oxide mixture is used as a sorbent for removing hydrogen sulfide and other sulfur containing gases at high temperatures from a gaseous fuel mixture. This high-temperature sorbent is especially useful for preparing fuel gases for high temperature fuel cells. The copper oxide is initially reduced in a preconditioning step to elemental copper and is present in a highly dispersed state throughout the zinc oxide which serves as a support as well as adding to the sulfur sorption capacity. The spent sorbent is regenerated by high-temperature treatment with an air fuel, air steam mixture followed by hydrogen reduction to remove and recover the sulfur.

Studying the characteristics of a 5 kW power installation on solid-oxide fuel cells with steam reforming of natural gas

NASA Astrophysics Data System (ADS)

Munts, V. A.; Volkova, Yu. V.; Plotnikov, N. S.; Dubinin, A. M.; Tuponogov, V. G.; Chernishev, V. A.

2015-11-01

The results from tests of a 5 kW power plant on solid-oxide fuel cells (SOFCs), in which natural gas is used as fuel, are presented. The installation's process circuit, the test procedure, and the analysis of the obtained results are described. The characteristics of the power plant developed by the Ural Industrial Company are investigated in four steady-state modes of its operation: with the SOFC nominal power capacity utilized by 40% (2 kW), 60% (3 kW), 90% (4.5 kW) and 110% (5.4 kW) (the peaking mode). The electrical and thermodynamic efficiencies are calculated for all operating modes, and the most efficient mode, in which the electrical efficiency reached almost 70%, is determined. The air excess coefficient and heat loss with flue gases q 2 are determined, and it is revealed that the heat loss q 5 decreases from 40 to 25% with increasing the load. Thermal balances are drawn up for the following components of the system the reformer, the SOFC battery, the catalytic burner for afterburning anode gases, the heat exchanger for heating the cathode air and the mixture of natural gas and steam, and the actual fuel utilization rates in the electrochemical generator are calculated. An equation for the resulting natural gas steam reforming reaction was obtained based on the results from calculating the equilibrium composition of reforming products for the achieved temperatures at the reformer outlet t 3.

Modeling and Predicting the Electrical Conductivity of Composite Cathode for Solid Oxide Fuel Cell by Using Support Vector Regression

NASA Astrophysics Data System (ADS)

Tang, J. L.; Cai, C. Z.; Xiao, T. T.; Huang, S. J.

2012-07-01

The electrical conductivity of solid oxide fuel cell (SOFC) cathode is one of the most important indices affecting the efficiency of SOFC. In order to improve the performance of fuel cell system, it is advantageous to have accurate model with which one can predict the electrical conductivity. In this paper, a model utilizing support vector regression (SVR) approach combined with particle swarm optimization (PSO) algorithm for its parameter optimization was established to modeling and predicting the electrical conductivity of Ba0.5Sr0.5Co0.8Fe0.2 O3-δ-xSm0.5Sr0.5CoO3-δ (BSCF-xSSC) composite cathode under two influence factors, including operating temperature (T) and SSC content (x) in BSCF-xSSC composite cathode. The leave-one-out cross validation (LOOCV) test result by SVR strongly supports that the generalization ability of SVR model is high enough. The absolute percentage error (APE) of 27 samples does not exceed 0.05%. The mean absolute percentage error (MAPE) of all 30 samples is only 0.09% and the correlation coefficient (R2) as high as 0.999. This investigation suggests that the hybrid PSO-SVR approach may be not only a promising and practical methodology to simulate the properties of fuel cell system, but also a powerful tool to be used for optimal designing or controlling the operating process of a SOFC system.

Effect of aluminizing of Cr-containing ferritic alloys on the seal strength of a novel high-temperature solid oxide fuel cell sealing glass

NASA Astrophysics Data System (ADS)

Chou, Yeong-Shyung; Stevenson, Jeffry W.; Singh, Prabhakar

A novel high-temperature alkaline earth silicate sealing glass was developed for solid oxide fuel cell (SOFC) applications. The glass was used to join two metallic coupons of Cr-containing ferritic stainless steel for seal strength evaluation. In previous work, SrCrO 4 was found to form along the glass/steel interface, which led to severe strength degradation. In the present study, aluminization of the steel surface was investigated as a remedy to minimize or prevent the strontium chromate formation. Three different processes for aluminization were evaluated with Crofer22APU stainless steel: pack cementation, vapor-phase deposition, and aerosol spraying. It was found that pack cementation resulted in a rough surface with occasional cracks in the Al-diffused region. Vapor-phase deposition yielded a smoother surface, but the resulting high Al content increased the coefficient of thermal expansion (CTE), resulting in the failure of joined coupons. Aerosol spraying of an Al-containing salt resulted in the formation of a thin aluminum oxide layer without any surface damage. The room temperature seal strength was evaluated in the as-fired state and in environmentally aged conditions. In contrast to earlier results with uncoated Crofer22APU, the aluminized samples showed no strength degradation even for samples aged in air. Interfacial and chemical compatibility was also investigated. The results showed aluminization to be a viable candidate approach to minimize undesirable chromate formation between alkaline earth silicate sealing glass and Cr-containing interconnect alloys for SOFC applications.

A novel family of Nb-doped Bi0.5Sr0.5FeO3-δ perovskite as cathode material for intermediate-temperature solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Gao, Lei; Li, Qiang; Sun, Liping; Zhang, Xianfa; Huo, Lihua; Zhao, Hui; Grenier, Jean-Claude

2017-12-01

Cobalt-free provskite oxides Bi0.5Sr0.5Fe1-xNbxO3-δ (BSFNx, x = 0.05, 0.10 and 0.15) were prepared and evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). In particular, the effects of Nb substitution on phase evolution, thermal expansion behavior and electrochemical performance were systematically investigated. The average thermal expansion coefficient (TEC) of BSFNx decreases from 13.3 × 10-6 K-1 at x = 0.05 to 12.6 × 10-6 K-1 at x = 0.15 within a temperature range of 50-800 °C. Among the BSFNx materials, Bi0.5Sr0.5Fe0.9Nb0.1O3-δ (BSFN0.10) oxide shows the best electrochemical performance. The polarization resistances (Rp) of BSFN0.10 cathode on CGO electrolyte are 0.038, 0.075 and 0.156 Ω cm2 at 700, 650 and 600 °C, respectively. Meanwhile the maximum power densities of the anode-supported single cells are 1.28, 1.54 and 1.34 W cm-2 at 700 °C for BSFNx cathodes with x = 0.05, 0.10, and 0.15, respectively. Furthermore, the relationship study of oxygen partial pressure dependence on Rp indicates that the oxygen reduction reaction (ORR) rate-limiting step is the oxygen adsorption-dissociation on the electrode surface. The desirable electrochemical performance demonstrates that BSFNx oxides are potential cathode materials for IT-SOFCs.

Transport modeling of convection dominated helicon discharges in Proto-MPEX with the B2.5-Eirene code

NASA Astrophysics Data System (ADS)

Owen, L. W.; Rapp, J.; Canik, J.; Lore, J. D.

2017-11-01

Data-constrained interpretative analyses of plasma transport in convection dominated helicon discharges in the Proto-MPEX linear device, and predictive calculations with additional Electron Cyclotron Heating/Electron Bernstein Wave (ECH/EBW) heating, are reported. The B2.5-Eirene code, in which the multi-fluid plasma code B2.5 is coupled to the kinetic Monte Carlo neutrals code Eirene, is used to fit double Langmuir probe measurements and fast camera data in front of a stainless-steel target. The absorbed helicon and ECH power (11 kW) and spatially constant anomalous transport coefficients that are deduced from fitting of the probe and optical data are additionally used for predictive simulations of complete axial distributions of the densities, temperatures, plasma flow velocities, particle and energy fluxes, and possible effects of alternate fueling and pumping scenarios. The somewhat hollow electron density and temperature radial profiles from the probe data suggest that Trivelpiece-Gould wave absorption is the dominant helicon electron heating source in the discharges analyzed here. There is no external ion heating, but the corresponding calculated ion temperature radial profile is not hollow. Rather it reflects ion heating by the electron-ion equilibration terms in the energy balance equations and ion radial transport resulting from the hollow density profile. With the absorbed power and the transport model deduced from fitting the sheath limited discharge data, calculated conduction limited higher recycling conditions were produced by reducing the pumping and increasing the gas fueling rate, resulting in an approximate doubling of the target ion flux and reduction of the target heat flux.

Catalytic combustion of residual fuels

NASA Technical Reports Server (NTRS)

Bulzan, D. L.; Tacina, R. R.

1981-01-01

A noble metal catalytic reactor was tested using two grades of petroleum derived residual fuels at specified inlet air temperatures, pressures, and reference velocities. Combustion efficiencies greater than 99.5 percent were obtained. Steady state operation of the catalytic reactor required inlet air temperatures of at least 800 K. At lower inlet air temperatures, upstream burning in the premixing zone occurred which was probably caused by fuel deposition and accumulation on the premixing zone walls. Increasing the inlet air temperature prevented this occurrence. Both residual fuels contained about 0.5 percent nitrogen by weight. NO sub x emissions ranged from 50 to 110 ppm by volume at 15 percent excess O2. Conversion of fuel-bound nitrogen to NO sub x ranged from 25 to 50 percent.

Effects of chemical equilibrium on turbine engine performance for various fuels and combustor temperatures

NASA Technical Reports Server (NTRS)

Tran, Donald H.; Snyder, Christopher A.

1992-01-01

A study was performed to quantify the differences in turbine engine performance with and without the chemical dissociation effects for various fuel types over a range of combustor temperatures. Both turbojet and turbofan engines were studied with hydrocarbon fuels and cryogenic, nonhydrocarbon fuels. Results of the study indicate that accuracy of engine performance decreases when nonhydrocarbon fuels are used, especially at high temperatures where chemical dissociation becomes more significant. For instance, the deviation in net thrust for liquid hydrogen fuel can become as high as 20 percent at 4160 R. This study reveals that computer central processing unit (CPU) time increases significantly when dissociation effects are included in the cycle analysis.

Direct hydrocarbon fuel cells

DOEpatents

Barnett, Scott A.; Lai, Tammy; Liu, Jiang

2010-05-04

The direct electrochemical oxidation of hydrocarbons in solid oxide fuel cells, to generate greater power densities at lower temperatures without carbon deposition. The performance obtained is comparable to that of fuel cells used for hydrogen, and is achieved by using novel anode composites at low operating temperatures. Such solid oxide fuel cells, regardless of fuel source or operation, can be configured advantageously using the structural geometries of this invention.

The use of experimental data in an MTR-type nuclear reactor safety analysis

NASA Astrophysics Data System (ADS)

Day, Simon E.

Reactivity initiated accidents (RIAs) are a category of events required for research reactor safety analysis. A subset of this is unprotected RIAs in which mechanical systems or human intervention are not credited in the response of the system. Light-water cooled and moderated MTR-type ( i.e., aluminum-clad uranium plate fuel) reactors are self-limiting up to some reactivity insertion limit beyond which fuel damage occurs. This characteristic was studied in the Borax and Spert reactor tests of the 1950s and 1960s in the USA. This thesis considers the use of this experimental data in generic MTR-type reactor safety analysis. The approach presented herein is based on fundamental phenomenological understanding and uses correlations in the reactor test data with suitable account taken for differences in important system parameters. Specifically, a semi-empirical approach is used to quantify the relationship between the power, energy and temperature rise response of the system as well as parametric dependencies on void coefficient and the degree of subcooling. Secondary effects including the dependence on coolant flow are also examined. A rigorous curve fitting approach and error assessment is used to quantify the trends in the experimental data. In addition to the initial power burst stage of an unprotected transient, the longer term stability of the system is considered with a stylized treatment of characteristic power/temperature oscillations (chugging). A bridge from the HEU-based experimental data to the LEU fuel cycle is assessed and outlined based on existing simulation results presented in the literature. A cell-model based parametric study is included. The results are used to construct a practical safety analysis methodology for determining reactivity insertion safety limits for a light-water moderated and cooled MTR-type core.

Elucidating reactivity regimes in cyclopentane oxidation: Jet stirred reactor experiments, computational chemistry, and kinetic modeling

DOE PAGES

Al Rashidi, Mariam J.; Thion, Sebastien; Togbe, Casimir; ...

2016-06-22

This study is concerned with the identification and quantification of species generated during the combustion of cyclopentane in a jet stirred reactor (JSR). Experiments were carried out for temperatures between 740 and 1250 K, equivalence ratios from 0.5 to 3.0, and at an operating pressure of 10 atm. The fuel concentration was kept at 0.1% and the residence time of the fuel/O 2/N 2 mixture was maintained at 0.7 s. The reactant, product, and intermediate species concentration profiles were measured using gas chromatography and Fourier transform infrared spectroscopy. The concentration profiles of cyclopentane indicate inhibition of reactivity between 850-1000 Kmore » for φ=2.0 and φ=3.0. This behavior is interesting, as it has not been observed previously for other fuel molecules, cyclic or non-cyclic. A kinetic model including both low- and high-temperature reaction pathways was developed and used to simulate the JSR experiments. The pressure-dependent rate coefficients of all relevant reactions lying on the PES of cyclopentyl + O 2, as well as the C-C and C-H scission reactions of the cyclopentyl radical were calculated at the UCCSD(T)-F12b/cc-pVTZ-F12//M06-2X/6-311++G(d,p) level of theory. The simulations reproduced the unique reactivity trend of cyclopentane and the measured concentration profiles of intermediate and product species. Furthermore, sensitivity and reaction path analyses indicate that this reactivity trend may be attributed to differences in the reactivity of allyl radical at different conditions, and it is highly sensitive to the C-C/C-H scission branching ratio of the cyclopentyl radical decomposition.« less

An algorithm for temperature correcting substrate moisture measurements: aligning substrate moisture responses with environmental drivers in polytunnel-grown strawberry plants

NASA Astrophysics Data System (ADS)

Goodchild, Martin; Janes, Stuart; Jenkins, Malcolm; Nicholl, Chris; Kühn, Karl

2015-04-01

The aim of this work is to assess the use of temperature corrected substrate moisture data to improve the relationship between environmental drivers and the measurement of substrate moisture content in high porosity soil-free growing environments such as coir. Substrate moisture sensor data collected from strawberry plants grown in coir bags installed in a table-top system under a polytunnel illustrates the impact of temperature on capacitance-based moisture measurements. Substrate moisture measurements made in our coir arrangement possess the negative temperature coefficient of the permittivity of water where diurnal changes in moisture content oppose those of substrate temperature. The diurnal substrate temperature variation was seen to range from 7° C to 25° C resulting in a clearly observable temperature effect in substrate moisture content measurements during the 23 day test period. In the laboratory we measured the ML3 soil moisture sensor (ThetaProbe) response to temperature in Air, dry glass beads and water saturated glass beads and used a three-phase alpha (α) mixing model, also known as the Complex Refractive Index Model (CRIM), to derive the permittivity temperature coefficients for glass and water. We derived the α value and estimated the temperature coefficient for water - for sensors operating at 100MHz. Both results are good agreement with published data. By applying the CRIM equation with the temperature coefficients of glass and water the moisture temperature coefficient of saturated glass beads has been reduced by more than an order of magnitude to a moisture temperature coefficient of

Micro-mechanical evaluation of SiC-SiC composite interphase properties and debond mechanisms

DOE PAGES

Kabel, Joey; Yang, Y.; Balooch, Mehdi; ...

2017-07-31

SiC-SiC composites exhibit exceptional high temperature strength and oxidation properties making them an advantageous choice for accident tolerant nuclear fuel cladding. In the present work, small scale mechanical testing along with AFM and TEM analysis were employed to evaluate PyC interphase properties that play a key role in the overall mechanical behavior of the composite. The Mohr-Coulomb formulation allowed for the extraction of the internal friction coefficient and debonding shear strength as a function of the PyC layer thickness, an additional parameter. Here, these results have led to re-evaluation of the Mohr-Coulomb failure criterion and adjustment via a new phenomenologicalmore » equation.« less

Electrolyte matrix for molten carbonate fuel cells

DOEpatents

Huang, C.M.; Yuh, C.Y.

1999-02-09

A matrix is described for a carbonate electrolyte including a support material and an additive constituent having a relatively low melting temperature and a relatively high coefficient of thermal expansion. The additive constituent is from 3 to 45 weight percent of the matrix and is formed from raw particles whose diameter is in a range of 0.1 {micro}m to 20 {micro}m and whose aspect ratio is in a range of 1 to 50. High energy intensive milling is used to mix the support material and additive constituent during matrix formation. Also disclosed is the use of a further additive constituent comprising an alkaline earth containing material. The further additive is mixed with the support material using high energy intensive milling. 5 figs.

Electrolyte matrix for molten carbonate fuel cells

DOEpatents

Huang, Chao M.; Yuh, Chao-Yi

1999-01-01

A matrix for a carbonate electrolyte including a support material and an additive constituent having a relatively low melting temperature and a relatively high coefficient of thermal expansion. The additive constituent is from 3 to 45 weight percent of the matrix and is formed from raw particles whose diameter is in a range of 0.1 .mu.m to 20 .mu.m and whose aspect ratio is in a range of 1 to 50. High energy intensive milling is used to mix the support material and additive constituent during matrix formation. Also disclosed is the use of a further additive constituent comprising an alkaline earth containing material. The further additive is mixed with the support material using high energy intensive milling.

Meso and Micro Scale Propulsion Concepts for Small Spacecraft

DTIC Science & Technology

2006-07-28

flame length , QF is the volumetric flow rate of the fuel, D is the binary diffusion coefficient of the fuel in the oxidizer, and YFsoi, is the...R, can yield the same flame length . Most laminar diffusion flames are buoyancy-controlled since a small exit velocity is generally required to

K1.33Mn8O16 as an electrocatalyst and a cathode

NASA Astrophysics Data System (ADS)

Jalili, Seifollah; Moharramzadeh Goliaei, Elham; Schofield, Jeremy

2017-02-01

Density functional theory (DFT) calculations are carried out to investigate the electronic, magnetic and thermoelectric properties of bulk and nanosheet K1.33Mn8O16 materials. The catalytic activity and cathodic performance of bulk and nanosheet structures are examined using the Tran-Blaha modified Becke-Johnson (TB-mBJ) exchange potential. Electronic structure calculations reveal an anti-ferromagnetic ground state, with a TB-mMBJ band gap in bulk K1.33Mn8O16 that is in agreement with experimental results. Density of state plots indicate a partial reduction of Mn4+ ions to Mn3+, without any obvious sign of Jahn-Teller distortion. Moreover, use of the O p-band center as a descriptor of catalytic activity suggests that the nanosheet has enhanced catalytic activity compared to the bulk structure. Thermoelectric parameters such as the Seebeck coefficient, electrical conductivity, and thermal conductivity are also calculated, and it is found that the Seebeck coefficients decrease with increasing temperature. High Seebeck coefficients for both spin-up and spin-down states are found in the nanosheet relative to their value in the bulk K1.33Mn8O16 structure, whereas the electrical and thermal conductivity are reduced relative to the bulk. In addition, figures of merit values are calculated as a function of the chemical potential and it is found that the nanosheet has a figure of merit of 1 at room temperature, compared to 0.5 for the bulk material. All results suggest that K1.33Mn8O16 nanosheets can be used both as a material in waste heat recovery and as an electrocatalyst in fuel cells and batteries.

Method for control of NOx emission from combustors using fuel dilution

DOEpatents

Schefer, Robert W [Alamo, CA; Keller, Jay O [Oakland, CA

2007-01-16

A method of controlling NOx emission from combustors. The method involves the controlled addition of a diluent such as nitrogen or water vapor, to a base fuel to reduce the flame temperature, thereby reducing NOx production. At the same time, a gas capable of enhancing flame stability and improving low temperature combustion characteristics, such as hydrogen, is added to the fuel mixture. The base fuel can be natural gas for use in industrial and power generation gas turbines and other burners. However, the method described herein is equally applicable to other common fuels such as coal gas, biomass-derived fuels and other common hydrocarbon fuels. The unique combustion characteristics associated with the use of hydrogen, particularly faster flame speed, higher reaction rates, and increased resistance to fluid-mechanical strain, alter the burner combustion characteristics sufficiently to allow operation at the desired lower temperature conditions resulting from diluent addition, without the onset of unstable combustion that can arise at lower combustor operating temperatures.

Fuel-rich, catalytic reaction experimental results

NASA Technical Reports Server (NTRS)

Rollbuhler, R. James

1991-01-01

Future aeropropulsion gas turbine combustion requirements call for operating at very high inlet temperatures, pressures, and large temperature rises. At the same time, the combustion process is to have minimum pollution effects on the environment. Aircraft gas turbine engines utilize liquid hydrocarbon fuels which are difficult to uniformly atomize and mix with combustion air. An approach for minimizing fuel related problems is to transform the liquid fuel into gaseous form prior to the completion of the combustion process. Experimentally obtained results are presented for vaporizing and partially oxidizing a liquid hydrocarbon fuel into burnable gaseous components. The presented experimental data show that 1200 to 1300 K reaction product gas, rich in hydrogen, carbon monoxide, and light-end hydrocarbons, is formed when flowing 0.3 to 0.6 fuel to air mixes through a catalyst reactor. The reaction temperatures are kept low enough that nitrogen oxides and carbon particles (soot) do not form. Results are reported for tests using different catalyst types and configurations, mass flowrates, input temperatures, and fuel to air ratios.

Investigation of the Performance of D 2O-Cooled High-Conversion Reactors for Fuel Cycle Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiruta, Hikaru; Youinou, Gilles

2013-09-01

This report presents FY13 activities for the analysis of D 2O cooled tight-pitch High-Conversion PWRs (HCPWRs) with U-Pu and Th-U fueled cores aiming at break-even or near breeder conditions while retaining the negative void reactivity. The analyses are carried out from several aspects which could not be covered in FY12 activities. SCALE 6.1 code system is utilized, and a series of simple 3D fuel pin-cell models are developed in order to perform Monte Carlo based criticality and burnup calculations. The performance of U-Pu fueled cores with axial and internal blankets is analyzed in terms of their impact on the relativemore » fissile Pu mass balance, initial Pu enrichment, and void coefficient. In FY12, Pu conversion performances of D 2O-cooled HCPWRs fueled with MOX were evaluated with small sized axial/internal DU blankets (approximately 4cm of axial length) in order to ensure the negative void reactivity, which evidently limits the conversion performance of HCPWRs. In this fiscal year report, the axial sizes of DU blankets are extended up to 30 cm in order to evaluate the amount of DU necessary to reach break-even and/or breeding conditions. Several attempts are made in order to attain the milestone of the HCPWR designs (i.e., break-even condition and negative void reactivity) by modeling of HCPWRs under different conditions such as boiling of D 2O coolant, MOX with different 235U enrichment, and different target burnups. A similar set of analyses are performed for Th-U fueled cores. Several promising characteristics of 233U over other fissile like 239Pu and 235U, most notably its higher fission neutrons per absorption in thermal and epithermal ranges combined with lower ___ in the fast range than 239Pu allows Th-U cores to be taller than MOX ones. Such an advantage results in 4% higher relative fissile mass balance than that of U-Pu fueled cores while retaining the negative void reactivity until the target burnup of 51 GWd/t. Several other distinctions between U-Pu and Th-U fueled cores are identified by evaluating the sensitivity coefficients of keff, mass balance, and void coefficient. The effect of advanced iron alloy cladding (i.e., FeCrAl) on the performance of Pu conversion in MOX fueled cores is studied instead of using standard stainless-steel cladding. Variations in clad thickness and coolant-to-fuel volume ratio are also exercised. The use of FeCrAl instead of SS as a cladding alloy reduces the required Pu enrichment and improves the Pu conversion rate primarily due to the absence of nickel in the cladding alloy that results in the reduction of the neutron absorption. Also the difference in void coefficients between SS and FeCrAl alloys is nearly 500 pcm over the entire burnup range. The report also shows sensitivity and uncertainty analyses in order to characterize D 2O cooled HCPWRs from different aspects. The uncertainties of integral parameters (keff and void coefficient) for selected reactor cores are evaluated at different burnup points in order to find similarities and trends respect to D 2O-HCPWR.« less

Thermodynamics and Cation Diffusion in the Oxygen Ion Conductor Lsgm

NASA Astrophysics Data System (ADS)

Martin, M.; Schulz, O.

Perovskite type oxides based on LaGaO3 are of large technical interest because of their high oxygen-ion conductivity. Lanthanum gallate doped with Sr on A- and Mg on B-sites, La1-xSrxGa1-yMgyO3-(x+y)/2 (LSGM), reaches higher oxygen-ion conductivities than yttria-doped zirconia (YSZ). Thus LSGM represents a promising alternative for YSZ as electrolyte in solid oxide fuel cells (SOFC). Cells using thin LSGM-layers as electrolyte are expected to operate at intermediate temperatures around 700°C for more than 30000 hours without severe degradation. A potential long term degradation effect of LSGM is kinetic demixing of the electrolyte, caused by different cation diffusion coefficients. In this paper we report on experimental studies concerning the phase diagram of LSGM and the diffusion of cations. Cation self-diffusion of 139La, 84Sr and 25Mg and cation impurity diffusion of 144Nd, 89Y and 56Fe in polycrystalline LSGM samples was investigated by secondary ion mass spectrometry (SIMS) for temperatures between 900°C and 1400°C. It was found that diffusion occurs by means of bulk and grain boundaries. The bulk diffusion coefficients are similar for all cations with activation energies which are strongly dependent on temperature. At high temperatures, the activation energies are about 5 eV, while at low temperatures values of about 2 eV are found. These results are explained by a frozen in defect structure at low temperatures. This means that the observed activation energy at low temperatures represents only the migration energy of the different cations while the observed activation energy at high temperatures is the sum of the defect formation energy and the migration energy. The migration energies for all cations are nearly identical, although 139La, 84Sr and 144Nd are occupying A-sites while 25Mg and 56Fe are occupying B-sites in the perovskite-structure. To explain these experimental findings we propose a defect cluster containing cation vacancies in both the A- and the B-sublattice and anion vacancies as well.

40 CFR 86.1427 - Certification Short Test procedure; overview.

Code of Federal Regulations, 2010 CFR

2010-07-01

... loaded modes. Specific conditions defined by this test procedure include fuel characteristics, ambient... CO fuel, a moderate temperature test with Cold CO fuel, and a warm temperature test with FTP Otto-cycle test fuel, as described in table O-96-1 of § 86.1430. The manufacturer must complete testing for...

40 CFR 86.1427 - Certification Short Test procedure; overview.

Code of Federal Regulations, 2013 CFR

2013-07-01

... loaded modes. Specific conditions defined by this test procedure include fuel characteristics, ambient... CO fuel, a moderate temperature test with Cold CO fuel, and a warm temperature test with FTP Otto-cycle test fuel, as described in table O-96-1 of § 86.1430. The manufacturer must complete testing for...

40 CFR 86.1427 - Certification Short Test procedure; overview.

Code of Federal Regulations, 2011 CFR

2011-07-01

... loaded modes. Specific conditions defined by this test procedure include fuel characteristics, ambient... CO fuel, a moderate temperature test with Cold CO fuel, and a warm temperature test with FTP Otto-cycle test fuel, as described in table O-96-1 of § 86.1430. The manufacturer must complete testing for...

40 CFR 86.1427 - Certification Short Test procedure; overview.

Code of Federal Regulations, 2012 CFR

2012-07-01

... loaded modes. Specific conditions defined by this test procedure include fuel characteristics, ambient... CO fuel, a moderate temperature test with Cold CO fuel, and a warm temperature test with FTP Otto-cycle test fuel, as described in table O-96-1 of § 86.1430. The manufacturer must complete testing for...

A full set of langatate high-temperature acoustic wave constants: elastic, piezoelectric, dielectric constants up to 900°C.

PubMed

Davulis, Peter M; da Cunha, Mauricio Pereira

2013-04-01

A full set of langatate (LGT) elastic, dielectric, and piezoelectric constants with their respective temperature coefficients up to 900°C is presented, and the relevance of the dielectric and piezoelectric constants and temperature coefficients are discussed with respect to predicted and measured high-temperature SAW propagation properties. The set of constants allows for high-temperature acoustic wave (AW) propagation studies and device design. The dielectric constants and polarization and conductive losses were extracted by impedance spectroscopy of parallel-plate capacitors. The measured dielectric constants at high temperatures were combined with previously measured LGT expansion coefficients and used to determine the elastic and piezoelectric constants using resonant ultrasound spectroscopy (RUS) measurements at temperatures up to 900°C. The extracted LGT piezoelectric constants and temperature coefficients show that e11 and e14 change by up to 62% and 77%, respectively, for the entire 25°C to 900°C range when compared with room-temperature values. The LGT high-temperature constants and temperature coefficients were verified by comparing measured and predicted phase velocities (vp) and temperature coefficients of delay (TCD) of SAW delay lines fabricated along 6 orientations in the LGT plane (90°, 23°, Ψ) up to 900°C. For the 6 tested orientations, the predicted SAW vp agree within 0.2% of the measured vp on average and the calculated TCD is within 9.6 ppm/°C of the measured value on average over the temperature range of 25°C to 900°C. By including the temperature dependence of both dielectric and piezoelectric constants, the average discrepancies between predicted and measured SAW properties were reduced, on average: 77% for vp, 13% for TCD, and 63% for the turn-over temperatures analyzed.

Performance and emission characteristics of swirl-can combustors to near-stoichiometric fuel-air ratio

NASA Technical Reports Server (NTRS)

Diehl, L. A.; Trout, A. M.

1976-01-01

Emissions and performance characteristics were determined for two full annular swirl-can combustors operated to near stoichiometric fuel-air ratio. Test condition variations were as follows: combustor inlet-air temperatures, 589, 756, 839, and 894 K; reference velocities, 24 to 37 meters per second; inlet pressure, 62 newtons per square centimeter; and fuel-air ratios, 0.015 to 0.065. The combustor average exit temperature and combustor efficiency were calculated from the combustor exhaust gas composition. For fuel-air ratios greater than 0.04, the combustion efficiency decreased with increasing fuel-air ratios in a near-linear manner. Increasing the combustor inlet air temperature tended to offset this decrease. Maximum oxides of nitrogen emission indices occurred at intermediate fuel-air ratios and were dependent on combustor design. Carbon monoxide levels were extremely high and were the primary cause of poor combustion efficiency at the higher fuel-air ratios. Unburned hydrocarbons were low for all test conditions. For high fuel-air ratios SAE smoke numbers greater than 25 were produced, except at the highest inlet-air temperatures.

Nuclear fuel elements and method of making same

DOEpatents

Schweitzer, Donald G.

1992-01-01

A nuclear fuel element for a high temperature gas nuclear reactor that has an average operating temperature in excess of 2000.degree. C., and a method of making such a fuel element. The fuel element is characterized by having fissionable fuel material localized and stabilized within pores of a carbon or graphite member by melting the fissionable material to cause it to chemically react with the carbon walls of the pores. The fissionable fuel material is further stabilized and localized within the pores of the graphite member by providing one or more coatings of pyrolytic carbon or diamond surrounding the porous graphite member so that each layer defines a successive barrier against migration of the fissionable fuel from the pores, and so that the outermost layer of pyrolytic carbon or diamond forms a barrier between the fissionable material and the moderating gases used in an associated high temperature gas reactor. The method of the invention provides for making such new elements either as generally spherically elements, or as flexible filaments, or as other relatively small-sized fuel elements that are particularly suited for use in high temperature gas reactors.

Long term deposit formation in aviation turbine fuel at elevated temperature

NASA Technical Reports Server (NTRS)

Giovanetti, A. J.; Szetela, E. J.

1986-01-01

An experimental characterization is conducted for the relationships between deposit mass, operating time, and temperature, in coking associated with aviation fuels under conditions simulating those typical of turbine engine fuel systems. Jet A and Suntech A fuels were tested in stainless steel tubing heated to 420-750 K, over test durations of between 3 and 730 hr and at fuel velocities of 0.07-1.3 m/sec. Deposit rates are noted to be a strong function of tube temperature; for a given set of test conditions, deposition rates for Suntech A exceed those of Jet A by a factor of 10. Deposition rates increased markedly with test duration for both fuels. The heated tube data obtained are used to develop a global chemical kinetic model for fuel oxidation and carbon deposition.

Fabrication and testing of an enhanced ignition system to reduce cold-start emissions in an ethanol (E85) light-duty truck engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gardiner, D; Mallory, R; Todesco, M

This report describes an experimental investigation of the potential for an enhanced ignition system to lower the cold-start emissions of a light-duty vehicle engine using fuel ethanol (commonly referred to as E85). Plasma jet ignition and conventional inductive ignition were compared for a General Motors 4-cylinder, alcohol-compatible engine. Emission and combustion stability measurements were made over a range of air/fuel ratios and spark timing settings using a steady-state, cold-idle experimental technique in which the engine coolant was maintained at 25 C to simulate cold-running conditions. These tests were aimed at identifying the degree to which calibration strategies such as mixturemore » enleanment and retarded spark timing could lower engine-out hydrocarbon emissions and raise exhaust temperatures, as well as determining how such calibration changes would affect the combustion stability of the engine (as quantified by the coefficient of variation, or COV, of indicated mean effective pressure calculated from successive cylinder pressure measurements). 44 refs., 39 figs.« less

Reactivity effects in VVER-1000 of the third unit of the kalinin nuclear power plant at physical start-up. Computations in ShIPR intellectual code system with library of two-group cross sections generated by UNK code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zizin, M. N.; Zimin, V. G.; Zizina, S. N., E-mail: zizin@adis.vver.kiae.ru

2010-12-15

The ShIPR intellectual code system for mathematical simulation of nuclear reactors includes a set of computing modules implementing the preparation of macro cross sections on the basis of the two-group library of neutron-physics cross sections obtained for the SKETCH-N nodal code. This library is created by using the UNK code for 3D diffusion computation of first VVER-1000 fuel loadings. Computation of neutron fields in the ShIPR system is performed using the DP3 code in the two-group diffusion approximation in 3D triangular geometry. The efficiency of all groups of control rods for the first fuel loading of the third unit ofmore » the Kalinin Nuclear Power Plant is computed. The temperature, barometric, and density effects of reactivity as well as the reactivity coefficient due to the concentration of boric acid in the reactor were computed additionally. Results of computations are compared with the experiment.« less

Reactivity effects in VVER-1000 of the third unit of the kalinin nuclear power plant at physical start-up. Computations in ShIPR intellectual code system with library of two-group cross sections generated by UNK code

NASA Astrophysics Data System (ADS)

Zizin, M. N.; Zimin, V. G.; Zizina, S. N.; Kryakvin, L. V.; Pitilimov, V. A.; Tereshonok, V. A.

2010-12-01

The ShIPR intellectual code system for mathematical simulation of nuclear reactors includes a set of computing modules implementing the preparation of macro cross sections on the basis of the two-group library of neutron-physics cross sections obtained for the SKETCH-N nodal code. This library is created by using the UNK code for 3D diffusion computation of first VVER-1000 fuel loadings. Computation of neutron fields in the ShIPR system is performed using the DP3 code in the two-group diffusion approximation in 3D triangular geometry. The efficiency of all groups of control rods for the first fuel loading of the third unit of the Kalinin Nuclear Power Plant is computed. The temperature, barometric, and density effects of reactivity as well as the reactivity coefficient due to the concentration of boric acid in the reactor were computed additionally. Results of computations are compared with the experiment.

Membranes produced by plasma enhanced chemical vapor deposition technique for low temperature fuel cell applications

NASA Astrophysics Data System (ADS)

Ennajdaoui, Aboubakr; Roualdes, Stéphanie; Brault, Pascal; Durand, Jean

A plasma polymerization process using a continuous glow discharge has been implemented for preparing proton conducting membranes from trifluoromethane sulfonic acid and styrene. The chemical and physical structure of plasma membranes has been investigated using FTIR and SEM. The films are homogeneous with a good adhesion on commercial gas diffusion layer (E-Tek ®). Their deposition rate can be increased with increasing flow rate and input power. The thermogravimetric analysis under air of plasma polymers has showed a thermal stability up to 140 °C. Compared to the pulsed glow discharge studied in a previous paper, the continuous glow discharge has enabled to enhance the proton conductivity of membranes by a factor 3 (up to 1.7 mS cm -1). Moreover, the low methanol permeability (methanol diffusion coefficient down to 5 × 10 -13 m 2 s -1) of membranes has been confirmed by this study. In an industrial context, a reactor prototype has been developed to manufacture by plasma processes all active layers of fuel cell cores to be integrated in original compact PEMFC or DMFC.

STEAM FORMING NEUTRONIC REACTOR AND METHOD OF OPERATING IT

DOEpatents

Untermyer, S.

1960-05-10

The heterogeneous reactor is liquid moderated and cooled by a steam forming coolant and is designed to produce steam from the coolant directly within the active portion of the reactor while avoiding the formation of bubbles in the liquid moderator. This reactor achieves inherent stability as a result of increased neutron leakage and increased neutron resonance absorption in the U/sup 238/ fuel with the formation of bubbles. The invention produces certain conditions under which the formation of vapor bubbles as a result of a neutron flux excursion from the injection of a reactivity increment into the reactor will operate to nullify the reactivity increment within a sufficiently short period of time to prevent unsafe reactor operating conditions from developing. This is obtained by disposing a plurality of fuel elements within a mass of steam forming coolant in the core with the ratio of the volume of steam forming coolant to the volume of fissionable isotopes being within the range yielding a multiplication factor greater than unity and a negative reactivity to core void coefficient at the boiling temperature of the coolant.

In-situ Monitoring of Internal Local Temperature and Voltage of Proton Exchange Membrane Fuel Cells

PubMed Central

Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

2010-01-01

The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm2, and that with a sensor is 426 mW/cm2. Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse. PMID:22163556

In-situ monitoring of internal local temperature and voltage of proton exchange membrane fuel cells.

PubMed

Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

2010-01-01

The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm(2), and that with a sensor is 426 mW/cm(2). Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse.

Effect on combined cycle efficiency of stack gas temperature constraints to avoid acid corrosion

NASA Technical Reports Server (NTRS)

Nainiger, J. J.

1980-01-01

To avoid condensation of sulfuric acid in the gas turbine exhaust when burning fuel oils contaning sulfur, the exhaust stack temperature and cold-end heat exchanger surfaces must be kept above the condensation temperature. Raising the exhaust stack temperature, however, results in lower combined cycle efficiency compared to that achievable by a combined cycle burning a sulfur-free fuel. The maximum difference in efficiency between the use of sulfur-free and fuels containing 0.8 percent sulfur is found to be less than one percentage point. The effect of using a ceramic thermal barrier coating (TBC) and a fuel containing sulfur is also evaluated. The combined-cycle efficiency gain using a TBC with a fuel containing sulfur compared to a sulfur-free fuel without TBC is 0.6 to 1.0 percentage points with air-cooled gas turbines and 1.6 to 1.8 percentage points with water-cooled gas turbines.

Influence of temperature conditions in outer space on the macrokinetic characteristics of ignition and combustion of the solid-fuel charge of the microthruster of a microelectromechanical system

NASA Astrophysics Data System (ADS)

Futko, S. I.; Bondarenko, V. P.; Dolgii, L. N.

2012-03-01

On the basis of macrokinetic calculations, the influence of the initial temperature on the impulse responses of the processes of ignition and combustion of the solid-fuel charge of the microelectromechanical system (MEMS) microthruster burning the solid fuel glycidyl azide polymer (GAP)/RDX has been investigated. It has been established that fuel heating/cooling in a wide range of temperature values from 150 to 450 K characteristic of the conditions of a satellite in orbital flight markedly affects both the thrust and the total impulse of the MEMS microthruster. In so doing, an increase in the initial temperature leads to a marked decrease in the induction period and an increase in the critical flux of fuel ignition. The influence of the change in the initial temperature on the self-ignition temperature of GAP can be neglected. To obtain stable characteristics of the microthruster, it seems expedient to use a thermostating system.

Detailed Multi‐dimensional Modeling of Direct Internal Reforming Solid Oxide Fuel Cells

PubMed Central

Tseronis, K.; Fragkopoulos, I.S.; Bonis, I.

2016-01-01

Abstract Fuel flexibility is a significant advantage of solid oxide fuel cells (SOFCs) and can be attributed to their high operating temperature. Here we consider a direct internal reforming solid oxide fuel cell setup in which a separate fuel reformer is not required. We construct a multidimensional, detailed model of a planar solid oxide fuel cell, where mass transport in the fuel channel is modeled using the Stefan‐Maxwell model, whereas the mass transport within the porous electrodes is simulated using the Dusty‐Gas model. The resulting highly nonlinear model is built into COMSOL Multiphysics, a commercial computational fluid dynamics software, and is validated against experimental data from the literature. A number of parametric studies is performed to obtain insights on the direct internal reforming solid oxide fuel cell system behavior and efficiency, to aid the design procedure. It is shown that internal reforming results in temperature drop close to the inlet and that the direct internal reforming solid oxide fuel cell performance can be enhanced by increasing the operating temperature. It is also observed that decreases in the inlet temperature result in smoother temperature profiles and in the formation of reduced thermal gradients. Furthermore, the direct internal reforming solid oxide fuel cell performance was found to be affected by the thickness of the electrochemically‐active anode catalyst layer, although not always substantially, due to the counter‐balancing behavior of the activation and ohmic overpotentials. PMID:27570502

Resonant structure of low-energy H3+ dissociative recombination

NASA Astrophysics Data System (ADS)

Petrignani, Annemieke; Altevogt, Simon; Berg, Max H.; Bing, Dennis; Grieser, Manfred; Hoffmann, Jens; Jordon-Thaden, Brandon; Krantz, Claude; Mendes, Mario B.; Novotný, Oldřich; Novotny, Steffen; Orlov, Dmitry A.; Repnow, Roland; Sorg, Tobias; Stützel, Julia; Wolf, Andreas; Buhr, Henrik; Kreckel, Holger; Kokoouline, Viatcheslav; Greene, Chris H.

2011-03-01

High-resolution dissociative recombination rate coefficients of rotationally cool and hot H3+ in the vibrational ground state have been measured with a 22-pole trap setup and a Penning ion source, respectively, at the ion storage-ring TSR. The experimental results are compared with theoretical calculations to explore the dependence of the rate coefficient on ion temperature and to study the contributions of different symmetries to probe the rich predicted resonance spectrum. The kinetic energy release was investigated by fragment imaging to derive internal temperatures of the stored parent ions under differing experimental conditions. A systematic experimental assessment of heating effects is performed which, together with a survey of other recent storage-ring data, suggests that the present rotationally cool rate-coefficient measurement was performed at 380-130+50 K and that this is the lowest rotational temperature so far realized in storage-ring rate-coefficient measurements on H3+. This partially supports the theoretical suggestion that temperatures higher than assumed in earlier experiments are the main cause for the large gap between the experimental and the theoretical rate coefficients. For the rotationally hot rate-coefficient measurement a temperature of below 3250 K is derived. From these higher-temperature results it is found that increasing the rotational ion temperature in the calculations cannot fully close the gap between the theoretical and the experimental rate coefficients.

High temperature XRD of Cu2GeSe3

NASA Astrophysics Data System (ADS)

Premkumar D., S.; Chetty, Raju; Malar, P.; Mallik, Ramesh Chandra

2015-06-01

The Cu2GeSe3 is prepared by solid state synthesis method. The high temperature XRD has been done at different temperature from 30 °C to 450 °C. The reitveld refinement confirms Cu2GeSe3 phase and orthorhombic crystal structure. The lattice constants are increasing with increase in the temperature and their rate of increase with respect to temperature are used for finding the thermal expansion coefficient. The calculation of the linear and volume coefficient of thermal expansion is done from 30 °C to 400 °C. Decrease in the values of linear expansion coefficients with temperature are observed along a and c axis. Since thermal expansion coefficient is the consequence of the distortion of atoms in the lattice; this can be further used to find the minimum lattice thermal conductivity at given temperature.

Gas-film coefficients for the volatilization of ketones from water

USGS Publications Warehouse

Rathbun, R.E.; Tai, D.Y.

1986-01-01

Volatilization is a significant process in determining the fate of many organic compounds in streams and rivers. Quantifying this process requires knowledge of the mass-transfer coefficient from water, which is a function of the gas-film and liquid-film coefficients. The gas-film coefficient can be determined by measuring the flux for the volatilization of pure organic liquids. Volatilization fluxes for acetone, 2-butanone, 2-pentanone, 3-pentanone, 4-methyl-2-pentanone, 2-heptanone, and 2-octanone were measured in the laboratory over a range of temperatures. Gas-film coefficients were then calculated from these fluxes and from vapor pressure data from the literature. An equation was developed for predicting the volatilization flux of pure liquid ketones as a function of vapor pressure and molecular weight. Large deviations were found for acetone, and these were attributed to the possibility that acetone may be hydrogen bonded. A second equation for predicting the flux as a function of molecular weight and temperature resulted in large deviations for 4methyl-2-pentanone. These deviations were attributed to the branched structure of this ketone. Four factors based on the theory of volatilization and relating the volatilization flux or rate to the vapor pressure, molecular weight, temperature, and molecular diffusion coefficient were not constant as suggested by the literature. The factors generally increased with molecular weight and with temperature. Values for acetone corresponded to ketones with a larger molecular weight, and the acetone factors showed the greatest dependence on temperature. Both of these results are characteristic of compounds that are hydrogen bonded. Relations from the literature commonly used for describing the dependence of the gas-film coefficient on molecular weight and molecular diffusion coefficient were not applicable to the ketone gas-film coefficients. The dependence on molecular weight and molecular diffusion coefficient was in general U-shaped with the largest coefficients observed for acetone, the next largest for 2octanone, and the smallest for 2-pentanone and 3-pentanone. The gas-film coefficient for acetone was much more dependent on temperature than were the coefficients for the other ketones. Such behavior is characteristic of hydrogen-bonded substances. Temperature dependencies of the other ketones were about twice the theoretical value, but were comparable to a literature value for water. Ratios of the ketone gas-film coefficients to the gasfilm coefficients for the evaporation of water were approximately constant for all the ketones except for acetone, whose values were considerably larger. The ratios increased with temperature; however, the increases were small except for acetone. These ratios can be combined with an equation from the literaure for predicting the gasfilm coefficient for evaporation of water from a canal to predict the gas-film coefficients for the volatilization of ketones from streams and rivers.

Carbide fuel pin and capsule design for irradiations at thermionic temperatures

NASA Technical Reports Server (NTRS)

Siegel, B. L.; Slaby, J. G.; Mattson, W. F.; Dilanni, D. C.

1973-01-01

The design of a capsule assembly to evaluate tungsten-emitter - carbide-fuel combinations for thermionic fuel elements is presented. An inpile fuel pin evaluation program concerned with clad temperture, neutron spectrum, carbide fuel composition, fuel geometry,fuel density, and clad thickness is discussed. The capsule design was a compromise involving considerations between heat transfer, instrumentation, materials compatibility, and test location. Heat-transfer calculations were instrumental in determining the method of support of the fuel pin to minimize axial temperature variations. The capsule design was easily fabricable and utilized existing state-of-the-art experience from previous programs.

Heat exchanger for fuel cell power plant reformer

DOEpatents

Misage, Robert; Scheffler, Glenn W.; Setzer, Herbert J.; Margiott, Paul R.; Parenti, Jr., Edmund K.

1988-01-01

A heat exchanger uses the heat from processed fuel gas from a reformer for a fuel cell to superheat steam, to preheat raw fuel prior to entering the reformer and to heat a water-steam coolant mixture from the fuel cells. The processed fuel gas temperature is thus lowered to a level useful in the fuel cell reaction. The four temperature adjustments are accomplished in a single heat exchanger with only three heat transfer cores. The heat exchanger is preheated by circulating coolant and purge steam from the power section during startup of the latter.

The Joint Toxicity of Different Temperature Coefficient Insecticides on Apolygus lucorum (Hemiptera: Miridae)

USDA-ARS?s Scientific Manuscript database

The effect of temperature on the co-toxicity coefficients (CTC) value was used to evaluate mixture efficacy of different temperature coefficient chemicals from 15°C to 35°C by exposing third-instar Apolygus lucorum (Meyer-Dür) to dip-treated asparagus bean pods. The results indicated the joint actio...

Block Copolymers for Alkaline Fuel Cell Membrane Materials

DTIC Science & Technology

2014-07-30

temperature fuel cells including proton exchange membrane fuel cell ( PEMFC ) and alkaline fuel cell (AFC) with operation temperature usually lower than 120...advantages over proton exchange membrane fuel cells ( PEMFCs ) resulting in the popularity of AFCs in the US space program.[8-11] The primary benefit AFC...offered over PEMFC is better electrochemical kinetics on the anode and cathode under the alkaline environment, which results in the ability to use

Evaluation of the finite element fuel rod analysis code (FRANCO)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, K.; Feltus, M.A.

1994-12-31

Knowledge of temperature distribution in a nuclear fuel rod is required to predict the behavior of fuel elements during operating conditions. The thermal and mechanical properties and performance characteristics are strongly dependent on the temperature, which can vary greatly inside the fuel rod. A detailed model of fuel rod behavior can be described by various numerical methods, including the finite element approach. The finite element method has been successfully used in many engineering applications, including nuclear piping and reactor component analysis. However, fuel pin analysis has traditionally been carried out with finite difference codes, with the exception of Electric Powermore » Research Institute`s FREY code, which was developed for mainframe execution. This report describes FRANCO, a finite element fuel rod analysis code capable of computing temperature disrtibution and mechanical deformation of a single light water reactor fuel rod.« less

Charring temperatures are driven by the fuel types burned in a peatland wildfire

PubMed Central

Hudspith, Victoria A.; Belcher, Claire M.; Yearsley, Jonathan M.

2014-01-01

Peatlands represent a globally important carbon store; however, the human exploitation of this ecosystem is increasing both the frequency and severity of fires on drained peatlands. Yet, the interactions between the hydrological conditions (ecotopes), the fuel types being burned, the burn severity, and the charring temperatures (pyrolysis intensity) remain poorly understood. Here we present a post-burn assessment of a fire on a lowland raised bog in Co. Offaly, Ireland (All Saints Bog). Three burn severities were identified in the field (light, moderate, and deeply burned), and surface charcoals were taken from 17 sites across all burn severities. Charcoals were classified into two fuel type categories (either ground or aboveground fuel) and the reflectance of each charcoal particle was measured under oil using reflectance microscopy. Charcoal reflectance shows a positive relationship with charring temperature and as such can be used as a temperature proxy to reconstruct minimum charring temperatures after a fire event. Resulting median reflectance values for ground fuels are 1.09 ± 0.32%Romedian, corresponding to estimated minimum charring temperatures of 447°C ± 49°C. In contrast, the median charring temperatures of aboveground fuels were found to be considerably higher, 646°C ± 73°C (3.58 ± 0.77%Romedian). A mixed-effects modeling approach was used to demonstrate that the interaction effects of burn severity, as well as ecotope classes, on the charcoal reflectance is small compared to the main effect of fuel type. Our findings reveal that the different fuel types on raised bogs are capable of charring at different temperatures within the same fire, and that the pyrolysis intensity of the fire on All Saints Bog was primarily driven by the fuel types burning, with only a weak association to the burn severity or ecotope classes. PMID:25566288

Temperature measuring analysis of the nuclear reactor fuel assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, F., E-mail: jozef.bereznai@stuba.sk, E-mail: zdenko.zavodny@stuba.sk; Kučák, L., E-mail: jozef.bereznai@stuba.sk, E-mail: zdenko.zavodny@stuba.sk; Bereznai, J., E-mail: jozef.bereznai@stuba.sk, E-mail: zdenko.zavodny@stuba.sk

2014-08-06

Study was based on rapid changes of measured temperature values from the thermocouple in the VVER 440 nuclear reactor fuel assembly. Task was to determine origin of fluctuations of the temperature values by experiments on physical model of the fuel assembly. During an experiment, heated water was circulating in the system and cold water inlet through central tube to record sensitivity of the temperature sensor. Two positions of the sensor was used. First, just above the central tube in the physical model fuel assembly axis and second at the position of the thermocouple in the VVER 440 nuclear reactor fuelmore » assembly. Dependency of the temperature values on time are presented in the diagram form in the paper.« less

Flight and Preflight Tests of a Ram Jet Burning Magnesium Slurry Fuel and Utilizing a Solid-propellant Gas Generator for Fuel Expulsion

NASA Technical Reports Server (NTRS)

Bartlett, Walter, A , jr; Hagginbotham, William K , Jr

1955-01-01

Data obtained from the first flight test of a ram jet utilizing a magnesium slurry fuel are presented. The ram jet accelerated from a Mach number of 1.75 to a Mach number of 3.48 in 15.5 seconds. During this period a maximum values of air specific impulse and gross thrust coefficient were calculated to be 151 seconds and 0.658, respectively. The rocket gas generator used as a fuel-pumping system operated successfully.

Details of the Construction and Production of Fuel Pumps and Fuel Nozzles for the Airplane Diesel Engine

NASA Technical Reports Server (NTRS)

Lubenetsky, W S

1936-01-01

This report presents investigations into the design and construction of fuel pumps for diesel engines. The results of the pump tests on the engines showed that, with a good cut-off, accurate injection, assured by the proper adjustment of the pump elements, there is a decrease in the consumption of fuel and hence an increase in the rated power of the engine. Some of the aspects investigated include: cam profile, coefficient of discharge, and characteristics of the injection system.

Antimisting kerosene: Low temperature degradation and blending

NASA Technical Reports Server (NTRS)

Yavrouian, A.; Parikh, P.; Sarohia, V.

1988-01-01

The inline filtration characteristics of freshly blended and degraded antimisting fuels (AMK) at low temperature are examined. A needle valve degrader was modified to include partial recirculation of degraded fuel and heat addition in the bypass loop. A pressure drop across the needle valve of up to 4,000 psi was used. The pressure drop across a 325 mesh filter screen placed inline with the degrader and directly downstream of the needle valve was measured as a function of time for different values of pressure drop across the needle valve. A volume flux of 1 gpm/sq in was employed based on the frontal area of the screen. It was found that, at ambient temperatures, freshly blended AMK fuel could be degraded using a single pass degradation at 4,000 psi pressure drop across the needle valve to give acceptable filterability performance. At fuel temperatures below -20 C, degradation becomes increasingly difficult and a single pass technique results in unacceptable filtration performance. Recirculation of a fraction of the degraded fuel and heat addition in the bypass loop improved low temperature degradation performance. The problem is addressed of blending the AMK additive with Jet A at various base fuel temperatures.

High-Temperature Piezoelectric Ceramic Developed

NASA Technical Reports Server (NTRS)

Sayir, Ali; Farmer, Serene C.; Dynys, Frederick W.

2005-01-01

Active combustion control of spatial and temporal variations in the local fuel-to-air ratio is of considerable interest for suppressing combustion instabilities in lean gas turbine combustors and, thereby, achieving lower NOx levels. The actuator for fuel modulation in gas turbine combustors must meet several requirements: (1) bandwidth capability of 1000 Hz, (2) operating temperature compatible with the fuel temperature, which is in the vicinity of 400 F, (3) stroke of approximately 4 mils (100 m), and (4) force of 300 lb-force. Piezoelectric actuators offer the fastest response time (microsecond time constants) and can generate forces in excess of 2000 lb-force. The state-of-the-art piezoceramic material in industry today is Pb(Zr,Ti)O3, called PZT. This class of piezoelectric ceramic is currently used in diesel fuel injectors and in the development of high-response fuel modulation valves. PZT materials are generally limited to operating temperatures of 250 F, which is 150 F lower than the desired operating temperature for gas turbine combustor fuel-modulation injection valves. Thus, there is a clear need to increase the operating temperature range of piezoceramic devices for active combustion control in gas turbine engines.

Transport coefficients in high-temperature ionized air flows with electronic excitation

NASA Astrophysics Data System (ADS)

Istomin, V. A.; Oblapenko, G. P.

2018-01-01

Transport coefficients are studied in high-temperature ionized air mixtures using the modified Chapman-Enskog method. The 11-component mixture N2/N2+/N /N+/O2/O2+/O /O+/N O /N O+/e- , taking into account the rotational and vibrational degrees of freedom of molecules and electronic degrees of freedom of both atomic and molecular species, is considered. Using the PAINeT software package, developed by the authors of the paper, in wide temperature range calculations of the thermal conductivity, thermal diffusion, diffusion, and shear viscosity coefficients for an equilibrium ionized air mixture and non-equilibrium flow conditions for mixture compositions, characteristic of those in shock tube experiments and re-entry conditions, are performed. For the equilibrium air case, the computed transport coefficients are compared to those obtained using simplified kinetic theory algorithms. It is shown that neglecting electronic excitation leads to a significant underestimation of the thermal conductivity coefficient at temperatures higher than 25 000 K. For non-equilibrium test cases, it is shown that the thermal diffusion coefficients of neutral species and the self-diffusion coefficients of all species are strongly affected by the mixture composition, while the thermal conductivity coefficient is most strongly influenced by the degree of ionization of the flow. Neglecting electronic excitation causes noticeable underestimation of the thermal conductivity coefficient at temperatures higher than 20 000 K.

Lowering the temperature of solid oxide fuel cells.

PubMed

Wachsman, Eric D; Lee, Kang Taek

2011-11-18

Fuel cells are uniquely capable of overcoming combustion efficiency limitations (e.g., the Carnot cycle). However, the linking of fuel cells (an energy conversion device) and hydrogen (an energy carrier) has emphasized investment in proton-exchange membrane fuel cells as part of a larger hydrogen economy and thus relegated fuel cells to a future technology. In contrast, solid oxide fuel cells are capable of operating on conventional fuels (as well as hydrogen) today. The main issue for solid oxide fuel cells is high operating temperature (about 800°C) and the resulting materials and cost limitations and operating complexities (e.g., thermal cycling). Recent solid oxide fuel cells results have demonstrated extremely high power densities of about 2 watts per square centimeter at 650°C along with flexible fueling, thus enabling higher efficiency within the current fuel infrastructure. Newly developed, high-conductivity electrolytes and nanostructured electrode designs provide a path for further performance improvement at much lower temperatures, down to ~350°C, thus providing opportunity to transform the way we convert and store energy.

Experiments on fuel heating for commercial aircraft

NASA Technical Reports Server (NTRS)

Friedman, R.; Stockemer, F. J.

1982-01-01

An experimental jet fuel with a -33 C freezing point was chilled in a wing tank simulator with superimposed fuel heating to improve low temperature flowability. Heating consisted of circulating a portion of the fuel to an external heat exchanger and returning the heated fuel to the tank. Flowability was determined by the mass percent of unpumpable fuel (holdup) left in the simulator upon withdrawal of fuel at the conclusion of testing. The study demonstrated that fuel heating is feasible and improves flowability as compared to that of baseline, unheated tests. Delayed heating with initiation when the fuel reaches a prescribed low temperature limit, showed promise of being more efficient than continuous heating. Regardless of the mode or rate of heating, complete flowability (zero holdup) could not be restored by fuel heating. The severe, extreme-day environment imposed by the test caused a very small amount of subfreezing fuel to be retained near the tank surfaces even at high rates of heating. Correlations of flowability established for unheated fuel tests also could be applied to the heated test results if based on boundary-layer temperature or a solid index (subfreezing point) characteristic of the fuel.

Self-ignition of S.I. engine model fuels: A shock tube investigation at high pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fieweger, K.; Blumenthal, R.; Adomeit, G.

1997-06-01

The self-ignition of several spark-ignition (SI) engine fuels (iso-octane, methanol, methyl tert-butyl ether and three different mixtures of iso-octane and n-heptane), mixed with air, was investigated experimentally under relevant engine conditions by the shock tube technique. Typical modes of the self-ignition process were registered cinematographically. For temperatures relevant to piston engine combustion, the self-ignition process always starts as an inhomogeneous, deflagrative mild ignition. This instant is defined by the ignition delay time, {tau}{sub defl}. The deflagration process in most cases is followed by a secondary explosion (DDT). This transition defines a second ignition delay time, {tau}{sub DDT}, which is amore » suitable approximation for the chemical ignition delay time, if the change of the thermodynamic conditions of the unburned test gas due to deflagration is taken into account. For iso-octane at p = 40 bar, a NTC (negative temperature coefficient), behavior connected with a two step (cool flame) self-ignition at low temperatures was observed. This process was very pronounced for rich and less pronounced for stoichiometric mixtures. The results of the {tau}{sub DDT} delays of the stoichiometric mixtures were shortened by the primary deflagration process in the temperature range between 800 and 1,000 K. Various mixtures of iso-octane and n-heptane were investigated. The results show a strong influence of the n-heptane fraction in the mixture, both on the ignition delay time and on the mode of self-ignition. The self-ignition of methanol and MTBE (methyl tert-butyl ether) is characterized by a very pronounced initial deflagration. For temperatures below 900 K (methanol: 800 K), no secondary explosion occurs. Taking into account the pressure increase due to deflagration, the measured delays {tau}{sub DDT} of the secondary explosion are shortened by up to one order of magnitude.« less

Preparation of high temperature gas-cooled reactor fuel element

DOEpatents

Bradley, Ronnie A.; Sease, John D.

1976-01-01

This invention relates to a method for the preparation of high temperature gas-cooled reactor (HTGR) fuel elements wherein uncarbonized fuel rods are inserted in appropriate channels of an HTGR fuel element block and the entire block is inserted in an autoclave for in situ carbonization under high pressure. The method is particularly applicable to remote handling techniques.

Laboratory Test of Reciprocating Internal Combustion Engines

DTIC Science & Technology

2016-02-04

testing require extremely accurate fuel consumption measurement, and the ability to temperature condition the fuel. Most dynamometer manufacturers...include, but are not limited to, differences in fuels, lubrication, temperatures , engine control module parameters, component wear, exhaust, and air...exhaust gas recirculation (EGR) fuel consumption 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT SAR 18. NUMBER OF PAGES 38

Methods for manufacturing porous nuclear fuel elements for high-temperature gas-cooled nuclear reactors

DOEpatents

Youchison, Dennis L [Albuquerque, NM; Williams, Brian E [Pocoima, CA; Benander, Robert E [Pacoima, CA

2010-02-23

Methods for manufacturing porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's). Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, a thin coating of nuclear fuel may be deposited inside of a highly porous skeletal structure made, for example, of reticulated vitreous carbon foam.

Porous nuclear fuel element for high-temperature gas-cooled nuclear reactors

DOEpatents

Youchison, Dennis L [Albuquerque, NM; Williams, Brian E [Pacoima, CA; Benander, Robert E [Pacoima, CA

2011-03-01

Porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's), and to processes for fabricating them. Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, the nuclear fuel may be deposited inside of a highly porous skeletal structure made of, for example, reticulated vitreous carbon foam.

Porous nuclear fuel element with internal skeleton for high-temperature gas-cooled nuclear reactors

DOEpatents

Youchison, Dennis L.; Williams, Brian E.; Benander, Robert E.

2013-09-03

Porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's), and to processes for fabricating them. Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, the nuclear fuel may be deposited inside of a highly porous skeletal structure made of, for example, reticulated vitreous carbon foam.

Glass binder development for a glass-bonded sodalite ceramic waste form

NASA Astrophysics Data System (ADS)

Riley, Brian J.; Vienna, John D.; Frank, Steven M.; Kroll, Jared O.; Peterson, Jacob A.; Canfield, Nathan L.; Zhu, Zihua; Zhang, Jiandong; Kruska, Karen; Schreiber, Daniel K.; Crum, Jarrod V.

2017-06-01

This paper discusses work to develop Na2O-B2O3-SiO2 glass binders for immobilizing LiCl-KCl eutectic salt waste in a glass-bonded sodalite waste form following electrochemical reprocessing of used metallic nuclear fuel. Here, five new glasses with ∼20 mass% Na2O were designed to generate waste forms with high sodalite. The glasses were then used to produce ceramic waste forms with a surrogate salt waste. The waste forms made using these new glasses were formulated to generate more sodalite than those made with previous baseline glasses for this type of waste. The coefficients of thermal expansion for the glass phase in the glass-bonded sodalite waste forms made with the new binder glasses were closer to the sodalite phase in the critical temperature region near and below the glass transition temperature than previous binder glasses used. These improvements should result in lower probability of cracking in the full-scale monolithic ceramic waste form, leading to better long-term chemical durability.

Loyola University, New Orleans, Louisiana solar energy system performance evaluation, February 1981 - June 1981

NASA Astrophysics Data System (ADS)

Welch, K. M.

1981-09-01

The Loyola University site is a student dormitory in New Orleans, Louisiana whose active solar energy system is designed to supply 52% of the hot water demand. The system is equipped with 4590 square feet of flat-plate collectors, a 5000-gallon water tank, auxiliary water supplied at high temperature and pressure from a central heating plant with a gas-fired boiler, and a differential controller that selects from 5 operating modes. System performance data are given, including the solar fraction, solar savings ratio, conventional fuel savings, system performance factor, and system coefficient of performance. The solar fraction is well below the design goal; this is attributed to great fluctuations in demand. Insolation, temperature, operation and solar energy utilization data are also presented. The performance of the collector, storage, and domestic hot water subsystems, the system operating energy, energy savings, and weather conditions are also evaluated. Appended are a system description, performance evaluation techniques and equations, site history, sensor technology, and typical monthly data.

A Methodology for Multidisciplinary Decision Making for a Surface Combatant Main Engine Selection Problem

DTIC Science & Technology

2014-06-01

nautical miles per hour ONR Office of Naval Research OPC overall propulsive coefficient RS repairable at sea SFC specific fuel consumption SHP shaft...fmSFC SHP hp =  (2.3) Overall Propulsive Coefficient ( OPC ) The overall propulsive coefficient is equal to the ratio between the effective...horsepower (EHP), and the total installed shaft horsepower (SHP) delivered by the main engine [6]. OPC can be determined using the following relationship

Numerical determination of lateral loss coefficients for subchannel analysis in nuclear fuel bundles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sin Kim; Goon-Cherl Park

1995-09-01

An accurate prediction of cross-flow based on detailed knowledge of the velocity field in subchannels of a nuclear fuel assembly is of importance in nuclear fuel performance analysis. In this study, the low-Reynolds number {kappa}-{epsilon} turbulence model has been adopted in two adjacent subchannels with cross-flow. The secondary flow is estimated accurately by the anisotropic algebraic Reynolds stress model. This model was numerically calculated by the finite element method and has been verified successfully through comparison with existing experimental data. Finally, with the numerical analysis of the velocity field in such subchannel domain, an analytical correlation of the lateral lossmore » coefficient is obtained to predict the cross-flow rate in subchannel analysis codes. The correlation is expressed as a function of the ratio of the lateral flow velocity to the donor subchannel axial velocity, recipient channel Reynolds number and pitch-to-diameter.« less

Diffusivities of Ag, Cs, Sr, and Kr in TRISO fuel particles and graphite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collin, Blaise Paul

Tri-structural isotropic (TRISO) coated particles have been developed and studied since the late 1950s when the concept of coated particles was invented by Roy Huddle of the United Kingdom Atomic Energy Authority. Several decades of work by half a dozen countries on fission product transport in TRISO fuel through numerous irradiation and heating experiments have led to several recommendations of transport data and to the adoption of various sets of diffusion coefficients. In 1997, the International Atomic Energy Agency (IAEA) gathered all these historical results and issued a technical document (TECDOC-978 [IAEA]) that summarizes these sets of recommended diffusion coefficients.more » Table 1 shows the reference literature articles for the diffusivities that have historically been recommended by the American and German TRISO fuel development programs and that are summarized in the IAEA report (see section 7 for full references of these articles).« less

Thermal Expansion of Ferromagnetic Superconductors:. Possible Application to UGe2

NASA Astrophysics Data System (ADS)

Hatayama, Nobukuni; Konno, Rikio

2011-03-01

We investigate the temperature dependence of thermal expansion of the ferromagnetic triplet superconductors and their thermal expansion coefficients below the superconducting transition temperature of a majority spin conduction band. The free energy of the ferromagnetic superconductors derived by Linder et al. is used. The superconducting gaps in the A2 phase of 3He and with a node in UGe2 are considered. By applying Takahashi's method to the free energy, i.e. by taking into account the volume dependence of the free energy explicitly, the temperature dependence of the thermal expansion and the thermal expansion coefficients is studied below the superconducting transition temperature of the majority spin conduction band. We find that we have anomalies of the thermal expansion in the vicinity of the superconducting transition temperatures and that we have divergence of the thermal expansion coefficients are divergent at the superconducting transition temperatures. The Grüneisen's relation between the temperature dependence of the thermal expansion coefficients and the temperature dependence of the specific heat at low temperatures is satisfied.

Thermal Expansion of Ferromagnetic Superconductors:. Possible Application to UGe2

NASA Astrophysics Data System (ADS)

Hatayama, Nobukuni; Konno, Rikio

We investigate the temperature dependence of thermal expansion of the ferromagnetic triplet superconductors and their thermal expansion coefficients below the superconducting transition temperature of a majority spin conduction band. The free energy of the ferromagnetic superconductors derived by Linder et al. is used. The superconducting gaps in the A2 phase of 3He and with a node in UGe2 are considered. By applying Takahashi's method to the free energy, i.e. by taking into account the volume dependence of the free energy explicitly, the temperature dependence of the thermal expansion and the thermal expansion coefficients is studied below the superconducting transition temperature of the majority spin conduction band. We find that we have anomalies of the thermal expansion in the vicinity of the superconducting transition temperatures and that we have divergence of the thermal expansion coefficients are divergent at the superconducting transition temperatures. The Grüneisen's relation between the temperature dependence of the thermal expansion coefficients and the temperature dependence of the specific heat at low temperatures is satisfied.

Simultaneous imaging of fuel vapor mass fraction and gas-phase temperature inside gasoline sprays using two-line excitation tracer planar laser-induced fluorescence.

PubMed

Zigan, Lars; Trost, Johannes; Leipertz, Alfred

2016-02-20

This paper reports for the first time, to the best of our knowledge, on the simultaneous imaging of the gas-phase temperature and fuel vapor mass fraction distribution in a direct-injection spark-ignition (DISI) spray under engine-relevant conditions using tracer planar laser-induced fluorescence (TPLIF). For measurements in the spray, the fluorescence tracer 3-pentanone is added to the nonfluorescent surrogate fuel iso-octane, which is excited quasi-simultaneously by two different excimer lasers for two-line excitation LIF. The gas-phase temperature of the mixture of fuel vapor and surrounding gas and the fuel vapor mass fraction can be calculated from the two LIF signals. The measurements are conducted in a high-temperature, high-pressure injection chamber. The fluorescence calibration of the tracer was executed in a flow cell and extended significantly compared to the existing database. A detailed error analysis for both calibration and measurement is provided. Simultaneous single-shot gas-phase temperature and fuel vapor mass fraction fields are processed for the assessment of cyclic spray fluctuations.

High temperature XRD of Cu{sub 2}GeSe{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Premkumar, D. S.; Malar, P.; Chetty, Raju

2015-06-24

The Cu{sub 2}GeSe{sub 3} is prepared by solid state synthesis method. The high temperature XRD has been done at different temperature from 30 °C to 450 °C. The reitveld refinement confirms Cu{sub 2}GeSe{sub 3} phase and orthorhombic crystal structure. The lattice constants are increasing with increase in the temperature and their rate of increase with respect to temperature are used for finding the thermal expansion coefficient. The calculation of the linear and volume coefficient of thermal expansion is done from 30 °C to 400 °C. Decrease in the values of linear expansion coefficients with temperature are observed along a andmore » c axis. Since thermal expansion coefficient is the consequence of the distortion of atoms in the lattice; this can be further used to find the minimum lattice thermal conductivity at given temperature.« less

Recovery of minor actinides from spent fuel using TPEN-immobilized gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koyama, S.; Suto, M.; Ohbayashi, H.

2013-07-01

A series of separation experiments was performed in order to study the recovery process for minor actinides (MAs), such as americium (Am) and curium (Cm), from the actual spent fuel by using an extraction chromatographic technique. N,N,N',N'-tetrakis-(4-propenyloxy-2-pyridylmethyl) ethylenediamine (TPPEN) is an N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN) analogue consisting of an incorporated pyridine ring that acts as not only a ligand but also as a site for polymerization and crosslinking of the gel. The TPPEN and N-isopropylacrylamide (NIPA) were dissolved into dimethylformamide (DMF, Wako Co., Ltd.) and a silica beads polymer, and then TTPEN was immobilized chemically in a polymer gel (somore » called TPEN-gel). Mixed oxide (MOX) fuel, which was highly irradiated up to 119 GWD/MTM in the experimental fast reactor Joyo, was used as a reference spent fuel. First, uranium (U) and plutonium (Pu) were separated from the irradiated fuel using an ion-exchange method, and then, the platinum group elements were removed by CMPO to leave a mixed solution of MAs and lanthanides. The 3 mol% TPPEN-gel was packed with as an extraction column (CV: 1 ml) and then rinsed by 0.1 M NaNO{sub 3}(pH 4.0) for pH adjustment. After washing the column by 0.01 M NaNO{sub 3} (pH 4.0), Eu was detected and the recovery rate reached 93%. The MAs were then recovered by changing the eluent to 0.01 M NaNO{sub 3} (pH 2.0), and the recovery rate of Am was 48 %. The 10 mol% TPPEN-gel was used to improve adsorption coefficient of Am and a condition of eluent temperature was changed in order to confirm the temperature swing effect on TPEN-gel for MA. More than 90% Eu was detected in the eluent after washing with 0.01 M NaNO{sub 3} (pH 3.5) at 5 Celsius degrees. Americium was backwardly detected and eluted continuously during the same condition. After removal of Eu, the eluent temperature was changed to 32 Celsius degrees, then Am was detected (pH 3.0). Finally remained Am could be stripped from TPPEN-gel by changing the pH of the eluent to 2.0. These results These results prove that the proposed recovery process for MAs is a potential candidate for future reprocessing methods based on the extraction chromatographic technique. (authors)« less

Advanced Thermally Stable Coal-Based Jet Fuels

DTIC Science & Technology

2008-02-01

of hydrotreated refined chemical oil derived jet fuels in the pyrolytic regime. Preprints of Papers-American Chemical Society Division of Fuel...hydrogenation of a mixture of light cycle oil and refined chemical oil met or exceeded all but four JP-8 specifications. The fuel has excellent low-temperature...mixture of light cycle oil and refined chemical oil met or exceeded all but four JP-8 specifications. The fuel has excellent low-temperature viscosity

Comprehensive kinetic model for the low-temperature oxidation of hydrocarbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaffuri, P.; Faravelli, T.; Ranzi, E.

1997-05-01

The oxidation chemistry in the low- and intermediate-temperature regimes (600--900 K) is important and plays a significant role in the overall combustion process. Autoignition in diesel engines as well as end-gas autoignition and knock phenomena in s.i. engines are initiated at these low temperatures. The low-temperature oxidation chemistry of linear and branched alkanes is discussed with the aim of unifying their complex behavior in various experimental systems using a single detailed kinetic model. New experimental data, obtained in a pressurized flow reactor, as well as in batch- and jet-stirred reactors, are useful for a better definition of the region ofmore » cool flames and negative temperature coefficient (NTC) for pure hydrocarbons from propane up to isooctane. Thermochemical oscillations and the NTC region of the reaction rate of the low-temperature oxidation of n-heptane and isooctane in a jet-stirred flow reactor are reproduced quite well by the model, not only in a qualitative way but in terms of the experimental frequencies and intensities of cool flames. Very good agreement is also observed for fuel conversion and intermediate-species formation. Irrespective of the experimental system, the same critical reaction steps always control these phenomena. The results contribute to the definition of a limited set of fundamental kinetic parameters that should be easily extended to model heavier alkanes.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ingham, J.G.

Maximum cladding temperatures occur when the IDENT 1578 fuel pin shipping container is installed in the T-3 Cask. The maximum allowable cladding temperature of 800/sup 0/F is reached when the rate of energy deposited in the 19-pin basket reaches 400 watts. Since 45% of the energy which is generated in the fuel escapes the 19-pin basket without being deposited, mostly gamma energy, the maximum allowable rate of heat generation is 400/.55 = 727 watts. Similarly, the maximum allowable cladding temperature of 800/sup 0/F is reached when the rate of energy deposited in the 40-pin basket reaches 465 watts. Since 33%more » of the energy which is generated in the fuel escapes the 40-pin basket without being deposited, mostly gamma energy, the maximum allowable rate of heat generation is 465/.66 = 704 watts. The IDENT 1578 fuel pin shipping container therefore meets its thermal design criteria. IDENT 1578 can handle fuel pins with a decay heat load of 600 watts while maintaining the maximum fuel pin cladding temperature below 800/sup 0/F. The emissivities which were determined from the test results for the basket tubes and container are relatively low and correspond to new, shiny conditions. As the IDENT 1578 container is exposed to high temperatures for extended periods of time during the transportation of fuel pins, the emissivities will probably increase. This will result in reduced temperatures.« less

Effects of Cold Temperature and Ethanol Content on VOC Emissions from Light-Duty Gasoline Vehicles.

PubMed

George, Ingrid J; Hays, Michael D; Herrington, Jason S; Preston, William; Snow, Richard; Faircloth, James; George, Barbara Jane; Long, Thomas; Baldauf, Richard W

2015-11-03

Emissions of speciated volatile organic compounds (VOCs), including mobile source air toxics (MSATs), were measured in vehicle exhaust from three light-duty spark ignition vehicles operating on summer and winter grade gasoline (E0) and ethanol blended (E10 and E85) fuels. Vehicle testing was conducted using a three-phase LA92 driving cycle in a temperature-controlled chassis dynamometer at two ambient temperatures (-7 and 24 °C). The cold start driving phase and cold ambient temperature increased VOC and MSAT emissions up to several orders of magnitude compared to emissions during other vehicle operation phases and warm ambient temperature testing, respectively. As a result, calculated ozone formation potentials (OFPs) were 7 to 21 times greater for the cold starts during cold temperature tests than comparable warm temperature tests. The use of E85 fuel generally led to substantial reductions in hydrocarbons and increases in oxygenates such as ethanol and acetaldehyde compared to E0 and E10 fuels. However, at the same ambient temperature, the VOC emissions from the E0 and E10 fuels and OFPs from all fuels were not significantly different. Cold temperature effects on cold start MSAT emissions varied by individual MSAT compound, but were consistent over a range of modern spark ignition vehicles.

Heat transfer and fire spread

Treesearch

Hal E. Anderson

1969-01-01

Experimental testing of a mathematical model showed that radiant heat transfer accounted for no more than 40% of total heat flux required to maintain rate of spread. A reasonable prediction of spread was possible by assuming a horizontal convective heat transfer coefficient when certain fuel and flame characteristics were known. Fuel particle size had a linear relation...

Metallography and fuel cladding chemical interaction in fast flux test facility irradiated metallic U-10Zr MFF-3 and MFF-5 fuel pins

DOE PAGES

Carmack, W. Jon; Chichester, Heather M.; Porter, Douglas L.; ...

2016-02-27

The Mechanistic Fuel Failure (MFF) series of metal fuel irradiations conducted in the Fast Flux Test Facility (FFTF) provides an important potential comparison between data generated in the Experimental Breeder Reactor (EBR-II) and that expected in a larger-scale fast reactor. The irradiations were the beginning tests to qualify U-10wt%Zr as a driver fuel for FFTF. The FFTF core, with a 91.4 cm tall fuel column and a chopped cosine neutron flux profile, operated with a peak cladding temperature at the top of the fuel column, but developed peak burnup at the centerline of the core. This then places the peakmore » fuel temperature midway between the core center and the top of fuel, lower in the fuel column than in previous EBR-II experiments that had a 32-cm height core. The MFF-3 and MFF-5 qualification assemblies operated in FFTF to >10 at% burnup, and performed very well with no cladding breaches. The MFF-3 assembly operated to 13.8 at% burnup with a peak inner cladding temperature of 643°C, and the MFF-5 assembly operated to 10.1 at% burnup with a peak inner cladding temperature of 651°C. Because of the very high operating temperatures for both the fuel and the cladding, data from the MFF assemblies are most comparable to the data obtained from the EBR-II X447 experiment, which experienced two pin breaches. The X447 breaches were strongly influenced by a large amount of fuel/cladding chemical interaction (FCCI). The MFF pins benefitted from different axial locations of high burnup and peak cladding temperature, which helped to reduce interdiffusion between rare earth fission products and stainless steel cladding. Post-irradiation examination evidence illustrates this advantage. After comparing other performance data of the long MFF pins to prior EBR-II test data, the MFF fuel inside the cladding grew less axially, and the gas release data did not reveal a definitive difference.« less

Metallography and fuel cladding chemical interaction in fast flux test facility irradiated metallic U-10Zr MFF-3 and MFF-5 fuel pins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmack, W. J.; Chichester, H. M.; Porter, D. L.

2016-05-01

Abstract The Mechanistic Fuel Failure (MFF) series of metal fuel irradiations conducted in the Fast Flux Test Facility (FFTF) provides an important potential comparison between data generated in the Experimental Breeder Reactor (EBR-II) and that expected in a larger-scale fast reactor. The irradiations were the beginning tests to qualify U-10wt%Zr as a driver fuel for FFTF. The FFTF core, with a 91.4 cm tall fuel column and a chopped cosine neutron flux profile, operated with a peak cladding temperature at the top of the fuel column, but developed peak burnup at the centerline of the core. This places the peakmore » fuel temperature midway between the core center and the top of fuel, lower in the fuel column than in previous EBR-II experiments that had a 32-cm height core. The MFF-3 and MFF-5 qualification assemblies operated in FFTF to >10 at% burnup, and performed very well with no cladding breaches. The MFF-3 assembly operated to 13.8 at% burnup with a peak inner cladding temperature of 643°C, and the MFF-5 assembly operated to 10.1 at% burnup with a peak inner cladding temperature of 651°C. Because of the very high operating temperatures for both the fuel and the cladding, data from the MFF assemblies are most comparable to the data obtained from the EBR-II X447 experiment, which experienced two pin breaches. The X447 breaches were strongly influenced by a large amount of fuel/cladding chemical interaction (FCCI). The MFF pins benefitted from different axial locations of high burnup and peak cladding temperature, which helped to reduce interdiffusion between rare earth fission products and stainless steel cladding. Post-irradiation examination evidence illustrates this advantage. Comparing other performance data of the long MFF pins to prior EBR-II test data, the MFF fuel inside the cladding grew less axially, and the gas release data did not reveal a definitive difference.« less

Potential impacts of Brayton and Stirling cycle engines

NASA Astrophysics Data System (ADS)

Heft, R. C.

1980-11-01

Two engine technologies (Brayton cycle and Stirling cycle) are examined for their potential economic impact and fuel utilization. An economic analysis of the expected response of buyers to the attributes of the alternative engines was performed. Hedonic coefficients for vehicle fuel efficiency, performance and size were estimated for domestic cars based upon historical data. The marketplace value of the fuel efficiency enhancement provided by Brayton or Stirling engines was estimated. Under the assumptions of 10 years for plant conversions and 1990 and 1995 as the introduction data for turbine and Stirling engines respectively, the comparative fuel savings and present value of the future savings in fuel costs were estimated.

Potential impacts of Brayton and Stirling cycle engines

NASA Technical Reports Server (NTRS)

Heft, R. C.

1980-01-01

Two engine technologies (Brayton cycle and Stirling cycle) are examined for their potential economic impact and fuel utilization. An economic analysis of the expected response of buyers to the attributes of the alternative engines was performed. Hedonic coefficients for vehicle fuel efficiency, performance and size were estimated for domestic cars based upon historical data. The marketplace value of the fuel efficiency enhancement provided by Brayton or Stirling engines was estimated. Under the assumptions of 10 years for plant conversions and 1990 and 1995 as the introduction data for turbine and Stirling engines respectively, the comparative fuel savings and present value of the future savings in fuel costs were estimated.

FUEL ELEMENT FOR A NUCLEAR REACTOR

DOEpatents

Davidson, J.K.

1963-11-19

A fuel element structure particularly useful in high temperature nuclear reactors is presented. Basically, the structure comprises two coaxial graphite sleeves integrally joined together by radial fins. Due to the high structural strength of graphite at high temperatures and the rigidity of this structure, nuclear fuel encased within the inner sleeve in contiguous relation therewith is supported and prevented from expanding radially at high temperatures. Thus, the necessity of relying on the usual cladding materials with relatively low temperature limitations for structural strength is removed. (AEC)

High-temperature Chemical Compatibility of As-fabricated TRIGA Fuel and Type 304 Stainless Steel Cladding

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dennis D. Keiser, Jr.; Jan-Fong Jue; Eric Woolstenhulme

2012-09-01

Chemical interaction between TRIGA fuel and Type-304 stainless steel cladding at relatively high temperatures is of interest from the point of view of understanding fuel behavior during different TRIGA reactor transient scenarios. Since TRIGA fuel comes into close contact with the cladding during irradiation, there is an opportunity for interdiffusion between the U in the fuel and the Fe in the cladding to form an interaction zone that contains U-Fe phases. Based on the equilibrium U-Fe phase diagram, a eutectic can develop at a composition between the U6Fe and UFe2 phases. This eutectic composition can become a liquid at aroundmore » 725°C. From the standpoint of safe operation of TRIGA fuel, it is of interest to develop better understanding of how a phase with this composition may develop in irradiated TRIGA fuel at relatively high temperatures. One technique for investigating the development of a eutectic phase at the fuel/cladding interface is to perform out-of-pile diffusion-couple experiments at relatively high temperatures. This information is most relevant for lightly irradiated fuel that just starts to touch the cladding due to fuel swelling. Similar testing using fuel irradiated to different fission densities should be tested in a similar fashion to generate data more relevant to more heavily irradiated fuel. This report describes the results for TRIGA fuel/Type-304 stainless steel diffusion couples that were annealed for one hour at 730 and 800°C. Scanning electron microscopy with energy- and wavelength-dispersive spectroscopy was employed to characterize the fuel/cladding interface for each diffusion couple to look for evidence of any chemical interaction. Overall, negligible fuel/cladding interaction was observed for each diffusion couple.« less

Method for producing electricity from a fuel cell having solid-oxide ionic electrolyte

DOEpatents

Mason, David M.

1984-01-01

Stabilized quadrivalent cation oxide electrolytes are employed in fuel cells at elevated temperatures with a carbon and/or hydrogen containing fuel anode and an oxygen cathode. The fuel cell is operated at elevated temperatures with conductive metallic coatings as electrodes and desirably having the electrolyte surface blackened. Of particular interest as the quadrivalent oxide is zirconia.

Growth, partitioning, and nutrient and carbohydrate concentration of Petunia x hybrid Vilm. are influenced by altering light, CO2, and fertility

USDA-ARS?s Scientific Manuscript database

Fuel prices have fluctuated wildly in the last several years, and faced with unpredictable or rising fuel costs, growers often lower temperature set points to decrease fuel use. However, plant growth and development are influenced by lower temperatures and may cause increases in fuel use due to lon...

Tailoring gadolinium-doped ceria-based solid oxide fuel cells to achieve 2 W cm(-2) at 550 °C.

PubMed

Lee, Jin Goo; Park, Jeong Ho; Shul, Yong Gun

2014-06-04

Low-temperature operation is necessary for next-generation solid oxide fuel cells due to the wide variety of their applications. However, significant increases in the fuel cell losses appear in the low-temperature solid oxide fuel cells, which reduce the cell performance. To overcome this problem, here we report Gd0.1Ce0.9O1.95-based low-temperature solid oxide fuel cells with nanocomposite anode functional layers, thin electrolytes and core/shell fibre-structured Ba0.5Sr0.5Co0.8Fe0.2O3-δ-Gd0.1Ce0.9O1.95 cathodes. In particular, the report describes the use of the advanced electrospinning and Pechini process in the preparation of the core/shell-fibre-structured cathodes. The fuel cells show a very high performance of 2 W cm(-2) at 550 °C in hydrogen, and are stable for 300 h even under the high current density of 1 A cm(-2). Hence, the results suggest that stable and high-performance solid oxide fuel cells at low temperatures can be achieved by modifying the microstructures of solid oxide fuel cell components.

Fuel-rich catalytic combustion: A fuel processor for high-speed propulsion

NASA Technical Reports Server (NTRS)

Brabbs, Theodore A.; Rollbuhler, R. James; Lezberg, Erwin A.

1990-01-01

Fuel-rich catalytic combustion of Jet-A fuel was studied over the equivalence ratio range 4.7 to 7.8, which yielded combustion temperatures of 1250 to 1060 K. The process was soot-free and the gaseous products were similar to those obtained in the iso-octane study. A carbon atom balance across the catalyst bed calculated for the gaseous products accounted for about 70 to 90 percent of the fuel carbon; the balance was condensed as a liquid in the cold trap. It was shown that 52 to 77 percent of the fuel carbon was C1, C2, and C3 molecules. The viability of using fuel-rich catalytic combustion as a technique for preheating a practical fuel to very high temperatures was demonstrated. Preliminary results from the scaled up version of the catalytic combustor produced a high-temperature fuel containing large amounts of hydrogen and carbon monoxide. The balance of the fuel was completely vaporized and in various stages of pyrolysis and oxidation. Visual observations indicate that there was no soot present.

Application of the two-film model to the volatilization of acetone and t-butyl alcohol from water as a function of temperature

USGS Publications Warehouse

Rathbun, R.E.; Tai, D.Y.

1988-01-01

The two-film model is often used to describe the volatilization of organic substances from water. This model assumes uniformly mixed water and air phases separated by thin films of water and air in which mass transfer is by molecular diffusion. Mass-transfer coefficients for the films, commonly called film coefficients, are related through the Henry's law constant and the model equation to the overall mass-transfer coefficient for volatilization. The films are modeled as two resistances in series, resulting in additive resistances. The two-film model and the concept of additivity of resistances were applied to experimental data for acetone and t-butyl alcohol. Overall mass-transfer coefficients for the volatilization of acetone and t-butyl alcohol from water were measured in the laboratory in a stirred constant-temperature bath. Measurements were completed for six water temperatures, each at three water mixing conditions. Wind-speed was constant at about 0.1 meter per second for all experiments. Oxygen absorption coefficients were measured simultaneously with the measurement of the acetone and t-butyl alcohol mass-transfer coefficients. Gas-film coefficients for acetone, t-butyl alcohol, and water were determined by measuring the volatilization fluxes of the pure substances over a range of temperatures. Henry's law constants were estimated from data from the literature. The combination of high resistance in the gas film for solutes with low values of the Henry's law constants has not been studied previously. Calculation of the liquid-film coefficients for acetone and t-butyl alcohol from measured overall mass-transfer and gas-film coefficients, estimated Henry's law constants, and the two-film model equation resulted in physically unrealistic, negative liquid-film coefficients for most of the experiments at the medium and high water mixing conditions. An analysis of the two-film model equation showed that when the percentage resistance in the gas film is large and the gas-film resistance approaches the overall resistance in value, the calculated liquid-film coefficient becomes extremely sensitive to errors in the Henry's law constant. The negative coefficients were attributed to this sensitivity and to errors in the estimated Henry's law constants. Liquid-film coefficients for the absorption of oxygen were correlated with the stirrer Reynolds number and the Schmidt number. Application of this correlation with the experimental conditions and a molecular-diffusion coefficient adjustment resulted in values of the liquid-film coefficients for both acetone and t-butyl alcohol within the range expected for all three mixing conditions. Comparison of Henry's law constants calculated from these film coefficients and the experimental data with the constants calculated from literature data showed that the differences were small relative to the errors reported in the literature as typical for the measurement or estimation of Henry's law constants for hydrophilic compounds such as ketones and alcohols. Temperature dependence of the mass-transfer coefficients was expressed in two forms. The first, based on thermodynamics, assumed the coefficients varied as the exponential of the reciprocal absolute temperature. The second empirical approach assumed the coefficients varied as the exponential of the absolute temperature. Both of these forms predicted the temperature dependence of the experimental mass-transfer coefficients with little error for most of the water temperature range likely to be found in streams and rivers. Liquid-film and gas-film coefficients for acetone and t-butyl alcohol were similar in value. However, depending on water mixing conditions, overall mass-transfer coefficients for acetone were from two to four times larger than the coefficients for t-butyl alcohol. This difference in behavior of the coefficients resulted because the Henry's law constant for acetone was about three times larger than that of

Gas-film coefficients for the volatilization of ethylene dibromide from water

USGS Publications Warehouse

Rathbun, R.E.; Tal, D.Y.

1986-01-01

Gas-film coefficients for the volatilization of ethylene dibromide (EDB) and water were determined in the laboratory as a function of wind speed and temperature. The ratio of the coefficients was independent of wind speed and increased slightly with temperature. Use of this ratio with an environmentally determined gas-film coefficient for the evaporation of water permits determination of the gas-film coefficient for the volatilization of EDB from environmental waters.

Development of Polybenzimidazole-Based High-Temperature Membrane and Electrode Assemblies for Stationary and Automotive Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vogel, John A.

The program began on August 1, 2003 and ended on July 31, 2007. The goal of the project was to optimize a high-temperature polybenzimidazole (PBI) membrane to meet the performance, durability, and cost targets required for stationary fuel cell applications. These targets were identified in the Fuel Cell section (3.4) of DOE’s Hydrogen, Fuel Cells and Infrastructure Technologies Program Multi-Year Research, Development and Demonstration Plan. A membrane that operates at high temperatures is important to the fuel cell industry because it is insensitive to carbon monoxide (a poison to low-temperature fuel cells), and does not require complex water management strategies.more » Together, these two benefits greatly simplify the fuel cell system. As a result, the high-temperature fuel cell system realizes a cost benefit as the number of components is reduced by nearly 30%. There is also an inherent reliability benefit as components such as humidifiers and pumps for water management are unnecessary. Furthermore, combined heat and power (CHP) systems may be the best solution for a commercial, grid-connected, stationary product that must offer a cost benefit to the end user. For a low-temperature system, the quality of the heat supplied is insufficient to meet consumer needs and comfort requirements, so peak heaters or supplemental boilers are required. The higher operating temperature of PBI technology allows the fuel cell to meet the heat and comfort demand without the additional equipment. Plug Power, working with the Rensselaer Polytechnic Institute (RPI) Polymer Science Laboratory, made significant advances in optimizing the PBI membrane material for operation at temperatures greater than 160oC with a lifetime of 40,000 hours. Supporting hardware such as flow field plates and a novel sealing concept were explored to yield the lower-cost stack assembly and corresponding manufacturing process. Additional work was conducted on acid loss, flow field design and cathode electrode development. Membranes and MEAs were supplied by team member BASF Fuel Cell (formerly PEMEAS), a manufacturer of polymer and fiber. Additional subcontractors Entegris, the University of South Carolina (USC) Fuel Cell Center, and RPI’s Fuel Cell Center conducted activities with regard to stack sealing, acid modeling, and electrode development.« less

Modeling the UO2 ex-AUC pellet process and predicting the fuel rod temperature distribution under steady-state operating condition

NASA Astrophysics Data System (ADS)

Hung, Nguyen Trong; Thuan, Le Ba; Thanh, Tran Chi; Nhuan, Hoang; Khoai, Do Van; Tung, Nguyen Van; Lee, Jin-Young; Jyothi, Rajesh Kumar

2018-06-01

Modeling uranium dioxide pellet process from ammonium uranyl carbonate - derived uranium dioxide powder (UO2 ex-AUC powder) and predicting fuel rod temperature distribution were reported in the paper. Response surface methodology (RSM) and FRAPCON-4.0 code were used to model the process and to predict the fuel rod temperature under steady-state operating condition. Fuel rod design of AP-1000 designed by Westinghouse Electric Corporation, in these the pellet fabrication parameters are from the study, were input data for the code. The predictive data were suggested the relationship between the fabrication parameters of UO2 pellets and their temperature image in nuclear reactor.

Thermal stability of some aircraft turbine fuels derived from oil shale and coal

NASA Technical Reports Server (NTRS)

Reynolds, T. W.

1977-01-01

Thermal stability breakpoint temperatures are shown for 32 jet fuels prepared from oil shale and coal syncrudes by various degrees of hydrogenation. Low severity hydrotreated shale oils, with nitrogen contents of 0.1 to 0.24 weight percent, had breakpoint temperatures in the 477 to 505 K (400 to 450 F) range. Higher severity treatment, lowering nitrogen levels to 0.008 to 0.017 weight percent, resulted in breakpoint temperatures in the 505 to 533 K (450 to 500 F) range. Coal derived fuels showed generally increasing breakpoint temperatures with increasing weight percent hydrogen, fuels below 13 weight percent hydrogen having breakpoints below 533 K (500 F). Comparisons are shown with similar literature data.

Refractive indices at visible wavelengths of soot emitted from buoyant turbulent diffusion flames

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, J.S.; Krishnan, S.K.; Faeth, G.M.

1996-11-01

Measurements of the optical properties of soot, emphasizing refractive indices, are reported for visible wavelengths. The experiments considered soot in the fuel-lean (overfire) region of buoyant turbulent diffusion flames in the long residence time regime where soot properties are independent of position in the overfire region and residence time. Flames fueled with acetylene, propylene, ethylene and propane burning in still air provided a range of soot physical and structure properties. Measurements included soot composition, density, structure, gravimetric volume fraction, scattering properties and absorption properties. These data were analyzed to find soot fractal dimensions, refractive indices and dimensionless extinction coefficients, assumingmore » Rayleigh-Debye-Gans scattering for polydisperse mass fractal aggregates (RDG-PFA theory). RDG-PFA theory was successfully evaluated, based on measured scattering patterns. Soot fractal dimensions were independent of both fuel type and wavelength, yielding a mean value of 1.77 with a standard deviation of 0.04. Refractive indices were independent of fuel type within experimental uncertainties and were in reasonably good agreement with earlier measurements for soot in the fuel-lean region of diffusion flames due to Dalzell and Sarofim (1969). Dimensionless extinction coefficients were independent of both fuel type and wavelength, yielding a mean value of 5.1 with a standard deviation of 0.5, which is lower than earlier measurements for reasons that still must be explained.« less

Effect of fuel vapor concentrations on combustor emissions and performance

NASA Technical Reports Server (NTRS)

Norgren, C. T.; Ingebo, R. D.

1973-01-01

Effects of fuel vaporization on the exhaust emission levels of oxides of nitrogen, carbon monoxide, total hydrocarbons, and smoke number were obtained in an experimental turbojet combustor segment. Two different fuel injectors were used in which liquid ASTM A-1 jet fuel and vapor propane fuel were independently controlled to simulate varying degrees of vaporization. Tests were conducted over a range of inlet-air temperatures from 478 to 700 K, pressures from 4 to 20 atm, and combustor reference velocities from 15.3 to 27.4 m/sec. Converting from liquid to complete vapor fuel resulted in oxides of nitrogen reductions of as much as 22 percent and smoke number reductions up to 51 percent. Supplement data are also presented on flame emissivity, flame temperature, and primary-zone liner wall temperatures.

State Relationships of Laminar Permanently-Blue Opposed-Jet Hydrocarbon-Fueled Diffusion Flames. Appendix D

NASA Technical Reports Server (NTRS)

Lin, K.-C.; Faeth, G. M.; Urban, D. L. (Technical Monitor)

2000-01-01

The structure and state relationships of laminar soot-free (permanently-blue) diffusion flames at various strain rates were studied experimentally using an opposed-jet configuration, motivated by the importance of soot-free hydrocarbon-fueled diffusion flames for many practical applications. Measurements of gas velocities, temperatures and compositions were carried out along the stagnation stream line. Flame conditions studied included propylene- and 1,3-butadiene-fueled opposed-jet diffusion flames having a stoichiometric mixture fractions of 0.7 and strain rates of 60-240 s (exp -1) at normal temperature and pressure. It was found that oxygen leakage to fuel-rich conditions and carbon monoxide leakage to fuel-lean conditions both increased as strain rates increased. Furthermore, increased strain rates caused increased fuel concentrations near the flame sheet, decreased peak gas temperatures, and decreased concentrations of carbon dioxide and water vapor throughout the flames. State relationships for major gas species and gas temperatures for these flames were found to exist over broad ranges of strain rates. In addition, current measurements, as well as previous measurements and predictions of ethylene-fueled permanently-blue diffusion flames, all having a stoichiometric mixture fraction of 0.7, were combined to establish generalized state relationships for permanently-blue diffusion flames for this stoichiometric mixture fraction. The combined measurements and predictions support relatively universal generalized state relationships for N2, CO2, H2O and fuel over a broad range of strain rates and fuel types. State relationships for O2 in the fuel-rich region, and for CO in the fuel-lean region, however, are functions of strain rate and fuel type. State relationships for H2 and temperature exhibit less universality, mainly due to the increased experimental uncertainties for these variables. The existence of state relationships for soot-free hydrocarbon-fueled diffusion flames provides potential for significant computational simplifications for modeling purposes in many instances, allowing for effects of finite-rate chemistry while avoiding time-consuming computations of Arrhenius expressions.

Fuel Maps for the GEP 6.5LT Engine When Operating on at J/JP-8 Fuel Blends at Ambient and Elevated Temperatures

DTIC Science & Technology

2015-04-01

system. The new calibrated fuel injection pump and injectors were installed, and the fuel injection timing of the new fuel injection system was set to...Product 6.5L Turbocharged diesel engine at two inlet temperature conditions. The GEP 6.5LT engine represents legacy diesel engine design with...derived cetane number DF-2 Diesel Fuel number 2 ft Foot HEFA Hydro-treated Esters and Fatty Acid(s) HP or hp Horsepower hr Hour in Inch in³ cubic

Defining the Operational Conditions for High Temperature Polymer Fuel Cells in Naval Environments

DTIC Science & Technology

2008-12-31

benefits of both Proton Exchange Membrane Fuel Cells ( PEMFCs ) and phosphoric acid fuel cell technologies: a solid polymer electrolyte, the PBI...membrane, but with higher temperature (160°C) operation. PBI membrane technology is far less developed than that for PEMFCs , but it is rapidly emerging as...how air contaminants affect the properties of proton exchange membrane fuel cells ( PEMFCs ). PEMFCs operate at 80 °C, and are the present choice of fuel

RP-1 and JP-8 Thermal Stability Experiments

NASA Technical Reports Server (NTRS)

Brown, Sarah P.; Emens, Jessica M.; Frederick, Robert A., Jr.

2005-01-01

This work experimentally investigates the effect of fuel composition changes on jet and rocket fuel thermal stability. A High Reynolds Number Thermal Stability test device evaluated JP-8 and RP-1 fuels. The experiment consisted of an electrically heated, stainless steel capillary tube with a controlled fuel outlet temperature. An optical pyrometer monitored the increasing external temperature profiles of the capillary tube as deposits build inside during each test. Multiple runs of each fuel composition provided results on measurement repeatability. Testing a t two different facilities provided data on measurement reproducibility. The technique is able to distinguish between thermally stable and unstable compositions of JP-8 and intermediate blends made by combining each composition. The technique is also able to distinguish among standard RP-1 rocket fuels and those having reduced sulfur levels. Carbon burn off analysis of residue in the capillary tubes on the RP-1 fuels correlates with the external temperature results.

Analytical fuel property effects: Small combustors, phase 2

NASA Technical Reports Server (NTRS)

Hill, T. G.; Monty, J. D.; Morton, H. L.

1985-01-01

The effects of non-standard aviation fuels on a typical small gas turbine combustor were studied and the effectiveness of design changes intended to counter the effects of these fuels was evaluated. The T700/CT7 turboprop engine family was chosen as being representative of the class of aircraft power plants desired for this study. Fuel properties, as specified by NASA, are characterized by low hydrogen content and high aromatics levels. No. 2 diesel fuel was also evaluated in this program. Results demonstrated the anticipated higher than normal smoke output and flame radiation intensity with resulting increased metal temperatures on the baseline T700 combustor. Three new designs were evaluated using the non standard fuels. The three designs incorporated enhanced cooling features and smoke reduction features. All three designs, when burning the broad specification fuels, exhibited metal temperatures at or below the baseline combustor temperatures on JP-5. Smoke levels were acceptable but higher than predicted.

Ultra-lean combustion at high inlet temperatures

NASA Technical Reports Server (NTRS)

Anderson, D. N.

1981-01-01

Combustion at inlet air temperatures of 1100 to 1250 K was studied for application to advanced automotive gas turbine engines. Combustion was initiated by the hot environment, and therefore no external ignition source was used. Combustion was stabilized without a flameholder. The tests were performed in a 12 cm diameter test section at a pressure of 2.5 x 10 to the 5th power Pa, with reference velocities of 32 to 60 m/sec and at maximum combustion temperatures of 1350 to 1850 K. Number 2 diesel fuel was injected by means of a multiple source fuel injector. Unburned hydrocarbons emissions were negligible for all test conditions. Nitrogen oxides emissions were less than 1.9 g NO2/kg fuel for combustion temperatures below 1680 K. Carbon monoxide emissions were less than 16 g CO/kg fuel for combustion temperatures greater than 1600 K, inlet air temperatures higher than 1150 K, and residence times greater than 4.3 microseconds.

Verification of combined thermal-hydraulic and heat conduction analysis code FLOWNET/TRUMP

NASA Astrophysics Data System (ADS)

Maruyama, Soh; Fujimoto, Nozomu; Kiso, Yoshihiro; Murakami, Tomoyuki; Sudo, Yukio

1988-09-01

This report presents the verification results of the combined thermal-hydraulic and heat conduction analysis code, FLOWNET/TRUMP which has been utilized for the core thermal hydraulic design, especially for the analysis of flow distribution among fuel block coolant channels, the determination of thermal boundary conditions for fuel block stress analysis and the estimation of fuel temperature in the case of fuel block coolant channel blockage accident in the design of the High Temperature Engineering Test Reactor(HTTR), which the Japan Atomic Energy Research Institute has been planning to construct in order to establish basic technologies for future advanced very high temperature gas-cooled reactors and to be served as an irradiation test reactor for promotion of innovative high temperature new frontier technologies. The verification of the code was done through the comparison between the analytical results and experimental results of the Helium Engineering Demonstration Loop Multi-channel Test Section(HENDEL T(sub 1-M)) with simulated fuel rods and fuel blocks.

FRAPCON analysis of cladding performance during dry storage operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richmond, David J.; Geelhood, Kenneth J.

There is an increasing need in the U.S. and around the world to move used nuclear fuel from wet storage in fuel pools to dry storage in casks stored at independent spent fuel storage installations (ISFSI) or interim storage sites. The NRC limits cladding temperature to 400°C while maintaining cladding hoop stress below 90 MPa in an effort to avoid radial hydride reorientation. An analysis was conducted with FRAPCON-4.0 on three modern fuel designs with three representative used nuclear fuel storage temperature profiles that peaked at 400 °C. Results were representative of the majority of U.S. LWR fuel. They conservativelymore » showed that hoop stress remains below 90 MPa at the licensing temperature limit. Results also show that the limiting case for hoop stress may not be at the highest rod internal pressure in all cases but will be related to the axial temperature and oxidation profiles of the rods at the end of life and in storage.« less

Effects of broadened property fuels on radiant heat flux to gas turbine combustor liners

NASA Technical Reports Server (NTRS)

Haggard, J. B., Jr.

1983-01-01

The effects of fuel type, inlet air pressure, inlet air temperature, and fuel/air ratio on the combustor radiation were investigated. Combustor liner radiant heat flux measurements were made in the spectral region between 0.14 and 6.5 microns at three locations in a modified commercial aviation can combustor. Two fuels, Jet A and a heavier distillate research fuel called ERBS were used. The use of ERBS fuel as opposed to Jet A under similar operating conditions resulted in increased radiation to the combustor liner and hence increased backside liner temperature. This increased radiation resulted in liner temperature increases always less than 73 C. The increased radiation is shown by way of calculations to be the result of increased soot concentrations in the combustor. The increased liner temperatures indicated can substantially affect engine maintenance costs by reducing combustor liner life up to 1/3 because of the rapid decay in liner material properties when operated beyond their design conditions.

Conjugate Heat Transfer Analyses on the Manifold for Ramjet Fuel Injectors

NASA Technical Reports Server (NTRS)

Wang, Xiao-Yen J.

2006-01-01

Three-dimensional conjugate heat transfer analyses on the manifold located upstream of the ramjet fuel injector are performed using CFdesign, a finite-element computational fluid dynamics (CFD) software. The flow field of the hot fuel (JP-7) flowing through the manifold is simulated and the wall temperature of the manifold is computed. The three-dimensional numerical results of the fuel temperature are compared with those obtained using a one-dimensional analysis based on empirical equations, and they showed a good agreement. The numerical results revealed that it takes around 30 to 40 sec to reach the equilibrium where the fuel temperature has dropped about 3 F from the inlet to the exit of the manifold.

Temperature Profile in Fuel and Tie-Tubes for Nuclear Thermal Propulsion Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vishal Patel

A finite element method to calculate temperature profiles in heterogeneous geometries of tie-tube moderated LEU nuclear thermal propulsion systems and HEU designs with tie-tubes is developed and implemented in MATLAB. This new method is compared to previous methods to demonstrate shortcomings in those methods. Typical methods to analyze peak fuel centerline temperature in hexagonal geometries rely on spatial homogenization to derive an analytical expression. These methods are not applicable to cores with tie-tube elements because conduction to tie-tubes cannot be accurately modeled with the homogenized models. The fuel centerline temperature directly impacts safety and performance so it must be predictedmore » carefully. The temperature profile in tie-tubes is also important when high temperatures are expected in the fuel because conduction to the tie-tubes may cause melting in tie-tubes, which may set maximum allowable performance. Estimations of maximum tie-tube temperature can be found from equivalent tube methods, however this method tends to be approximate and overly conservative. A finite element model of heat conduction on a unit cell can model spatial dependence and non-linear conductivity for fuel and tie-tube systems allowing for higher design fidelity of Nuclear Thermal Propulsion.« less

High temperature two component explosive

DOEpatents

Mars, James E.; Poole, Donald R.; Schmidt, Eckart W.; Wang, Charles

1981-01-01

A two component, high temperature, thermally stable explosive composition comprises a liquid or low melting oxidizer and a liquid or low melting organic fuel. The oxidizer and fuel in admixture are incapable of substantial spontaneous exothermic reaction at temperatures on the order of 475.degree. K. At temperatures on the order of 475.degree. K., the oxidizer and fuel in admixture have an activation energy of at least about 40 kcal/mol. As a result of the high activation energy, the preferred explosive compositions are nondetonable as solids at ambient temperature, and become detonable only when heated beyond the melting point. Preferable oxidizers are selected from alkali or alkaline earth metal nitrates, nitrites, perchlorates, and/or mixtures thereof. Preferred fuels are organic compounds having polar hydrophilic groups. The most preferred fuels are guanidinium nitrate, acetamide and mixtures of the two. Most preferred oxidizers are eutectic mixtures of lithium nitrate, potassium nitrate and sodium nitrate, of sodium nitrite, sodium nitrate and potassium nitrate, and of potassium nitrate, calcium nitrate and sodium nitrate.

Process Developed for Generating Ceramic Interconnects With Low Sintering Temperatures for Solid Oxide Fuel Cells

NASA Technical Reports Server (NTRS)

Zhong, Zhi-Min; Goldsby, Jon C.

2005-01-01

Solid oxide fuel cells (SOFCs) have been considered as premium future power generation devices because they have demonstrated high energy-conversion efficiency, high power density, and extremely low pollution, and have the flexibility of using hydrocarbon fuel. The Solid-State Energy Conversion Alliance (SECA) initiative, supported by the U.S. Department of Energy and private industries, is leading the development and commercialization of SOFCs for low-cost stationary and automotive markets. The targeted power density for the initiative is rather low, so that the SECA SOFC can be operated at a relatively low temperature (approx. 700 C) and inexpensive metallic interconnects can be utilized in the SOFC stack. As only NASA can, the agency is investigating SOFCs for aerospace applications. Considerable high power density is required for the applications. As a result, the NASA SOFC will be operated at a high temperature (approx. 900 C) and ceramic interconnects will be employed. Lanthanum chromite-based materials have emerged as a leading candidate for the ceramic interconnects. The interconnects are expected to co-sinter with zirconia electrolyte to mitigate the interface electric resistance and to simplify the processing procedure. Lanthanum chromites made by the traditional method are sintered at 1500 C or above. They react with zirconia electrolytes (which typically sinter between 1300 and 1400 C) at the sintering temperature of lanthanum chromites. It has been envisioned that lanthanum chromites with lower sintering temperatures can be co-fired with zirconia electrolyte. Nonstoichiometric lanthanum chromites can be sintered at lower temperatures, but they are unstable and react with zirconia electrolyte during co-sintering. NASA Glenn Research Center s Ceramics Branch investigated a glycine nitrate process to generate fine powder of the lanthanum-chromite-based materials. By simultaneously doping calcium on the lanthanum site, and cobalt and aluminum on the chromium site, we could sinter the materials below 1400 C. The doping concentrations were adjusted so that the thermal expansion coefficient matched that of the zirconia electrolyte. Also, the investigation was focused on stoichiometric compositions so that the materials would have better stability. Co-sintering and chemical compatibility with zirconia electrolyte were examined by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (line scanning and dot map). The results showed that the materials bond well, but do not react, with zirconia electrolyte. The electric conductivity of the materials measured at 900 C in air was about 20 S/cm.

Measurements of Heat-Transfer and Friction Coefficients for Helium Flowing in a Tube at Surface Temperatures up to 5900 Deg R

NASA Technical Reports Server (NTRS)

Taylor, Maynard F.; Kirchgessner, Thomas A.

1959-01-01

Measurements of average heat transfer and friction coefficients and local heat transfer coefficients were made with helium flowing through electrically heated smooth tubes with length-diameter ratios of 60 and 92 for the following range of conditions: Average surface temperature from 1457 to 4533 R, Reynolds numbe r from 3230 to 60,000, heat flux up to 583,200 Btu per hr per ft2 of heat transfer area, and exit Mach numbe r up to 1.0. The results indicate that, in the turbulent range of Reynolds number, good correlation of the local heat transfer coefficients is obtained when the physical properties and density of helium are evaluated at the surface temperature. The average heat transfer coefficients are best correlated on the basis that the coefficient varies with [1 + (L/D))(sup -0,7)] and that the physical properties and density are evaluated at the surface temperature. The average friction coefficients for the tests with no heat addition are in complete agreement with the Karman-Nikuradse line. The average friction coefficients for heat addition are in poor agreement with the accepted line.

Blister Threshold Based Thermal Limits for the U-Mo Monolithic Fuel System

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. M. Wachs; I. Glagolenko; F. J. Rice

2012-10-01

Fuel failure is most commonly induced in research and test reactor fuel elements by exposure to an under-cooled or over-power condition that results in the fuel temperature exceeding a critical threshold above which blisters form on the plate. These conditions can be triggered by normal operational transients (i.e. temperature overshoots that may occur during reactor startup or power shifts) or mild upset events (e.g., pump coastdown, small blockages, mis-loading of fuel elements into higher-than-planned power positions, etc.). The rise in temperature has a number of general impacts on the state of a fuel plate that include, for example, stress relaxationmore » in the cladding (due to differential thermal expansion), softening of the cladding, increased mobility of fission gases, and increased fission-gas pressure in pores, all of which can encourage the formation of blisters on the fuel-plate surface. These blisters consist of raised regions on the surface of fuel plates that occur when the cladding plastically deforms in response to fission-gas pressure in large pores in the fuel meat and/or mechanical buckling of the cladding over damaged regions in the fuel meat. The blister temperature threshold decreases with irradiation because the mechanical properties of the fuel plate degrade while under irradiation (due to irradiation damage and fission-product accumulation) and because the fission-gas inventory progressively increases (and, thus, so does the gas pressure in pores).« less

Butanol / Gasoline Mercury CRADA Report

DTIC Science & Technology

2015-03-01

oxygenated fuel, which increases in-cylinder temperatures and thus generates higher NOx emissions. 3.2 Modifications to the SPC-TB 3.2.1 Data Collection...emissions.  Emissions of oxides of Nitrogen (NOx) are higher with oxygenated fuel. NOx generation is a function of the time spent at high temperature ...pressure in the combustion chamber. The engines run leaner and hotter with oxygenated fuel, which increases in-cylinder temperatures and thus

Thermodynamic Modeling of a Solid Oxide Fuel Cell to Couple with an Existing Gas Turbine Engine Model

NASA Technical Reports Server (NTRS)

Brinson, Thomas E.; Kopasakis, George

2004-01-01

The Controls and Dynamics Technology Branch at NASA Glenn Research Center are interested in combining a solid oxide fuel cell (SOFC) to operate in conjunction with a gas turbine engine. A detailed engine model currently exists in the Matlab/Simulink environment. The idea is to incorporate a SOFC model within the turbine engine simulation and observe the hybrid system's performance. The fuel cell will be heated to its appropriate operating condition by the engine s combustor. Once the fuel cell is operating at its steady-state temperature, the gas burner will back down slowly until the engine is fully operating on the hot gases exhausted from the SOFC. The SOFC code is based on a steady-state model developed by The U.S. Department of Energy (DOE). In its current form, the DOE SOFC model exists in Microsoft Excel and uses Visual Basics to create an I-V (current-voltage) profile. For the project's application, the main issue with this model is that the gas path flow and fuel flow temperatures are used as input parameters instead of outputs. The objective is to create a SOFC model based on the DOE model that inputs the fuel cells flow rates and outputs temperature of the flow streams; therefore, creating a temperature profile as a function of fuel flow rate. This will be done by applying the First Law of Thermodynamics for a flow system to the fuel cell. Validation of this model will be done in two procedures. First, for a given flow rate the exit stream temperature will be calculated and compared to DOE SOFC temperature as a point comparison. Next, an I-V curve and temperature curve will be generated where the I-V curve will be compared with the DOE SOFC I-V curve. Matching I-V curves will suggest validation of the temperature curve because voltage is a function of temperature. Once the temperature profile is created and validated, the model will then be placed into the turbine engine simulation for system analysis.

Assessment of langatate material constants and temperature coefficients using SAW delay line measurements.

PubMed

Sturtevant, Blake T; Pereira da Cunha, Mauricio

2010-03-01

This paper reports on the assessment of langatate (LGT) acoustic material constants and temperature coefficients by surface acoustic wave (SAW) delay line measurements up to 130 degrees C. Based upon a full set of material constants recently reported by the authors, 7 orientations in the LGT plane with Euler angles (90 degrees, 23 degrees, Psi) were identified for testing. Each of the 7 selected orientations exhibited calculated coupling coefficients (K(2)) between 0.2% and 0.75% and also showed a large range of predicted temperature coefficient of delay (TCD) values around room temperature. Additionally, methods for estimating the uncertainty in predicted SAW propagation properties were developed and applied to SAW phase velocity and temperature coefficient of delay calculations. Starting from a purchased LGT boule, the SAW wafers used in this work were aligned, cut, ground, and polished at University of Maine facilities, followed by device fabrication and testing. Using repeated measurements of 2 devices on separate wafers for each of the 7 orientations, the room temperature SAW phase velocities were extracted with a precision of 0.1% and found to be in agreement with the predicted values. The normalized frequency change and the temperature coefficient of delay for all 7 orientations agreed with predictions within the uncertainty of the measurement and the predictions over the entire 120 degrees C temperature range measured. Two orientations, with Euler angles (90 degrees, 23 degrees, 123 degrees) and (90 degrees, 23 degrees, 119 degrees), were found to have high predicted coupling for LGT (K(2) > 0.5%) and were shown experimentally to exhibit temperature compensation in the vicinity of room temperature, with turnover temperatures at 50 and 60 degrees C, respectively.

40 CFR 600.113-08 - Fuel economy calculations for FTP, HFET, US06, SC03 and cold temperature FTP tests.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Fuel economy calculations for FTP, HFET, US06, SC03 and cold temperature FTP tests. 600.113-08 Section 600.113-08 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) ENERGY POLICY FUEL ECONOMY AND CARBON-RELATED EXHAUST EMISSIONS OF MOTOR VEHICLES Fuel Economy...

40 CFR 600.113-08 - Fuel economy calculations for FTP, HFET, US06, SC03 and cold temperature FTP tests.

Code of Federal Regulations, 2013 CFR

2013-07-01

... EMISSIONS OF MOTOR VEHICLES Fuel Economy and Carbon-Related Exhaust Emission Test Procedures § 600.113-08 Fuel economy calculations for FTP, HFET, US06, SC03 and cold temperature FTP tests. The Administrator... specific gravity, carbon weight fraction and net heating value of the test fuel must be determined. The FTP...

Laboratory demonstration and field verification of a Wireless Cookstove Sensing System (WiCS) for determining cooking duration and fuel consumption

DOE PAGES

Graham, Eric A.; Patange, Omkar; Lukac, Martin; ...

2014-08-27

With improved cookstoves (ICs) increasingly distributed to households for a range of air pollution interventions and carbon-credit programs, it has become necessary to accurately monitor the duration of cooking and the amount of fuel consumed. In this study, laboratory trials were used to create temperature-based algorithms for quantifying cooking duration and estimating fuel consumption from stove temperatures. Field validation of the algorithms employed a Wireless Cookstove Sensing System (WiCS) that offers remote, low-cost temperature sensing and the wireless transmission of temperature data to a centralized database using local cellular networks. Field trials included 68 unscripted household cooking events. In themore » laboratory, temperature responses of the IC body and that of a removable temperature probe (J-bar) followed well-known physical models during cooking, indicating that location of the temperature sensor is not critical. In the laboratory, the classification correctly identified active cooking 97.2% of the time. In the field, the cooking duration was not statistically different from that recorded by trained volunteers; the average difference between calculated and observed cooking times was 0.03 ± 0.31 h (mean ± SD). In the laboratory, energy flux from the IC was calculated using temperatures measured by the J-bar and on the IC body and found to be proportional to the total energy in the consumed fuel, with an r 2 correlation value of 0.95. Here in the field, the average fuel consumption was calculated to be 0.97 ± 0.32 kg compared to that recorded by volunteers of 1.19 ± 0.37 kg with an average difference between calculated and observed fuel mass of 0.21 ± 0.37 kg per event. Finally, despite wide variation in observed cooking duration and fuel consumption per event, a relatively constant rate of fuel consumption of 0.48 kg h -1 was calculated for users of the same type of IC.« less

THETRIS: A MICRO-SCALE TEMPERATURE AND GAS RELEASE MODEL FOR TRISO FUEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

J. Ortensi; A.M. Ougouag

2011-12-01

The dominating mechanism in the passive safety of gas-cooled, graphite-moderated, high-temperature reactors (HTRs) is the Doppler feedback effect. These reactor designs are fueled with sub-millimeter sized kernels formed into TRISO particles that are imbedded in a graphite matrix. The best spatial and temporal representation of the feedback effect is obtained from an accurate approximation of the fuel temperature. Most accident scenarios in HTRs are characterized by large time constants and slow changes in the fuel and moderator temperature fields. In these situations a meso-scale, pebble and compact scale, solution provides a good approximation of the fuel temperature. Micro-scale models aremore » necessary in order to obtain accurate predictions in faster transients or when parameters internal to the TRISO are needed. Since these coated particles constitute one of the fundamental design barriers for the release of fission products, it becomes important to understand the transient behavior inside this containment system. An explicit TRISO fuel temperature model named THETRIS has been developed and incorporated into the CYNOD-THERMIX-KONVEK suite of coupled codes. The code includes gas release models that provide a simple predictive capability of the internal pressure during transients. The new model yields similar results to those obtained with other micro-scale fuel models, but with the added capability to analyze gas release, internal pressure buildup, and effects of a gap in the TRISO. The analyses show the instances when the micro-scale models improve the predictions of the fuel temperature and Doppler feedback. In addition, a sensitivity study of the potential effects on the transient behavior of high-temperature reactors due to the presence of a gap is included. Although the formation of a gap occurs under special conditions, its consequences on the dynamic behavior of the reactor can cause unexpected responses during fast transients. Nevertheless, the strong Doppler feedback forces the reactor to quickly stabilize.« less

Characterization of a Heated Liquid Jet in Crossflow

NASA Astrophysics Data System (ADS)

Wiest, Heather K.

The liquid jet in crossflow (LJICF) is a widely utilized fuel injection method for airbreathing propulsion devices such as low NO x gas turbine combustors, turbojet afterburners, scramjet/ramjet engines, and rotating detonation engines (RDE's). This flow field allows for efficient fuel-air mixing as aerodynamic forces from the crossflow augment atomization. Additionally, increases in the thermal demands of advanced aeroengines necessitates the use of fuel as a primary coolant. The resulting higher fuel temperatures can cause flash atomization of the liquid fuel as it is injected into a crossflow, potentially leading to a large reduction in the jet penetration. While many experimental works have characterized the overall atomization process of a room temperature liquid jet in an ambient temperature and pressure crossflow, the aggressive conditions associated with flash atomization especially in an air crossflow with elevated temperatures and pressures have been less studied in the community. A successful test campaign was conducted to study the effects of fuel temperature on a liquid jet injected transversely into a steady air crossflow at ambient as well as elevated temperature and pressure conditions. Modifications were made to an existing optically accessible rig, and a new fuel injector was designed for this study. Backlit imaging was utilized to record changes in the overall spray characteristics and jet trajectory as fuel temperature and crossflow conditioners were adjusted. Three primary analysis techniques were applied to the heated LJICF data: linear regression of detected edges to determine trajectory correlations, exploratory study of pixel intensity variations both temporally as well as spatially, and modal decomposition of the data. The overall objectives of this study was to assess the trajectory, breakup, and mixing of the LJICF undery varying jet and crossflow conditions, develop a trajectory correlation to predict changes in jet penetration due to fuel temperature increases, and characterize the changes in underlying physics in the LJICF flow field. Based on visual inspection, the increase in fuel temperature leads to a finer and denser fuel spray. With increasingly elevated liquid temperatures, the penetration of the jet typically decreases. At or near flashing conditions, the jet had a tendency to penetrate upstream before bending over in the crossflow as well as experiences a rapid expansion causing the jet column to increase in width. Two trajectory correlations were determined, one for each set of crossflow conditions, based on normalized axial distance, normalized liquid viscosity, and normalized jet diameter as liquid is vaporized. The pixel intensity analysis showed that the highest temperature jet in the ambient temperature and pressure crossflow exhibited periodic behavior that was also found using various modal techniques including proper orthogonal decomposition and dynamic mode decomposition. Dominant frequencies determined for most test cases were associated with the bulk or flapping motion of the jet. Most notably, the DMD analysis in this study was successful in identifying robust modes across different subgroupings of the data even though the modes identified were not the highest power modes in each DMD spectrum.

Quantitative Analysis of Spectral Interference of Spontaneous Raman Scattering in High-Pressure Fuel-Rich H2-Air Combustion

NASA Technical Reports Server (NTRS)

Kojima, Jun; Nguyen, Quang-Viet

2004-01-01

We present a theoretical study of the spectral interferences in the spontaneous Raman scattering spectra of major combustion products in 30-atm fuel-rich hydrogen-air flames. An effective methodology is introduced to choose an appropriate line-shape model for simulating Raman spectra in high-pressure combustion environments. The Voigt profile with the additive approximation assumption was found to provide a reasonable model of the spectral line shape for the present analysis. The rotational/vibrational Raman spectra of H2, N2, and H2O were calculated using an anharmonic-oscillator model using the latest collisional broadening coefficients. The calculated spectra were validated with data obtained in a 10-atm fuel-rich H2-air flame and showed excellent agreement. Our quantitative spectral analysis for equivalence ratios ranging from 1.5 to 5.0 revealed substantial amounts of spectral cross-talk between the rotational H2 lines and the N2 O-/Q-branch; and between the vibrational H2O(0,3) line and the vibrational H2O spectrum. We also address the temperature dependence of the spectral cross-talk and extend our analysis to include a cross-talk compensation technique that removes the nterference arising from the H2 Raman spectra onto the N2, or H2O spectra.

Fuel cell membranes and crossover prevention

DOEpatents

Masel, Richard I [Champaign, IL; York, Cynthia A [Newington, CT; Waszczuk, Piotr [White Bear Lake, MN; Wieckowski, Andrzej [Champaign, IL

2009-08-04

A membrane electrode assembly for use with a direct organic fuel cell containing a formic acid fuel includes a solid polymer electrolyte having first and second surfaces, an anode on the first surface and a cathode on the second surface and electrically linked to the anode. The solid polymer electrolyte has a thickness t:.gtoreq..times..times..times..times. ##EQU00001## where C.sub.f is the formic acid fuel concentration over the anode, D.sub.f is the effective diffusivity of the fuel in the solid polymer electrolyte, K.sub.f is the equilibrium constant for partition coefficient for the fuel into the solid polymer electrolyte membrane, I is Faraday's constant n.sub.f is the number of electrons released when 1 molecule of the fuel is oxidized, and j.sub.f.sup.c is an empirically determined crossover rate of fuel above which the fuel cell does not operate.