Science.gov

Sample records for oxygen enhanced combustion

  1. OXYGEN ENHANCED COMBUSTION FOR NOx CONTROL

    SciTech Connect

    David R. Thompson; Lawrence E. Bool; Jack C. Chen

    2004-04-01

    Conventional wisdom says adding oxygen to a combustion system enhances product throughput, system efficiency, and, unless special care is taken, increases NOx emissions. This increase in NOx emissions is typically due to elevated flame temperatures associated with oxygen use leading to added thermal NOx formation. Innovative low flame temperature oxy-fuel burner designs have been developed and commercialized to minimize both thermal and fuel NOx formation for gas and oil fired industrial furnaces. To be effective these systems require close to 100% oxy-fuel combustion and the cost of oxygen is paid for by fuel savings and other benefits. For applications to coal-fired utility boilers at the current cost of oxygen, however, it is not economically feasible to use 100% oxygen for NOx control. In spite of this conventional wisdom, Praxair and its team members, in partnership with the US Department of Energy National Energy Technology Laboratory, have developed a novel way to use oxygen to reduce NOx emissions without resorting to complete oxy-fuel conversion. In this concept oxygen is added to the combustion process to enhance operation of a low NOx combustion system. Only a small fraction of combustion air is replaced with oxygen in the process. By selectively adding oxygen to a low NOx combustion system it is possible to reduce NOx emissions from nitrogen-containing fuels, including pulverized coal, while improving combustion characteristics such as unburned carbon. A combination of experimental work and modeling was used to define how well oxygen enhanced combustion could reduce NOx emissions. The results of this work suggest that small amounts of oxygen replacement can reduce the NOx emissions as compared to the air-alone system. NOx emissions significantly below 0.15 lbs/MMBtu were measured. Oxygen addition was also shown to reduce carbon in ash. Comparison of the costs of using oxygen for NOx control against competing technologies, such as SCR, show that this

  2. Enhancing SNCR-aided combustion with oxygen addition

    DOEpatents

    Kobayashi, Hisashi; Wu, Kuang Tsai; Bool, III, Lawrence E.

    2004-03-09

    NOx emissions from combustion are reduced, NOx reduction efficiency by SNCR is improved, and other efficiencies are realized, by injecting oxygen into a fuel-rich combustion zone under controlled conditions.

  3. Oxygen enhanced switching to combustion of lower rank fuels

    DOEpatents

    Kobayashi, Hisashi; Bool, III, Lawrence E.; Wu, Kuang Tsai

    2004-03-02

    A furnace that combusts fuel, such as coal, of a given minimum energy content to obtain a stated minimum amount of energy per unit of time is enabled to combust fuel having a lower energy content, while still obtaining at least the stated minimum energy generation rate, by replacing a small amount of the combustion air fed to the furnace by oxygen. The replacement of oxygen for combustion air also provides reduction in the generation of NOx.

  4. THE SITE DEMONSTRATION OF THE AMERICAN COMBUSTION PYRETRON OXYGEN-ENHANCED BURNER

    EPA Science Inventory

    A demonstration of the American Combustion PyretronTM oxygen-enhanced burner ws conducted under the Superfund Innovative Technology Evaluation (SITE) program. The Demonstration was conducted at the U.S. EPA's Combustion Research Facility (CRF) in Jefferson, Arkansas....

  5. Mult-Pollutant Control Through Novel Approaches to Oxygen Enhanced Combustion

    SciTech Connect

    Richard Axelbaum; Pratim Biswas

    2009-02-28

    Growing concerns about global climate change have focused effortss on identifying approaches to stabilizing carbon dioxide levels in the atmosphere. One approach utilizes oxy-fuel combustion to produce a concentrated flue gas that will enable economical CO{sub 2} capture by direct methods. Oxy-fuel combustion rewuires an Air Separation Unit (ASU) to provide a high-purity stream of oxygen as well as a Compression and Purification Unit (CPU) to clean and compress the CO{sub 2} for long term storage. Overall plant efficiency will suffer from the parasitic load of both the ASU and CPU and researchers are investigating techniques to enhance other aspects of the combustion and gas cleanup proceses to improve the benefit-to-cost ratio. This work examines the influence of oxy-fuel combustion and non-carbon based sorbents on the formation and fate of multiple combustion pollutants both numerically and experimentally.

  6. High-Efficiency, High-Capacity, Low-NOx Aluminum Melting Using Oxygen-Enhanced Combustion

    SciTech Connect

    D'Agostini, M.D.

    2000-06-02

    This report describes the development and application of a novel oxygen enhanced combustion system with an integrated vacuum swing adsorption (VSA) oxygen supply providing efficient, low NOx melting in secondary aluminum furnaces. The mainstay of the combustion system is a novel air-oxy-natural gas burner that achieves high productivity and energy efficiency with low NOx emissions through advanced mixing concepts and the use of separate high- and low-purity oxidizer streams. The technology was installed on a reverberatory, secondary aluminum melting plant at the Wabash Aluminum Alloy's Syracuse, N.Y. plant, where it is currently in operation. Field testing gave evidence that the new burner technology meets the stringent NOx emissions target of 0.323 lb NO2/ton aluminum, thus complying with regulations promulgated by Southern California's South Coast Air Quality Management District (SCAQMD). Test results also indicated that the burner technology exceeded fuel efficiency and melting capacity goals. Economic modeling showed that the novel air-oxy-fuel (ADF) combustion technology provides a substantial increase in furnace profitability relative to air-fuel operation. Model results also suggest favorable economics for the air-oxy-fuel technology relative to a full oxy-fuel conversion of the furnace.

  7. Hydrogen-oxygen powered internal combustion engine

    NASA Technical Reports Server (NTRS)

    Cameron, H.; Morgan, N.

    1970-01-01

    Hydrogen at 300 psi and oxygen at 800 psi are injected sequentially into the combustion chamber to form hydrogen-rich mixture. This mode of injection eliminates difficulties of preignition, detonation, etc., encountered with carburated, spark-ignited, hydrogen-air mixtures. Ignition at startup is by means of a palladium catalyst.

  8. [Fire by spontaneous combustion of oxygen cylinders].

    PubMed

    Coumans, Tanja; Maissan, Iscander M; Wolff, André P; Stolker, Robert Jan; Damen, Johan; Scheffer, Gert Jan

    2010-01-01

    The use of medicinal oxygen can be dangerous. The spontaneous combustion of an oxygen cylinder was the cause of a fire in an operating theatre and an emergency medical service. The fire developed after turning on the gas main while the flow supply valve was already open. Not opening the pressure reduction valve while the oxygen flow supply valve is open can prevent this type of fire. Information from the contractor shows that the probability of such an incident is 1 in a million.

  9. Combustion of bulk titanium in oxygen

    NASA Technical Reports Server (NTRS)

    Clark, A. F.; Moulder, J. C.; Runyan, C. C.

    1975-01-01

    The combustion of bulk titanium in one atmosphere oxygen is studied using laser ignition and several analytical techniques. These were high-speed color cinematography, time and space resolved spectra in the visible region, metallography (including SEM) of specimens quenched in argon gas, X-ray and chemical product analyses, and a new optical technique, the Hilbert transform method. The cinematographic application of this technique for visualizing phase objects in the combustion zone is described. The results indicate an initial vapor phase reaction immediately adjacent to the molten surface but as the oxygen uptake progresses the evaporation approaches the point of congruency and a much reduced evaporation rate. This and the accumulation of the various soluble oxides soon drive the reaction zone below the surface where gas formation causes boiling and ejection of particles. The buildup of rutile cuts off the oxygen supply and the reaction ceases.

  10. Quantitative measurement of oxygen in microgravity combustion

    NASA Technical Reports Server (NTRS)

    Silver, Joel A.

    1995-01-01

    This research combines two innovations in an experimental system which should result in a new capability for quantitative, nonintrusive measurement of major combustion species. Using a newly available vertical cavity surface-emitting diode laser (VCSEL) and an improved spatial scanning method, we plan to measure the temporal and spatial profiles of the concentrations and temperatures of molecular oxygen in a candle flame and in a solid fuel (cellulose sheet) system. The required sensitivity for detecting oxygen is achieved by the use of high frequency wavelength modulation spectroscopy (WMS). Measurements will be performed in the NASA Lewis 2.2-second Drop Tower Facility. The objective of this research is twofold. First, we want to develop a better understanding of the relative roles of diffusion and reaction of oxygen in microgravity combustion. As the primary oxidizer species, oxygen plays a major role in controlling the observed properties of flames, including flame front speed (in solid or liquid flames), extinguishment characteristics, flame size, and flame temperature. The second objective is to develop better diagnostics based on diode laser absorption which can be of real value in microgravity combustion research. We will also demonstrate diode lasers' potential usefulness for compact, intrinsically-safe monitoring sensors aboard spacecraft. Such sensors could be used to monitor any of the major cabin gases as well as important pollutants.

  11. SITE PROGRAM APPLICATIONS ANALYSIS ASSESSMENT OF SUPERFUND APPLICATIONS FOR THE AMERICAN COMBUSTION INC. PYRETRON OXYGEN ENHANCED BURNER

    EPA Science Inventory

    Incineration is widely used to clean up Superfund sites. Modifications which improve the efficiency with which waste can be incinerated are therefore of interest to EPA. Oxygen/air burners are of interest because their installation on conventional incinerators can allow for signi...

  12. Bimetallic Fe-Ni Oxygen Carriers for Chemical Looping Combustion

    SciTech Connect

    Bhavsar, Saurabh; Veser, Goetz

    2013-11-06

    The relative abundance, low cost, and low toxicity of iron make Fe-based oxygen carriers of great interest for chemical looping combustion (CLC), an emerging technology for clean and efficient combustion of fossil and renewable fuels. However, Fe also shows much lower reactivity than other metals (such as Ni and Cu). Here, we demonstrate strong improvement of Fe-based carriers by alloying the metal phase with Ni. Through a combination of carrier synthesis and characterization with thermogravimetric and fixed-bed reactor studies, we demonstrate that the addition of Ni results in a significant enhancement in activity as well as an increase in selectivity for total oxidation. Furthermore, comparing alumina and ceria as support materials highlights the fact that reducible supports can result in a strong increase in oxygen carrier utilization.

  13. Quantitative Measurement of Oxygen in Microgravity Combustion

    NASA Technical Reports Server (NTRS)

    Silver, Joel A.

    1997-01-01

    A low-gravity environment, in space or in ground-based facilities such as drop towers, provides a unique setting for studying combustion mechanisms. Understanding the physical phenomena controlling the ignition and spread of flames in microgravity has importance for space safety as well as for better characterization of dynamical and chemical combustion processes which are normally masked by buoyancy and other gravity-related effects. Due to restrictions associated with performing measurements in reduced gravity, diagnostic methods which have been applied to microgravity combustion studies have generally been limited to capture of flame emissions on film or video, laser Schlieren imaging and (intrusive) temperature measurements using thermocouples. Given the development of detailed theoretical models, more sophisticated diagnostic methods are needed to provide the kind of quantitative data necessary to characterize the properties of microgravity combustion processes as well as provide accurate feedback to improve the predictive capabilities of the models. When the demands of space flight are considered, the need for improved diagnostic systems which are rugged, compact, reliable, and operate at low power becomes apparent. The objective of this research is twofold. First, we want to develop a better understanding of the relative roles of diffusion and reaction of oxygen in microgravity combustion. As the primary oxidizer species, oxygen plays a major role in controlling the observed properties of flames, including flame front speed (in solid or liquid flames), extinguishment characteristics, flame size and flame temperature. The second objective is to develop better diagnostics based on diode laser absorption which can be of real value in both microgravity combustion research and as a sensor on-board Spacelab as either an air quality monitor or as part of a fire detection system. In our prior microgravity work, an eight line-of-sight fiber optic system measured

  14. Reactive Oxygen Species in Combustion Aerosols

    NASA Astrophysics Data System (ADS)

    Balasubramanian, R.; See, S.

    2007-12-01

    Research on airborne particulate matter (PM) has received increased concern in recent years after it was identified as a major component of the air pollution mix that is strongly associated with premature mortality and morbidity. Particular attention has been paid to understanding the potential health impacts of fine particles (PM2.5), which primarily originate from combustion sources. One group of particulate-bound chemical components of health concern is reactive oxygen species (ROS), which include molecules such as hydrogen peroxide (H2O2), ions such as hypochlorite ion (OCl-), free radicals such as hydroxyl radical (·OH) and superoxide anion (·O2-) which is both an ion and a radical. However, the formation of ROS in PM is not clearly understood yet. Furthermore, the concentration of ROS in combustion particles of different origin has not been quantified. The primary objective of this work is to study the effect of transition metals on the production of ROS in PM2.5 by determining the concentrations of ROS and metals. Both soluble and total metals were measured to evaluate their respective associations with ROS. PM2.5 samples were collected from several outdoor and indoor combustion sources, including those emitted from on-road vehicles, food cooking, incense sticks, and cigarette smoke. PM2.5 samples were also collected from the background air in both the ambient outdoor and indoor environments to assess the levels of particulate-bound transition metals and ROS with no combustion activities in the vicinity of sampling locations. Results obtained from this comprehensive study on particulate-bound ROS will be presented and discussed.

  15. Low NOx combustion using cogenerated oxygen and nitrogen streams

    DOEpatents

    Kobayashi, Hisashi; Bool, Lawrence E.; Snyder, William J.

    2009-02-03

    Combustion of hydrocarbon fuel is achieved with less formation of NOx by feeding the fuel into a slightly oxygen-enriched atmosphere, and separating air into oxygen-rich and nitrogen-rich streams which are fed separately into the combustion device.

  16. Dilute Oxygen Combustion Phase 2 Final Report

    SciTech Connect

    Ryan, H.M.; Riley, M.F.; Kobayashi, H.

    2005-09-30

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions

  17. Dilute oxygen combustion. Phase I report

    SciTech Connect

    1997-10-01

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NO{sub x}) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NO{sub x} through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NO{sub x} production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature ({approximately}1366 K) oxidant (7-27% O{sub 2} vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d{sup +} scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d{sup +} scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW ({approximately}0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric

  18. Dilute Oxygen Combustion Phase I Final Report

    SciTech Connect

    Ryan, H.M.; Riley, M.F.; Kobayashi, H.

    1997-10-31

    A novel burner, in which fuel (natural gas) and oxidant (oxygen or air) are separately injected into a furnace, shows promise for achieving very low nitrogen oxide(s) (NOx) emissions for commercial furnace applications. The dilute oxygen combustion (DOC) burner achieves very low NOx through in-furnace dilution of the oxidant stream prior to combustion, resulting in low flame temperatures, thus inhibiting thermal NOx production. The results of a fundamental and applied research effort on the development of the DOC burner are presented. In addition, the results of a market survey detailing the potential commercial impact of the DOC system are disclosed. The fundamental aspects of the burner development project involved examining the flame characteristics of a natural gas turbulent jet in a high-temperature (~1366 K) oxidant (7-27% O2 vol. wet). Specifically, the mass entrainment rate, the flame lift-off height, the velocity field and major species field of the jet were evaluated as a function of surrounding-gas temperature and composition. The measured entrainment rate of the fuel jet decreased with increasing oxygen content in the surrounding high-temperature oxidant, and was well represented by the d+ scaling correlation found in the literature. The measured flame lift-off height decreased with increasing oxygen content and increasing temperature of the surrounding gas. An increase in surrounding-gas oxygen content and/or temperature inhibited the velocity decay within the jet periphery as a function of axial distance as compared to isothermal turbulent jets. However, the velocity measurements were only broadly represented by the d+ scaling correlation. Several DOC burner configurations were tested in a laboratory-scale furnace at a nominal firing rate of 185 kW (~0.63 MMBtu/h). The flue gas composition was recorded as a function of furnace nitrogen content, furnace temperature, burner geometric arrangement, firing rate, and fuel injection velocity. NOx emissions

  19. Dilute Oxygen Combustion Phase IV Final Report

    SciTech Connect

    Riley, M.F.

    2003-04-30

    Novel furnace designs based on Dilute Oxygen Combustion (DOC) technology were developed under subcontract by Techint Technologies, Coraopolis, PA, to fully exploit the energy and environmental capabilities of DOC technology and to provide a competitive offering for new furnace construction opportunities. Capital cost, fuel, oxygen and utility costs, NOx emissions, oxide scaling performance, and maintenance requirements were compared for five DOC-based designs and three conventional air5-fired designs using a 10-year net present value calculation. A furnace direct completely with DOC burners offers low capital cost, low fuel rate, and minimal NOx emissions. However, these benefits do not offset the cost of oxygen and a full DOC-fired furnace is projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The incremental cost of the improved NOx performance is roughly $6/lb NOx, compared with an estimated $3/lb. NOx for equ8pping a conventional furnace with selective catalytic reduction (SCCR) technology. A furnace fired with DOC burners in the heating zone and ambient temperature (cold) air-fired burners in the soak zone offers low capital cost with less oxygen consumption. However, the improvement in fuel rate is not as great as the full DOC-fired design, and the DOC-cold soak design is also projected to cost $1.30 per ton more to operate than a conventional air-fired furnace. The NOx improvement with the DOC-cold soak design is also not as great as the full DOC fired design, and the incremental cost of the improved NOx performance is nearly $9/lb NOx. These results indicate that a DOC-based furnace design will not be generally competitive with conventional technology for new furnace construction under current market conditions. Fuel prices of $7/MMBtu or oxygen prices of $23/ton are needed to make the DOC furnace economics favorable. Niche applications may exist, particularly where access to capital is limited or floor space limitations

  20. Gasdynamic enhancement of nonpremixed combustion

    SciTech Connect

    Marble, F.E.

    1994-12-31

    To promote efficient performance of very high speed air-breathing propulsion systems, the combustor Mach number must be of the order of six for a flight Mach number of 18. Because of this high gas speed through the combustor, mixing rates of hydrogen fuel with air must be very rapid in order to allow a combustor of reasonable length. It is proposed to enhance the rate of mixing and combustion of hydrogen and air, and thereby reduce combustor length, through the introduction of streamwise vorticity generated by the interaction of a weak oblique shock wave with the density gradient between air and a cylindrical jet of hydrogen. Because of the high Mach number flow in the combustor, the oblique shock traverses the jet at a small angle with respect to the free stream direction, and the principle of slender body theory allows one conceptually to replace the three-dimensional steady flow with a two-dimensional unsteady flow. As a consequence, two-dimensional time-dependent computational studies and an extensive experimental shock tube investigation were employed to assess mixing rates for the steady flow in the combustor. The results indicated that under realistic conditions, adequate mixing could be accomplished within 1 ms, a rate that was technologically interesting. Encouraged by these experiments, a ``practical`` injector, utilizing shock-enhanced mixing, was designed for a combustor having a free stream Mach number of 6.0. A detailed aerodynamic and mixing investigation was carried out in the Mach 6 High Reynolds Number Tunnel at the NASA-Langley Research Center. The results confirmed both the details and the overall effectiveness of the shock-enhanced mixing concept.

  1. DEMONSTRATION BULLETIN: THE PYRETRON OXYGEN BURNER, AMERICAN COMBUSTION TECHNOLOGIES, INC.

    EPA Science Inventory

    The Pyretron is a burner which is designed to allow for the injection of oxygen into the combustion air stream for the purpose of increasing the efficiency of a hazardous waste incinerator. The SITE demonstration of the Pyretron took place at the U.S. EPA's Combustion Re...

  2. Engine valve actuation for combustion enhancement

    DOEpatents

    Reitz, Rolf Deneys; Rutland, Christopher J.; Jhavar, Rahul

    2008-03-04

    A combustion chamber valve, such as an intake valve or an exhaust valve, is briefly opened during the compression and/or power strokes of a 4-strokes combustion cycle in an internal combustion engine (in particular, a diesel or CI engine). The brief opening may (1) enhance mixing withing the combustion chamber, allowing more complete oxidation of particulates to decrease engine emissions; and/or may (2) delay ignition until a more desirable time, potentially allowing a means of timing ignition in otherwise difficult-to-control conditions, e.g., in HCCI (Homogeneous Charge Compression Ignition) conditions.

  3. Engine Valve Actuation For Combustion Enhancement

    DOEpatents

    Reitz, Rolf Deneys; Rutland, Christopher J.; Jhavar, Rahul

    2004-05-18

    A combustion chamber valve, such as an intake valve or an exhaust valve, is briefly opened during the compression and/or power strokes of a 4-stroke combustion cycle in an internal combustion engine (in particular, a diesel or CI engine). The brief opening may (1) enhance mixing withing the combustion chamber, allowing more complete oxidation of particulates to decrease engine emissions; and/or may (2) delay ignition until a more desirable time, potentially allowing a means of timing ignition in otherwise difficult-to-control conditions, e.g., in HCCI (Homogeneous Charge Compression Ignition) conditions.

  4. Natural Ores as Oxygen Carriers in Chemical Looping Combustion

    SciTech Connect

    Tian, Hanjing; Siriwardane, Ranjani; Simonyi, Thomas; Poston, James

    2013-08-01

    Chemical looping combustion (CLC) is a combustion technology that utilizes oxygen from oxygen carriers (OC), such as metal oxides, instead of air to combust fuels. The use of natural minerals as oxygen carriers has advantages, such as lower cost and availability. Eight materials, based on copper or iron oxides, were selected for screening tests of CLC processes using coal and methane as fuels. Thermogravimetric experiments and bench-scale fixed-bed reactor tests were conducted to investigate the oxygen transfer capacity, reaction kinetics, and stability during cyclic reduction/oxidation reaction. Most natural minerals showed lower combustion capacity than pure CuO/Fe{sub 2}O{sub 3} due to low-concentrations of active oxide species in minerals. In coal CLC, chryscolla (Cu-based), magnetite, and limonite (Fe-based) demonstrated better reaction performances than other materials. The addition of steam improved the coal CLC performance when using natural ores because of the steam gasification of coal and the subsequent reaction of gaseous fuels with active oxide species in the natural ores. In methane CLC, chryscolla, hematite, and limonite demonstrated excellent reactivity and stability in 50-cycle thermogravimetric analysis tests. Fe{sub 2}O{sub 3}-based ores possess greater oxygen utilization but require an activation period before achieving full performance in methane CLC. Particle agglomeration issues associated with the application of natural ores in CLC processes were also studied by scanning electron microscopy (SEM).

  5. Effects of oxygen dissociation on hypervelocity combustion experiments

    NASA Technical Reports Server (NTRS)

    Bakos, R. J.; Morgan, R. G.; Tamagno, J.

    1992-01-01

    Results are presented of a comparative experimental study conducted to measure the effects of the test gas oxygen dissociation produced in reflected shock tunnels on hypervelocity combustion. An identical combustor model was tested in a reflected shock tunnel with test gas containing about 50 pct by mass of oxygen in dissociated form, as either nitric oxide or atomic oxygen, and in an expansion tube with test gas having negligible dissociated oxygen. Comparisons are made at two test conditions that are energy equivalent to flight conditions at Mach 13.5 and 17.

  6. Combustion Enhancement with a Silent Discharge Plasma

    NASA Astrophysics Data System (ADS)

    Rosocha, Louis

    2003-10-01

    It is well known that the application of an external electric field to a flame can affect its propagation speed, stability, and combustion chemistry (Lawton & Weinberg 1969). External electrodes, arc discharges, and plasma jets have been employed to allow combustible gas mixtures to operate outside their flammability limits by gas heating, injection of free radicals, and field-promoted flame stabilization (Yagodnikov & Voronetskii 1994). Other investigators have carried out experiments with silent electrical discharges applied to propagating flames (Inomata et al 1983, Kim et al 2003). These have demonstrated that the flame propagation velocity is actually decreased (combustion retarded) when a silent discharge is applied directly to the flame region, but that the flame propagation velocity is increased (combustion promoted) when a silent discharge is applied to the unburned gas mixture upstream of a flame. Two other recent works have considered the possibility of combustion enhancement in aircraft gas turbine engine combustor mixers by using a plasma-generating fuel nozzle, that employs an electric-arc or microwave plasma generator, to produce dissociated fuel or ionized fuel (Johnson et al 2001); and pulsed corona-enhanced detonation of fuel-air mixtures in jet engines (Wang et al 2003). In contrast to these prior works, we have employed a silent discharge plasma (SDP) reactor to break up large fuel molecules into smaller molecules and create free radicals or other active species in a gas stream before the fuel is mixed with an oxidizer and combusted. In experiments reported here, a cylindrical SDP reactor was used to 'activate' propane before mixing it with air and igniting the combustible gas mixture. With the plasma, the physical appearance of the flame changes and substantial changes in mass spectrometer fragmentation peaks are observed (e.g., propane fragments decrease and water and carbon dioxide increase). This indicates that the combustion process is

  7. Simulation and experiment for oxygen-enriched combustion engine using liquid oxygen to solidify CO2

    NASA Astrophysics Data System (ADS)

    Liu, Yongfeng; Jia, Xiaoshe; Pei, Pucheng; Lu, Yong; Yi, Li; Shi, Yan

    2016-01-01

    For capturing and recycling of CO2 in the internal combustion engine, Rankle cycle engine can reduce the exhaust pollutants effectively under the condition of ensuring the engine thermal efficiency by using the techniques of spraying water in the cylinder and optimizing the ignition advance angle. However, due to the water spray nozzle need to be installed on the cylinder, which increases the cylinder head design difficulty and makes the combustion conditions become more complicated. In this paper, a new method is presented to carry out the closing inlet and exhaust system for internal combustion engines. The proposed new method uses liquid oxygen to solidify part of cooled CO2 from exhaust system into dry ice and the liquid oxygen turns into gas oxygen which is sent to inlet system. The other part of CO2 is sent to inlet system and mixed with oxygen, which can reduce the oxygen-enriched combustion detonation tendency and make combustion stable. Computing grid of the IP52FMI single-cylinder four-stroke gasoline-engine is established according to the actual shape of the combustion chamber using KIVA-3V program. The effects of exhaust gas recirculation (EGR) rate are analyzed on the temperatures, the pressures and the instantaneous heat release rates when the EGR rate is more than 8%. The possibility of enclosing intake and exhaust system for engine is verified. The carbon dioxide trapping device is designed and the IP52FMI engine is transformed and the CO2 capture experiment is carried out. The experimental results show that when the EGR rate is 36% for the optimum EGR rate. When the liquid oxygen of 35.80-437.40 g is imported into the device and last 1-20 min, respectively, 21.50-701.30 g dry ice is obtained. This research proposes a new design method which can capture CO2 for vehicular internal combustion engine.

  8. Oxygen enriched combustion system performance study. Phase 2: 100 percent oxygen enriched combustion in regenerative glass melters, Final report

    SciTech Connect

    Tuson, G.B.; Kobayashi, H.; Campbell, M.J.

    1994-08-01

    The field test project described in this report was conducted to evaluate the energy and environmental performance of 100% oxygen enriched combustion (100% OEC) in regenerative glass melters. Additional objectives were to determine other impacts of 100% OEC on melter operation and glass quality, and to verify on a commercial scale that an on-site Pressure Swing Adsorption oxygen plant can reliably supply oxygen for glass melting with low electrical power consumption. The tests constituted Phase 2 of a cooperative project between the United States Department of Energy, and Praxair, Inc. Phase 1 of the project involved market and technical feasibility assessments of oxygen enriched combustion for a range of high temperature industrial heating applications. An assessment of oxygen supply options for these applications was also performed during Phase 1, which included performance evaluation of a pilot scale 1 ton per day PSA oxygen plant. Two regenerative container glass melters were converted to 100% OEC operation and served as host sites for Phase 2. A 75 ton per day end-fired melter at Carr-Lowrey Glass Company in Baltimore, Maryland, was temporarily converted to 100% OEC in mid- 1990. A 350 tpd cross-fired melter at Gallo Glass Company in Modesto, California was rebuilt for permanent commercial operation with 100% OEC in mid-1991. Initially, both of these melters were supplied with oxygen from liquid storage. Subsequently, in late 1992, a Pressure Swing Adsorption oxygen plant was installed at Gallo to supply oxygen for 100% OEC glass melting. The particular PSA plant design used at Gallo achieves maximum efficiency by cycling the adsorbent beds between pressurized and evacuated states, and is therefore referred to as a Vacuum/Pressure Swing Adsorption (VPSA) plant.

  9. On the influence of singlet oxygen molecules on characteristics of HCCI combustion: A numerical study

    NASA Astrophysics Data System (ADS)

    Starik, A. M.; Kozlov, V. E.; Titova, N. S.

    2013-08-01

    Mechanisms of homogeneous charge compression ignition (HCCI) combustion enhancement are investigated numerically when excited O2(a 1Δg) molecules are produced at different points in the compression stroke. The analysis is conducted with the use of an extended kinetic model involving the submechanism of nitric oxide formation in the presence of singlet oxygen O2(a 1Δg) or O2(b 1Σg +) molecules in the methane-air mixture. It is demonstrated that the abundance of excited O2(a 1Δg) molecules in the mixture even in a small amounts intensifies the ignition and combustion and allows one to control the ignition event in the HCCI engine. Such a method of energy supply in the HCCI engine is much more effective in advancement of combustion timing than mere heating of the mixture, because it leads to acceleration of the chain-branching mechanism. The excitation of O2 molecules to the a 1Δg electronic state makes it possible to organise the successful combustion in the cylinder at diminished initial temperature of the mixture and increase the effective energy released during HCCI combustion. The advance in the value of this energy is much higher than the energy needed for the excitation of oxygen molecules. Moreover, in this case, the output concentration of NO and CO can be reduced significantly.

  10. Powdered aluminum and oxygen rocket propellants: Subscale combustion experiments

    NASA Technical Reports Server (NTRS)

    Meyer, Mike L.

    1993-01-01

    Aluminum combined with oxygen has been proposed as a potential lunar in situ propellant for ascent/descent and return missions for future lunar exploration. Engine concepts proposed to use this propellant have not previously been demonstrated, and the impact on performance from combustion and two-phase flow losses could only be estimated. Therefore, combustion tests were performed for aluminum and aluminum/magnesium alloy powders with oxygen in subscale heat-sink rocket engine hardware. The metal powder was pneumatically injected, with a small amount of nitrogen, through the center orifice of a single element O-F-O triplet injector. Gaseous oxygen impinged on the fuel stream. Hot-fire tests of aluminum/oxygen were performed over a mixture ratio range of 0.5 to 3.0, and at a chamber pressure of approximately 480 kPa (70 psia). The theoretical performance of the propellants was analyzed over a mixture ratio range of 0.5 to 5.0. In the theoretical predictions the ideal one-dimensional equilibrium rocket performance was reduced by loss mechanisms including finite rate kinetics, two-dimensional divergence losses, and boundary layer losses. Lower than predicted characteristic velocity and specific impulse performance efficiencies were achieved in the hot-fire tests, and this was attributed to poor mixing of the propellants and two-phase flow effects. Several tests with aluminum/9.8 percent magnesium alloy powder did not indicate any advantage over the pure aluminum fuel.

  11. REDUCTION OF NOx EMISSION FROM COAL COMBUSTION THROUGH OXYGEN ENRICHMENT

    SciTech Connect

    Western Research Institute

    2006-07-01

    BOC Process Gas Solutions and Western Research Institute (WRI) conducted a pilot-scale test program to evaluate the impact of oxygen enrichment on the emissions characteristics of pulverized coal. The combustion test facility (CTF) at WRI was used to assess the viability of the technique and determine the quantities of oxygen required for NOx reduction from coal fired boiler. In addition to the experimental work, a series of Computational Fluid Dynamics (CFD) simulations were made of the CTF under comparable conditions. A series of oxygen enrichment test was performed using the CTF. In these tests, oxygen was injected into one of the following streams: (1) the primary air (PA), (2) the secondary air (SA), and (3) the combined primary and secondary air. Emission data were collected from all tests, and compared with the corresponding data from the baseline cases. A key test parameter was the burner stoichiometry ratio. A series of CFD simulation models were devised to mimic the initial experiments in which secondary air was enriched with oxygen. The results from these models were compared against the experimental data. Experimental evidence indicated that oxygen enrichment does appear to be able to reduce NOx levels from coal combustion, especially when operated at low over fire air (OFA) levels. The reductions observed however are significantly smaller than that reported by others (7-8% vs. 25-50%), questioning the economic viability of the technique. This technique may find favor with fuels that are difficult to burn or stabilize at high OFA and produce excessive LOI. While CFD simulation appears to predict NO amounts in the correct order of magnitude and the correct trend with staging, it is sensitive to thermal conditions and an accurate thermal prediction is essential. Furthermore, without development, Fluent's fuel-NO model cannot account for a solution sensitive fuel-N distribution between volatiles and char and thus cannot predict the trends seen in the

  12. Observation of spontaneous combustion of hydrogen and oxygen in microbubbles

    NASA Astrophysics Data System (ADS)

    Postnikov, A. V.; Uvarov, I. V.; Prokaznikov, A. V.; Svetovoy, V. B.

    2016-03-01

    Experimental evidence is presented that combustion can ignite at room temperature spontaneously inside microbubbles filled with mixture of hydrogen and oxygen. We perform water electrolysis in a closed microchamber by voltage pulses of alternating polarity at repetition frequencies ≥100 kHz to pump the gases rapidly into the electrolyte and produce extreme supersaturation with both gases. After a delay of 300 -600 μs , we observe stroboscopically microbubbles of 5 -20 μm in diameter that appear in between the electrodes for several microseconds. Each event is accompanied by a pressure jump of 0.1 -1 bar that is measured interferometrically. The pressure jumps are attributed to combustion of the gases in the microbubbles.

  13. Polymer-Oxygen Compatibility Testing: Effect of Oxygen Aging on Ignition and Combustion Properties

    NASA Technical Reports Server (NTRS)

    Waller, Jess M.; Haas, Jon P.; Wilson, D. Bruce; Fries, Joseph (Technical Monitor)

    2000-01-01

    The oxygen compatibility of six polymers used in oxygen service was evaluated after exposure for 48 hours to oxygen pressures ranging from 350 to 6200 kPa (50 to 900 psia), and temperatures ranging from 50 to 250 C (122 to 302 F). Three elastomers were tested: CR rubber (C873-70), FKM fluorocarbon rubber (Viton A), and MPQ silicone rubber (MIL-ZZ-765, Class 2); and three thermoplastics were tested: polyhexamethylene adipamide (Zytel 42), polytetrafluoroethylene (Teflon TFE), and polychlorotrifluoroethylene (Neoflon CTFE M400H). Post-aging changes in mass, dimensions, tensile strength, elongation at break, and durometer hardness were determined. Also, the compression set was determined for the three elastomers. Results show that the properties under investigation were more sensitive to oxygen pressure at low to moderate temperatures, and more sensitive to temperature at low to moderate oxygen pressures. Inspection of the results also suggested that both chain scissioning and cross-linking processes were operative, consistent with heterogeneous oxidation. Attempts are underway to verify conclusively the occurrence of heterogeneous oxidation using a simple modulus profiling technique. Finally, the effect of aging at 620 kpa (90 psia) and 121 C (250 F) on ignition and combustion resistance was determined. As expected, aged polymers were less ignitable and combustible (had higher AlTs and lower heats of combustion). Special attention was given to Neoflon CTFE. More specifically, the effect of process history (compression versus extrusion molding) and percent crystallinity (quick- versus slow-quenched) on the AIT, heat of combustion, and impact sensitivity of Neoflon CTFE was investigated. Results show the AIT, heat of combustion, and impact sensitivity to be essentially independent of Neoflon CTFE process history and structure.

  14. Methanol Droplet Combustion in Oxygen-Inert Environments in Microgravity

    NASA Technical Reports Server (NTRS)

    Nayagam, Vedha; Dietrich, Daniel L.; Hicks, Michael C.; Williams, Forman A.

    2013-01-01

    The Flame Extinguishment (FLEX) experiment that is currently underway in the Combustion Integrated Rack facility onboard the International Space Station is aimed at understanding the effects of inert diluents on the flammability of condensed phase fuels. To this end, droplets of various fuels, including alkanes and alcohols, are burned in a quiescent microgravity environment with varying amounts of oxygen and inert diluents to determine the limiting oxygen index (LOI) for these fuels. In this study we report experimental observations of methanol droplets burning in oxygen-nitrogen-carbon dioxide and oxygen-nitrogen-helium gas mixtures at 0.7 and 1 atmospheric pressures. The initial droplet size varied between approximately 1.5 mm and 4 mm to capture both diffusive extinction brought about by insufficient residence time at the flame and radiative extinction caused by excessive heat loss from the flame zone. The ambient oxygen concentration varied from a high value of 30% by volume to as low as 12%, approaching the limiting oxygen index for the fuel. The inert dilution by carbon dioxide and helium varied over a range of 0% to 70% by volume. In these experiments, both freely floated and tethered droplets were ignited using symmetrically opposed hot-wire igniters and the burning histories were recorded onboard using digital cameras, downlinked later to the ground for analysis. The digital images yielded droplet and flame diameters as functions of time and subsequently droplet burning rate, flame standoff ratio, and initial and extinction droplet diameters. Simplified theoretical models correlate the measured burning rate constant and the flame standoff ratio reasonably well. An activation energy asymptotic theory accounting for time-dependent water dissolution or evaporation from the droplet is shown to predict the measured diffusive extinction conditions well. The experiments also show that the limiting oxygen index for methanol in these diluent gases is around 12% to

  15. Enhanced Combustion Low NOx Pulverized Coal Burner

    SciTech Connect

    David Towle; Richard Donais; Todd Hellewell; Robert Lewis; Robert Schrecengost

    2007-06-30

    For more than two decades, Alstom Power Inc. (Alstom) has developed a range of low cost, infurnace technologies for NOx emissions control for the domestic U.S. pulverized coal fired boiler market. This includes Alstom's internally developed TFS 2000{trademark} firing system, and various enhancements to it developed in concert with the U.S. Department of Energy. As of the date of this report, more than 270 units representing approximately 80,000 MWe of domestic coal fired capacity have been retrofit with Alstom low NOx technology. Best of class emissions range from 0.18 lb/MMBtu for bituminous coal to 0.10 lb/MMBtu for subbituminous coal, with typical levels at 0.24 lb/MMBtu and 0.13 lb/MMBtu, respectively. Despite these gains, NOx emissions limits in the U.S. continue to ratchet down for new and existing boiler equipment. On March 10, 2005, the Environmental Protection Agency (EPA) announced the Clean Air Interstate Rule (CAIR). CAIR requires 25 Eastern states to reduce NOx emissions from the power generation sector by 1.7 million tons in 2009 and 2.0 million tons by 2015. Low cost solutions to meet such regulations, and in particular those that can avoid the need for a costly selective catalytic reduction system (SCR), provide a strong incentive to continue to improve low NOx firing system technology to meet current and anticipated NOx control regulations. The overall objective of the work is to develop an enhanced combustion, low NOx pulverized coal burner, which, when integrated with Alstom's state-of-the-art, globally air staged low NOx firing systems will provide a means to achieve: Less than 0.15 lb/MMBtu NOx emissions when firing a high volatile Eastern or Western bituminous coal, Less than 0.10 lb/MMBtu NOx emissions when firing a subbituminous coal, NOx reduction costs at least 25% lower than the costs of an SCR, Validation of the NOx control technology developed through large (15 MWt) pilot scale demonstration, and Documentation required for economic

  16. Thermodynamic, transport, and flow properties of gaseous products resulting from combustion of methane-air-oxygen

    NASA Technical Reports Server (NTRS)

    Klich, G. F.

    1976-01-01

    Results of calculations to determine thermodynamic, transport, and flow properties of combustion product gases are presented. The product gases are those resulting from combustion of methane-air-oxygen and methane-oxygen mixtures. The oxygen content of products resulting from the combustion of methane-air-oxygen mixtures was similiar to that of air; however, the oxygen contained in products of methane-oxygen combustion ranged from 20 percent by volume to zero for stoichiometric combustion. Calculations were made for products of reactant mixtures with fuel percentages, by mass, of 7.5 to 20. Results are presented for specific mixtures for a range of pressures varying from 0.0001 to 1,000 atm and for temperatures ranging from 200 to 3,800 K.

  17. Enhancement of burning velocity by dissociated oxygen atoms

    NASA Astrophysics Data System (ADS)

    Akashi, Haruaki; Yoshinaga, Tomokazu; Sasaki, Koichi

    2015-09-01

    Green technology, such as preventing global warming, has been developed for years. Researches on plasma assisted combustion is one of the technologies and have been done for investigating more efficient combustion, more efficient use of fossil fuel with plasmas or applying electric fields. In the ignition time delay analyses with the dissociated oxygen atoms which is generated by non-equilibrium plasma had significant effect on the ignition time. In this paper, dissociated oxygen could effect on burning velocity or not has been examined using CHEMKIN. As a result, no effect can be seen with dissociation degree of lower than 10-3. But there is an effect on the enhancement of burning velocity with higher degree of 10-3. At the dissociation degree of 5×10-2, the burning velocity is enhanced at a factor of 1.24. And it is found that the distributions of each species in front of preheat zone are completely different. The combustion process is proceeded several steps in advance, and generation of H2O, CO and CO2 can be seen before combustion in higher dissociation case. This work was supported by KAKENHI (22340170).

  18. Combustion of hydrogen-oxygen mixture in electrochemically generated nanobubbles.

    PubMed

    Svetovoy, Vitaly B; Sanders, Remko G P; Lammerink, Theo S J; Elwenspoek, Miko C

    2011-09-01

    Ignition of exothermic chemical reactions in small volumes is considered as difficult or impossible due to the large surface-to-volume ratio. Here observation of the spontaneous reaction is reported between hydrogen and oxygen in bubbles whose diameter is smaller than a threshold value around 150 nm. The effect is attributed to high Laplace pressure and to fast dynamics in nanobubbles and is the first indication on combustion in the nanoscale. In this study the bubbles were produced by water electrolysis using successive generation of H(2) and O(2) above the same electrode with short voltage pulses in the microsecond range. The process was observed in a microsystem at current densities >1000 A/cm(2) and relative supersaturations >1000.

  19. Combustion of hydrogen-oxygen mixture in electrochemically generated nanobubbles

    NASA Astrophysics Data System (ADS)

    Svetovoy, Vitaly B.; Sanders, Remko G. P.; Lammerink, Theo S. J.; Elwenspoek, Miko C.

    2011-09-01

    Ignition of exothermic chemical reactions in small volumes is considered as difficult or impossible due to the large surface-to-volume ratio. Here observation of the spontaneous reaction is reported between hydrogen and oxygen in bubbles whose diameter is smaller than a threshold value around 150 nm. The effect is attributed to high Laplace pressure and to fast dynamics in nanobubbles and is the first indication on combustion in the nanoscale. In this study the bubbles were produced by water electrolysis using successive generation of H2 and O2 above the same electrode with short voltage pulses in the microsecond range. The process was observed in a microsystem at current densities >1000 A/cm2 and relative supersaturations >1000.

  20. Synergetic effects of mixed copper–iron oxides oxygen carriers in chemical looping combustion

    SciTech Connect

    Siriwardane, Ranjani; Tian, Hanjing; Simonyi, Thomas; Poston, James

    2013-06-01

    Chemical looping combustion (CLC) is an emerging technology for clean energy production from fuels. CLC produces sequestration-ready CO{sub 2}-streams without a significant energy penalty. Development of efficient oxygen carriers is essential to successfully operate a CLC system. Copper and iron oxides are promising candidates for CLC. Copper oxide possesses high reactivity but it has issues with particle agglomeration due to its low melting point. Even though iron oxide is an inexpensive oxygen carrier it has a slower reactivity. In this study, mixed metal oxide carriers containing iron and copper oxides were evaluated for coal and methane CLC. The components of CuO and Fe{sub 2}O{sub 3} were optimized to obtain good reactivity while maintaining physical and chemical stability during cyclic reactions for methane-CLC and solid-fuel CLC. Compared with single metal oxygen carriers, the optimized Cu–Fe mixed oxide oxygen carriers demonstrated high reaction rate, better combustion conversion, greater oxygen usage and improved physical stability. Thermodynamic calculations, XRD, TGA, flow reactor studies and TPR experiments suggested that there is a strong interaction between CuO and Fe{sub 2}O{sub 3} contributing to a synergistic effect during CLC reactions. The amount of oxygen release of the mixed oxide carrier in the absence of a fuel was similar to that of the single metal oxides. However, in the presence of fuels, the oxygen consumption and the reaction profiles of the mixed oxide carriers were significantly better than that of the single metal oxides. The nature of the fuel not only influenced the reactivity, but also the final reduction status of the oxygen carriers during chemical looping combustion. Cu oxide of the mixed oxide was fully reduced metallic copper with both coal and methane. Fe oxide of the mixed oxide was fully reduced Fe metal with methane but it was reduced to only FeO with coal. Possible mechanisms of how the presence of CuO enhances the

  1. Computational fluid dynamics modeling of chemical looping combustion process with calcium sulphate oxygen carrier - article no. A19

    SciTech Connect

    Baosheng Jin; Rui Xiao; Zhongyi Deng; Qilei Song

    2009-07-01

    To concentrate CO{sub 2} in combustion processes by efficient and energy-saving ways is a first and very important step for its sequestration. Chemical looping combustion (CLC) could easily achieve this goal. A chemical-looping combustion system consists of a fuel reactor and an air reactor. Two reactors in the form of interconnected fluidized beds are used in the process: (1) a fuel reactor where the oxygen carrier is reduced by reaction with the fuel, and (2) an air reactor where the reduced oxygen carrier from the fuel reactor is oxidized with air. The outlet gas from the fuel reactor consists of CO{sub 2} and H{sub 2}O, while the outlet gas stream from the air reactor contains only N{sub 2} and some unused O{sub 2}. The water in combustion products can be easily removed by condensation and pure carbon dioxide is obtained without any loss of energy for separation. Until now, there is little literature about mathematical modeling of chemical-looping combustion using the computational fluid dynamics (CFD) approach. In this work, the reaction kinetic model of the fuel reactor (CaSO{sub 4}+ H{sub 2}) is developed by means of the commercial code FLUENT and the effects of partial pressure of H{sub 2} (concentration of H{sub 2}) on chemical looping combustion performance are also studied. The results show that the concentration of H{sub 2} could enhance the CLC performance.

  2. Combustion Enhancement Using a Silent Discharge Plasma Reactor

    NASA Astrophysics Data System (ADS)

    Rosocha, Louis; Platts, David; Coates, Don; Stange, Sy

    2003-10-01

    Electric fields affect flame propagation speed, stability, and combustion chemistry. External electrodes, arc discharges, and plasma jets have been used to combust gas mixtures outside their flammability limits. Experiments with silent electrical discharges (SEDs) and propagating flames have shown that flame propagation velocity is actually decreased (combustion retarded) when an SED is applied directly to the flame region, but velocity is increased (combustion promoted) when applied to the unburned gas mixture upstream of a flame. More recent work has proposed electric arc/microwave-driven plasma-generating fuel nozzles to produce dissociated fuel or ionized fuel for aircraft gas turbine engine combustor mixers. In contrast to prior works, we have used a silent discharge plasma (SDP) reactor to break up large fuel molecules into smaller molecules and create free radicals/active species in a gas stream before the fuel is mixed with an oxidizer and combusted. A cylindrical SDP reactor was used to 'activate' propane before mixing it with air and igniting the combustible gas mixture. With the plasma, the physical appearance of the flame changes and substantial changes in mass spectrometer fragmentation peaks for fuel and combustion products are observed (i.e., combustion is enhanced). Results of changes in the degree of combustion will be discussed in terms of variations in the plasma specific energy.

  3. Carbon deposition model for oxygen-hydrocarbon combustion, volume 1

    NASA Technical Reports Server (NTRS)

    Hernandez, R.; Ito, J. I.; Niiya, K. Y.

    1987-01-01

    Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at pressures of 1000 to 1500 psia. No carbon deposition on the chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational consequences of carbon deposition on preburner/gas generator performance. The report is in two volumes, of which this is Volume 1 covering the main body of the report plus Appendixes A through D.

  4. Carbon Deposition Model for Oxygen-Hydrocarbon Combustion, Volume 2

    NASA Technical Reports Server (NTRS)

    Hernandez, R.; Ito, J. I.; Niiya, K. Y.

    1987-01-01

    Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at chamber pressures of 1000 to 1500 psia. No carbon deposition on chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational concequences of carbon deposition on preburner/gas generator performance. This is Volume 2 of the report, which contains data plots of all the test programs.

  5. Attrition Rate of Oxygen Carriers in Chemical Looping Combustion Systems

    NASA Astrophysics Data System (ADS)

    Feilen, Harry Martin

    This project developed an evaluation methodology for determining, accurately and rapidly, the attrition resistance of oxygen carrier materials used in chemical looping technologies. Existing test protocols, to evaluate attrition resistance of granular materials, are conducted under non-reactive and ambient temperature conditions. They do not accurately reflect the actual behavior under the unique process conditions of chemical looping, including high temperatures and cyclic operation between oxidizing and reducing atmospheres. This project developed a test method and equipment that represented a significant improvement over existing protocols. Experimental results obtained from this project have shown that hematite exhibits different modes of attrition, including both due to mechanical stresses and due to structural changes in the particles due to chemical reaction at high temperature. The test methodology has also proven effective in providing reactivity changes of the material with continued use, a property, which in addition to attrition, determines material life. Consumption/replacement cost due to attrition or loss of reactivity is a critical factor in the economic application of the chemical looping technology. This test method will allow rapid evaluation of a wide range of materials that are best suited for this technology. The most important anticipated public benefit of this project is the acceleration of the development of chemical looping technology for lowering greenhouse gas emissions from fossil fuel combustion.

  6. National Combustion Code Parallel Performance Enhancements

    NASA Technical Reports Server (NTRS)

    Quealy, Angela; Benyo, Theresa (Technical Monitor)

    2002-01-01

    The National Combustion Code (NCC) is being developed by an industry-government team for the design and analysis of combustion systems. The unstructured grid, reacting flow code uses a distributed memory, message passing model for its parallel implementation. The focus of the present effort has been to improve the performance of the NCC code to meet combustor designer requirements for model accuracy and analysis turnaround time. Improving the performance of this code contributes significantly to the overall reduction in time and cost of the combustor design cycle. This report describes recent parallel processing modifications to NCC that have improved the parallel scalability of the code, enabling a two hour turnaround for a 1.3 million element fully reacting combustion simulation on an SGI Origin 2000.

  7. The influence of thermal annealing on oxygen uptake and combustion rates of a bituminous coal char

    SciTech Connect

    Osvalda Senneca; Piero Salatino; Daniela Menghini

    2007-07-01

    The effect of thermal annealing on the combustion reactivity of a bituminous coal char has been investigated with a focus on the role of the formation of surface oxides by oxygen chemisorption. The combined use of thermogravimetric analysis and of analysis of the off-gas during isothermal combustion of char samples enabled the determination of the rate and extent of oxygen uptake along burn-off. Combustion was carried out at temperatures between 350 and 510{sup o}C. Char samples were prepared by controlled isothermal heat treatment of coal for different times (in the range between 1 s and 30 min) at different temperatures (in the range 900-2000{sup o}C). Results indicate that oxygen uptake is extensive along burn-off of chars prepared under mild heat treatment conditions. The maximum oxygen uptake is barely affected by the combustion temperature within the range of combustion conditions investigated. The severity of heat treatment has a pronounced effect on char combustion rate as well as on the extent and rate at which surface oxides are built up by oxygen chemisorption. Chars prepared under severe heat treatment conditions show negligible oxygen uptake and strongly reduced combustion rates. Altogether it appears that a close correlation can be established between the extent and the accessibility of active sites on the carbon surface and the combustion rate. Despite the investigation has been carried out at temperatures well below those of practical interest, results provide useful insight into the relationship existing between thermal annealing, formation of surface oxide and combustion reactivity which is relevant to the proper formulation of detailed kinetic models of char combustion. 31 refs., 6 figs., 1 tab.

  8. Algorithmic Enhancements for Unsteady Aerodynamics and Combustion Applications

    NASA Technical Reports Server (NTRS)

    Venkateswaran, Sankaran; Olsen, Michael (Technical Monitor)

    2001-01-01

    Research in the FY01 focused on the analysis and development of enhanced algorithms for unsteady aerodynamics and chemically reacting flowfields. The research was performed in support of NASA Ames' efforts to improve the capabilities of the in-house computational fluid dynamics code, OVERFLOW. Specifically, the research was focused on the four areas: (1) investigation of stagnation region effects; (2) unsteady preconditioning dual-time procedures; (3) dissipation formulation for combustion; and (4) time-stepping methods for combustion.

  9. Experimental investigation on combustion of hydrogen-oxygen and methane-oxygen mixtures in the medium of low-superheated steam

    NASA Astrophysics Data System (ADS)

    Pribaturin, N. A.; Fedorov, V. A.; Alekseev, M. V.; Bogomolov, A. R.; Sorokin, A. L.; Azikhanov, S. S.; Shevyrev, S. A.

    2016-05-01

    Experimental data are represented on the investigation of combustion of hydrogen-oxygen and methane-oxygen mixtures in the medium of low-superheated (initial temperature of approximately 150°C) steam at atmospheric pressure. The influence of the ratio of mass flows of the combustible mixture and steam on the qualitative composition of combustion products and the temperature of produced steam is revealed. Main laws for combustion of the hydrogen-oxygen mixture within the steam flow, which affect the completeness of mixture combustion, are determined. Experimental data on the influence of concentrations of the hydrogen-oxygen mixture within the flow of the steam and the combustible mixture upon the completeness of combustion are given. It is found that, when burning the hydrogen-oxygen mixture within the steam flow with a temperature of 1000-1200°C, it is possible using a variation of the combustible mixture flow. At the same time, the volume fraction of noncondensable gases in the produced steam is no more than 2%. It is revealed that there are several combustion modes of the hydrogen-oxygen mixture within the steam flow, in which, in one case, the steam always suppresses combustion and, in another one, detonation of the combustible mixture combustible mixture occurs. It is found that with the excess air factor close to unit, the combustion of the methane-oxygen mixture within steam and the vapor conversion of methane, which result in the appearance of free hydrogen in the produced high-temperature steam, are possible. The description and the principle of the operation of the experimental bench for investigation of combustion of methane-oxygen and hydrogen-oxygen mixtures in the medium of steam are given. Results of experimental investigations of burning fuel and oxygen in the medium of steam are used in the development of a steam superheater for a hightemperature steam turbine.

  10. Combustion of solid fuel in very low speed oxygen streams

    NASA Technical Reports Server (NTRS)

    Tien, James S.; Sacksteder, Kurt R.; Ferkul, Paul V.; Grayson, Gary D.

    1993-01-01

    In reduced gravity, the combustion of solid fuel in low-speed flow can be studied. The flame behavior in this low-speed regime will fill a void in our understanding of the flow effect on combustion. In addition, it is important for spacecraft fire safety considerations. In this work, modeling and experimental work on low-speed forced-concurrent-flow flame spread are carried out. In addition, experiments on reduced-gravity buoyant-flow flame spread are performed.

  11. Development and performance of Cu-based oxygen carriers for chemical-looping combustion

    SciTech Connect

    Chuang, S.Y.; Dennis, J.S.; Hayhurst, A.N.; Scott, S.A.

    2008-07-15

    Chemical-looping combustion (CLC) has the inherent property of separating the product CO{sub 2} from flue gases. Instead of air, it uses an oxygen carrier, usually in the form of a metal oxide, to provide oxygen for combustion. This paper focuses on the development and performance of a suitable Cu-based oxygen carrier for burning solid fuels using CLC. Carriers were made from CuO and Al{sub 2}O{sub 3} (as a support) in three different ways: mechanical mixing, wet impregnation, and co-precipitation. The reactivity of these solids was assessed by measuring their ability to oxidize CO, when in a hot bed of sand fluidized by a mixture of CO and N{sub 2}. After that, the Cu in the carrier was oxidized back to CuO by fluidizing the hot bed with air. These oxygen carriers were tested over many such cycles of reduction and oxidation. This work confirms that supporting CuO on Al{sub 2}O{sub 3} enhances the ability of the resulting particles to withstand mechanical and thermal stresses in a fluidized bed. Also, only co-precipitation produces particles that have a high loading of copper and do not agglomerate at 800-900 C. The performance of co-precipitated particles of CuO/Al{sub 2}O{sub 3} at oxidizing CO to CO{sub 2} was significantly affected by the pH of the solution in which precipitation occurred: a high pH (9.7) gave particles that reacted completely and rapidly. After 18 cycles, such a co-precipitated carrier with 82.5 wt% CuO yielded all its oxygen when oxidizing CO. X-ray analysis showed that when heated, CuO reacted with Al{sub 2}O{sub 3} to form CuAl{sub 2}O{sub 4}, which was fully reducible, so CuO experienced no loss in extent of reaction after forming this mixed oxide. An increase in operating temperature from 800 to 900 C led to the CuO providing slightly less oxygen; this was because a little of the CuO decomposed to Cu{sub 2}O between its reduction and oxidation, when the bed was fluidized by pure N{sub 2}. (author)

  12. Regenerable mixed copper-iron-inert support oxygen carriers for solid fuel chemical looping combustion process

    DOEpatents

    Siriwardane, Ranjani V.; Tian, Hanjing

    2016-12-20

    The disclosure provides an oxygen carrier for a chemical looping cycle, such as the chemical looping combustion of solid carbonaceous fuels, such as coal, coke, coal and biomass char, and the like. The oxygen carrier is comprised of at least 24 weight % (wt %) CuO, at least 10 wt % Fe2O3, and an inert support, and is typically a calcine. The oxygen carrier exhibits a CuO crystalline structure and an absence of iron oxide crystalline structures under XRD crystallography, and provides an improved and sustained combustion reactivity in the temperature range of 600.degree. C.-1000.degree. C. particularly for solid fuels such as carbon and coal.

  13. Simulation of surface profile formation in oxygen laser cutting of mild steel due to combustion cycles

    NASA Astrophysics Data System (ADS)

    Ermolaev, G. V.; Kovalev, O. B.

    2009-09-01

    A physicomathematical model of cyclic iron combustion in an oxygen flow during oxygen laser cutting of metal sheets is developed. The combustion front is set into motion by focused laser radiation and a heterogeneous oxidation reaction in oxygen. The burning rate is limited by oxygen supply from the gas phase towards the metal surface, and the interface motion depends on the local temperature. A 3D numerical simulation predicts wavy structures on the metal surface; their linear sizes depend on the scanning speed of the laser beam, the thickness of the produced liquid oxide film and the parameters of the oxygen jet flow. Simulation results help in understanding the mechanism of striation formation during oxygen gas-laser cutting of mild steel and are in qualitative agreement with experimental findings.

  14. Enhancement of pulverized coal combustion by plasma technology

    SciTech Connect

    Gorokhovski, M.A.; Jankoski, Z.; Lockwood, F.C.; Karpenko, E.I.; Messerle, V.E.; Ustimenko, A.B.

    2007-07-01

    Plasma-assisted pulverized coal combustion is a promising technology for thermal power plants (TPP). This article reports one- and three- dimensional numerical simulations, as well as laboratory and industrial measurements of coal combustion using a plasma-fuel system (PFS). The chemical kinetic and fluid mechanics involved in this technology are analysed. The results show that a PFS, can be used to promote early ignition and enhanced stabilization of a pulverized coal flame. It is shown that this technology, in addition to enhancing the combustion efficiency of the flame, reduces harmful emissions from power coals of all ranks (brown, bituminous, anthracite and their mixtures). Data summarising the experience of 27 pulverized coal boilers in 16 thermal power plants in several countries (Russia, Kazakhstan, Korea, Ukraine, Slovakia, Mongolia and China), embracing steam productivities from 75 to 670 tons per hour (TPH), are presented. Finally, the practical computation of the characteristics of the PFS, as function of coal properties, is discussed.

  15. Combustion Enhancement in Scramjet-Operation of a RBCC Engine

    NASA Astrophysics Data System (ADS)

    Sadatake Tomioka, By; Ryohei Kobayashi; Murakami, Atsuo; Shuichi Ueda; Komuro, Tomoyuki; Katsuhiro Itoh, And

    Combination of a scramjet (supersonic combustion ramjet) flow-pass with embedded rocket engines (the combined system termed as Rocket Based Combined Cycle engine) are expected to be the most effective propulsion system for Booster stage of space launch vehicles. At hypersonic regime, it will be operated at rather high rocket engine output for final acceleration with some Isp gains due to air-breathing effects. In this regime, attaining thrust at this high-speed regime becomes very difficult, so that parallel injection of the fuel for scramjet combustion is favorable as the momentum of the injection can contribute to the thrust production. Thus, embedded rocket chamber was supposed to the operated as fuel rich gas generator at very high output. This configuration was tested at simulated flight Mach number of 7-11 at High Enthalpy Shock Tunnel (HIEST) with detonation tube as the source of the simulated rocket exhaust. However, combustion of the residual fuel in the rocket exhaust with airflow could not be attained. Direct-connect combustor tests were performed to evaluate effectiveness of a combustion enhancement technique termed auxiliary injection, i.e., a portion of fuel to be directly injected into airflow to provide ignition source for the residual fuel. Results of both the engine model tests at HIEST and the direct-connect tests are summarized and presented, and modification to the engine model for combustion enhancement was proposed.

  16. Pressurized chemical-looping combustion of coal with an iron ore-based oxygen carrier

    SciTech Connect

    Xiao, Rui; Song, Min; Zhang, Shuai; Shen, Laihong; Song, Qilei; Lu, Zuoji

    2010-06-15

    Chemical-looping combustion (CLC) is a new combustion technology with inherent separation of CO{sub 2}. Most of the previous investigations on CLC of solid fuels were conducted under atmospheric pressure. A pressurized CLC combined cycle (PCLC-CC) system is proposed as a promising coal combustion technology with potential higher system efficiency, higher fuel conversion, and lower cost for CO{sub 2} sequestration. In this study pressurized CLC of coal with Companhia Valedo Rio Doce (CVRD) iron ore was investigated in a laboratory fixed bed reactor. CVRD iron ore particles were exposed alternately to reduction by 0.4 g of Chinese Xuzhou bituminous coal gasified with 87.2% steam/N{sub 2} mixture and oxidation with 5% O{sub 2} in N{sub 2} at 970 C. The operating pressure was varied between 0.1 MPa and 0.6 MPa. First, control experiments of steam coal gasification over quartz sand were performed. H{sub 2} and CO{sub 2} are the major components of the gasification products, and the operating pressure influences the gas composition. Higher concentrations of CO{sub 2} and lower fractions of CO, CH{sub 4}, and H{sub 2} during the reduction process with CVRD iron ore was achieved under higher pressures. The effects of pressure on the coal gasification rate in the presence of the oxygen carrier were different for pyrolysis and char gasification. The pressurized condition suppresses the initial coal pyrolysis process while it also enhances coal char gasification and reduction with iron ore in steam, and thus improves the overall reaction rate of CLC. The oxidation rates and variation of oxygen carrier conversion are higher at elevated pressures reflecting higher reduction level in the previous reduction period. Scanning electron microscope and energy-dispersive X-ray spectroscopy (SEM-EDX) analyses show that particles become porous after experiments but maintain structure and size after several cycles. Agglomeration was not observed in this study. An EDX analysis demonstrates

  17. Intrinsic and metal-doped gallium oxide based high-temperature oxygen sensors for combustion processes

    NASA Astrophysics Data System (ADS)

    Rubio, Ernesto Javier

    Currently, there is enormous interest in research, development and optimization of the combustion processes for energy harvesting. Recent statistical and economic analyses estimated that by improving the coal-based firing/combustion processes in the power plants, savings up to $450-500 million yearly can be achieved. Advanced sensors and controls capable of withstanding extreme environments such as high temperatures, highly corrosive atmospheres, and high pressures are critical to such efficiency enhancement and cost savings. For instance, optimization of the combustion processes in power generation systems can be achieved by sensing, monitoring and control of oxygen, which is a measure of the completeness of the process and can lead to enhanced efficiency and reduced greenhouse gas emissions. However, despite the fact that there exists a very high demand for advanced sensors, the existing technologies suffer from poor 'response and recovery times' and 'long-term stability.' Motivated by the aforementioned technological challenges, the present work was focused on high-temperature (≥700 °C) oxygen sensors for application in power generation systems. The objective of the present work is to investigate nanostructured gallium oxide (2O3) based sensors for oxygen sensing, where we propose to conduct in-depth exploration of the role of refractory metal (tungsten, W, in this case) doping into 2O 3 to enhance the sensitivity, selectivity, stability ("3S" criteria) and reliability of such sensors while keeping cost economical. Tungsten (W) doped gallium oxide (2O3) thin films were deposited via rf-magnetron co-sputtering of W-metal and Ga2O3-ceramic targets. Films were produced by varying the sputtering power applied to the W-target in order to achieve variable W content into 2O3 films while substrate temperature was kept constant at 500 °C. Chemical composition, chemical valence states, microstructure and crystal structure of as-grown and post-annealed W-doped 2O3

  18. New type of microengine using internal combustion of hydrogen and oxygen

    NASA Astrophysics Data System (ADS)

    Svetovoy, Vitaly B.; Sanders, Remco G. P.; Ma, Kechun; Elwenspoek, Miko C.

    2014-03-01

    Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100 × 100 × 5 μm3 that is using internal combustion of hydrogen and oxygen as part of its working cycle. Water electrolysis driven by short voltage pulses creates an extra pressure of 0.5-4 bar for a time of 100-400 μs in a chamber closed by a flexible membrane. When the pulses are switched off this pressure is released even faster allowing production of mechanical work in short cycles. We provide arguments that this unexpectedly fast pressure decrease is due to spontaneous combustion of the gases in the chamber. This actuator is the first step to truly microscopic combustion engines.

  19. Combustion in a multiburner furnace with selective flow of oxygen

    DOEpatents

    Bool, III, Lawrence E.; Kobayashi, Hisashi

    2004-03-02

    Improved operational characteristics such as improved fuel efficiency, reduction of NOx formation, reduction of the amount of unburned carbon in the ash, and lessened tendency to corrosion at the tube wall, in a multi-burner furnace are obtained by reducing the flow rate of combustion air to the burners and selectively individually feeding oxidant to only some of the burners.

  20. Investigation of spontaneous combustion of hydrogen-oxygen mixture using DSMC simulation

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Sun, Quanhua

    2014-12-01

    Combustion has been widely studied in the literature, but very little work was focused on the microscopic level. In this paper, the DSMC method is applied to simulate the microscopic behavior of the spontaneous combustion of hydrogen oxygen mixture. It is found that the ignition delay time of the mixture depends on many factors, such as the physical size, temperature, pressure, and dilution. Comparison between DSMC and CFD results shows that more atomic hydrogen is consumed through reaction HO2+ H → H2+ O2 at temperature close to the extended second explosion limit due to localized distribution of reactants, which may indicate the importance of microscopic behavior on low temperature combustion.

  1. Experimental and theoretical study of iron and mild steel combustion in oxygen flows

    NASA Astrophysics Data System (ADS)

    El-Rabii, Hazem; Kazakov, Kirill A.; Muller, Maryse

    2017-03-01

    The effects of oxygen flow speed and pressure on the iron and mild steel combustion are investigated experimentally and theoretically. The studied specimens are vertical cylindrical rods subjected to an axial oxygen flow and ignited at the upper end by laser irradiation. Three main stages of the combustion process have been identified experimentally: (1) induction period, during which the rod is heated until an intensive metal oxidation begins at its upper end; (2) static combustion, during which a laminar liquid "cap'' slowly grows on the upper rod end, and, after the liquid cap detachment from the sample; (3) dynamic combustion, which is characterized by a rapid metal consumption and turbulent liquid motions. An analytical description of these stages is given. In particular, a model of the dynamic combustion is constructed based on the turbulent oxygen transport through the liquid metal-oxide flow. This model yields a simple expression for the fraction of metal burned in the process and allows one to calculate the normal propagation speed of the solid metal-liquid interface as a function of the oxygen flow speed and pressure. A comparison of the theory with the experimental results is made, and its potential application is mentioned.

  2. Real gas CFD simulations of hydrogen/oxygen supercritical combustion

    NASA Astrophysics Data System (ADS)

    Pohl, S.; Jarczyk, M.; Pfitzner, M.; Rogg, B.

    2013-03-01

    A comprehensive numerical framework has been established to simulate reacting flows under conditions typically encountered in rocket combustion chambers. The model implemented into the commercial CFD Code ANSYS CFX includes appropriate real gas relations based on the volume-corrected Peng-Robinson (PR) equation of state (EOS) for the flow field and a real gas extension of the laminar flamelet combustion model. The results indicate that the real gas relations have a considerably larger impact on the flow field than on the detailed flame structure. Generally, a realistic flame shape could be achieved for the real gas approach compared to experimental data from the Mascotte test rig V03 operated at ONERA when the differential diffusion processes were only considered within the flame zone.

  3. Combustion Of Porous Graphite Particles In Oxygen Enriched Air

    NASA Technical Reports Server (NTRS)

    Delisle, Andrew J.; Miller, Fletcher J.; Chelliah, Harsha K.

    2003-01-01

    Combustion of solid fuel particles has many important applications, including power generation and space propulsion systems. The current models available for describing the combustion process of these particles, especially porous solid particles, include various simplifying approximations. One of the most limiting approximations is the lumping of the physical properties of the porous fuel with the heterogeneous chemical reaction rate constants [1]. The primary objective of the present work is to develop a rigorous modeling approach that could decouple such physical and chemical effects from the global heterogeneous reaction rates. For the purpose of validating this model, experiments with porous graphite particles of varying sizes and porosity are being performed under normal and micro gravity.

  4. Combustion and Performance Analyses of Coaxial Element Injectors with Liquid Oxygen/Liquid Methane Propellants

    NASA Technical Reports Server (NTRS)

    Hulka, J. R.; Jones, G. W.

    2010-01-01

    Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in a flight-qualified engine system, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented activities with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, the NASA Marshall Space Flight Center has conducted combustion, performance, and combustion stability analyses of several of the configurations. This paper summarizes the analyses of combustion and performance as a follow-up to a paper published in the 2008 JANNAF/LPS meeting. Combustion stability analyses are presented in a separate paper. The current paper includes test and analysis results of coaxial element injectors using liquid oxygen and liquid methane or gaseous methane propellants. Several thrust chamber configurations have been modeled, including thrust chambers with multi-element swirl coax element injectors tested at the NASA MSFC, and a uni-element chamber with shear and swirl coax injectors tested at The Pennsylvania State University. Configurations were modeled with two one-dimensional liquid rocket combustion analysis codes, the Rocket Combustor Interaction Design and Analysis (ROCCID), and the Coaxial Injector Combustion Model (CICM). Significant effort was applied to show how these codes can be used to model combustion and performance with oxygen/methane propellants a priori, and what anchoring or calibrating features need to be applied or developed in the future. This paper describes the test hardware configurations, presents the results of all the analyses, and compares the results from the two analytical methods

  5. Combustion Effects in Laser-oxygen Cutting: Basic Assumptions, Numerical Simulation and High Speed Visualization

    NASA Astrophysics Data System (ADS)

    Zaitsev, Alexander V.; Ermolaev, Grigory V.

    Laser-oxygen cutting is very complicated for theoretical description technological process. Iron-oxygen combustion playing a leading role making it highly effective, able to cut thicker plates and, at the same time, producing special types of striations and other defects on the cut surface. In this paper results of numerical simulation based on elementary assumptions on iron-oxygen combustion are verified with high speed visualization of laser-oxygen cutting process. On a base of assumption that iron oxide lost its protective properties after melting simulation of striation formation due cycles of laser induced non self-sustained combustion is proposed. Assumption that reaction limiting factor is oxygen transport from the jet to cutting front allows to calculate reaction intensity by solving Navier - Stokes and diffusion system in gas phase. Influence of oxygen purity and pressure is studied theoretically. The results of numerical simulation are examined with high speed visualization of laser-oxygen cutting of 4-20 mm mild steel plates at cutting conditions close to industrial.

  6. Oxygen index: An approximate value for the evaluation of combustion characteristics

    NASA Technical Reports Server (NTRS)

    Zartmann, I.; Reinwardt, D.; Franke, A.

    1986-01-01

    The oxygen index has gained international recognition for the determination of combustion characteristics of plastic material. The amounts of oxygen and nitrogen were more accurately determined for existing test equipment in order to specify the oxygen index as precisely and as reproducible as possible. Parameters are outlined such as the size of the ignition flame, ignition of test pieces, test piece sizes and test temperature. The minimum oxygen index was determined by the dimension and duration of the fire. The results are sufficiently accurate for factory operating conditions and are also reproducible.

  7. PROGRESS IN DETAILED KINETIC MODELING OF THE COMBUSTION OF OXYGENATED COMPONENTS OF BIOFUELS

    PubMed Central

    Sy Tran, Luc; Sirjean, Baptiste; Glaude, Pierre-Alexandre; Fournet, René; Battin-Leclerc, Frédérique

    2013-01-01

    Due to growing environmental concerns and diminishing petroleum reserves, a wide range of oxygenated species has been proposed as possible substitutes to fossil fuels: alcohols, methyl esters, acyclic and cyclic ethers. After a short review the major detailed kinetic models already proposed in the literature for the combustion of these molecules, the specific classes of reactions considered for modeling the oxidation of acyclic and cyclic oxygenated molecules respectively, are detailed. PMID:23700355

  8. Experimental and numerical study of PC combustion with oxygen enrichment in a blowpipe model of blast furnace

    SciTech Connect

    Cang Daqiang; Yang Min; Ding Yulong; Yang Tianjun

    1994-12-31

    The method of pulverized coal injection (PCI), oxygen enrichment position, and PC size with oxygen enrichment have been studied to improve of the combustion efficiency of PC by using a theoretical model and experiment. The results showed: (1) by using double coal lance instead of single coal lance in a blowpipe, the combustion efficiency of anthracite can be increased significantly; (2) under the experimental conditions, pure oxygen directly mixed with hot blast is suitable for combustion efficiency when oxygen content is lower then 24%, and when oxygen content is higher, oxygen enrichment location at a proper position of blowpipe away from PC lance should be used; and (3) fine anthracite particle with high oxygen content is an effective way to improve the combustion efficiency of anthracite.

  9. Enhanced efficiency of internal combustion engines by employing spinning gas.

    PubMed

    Geyko, V I; Fisch, N J

    2014-08-01

    The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A remarkable gain in fuel efficiency is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in efficiency.

  10. Enhanced Efficiency of Internal Combustion Engines By Employing Spinning Gas

    SciTech Connect

    Geyko, Vasily; Fisch, Nathaniel

    2014-02-27

    The efficiency of the internal combustion engine might be enhanced by employing spinning gas. A gas spinning at near sonic velocities has an effectively higher heat capacity, which allows practical fuel cycles, which are far from the Carnot efficiency, to approach more closely the Carnot efficiency. A gain in fuel efficiency of several percent is shown to be theoretically possible for the Otto and Diesel cycles. The use of a flywheel, in principle, could produce even greater increases in the efficiency.

  11. FIELD DEMONSTRATION OF THE LINDE OXYGEN COMBUSTION SYSTEM ON THE EPA MOBILE INCINERATOR

    EPA Science Inventory

    This paper summarizes the various system performance tests and the long-term operating experience of the LINDE Oxygen Combustion System installed on the U.S. Environmental Protection Agency's Mobile Incineration System (MIS) when it was in operation at the Denney Farm site in sou...

  12. Experimental study on improving cement quality with oxygen- enriched combustion technology

    NASA Astrophysics Data System (ADS)

    Liu, Y. Q.; Zhang, A. M.; Qing, S.; Li, F. S.; Yang, S. P.; Yang, Z. F.

    2015-12-01

    With the intensification of the global energy crisis, the production cost of enterprises is continuously increasing because of the rising fuel prices and high requirements for environmental protection. As result, energy savings and environmental protection are vital considerations for a variety of enterprises. As a practical energy-saving technology, oxygen- enriched combustion has played a major role in energy saving and emissions reduction as its application in industrial furnaces has been popularized in recent years. This experiment was conducted in a cement rotary kiln with a capacity of 4000 t/d in a factory in China. Based on measured data in the oxygen-enriched combustion experiment, we determined the patterns of variation in the main parameters of the cement rotary kiln under oxygen-enriched production conditions. The results provide important theoretical and practical base for the cement building materials industry in energy saving and emissions reduction.

  13. A mechanistic investigation of a calcium-based oxygen carrier for chemical looping combustion

    SciTech Connect

    Shen, Laihong; Zheng, Min; Xiao, Jun; Xiao, Rui

    2008-08-15

    Chemical looping combustion (CLC) has been suggested as an energy-efficient method for the capture of carbon dioxide from combustion. It is indirect combustion by the use of an oxygen carrier, which can be used for CO{sub 2} capture in power-generating processes. The possibility of CLC using a calcium-based oxygen carrier is investigated in this paper. In the air reactor air is supplied to oxidize CaS to CaSO{sub 4}, where oxygen is transferred from air to the oxygen carrier; the reduction of CaSO{sub 4} to CaS takes place in the fuel reactor. The exit gas from the fuel reactor is CO{sub 2} and H{sub 2}O. After condensation of water, almost pure CO{sub 2} could be obtained. The thermodynamic and kinetic problem of the reduction reactions of CaSO{sub 4} with CO and H{sub 2} and the oxidization reactions of CaS with O{sub 2} is discussed in the paper to investigate the technique possibility. To prevent SO{sub 2} release from the process of chemical looping combustion using a calcium-based oxygen carrier, thermochemical CaSO{sub 4} reduction and CaS oxidation are discussed. Thermal simulation experiments are carried out using a thermogravimetric analyzer (TGA). The properties of the products are characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffractometry (XRD), and the optimal reaction parameters are evaluated. The effects of reaction temperature, reductive gas mixture, and oxygen partial pressure on the composition of flue gas are discussed. The suitable temperature of the air reactor is between 1050 and 1150 C and the optimal temperature of the fuel reactor between 900 and 950 C. (author)

  14. Use of coal as fuel for chemical-looping combustion with Ni-based oxygen carrier

    SciTech Connect

    Gao, Z.P.; Shen, L.H.; Xiao, J.; Qing, C.J.; Song, Q.L.

    2008-12-15

    Chemical-looping combustion is an indirect combustion technology with inherent separation of the greenhouse gas CO{sub 2}. The feasibility of using NiO as an oxygen carrier during chemical-looping combustion of coal has been investigated experimentally at 800-960{degree}C in the present work. The experiments were carried out in a fluidized bed, where the steam acted as the gasification-fluidization medium. Coal gasification and the reaction of oxygen carrier with the water gas take place simultaneously in the reactor. The oxygen carrier particles exhibit high reactivity above 900{degree}C, and the dry basis concentration of CO{sub 2} in the exit gas of the reactor is nearly 95%. The flue gas composition as a function of the reactor temperature and cyclic reduction number is discussed. At 800-960{degree}C, the dry basis concentration of CO{sub 2} in the flue gas presents a monotonously increasing trend, whereas the dry basis concentration of CO, H{sub 2}, and CH{sub 4} decreases monotonously. The concentrations of CO{sub 2}, CO, H{sub 2}, and CH{sub 4} in the flue gas as a function of cyclic reduction number present a para-curve characteristic at 900{degree}C. With the increase of cyclic reduction number, the dry basis concentration of CO{sub 2} decreases remarkably, while the dry basis concentrations of CO, H{sub 2}, and CH{sub 4} increase rapidly. Moreover, the peak value of H{sub 2} concentration is less than that of CO. The performance of the NiO-based oxygen carriers was also evaluated using an X-ray diffractometer and a scanning electron microscope to characterize the solid residues of oxygen carrier. The results indicate that NiO is one of the suitable oxygen carriers for chemical-looping combustion of coal.

  15. Performance and Stability Analyses of Rocket Combustion Devices Using Liquid Oxygen/Liquid Methane Propellants

    NASA Technical Reports Server (NTRS)

    Hulka, James R.; Jones, G. W.

    2010-01-01

    Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in flight-qualified engine systems, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented programs with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, NASA Marshall Space Flight Center has conducted combustion, performance, and combustion stability analyses of several of the configurations on these programs. This paper summarizes these analyses. Test and analysis results of impinging and coaxial element injectors using liquid oxygen and liquid methane propellants are included. Several cases with gaseous methane are included for reference. Several different thrust chamber configurations have been modeled, including thrust chambers with multi-element like-on-like and swirl coax element injectors tested at NASA MSFC, and a unielement chamber with shear and swirl coax injectors tested at The Pennsylvania State University. Configurations were modeled with two one-dimensional liquid rocket combustion analysis codes, the Rocket Combustor Interaction Design and Analysis (ROCCID), and the Coaxial Injector Combustion Model (CICM). Significant effort was applied to show how these codes can be used to model combustion and performance with oxygen/methane propellants a priori, and what anchoring or calibrating features need to be applied or developed in the future. This paper describes the test hardware configurations, presents the results of all the analyses, and compares the results from the two analytical methods.

  16. Carbon dioxide remediation via oxygen-enriched combustion using dense ceramic membranes

    DOEpatents

    Balachandran, Uthamalingam; Bose, Arun C.; McIlvried, Howard G.

    2001-01-01

    A method of combusting pulverized coal by mixing the pulverized coal and an oxidant gas to provide a pulverized coal-oxidant gas mixture and contacting the pulverized coal-oxidant gas mixture with a flame sufficiently hot to combust the mixture. An oxygen-containing gas is passed in contact with a dense ceramic membrane of metal oxide material having electron conductivity and oxygen ion conductivity that is gas-impervious until the oxygen concentration on one side of the membrane is not less than about 30% by volume. An oxidant gas with an oxygen concentration of not less than about 30% by volume and a CO.sub.2 concentration of not less than about 30% by volume and pulverized coal is contacted with a flame sufficiently hot to combust the mixture to produce heat and a flue gas. One dense ceramic membrane disclosed is selected from the group consisting of materials having formulae SrCo.sub.0.8 Fe.sub.0.2 O.sub.x, SrCo.sub.0.5 FeO.sub.x and La.sub.0.2 Sr.sub.0.8 Co.sub.0.4 Fe.sub.0.6 O.sub.x.

  17. Investigation of spontaneous combustion of hydrogen-oxygen mixture using DSMC simulation

    SciTech Connect

    Yang, Chao; Sun, Quanhua

    2014-12-09

    Combustion has been widely studied in the literature, but very little work was focused on the microscopic level. In this paper, the DSMC method is applied to simulate the microscopic behavior of the spontaneous combustion of hydrogen oxygen mixture. It is found that the ignition delay time of the mixture depends on many factors, such as the physical size, temperature, pressure, and dilution. Comparison between DSMC and CFD results shows that more atomic hydrogen is consumed through reaction HO{sub 2}+H→H{sub 2}+O{sub 2} at temperature close to the extended second explosion limit due to localized distribution of reactants, which may indicate the importance of microscopic behavior on low temperature combustion.

  18. A Preliminary Study on the Toxic Combustion Products Testing of Polymers Used in High-Pressure Oxygen Systems

    NASA Technical Reports Server (NTRS)

    Hshieh, Fu-Yu; Beeson, Harold D.

    2004-01-01

    One likely cause of polymer ignition in a high-pressure oxygen system is adiabatic-compression heating of polymers caused by pneumatic impact. Oxidative _ pyrolysis or combustion of polymers in a high-pressure oxygen system could generate toxic gases. This paper reports the preliminary results of toxic combustion product testing of selected polymers in a pneumatic-impact test system. Five polymers commonly used in high-pressure oxygen systems, Nylon 6/6, polychlorotrifluoroethylene (CTFE), polytetrafluoroethylene (PTFE), fluoroelastomer (Viton(TradeMark) A), and nitrile rubber (Buna N), were tested in a pneumatic-impact test system at 2500- or 3500-psia oxygen pressure. The polymers were ignited and burned, then combustion products were collected in a stainless-steel sample bottle and analyzed by GC/MS/IRD, GC/FID, and GC/Methanizer/FID. The results of adiabatic-compression tests show that combustion of hydrocarbon polymers, nitrogen-containing polymers, and halogenated polymers in high-pressure oxygen systems are relatively complete. Toxicity of the combustion product gas is presumably much lower than the combustion product gas generated from ambient-pressure oxygen (or air) environments. The NASA-Lewis equilibrium code was used to determine the composition of combustion product gas generated from a simulated, adiabatic-compression test of nine polymers. The results are presented and discussed.

  19. Injector characterization for a gaseous oxygen-methane single element combustion chamber

    NASA Astrophysics Data System (ADS)

    Celano, M. P.; Silvestri, S.; Schlieben, G.; Kirchberger, C.; Haidn, O. J.; Knab, O.

    2016-07-01

    The results from an experimental investigation on an oxygen-methane single-injector combustion chamber are presented. They provide detailed information about the thermal loads at the hot inner walls of the combustion chamber at representative rocket engine conditions and pressures up to 20 bar. The present study aims to contribute to the understanding of the thermal transfer processes and to validate the in-house design tool Thermtest and a base for an attempt to simulate the flame behavior with large-eddy simulation (LES). Due to the complex flow phenomena linked to the use of cryogenic propellants, like extreme variation of flow properties and steep temperature gradients, in combination with intensive chemical reactions, the problem has been partially simplified by injecting gaseous oxygen (GOx) and gaseous methane (GCH4).

  20. New type of microengine using internal combustion of hydrogen and oxygen.

    PubMed

    Svetovoy, Vitaly B; Sanders, Remco G P; Ma, Kechun; Elwenspoek, Miko C

    2014-03-06

    Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100 × 100 × 5 μm(3) that is using internal combustion of hydrogen and oxygen as part of its working cycle. Water electrolysis driven by short voltage pulses creates an extra pressure of 0.5-4 bar for a time of 100-400 μs in a chamber closed by a flexible membrane. When the pulses are switched off this pressure is released even faster allowing production of mechanical work in short cycles. We provide arguments that this unexpectedly fast pressure decrease is due to spontaneous combustion of the gases in the chamber. This actuator is the first step to truly microscopic combustion engines.

  1. New type of microengine using internal combustion of hydrogen and oxygen

    PubMed Central

    Svetovoy, Vitaly B.; Sanders, Remco G. P.; Ma, Kechun; Elwenspoek, Miko C.

    2014-01-01

    Microsystems become part of everyday life but their application is restricted by lack of strong and fast motors (actuators) converting energy into motion. For example, widespread internal combustion engines cannot be scaled down because combustion reactions are quenched in a small space. Here we present an actuator with the dimensions 100 × 100 × 5 μm3 that is using internal combustion of hydrogen and oxygen as part of its working cycle. Water electrolysis driven by short voltage pulses creates an extra pressure of 0.5–4 bar for a time of 100–400 μs in a chamber closed by a flexible membrane. When the pulses are switched off this pressure is released even faster allowing production of mechanical work in short cycles. We provide arguments that this unexpectedly fast pressure decrease is due to spontaneous combustion of the gases in the chamber. This actuator is the first step to truly microscopic combustion engines. PMID:24599052

  2. Emission of Oxygenated Polycyclic Aromatic Hydrocarbons from Indoor Solid Fuel Combustion

    PubMed Central

    Shen, Guofeng; Tao, Shu; Wang, Wei; Yang, Yifeng; Ding, Junnan; Xue, Miao; Min, Yujia; Zhu, Chen; Shen, Huizhong; Li, Wei; Wang, Bin; Wang, Rong; Wang, Wentao; Wang, Xilong; Russell, Armistead G.

    2011-01-01

    Indoor solid fuel combustion is a dominant source of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (OPAHs) and the latter are believed to be more toxic than the former. However, there is limited quantitative information on the emissions of OPAHs from solid fuel combustion. In this study, emission factors of OPAHs (EFOPAH) for nine commonly used crop residues and five coals burnt in typical residential stoves widely used in rural China were measured under simulated kitchen conditions. The total EFOPAH ranged from 2.8±0.2 to 8.1±2.2 mg/kg for tested crop residues and from 0.043 to 71 mg/kg for various coals and 9-fluorenone was the most abundant specie. The EFOPAH for indoor crop residue burning were 1~2 orders of magnitude higher than those from open burning, and they were affected by fuel properties and combustion conditions, like moisture and combustion efficiency. For both crop residues and coals, significantly positive correlations were found between EFs for the individual OPAHs and the parent PAHs. An oxygenation rate, Ro, was defined as the ratio of the EFs between the oxygenated and parent PAH species to describe the formation potential of OPAHs. For the studied OPAH/PAH pairs, mean Ro values were 0.16 ~ 0.89 for crop residues and 0.03 ~ 0.25 for coals. Ro for crop residues burned in the cooking stove were much higher than those for open burning and much lower than those in ambient air, indicating the influence of secondary formation of OPAH and loss of PAHs. In comparison with parent PAHs, OPAHs showed a higher tendency to be associated with particulate matter (PM), especially fine PM, and the dominate size ranges were 0.7 ~ 2.1 µm for crop residues and high caking coals and < 0.7 µm for the tested low caking briquettes. PMID:21375317

  3. Chemical looping combustion of biomass-derived syngas using ceria-supported oxygen carriers.

    PubMed

    Huang, H B; Aisyah, L; Ashman, P J; Leung, Y C; Kwong, C W

    2013-07-01

    Cu, Ni and Fe oxides supported on ceria were investigated for their performance as oxygen carriers during the chemical looping combustion of biomass-derived syngas. A complex gas mixture containing CO, H2, CO2, CH4 and other hydrocarbons was used to simulate the complex fuel gas environment derived from biomass gasification. Results show that the transfer of the stored oxygen into oxidants for the supported Cu and Ni oxides at 800°C for the combustion of syngas was effective (>85%). The unsupported Cu oxide showed high oxygen carrying capacity but particle sintering was observed at 800°C. A reaction temperature of 950°C was required for the supported Fe oxides to transfer the stored oxygen into oxidants effectively. Also, for the complex fuel gas environment, the supported Ni oxide was somewhat effective in reforming CH4 and other light hydrocarbons into CO, which may have benefits for the reduction of tar produced during biomass pyrolysis.

  4. Photographic Study of Combustion in a Rocket Engine I : Variation in Combustion of Liquid Oxygen and Gasoline with Seven Methods of Propellant Injection

    NASA Technical Reports Server (NTRS)

    Bellman, Donald R; Humphrey, Jack C

    1948-01-01

    Motion pictures at camera speeds up to 3000 frames per second were taken of the combustion of liquid oxygen and gasoline in a 100-pound-thrust rocket engine. The engine consisted of thin contour and injection plates clamped between two clear plastic sheets forming a two-dimensional engine with a view of the entire combustion chamber and nozzle. A photographic investigation was made of the effect of seven methods of propellant injection on the uniformity of combustion. From the photographs, it was found that the flame front extended almost to the faces of the injectors with most of the injection methods, all the injection systems resulted in a considerable nonuniformity of combustion, and luminosity rapidly decreased in the divergent part of the nozzle. Pressure vibration records indicated combustion vibrations that approximately corresponded to the resonant frequencies of the length and the thickness of the chamber. The combustion temperature divided by the molecular weight of the combustion gases as determined from the combustion photographs was about 50 to 70 percent of the theoretical value.

  5. Oxygen bomb combustion of biological samples for inductively coupled plasma optical emission spectrometry

    NASA Astrophysics Data System (ADS)

    Souza, Gilberto B.; Carrilho, Elma Neide V. M.; Oliveira, Camila V.; Nogueira, Ana Rita A.; Nóbrega, Joaquim A.

    2002-12-01

    A rapid sample preparation method is proposed for decomposition of milk powder, corn bran, bovine and fish tissues, containing certified contents of the analytes. The procedure involves sample combustion in a commercial stainless steel oxygen bomb operating at 25 bar. Most of the samples were decomposed within 5 min. Diluted nitric acid or water-soluble tertiary amines 10% v/v were used as absorption solutions. Calcium, Cu, K, Mg, Na, P, S and Zn were recovered with the bomb washings and determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Ethanol mixed with paraffin was used as a combustion aid to allow complete combustion. A cooling step prior releasing of the bomb valve was employed to increase the efficiency of sample combustion. Iodine was also determined in milk samples spiked with potassium iodide to evaluate the volatilization and collection of iodine in amine CFA-C medium and the feasibility of its determination by ICP-OES with axial view configuration. Most of the element recoveries in the samples were between 91 and 105% and the certified and found contents exhibited a fair agreement at a 95% confidence level.

  6. Combustion Stability Analyses of Coaxial Element Injectors with Liquid Oxygen/Liquid Methane Propellants

    NASA Technical Reports Server (NTRS)

    Hulka, J. R.

    2010-01-01

    Liquid rocket engines using oxygen and methane propellants are being considered by the National Aeronautics and Space Administration (NASA) for in-space vehicles. This propellant combination has not been previously used in a flight-qualified engine system, so limited test data and analysis results are available at this stage of early development. NASA has funded several hardware-oriented activities with oxygen and methane propellants over the past several years with the Propulsion and Cryogenic Advanced Development (PCAD) project, under the Exploration Technology Development Program. As part of this effort, the NASA Marshall Space Flight Center has conducted combustion stability analyses of several of the configurations. This paper presents test data and analyses of combustion stability from the recent PCAD-funded test programs at the NASA MSFC. These test programs used swirl coaxial element injectors with liquid oxygen and liquid methane propellants. Oxygen was injected conventionally in the center of the coaxial element, and swirl was provided by tangential entry slots. Injectors with 28-element and 40-element patterns were tested with several configurations of combustion chambers, including ablative and calorimeter spool sections, and several configurations of fuel injection design. Low frequency combustion instability (chug) occurred with both injectors, and high-frequency combustion instability occurred at the first tangential (1T) transverse mode with the 40-element injector. In most tests, a transition between high-amplitude chug with gaseous methane flow and low-amplitude chug with liquid methane flow was readily observed. Chug analyses of both conditions were conducted using techniques from Wenzel and Szuch and from the Rocket Combustor Interactive Design and Analysis (ROCCID) code. The 1T mode instability occurred in several tests and was apparent by high-frequency pressure measurements as well as dramatic increases in calorimeter-measured heat flux

  7. Selective Coke Combustion by Oxygen Pulsing During Mo/ZSM‐5‐Catalyzed Methane Dehydroaromatization

    PubMed Central

    Coumans, Ferdy J. A. G.; Uslamin, Evgeny; Kapteijn, Freek

    2016-01-01

    Abstract Non‐oxidative methane dehydroaromatization is a promising reaction to directly convert natural gas into aromatic hydrocarbons and hydrogen. Commercialization of this technology is hampered by rapid catalyst deactivation because of coking. A novel approach is presented involving selective oxidation of coke during methane dehydroaromatization at 700 °C. Periodic pulsing of oxygen into the methane feed results in substantially higher cumulative product yield with synthesis gas; a H2/CO ratio close to two is the main side‐product of coke combustion. Using 13C isotope labeling of methane it is demonstrated that oxygen predominantly reacts with molybdenum carbide species. The resulting molybdenum oxides catalyze coke oxidation. Less than one‐fifth of the available oxygen reacts with gaseous methane. Combined with periodic regeneration at 550 °C, this strategy is a significant step forward, towards a process for converting methane into liquid hydrocarbons. PMID:27791321

  8. A Brief Study on Toxic Combustion Products of the Polymers Used in High-Pressure Oxygen Systems

    NASA Technical Reports Server (NTRS)

    Hshieh, Fu-Yu; Beeson, Harold D.

    2005-01-01

    One likely cause of polymer ignition in a high-pressure oxygen system is the adiabatic-compression heating of polymers caused by pneumatic impact. Oxidative pyrolysis or combustion of polymers in a high-pressure oxygen system could generate toxic gases. This paper investigates the feasibility of using the NASA pneumatic-impact system to conduct adiabatic-compression combustion tests and determines the toxic combustion products produced from the burning of five selected polymers. Five polymers commonly used in high-pressure oxygen systems, Zytel(Registered TradeMark) 42 (Nylon 6/6), Buna N (nitrile rubber), Witon(Registered TradeMark) A (copolymer of vinylidene fluoride and hexafluoropropylene), Neoflon(Registered TradeMark) (polychlorotrifluoroethylene), and Teflon(Registered TradeMark) (polytetrafluoroethylene), were tested in the NASA pneumatic-impact test system at 17.2-MPa oxygen pressure. The polymers were ignited and burned; combustion products were collected in a stainless-steel sample bottle and analyzed using various methods. The results show that the NASA pneumatic-impact system is an appropriate test system to conduct adiabatic-compression combustion tests and to collect combustion products for further chemical analysis. The composition of the combustion product gas generated from burning the five selected polymers are presented and discussed.

  9. Functionalized graphene sheet colloids for enhanced fuel/propellant combustion.

    PubMed

    Sabourin, Justin L; Dabbs, Daniel M; Yetter, Richard A; Dryer, Frederick L; Aksay, Ilhan A

    2009-12-22

    We have compared the combustion of the monopropellant nitromethane with that of nitromethane containing colloidal particles of functionalized graphene sheets or metal hydroxides. The linear steady-state burning rates of the monopropellant and colloidal suspensions were determined at room temperature, under a range of pressures (3.35-14.4 MPa) using argon as a pressurizing fluid. The ignition temperatures were lowered and burning rates increased for the colloidal suspensions compared to those of the liquid monopropellant alone, with the graphene sheet suspension having significantly greater burning rates (i.e., greater than 175%). The relative change in burning rate from neat nitromethane increased with increasing concentrations of fuel additives and decreased with increasing pressure until at high pressures no enhancement was found.

  10. Effect of temperature on reduction of CaSO{sub 4} oxygen carrier in chemical-looping combustion of simulated coal gas in a fluidized bed reactor

    SciTech Connect

    Song, Q.L.; Xiao, R.; Deng, Z.Y.; Shen, L.H.; Xiao, J.; Zhang, M.Y.

    2008-12-15

    Chemical-looping combustion (CLC) is a promising combustion technology for gaseous and solid fuel with efficient use of energy and inherent separation of CO{sub 2}. The concept of a coal-fueled CLC system using, calcium sulfate (CaSO{sub 4}) as oxygen carrier is proposed in this study. Reduction tests of CaSO{sub 4} oxygen carrier with simulated coal gas were performed in a laboratory-scale fluidized bed reactor in the temperature range of 890-950{degree}C. A high concentration of CO{sub 2} was obtained at the initial reduction period. CaSO{sub 4} oxygen carrier exhibited high reactivity initially and decreased gradually at the late period of reduction. The sulfur release during the reduction of CaSO{sub 4} as oxygen carrier was also observed and analyzed. H{sub 2} and CO{sub 2} conversions were greatly influenced by reduction temperature. The oxygen carrier conversion and mass-based reaction rates during the reduction at typical temperatures were compared. Higher temperatures would enhance reaction rates and result in high conversion of oxygen carrier. An XRD patterns study indicated that CaS was the dominant product of reduction and the variation of relative intensity with temperature is in agreement with the solid conversion. ESEM analysis indicated that the surface structure of oxygen carrier particles changed significantly from impervious to porous after reduction. EDS analysis also demonstrated the transfer of oxygen from the oxygen carrier to the fuel gas and a certain amount of sulfur loss and CaO formation on the surface at higher temperatures. The reduction kinetics of CaSO{sub 4} oxygen carrier was explored with the shrinking unreacted-core model. The apparent kinetic parameters were obtained, and the kinetic equation well predicted the experimental data. Finally, some basic considerations on the use of CaSO{sub 4} oxygen carrier in a CLC system for solid fuels were discussed.

  11. Reduction Kinetics of a CasO4 Based Oxygen Carrier for Chemical-Looping Combustion

    NASA Astrophysics Data System (ADS)

    Xiao, R.; Song, Q. L.; Zheng, W. G.; Deng, Z. Y.; Shen, L. H.; Zhang, M. Y.

    The CaSO4 based oxygen carrier has been proposed as an alternative low cost oxygen carrier for Chemical-looping combustion (CLC) of coal. The reduction of CaSO4 to CaS is an important step for the cyclic process of reduction/oxidation in CLC of coal with CaSO4 based oxygen carrier. Thermodynamic analysis of CaSO4 oxygen carrier with CO based on the principle of Gibbs free energy minimization show that the essentially high purity of CO2 can be obtained, while the solid product is CaS instead of CaO. The intrinsic reduction kinetics of a CaSO4 based oxygen carrier with CO was investigated in a differential fixed bed reactor. The effects of gas partial pressure (20%-70%) and temperature (880-950°C) on the reduction were investigated. The reduction was described with shrinking unreacted core model. Experimental results of CO partial pressure on the solid conversion show that the reduction of fresh oxygen carriers is of first order with respect to the CO partial pressure. Both chemical reaction control and product layer diffusion control determine the reduction rate. The dependences of reaction rate constant and effective diffusivity with temperature were both obtained. The kinetic equation well predicted the experimental data.

  12. Chemicl-looping combustion of coal with metal oxide oxygen carriers

    SciTech Connect

    Siriwardane, R.; Tian, H.; Richards, G.; Simonyi, T.; Poston, J.

    2009-01-01

    The combustion and reoxidation properties of direct coal chemical-looping combustion (CLC) over CuO, Fe2O3, Co3O4, NiO, and Mn2O3 were investigated using thermogravimetric analysis (TGA) and bench-scale fixed-bed flow reactor studies. When coal is heated in either nitrogen or carbon dioxide (CO2), 50% of weight loss was observed because of partial pyrolysis, consistent with the proximate analysis. Among various metal oxides evaluated, CuO showed the best reaction properties: CuO can initiate the reduction reaction as low as 500 °C and complete the full combustion at 700 °C. In addition, the reduced copper can be fully reoxidized by air at 700 °C. The combustion products formed during the CLC reaction of the coal/metal oxide mixture are CO2 and water, while no carbon monoxide was observed. Multicycle TGA tests and bench-scale fixed-bed flow reactor tests strongly supported the feasibility of CLC of coal by using CuO as an oxygen carrier. Scanning electron microscopy (SEM) images of solid reaction products indicated some changes in the surface morphology of a CuO-coal sample after reduction/oxidation reactions at 800 °C. However, significant surface sintering was not observed. The interactions of fly ash with metal oxides were investigated by X-ray diffraction and thermodynamic analysis. Overall, the results indicated that it is feasible to develop CLC with coal by metal oxides as oxygen carriers.

  13. Chemical-looping combustion of coal with metal oxide oxygen carriers

    SciTech Connect

    Ranjani Siriwardane; Hanjing Tian; George Richards; Thomas Simonyi; James Poston

    2009-08-15

    The combustion and reoxidation properties of direct coal chemical-looping combustion (CLC) over CuO, Fe{sub 2}O{sub 3}, CO{sub 3}O{sub 4}, NiO, and Mn{sub 2}O{sub 3} were investigated using thermogravimetric analysis (TGA) and bench-scale fixed-bed flow reactor studies. When coal is heated in either nitrogen or carbon dioxide (CO{sub 2}), 50% of weight loss was observed because of partial pyrolysis, consistent with the proximate analysis. Among various metal oxides evaluated, CuO showed the best reaction properties: CuO can initiate the reduction reaction as low as 500{sup o}C and complete the full combustion at 700{sup o}C. In addition, the reduced copper can be fully reoxidized by air at 700{sup o}C. The combustion products formed during the CLC reaction of the coal/metal oxide mixture are CO{sub 2} and water, while no carbon monoxide was observed. Multicycle TGA tests and bench-scale fixed-bed flow reactor tests strongly supported the feasibility of CLC of coal by using CuO as an oxygen carrier. Scanning electron microscopy (SEM) images of solid reaction products indicated some changes in the surface morphology of a CuO-coal sample after reduction/oxidation reactions at 800 {sup o}C. However, significant surface sintering was not observed. The interactions of fly ash with metal oxides were investigated by X-ray diffraction and thermodynamic analysis. Overall, the results indicated that it is feasible to develop CLC with coal by metal oxides as oxygen carriers. 22 refs., 12 figs., 2 tabs.

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

    SciTech Connect

    Gehmlich, Ryan K.; Dumitrescu, Cosmin E.; Wang, Yefu; Mueller, Charles J.

    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/or 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

  15. 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

  16. Nanocomposite oxygen carriers for chemical-looping combustion of sulfur-contaminated synthesis gas

    SciTech Connect

    Rahul D. Solunke; Goetz Veser

    2009-09-15

    Chemical-looping combustion (CLC) is an emerging technology for clean combustion. We have previously demonstrated that the embedding of metal nanoparticles into a nanostructured ceramic matrix can result in unusually active and sinter-resistant nanocomposite oxygen carrier materials for CLC, which combine the high reactivity of metals with the high-temperature stability of ceramics. In the present study, we investigate the effect of H{sub 2}S in a typical coal-derived syngas on the stability and redox kinetics of Ni- and Cu-based nanostructured oxygen carriers. Both carriers show excellent structural stability and only mildly changed redox kinetics upon exposure to H{sub 2}S, despite a significant degree of sulfide formation. Surprisingly, partial sulfidation of the support results in a strong increase in oxygen carrier capacity in both cases because of the addition of a sulfide-sulfate cycle. Overall, the carriers show great potential for use in CLC of high-sulfur fuels. 21 refs., 13 figs. 1 tab.

  17. Corrosion prevention in copper combustion chamber liners of liquid oxygen/methane booster engines

    NASA Technical Reports Server (NTRS)

    Rosenberg, S. D.; Gage, M. L.

    1990-01-01

    The use of a protective gold coating for preventing the corrosion of copper combustion chamber liners in liquid oxygen/methane booster engines is discussed with reference to experimental results. Gold-plated and unplated copper alloy specimens were tested in a carbothermal test facility providing realistic simulations of booster engine cooling channel conditions, such as temperature, pressure, flow velocity, and heat flux. Metallographic examinations of the unplated specimens showed severe corrosion as a result of the reaction with the sulfur-containing contaminant in the fuel. In contrast, gold-plated specimens showed no corrosion under similar operating conditions.

  18. Metal ferrite oxygen carriers for chemical looping combustion of solid fuels

    DOEpatents

    Siriwardane, Ranjani V.; Fan, Yueying

    2017-01-31

    The disclosure provides a metal ferrite oxygen carrier for the chemical looping combustion of solid carbonaceous fuels, such as coal, coke, coal and biomass char, and the like. The metal ferrite oxygen carrier comprises MFe.sub.xO.sub.y on an inert support, where MFe.sub.xO.sub.y is a chemical composition and M is one of Mg, Ca, Sr, Ba, Co, Mn, and combinations thereof. For example, MFe.sub.xO.sub.y may be one of MgFe.sub.2O.sub.4, CaFe.sub.2O.sub.4, SrFe.sub.2O.sub.4, BaFe.sub.2O.sub.4, CoFe.sub.2O.sub.4, MnFeO.sub.3, and combinations thereof. The MFe.sub.xO.sub.y is supported on an inert support. The inert support disperses the MFe.sub.xO.sub.y oxides to avoid agglomeration and improve performance stability. In an embodiment, the inert support comprises from about 5 wt. % to about 60 wt. % of the metal ferrite oxygen carrier and the MFe.sub.xO.sub.y comprises at least 30 wt. % of the metal ferrite oxygen carrier. The metal ferrite oxygen carriers disclosed display improved reduction rates over Fe.sub.2O.sub.3, and improved oxidation rates over CuO.

  19. Variable oxygen/nitrogen enriched intake air system for internal combustion engine applications

    DOEpatents

    Poola, Ramesh B.; Sekar, Ramanujam R.; Cole, Roger L.

    1997-01-01

    An air supply control system for selectively supplying ambient air, oxygen enriched air and nitrogen enriched air to an intake of an internal combustion engine includes an air mixing chamber that is in fluid communication with the air intake. At least a portion of the ambient air flowing to the mixing chamber is selectively diverted through a secondary path that includes a selectively permeable air separating membrane device due a differential pressure established across the air separating membrane. The permeable membrane device separates a portion of the nitrogen in the ambient air so that oxygen enriched air (permeate) and nitrogen enriched air (retentate) are produced. The oxygen enriched air and the nitrogen enriched air can be selectively supplied to the mixing chamber or expelled to atmosphere. Alternatively, a portion of the nitrogen enriched air can be supplied through another control valve to a monatomic-nitrogen plasma generator device so that atomic nitrogen produced from the nitrogen enriched air can be then injected into the exhaust of the engine. The oxygen enriched air or the nitrogen enriched air becomes mixed with the ambient air in the mixing chamber and then the mixed air is supplied to the intake of the engine. As a result, the air being supplied to the intake of the engine can be regulated with respect to the concentration of oxygen and/or nitrogen.

  20. Carbon monoxide and oxygen combustion experiments: A demonstration of Mars in situ propellants

    NASA Technical Reports Server (NTRS)

    Linne, Diane L.

    1991-01-01

    The feasibility of using carbon monoxide and oxygen as rocket propellants was examined both experimentally and theoretically. The steady-state combustion of carbon monoxide and oxygen was demonstrated for the first time in a subscale rocket engine. Measurements of experimental characteristic velocity, vacuum specific impulse, and thrust coefficient efficiency were obtained over a mixture ratio range of 0.30 to 2.0 and a chamber pressures of 1070 and 530 kPa. The theoretical performance of the propellant combination was studied parametrically over the same mixture ratio range. In addition to one dimensional ideal performance predictions, various performance reduction mechanisms were also modeled, including finite-rate kinetic reactions, two-dimensional divergence effects and viscous boundary layer effects.

  1. Oxygen carrier development for chemical looping combustion of coal derived synthesis gas

    SciTech Connect

    Siriwardane, R.V.; Chaudhari, K.; Zinn, A.N.; Simonyi, T.; Robinson, Clark; Poston, J.A.

    2006-09-01

    In the present work, NETL researchers have studied chemical looping combustion (CLC) with an oxygen carrier NiO/bentonite (60 wt.% NiO) for the IGCC systems utilizing simulated synthesis gas. Multi cycle CLC was conducted with NiO/Bentonite in TGA at atmospheric pressure and in a high pressure reactor in a temperature range between 700-900°C. Global reaction rates of reduction and oxidation as a function of conversion were calculated for all oxidation-reduction cycles utilizing the TGA data. The effect of particle size of the oxygen carrier on CLC was studied for the size between 20-200 mesh. The multi cycle CLC tests conducted in a high pressure packed bed flow reactor indicated constant total production of CO2 from fuel gas at 800°C and 900°C and full consumption of hydrogen during the reaction.

  2. Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen/Liquid Methane Main Engine

    NASA Technical Reports Server (NTRS)

    Melcher, J. C.; Morehead, Robert L.

    2014-01-01

    The Project Morpheus liquid oxygen (LOX) / liquid methane rocket engines demonstrated acousticcoupled combustion instabilities during sea-level ground-based testing at the NASA Johnson Space Center (JSC) and Stennis Space Center (SSC). High-amplitude, 1T, 1R, 1T1R (and higher order) modes appear to be triggered by injector conditions. The instability occurred during the Morpheus-specific engine ignition/start sequence, and did demonstrate the capability to propagate into mainstage. However, the instability was never observed to initiate during mainstage, even at low power levels. The Morpheus main engine is a JSC-designed 5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. Two different engine designs, named HD4 and HD5, and two different builds of the HD4 engine all demonstrated similar instability characteristics. Through the analysis of more than 200 hot fire tests on the Morpheus vehicle and SSC test stand, a relationship between ignition stability and injector/chamber pressure was developed. The instability has the distinct characteristic of initiating at high relative injection pressure drop (dP) at low chamber pressure (Pc); i.e., instabilities initiated at high dP/Pc at low Pc during the start sequence. The high dP/Pc during start results during the injector /chamber chill-in, and is enhanced by hydraulic flip in the injector orifice elements. Because of the fixed mixture ratio of the existing engine design (the main valves share a common actuator), it is not currently possible to determine if LOX or methane injector dP/Pc were individual contributors (i.e., LOX and methane dP/Pc typically trend in the same direction within a given test). The instability demonstrated initiation characteristic of starting at or shortly after methane injector chillin. Colder methane (e.g., sub-cooled) at the injector inlet prior to engine start was much more likely to result in an instability. A secondary effect of LOX

  3. Numerical Investigation of Combustion and Flow Dynamics in a High Velocity Oxygen-Fuel Thermal Spray Gun

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoguang; Song, Qiuzhi; Yu, Zhiyi

    2016-02-01

    The combustion and flow behavior within a high velocity oxygen-fuel (HVOF) thermal spray gun is very complex and involves multiphase flow, heat transfer, chemical reactions, and supersonic/subsonic transitions. Additionally, this behavior has a significant effect on the formation of a coating. Non-premixed combustion models have been developed and are able to provide insight into the underlying physics of the process. Therefore, this investigation employs a non-premixed combustion model and the SST k - ω turbulence model to simulate the flow field of the JP5000 (Praxair-TAFA, US) HVOF thermal spray gun. The predicted temperature and velocity have a high level of agreement with experimental data when using the non-premixed combustion model. The results are focused on the fuel combustion, the subsequent gas dynamics within the HVOF gun, and the development of a supersonic free jet outside the gun. Furthermore, the oxygen/fuel inlet turbulence intensity, the fuel droplet size, and the oxygen/fuel ratio are investigated to determine their effect on the supersonic flow characteristics of the combustion gas.

  4. Chemical-looping combustion of simulated synthesis gas using nickel oxide oxygen carrier supported on bentonite

    SciTech Connect

    Siriwardane, R.V.; Chaudhari, K.; Poston, J.A.; Zinn, A.; Simonyi, T.; Robinson, C.

    2007-05-01

    Chemical-looping combustion (CLC) is a combustion technology for clean and efficient utilization of fossil fuels for energy production. This process which produces sequestration ready CO2 systems is a promising technology to be utilized with coal gasification systems. In the present work, chemical-looping combustion has been studied with an oxygen carrier, NiO/bentonite (60 wt % NiO) for the gasification systems utilizing simulated synthesis gas. Global reaction rates of reduction and oxidation as a function of conversion were calculated for oxidation-reduction cycles utilizing the thermogravimetric analysis (TGA) data on multicycle tests conducted with NiO/bentonite at atmospheric pressure between 700 and 900 °C. The rate of reduction increased slightly with an increase in temperature, while the rate of oxidation decreased at 900 °C. The effect of particle size of the oxygen carrier on CLC was studied for the particle size between 20 and 200 mesh. The rates of reactions depended on the particle size of the oxygen carrier. The smaller the particle size, the higher the reaction rates. The multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for the production of CO2 from fuel gas at 800 and 900 °C and full consumption of hydrogen during the reaction. The data from a one cycle test on the effect of the pressure on the performance with NiO/bentonite utilizing the tapered element oscillating microbalance (TEOM) showed a positive effect of the pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. The X-ray diffraction (XRD) analysis confirmed the presence of the NiO phase in NiO/bentonite with the oxidized sample in the highpressure reactor and Ni phase with the reduced sample. The presence of a small amount of NiO in the reduced sample detected by X-ray photoelectron spectroscopy (XPS) may be due to its exposure to air during sample transfer from the reactor to XPS. Scanning electron

  5. Emissions of Parent, Nitro, and Oxygenated Polycyclic Aromatic Hydrocarbons from Residential Wood Combustion in Rural China

    PubMed Central

    SHEN, Guofeng; TAO, Shu; WEI, Siye; ZHANG, Yanyan; WANG, Rong; WANG, Bin; LI, Wei; SHEN, Huizhong; HUANG, Ye; CHEN, Yuanchen; CHEN, Han; YANG, Yifeng; WANG, Wei; WANG, Xilong; LIU, Wenxin; SIMONICH, Staci L. M.

    2012-01-01

    Residential wood combustion is one of the important sources of air pollution in developing countries. Among the pollutants emitted, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives, including nitrated and oxygenated PAHs (nPAHs and oPAHs), are of concern because of their mutagenic and carcinogenic effects. In order to evaluate their impacts on regional air quality and human health, emission inventories, based on realistic emission factors (EFs), are needed. In this study, the EFs of 28 pPAHs (EFPAH28), 9 nPAHs (EFPAHn9) and 4 oPAHs (EFPAHo4) were measured for residential combustion of 27 wood fuels in rural China. The measured EFPAH28, EFPAHn9, and EFPAHo4 for brushwood were 86.7±67.6, 3.22±1.95×10−2, and 5.56±4.32 mg/kg, which were significantly higher than 12.7±7.0, 8.27±5.51×10−3, and 1.19±1.87 mg/kg for fuel wood combustion (p < 0.05). Sixteen U.S. EPA priority pPAHs contributed approximately 95% of the total of the 28 pPAHs measured. EFs of pPAHs, nPAHs, and oPAHs were positively correlated with one another. Measured EFs varied obviously depending on fuel properties and combustion conditions. The EFs of pPAHs, nPAHs, and oPAHs were significantly correlated with modified combustion efficiency and fuel moisture. Nitro-naphthalene and 9-fluorenone were the most abundant nPAHs and oPAHs identified. Both nPAHs and oPAHs showed relatively high tendencies to be present in the particulate phase than pPAHs due to their lower vapor pressures. The gas-particle partitioning of freshly emitted pPAHs, nPAHs and oPAHs was primarily controlled by organic carbon absorption. PMID:22765266

  6. Numerical investigation of the role of clustering during oxygen-carrier regeneration in Chemical Looping Combustion

    NASA Astrophysics Data System (ADS)

    Goyal, Himanshu; Pepiot, Perrine

    2016-11-01

    In the air-reactor of a dual-bed Chemical Looping Combustion (CLC) system, the spent oxygen-carrier, in the form of metal or reduced metal oxide, is oxidized with air, typically in a high velocity riser reactor. Such a configuration provides challenging modeling issues, as the granular flow is characterized by a highly fluctuating solid volume fraction due to the formation of dense clusters. This may strongly affect the solid residence time in the air-reactor, and therefore, the extent of the oxygen-carrier regeneration and ultimately, the overall reactivity of the carrier in the fuel reactor. Here, we investigate how clustering impacts gas-solid chemical reactions in the reactor using a detailed Lagrange-Euler computational framework. The simulations account for both mass and heat transfer between the gas phase and the metal oxide particles, and the evolution of oxygen content of the metal oxide particles, or equivalently, their degree of oxidation. Two particle models of different complexity are considered. Results are analyzed to quantify the relative importance on the regeneration process of the reactor hydrodynamics. This material is based upon work supported by the National Science Foundation under Grant No. CBET-1638837.

  7. Kinetic mechanism for low-pressure oxygen/methane ignition and combustion

    NASA Astrophysics Data System (ADS)

    Slavinskaya, N. A.; Wiegand, M.; Starcke, J. H.; Riedel, U.; Haidn, O. J.; Suslov, D.

    2013-03-01

    It is known that during a launch of a rocket, the interaction of the exhaust gases of rocket engines with the atmosphere causes a local depletion of the ozone layer. In order to study these chemical processes in detail, a chemical reaction mechanism of the methane oxidation appropriate for high- and low-pressure conditions and a chemical reactor network to reproduce operating conditions in rocket engines and in the environment have been developed. An earlier developed detailed chemical kinetic model for the high-pressure CH4/O2 combustion has been improved for the low pressure and low temperature methane combustion and augmented with a submodel for NOx formation. The main model improvements are related to the pressure depending reactions. The model has been validated for operating conditions of 0.02 < p < 100 atm, 300 < T < 1800 K and 0.5 < Φ < 3.0. The network of chemical reactors available in CHEMICAL WORKBENCH software has been successfully developed to simulate chemical processes in the convergent divergent rocket nozzle and in the exhaust-jet. Simulations performed have shown that the exhaust gases of a methane/oxygen propelled liquid rocket engine contain high amounts of active radicals, which can influence the formation of nitrogen compounds and consume ozone in the atmosphere.

  8. Investigation of Coal Fueled Chemical Looping Combustion Using Fe3O4 as Oxygen Carrier

    NASA Astrophysics Data System (ADS)

    Xlang, Wenguo; Sun, Xiaoyan; Wangt, Sha; Tian, Wendong; Xu, Xiang; Xu, Yanji; Xiao, Yunhan

    Chemical-looping combustion (CLC) is a novel combustion technique with CO2 separation. Magnetite (Fe3O4) was selected as the oxygen carrier and Shenhua coal (Inner Mongolia, China) as the fuel for this study. The influences of operation temperatures, and coal to Fe3O4 mass ratios on the reduction characteristics of the oxygen carrier were investigated using an atmosphere TGA. The sample, comprised of 2.25mg coal and 12.75mg Fe3O4, was heated to 1000°C. Experimental results show that the reaction between the coal volatile and Fe3O4 began at 700°C while the reaction between the coal char and Fe3O4 occurred at 800°C and reached a peak at 900°C. Fe3O4 was fully reduced into FeO, while some FeO was further reduced to Fe. As the operation temperature rises, the reduction conversion rate increases. At the temperatures of 850°C, 900°C, and 950°C, the reduction conversion rates were 37.1%, 46.5%, and 54.1% respectively. When the mass ratios of coal to Fe3O4 were 5/95, 10/90, 15/85, and 20/80, the reduction conversion rates were 29.5%,40.8%,46.5%, and 46.6% respectively. With the increase of coal to Fe3O4 mass ratio, the conversion rate increases first and then changes no more. There exists an optimal coal to Fe3O4 mass ratio.

  9. Burning of solids in oxygen-rich environments in normal and reduced gravity. [combustion of cellulose acetates

    NASA Technical Reports Server (NTRS)

    Andracchio, C. R.; Cochran, T. H.

    1974-01-01

    An experimental program was conducted to investigate the combustion characteristics of solids burning in a weightless environment. The combustion characteristics of thin cellulose acetate material were obtained from specimens burned in supercritical as well as in low pressure oxygen atmospheres. Flame spread rates were measured and found to depend on material thickness and pressure in both normal gravity (1-g) and reduced gravity (0-g). A gravity effect on the burning process was also observed; the ratio of 1-g to 0-g flame spread rate becomes larger with increasing material thickness. Qualitative results on the combustion characteristics of metal screens (stainless steel, Inconel, copper, and aluminum) burning in supercritical oxygen and normal gravity are also presented. Stainless steel (300 sq mesh) was successfully ignited in reduced gravity; no apparent difference in the flame spread pattern was observed between 1-g and 0-g.

  10. Particulate Formation from a Copper Oxide-Based Oxygen Carrier in Chemical Looping Combustion for CO2 Capture

    EPA Science Inventory

    Attrition behavior and particle loss of a copper oxide-based oxygen carrier from a methane chemical looping combustion (CLC) process was investigated in a fluidized bed reactor. The aerodynamic diameters of most elutriated particulates, after passing through a horizontal settling...

  11. Effect of fuel gas composition in chemical-looping combustion with Ni-based oxygen carriers. 1. Fate of sulfur

    SciTech Connect

    Garcia-Labiano, F.; de Diego, L.F.; Gayan, P.; Adanez, J.; Abad, A.; Dueso, C.

    2009-03-15

    Chemical-looping combustion (CLC) has been suggested among the best alternatives to reduce the economic cost of CO{sub 2} capture using fuel gas because CO{sub 2} is inherently separated in the process. For gaseous fuels, natural gas, refinery gas, or syngas from coal gasification can be used. These fuels may contain different amounts of sulfur compounds, such as H{sub 2}S and COS. An experimental investigation of the fate of sulfur during CH{sub 4} combustion in a 500 W{sub th} CLC prototype using a Ni-based oxygen carrier has been carried out. The effect on the oxygen carrier behavior and combustion efficiency of several operating conditions such as temperature and H{sub 2}S concentration has been analyzed. Nickel sulfide, Ni3S{sub 2}, was formed at all operating conditions in the fuel reactor, which produced an oxygen carrier deactivation and lower combustion efficiencies. However, the oxygen carrier recovered their initial reactivity after certain time without sulfur addition. The sulfides were transported to the air reactor where SO{sub 2} was produced as final gas product. Agglomeration problems derived from the sulfides formation were never detected during continuous operation. Considering both operational and environmental aspects, fuels with sulfur contents below 100 vppm H{sub 2}S seem to be adequate to be used in an industrial CLC plant.

  12. Experiments on chemical looping combustion of coal with a NiO based oxygen carrier

    SciTech Connect

    Shen, Laihong; Wu, Jiahua; Xiao, Jun

    2009-03-15

    A chemical looping combustion process for coal using interconnected fluidized beds with inherent separation of CO{sub 2} is proposed in this paper. The configuration comprises a high velocity fluidized bed as an air reactor, a cyclone, and a spout-fluid bed as a fuel reactor. The high velocity fluidized bed is directly connected to the spout-fluid bed through the cyclone. Gas composition of both fuel reactor and air reactor, carbon content of fly ash in the fuel reactor, carbon conversion efficiency and CO{sub 2} capture efficiency were investigated experimentally. The results showed that coal gasification was the main factor which controlled the contents of CO and CH{sub 4} concentrations in the flue gas of the fuel reactor, carbon conversion efficiency in the process of chemical looping combustion of coal with NiO-based oxygen carrier in the interconnected fluidized beds. Carbon conversion efficiency reached only 92.8% even when the fuel reactor temperature was high up to 970 C. There was an inherent carbon loss in the process of chemical looping combustion of coal in the interconnected fluidized beds. The inherent carbon loss was due to an easy elutriation of fine char particles from the freeboard of the spout-fluid bed, which was inevitable in this kind of fluidized bed reactor. Further improvement of carbon conversion efficiency could be achieved by means of a circulation of fine particles elutriation into the spout-fluid bed or the high velocity fluidized bed. CO{sub 2} capture efficiency reached to its equilibrium of 80% at the fuel reactor temperature of 960 C. The inherent loss of CO{sub 2} capture efficiency was due to bypassing of gases from the fuel reactor to the air reactor, and the product of residual char burnt with air in the air reactor. Further experiments should be performed for a relatively long-time period to investigate the effects of ash and sulfur in coal on the reactivity of nickel-based oxygen carrier in the continuous CLC reactor

  13. Combustion

    NASA Technical Reports Server (NTRS)

    Bulzan, Dan

    2007-01-01

    An overview of the emissions related research being conducted as part of the Fundamental Aeronautics Subsonics Fixed Wing Project is presented. The overview includes project metrics, milestones, and descriptions of major research areas. The overview also includes information on some of the emissions research being conducted under NASA Research Announcements. Objective: Development of comprehensive detailed and reduced kinetic mechanisms of jet fuels for chemically-reacting flow modeling. Scientific Challenges: 1) Developing experimental facilities capable of handling higher hydrocarbons and providing benchmark combustion data. 2) Determining and understanding ignition and combustion characteristics, such as laminar flame speeds, extinction stretch rates, and autoignition delays, of jet fuels and hydrocarbons relevant to jet surrogates. 3) Developing comprehensive kinetic models for jet fuels.

  14. Combustion, Respiration and Intermittent Exercise: A Theoretical Perspective on Oxygen Uptake and Energy Expenditure

    PubMed Central

    Scott, Christopher B.

    2014-01-01

    While no doubt thought about for thousands of years, it was Antoine Lavoisier in the late 18th century who is largely credited with the first “modern” investigations of biological energy exchanges. From Lavoisier’s work with combustion and respiration a scientific trend emerges that extends to the present day: the world gains a credible working hypothesis but validity goes missing, often for some time, until later confirmed using proper measures. This theme is applied to glucose/glycogen metabolism where energy exchanges are depicted as conversion from one form to another and, transfer from one place to another made by both the anaerobic and aerobic biochemical pathways within working skeletal muscle, and the hypothetical quantification of these components as part of an oxygen (O2) uptake measurement. The anaerobic and aerobic energy exchange components of metabolism are represented by two different interpretations of O2 uptake: one that contains a glycolytic component (1 L O2 = 21.1 kJ) and one that does not (1 L O2 = 19.6 kJ). When energy exchange transfer and oxygen-related expenditures are applied separately to exercise and recovery periods, an increased energy cost for intermittent as compared to continuous exercise is hypothesized to be a direct result. PMID:24833508

  15. Processing and Evaluation of Next Generation Oxygen Carrier Materials for Chemical Looping Combustion

    NASA Astrophysics Data System (ADS)

    Hamedi Rad, Mina

    This study follows two methods to achieve a modified CaMnO 3-delta structure with higher oxygen capacity and stability. The first method is replacement of manganese with iron as a cheaper alternative and the second method is size effect investigations of A-site dopants on CaMn 0.9Fe0.1O3-delta and its oxygen capacity and stability. Solid state reaction followed by mechanical extrusion is used as the preparation method. All synthesized perovskites are characterized by TGA and XRD analyses. The samples of highest oxygen capacity and stability are further characterized by SEM and BET analyses. Oxygen uncoupling behavior and reactivity of these samples are also examined using a fluidized bed reactor performing Chemical Looping Combustion. The temperature effect is also investigated during chemical looping process at temperatures of 800, 850, 900 and 950 °C. In the first method, since calcium could not be incorporated in the structure, strontium is used as the A-site cation. SrFeO3-delta has shown to be more stable than CaMnO3-delta. However, because of low oxygen capacity, it is doped on the A-site (La and Ba) and B-site (Al, Ti, Mn, Co) by 10 mol% (Sr0.9La0.1FeO3-delta, Sr0.9Ba0.1FeO3-delta, SrFe0.9Al 0.1O3-delta, SrFe0.9Ti0.1O3-delta , SrFe0.9Mn0.1O3-delta, SrFe 0.9Co0.1O3-delta). Results reveal that manganese doped structure (SrFe0.9Mn0.1O3-delta) has the highest oxygen capacity. Adding more manganese to the structure increases the oxygen capacity even further. The best iron-based structure has 30 mol% manganese, doped on the B-site, having 28% mass change in an inert atmosphere (SrFe0.7Mn0.3O3-delta, SFM73) and high stability. Results of conducted experiments in second method demonstrated that Strontium doped perovskite (Ca0.9Sr0.1Mn0.9Fe 0.1O3-delta, CS91MF91) is the best synthesized oxygen carrier among all synthesized manganese and iron-based perovskites. This material shows excellent oxygen uptake and release (1.78 wt. %) and high stability. The reactivity and

  16. Exfoliation of layered double hydroxides for enhanced oxygen evolution catalysis.

    PubMed

    Song, Fang; Hu, Xile

    2014-07-17

    The oxygen evolution reaction is a key reaction in water splitting. The common approach in the development of oxygen evolution catalysts is to search for catalytic materials with new and optimized chemical compositions and structures. Here we report an orthogonal approach to improve the activity of catalysts without alternating their compositions or structures. Specifically, liquid phase exfoliation is applied to enhance the oxygen evolution activity of layered double hydroxides. The exfoliated single-layer nanosheets exhibit significantly higher oxygen evolution activity than the corresponding bulk layered double hydroxides in alkaline conditions. The nanosheets from nickel iron and nickel cobalt layered double hydroxides outperform a commercial iridium dioxide catalyst in both activity and stability. The exfoliation creates more active sites and improves the electronic conductivity. This work demonstrates the promising catalytic activity of single-layered double hydroxides for the oxygen evolution reaction.

  17. Combustion of solid fuel slabs with gaseous oxygen in a hybrid motor analog

    NASA Technical Reports Server (NTRS)

    Chiaverini, Martin J.; Harting, George C.; Lu, Yeu-Cherng; Kuo, Kenneth K.; Serin, Nadir; Johnson, David K.

    1995-01-01

    Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated Polybutadiene) fuel cross-linked with diisocyanate was burned with gaseous oxygen (GOX) under various operating conditions. Large-amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed-line system and combustion chamber, the pressure oscillations were drastically reduced from plus or minus 20% of the localized mean pressure to an acceptable range of plus or minus 1.5%. Embedded fine--wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading edge region, the subsurface thermal wave profiles in the upstream locations are thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundary-layer region. Both real-time X-ray radiography and ultrasonic pulse echo techniques were used to determine the instantaneous web thicknesses and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented. Several tests were conducted using, simultaneously, one translucent fuel slab and one fuel slab processed with carbon black powder. The addition of carbon black did not affect the measured regression rates or

  18. Solid waste management of a chemical-looping combustion plant using Cu-based oxygen carriers.

    PubMed

    García-Labiano, Francisco; Gayán, Pilar; Adánez, Juan; De Diego, Luis F; Forero, Carmen R

    2007-08-15

    Waste management generated from a Chemical-Looping Combustion (CLC) plant using copper-based materials is analyzed by two ways: the recovery and recycling of the used material and the disposal of the waste. A copper recovery process coupled to the CLC plant is proposed to avoid the loss of active material generated by elutriation from the system. Solid residues obtained from a 10 kWth CLC prototype operated during 100 h with a CuO-Al2O3 oxygen carrier prepared by impregnation were used as raw material in the recovery process. Recovering efficiencies of approximately 80% were obtained in the process, where the final products were an eluate of Cu(NO3)2 and a solid. The eluate was used for preparation of new oxygen carriers by impregnation, which exhibited high reactivity for reduction and oxidation reactions as well as adequate physical and chemical properties to be used in a CLC plant. The proposed recovery process largely decreases the amount of natural resources (Cu and Al203) employed in a CLC power plant as well as the waste generated in the process. To determine the stability of the different solid streams during deposition in a landfill, these were characterized with respect to their leaching behavior according to the European Union normative. The solid residue finally obtained in the CLC plant coupled to the recovery process (composed by Al2O3 and CuAl2O4) can be classified as a stable nonreactive hazardous waste acceptable at landfills for nonhazardous wastes.

  19. The study on the heat transfer characteristics of oxygen fuel combustion boiler

    NASA Astrophysics Data System (ADS)

    Wu, Haibo; Liu, Zhaohui; Liao, Haiyan

    2016-10-01

    According to 350MW and 600MW boilers, under oxygen fuel condition, through the reasonable control of the primary and secondary flow and the correct option and revision of mathematical model, the temperature distribution, heat flux distribution and absorption heat distribution, etc. was obtained which compared with those under air condition. Through calculation, it is obtained that the primary and secondary flow mixed well, good tangentially fired combustion in furnace was formed, the temperature under air condition obviously higher than the temperature under O26 condition. The adiabatic flame temperature of wet cycle was slightly higher than that of dry cycle. The maximum heat load appeared on the waterwall around the burner area. The heat load gradually decreased along the furnace height up and down in burner area. The heat absorption capacity of the furnace under O26 was lower than that under the air condition. The heat absorption capacity of the platen heating surface under O26 was equal to that under air condition. And the heat absorbing capacity of waterwall under O26 was about7%~12% less than that under air condition.

  20. Reference concepts for a space-based hydrogen-oxygen combustion, turboalternator, burst power system

    SciTech Connect

    Edenburn, M.W.

    1990-07-01

    This report describes reference concepts for a hydrogen-oxygen combustion, turboalternator power system that supplies power during battle engagement to a space-based, ballistic missile defense platform. All of the concepts are open''; that is, they exhaust hydrogen or a mixture of hydrogen and water vapor into space. We considered the situation where hydrogen is presumed to be free to the power system because it is also needed to cool the platform's weapon and the situation where hydrogen is not free and its mass must be added to that of the power system. We also considered the situation where water vapor is an acceptable exhaust and the situation where it is not. The combination of these two sets of situations required four different power generation systems, and this report describes each, suggests parameter values, and estimates masses for each of the four. These reference concepts are expected to serve as a baseline'' to which other types of power systems can be compared, and they are expected to help guide technology development efforts in that they suggest parameter value ranges that will lead to optimum system designs. 7 refs., 18 figs., 5 tabs.

  1. OXYGEN-ENRICHED COAL COMBUSTION WITH CARBON DIOXIDE RECYCLE AND RECOVERY: SIMULATION AND EXPERIMENTAL STUDY

    SciTech Connect

    John M. Veranth; Gautham Krishnamoorthy

    2002-02-28

    Two computational problems were worked on for this study. The first chapter examines the option of coal combustion using oxygen feed with carbon dioxide recycle to control the adiabatic flame temperature. Computer simulations using an existing state-of-the-art 3-dimensional computer code for turbulent reacting flows with reacting particles were employed to study the effects of increased carbon dioxide mole fraction on the char burnout, radiant heat transfer, metal partitioning, and NOx formation. The second chapter compares assumptions for the CO/CO{sub 2} ratio at the surface of mineral inclusions made in previous studies to predictions obtained from a pseudo-steady state kinetic model (SKIPPY) for a single porous particle. The detailed kinetic simulations from SKIPPY for varying particle sizes and bulk gas compositions were used to develop algebraic expressions for the CO/CO{sub 2} ratio that can be incorporated into metal vaporization sub-models run as a post processor to detailed furnace simulations. Vaporization rate controls the formation of metal-enriched sub-micron particles in pulverized coal fired power plants.

  2. Design and Fabrication of Oxygen/RP-2 Multi-Element Oxidizer-Rich Staged Combustion Thrust Chamber Injectors

    NASA Technical Reports Server (NTRS)

    Garcia, C. P.; Medina, C. R.; Protz, C. S.; Kenny, R. J.; Kelly, G. W.; Casiano, M. J.; Hulka, J. R.; Richardson, B. R.

    2016-01-01

    As part of the Combustion Stability Tool Development project funded by the Air Force Space and Missile Systems Center, the NASA Marshall Space Flight Center was contracted to assemble and hot-fire test a multi-element integrated test article demonstrating combustion characteristics of an oxygen/hydrocarbon propellant oxidizer-rich staged-combustion engine thrust chamber. Such a test article simulates flow through the main injectors of oxygen/kerosene oxidizer-rich staged combustion engines such as the Russian RD-180 or NK-33 engines, or future U.S.-built engine systems such as the Aerojet-Rocketdyne AR-1 engine or the Hydrocarbon Boost program demonstration engine. On the current project, several configurations of new main injectors were considered for the thrust chamber assembly of the integrated test article. All the injector elements were of the gas-centered swirl coaxial type, similar to those used on the Russian oxidizer-rich staged-combustion rocket engines. In such elements, oxidizer-rich combustion products from the preburner/turbine exhaust flow through a straight tube, and fuel exiting from the combustion chamber and nozzle regenerative cooling circuits is injected near the exit of the oxidizer tube through tangentially oriented orifices that impart a swirl motion such that the fuel flows along the wall of the oxidizer tube in a thin film. In some elements there is an orifice at the inlet to the oxidizer tube, and in some elements there is a sleeve or "shield" inside the oxidizer tube where the fuel enters. In the current project, several variations of element geometries were created, including element size (i.e., number of elements or pattern density), the distance from the exit of the sleeve to the injector face, the width of the gap between the oxidizer tube inner wall and the outer wall of the sleeve, and excluding the sleeve entirely. This paper discusses the design rationale for each of these element variations, including hydraulic, structural

  3. Enhancing perovskite electrocatalysis through strain tuning of oxygen deficiency

    DOE PAGES

    Barron, Sara C.; Lee, Ho Nyung; Petrie, Jonathan R.; ...

    2016-05-27

    Oxygen vacancies in transition-metal oxides facilitate catalysis critical for energy storage and generation. However, promoting vacancies at the lower temperatures required for operation in devices such as metal–air batteries and portable fuel cells has proven elusive. Here we used thin films of perovskite-based strontium cobaltite (SrCoOx) to show that epitaxial strain is a powerful tool for manipulating the oxygen content under conditions consistent with the oxygen evolution reaction, yielding increasingly oxygen-deficient states in an environment where the cobaltite would normally be fully oxidized. The additional oxygen vacancies created through tensile strain enhance the cobaltite’s catalytic activity toward this important reactionmore » by over an order of magnitude, equaling that of precious-metal catalysts, including IrO2. Lastly, our findings demonstrate that strain in these oxides can dictate the oxygen stoichiometry independent of ambient conditions, allowing unprecedented control over oxygen vacancies essential in catalysis near room temperature.« less

  4. Enhancing perovskite electrocatalysis through strain tuning of oxygen deficiency

    SciTech Connect

    Barron, Sara C.; Lee, Ho Nyung; Petrie, Jonathan R.; Jeen, Hyoungjeen; Meyer, Tricia L.

    2016-05-27

    Oxygen vacancies in transition-metal oxides facilitate catalysis critical for energy storage and generation. However, promoting vacancies at the lower temperatures required for operation in devices such as metal–air batteries and portable fuel cells has proven elusive. Here we used thin films of perovskite-based strontium cobaltite (SrCoOx) to show that epitaxial strain is a powerful tool for manipulating the oxygen content under conditions consistent with the oxygen evolution reaction, yielding increasingly oxygen-deficient states in an environment where the cobaltite would normally be fully oxidized. The additional oxygen vacancies created through tensile strain enhance the cobaltite’s catalytic activity toward this important reaction by over an order of magnitude, equaling that of precious-metal catalysts, including IrO2. Lastly, our findings demonstrate that strain in these oxides can dictate the oxygen stoichiometry independent of ambient conditions, allowing unprecedented control over oxygen vacancies essential in catalysis near room temperature.

  5. Longevity, oxygen toxicity and radiation-enhanced resistance to oxygen in tribolium confusum

    SciTech Connect

    Lee, Y.J.

    1985-01-01

    Sublethal doses of ionizing radiation increase longevity in a variety of insects suggesting that irradiation may retard the age-dependent decline of physiological functions. There have been no systematic investigations of the response of irradiated populations to stress, however. The authors have demonstrated that resistance of adult flour beetles, Tribolium confusum, to oxygen poisoning declines progressively with age. They have examined oxygen resistance of irradiated populations of T. confusum as a function of age at irradiation, of time after irradiation, and of radiation dose and of dose-modifying factors. Shortly after gamma-irradiation, flour beetles exhibited a decline in resistance to oxygen toxicity. Then, about two weeks after irradiation, the LD/sub 50/ exposure time in pure oxygen was much greater than that of nonirradiated beetles, and this enhanced resistance persisted for about 6 months. The magnitude of the enhancement was a function of dose, decreased with increasing age at irradiation, and was modified by radiation factors. Sublethal irradiation under anoxia, at low dose rate, or with dose fractionation reduced the development of oxygen resistance to approximately the same degree that it reduced acute radiation lethality . Radiation-enhanced resistance to stress may be an important factor in the increased longevity of irradiated insects.

  6. Sulfur behavior in chemical looping combustion with NiO/Al{sub 2}O{sub 3} oxygen carrier

    SciTech Connect

    Shen, Laihong; Gao, Zhengping; Wu, Jiahua; Xiao, Jun

    2010-05-15

    Chemical looping combustion (CLC) is a novel technology where CO{sub 2} is inherently separated during combustion. Due to the existence of sulfur contaminants in the fossil fuels, the gaseous products of sulfur species and the interaction of sulfur contaminants with oxygen carrier are a big concern in the CLC practice. The reactivity of NiO/Al{sub 2}O{sub 3} oxygen carrier reduction with a gas mixture of CO/H{sub 2} and H{sub 2}S is investigated by means of a thermogravimetric analyzer (TGA) and Fourier Transform Infrared spectrum analyzer in this study. An X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscope (SEM) are used to evaluate the phase characterization of reacted oxygen carrier, and the formation mechanisms of the gaseous products of sulfur species are elucidated in the process of chemical looping combustion with a gaseous fuel containing hydrogen sulfide. The results show that the rate of NiO reduction with H{sub 2}S is higher than the one with CO. There are only Ni and Ni{sub 3}S{sub 2} phases of nickel species in the fully reduced oxygen carrier, and no evidence for the existence of NiS or NiS{sub 2}. The formation of Ni{sub 3}S{sub 2} is completely reversible during the process of oxygen carrier redox. A liquid phase sintering on the external surface of reduced oxygen carriers is mainly attributed to the production of the low melting of Ni{sub 3}S{sub 2} in the nickel-based oxygen carrier reduction with a gaseous fuel containing H{sub 2}S. Due to the sintering of metallic nickel grains on the external surface of the reduced oxygen carrier, further reaction of the oxygen carrier with H{sub 2}S is constrained, and there is no increase of the sulfidation index of the reduced oxygen carrier with the cyclical reduction number. Also, a continuous operation with a syngas of carbon monoxide and hydrogen containing H{sub 2}S is carried out in a 1 kW{sub th} CLC prototype based on the nickel-based oxygen carrier, and

  7. Enhanced capability of the Combustion-Heated Scramjet Test Facility

    NASA Technical Reports Server (NTRS)

    Rock, Kenneth E.; Andrews, Earl H.; Eggers, James M.

    1991-01-01

    The Combustion-Heated Scramjet Test Facility (CHSTF) is described together with its modifications. The expanded simulation capabilities of the facility are documented. Nozzle exit surveys and tunnel calibration information are presented. It is noted that these modifications included a new heat-sink nickel liner heater, a new Mach 4.7 nozzle, and a new 70-ft vacuum sphere exhaust system. It is found that the facility in the air ejector mode of operation performed similarly to that prior to the addition of the vacuum sphere ducting.

  8. Metallized Gelled Propellants: Oxygen/RP-1/Aluminum Rocket Heat Transfer and Combustion Measurements

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan; Zakany, James S.

    1996-01-01

    A series of rocket engine heat transfer experiments using metallized gelled liquid propellants was conducted. These experiments used a small 20- to 40-lb/f thrust engine composed of a modular injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-percentage by weight loadings of aluminum particles. Gaseous oxygen was used as the oxidizer. Three different injectors were used during the testing: one for the baseline O(2)/RP-1 tests and two for the gelled and metallized gelled fuel firings. Heat transfer measurements were made with a rocket engine calorimeter chamber and nozzle with a total of 31 cooling channels. Each chamber used a water flow to carry heat away from the chamber and the attached thermocouples and flow meters allowed heat flux estimates at each of the 31 stations. The rocket engine Cstar efficiency for the RP-1 fuel was in the 65-69 percent range, while the gelled 0 percent by weight RP-1 and the 5-percent by weight RP-1 exhibited a Cstar efficiency range of 60 to 62% and 65 to 67%, respectively. The 55-percent by weight RP-1 fuel delivered a 42-47% Cstar efficiency. Comparisons of the heat flux and temperature profiles of the RP-1 and the metallized gelled RP-1/A1 fuels show that the peak nozzle heat fluxes with the metallized gelled O2/RP-1/A1 propellants are substantially higher than the baseline O2/RP-1: up to double the flux for the 55 percent by weight RP-1/A1 over the RP-1 fuel. Analyses showed that the heat transfer to the wall was significantly different for the RP-1/A1 at 55-percent by weight versus the RP-1 fuel. Also, a gellant and an aluminum combustion delay was inferred in the 0 percent and 5-percent by weight RP-1/A1 cases from the decrease in heat flux in the first part of the chamber. A large decrease in heat flux in the last half of the chamber was caused by fuel deposition in the chamber and nozzle. The engine combustion occurred well downstream of the injector face

  9. Combustion Dynamics and Stability Modeling of a Liquid Oxygen/RP-2 Oxygen-Rich Staged Combustion Preburner and Thrust Chamber Assembly with Gas-Centered Swirl Coaxial Injector Elements

    NASA Technical Reports Server (NTRS)

    Casiano, M. J.; Kenny, R. J.; Protz, C. S.; Garcia, C. P.; Simpson, S. P.; Elmore, J. L.; Fischbach, S. R.; Giacomoni, C. B.; Hulka, J. R.

    2016-01-01

    The Combustion Stability Tool Development (CSTD) project, funded by the Air Force Space and Missile Systems Center, began in March 2015 supporting a renewed interest in the development of a liquid oxygen/hydrocarbon, oxygen-rich combustion engine. The project encompasses the design, assembly, and hot-fire testing of the NASA Marshall Space Flight Center 40-klbf Integrated Test Rig (MITR). The test rig models a staged-combustion configuration by combining an oxygen-rich preburner (ORPB), to generate hot gas, with a thrust chamber assembly (TCA) using gas-centered swirl coaxial injector elements. There are five separately designed interchangeable injectors in the TCA that each contain 19- or 27- injector elements. A companion paper in this JANNAF conference describes the design characteristics, rationale, and fabrication issues for all the injectors. The data acquired from a heavily instrumented rig encompasses several injectors, several operating points, and stability bomb tests. Another companion paper in this JANNAF conference describes this test program in detail. In this paper, dynamic data from the hot-fire testing is characterized and used to identify the responses in the ORPB and TCA. A brief review of damping metrics are discussed and applied as a measure of stability margin for damped acoustic modes. Chug and longitudinal combustion stability models and predictions are described which includes new dynamic models for compressible flow through an orifice and a modification to incorporate a third feed line for inclusion of the fuel-film coolant. Flow-acoustics finite element modeling is used to investigate the anticipated TCA acoustics, the effects of injector element length on stability margin, and the potential use of an ORPB orifice trip ring for improving longitudinal stability margin.

  10. Low Oxygen Tension Enhances Hepatitis C Virus Replication

    PubMed Central

    Kalliampakou, K. I.; Kotta-Loizou, I.; Befani, C.; Liakos, P.; Simos, G.; Mentis, A. F.; Kalliaropoulos, A.; Doumba, P. P.; Smirlis, D.; Foka, P.; Bauhofer, O.; Poenisch, M.; Windisch, M. P.; Lee, M. E.; Koskinas, J.; Bartenschlager, R.

    2013-01-01

    Low oxygen tension exerts a significant effect on the replication of several DNA and RNA viruses in cultured cells. In vitro propagation of hepatitis C virus (HCV) has thus far been studied under atmospheric oxygen levels despite the fact that the liver tissue microenvironment is hypoxic. In this study, we investigated the efficiency of HCV production in actively dividing or differentiating human hepatoma cells cultured under low or atmospheric oxygen tensions. By using both HCV replicons and infection-based assays, low oxygen was found to enhance HCV RNA replication whereas virus entry and RNA translation were not affected. Hypoxia signaling pathway-focused DNA microarray and real-time quantitative reverse transcription-PCR (qRT-PCR) analyses revealed an upregulation of genes related to hypoxic stress, glycolytic metabolism, cell growth, and proliferation when cells were kept under low (3% [vol/vol]) oxygen tension, likely reflecting cell adaptation to anaerobic conditions. Interestingly, hypoxia-mediated enhancement of HCV replication correlated directly with the increase in anaerobic glycolysis and creatine kinase B (CKB) activity that leads to elevated ATP production. Surprisingly, activation of hypoxia-inducible factor alpha (HIF-α) was not involved in the elevation of HCV replication. Instead, a number of oncogenes known to be associated with glycolysis were upregulated and evidence that these oncogenes contribute to hypoxia-mediated enhancement of HCV replication was obtained. Finally, in liver biopsy specimens of HCV-infected patients, the levels of hypoxia and anaerobic metabolism markers correlated with HCV RNA levels. These results provide new insights into the impact of oxygen tension on the intricate HCV-host cell interaction. PMID:23269812

  11. Carbon and oxygen isotopic composition of coal and carbon dioxide derived from laboratory coal combustion: A preliminary study

    USGS Publications Warehouse

    Warwick, Peter; Ruppert, Leslie F.

    2016-01-01

    The concentration of carbon dioxide (CO2) in the atmosphere has dramatically increased from the start of the industrial revolution in the mid-1700s to present levels exceeding 400 ppm. Carbon dioxide derived from fossil fuel combustion is a greenhouse gas and a major contributor to on-going climate change. Carbon and oxygen stable isotope geochemistry is a useful tool to help model and predict the contributions of anthropogenic sources of CO2 in the global carbon cycle. Surprisingly few studies have addressed the carbon and oxygen isotopic composition of CO2 derived from coal combustion. The goal of this study is to document the relationships between the carbon and oxygen isotope signatures of coal and signatures of the CO2 produced from laboratory coal combustion in atmospheric conditions.Six coal samples were selected that represent various geologic ages (Carboniferous to Tertiary) and coal ranks (lignite to bituminous). Duplicate splits of the six coal samples were ignited and partially combusted in the laboratory at atmospheric conditions. The resulting coal-combustion gases were collected and the molecular composition of the collected gases and isotopic analyses of δ13C of CO2, δ13C of CH4, and δ18O of CO2 were analysed by a commercial laboratory. Splits (~ 1 g) of the un-combusted dried ground coal samples were analyzed for δ13C and δ18O by the U.S. Geological Survey Reston Stable Isotope Laboratory.The major findings of this preliminary work indicate that the isotopic signatures of δ13C (relative to the Vienna Pee Dee Belemnite scale, VPDB) of CO2 resulting from coal combustion are similar to the δ13CVPDB signature of the bulk coal (− 28.46 to − 23.86 ‰) and are not similar to atmospheric δ13CVPDB of CO2 (~ − 8 ‰, see http://www.esrl.noaa.gov/gmd/outreach/isotopes/c13tellsus.html). The δ18O values of bulk coal are strongly correlated to the coal dry ash yields and appear to have little or no influence on the δ18O values of CO2

  12. Enhancing the combustible properties of bamboo by torrefaction.

    PubMed

    Rousset, Patrick; Aguiar, Clarissa; Labbé, Nicole; Commandré, Jean-Michel

    2011-09-01

    Bamboo has wide range of moisture content, low bulk energy density and is difficult to transport, handle, store and feed into existing combustion and gasification systems. Because of its important fuel characteristics such as low ash content, alkali index and heating value, bamboo is a promising energy crop for the future. The aim of this study was to evaluate the effects of torrefaction on the main energy properties of Bambusa vulgaris. Three different torrefaction temperatures were employed: 220, 250 and 280°C. The elemental characteristics of lignite and coal were compared to the torrefied bamboo. The characteristics of the biomass fuels tend toward those of low rank coals. Principal component analysis of FTIR data showed a clear separation between the samples by thermal treatment. The loadings plot indicated that the bamboo samples underwent chemical changes related to carbonyl groups, mostly present in hemicelluloses, and to aromatic groups present in lignin.

  13. Metallized Gelled Propellants: Oxygen/RP-1/aluminum Rocket Combustion Experiments

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan; Zakany, James S.

    1995-01-01

    A series of combustion experiments were conducted to measure the specific impulse, Cstar-, and specific-impulse efficiencies of a rocket engine using metallized gelled liquid propellants. These experiments used a small 20- to 40-1bf (89- to 178-N) thrust, modular engine consisting of an injector, igniter, chamber and nozzle. The fuels used were traditional liquid RP-1 and gelled RP-1 with 0-, 5-, and 55-wt% loadings of aluminum and gaseous oxygen was the oxidizer. Ten different injectors were used during the testing: 6 for the baseline 02/RP-1 tests and 4 for the gelled fuel tests which covered a wide range of mixture ratios. At the peak of the Isp versus oxidizer-to-fuel ratio (O/F) data, a range of 93 to 99% Cstar efficiency was reached with ungelled 02/RP-1. A Cstar efficiency range of 75 to 99% was obtained with gelled RP-l (0-wt% RP-1/Al) while the metallized 5-wt% RP-1/Al delivered a Cstar efficiency of 94 to 99% at the peak Isp in the O/F range tested. An 88 to 99% Cstar efficiency was obtained at the peak Isp of the gelled RP1/Al with 55-wt% Al. Specific impulse efficiencies for the 55-wt% RP-1/Al of 67%-83% were obtained at a 2.4:1 expansion ratio. Injector erosion was evident with the 55-wt% testing, while there was little or no erosion seen with the gelled RP-1 with 0- and 5-wt% Al. A protective layer of gelled fuel formed in the firings that minimized the damage to the rocket injector face. This effect may provide a useful technique for engine cooling. These experiments represent a first step in characterizing the performance of and operational issues with gelled RP-1 fuels.

  14. Combustion Stability Characteristics of the Project Morpheus Liquid Oxygen / Liquid Methane Main Engine

    NASA Technical Reports Server (NTRS)

    Melcher, John C.; Morehead, Robert L.

    2014-01-01

    The project Morpheus liquid oxygen (LOX) / liquid methane (LCH4) main engine is a Johnson Space Center (JSC) designed 5,000 lbf-thrust, 4:1 throttling, pressure-fed cryogenic engine using an impinging element injector design. The engine met or exceeded all performance requirements without experiencing any in- ight failures, but the engine exhibited acoustic-coupled combustion instabilities during sea-level ground-based testing. First tangential (1T), rst radial (1R), 1T1R, and higher order modes were triggered by conditions during the Morpheus vehicle derived low chamber pressure startup sequence. The instability was never observed to initiate during mainstage, even at low power levels. Ground-interaction acoustics aggravated the instability in vehicle tests. Analysis of more than 200 hot re tests on the Morpheus vehicle and Stennis Space Center (SSC) test stand showed a relationship between ignition stability and injector/chamber pressure. The instability had the distinct characteristic of initiating at high relative injection pressure drop at low chamber pressure during the start sequence. Data analysis suggests that the two-phase density during engine start results in a high injection velocity, possibly triggering the instabilities predicted by the Hewitt stability curves. Engine ignition instability was successfully mitigated via a higher-chamber pressure start sequence (e.g., 50% power level vs 30%) and operational propellant start temperature limits that maintained \\cold LOX" and \\warm methane" at the engine inlet. The main engine successfully demonstrated 4:1 throttling without chugging during mainstage, but chug instabilities were observed during some engine shutdown sequences at low injector pressure drop, especially during vehicle landing.

  15. Chemical-looping combustion of coal-derived synthesis gas over copper oxide oxygen carriers

    SciTech Connect

    Tian, H.; Chaudhari, K.; Simonyi, T.; Poston, J.; Liu, T.; Sanders, T.; Veser, G.; Siriwardane, R.

    2008-01-01

    CuO/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900 °C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO2 from fuel gas at 800 and 900 °C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation-reduction cycles above 700 °C in an atmospheric thermogravimetric analyzer. The nanostructured CuO-BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700-900 °C.

  16. Chemical-looping combustion of coal-derived synthesis gas over copper oxide oxygen carriers

    SciTech Connect

    Hanjing Tian; Karuna Chaudhari; Thomas Simonyi; James Poston; Tengfei Liu; Tom Sanders; Goetz Veser; Ranjani Siriwardane

    2008-11-15

    CuO/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900{degree}C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO{sub 2} from fuel gas at 800 and 900{degree}C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation-reduction cycles above 700{degree}C in an atmospheric thermogravimetric analyzer. The nanostructured CuO-BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700-900{degree}C. 48 refs., 12 figs., 8 tabs.

  17. Chemical-looping Combustion of Coal-derived Synthesis Gas Over Copper Oxide Oxygen Carriers

    SciTech Connect

    Tian, Hanjing; Chaudhari, K P; Simonyi, Thomas; Poston, J A; Liu, Tengfei; Sanders, Tom; Veser, Goetz; Siriwardane, R V

    2008-11-01

    CuO/bentonite and CuO-BHA nanocomposites were studied as oxygen carriers in chemical-looping combustion (CLC) of simulated synthesis gas. Global reaction rates of reduction and oxidation, as the function of reaction conversion, were calculated from 10-cycle oxidation/reduction tests utilizing thermogravimetric analysis at atmospheric pressure between 700 and 900 °C. It was found that the reduction reactions are always faster than oxidation reactions; reaction temperature and particle size do not significantly affect the reaction performance of CuO/bentonite. Multicycle CLC tests conducted in a high-pressure flow reactor showed stable reactivity for production of CO2 from fuel gas at 800 and 900 °C and full consumption of hydrogen during the reaction. Results of the tapered element oscillating microbalance showed a negative effect of pressure on the global rates of reduction-oxidation reactions at higher fractional conversions. X-ray diffraction patterns confirmed the presence of CuO in the bulk phase of the oxidized sample. Electron microanalysis showed significant morphology changes of reacted CuO/bentonite samples after the 10 oxidation-reduction cycles above 700 °C in an atmospheric thermogravimetric analyzer. The nanostructured CuO-BHA carrier also showed excellent stability and, in comparison to the CuO/bentonite system, slightly accelerated redox kinetics albeit at the expense of significantly increased complexity of manufacturing. Overall, both types of CuO carriers exhibited excellent reaction performance and thermal stability for the CLC process at 700-900 °C.

  18. The Tapioca Bomb: A Demonstration to Enhance Learning about Combustion and Chemical Safety

    ERIC Educational Resources Information Center

    Keeratichamroen, Wasana; Dechsri, Precharn; Panijpan, Bhinyo; Ruenwongsa, Pintip

    2010-01-01

    In any demonstration to students, producing light and sound usually ensures interest and can enhance understanding and retention of the concepts involved. A guided inquiry (Predict, Observe, Explain: POE) approach was used to involve the students actively in their learning about the explosive combustion of fine flour particles in air in the…

  19. Plasma torch for ignition, flameholding and enhancement of combustion in high speed flows

    NASA Technical Reports Server (NTRS)

    O'Brien, Walter F. (Inventor); Billingsley, Matthew C. (Inventor); Sanders, Darius D. (Inventor); Schetz, Joseph A. (Inventor)

    2009-01-01

    Preheating of fuel and injection into a plasma torch plume fro adjacent the plasma torch plume provides for only ignition with reduced delay but improved fuel-air mixing and fuel atomization as well as combustion reaction enhancement. Heat exchange also reduced erosion of the anode of the plasma torch. Fuel mixing atomization, fuel mixture distribution enhancement and combustion reaction enhancement are improved by unsteady plasma torch energization, integral formation of the heat exchanger, fuel injection nozzle and plasma torch anode in a more compact, low-profile arrangement which is not intrusive on a highspeed air flow with which the invention is particularly effective and further enhanced by use of nitrogen as a feedstock material and inclusion of high pressure gases in the fuel to cause effervescence during injection.

  20. Embryonic oxygen enhances learning ability in hatchling lizards

    PubMed Central

    2014-01-01

    Introduction Producing smart offspring is an important fitness trait; individuals with enhanced cognitive ability should be more adept at responding to complex environmental demands. Cognitive ability can be influenced by conditions experienced during embryonic development. Although oxygen is necessary for embryonic development, availability can be limited within the nest environment because of substrate type, hydric conditions, and temperature. We do not yet understand, however, whether oxygen availability during embryonic development influences offspring fitness, especially cognitive ability. To address this question we incubated Mongolian Racerunner lizard (Eremias argus) eggs under hypoxic (12% O2), normoxic (21% O2), and hyperoxic conditions (30% O2). Results Hypoxia not only slowed hatching time, but also resulted in constrained cognitive ability relative to hatchlings experiencing normoxic or hyperoxic incubation conditions. Oxygen did not influence hatching success, body size or sprint speed of hatchlings. Conclusions Oxygen availability during embryonic development has important influences on incubation duration and cognitive ability of hatchling lizards. This study provides the first evidence that oxygen availability during embryonic development can modify cognitive ability of oviparous reptiles. PMID:24589451

  1. Highly Efficient Oxygen-Storage Material with Intrinsic Coke Resistance for Chemical Looping Combustion-Based CO2 Capture.

    PubMed

    Imtiaz, Qasim; Kurlov, Alexey; Rupp, Jennifer Lilia Marguerite; Müller, Christoph Rüdiger

    2015-06-22

    Chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) are emerging thermochemical CO2 capture cycles that allow the capture of CO2 with a small energy penalty. Here, the development of suitable oxygen carrier materials is a key aspect to transfer these promising concepts to practical installations. CuO is an attractive material for CLC and CLOU because of its high oxygen-storage capacity (20 wt %), fast reaction kinetics, and high equilibrium partial pressure of oxygen at typical operating temperatures (850-1000 °C). However, despite its promising characteristics, its low Tammann temperature requires the development of new strategies to phase-stabilize CuO-based oxygen carriers. In this work, we report a strategy based on stabilization by co-precipitated ceria (CeO2-x ), which allowed us to increase the oxygen capacity, coke resistance, and redox stability of CuO-based oxygen carriers substantially. The performance of the new oxygen carriers was evaluated in detail and compared to the current state-of-the-art materials, that is, Al2 O3 -stabilized CuO with similar CuO loadings. We also demonstrate that the higher intrinsic oxygen uptake, release, and mobility in CeO2-x -stabilized CuO leads to a three times higher carbon deposition resistance compared to that of Al2 O3 -stabilized CuO. Moreover, we report a high cyclic stability without phase intermixing for CeO2-x -supported CuO. This was accompanied by a lower reduction temperature compared to state-of-the-art Al2 O3 -supported CuO. As a result of its high resistance towards carbon deposition and fast oxygen uncoupling kinetics, CeO2-x -stabilized CuO is identified as a very promising material for CLC- and CLOU-based CO2 capture architectures.

  2. Determination of mercury in ash and soil samples by oxygen flask combustion method--cold vapor atomic fluorescence spectrometry (CVAFS).

    PubMed

    Geng, Wenhua; Nakajima, Tsunenori; Takanashi, Hirokazu; Ohki, Akira

    2008-06-15

    A simple method was developed for the determination of mercury (Hg) in coal fly ash (CFA), waste incineration ash (WIA), and soil by use of oxygen flask combustion (OFC) followed by cold vapor atomic fluorescence spectrometry (CVAFS). A KMnO4 solution was used as an absorbent in the OFC method, and the sample containing a combustion agent and an ash or soil sample was combusted by the OFC method. By use of Hg-free graphite as the combustion agent, the determination of Hg in ash and soil was successfully carried out; the Hg-free graphite was prepared by use of a mild pyrolysis procedure at 500 degrees C. For six certified reference materials (three CFA samples and three soil samples), the values of Hg obtained by this method were in good agreement with the certified or reference values. In addition, real samples including nine CFAs collected from some coal-fired power plants, five WIAs collected from waste incineration plants, and two soils were analyzed by the present method, and the data were compared to those from microwave-acid digestion (MW-AD) method.

  3. Liquid oxygen/hydrogen testing of a single swirl coaxial injector element in a windowed combustion chamber

    NASA Astrophysics Data System (ADS)

    Hulka, J.; Makel, D.

    1993-06-01

    A modular, high pressure, liquid rocket single element combustion chamber was developed at Aerojet for use with nonintrusive combustion diagnostics. The hardware is able to accommodate full-size injection elements and includes a recessed annular injector around the single element to provide a source for hot gas background flow, which reduces recirculation in the chamber and provides additional injection mass to elevate chamber pressure. Experiments are being conducted to develop the diagnostics required to characterize a single-element combustion spray field for combustion modeling, benchmark data for CFD model validation, and development of the transfer functions between single element cold flow and multielement hot fire. The latter task is being pursued using an injector element identical to elements that had been previously cold-flow tested in single element tests to ambient backpressure and hot fire tested in a multielement injector. Preliminary tests conducted to date without hydrogen flowing through the annular coaxial orifice of the single element show the general flow characteristics of a reacting, unconfined, liquid oxygen hollow cone swirl spray.

  4. Spiking of Hydrocarbon Fuels with Silanes-based Combustion Enhancers

    NASA Astrophysics Data System (ADS)

    Hidding, Bernhard; Fikri, Mustapha; Bozkurt, Metehan; Schulz, Christof; Soltner, Theresa; Kornath, Andreas; Pfitzner, Michael; Lang, Martin; Adamczyk, Andrew J.; Broadbelt, Linda; Ellerbrock, Hartwig; Simone, Domenico; Bruno, Claudio

    The concept of spiking hydrocarbon fuels such as kerosenes with liquid silicon hydrides in order to render the fuel combination hypergolic and to improve the combustion efficiency is presented and preliminarily analyzed. In view of scarcity of available data, various approaches are used, among them quantum-mechanical ab initio calculations for the thermodynamics and shock-tube measurements for the kinetics of higher, liquid silanes. Based on these results and other data, performance predictions indicate that miscible hydrocarbon/silicon hydride fuels (HC/SH) have the potential to be stored in a single tank, to be hypergolic with many oxidizers, and to yield similar, partly better specific impulses (and volume-specific impulses) than hydrocarbon fuels without silane additives. A variety of hybrid HC/SH fuel combinations seems to be accessible, which might offer the possibility to design a fuel combination with characteristics adjustable in a wide range. The current and future availability of larger amounts of liquid silanes is discussed.

  5. Analytical chemical kinetic investigation of the effects of oxygen, hydrogen, and hydroxyl radicals on hydrogen-air combustion

    NASA Technical Reports Server (NTRS)

    Carson, G. T., Jr.

    1974-01-01

    Quantitative values were computed which show the effects of the presence of small amounts of oxygen, hydrogen, and hydroxyl radicals on the finite-rate chemical kinetics of premixed hydrogen-air mixtures undergoing isobaric autoignition and combustion. The free radicals were considered to be initially present in hydrogen-air mixtures at equivalence ratios of 0.2, 0.6, 1.0, and 1.2. Initial mixture temperatures were 1100 K, 1200 K, and 1500 K, and pressures were 0.5, 1.0, 2.0, and 4.0 atm. Of the radicals investigated, atomic oxygen was found to be the most effective for reducing induction time, defined as the time to 5 percent of the total combustion temperature rise. The reaction time, the time between 5 percent and 95 percent of the temperature rise, is not decreased by the presence of free radicals in the initial hydrogen-air mixture. Fuel additives which yield free radicals might be used to effect a compact supersonic combustor design for efficient operation in an otherwise reaction-limited combustion regime.

  6. Particulate Formation from a Copper Oxide-Based Oxygen Carrier in Chemical Looping Combustion for CO2 Capture.

    PubMed

    He, Feng; Linak, William P; Deng, Shuang; Li, Fanxing

    2017-02-21

    Attrition behavior and particle loss of a copper oxide-based oxygen carrier from a methane chemical looping combustion (CLC) process was investigated in a fluidized bed reactor. The aerodynamic diameters of most elutriated particulates, after passing through a horizontal settling duct, range between 2 and 5 μm. A notable number of submicrometer particulates are also identified. Oxygen carrier attrition was observed to lead to increased CuO loss resulting from the chemical looping reactions, i.e., Cu is enriched in small particles generated primarily from fragmentation in the size range of 10-75 μm. Cyclic reduction and oxidation reactions in CLC have been determined to weaken the oxygen carrier particles, resulting in increased particulate emission rates when compared to those of oxygen carriers without redox reactions. The generation rate for particulates <10 μm was found to decrease with progressive cycles over as-prepared oxygen carrier particles and then reach a steady state. The surface of the oxygen carrier is also found to be coarsened due to a Kirkendall effect, which also explains the enrichment of Cu on particle surfaces and in small particles.

  7. Determination of total iodine in nutritional and biological samples by ICP-MS following their combustion within an oxygen stream.

    PubMed

    Gélinas, Y; Krushevska, A; Barnes, R M

    1998-03-01

    A mineralization and determination method for total iodine in nutritional and biological samples is described. Combustion of the sample in an oxygen stream is followed by collection of the combustion products in a 5% water-soluble tertiary amine solution. Iodine is determined by inductively coupled plasma mass spectrometry. The accuracy and precision of the quantitative iodine analysis using standard addition is better than +/- 10%. A semi-quantitative analysis of four standard reference materials is evaluated. Owing to the presence of low-level iodine contaminant in the blank solution, the determination limit of the method is +/- 10 micrograms kg-1. Good agreement with certified iodine values is obtained for six reference materials. The use of the tertiary amine matrix solution permits the simultaneous determination of iodine and other trace metals of biological and toxicological importance, including Mn, Co, Ni, Cu, Zn, Rb, Cd, and Pb.

  8. Vapor hydrogen and oxygen isotopes reflect water of combustion in the urban atmosphere

    NASA Astrophysics Data System (ADS)

    Gorski, Galen; Strong, Courtenay; Good, Stephen P.; Bares, Ryan; Ehleringer, James R.; Bowen, Gabriel J.

    2015-03-01

    Anthropogenic modification of the water cycle involves a diversity of processes, many of which have been studied intensively using models and observations. Effective tools for measuring the contribution and fate of combustion-derived water vapor in the atmosphere are lacking, however, and this flux has received relatively little attention. We provide theoretical estimates and a first set of measurements demonstrating that water of combustion is characterized by a distinctive combination of H and O isotope ratios. We show that during periods of relatively low humidity and/or atmospheric stagnation, this isotopic signature can be used to quantify the concentration of water of combustion in the atmospheric boundary layer over Salt Lake City. Combustion-derived vapor concentrations vary between periods of atmospheric stratification and mixing, both on multiday and diurnal timescales, and respond over periods of hours to variations in surface emissions. Our estimates suggest that up to 13% of the boundary layer vapor during the period of study was derived from combustion sources, and both the temporal pattern and magnitude of this contribution were closely reproduced by an independent atmospheric model forced with a fossil fuel emissions data product. Our findings suggest potential for water vapor isotope ratio measurements to be used in conjunction with other tracers to refine the apportionment of urban emissions, and imply that water vapor emissions associated with combustion may be a significant component of the water budget of the urban boundary layer, with potential implications for urban climate, ecohydrology, and photochemistry.

  9. Vapor hydrogen and oxygen isotopes reflect water of combustion in the urban atmosphere

    PubMed Central

    Gorski, Galen; Strong, Courtenay; Good, Stephen P.; Bares, Ryan; Ehleringer, James R.; Bowen, Gabriel J.

    2015-01-01

    Anthropogenic modification of the water cycle involves a diversity of processes, many of which have been studied intensively using models and observations. Effective tools for measuring the contribution and fate of combustion-derived water vapor in the atmosphere are lacking, however, and this flux has received relatively little attention. We provide theoretical estimates and a first set of measurements demonstrating that water of combustion is characterized by a distinctive combination of H and O isotope ratios. We show that during periods of relatively low humidity and/or atmospheric stagnation, this isotopic signature can be used to quantify the concentration of water of combustion in the atmospheric boundary layer over Salt Lake City. Combustion-derived vapor concentrations vary between periods of atmospheric stratification and mixing, both on multiday and diurnal timescales, and respond over periods of hours to variations in surface emissions. Our estimates suggest that up to 13% of the boundary layer vapor during the period of study was derived from combustion sources, and both the temporal pattern and magnitude of this contribution were closely reproduced by an independent atmospheric model forced with a fossil fuel emissions data product. Our findings suggest potential for water vapor isotope ratio measurements to be used in conjunction with other tracers to refine the apportionment of urban emissions, and imply that water vapor emissions associated with combustion may be a significant component of the water budget of the urban boundary layer, with potential implications for urban climate, ecohydrology, and photochemistry. PMID:25733906

  10. Enhanced spin orbit torques by oxygen incorporation in tungsten films

    NASA Astrophysics Data System (ADS)

    Phung, Timothy; Demasius, Kai-Uwe; Zhang, Weifeng; Hughes, Brian P.; Yang, See-Hun; Kellock, Andrew; Han, Wei; Pushp, Aakash; Parkin, Stuart S. P.

    Spin orbit torques are generated by the conversion of charge to spin currents in non-magnetic materials. The origin of these torques is of considerable debate. One of the most interesting materials is metallic tungsten for which large spin orbit torques have been found in thin films that are stabilized in the A15 (β-phase) structure. Here we report, using spin transfer torque ferromagnetic resonance, large spin Hall angles of up to ~-0.5 by incorporating oxygen into tungsten films. Whilst the incorporation of oxygen into the tungsten leads to significant changes in its microstructure and electrical resistivity, the large spin Hall angles measured are found to be remarkably insensitive to the oxygen doping level (12-44%). This invariance of the spin Hall angle with the bulk W(O) properties for higher oxygen concentrations suggests that the spin orbit torques in this system may actually be partly interfacial in origin, and induced by scattering of the electrons at the W(O) |CoFeB interface rather than from the interior of the W(O) film. Our results show an intriguing novel path towards enhanced spin orbit torques.

  11. Mechanism of singlet oxygen chemiluminescence enhancement by human serum albumin

    NASA Astrophysics Data System (ADS)

    Zhou, Jing; Xing, Da; Chen, Qun

    2006-02-01

    Fluoresceinyl Cypridina Luciferin Analog (FCLA) is a chemiluminescence (CL) probe for detecting reactive oxygen species (ROS). Its detection efficiency of singlet oxygen can be significantly enhanced in the presence of human serum albumin (HSA). In the current study, the mechanism of the FCLA-HSA CL system is studied by means of direct CL measurement and spectroscopy techniques. Our results show that FCLA can combine with HSA via a single binding site to form a complex. The CL efficiency of the system is largely governed by an inter-system energy transfer between the two components upon interaction with singlet oxygen. The CL production reaches maximum in a synergetic manner when equal amount of FCLA and HSA are present simultaneously, but the production is less efficient at other ratios. This suggests that the FCLA-HSA system maybe used as a singlet oxygen detecting technique with higher sensitivity compared with that of conventional CL techniques. It may also provide a potential new technique for quantitatively analyze the presence of HSA in a sample.

  12. Oxygen functional groups in graphitic carbon nitride for enhanced photocatalysis.

    PubMed

    Liu, Shizhen; Li, Degang; Sun, Hongqi; Ang, Ha Ming; Tadé, Moses O; Wang, Shaobin

    2016-04-15

    Metal-free semiconductors offer a new opportunity for environmental photocatalysis toward a potential breakthrough in high photo efficiency with complete prevention of metal leaching. In this study, graphitic carbon nitride (GCN) modified by oxygen functional groups was synthesized by a hydrothermal treatment of pristine GCN at different temperatures with H2O2. Insights into the emerging characteristics of the modified GCN in photocatalysis were obtained by determining the optical properties, band structure, electrochemical activity and pollutant degradation efficiency. It was found that the introduction of GCN with oxygen functional groups can enhance light absorption and accelerate electron transfer so as to improve the photocatalytic reaction efficiency. The photoinduced reactive radicals and the associated photodegradation were investigated by in situ electron paramagnetic resonance (EPR). The reactive radicals, O2(-) and OH, were responsible for organic degradation.

  13. Development of Nanofiller-Modulated Polymeric Oxygen Enrichment Membranes for Reduction of Nitrogen Oxides in Coal Combustion

    SciTech Connect

    Jianzhong Lou; Shamsuddin Ilias

    2010-12-31

    North Carolina A&T State University in Greensboro, North Carolina, has undertaken this project to develop the knowledge and the material to improve the oxygen-enrichment polymer membrane, in order to provide high-grade oxygen-enriched streams for coal combustion and gasification applications. Both experimental and theoretical approaches were used in this project. The membranes evaluated thus far include single-walled carbon nano-tube, nano-fumed silica polydimethylsiloxane (PDMS), and zeolite-modulated polyimide membranes. To document the nanofiller-modulated polymer, molecular dynamics simulations have been conducted to calculate the theoretical oxygen molecular diffusion coefficient and nitrogen molecular coefficient inside single-walled carbon nano-tube PDMS membranes, in order to predict the effect of the nano-tubes on the gas-separation permeability. The team has performed permeation and diffusion experiments using polymers with nano-silica particles, nano-tubes, and zeolites as fillers; studied the influence of nano-fillers on the self diffusion, free volume, glass transition, oxygen diffusion and solubility, and perm-selectivity of oxygen in polymer membranes; developed molecular models of single-walled carbon nano-tube and nano-fumed silica PDMS membranes, and zeolites-modulated polyimide membranes. This project partially supported three graduate students (two finished degrees and one transferred to other institution). This project has resulted in two journal publications and additional publications will be prepared in the near future.

  14. Shock enhancement and control of hypersonic mixing and combustion

    NASA Technical Reports Server (NTRS)

    Marble, Frank E.; Zukoski, Edward E.; Jacobs, Jeffrey; Hendricks, Gavin; Waitz, Ian

    1990-01-01

    Experimental and computational analyses of the possibility that shock-enhanced mixing can substantially increase the rate of mixing between coflowing streams of hydrogen and air are discussed. Numerical computations indicate that the steady interaction between a weak shock in air with a coflowing hydrogen jet can be approximated by the two-dimensional time-dependent interaction between a weak shock and an initially circular region filled with hydrogen imbedded in air. Experimental results obtained in a shock tube and contoured wall injector are presented. It is shown that the shock impinging process causes the light gas cylinder to split into two parts; one of these mixes rapidly with air and the other forms a stably stratified vortex pair which mixes more slowly. The geometry of the flow field and the mixing process and scaling parameters are assessed.

  15. Thermochemical conversion of biomass in smouldering combustion across scales: The roles of heterogeneous kinetics, oxygen and transport phenomena.

    PubMed

    Huang, Xinyan; Rein, Guillermo

    2016-05-01

    The thermochemical conversion of biomass in smouldering combustion is investigated here by combining experiments and modeling at two scales: matter (1mg) and bench (100g) scales. Emphasis is put on the effect of oxygen (0-33vol.%) and oxidation reactions because these are poorly studied in the literature in comparison to pyrolysis. The results are obtained for peat as a representative biomass for which there is high-quality experimental data published previously. Three kinetic schemes are explored, including various steps of drying, pyrolysis and oxidation. The kinetic parameters are found using the Kissinger-Genetic Algorithm method, and then implemented in a one-dimensional model of heat and mass transfer. The predictions are validated with thermogravimetric and bench-scale experiments and then analyzed to unravel the role of heterogeneous reaction. This is the first time that the influence of oxygen on biomass smouldering is explained in terms of both chemistry and transport phenomena across scales.

  16. Modeling of the chemical-looping combustion of methane using a Cu-based oxygen-carrier

    SciTech Connect

    Abad, Alberto; Adanez, Juan; Garcia-Labiano, Francisco; de Diego, Luis F.; Gayan, Pilar

    2010-03-15

    A mathematical model for a bubbling fluidized bed has been developed to simulate the performance of the fuel-reactor in chemical-looping combustion (CLC) systems. This model considers both the fluid dynamic of the fluidized bed and freeboard and the kinetics of reduction of the oxygen-carrier, here CuO impregnated on alumina. The main outputs of the model are the conversion of the carrier and the gas composition at the reactor exit, the axial profiles of gas concentrations and the fluid dynamical structure of the reactor. The model was validated using measurements when burning CH{sub 4} in a 10 kW{sub th} prototype using a Cu-based oxygen-carrier. The influence of the circulation rate of solids, the load of fuel gas, the reactor temperature and size of the oxygen-carrier particles were analyzed. Combustion efficiencies predicted by the model showed a good agreement with measurements. Having validated the model, the implications for designing and optimizing a fuel-reactor were as follows. The inventory of solids for a high conversion of the fuel was sensitive to the reactor's temperature, the solids' circulation rate and the extent to which the solids entering to the reactor had been regenerated. The optimal ratio of oxygen-carrier to fuel was found to be 1.7-4 for the Cu-based oxygen-carrier used here. In this range, the inventory of solids to obtain a combustion efficiency of 99.9% at 1073 K was less than 130 kg/MW{sub th}. In addition, the model's results were very sensitive to the resistance to gas diffusing between the emulsion and bubble phases in the bed, to the decay of solids' concentration in the freeboard and to the efficiency contact between gas and solids in the freeboard. Thus, a simplified model, ignoring any restriction to gas and solids contacting each other, will under-predict the inventory of solids by a factor of 2-10. (author)

  17. Analysis of the laser ignition of methane/oxygen mixtures in a sub-scale rocket combustion chamber

    NASA Astrophysics Data System (ADS)

    Wohlhüter, Michael; Zhukov, Victor P.; Sender, Joachim; Schlechtriem, Stefan

    2016-12-01

    The laser ignition of methane/oxygen mixtures in a sub-scale rocket combustion chamber has been investigated numerically and experimentally. The ignition test case used in the present paper was generated during the In-Space Propulsion project (ISP-1), a project focused on the operation of propulsion systems in space, the handling of long idle periods between operations, and multiple reignitions under space conditions. Regarding the definition of the numerical simulation and the suitable domain for the current model, 2D and 3D simulations have been performed. Analysis shows that the usage of a 2D geometry is not suitable for this type of simulation, as the reduction of the geometry to a 2D domain significantly changes the conditions at the time of ignition and subsequently the flame development. The comparison of the numerical and experimental results shows a strong discrepancy in the pressure evolution and the combustion chamber pressure peak following the laser spark. The detailed analysis of the optical Schlieren and OH data leads to the conclusion that the pressure measurement system was not able to capture the strong pressure increase and the peak value in the combustion chamber during ignition. Although the timing in flame development following the laser spark is not captured appropriately, the 3D simulations reproduce the general ignition phenomena observed in the optical measurement systems, such as pressure evolution and injector flow characteristics.

  18. Investigation of coal fueled chemical looping combustion using Fe3O4 as oxygen carrier: Influence of variables

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoyan; Xiang, Wenguo; Wang, Sha; Tian, Wendong; Xu, Xiang; Xu, Yanji; Xiao, Yunhan

    2010-06-01

    Chemical-looping combustion (CLC) is a novel combustion technique with inherent CO2 separation. Magnetite (Fe3O4) was selected as the oxygen carrier. Shenhua coal (Inner Mongolia, China), straw coke and natural coke were used as fuels for this study. Influences of operation temperatures, coal to Fe3O4 mass ratios, and different kinds of fuels on the reduction characteristics of the oxygen carrier were investigated using an atmosphere thermogravimetric analyzer (TGA). Scanning electron microscopy (SEM) was used to analyse the characteristic of the solid residues. Experimental results shown that the reaction between the coal and the oxygen carrier become strong at a temperature of higher than 800°C. As the operation temperature rises, the reduction conversion rate increases. At the temperatures of 850°C, 900°C, and 950°C, the reduction conversion rates were 37.1%, 46.5%, and 54.1% respectively. However, SEM images show that at the temperature of higher than 950°C, the iron oxides become melted and sintered. The possible operation temperature should be kept around 900°C. When the mass ratios of coal to Fe3O4 were 5/95, 10/90, 15/85, and 20/80, the reduction conversion rates were 29.5%, 40.8%, 46.5%, and 46.6% respectively. With the increase of coal, the conversion rate goes up. But there exist an optimal ratio around 15/85. Comparisons based on different kinds of fuels show that the solid fuel with a higher volatile and a more developed pore structure is conducive to the reduction reactivity of the oxygen carrier.

  19. Combustion Enhancement of Liquid Fuels via Nanoparticle Additions: Screening, Dispersion, and Characterization

    DTIC Science & Technology

    2015-06-04

    affordability of a large variety of nano-sized particles, understanding of nano-sized particle ignition and combustion, and advances in colloidal science of...generate a suitable long-term stable colloidal suspension. 15. SUBJECT TERMS N/A 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18...advances in colloidal science of nano-sized metal particle/liquid suspensions, now allow for the development of enhanced nano-fluid fuels. To evaluate

  20. Determination of fluorine, chlorine and bromine in household products by means of oxygen bomb combustion and ion chromatography.

    PubMed

    Zhang, Shuai; Zhao, Tianbo; Wang, Jia; Qu, Xiaoling; Chen, Wei; Han, Yin

    2013-01-01

    A method for routine determination of fluorine, chlorine and bromine in household products was developed and validated. In this work, halogen analyses were made based on oxygen bomb combustion followed by ion chromatography (IC). The chromatographic analysis was performed by an IonPac AS19 hydroxide-selective anion-exchange column, a reagent free ion chromatograph eluent generator and an anion self-regenerating suppressor in 10 min. The response was linear (r ≥ 0.9995) in the entire investigated domain. The limit of detection for the halogens was in the range of 2 to 9 × 10(-3) mg/L and the limit of quantification was lower than 8 mg/Kg with 20 µL of injection volume. The certified reference material of ERM-EC 681k was pretreated using an oxygen bomb combustion procedure to demonstrate the precision of the proposed method. The quantitative analysis results obtained by IC for the target elements were 797 ± 9 mg/Kg chlorine and 786 ± 25 mg/Kg bromine, which were in good agreement with the certified values of 800 ± 4 mg/Kg chlorine, 770 ± 5 mg/Kg bromine for ERM-EC 681k, respectively. This validated method was successfully applied for the analysis of fluorine, chlorine and bromine in household product samples, and the variation of halogen contained among the tested samples was remarkable.

  1. High-pressure calorimeter chamber tests for liquid oxygen/kerosene (LOX/RP-1) rocket combustion

    NASA Technical Reports Server (NTRS)

    Masters, Philip A.; Armstrong, Elizabeth S.; Price, Harold G.

    1988-01-01

    An experimental program was conducted to investigate the rocket combustion and heat transfer characteristics of liquid oxygen/kerosene (LOX/RP-1) mixtures at high chamber pressures. Two water-cooled calorimeter chambers of different combustion lengths were tested using 37- and 61-element oxidizer-fuel-oxidizer triplet injectors. The tests were conducted at nominal chamber pressures of 4.1, 8.3, and 13.8 MPa abs (600, 1200, and 2000 psia). Heat flux Q/A data were obtained for the entire calorimeter length for oxygen/fuel mixture ratios of 1.8 to 3.3. Test data at 4.1 MPa abs compared favorably with previous test data from another source. Using an injector with a fuel-rich outer zone reduced the throat heat flux by 47 percent with only a 4.5 percent reduction in the characteristic exhaust velocity efficiency C* sub eff. The throat heat transfer coefficient was reduced approximately 40 percent because of carbon deposits on the chamber wall.

  2. Enhanced deep ocean ventilation and oxygenation with global warming

    NASA Astrophysics Data System (ADS)

    Froelicher, T. L.; Jaccard, S.; Dunne, J. P.; Paynter, D.; Gruber, N.

    2014-12-01

    Twenty-first century coupled climate model simulations, observations from the recent past, and theoretical arguments suggest a consistent trend towards warmer ocean temperatures and fresher polar surface oceans in response to increased radiative forcing resulting in increased upper ocean stratification and reduced ventilation and oxygenation of the deep ocean. Paleo-proxy records of the warming at the end of the last ice age, however, suggests a different outcome, namely a better ventilated and oxygenated deep ocean with global warming. Here we use a four thousand year global warming simulation from a comprehensive Earth System Model (GFDL ESM2M) to show that this conundrum is a consequence of different rates of warming and that the deep ocean is actually better ventilated and oxygenated in a future warmer equilibrated climate consistent with paleo-proxy records. The enhanced deep ocean ventilation in the Southern Ocean occurs in spite of increased positive surface buoyancy fluxes and a constancy of the Southern Hemisphere westerly winds - circumstances that would otherwise be expected to lead to a reduction in deep ocean ventilation. This ventilation recovery occurs through a global scale interaction of the Atlantic Meridional Overturning Circulation undergoing a multi-centennial recovery after an initial century of transient decrease and transports salinity-rich waters inform the subtropical surface ocean to the Southern Ocean interior on multi-century timescales. The subsequent upwelling of salinity-rich waters in the Southern Ocean strips away the freshwater cap that maintains vertical stability and increases open ocean convection and the formation of Antarctic Bottom Waters. As a result, the global ocean oxygen content and the nutrient supply from the deep ocean to the surface are higher in a warmer ocean. The implications for past and future changes in ocean heat and carbon storage will be discussed.

  3. Hot-Fire Test Results of an Oxygen/RP-2 Multi-Element Oxidizer-Rich Staged-Combustion Integrated Test Article

    NASA Technical Reports Server (NTRS)

    Hulka, J. R.; Protz, C. S.; Garcia, C. P.; Casiano, M. J.; Parton, J. A.

    2016-01-01

    As part of the Combustion Stability Tool Development project funded by the Air Force Space and Missile Systems Center, the NASA Marshall Space Flight Center was contracted to assemble and hot-fire test a multi-element integrated test article demonstrating combustion characteristics of an oxygen/hydrocarbon propellant oxidizer-rich staged-combustion engine thrust chamber. Such a test article simulates flow through the main injectors of oxygen/kerosene oxidizer-rich staged combustion engines such as the Russian RD-180 or NK-33 engines, or future U.S.-built engine systems such as the Aerojet-Rocketdyne AR-1 engine or the Hydrocarbon Boost program demonstration engine. For the thrust chamber assembly of the test article, several configurations of new main injectors, using relatively conventional gas-centered swirl coaxial injector elements, were designed and fabricated. The design and fabrication of these main injectors are described in a companion paper at this JANNAF meeting. New ablative combustion chambers were fabricated based on hardware previously used at NASA for testing at similar size and pressure. An existing oxygen/RP-1 oxidizer-rich subscale preburner injector from a previous NASA-funded program, along with existing and new inter-connecting hot gas duct hardware, were used to supply the oxidizer-rich combustion products to the oxidizer circuit of the main injector of the thrust chamber. Results from independent hot-fire tests of the preburner injector in a combustion chamber with a sonic throat are described in companion papers at this JANNAF conference. The resulting integrated test article - which includes the preburner, inter-connecting hot gas duct, main injector, and ablative combustion chamber - was assembled at Test Stand 116 at the East Test Area of the NASA Marshall Space Flight Center. The test article was well instrumented with static and dynamic pressure, temperature, and acceleration sensors to allow the collected data to be used for

  4. Physics and chemistry of the influence of excited molecules on combustion enhancement

    PubMed Central

    Starik, A. M.; Loukhovitski, B. I.; Sharipov, A. S.; Titova, N. S

    2015-01-01

    The paper addresses detailed analysis of kinetic processes in the H2−O2, CO−O2 and CH4−O2-reactive systems upon the presence of singlet oxygen molecules O2(a1Δg) and and the influence of the activation of oxygen molecules in electric discharge on the acceleration of ignition in the H2−O2 and CH4−O2 mixtures. The possibility of the intensification of CO oxidation due to excitation of O2 and N2 molecule vibrations and generation of singlet oxygen molecules is also considered. It is shown that the effect of accelerating the ignition strongly depends on the reduced electric field and, as a consequence, on the composition of discharge plasma as well as on the features of chain mechanism development in oxy-fuel systems. It is revealed that the most effective approach for the intensification of CO oxidation both in the moist air and in the products of hydrocarbon combustion in air is the generation of O2(a1Δg) molecules by electric discharge. Computations showed that the presence of 1% O2(a1Δg) in the total oxygen allowed one to convert CO to CO2 even at the temperature T=850–900 K in the time of 10−2 s. The excitation of O2 and N2 molecule vibrations is less effective for such a conversion. PMID:26170425

  5. Solid Fuel - Oxygen Fired Combustion for Production of Nodular Reduced Iron to Reduce CO2 Emissions and Improve Energy Efficiencies

    SciTech Connect

    Donald R. Fosnacht; Richard F. Kiesel; David W. Hendrickson; David J. Englund; Iwao Iwasaki; Rodney L. Bleifuss; Mathew A. Mlinar

    2011-12-22

    The current trend in the steel industry is an increase in iron and steel produced in electric arc furnaces (EAF) and a gradual decline in conventional steelmaking from taconite pellets in blast furnaces. In order to expand the opportunities for the existing iron ore mines beyond their blast furnace customer base, a new material is needed to satisfy the market demands of the emerging steel industry while utilizing the existing infrastructure and materials handling capabilities. This demand creates opportunity to convert iron ore or other iron bearing materials to Nodular Reduced Iron (NRI) in a recently designed Linear Hearth Furnace (LHF). NRI is a metallized iron product containing 98.5 to 96.0% iron and 2.5 to 4% C. It is essentially a scrap substitute with little impurity that can be utilized in a variety of steelmaking processes, especially the electric arc furnace. The objective of this project was to focus on reducing the greenhouse gas emissions (GHG) through reducing the energy intensity using specialized combustion systems, increasing production and the use of biomass derived carbon sources in this process. This research examined the use of a solid fuel-oxygen fired combustion system and compared the results from this system with both oxygen-fuel and air-fuel combustion systems. The solid pulverized fuels tested included various coals and a bio-coal produced from woody biomass in a specially constructed pilot scale torrefaction reactor at the Coleraine Minerals Research Laboratory (CMRL). In addition to combustion, the application of bio-coal was also tested as a means to produce a reducing atmosphere during key points in the fusion process, and as a reducing agent for ore conversion to metallic iron to capture the advantage of its inherent reduced carbon footprint. The results from this study indicate that the approaches taken can reduce both greenhouse gas emissions and the associated energy intensity with the Linear Hearth Furnace process for converting

  6. Turbulence in a gaseous hydrogen-liquid oxygen rocket combustion chamber

    NASA Technical Reports Server (NTRS)

    Lebas, J.; Tou, P.; Ohara, J.

    1975-01-01

    The intensity of turbulence and the Lagrangian correlation coefficient for a LOX-GH2 rocket combustion chamber was determined from experimental measurements of tracer gas diffusion. A combination of Taylor's turbulent diffusion theory and a numerical method for solving the conservation equations of fluid mechanics was used to calculate these quantities. Taylor's theory was extended to consider the inhomogeneity of the turbulence field in the axial direction of the combustion chamber, and an exponential function was used to represent the Lagrangian correlation coefficient. The results indicate that the value of the intensity of turbulence reaches a maximum of 14% at a location about 7" downstream from the injector. The Lagrangian correlation coefficient associated with this value is given by the above exponential expression where alpha = 10,000/sec.

  7. Preliminary Study of Oxygen-Enhanced Longitudinal Relaxation in MRI: A Potential Novel Biomarker of Oxygenation Changes in Solid Tumors

    SciTech Connect

    O'Connor, James P.B.; Naish, Josephine H.; Parker, Geoff J.M.; Waterton, John C.; Watson, Yvonne; Jayson, Gordon C.; Buonaccorsi, Giovanni A.; Cheung, Sue; Buckley, David L.; McGrath, Deirdre M.; West, Catharine M.L.; Davidson, Susan E.; Roberts, Caleb; Mills, Samantha J.; Mitchell, Claire L.; Hope, Lynn; Ton, N. Chan; Jackson, Alan

    2009-11-15

    Purpose: There is considerable interest in developing non-invasive methods of mapping tumor hypoxia. Changes in tissue oxygen concentration produce proportional changes in the magnetic resonance imaging (MRI) longitudinal relaxation rate (R{sub 1}). This technique has been used previously to evaluate oxygen delivery to healthy tissues and is distinct from blood oxygenation level-dependent (BOLD) imaging. Here we report application of this method to detect alteration in tumor oxygenation status. Methods and materials: Ten patients with advanced cancer of the abdomen and pelvis underwent serial measurement of tumor R{sub 1} while breathing medical air (21% oxygen) followed by 100% oxygen (oxygen-enhanced MRI). Gadolinium-based dynamic contrast-enhanced MRI was then performed to compare the spatial distribution of perfusion with that of oxygen-induced DELTAR{sub 1}. Results: DELTAR{sub 1} showed significant increases of 0.021 to 0.058 s{sup -1} in eight patients with either locally recurrent tumor from cervical and hepatocellular carcinomas or metastases from ovarian and colorectal carcinomas. In general, there was congruency between perfusion and oxygen concentration. However, regional mismatch was observed in some tumor cores. Here, moderate gadolinium uptake (consistent with moderate perfusion) was associated with low area under the DELTAR{sub 1} curve (consistent with minimal increase in oxygen concentration). Conclusions: These results provide evidence that oxygen-enhanced longitudinal relaxation can monitor changes in tumor oxygen concentration. The technique shows promise in identifying hypoxic regions within tumors and may enable spatial mapping of change in tumor oxygen concentration.

  8. The influence of oxygen concentration on the combustion of a fuel/oxidizer mixture

    SciTech Connect

    Biteau, H.; Fuentes, A.; Marlair, G.; Torero, J.L.

    2010-04-15

    The aim of the present study is to investigate the influence of the O{sub 2} concentration on the combustion behaviour of a fuel/oxidizer mixture. The material tested is a ternary mixture of lactose, starch, and potassium nitrate, which has already been used in an attempt to estimate heat release rate using the FM-Global Fire Propagation Apparatus. It provides a well-controlled combustion chamber to study the evolution of the combustion products when varying the O{sub 2} concentration, between air and low oxidizer conditions. Different chemical behaviours have been exhibited. When the O{sub 2} concentration was reduced beyond 18%, large variations were observed in the CO{sub 2} and CO concentrations. This critical O{sub 2} concentration seems to be the limit before which the material only uses its own oxidizer to react. On the other hand, mass loss did not highlight this change in chemical reactions and remained similar whatever the test conditions. This presumes that the oxidation of CO into CO{sub 2} are due to reactions occurring in the gas phase especially for large O{sub 2} concentrations. This actual behaviour can be verified using a simplified flammability limit model adapted for the current work. Finally, a sensitivity analysis has been carried out to underline the influence of CO concentration in the evaluation of heat release rate using typical calorimetric methods. The results of this study provide a critical basis for the investigation of the combustion of a fuel/oxidizer mixture and for the validation of future numerical models. (author)

  9. Resonant enhanced multiphoton ionization studies of atomic oxygen

    NASA Technical Reports Server (NTRS)

    Dixit, S. N.; Levin, D.; Mckoy, V.

    1987-01-01

    In resonant enhanced multiphoton ionization (REMPI), an atom absorbs several photons making a transition to a resonant intermediate state and subsequently ionizing out of it. With currently available tunable narrow-band lasers, the extreme sensitivity of REMPI to the specific arrangement of levels can be used to selectively probe minute amounts of a single species (atom) in a host of background material. Determination of the number density of atoms from the observed REMPI signal requires a knowledge of the multiphoton ionization cross sections. The REMPI of atomic oxygen was investigated through various excitation schemes that are feasible with available light sources. Using quantum defect theory (QDT) to estimate the various atomic parameters, the REMPI dynamics in atomic oxygen were studied incorporating the effects of saturation and a.c. Stark shifts. Results are presented for REMPI probabilities for excitation through various 2p(3) (4S sup o) np(3)P and 2p(3) (4S sup o) nf(3)F levels.

  10. Effect of Ozone Addition on Combustion Efficiency of Hydrogen: Liquid-Oxygen Propellant in Small Rockets

    NASA Technical Reports Server (NTRS)

    Miller, Riley O.; Brown, Dwight D.

    1959-01-01

    An experimental study shows that 2 percent by weight ozone in oxygen has little effect on overall reactivity for a range of oxidant-fuel weight ratios from 1 to 6. This conclusion is based on characteristic-velocity measurements in 200-pound-thrust chambers at a pressure of 300 pounds per square inch absolute with low-efficiency injectors. The presence of 9 percent ozone in oxygen also did not affect performance in an efficient chamber. Explosions were encountered when equipment or procedure permitted ozone to concentrate locally. These experiments indicate that even small amounts of ozone in oxygen can cause operational problems.

  11. Application of oxygen-enriched combustion for locomotive diesel engines. Phase 1

    SciTech Connect

    Poola, R.B.; Sekar, R.R.; Assanis, D.N.

    1996-09-01

    A thermodynamic simulation is used to study the effects of oxygen-enriched intake air on the performance and nitrogen oxide (NO) emissions of a locomotive diesel engine. The parasitic power of the air separation membrane required to supply the oxygen-enriched air is also estimated. For a given constraint on peak cylinder pressure, the gross and net power outputs of an engine operating under different levels of oxygen enrichment are compared with those obtained when a high-boost turbocharged engine is used. A 4% increase in peak cylinder pressure can result in an increase in net engine power of approximately 13% when intake air with an oxygen content of 28% by volume is used and fuel injection timing is retarded by 4 degrees. When the engine is turbocharged to a higher inlet boost, the same increase in peak cylinder pressure improves power by only 4%. If part of the significantly higher exhaust enthalpies available as a result of oxygen enrichment are recovered, the power requirements of the air separator membrane can be met, resulting in substantial net power improvements. Oxygen enrichment reduces particulate and visible smoke emissions but increases NO emissions. However, a combination of retarded fuel injection timing and post-treatment of exhaust gases may be adequate to meet the locomotive diesel engine NO{sub x} standards. Exhaust gas after-treatment and heat recovery would be required to realize the full potential of oxygen enrichment. Economic analysis shows that oxygen-enrichment technology is economically feasible and provides high returns on investment. The study also indicates the strong influence of membrane parasitic requirements and exhaust energy recovery on economic benefits. To obtain an economic advantage while using a membrane with higher parasitic power requirements, it is necessary to recover a part of the exhaust energy.

  12. Performance and Stability Characteristics of a Uni-Element Swirl Injector for Oxygen-Rich Stage Combustion Cycles

    NASA Technical Reports Server (NTRS)

    Pal, S.; Kalitan, D.; Woodward, R. D.; Santoro, R. J.

    2004-01-01

    A uni-element liquid propellant combustion performance and instability study for liquid RP-1 and hot oxygen-rich pre-burner products was conducted, at a chamber pressure of about 1000 psi. using flush and recessed swirl injectors. High-frequency pressure transducer measurements were analyzed to yield the characteristic frequencies which were compared to expected frequencies of the chamber. Modes, which were discovered to be present within the main chamber included, the first longitudinal, detected at approximately 1950 Hz, and the second longitudinal mode at approximately 3800 Hz. An additional first longitudinal quarter wave mode was measured at a frequency of approximately 23000 Hz for the recessed swirl injector configuration. The characteristic instabilities resulting from these experiments were relatively weak averaging 0.2% to 0.3% of the chamber pressure.

  13. Carbon deposition model for oxygen-hydrocarbon combustion. Task 6: Data analysis and formulation of an empirical model

    NASA Technical Reports Server (NTRS)

    Makel, Darby B.; Rosenberg, Sanders D.

    1990-01-01

    The formation and deposition of carbon (soot) was studied in the Carbon Deposition Model for Oxygen-Hydrocarbon Combustion Program. An empirical, 1-D model for predicting soot formation and deposition in LO2/hydrocarbon gas generators/preburners was derived. The experimental data required to anchor the model were identified and a test program to obtain the data was defined. In support of the model development, cold flow mixing experiments using a high injection density injector were performed. The purpose of this investigation was to advance the state-of-the-art in LO2/hydrocarbon gas generator design by developing a reliable engineering model of gas generator operation. The model was formulated to account for the influences of fluid dynamics, chemical kinetics, and gas generator hardware design on soot formation and deposition.

  14. Determination of Local Experimental Heat-Transfer Coefficients on Combustion Side of an Ammonia-Oxygen Rocket

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Ehlers, Robert C.

    1961-01-01

    Local experimental heat-transfer coefficients were measured in the chamber and throat of a 2400-pound-thrust ammonia-oxygen rocket engine with a nominal chamber pressure of 600 pounds per square inch absolute. Three injector configurations were used. The rocket engine was run over a range of oxidant-fuel ratio and chamber pressure. The injector that achieved the best performance also produced the highest rates of heat flux at design conditions. The heat-transfer data from the best-performing injector agreed well with the simplified equation developed by Bartz at the throat region. A large spread of data was observed for the chamber. This spread was attributed generally to the variations of combustion processes. The spread was least evident, however, with the best-performing injector.

  15. Mesoporous magnesium oxide nanoparticles derived via complexation-combustion for enhanced performance in carbon dioxide capture.

    PubMed

    Hiremath, Vishwanath; Shavi, Raghavendra; Gil Seo, Jeong

    2017-03-10

    Magnesium oxide (MgO) is a promising candidate for carbon dioxide (CO2) capture at high temperature applicable to pre-combustion capture in an integrated gasification combined cycle (IGCC) scheme. In this work, mesoporous MgO nanoparticles were synthesized via simple complexation-combustion method by using glycine (G) and urea (U) as fuels (F). The obtained sorbents were thoroughly characterized in terms of the crystalline structure, morphology, nature of the fuel, F/O ratio, and their consequent effects on CO2 sorption. It was observed that due to the complexation followed by combustion in the presence of glycine, MgO with crystallite size as small as∼8nm could be derived. The synthesized MgO nanoparticles exhibited exceptionally high CO2 sorption at elevated temperatures. Furthermore, CO2 sorption isotherms in assistance with FT-IR and DSC experiments demonstrated that the low CO2 uptake at ambient temperature (25-100°C) may be due to the formation of monodentate carbonates, whereas predominant bicarbonates enhance the CO2 uptake at elevated temperatures (100-300°C). MgO-1.5(G) obtained the highest sorption corresponding to 1.34mmol/g at 200°C.

  16. Sulfur evolution in chemical looping combustion of coal with MnFe2O4 oxygen carrier.

    PubMed

    Wang, Baowen; Gao, Chuchang; Wang, Weishu; Zhao, Haibo; Zheng, Chuguang

    2014-05-01

    Chemical looping combustion (CLC) of coal has gained increasing attention as a novel combustion technology for its advantages in CO2 capture. Sulfur evolution from coal causes great harm from either the CLC operational or environmental perspective. In this research, a combined MnFe2O4 oxygen carrier (OC) was synthesized and its reaction with a typical Chinese high sulfur coal, Liuzhi (LZ) bituminous coal, was performed in a thermogravimetric analyzer (TGA)-Fourier transform infrared (FT-IR) spectrometer. Evolution of sulfur species during reaction of LZ coal with MnFe2O4 OC was systematically investigated through experimental means combined with thermodynamic simulation. TGA-FTIR analysis of the LZ reaction with MnFe2O4 indicated MnFe2O4 exhibited the desired superior reactivity compared to the single reference oxides Mn3O4 or Fe2O3, and SO2 produced was mainly related to oxidization of H2S by MnFe2O4. Experimental analysis of the LZ coal reaction with MnFe2O4, including X-ray diffraction and X-ray photoelectron spectroscopy analysis, verified that the main reduced counterparts of MnFe2O4 were Fe3O4 and MnO, in good agreement with the related thermodynamic simulation. The obtained MnO was beneficial to stabilize the reduced MnFe2O4 and avoid serious sintering, although the oxygen in MnO was not fully utilized. Meanwhile, most sulfur present in LZ coal was converted to solid MnS during LZ reaction with MnFe2O4, which was further oxidized to MnSO4. Finally, the formation of both MnS and such manganese silicates as Mn2SiO4 and MnSiO3 should be addressed to ensure the full regeneration of the reduced MnFe2O4.

  17. Electron mobility enhancement in (100) oxygen-inserted silicon channel

    SciTech Connect

    Xu, Nuo; King Liu, Tsu-Jae; Takeuchi, Hideki; Hytha, Marek; Cody, Nyles W.; Stephenson, Robert J.; Mears, Robert J.; Kwak, Byungil; Cha, Seon Yong

    2015-09-21

    High performance improvement (+88% in peak G{sub m} and >30% in linear and saturation region drain currents) was observed for N-MOSFETs with Oxygen-Inserted (OI) Si channel. From TCAD analysis of the C-V measurement data, the improvement was confirmed to be due to electron mobility enhancement of the OI Si channel (+75% at N{sub inv} = 4.0 × 10{sup 12} cm{sup −2} and +25% at N{sub inv} = 8.0 × 10{sup 12} cm{sup −2}). Raman and high-resolution Rutherford backscattering measurements confirmed that negligible strain is induced in the OI Si layer, and hence, it cannot be used to explain the origin of mobility improvement. Poisson-Schrödinger based quantum mechanical simulation was performed, taking into account phonon, surface roughness and Coulomb scatterings. The OI layer was modeled as a “quasi barrier” region with reference to the Si conduction band edge to confine inversion electrons. Simulation explains the measured electron mobility enhancement as the confinement effect of inversion electrons while the formation of an super-steep retrograde well doping profile in the channel (as a result of dopant diffusion blocking effect accompanied by introduction of the OI layer) also contributes 50%–60% of the mobility improvement.

  18. Review of the PDWA Concept for Combustion Enhancement in a Supersonic Air-Breathing Combustor Environment

    NASA Technical Reports Server (NTRS)

    Canbier, Jean-Luc; Edwards, Thomas A. (Technical Monitor)

    1995-01-01

    This paper reviews the design of the Pulsed Detonation Wave Augmentor (PDWA) concept and the preliminary computational fluid dynamics studies that supported it. The PDWA relies on the rapid generation of detonation waves in a small tube, which are then injected into the supersonic stream of the main combustor. The blast waves thus generated are used to stimulate the mixing and combustion inside the main combustor. The mixing enhancement relies on various forms of the baroclinic interaction, where misaligned pressure and density gradients combine to produce vortical flow. By using unsteady shock waves, the concept also uses the Richtmyer-Meshkov effect to further increase the rate of mixing. By carefully designing the respective configurations of the combustor and the detonation tubes, one can also increase the penetration of the fuel into the supersonic air stream. The unsteady shocks produce lower stagnation pressure losses than steady shocks. Combustion enhancement can also be obtained through the transient shock-heating of the fuel-air interface, and the lowering of the ignition delay in these regions. The numerical simulations identify these processes, and show which configurations give the best results. Engineering considerations are also presented, and discuss the feasibility of the concept. Of primary importance are the enhancements in performance, the design simplicity, the minimization of the power, cost, and weight, and the methods to achieve very rapid cycling.

  19. Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustors

    NASA Technical Reports Server (NTRS)

    Ryan, T. W., III; Harlowe, W. W.; Schwab, S.

    1992-01-01

    The work was based on adapting an apparatus and procedure developed at Southwest Research Institute for rating the ignition quality of fuels for diesel engines. Aluminum alkyls and various Lewis-base adducts of these materials, both neat and mixed 50/50 with pure JP-10 hydrocarbon, were injected into the combustion bomb using a high-pressure injection system. The bomb was pre-charged with air that was set at various initial temperatures and pressures for constant oxygen density. The ignition delay times were determined for the test materials at these different initial conditions. The data are presented in absolute terms as well as comparisons with the parent alkyls. The relative heats of reaction of the various test materials were estimated based on a computation of the heat release, using the pressure data recorded during combustion in the bomb. In addition, the global reaction rates for each material were compared at a selected tmperature and pressure.

  20. Oxygen "getter" effects on microstructure and carrier transport in low temperature combustion-processed a-InXZnO (X = Ga, Sc, Y, La) transistors.

    PubMed

    Hennek, Jonathan W; Smith, Jeremy; Yan, Aiming; Kim, Myung-Gil; Zhao, Wei; Dravid, Vinayak P; Facchetti, Antonio; Marks, Tobin J

    2013-07-24

    In oxide semiconductors, such as those based on indium zinc oxide (IXZO), a strong oxygen binding metal ion ("oxygen getter"), X, functions to control O vacancies and enhance lattice formation, hence tune carrier concentration and transport properties. Here we systematically study, in the IXZO series, the role of X = Ga(3+) versus the progression X = Sc(3+) → Y(3+) → La(3+), having similar chemical characteristics but increasing ionic radii. IXZO films are prepared from solution over broad composition ranges for the first time via low-temperature combustion synthesis. The films are characterized via thermal analysis of the precursor solutions, grazing incidence angle X-ray diffraction (GIAXRD), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and scanning transmission electron microscopy (STEM) with high angle annular dark field (HAADF) imaging. Excellent thin-film transistor (TFT) performance is achieved for all X, with optimal compositions after 300 °C processing exhibiting electron mobilities of 5.4, 2.6, 2.4, and 1.8 cm(2) V(-1) s(-1) for Ga(3+), Sc(3+), Y(3+), and La(3+), respectively, and with I(on)/I(off) = 10(7)-10(8). Analysis of the IXZO TFT positive bias stress response shows X = Ga(3+) to be superior with mobilities (μ) retaining >95% of the prestress values and threshold voltage shifts (ΔV(T)) of <1.6 V, versus <85% μ retention and ΔV(T) ≈ 20 V for the other trivalent ions. Detailed microstructural analysis indicates that Ga(3+) most effectively promotes oxide lattice formation. We conclude that the metal oxide lattice formation enthalpy (ΔH(L)) and metal ionic radius are the best predictors of IXZO oxygen getter efficacy.

  1. Regenerable MgO promoted metal oxide oxygen carriers for chemical looping combustion

    DOEpatents

    Siriwardane, Ranjani V.; Miller, Duane D.

    2014-08-19

    The disclosure provides an oxygen carrier comprised of a plurality of metal oxide particles in contact with a plurality of MgO promoter particles. The MgO promoter particles increase the reaction rate and oxygen utilization of the metal oxide when contacting with a gaseous hydrocarbon at a temperature greater than about 725.degree. C. The promoted oxide solid is generally comprised of less than about 25 wt. % MgO, and may be prepared by physical mixing, incipient wetness impregnation, or other methods known in the art. The oxygen carrier exhibits a crystalline structure of the metal oxide and a crystalline structure of MgO under XRD crystallography, and retains these crystalline structures over subsequent redox cycles. In an embodiment, the metal oxide is Fe.sub.2O.sub.3, and the gaseous hydrocarbon is comprised of methane.

  2. Growth enhancement and gene expression of Arabidopsis thaliana irradiated with active oxygen species

    NASA Astrophysics Data System (ADS)

    Watanabe, Satoshi; Ono, Reoto; Hayashi, Nobuya; Shiratani, Masaharu; Tashiro, Kosuke; Kuhara, Satoru; Inoue, Asami; Yasuda, Kaori; Hagiwara, Hiroko

    2016-07-01

    The characteristics of plant growth enhancement effect and the mechanism of the enhancement induced by plasma irradiation are investigated using various active species in plasma. Active oxygen species in oxygen plasma are effective for growth enhancement of plants. DNA microarray analysis of Arabidopsis thaliana indicates that the genes coding proteins that counter oxidative stresses by eliminating active oxygen species are expressed at significantly high levels. The size of plant cells increases owing to oxygen plasma irradiation. The increases in gene expression levels and cell size suggest that the increase in the expression level of the expansin protein is essential for plant growth enhancement phenomena.

  3. Effect of pressure on the behavior of copper-, iron-, and nickel-based oxygen carriers for chemical-looping combustion

    SciTech Connect

    Francisco Garcia-Labiano; Juan Adanez; Luis F. de Diego; Pilar Gayan; Alberto Abad

    2006-02-01

    This work analyzes the main characteristics related to the chemical looping combustion (CLC) process necessary to use the syngas obtained in an integrated gasification combined cycle (IGCC) power plant. The kinetics of reduction with H{sub 2} and CO and oxidation with O{sub 2} of three high-reactivity oxygen carriers used in the CLC system have been determined in a thermogravimetric analyzer at atmospheric pressure. The iron- and nickel-based oxygen carriers were prepared by freeze-granulation, and the copper-based oxygen carrier was prepared by impregnation. The changing grain size model (CGSM) was used for the kinetic determination, assuming spherical grains for the freeze-granulated particles containing iron and nickel and a platelike geometry for the reacting surface of the copper-based impregnated particles. The dependence of the reaction rates on temperature was low, with the activation energy values varying from 14 to 33 kJ mol{sup -1} for the reduction and 7 to 15 kJ mol{sup -1} for the oxidation. The reaction order depended on the reacting gas and oxygen carrier, with values ranging from 0.25 to 1. However, an increase in the operating pressure for the IGCC + CLC system increases the thermal efficiency of the process, and the CO{sub 2} is recovered as a high pressure gas, decreasing the energy demand for further compression. The effect of pressure on the behavior of the oxygen carriers has been analyzed in a pressurized thermogravimetric analyzer at 1073 K and pressures up to 30 atm. It has been found that an increase in total pressure has a negative effect on the reaction rates of all the oxygen carriers. Moreover, the use of the CGSM with the kinetic parameters obtained at atmospheric pressure predicted higher reaction rates than those experimentally obtained at higher pressures, and therefore, the kinetic parameters necessary to design pressurized CLC plants must be determined at the operating pressure. 34 refs., 8 figs., 2 tabs.

  4. OXYGEN-ENRICHED COAL COMBUSTION WITH CARBON DIOXIDE RECYCLE AND RECOVERY: SIMULATION AND EXPERIMENTAL STUDY

    SciTech Connect

    John M. Veranth; Gautham Krishnamoorthy

    2002-01-01

    An accurate estimation of the CO/CO{sub 2} ratio at the surface of an ash inclusion in coal during combustion is necessary to predict the equilibrium partial pressure of volatile reduced metal species inside the burning particle and the rate of vaporization of metal oxides. Assumptions that have been made previously for the CO/CO{sub 2} ratio at the surface of mineral inclusions are compared to those obtained from a steady state detailed kinetics code for a single porous particle (SKIPPY). The detailed kinetic simulations from SKIPPY for varying particle sizes and bulk gas compositions were used to develop algebraic expressions for the CO/CO{sub 2} ratio that can be incorporated into metal vaporization sub-models run as a post processor to detailed furnace simulations.

  5. Combustion of solid fuel slabs with gaseous oxygen in a hybrid motor analog

    NASA Technical Reports Server (NTRS)

    Chiaverini, Martin J.; Harting, George C.; Lu, Yeu-Cherng; Kuo, Kenneth K.; Serin, Nadir; Johnson, David K.

    1995-01-01

    Using a high-pressure, two-dimensional hybrid motor, an experimental investigation was conducted on fundamental processes involved in hybrid rocket combustion. HTPB (Hydroxyl-terminated- Polybutadiene) fuel cross linked with diisocyanate was burned with GOX under various operating conditions. Large amplitude pressure oscillations were encountered in earlier test runs. After identifying the source of instability and decoupling the GOX feed line system and combustion chamber, the pressure oscillations were drastically reduced from +/- 20% of the localized mean pressure to an acceptable range of +/- 1.5%. Embedded fine-wire thermocouples indicated that the surface temperature of the burning fuel was around 1000 K depending upon axial locations and operating conditions. Also, except near the leading-edge region, the subsurface thermal wave profiles in the upstream locations arc thicker than those in the downstream locations since the solid-fuel regression rate, in general, increases with distance along the fuel slab. The recovered solid fuel slabs in the laminar portion of the boundary layer exhibited smooth surfaces, indicating the existence of a liquid melt layer on the burning fuel surface in the upstream region. After the transition section, which displayed distinct transverse striations, the surface roughness pattern became quite random and very pronounced in the downstream turbulent boundary-layer region. Both real time X-ray radiography and ultrasonic pulse-echo techniques were used to determine the instantaneous web thicknesses and instantaneous solid-fuel regression rates over certain portions of the fuel slabs. Globally averaged and axially dependent but time-averaged regression rates were also obtained and presented. Several tests were conducted using, simultaneously, one translucent fuel slab and one fuel slab processed with carbon black powder. The addition of carbon black did not affect the measured regression rates or surface temperatures in comparison

  6. Oxygen assisted laser cutting mechanism—a laminar boundary layer approach including the combustion process

    NASA Astrophysics Data System (ADS)

    Yilbaş, B. S.; Sahin, A. Z.

    1995-06-01

    The present study examines the combined effects of chemical reactions taking place between a gas jet and molten metal, the cooling effect of the jet and the evaporation of metal, during a CO 2 laser cutting process. A laminar boundary layer approach was used to develop a theoretical model for the oxygen gas jet laser cutting mechanism. An experiment was carried out to monitor the keyhole formation using a video recorder and detect the light emitted from the entrance and exist surfaces of the workpiece using a fibre-optic probe during the cutting process. The experimental study was extended to employ two different workpiece materials (stainless steel and mild steel) at two thicknesses, and varying oxygen assisting gas pressures. It is found that the theoretical model developed in the present study is valid for a cutting speed of about 30 mm s -1 and all jet velocities up to sonic, since the effect of shock is excluded in the model.

  7. Reduction kinetics of iron-based oxygen carriers using methane for chemical-looping combustion

    NASA Astrophysics Data System (ADS)

    Luo, Ming; Wang, Shuzhong; Wang, Longfei; Lv, Mingming

    2014-12-01

    The performance of three iron-based oxygen carriers (pure Fe2O3, synthetic Fe2O3/MgAl2O4 and iron ore) in reduction process using methane as fuel is investigated in thermo-gravimetric analyzer (TGA). The reaction rate and mechanism between three oxygen carriers and methane are investigated. On the basis of reactivity in reduction process, it may be concluded that Fe2O3/MgAl2O4 has the best reactivity with methane. The reaction rate constant is found to be in the following order: Fe2O3/MgAl2O4 > pure Fe2O3 > iron ore and the activation energy varies between 49 and 184 kJ mol-1. Reduction reactions for the pure Fe2O3 and synthetic Fe2O3/MgAl2O4 are well represented by the reaction controlling mechanism, and for the iron ore the phase-boundary controlled (contracting cylinder) model dominates. The particles of iron ore and synthetic Fe2O3/MgAl2O4 have better stability than that of pure Fe2O3 when the reaction temperature is limited to lower than 1223 K. These preliminary results suggest that iron-based mixed oxygen carrier particles are potential to be used in methane chemical looping process, but the reactivity of the iron ore needs to be increased.

  8. Deciphering mechanisms of enhanced-retarded oxygen diffusion in doped Si

    NASA Astrophysics Data System (ADS)

    Timerkaeva, Dilyara; Caliste, Damien; Pochet, Pascal

    2013-12-01

    We study enhanced/retarded diffusion of oxygen in doped silicon by means of first principle calculations. We evidence that the migration energy of oxygen dimers cannot be significantly affected by strain, doping type, or concentration. We attribute the enhanced oxygen diffusion in p-doped silicon to reduced monomer migration energy and the retarded oxygen diffusion in Sb-doped to monomer trapping close to a dopant site. These two mechanisms can appear simultaneously for a given dopant leading to contradictory experimental results. More generally, our findings cast a new light on phenomena involving oxygen diffusion: precipitation, thermal donors formation, and light induced degradation.

  9. Variation of antioxidative activity and growth enhancement of Brassicaceae induced by low-pressure oxygen plasma

    NASA Astrophysics Data System (ADS)

    Ono, Reoto; Hayashi, Nobuya

    2015-06-01

    The mechanism of growth enhancement induced by active oxygen species generated in an oxygen plasma is investigated. The plant growth enhancement induced by the active oxygen species would relate to an antioxidative activity, which is one of the biological responses. The amount of generated active oxygen species is varied by the oxygen gas pressure in a low-pressure RF glow discharge plasma. The antioxidative activity of sprouts of Brassicaceae induced by the oxygen plasma is maximized at pressures between 30 and 40 Pa, whereas the antioxidative activity becomes small at around 60 and 80 Pa. The pressure dependence of the antioxidative activity of sprout stems is opposite to that of the stem length of the sprouts. The growth enhancement would be induced by the increase in the concentration of active oxygen species in plants owing to the decrease in the amount of antioxidative substances.

  10. Storm time impulsive enhancements of energetic oxygen due to adiabatic acceleration of preexisting warm oxygen in the inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Keika, Kunihiro; Seki, Kanako; Nosé, Masahito; Machida, Shinobu; Miyoshi, Yoshizumi; Lanzerotti, Louis J.; Mitchell, Donald G.; Gkioulidou, Matina; Turner, Drew; Spence, Harlan; Larsen, Brian A.

    2016-08-01

    We examine enhancements of energetic (>50 keV) oxygen ions observed by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on board the Van Allen Probes spacecraft in the inner magnetosphere (L ~ 6) at 22-23 h magnetic local time (MLT) during an injection event of the 6 June 2013 storm. Simultaneous observations by two Van Allen Probes spacecraft located close together (~0.5 RE) indicate that particle injections occurred in the premidnight sector (< ~24 h MLT). We also examine the evolution of the proton and oxygen energy spectra at L ~ 6 during the injection event. The spectral slope did not significantly change during the storm. The oxygen phase space density (PSD) was shifted toward higher PSD in a wide range of the first adiabatic invariant. The spectral evolution manifests the characteristics of adiabatic acceleration and density increase of oxygen ions. Warm (0.1-10 keV) oxygen measured by the Helium, Oxygen, Proton, and Electron (HOPE) instrument was enhanced prior to the storm mostly in magnetic field-aligned directions. The most reasonable scenario of this event is that warm oxygen ions that preexisted in the inner magnetosphere were picked up and adiabatically transported and accelerated by spatially localized, temporarily impulsive electric fields.

  11. New diagnostic methods for laser plasma- and microwave-enhanced combustion

    PubMed Central

    Miles, Richard B; Michael, James B; Limbach, Christopher M; McGuire, Sean D; Chng, Tat Loon; Edwards, Matthew R; DeLuca, Nicholas J; Shneider, Mikhail N; Dogariu, Arthur

    2015-01-01

    The study of pulsed laser- and microwave-induced plasma interactions with atmospheric and higher pressure combusting gases requires rapid diagnostic methods that are capable of determining the mechanisms by which these interactions are taking place. New rapid diagnostics are presented here extending the capabilities of Rayleigh and Thomson scattering and resonance-enhanced multi-photon ionization (REMPI) detection and introducing femtosecond laser-induced velocity and temperature profile imaging. Spectrally filtered Rayleigh scattering provides a method for the planar imaging of temperature fields for constant pressure interactions and line imaging of velocity, temperature and density profiles. Depolarization of Rayleigh scattering provides a measure of the dissociation fraction, and multi-wavelength line imaging enables the separation of Thomson scattering from Rayleigh scattering. Radar REMPI takes advantage of high-frequency microwave scattering from the region of laser-selected species ionization to extend REMPI to atmospheric pressures and implement it as a stand-off detection method for atomic and molecular species in combusting environments. Femtosecond laser electronic excitation tagging (FLEET) generates highly excited molecular species and dissociation through the focal zone of the laser. The prompt fluorescence from excited molecular species yields temperature profiles, and the delayed fluorescence from recombining atomic fragments yields velocity profiles. PMID:26170432

  12. Hydration of spent limestone and dolomite to enhance sulfation in fluidized-bed combustion

    SciTech Connect

    Shearer, J.A.; Smith, G.W.; Moulton, D.S.; Turner, C.B.; Myles, K.M.; Johnson, I.

    1980-01-01

    The utilization of CaO in fluidized bed combustion can be markedly increased to reduce the cost and environmental impact of quarrying and disposing of large quantities of solid waste. A new method of treatment of spent bed material to reactivate its SO/sub 2/ capturing ability has been found. Partially sulfated spent overflow material from a fluidized-bed combustor is treated with water and then reintroduced to the combustor as renewed feed that further reacts with SO/sub 2/. This material has sufficient physical integrity, due to the outer layer of CaSO/sub 4/, and high reactivity to make it suitable as a sorbent feedstock. The work reported here details observations on a number of limestones and dolomites reacted in laboratory furnaces under simulated combustion conditions as well as verification of the effectiveness of the method in a 15-cm-ID process development unit scale atmospheric fluidized-bed coal combustor. Initial kinetic studies have also been made on the hydration reaction of partially sulfated limestone. A proposed mechanism of interaction is discussed to explain the enhanced reactivity. Changes in total porosity and pore size distribution in the partially sulfated material due to Ca(OH)/sub 2/ formation and its dehydration serve to open up the particle interior and its residual CaO to further reaction with SO/sub 2/. Almost complete utilization of the available CaO can be achieved by successive applications of this promising new technique.

  13. A laboratory model of a hydrogen/oxygen engine for combustion and nozzle studies

    NASA Astrophysics Data System (ADS)

    Morren, Sybil H.; Myers, Roger M.; Benko, Stephen E.; Arrington, Lynn A.; Reed, Brian D.

    1993-06-01

    A small laboratory diagnostic thruster was developed in order to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flowfields. Tests were performed at chamber pressures of about 255 kPa, 370 kPa, and 500 kPa with oxidizer/fuel mixture ratios between 4.0 and 8.0. Two gaseous hydrogen/gaseous oxygen injector designs were tested with 60 and 75 fuel film cooling. The results of hot-wire tests showed the thruster and instrumentation designs to be effective. Azimuthal temperature distributions were found to be a function of operating conditions and hardware configuration. Results indicated that small differences in injector design can result in dramatically different thruster performance and wall temperature behavior. However, the importance of these injector effects may be decreased by operating at a high fuel film cooling rate.

  14. A laboratory model of a hydrogen/oxygen engine for combustion and nozzle studies

    NASA Technical Reports Server (NTRS)

    Morren, Sybil H.; Myers, Roger M.; Benko, Stephen E.; Arrington, Lynn A.; Reed, Brian D.

    1993-01-01

    A small laboratory diagnostic thruster was developed in order to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flowfields. Tests were performed at chamber pressures of about 255 kPa, 370 kPa, and 500 kPa with oxidizer/fuel mixture ratios between 4.0 and 8.0. Two gaseous hydrogen/gaseous oxygen injector designs were tested with 60 and 75 fuel film cooling. The results of hot-wire tests showed the thruster and instrumentation designs to be effective. Azimuthal temperature distributions were found to be a function of operating conditions and hardware configuration. Results indicated that small differences in injector design can result in dramatically different thruster performance and wall temperature behavior. However, the importance of these injector effects may be decreased by operating at a high fuel film cooling rate.

  15. Dramatically enhanced oxygen uptake and ionization yield of positive secondary ions with C60+ sputtering.

    PubMed

    Liao, Hua-Yang; Tsai, Meng-Hung; You, Yun-Wen; Chang, Hsun-Yun; Huang, Chih-Chieh; Shyue, Jing-Jong

    2012-04-03

    To explore C(60)(+) sputtering beyond low-damage depth profiling of organic materials, X-ray photoelectron spectrometry (XPS) and secondary ion mass spectrometry (SIMS) were used to examine metallic surfaces during and after C(60)(+) sputtering. During C(60)(+) sputtering, XPS spectra indicated that the degrees of carbon deposition were different for different metallic surfaces. Moreover, for some metals (e.g., Al, W, Ta, Ti, and Mo), the intensity of the O 1s photoelectron increased significantly during C(60)(+) sputtering, even though the instrument was under ultrahigh vacuum (<5 × 10(-7) Pa). This result indicated that the rate of oxygen uptake was greater than the rate of C(60)(+) sputtering. This behavior was not observed with the commonly used Ar(+) sputtering. To measure the oxygen uptake kinetics, pure oxygen was leaked into the chamber to maintain a 5 × 10(-6) Pa oxygen environment. The C(60)(+)-sputtered surface had a clearly increased rate of oxygen uptake than the Ar(+)-sputtered surface, even for moderately reactive metals such as Fe and Ni. For relatively nonreactive metals such as Cu and Au, a small amount of carbon was implanted and no oxygen uptake was observed. High-resolution XPS spectra revealed the formation of metal carbides on these reactive metals, and the carbon deposition and enhanced uptake of oxygen correlated to the carbide formation. Because oxygen enhances the secondary ion yield through surface passivation, the enhanced oxygen uptake due to C(60)(+) sputtering could be beneficial for SIMS analysis. To examine this hypothesis, C(60)(+) and Ar(+) were used as primary ions, and it was found that the intensity enhancement (because of the oxygen flooding at 5 × 10(-6) Pa) was much higher with C(60)(+) than with Ar(+). Therefore, oxygen flooding during C(60)(+) sputtering has a great potential for enhancing the detection limit due to the enhanced oxygen uptake.

  16. A laboratory model of a hydrogen/oxygen engine for combustion and nozzle studies

    NASA Astrophysics Data System (ADS)

    Morren, Sybil Huang; Myers, Roger M.; Benko, Stephen E.; Arrington, Lynn A.; Reed, Brian D.

    1993-06-01

    A small laboratory diagnostic thruster was developed to augment present low thrust chemical rocket optical and heat flux diagnostics at the NASA Lewis Research Center. The objective of this work was to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flow fields. The nominal engine thrust was 110 N. Tests were performed at chamber pressures of about 255 kPa, 370 kPa, and 500 kPa with oxidizer to fuel mixture ratios between 4.0 and 8.0. Two gaseous hydrogen/gaseous oxygen injector designs were tested with 60 percent and 75 percent fuel film cooling. The thruster and instrumentation designs were proven to be effective via hot fire testing. The thruster diagnostics provided inner wall temperature and static pressure measurements which were compared to the thruster global performance data. For several operating conditions, the performance data exhibited unexpected trends which were correlated with changes in the axial wall temperature distribution. Azimuthal temperature distributions were found to be a function of operating conditions and hardware configuration. The static pressure profiles showed that no severe pressure gradients were present in the rocket. The results indicated that small differences in injector design can result in dramatically different thruster performance and wall temperature behavior, but that these injector effects may be overshadowed by operating at a high fuel film cooling rate.

  17. A Laboratory Model of a Hydrogen/Oxygen Engine for Combustion and Nozzle Studies

    NASA Technical Reports Server (NTRS)

    Morren, Sybil Huang; Myers, Roger M.; Benko, Stephen E.; Arrington, Lynn A.; Reed, Brian D.

    1993-01-01

    A small laboratory diagnostic thruster was developed to augment present low thrust chemical rocket optical and heat flux diagnostics at the NASA Lewis Research Center. The objective of this work was to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flow fields. The nominal engine thrust was 110 N. Tests were performed at chamber pressures of about 255 kPa, 370 kPa, and 500 kPa with oxidizer to fuel mixture ratios between 4.0 and 8.0. Two gaseous hydrogen/gaseous oxygen injector designs were tested with 60 percent and 75 percent fuel film cooling. The thruster and instrumentation designs were proven to be effective via hot fire testing. The thruster diagnostics provided inner wall temperature and static pressure measurements which were compared to the thruster global performance data. For several operating conditions, the performance data exhibited unexpected trends which were correlated with changes in the axial wall temperature distribution. Azimuthal temperature distributions were found to be a function of operating conditions and hardware configuration. The static pressure profiles showed that no severe pressure gradients were present in the rocket. The results indicated that small differences in injector design can result in dramatically different thruster performance and wall temperature behavior, but that these injector effects may be overshadowed by operating at a high fuel film cooling rate.

  18. The upper airway response to pollen is enhanced by exposure to combustion particulates: a pilot human experimental challenge study.

    PubMed

    Hauser, Russ; Rice, Timothy M; Krishna Murthy, G G; Wand, Matt P; Lewis, Daniel; Bledsoe, Toni; Paulauskis, Joseph

    2003-04-01

    Although human experimental studies have shown that gaseous pollutants enhance the inflammatory response to allergens, human data on whether combustion particulates enhance the inflammatory response to allergen are limited. Therefore, we conducted a human experimental study to investigate whether combustion particulates enhance the inflammatory response to aeroallergens. "Enhancement" refers to a greater-than-additive response when combustion particulates are delivered with allergen, compared with the responses when particulates and allergen are delivered alone. Eight subjects, five atopic and three nonatopic, participated in three randomized exposure-challenge sessions at least 2 weeks apart (i.e., clean air followed by allergen, particles followed by no allergen, or particles followed by allergen). Each session consisted of nasal exposure to combustion particles (target concentration of 1.0 mg/m3) or clean air for 1 hr, followed 3 hr later by challenge with whole pollen grains or placebo. Nasal lavage was performed immediately before particle or clean air exposure, immediately after exposure, and 4, 18 and 42 hr after pollen challenge. Cell counts, differentials, and measurement of cytokines were performed on each nasal lavage. In atopic but not in nonatopic subjects, when allergen was preceded by particulates, there was a significant enhancement immediately after pollen challenge in nasal lavage leukocytes and neutrophils (29.7 X 10(3) cells/mL and 25.4 X 10(3) cells/mL, respectively). This represents a 143% and 130% enhancement, respectively. The enhanced response for interleukin-4 was 3.23 pg/mL (p = 0.06), a 395% enhancement. In atopic subjects there was evidence of an enhanced response when particulates, as compared to clean air, preceded the allergen challenge.

  19. Thermofluid analysis of the SSME preburner using a gas-gas diffusion model for oxygen and hydrogen combustion at supercritical pressures

    NASA Technical Reports Server (NTRS)

    Prakash, C.; Singhal, A. K.; Shafer, C.

    1986-01-01

    The paper discusses the thermofluid analysis of the Space Shuttle Main Engine (SSME) fuelside preburner. The governing equations have been solved numerically to predict flow, heat transfer, mixing, and combustion. A two-fluid approach is adopted in which oxygen is regarded as one fluid and hydrogen is regarded as the other fluid. The chemical kinetics is assumed to be very fast so that combustion is primarily controlled by the rate of mixing between oxygen and hydrogen. The preburner pressure is much greater than the critical pressures of oxygen and hydrogen; hence, a gas-gas diffusion model (rather than an evaporation model) has been developed to compute the rate of interphase mixing. Empirical correlations have been incorporated to account for the effect of slip on the interphase exchange. A sensitivity study has been performed with various model parameters. It is observed that the model can predict possibility of incomplete combustion and local regions of high temperatures under steady operating conditions. Some of these anomalies have been observed in actual tests, and the numerical model is useful for understanding possible causes and remedies. At least some measurements are needed for quantitative verification of the model.

  20. Reclaimed wastewater quality enhancement by oxygen injection during transportation.

    PubMed

    Rodríguez-Gómez, L E; Alvarez, M; Rodríguez-Sevilla, J; Marrero, M C; Hernández, A

    2011-01-01

    In-sewer treatments have been studied in sewer systems, but few have been carried out on reclaimed wastewater systems. A study of oxygen injection has been performed in a completely filled gravity pipe, 0.6 m in diameter and 62 km long, in cast iron with concrete inside coating, which is part of the reclaimed wastewater reuse scheme of Tenerife (Spain). A high pressure oxygen injection system was installed at 16.0 km from pipe inlet and a constant dosage of 30 mg/L O(2) has been injected during six months, under three different operational modes (low COD, 63 mg/L; high COD, 91 mg/L; and partially nitrified water). Oxygen has been consumed in nitrification and organic matter reduction. Generally, nitrification is clearly favored instead of the organic matter oxidation. Nitrification occurs, in general, with nitrite accumulation due to the presence of free ammonia above 1 mg/L. Denitrification is in all cases incomplete due to a limitation of easily biodegradable organic matter content, inhibiting the appearance of anaerobic conditions and sulfide generation. A notable reduction of organic matter parameters is achieved (TSS below 10 mg/L), which is significantly higher than that observed under the ordinary transport conditions without oxygen. This leads to a final cost reduction, and the oxygen injection system helps water reuse managers to maintain a final good water quality in the case of a treatment plant malfunction.

  1. Enhanced diffusion of oxygen depending on Fermi level position in heavily boron-doped silicon

    SciTech Connect

    Torigoe, Kazuhisa Fujise, Jun; Ono, Toshiaki; Nakamura, Kozo

    2014-11-21

    The enhanced diffusivity of oxygen in heavily boron doped silicon was obtained by analyzing oxygen out-diffusion profile changes found at the interface between a lightly boron-doped silicon epitaxial layer and a heavily boron-doped silicon substrate by secondary ion mass spectrometry. It was found that the diffusivity is proportional to the square root of boron concentration in the range of 10{sup 18 }cm{sup −3}–10{sup 19 }cm{sup −3} at temperatures from 750 °C to 950 °C. The model based on the diffusion of oxygen dimers in double positive charge state could explain the enhanced diffusion. We have concluded that oxygen diffusion enhanced in heavily boron-doped silicon is attributed to oxygen dimers ionized depending on Fermi level position.

  2. Enhancement of Electrical Conductivity of LiFePO4 by Controlled Solution Combustion Synthesis

    NASA Astrophysics Data System (ADS)

    Rajoba, S. J.; Jadhav, L. D.; Patil, P. S.; Tyagi, D. K.; Varma, S.; Wani, B. N.

    2016-12-01

    LiFePO4 has been synthesized by a solution combustion method at different oxidant-to-fuel ratios. At stoichiometric oxidant-to-fuel ratio (1:2), Fe2O3 formed in addition to LiFePO4 during combustion. Hence, reducing atmosphere was generated by increasing the ratio from stoichiometric to 1:4 and 1:8, named as 1-LFP, 2-LFP, and 4-LFP, respectively. Furthermore, as-prepared powders were calcined in inert atmosphere to avoid oxidation of LiFePO4 to Fe2O3 and Li3PO4, as confirmed by x-ray diffraction (XRD) and thermogravimetric and differential thermal analyses. The calcined powders were characterized by XRD analysis, Raman spectroscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. X-ray photoelectron spectroscopy ascertained oxidation state of +2 and +5 for Fe and P, respectively. With increasing oxidant-to-fuel ratio, the binding energies of 2p 3/2 and 2p 1/2 levels of Fe shifted downwards and showed increased splitting. According to Raman spectroscopy results, the residual carbon is amorphous with sp 2 C-C bond. The conductivity of 1-LFP, 2-LFP, and 4-LFP measured at 313 K was 0.15 × 10-6 S/cm, 8.46 × 10-6 S/cm, and 1.21 × 10-3 S/cm, respectively. The enhanced conductivity of 4-LFP is due to presence of residual carbon and Fe2P.

  3. Enhancement of Electrical Conductivity of LiFePO4 by Controlled Solution Combustion Synthesis

    NASA Astrophysics Data System (ADS)

    Rajoba, S. J.; Jadhav, L. D.; Patil, P. S.; Tyagi, D. K.; Varma, S.; Wani, B. N.

    2017-03-01

    LiFePO4 has been synthesized by a solution combustion method at different oxidant-to-fuel ratios. At stoichiometric oxidant-to-fuel ratio (1:2), Fe2O3 formed in addition to LiFePO4 during combustion. Hence, reducing atmosphere was generated by increasing the ratio from stoichiometric to 1:4 and 1:8, named as 1-LFP, 2-LFP, and 4-LFP, respectively. Furthermore, as-prepared powders were calcined in inert atmosphere to avoid oxidation of LiFePO4 to Fe2O3 and Li3PO4, as confirmed by x-ray diffraction (XRD) and thermogravimetric and differential thermal analyses. The calcined powders were characterized by XRD analysis, Raman spectroscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. X-ray photoelectron spectroscopy ascertained oxidation state of +2 and +5 for Fe and P, respectively. With increasing oxidant-to-fuel ratio, the binding energies of 2 p 3/2 and 2 p 1/2 levels of Fe shifted downwards and showed increased splitting. According to Raman spectroscopy results, the residual carbon is amorphous with sp 2 C-C bond. The conductivity of 1-LFP, 2-LFP, and 4-LFP measured at 313 K was 0.15 × 10-6 S/cm, 8.46 × 10-6 S/cm, and 1.21 × 10-3 S/cm, respectively. The enhanced conductivity of 4-LFP is due to presence of residual carbon and Fe2P.

  4. Reducible Supports for Ni-based Oxygen Carriers in Chemical Looping Combustion

    SciTech Connect

    Bhavsar, Saurabh; Veser, Goetz

    2013-04-01

    Nuclear spin relaxation, small-angle X-ray scattering (SAXS), and electrospray ionization mass spectrometry (ESI-MS) techniques are used to determine supramolecular arrangement of 3-methyl-1-octyl-4-phenyl-1H-triazol-1,2,3-ium bis(trifluoromethanesulfonyl)imide [OMPhTz][Tf{sub 2}N], an example of a triazolium-based ionic liquid. The results obtained showed first-order thermodynamic dependence for nuclear spin relaxation of the anion. First-order relaxation dependence is interpreted as through-bond dipolar relaxation. Greater than first-order dependence was found in the aliphatic protons, aromatic carbons (including nearest neighbors), and carbons at the end of the aliphatic tail. Greater than first order thermodynamic dependence of spin relaxation rates is interpreted as relaxation resulting from at least one mechanism additional to through-bond dipolar relaxation. In rigid portions of the cation, an additional spin relaxation mechanism is attributed to anisotropic effects, while greater than first order thermodynamic dependence of the octyl side chain’s spin relaxation rates is attributed to cation–cation interactions. Little interaction between the anion and the cation was observed by spin relaxation studies or by ESI-MS. No extended supramolecular structure was observed in this study, which was further supported by MS and SAXS. nuclear Overhauser enhancement (NOE) factors are used in conjunction with spin–lattice relaxation time (T{sub 1}) measurements to calculate rotational correlation times for C–H bonds (the time it takes for the vector represented by the bond between the two atoms to rotate by one radian). The rotational correlation times are used to represent segmental reorientation dynamics of the cation. A combination of techniques is used to determine the segmental interactions and dynamics of this example of a triazolium-based ionic liquid.

  5. Vacancy–Vacancy Interaction Induced Oxygen Diffusivity Enhancement in Undoped Nonstoichiometric Ceria

    SciTech Connect

    Yuan, Fenglin; Zhang, Yanwen; Weber, William J.

    2015-05-19

    In this paper, molecular dynamics simulations and molecular static calculations have been used to systematically study oxygen vacancy transport in undoped nonstoichiometric ceria. A strong oxygen diffusivity enhancement appears in the vacancy concentration range of 2–4% over the temperature range from 1000 to 2000 K. An Arrhenius ion diffusion mechanism by vacancy hopping along the (100) direction is unambiguously identified, and an increasing trend of both the oxygen migration barrier and the prefactor with increasing vacancy concentration is observed. Within the framework of classical diffusion theory, a weak concentration dependence of the prefactor in oxygen vacancy migration is shown to be crucial for explaining the unusual fast oxygen ion migration in the low concentration range and consequently the appearance of a maximum in oxygen diffusivity. Finally, a representative (100) direction interaction model is constructed to identify long-range vacancy–vacancy interaction as the structural origin of the positive correlation between oxygen migration barrier and vacancy concentration.

  6. Organic radicals for the enhancement of oxygen reduction reaction in Li-O2 batteries.

    PubMed

    Tesio, A Y; Blasi, D; Olivares-Marín, M; Ratera, I; Tonti, D; Veciana, J

    2015-12-25

    We examine for the first time the ability of inert carbon free-radicals as soluble redox mediators to catalyze and enhance the oxygen reduction reaction in a (TEGDME)-based electrolyte. We demonstrate that the tris(2,4,6-trichlorophenyl)methyl (TTM) radical is capable of chemically favoring the oxygen reduction reaction improving significantly the Li-O2 battery performance.

  7. Enhanced Singlet Oxygen Generation in Oxidized Graphitic Carbon Nitride for Organic Synthesis.

    PubMed

    Wang, Hui; Jiang, Shenlong; Chen, Shichuan; Li, Dandan; Zhang, Xiaodong; Shao, Wei; Sun, Xianshun; Xie, Junfeng; Zhao, Zhi; Zhang, Qun; Tian, Yupeng; Xie, Yi

    2016-08-01

    Experimental data reveal that the incorporation of carbonyl groups into polymer matrix can significantly enhance singlet oxygen ((1) O2 ) generation and suppress production of other reactive oxygen species. Excitonic processes investigated by phosphorescence spectroscopy reveal enhanced triplet-exciton generation in the modified g-C3 N4 , which facilitate (1) O2 generation through an energy transfer process. Benefiting from this, the modified g-C3 N4 shows excellent conversion and selectivity in organic synthesis.

  8. The Effect of Varying Magnetic Field Gradient on Combustion Dynamic

    NASA Astrophysics Data System (ADS)

    Suzdalenko, Vera; Zake, Maija; Barmina, Inesa; Gedrovics, Martins

    2011-01-01

    The focus of the recent experimental research is to provide control of the combustion dynamics and complex measurements (flame temperature, heat production rate, and composition of polluting emissions) for pelletized wood biomass using a non-uniform magnetic field that produces magnetic force interacting with magnetic moment of paramagnetic oxygen. The experimental results have shown that a gradient magnetic field provides enhanced mixing of the flame compounds by increasing combustion efficiency and enhancing the burnout of volatiles.

  9. Erythropoiesis-stimulating agents and other methods to enhance oxygen transport

    PubMed Central

    Elliott, S

    2008-01-01

    Oxygen is essential for life, and the body has developed an exquisite method to collect oxygen in the lungs and transport it to the tissues. Hb contained within red blood cells (RBCs), is the key oxygen-carrying component in blood, and levels of RBCs are tightly controlled according to demand for oxygen. The availability of oxygen plays a critical role in athletic performance, and agents that enhance oxygen delivery to tissues increase aerobic power. Early methods to increase oxygen delivery included training at altitude, and later, transfusion of packed RBCs. A breakthrough in understanding how RBC formation is controlled included the discovery of erythropoietin (Epo) and cloning of the EPO gene. Cloning of the EPO gene was followed by commercial development of recombinant human Epo (rHuEpo). Legitimate use of this and other agents that affect oxygen delivery is important in the treatment of anaemia (low Hb levels) in patients with chronic kidney disease or in cancer patients with chemotherapy-induced anaemia. However, competitive sports was affected by illicit use of rHuEpo to enhance performance. Testing methods for these agents resulted in a cat-and-mouse game, with testing labs attempting to detect the use of a drug or blood product to improve athletic performance (doping) and certain athletes developing methods to use the agents without being detected. This article examines the current methods to enhance aerobic performance and the methods to detect illicit use. PMID:18362898

  10. The enhancement of the mixing and combustion processes in supersonic flow applied to scramjet engine

    SciTech Connect

    Kopchenov, V.I.; Lomkov, K.E. )

    1992-07-01

    The Reynolds averaged parabolized Navier-Stokes equations are employed for the numerical study of turbulent mixing and combustion of a supersonic hydrogen jet in a supersonic airflow. A one-equation differential turbulence model is utilized. The simplified flame sheet model is employed for the numerical simulation of the supersonic combustion. 24 refs.

  11. Ignition delays, heats of combustion, and reaction rates of aluminum alkyl derivatives used as ignition and combustion enhancers for supersonic combustion

    NASA Technical Reports Server (NTRS)

    Ryan, Thomas W., III; Schwab, S. T.; Harlowe, W. W.

    1992-01-01

    The subject of this paper is the design of supersonic combustors which will be required in order to achieve the needed reaction rates in a reasonable sized combustor. A fuel additive approach, which is the focus of this research, is the use of pyrophorics to shorten the ignition delay time and to increase the energy density of the fuel. Pyrophoric organometallic compounds may also provide an ignition source and flame stabilization mechanism within the combustor, thus permitting use of hydrocarbon fuels in supersonic combustion systems. Triethylaluminum (TEA) and trimethylaluminum (TMA) were suggested for this application due to their high energy density and reactivity. The objective here is to provide comparative data for the ignition quality, the energy content, and the reaction rates of several different adducts of both TEA and TMA. The results of the experiments indicate the aluminum alkyls and their more stable derivatives reduce the ignition delay and total reaction time to JP-10 jet fuel. Furthermore, the temperature dependence of ignition delay and total reaction time of the blends of the adducts are significantly lower than in neat JP-10.

  12. Long term analysis of the biomass content in the feed of a waste-to-energy plant with oxygen-enriched combustion air.

    PubMed

    Fellner, Johann; Cencic, Oliver; Zellinger, Günter; Rechberger, Helmut

    2011-10-01

    Thermal utilization of municipal solid waste and commercial wastes has become of increasing importance in European waste management. As waste materials are generally composed of fossil and biogenic materials, a part of the energy generated can be considered as renewable and is thus subsidized in some European countries. Analogously, CO(2) emissions of waste incinerators are only partly accounted for in greenhouse gas inventories. A novel approach for determining these fractions is the so-called balance method. In the present study, the implementation of the balance method on a waste-to-energy plant using oxygen-enriched combustion air was investigated. The findings of the 4-year application indicate on the one hand the general applicability and robustness of the method, and on the other hand the importance of reliable monitoring data. In particular, measured volume flows of the flue gas and the oxygen-enriched combustion air as well as corresponding O(2) and CO(2) contents should regularly be validated. The fraction of renewable (biogenic) energy generated throughout the investigated period amounted to between 27 and 66% for weekly averages, thereby denoting the variation in waste composition over time. The average emission factor of the plant was approximately 45 g CO(2) MJ(-1) energy input or 450 g CO(2) kg(-1) waste incinerated. The maximum error of the final result was about 16% (relative error), which was well above the error (<8%) of the balance method for plants with conventional oxygen supply.

  13. Peroxide-based oxygen generating topical wound dressing for enhancing healing of dermal wounds.

    PubMed

    Chandra, Prafulla K; Ross, Christina L; Smith, Leona C; Jeong, Seon S; Kim, Jaehyun; Yoo, James J; Harrison, Benjamin S

    2015-01-01

    Oxygen generating biomaterials represent a new trend in regenerative medicine that aims to generate and supply oxygen at the site of requirement, to support tissue healing and regeneration. To enhance the healing of dermal wounds, we have developed a highly portable, in situ oxygen generating wound dressings that uses sodium percarbonate (SPO) and calcium peroxide (CPO) as chemical oxygen sources. The dressing continuously generated oxygen for more than 3 days, after which it was replaced. In the in vivo testing on porcine full-thickness porcine wound model, the SPO/CPO dressing showed enhanced wound healing during the 8 week study period. Quantitative measurements of wound healing related parameters, such as wound closure, reepithelialization, epidermal thickness and collagen content of dermis showed that supplying oxygen topically using the SPO/CPO dressing significantly accelerated the wound healing. An increase in neovascularization, as determined using Von Willebrand factor (vWF) and CD31 staining, was also observed in the presence of SPO/CPO dressing. This novel design for a wound dressing that contains oxygen generating biomaterials (SPO/CPO) for supplying topical oxygen, may find utility in treating various types of acute to chronic wounds.

  14. Oxygen enhancement induced by ionic implantation in scandium diphthalocyanine thin films

    NASA Astrophysics Data System (ADS)

    Robinet, S.; Gauneau, M.; Salvi, M.; Clarisse, C.; Chaplain, R.

    1990-07-01

    Secondary ion mass spectrometry correlated with ionic implantations has allowed us to determine oxygen bulk concentration in scandium diphthalocyanine thin films. This concentration, around 2×1020 atom cm-3, increases by a factor 20-25 in implanted areas. This oxygen enhancement is observed for oxygen implantation but as well for xenon, caesium, or iodine implantation, and therefore is not dependent on the nature of the implanted atoms. The oxygen concentration saturates in the damaged region but its quantity depends on the energy loss and on the fluence; the larger the damaged layer, the larger the region where the enhancment takes place. The phenomenon will be tentatively related to the creation of free radicals induced by bond breaking occurring during the implantation process.But, other explanations including more severe degradations of the molecular material cannot be dismissed.

  15. ENHANCED FORMATION OF DIOXINS AND FURANS FROM COMBUSTION DEVICES BY ADDITION OF TRACE QUANTITIES OF BROMINE

    EPA Science Inventory

    Past pilot-scale experimental studies have shown a dramatic increase in the formation of certain chlorinated products of incomplete combustion (PICs) caused by the addition of trace amounts of bromine (Br). Emissions of trichloroethylene and tetrachloorethylene, generated as PICs...

  16. Comparative investigation on chemical looping combustion of coal-derived synthesis gas containing H2S over supported NiO oxygen carriers

    SciTech Connect

    Ksepko, E.; Siriwardane, R.; Tian, H.; Simonyi, T.; Sciazko, M.

    2010-01-01

    Chemical looping combustion (CLC) of simulated coal-derived synthesis gas was conducted with NiO oxygen carriers supported on SiO2, ZrO2, TiO2, and sepiolite. The effect of H2S on the performance of these samples for the CLC process was also evaluated. Five-cycle thermogravimetric analysis (TGA) tests at 800 C indicated that all oxygen carriers had a stable performance at 800 C, except NiO/SiO2. Full reduction/oxidation reactions of the oxygen carrier were obtained during the five-cycle test. It was found that support had a significant effect on reaction performance of NiO both in reduction and oxidation rates. The reduction reaction was significantly faster than the oxidation reaction for all oxygen carriers, while the oxidation reaction is fairly slow due to oxygen diffusion on NiO layers. The reaction profile was greatly affected by the presence of H2S, but there was no effect on the capacity due to the presence of H2S in synthesis gas. The presence of H2S decreased reduction reaction rates significantly, but oxidation rates of reduced samples increased. X-ray diffraction (XRD) data of the oxidized samples after a five-cycle test showed stable crystalline phases without any formation of sulfides or sulfites/sulfates. Increase in reaction temperature to 900 C had a positive effect on the performance.

  17. Light enhanced calcification in Stylophora pistillata: effects of glucose, glycerol and oxygen

    PubMed Central

    Tambutté, Eric; Allemand, Denis; Tambutté, Sylvie

    2014-01-01

    Zooxanthellate corals have long been known to calcify faster in the light than in the dark, however the mechanism underlying this process has been uncertain. Here we tested the effects of oxygen under controlled pCO2 conditions and fixed carbon sources on calcification in zooxanthellate and bleached microcolonies of the branching coral Stylophora pistillata. In zooxanthellate microcolonies, oxygen increased dark calcification rates to levels comparable to those measured in the light. However in bleached microcolonies oxygen alone did not enhance calcification, but when combined with a fixed carbon source (glucose or glycerol), calcification increased. Respiration rates increased in response to oxygen with greater increases when oxygen is combined with fixed carbon. ATP content was largely unaffected by treatments, with the exception of glycerol which decreased ATP levels. PMID:24883242

  18. Low-Dose Oxygen Enhances Macrophage-Derived Bacterial Clearance following Cigarette Smoke Exposure.

    PubMed

    Bain, William G; Tripathi, Ashutosh; Mandke, Pooja; Gans, Jonathan H; D'Alessio, Franco R; Sidhaye, Venkataramana K; Aggarwal, Neil R

    2016-01-01

    Background. Chronic obstructive pulmonary disease (COPD) is a common, smoking-related lung disease. Patients with COPD frequently suffer disease exacerbations induced by bacterial respiratory infections, suggestive of impaired innate immunity. Low-dose oxygen is a mainstay of therapy during COPD exacerbations; yet we understand little about whether oxygen can modulate the effects of cigarette smoke on lung immunity. Methods. Wild-type mice were exposed to cigarette smoke for 5 weeks, followed by intratracheal instillation of Pseudomonas aeruginosa (PAO1) and 21% or 35-40% oxygen. After two days, lungs were harvested for PAO1 CFUs, and bronchoalveolar fluid was sampled for inflammatory markers. In culture, macrophages were exposed to cigarette smoke and oxygen (40%) for 24 hours and then incubated with PAO1, followed by quantification of bacterial phagocytosis and inflammatory markers. Results. Mice exposed to 35-40% oxygen after cigarette smoke and PAO1 had improved survival and reduced lung CFUs and inflammation. Macrophages from these mice expressed less TNF-α and more scavenger receptors. In culture, macrophages exposed to cigarette smoke and oxygen also demonstrated decreased TNF-α secretion and enhanced phagocytosis of PAO1 bacteria. Conclusions. Our findings demonstrate a novel, protective role for low-dose oxygen following cigarette smoke and bacteria exposure that may be mediated by enhanced macrophage phagocytosis.

  19. Enhanced oxidative vaporization of Cr2O3 and chromium by oxygen atoms

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

    1974-01-01

    Rates of oxidative vaporization of Cr2O3 have been found to be markedly enhanced in the presence of oxygen atoms. Investigations were conducted over the temperature range 200-1250 C. For Cr2O3 the enhancement was about 10 to the 9th power at 550 C in oxygen containing 2.5% atoms. Rapid oxidative vaporization of bare chromium was observed below 800 C, the rate being about one-half that of Cr2O3. Results are interpreted in terms of thermochemical analysis.

  20. Predictive Evaluations of Oxygen-Rich Hydrocarbon Combustion Gas-Centered Swirl Coaxial Injectors using a Flamelet-Based 3-D CFD Simulation Approach

    NASA Technical Reports Server (NTRS)

    Richardson, Brian R.; Braman, Kalem; West, Jeff

    2016-01-01

    NASA Marshall Space Flight Center (MSFC) has embarked upon a joint project with the Air Force to improve the state-of-the-art of space application combustion device design and operational understanding. One goal of the project is to design, build and hot-fire test a 40,000 pound-thrust Oxygen/Rocket Propellant-2 (RP-2) Oxygen-Rich staged engine at MSFC. The overall project goals afford the opportunity to test multiple different injector designs and experimentally evaluate the any effect on the engine performance and combustion dynamics. To maximize the available test resources and benefits, pre-test, combusting flow, Computational Fluid Dynamics (CFD) analysis was performed on the individual injectors to guide the design. The results of the CFD analysis were used to design the injectors for specific, targeted fluid dynamic features and the analysis results also provided some predictive input for acoustic and thermal analysis of the main Thrust Chamber Assembly (TCA). MSFC has developed and demonstrated the ability to utilize a computationally efficient, flamelet-based combustion model to guide the pre-test design of single-element Gas Centered Swirl Coaxial (GCSC) injectors. Previous, Oxygen/RP-2 simulation models utilizing the Loci-STREAM flow solver, were validated using single injector test data from the EC-1 Air Force test facility. The simulation effort herein is an extension of the validated, CFD driven, single-injector design approach applied to single injectors which will be part of a larger engine array. Time-accurate, Three-Dimensional, CFD simulations were performed for five different classes of injector geometries. Simulations were performed to guide the design of the injector to achieve a variety of intended performance goals. For example, two GCSC injectors were designed to achieve stable hydrodynamic behavior of the propellant circuits while providing the largest thermal margin possible within the design envelope. While another injector was designed

  1. Hemoglobin-based oxygen carrier and convection enhanced oxygen transport in a hollow fiber bioreactor.

    PubMed

    Chen, Guo; Palmer, Andre F

    2009-04-15

    A mathematical model was developed to study O(2) transport in a convection enhanced hepatic hollow fiber (HF) bioreactor, with hemoglobin-based O(2) carriers (HBOCs) present in the flowing cell culture media stream of the HF lumen. In this study, four HBOCs were evaluated: PEG-conjugated human hemoglobin (MP4), human hemoglobin (hHb), bovine hemoglobin (BvHb) and polymerized bovine hemoglobin (PolyBvHb). In addition, two types of convective flow in the HF extra capillary space (ECS) were considered in this study. Starling flow naturally occurs when both of the ECS ports are closed. If one of the ECS ports is open, forced convective flow through the ECS will occur due to the imposed pressure difference between the lumen and ECS. This type of flow is referred to as cross-flow in this work, since some of the fluid entering the HF lumen will pass across the HF membrane and exit via the open ECS port. In this work, we can predict the dissolved O(2) concentration profile as well as the O(2) transport flux in an individual HF of the bioreactor by solving the coupled momentum and mass transport equations. Our results show that supplementation of the cell culture media with HBOCs can dramatically enhance O(2) transport to the ECS (containing hepatocytes) and lead to the formation of an in vivo-like O(2) spectrum for the optimal culture of hepatocytes. However, both Starling flow and cross-flow have a very limited effect on O(2) transport in the ECS. Taken together, this work represents a novel predictive tool that can be used to design or analyze HF bioreactors that expose cultured cells to defined overall concentrations and gradients of O(2).

  2. Combustion-derived flame generated ultrafine soot generates reactive oxygen species and activates Nrf2 antioxidants differently in neonatal and adult rat lungs

    PubMed Central

    2013-01-01

    Background Urban particulate matter (PM) has been epidemiologically correlated with multiple cardiopulmonary morbidities and mortalities, in sensitive populations. Children exposed to PM are more likely to develop respiratory infections and asthma. Although PM originates from natural and anthropogenic sources, vehicle exhaust rich in polycyclic aromatic hydrocarbons (PAH) can be a dominant contributor to the PM2.5 and PM0.1 fractions and has been implicated in the generation of reactive oxygen species (ROS). Objectives Current studies of ambient PM are confounded by the variable nature of PM, so we utilized a previously characterized ethylene-combusted premixed flame particles (PFP) with consistent and reproducible physiochemical properties and 1) measured the oxidative potential of PFP compared to ambient PM, 2) determined the ability of PFPs to generate oxidative stress and activate the transcription factor using in vitro and ex vivo models, and 3) we correlated these responses with antioxidant enzyme expression in vivo. Methods We compared oxidative stress response (HMOX1) and antioxidant enzyme (SOD1, SOD2, CAT, and PRDX6) expression in vivo by performing a time-course study in 7-day old neonatal and young adult rats exposed to a single 6-hour exposure to 22.4 μg/m3 PFPs. Results We showed that PFP is a potent ROS generator that induces oxidative stress and activates Nrf2. Induction of the oxidative stress responsive enzyme HMOX1 in vitro was mediated through Nrf2 activation and was variably upregulated in both ages. Furthermore, antioxidant enzyme expression had age and lung compartment variations post exposure. Of particular interest was SOD1, which had mRNA and protein upregulation in adult parenchyma, but lacked a similar response in neonates. Conclusions We conclude that PFPs are effective ROS generators, comparable to urban ambient PM2.5, that induce oxidative stress in neonatal and adult rat lungs. PFPs upregulate a select set of antioxidant enzymes in

  3. Hydrogen production with CO 2 capture by coupling steam reforming of methane and chemical-looping combustion: Use of an iron-based waste product as oxygen carrier burning a PSA tail gas

    NASA Astrophysics Data System (ADS)

    Ortiz, María; Gayán, Pilar; de Diego, Luis F.; García-Labiano, Francisco; Abad, Alberto; Pans, Miguel A.; Adánez, Juan

    In this work it is analyzed the performance of an iron waste material as oxygen carrier for a chemical-looping combustion (CLC) system. CLC is a novel combustion technology with the benefit of inherent CO 2 separation that can be used as a source of energy for the methane steam reforming process (SR). The tail gas from the PSA unit is used as fuel in the CLC system. The oxygen carrier behaviour with respect to gas combustion was evaluated in a continuous 500 W th CLC prototype using a simulated PSA off-gas stream as fuel. Methane or syngas as fuel were also studied for comparison purposes. The oxygen carrier showed enough high oxygen transport capacity and reactivity to fully convert syngas at 880 °C. However, lower conversion of the fuel was observed with methane containing fuels. An estimated solids inventory of 1600 kg MW th -1 would be necessary to fully convert the PSA off-gas to CO 2 and H 2O. An important positive effect of the oxygen carrier-to-fuel ratio up to 1.5 and the reactor temperature on the combustion efficiency was found. A characterization of the calcined and after-used particles was carried out showing that this iron-based material can be used as oxygen carrier in a CLC plant since particles maintain their properties (reactivity, no agglomeration, high durability, etc.) after more than 111 h of continuous operation.

  4. Vacancy–Vacancy Interaction Induced Oxygen Diffusivity Enhancement in Undoped Nonstoichiometric Ceria

    DOE PAGES

    Yuan, Fenglin; Zhang, Yanwen; Weber, William J.

    2015-05-19

    In this paper, molecular dynamics simulations and molecular static calculations have been used to systematically study oxygen vacancy transport in undoped nonstoichiometric ceria. A strong oxygen diffusivity enhancement appears in the vacancy concentration range of 2–4% over the temperature range from 1000 to 2000 K. An Arrhenius ion diffusion mechanism by vacancy hopping along the (100) direction is unambiguously identified, and an increasing trend of both the oxygen migration barrier and the prefactor with increasing vacancy concentration is observed. Within the framework of classical diffusion theory, a weak concentration dependence of the prefactor in oxygen vacancy migration is shown tomore » be crucial for explaining the unusual fast oxygen ion migration in the low concentration range and consequently the appearance of a maximum in oxygen diffusivity. Finally, a representative (100) direction interaction model is constructed to identify long-range vacancy–vacancy interaction as the structural origin of the positive correlation between oxygen migration barrier and vacancy concentration.« less

  5. Enhanced Bifunctional Oxygen Catalysis in Strained LaNiO3 Perovskites

    SciTech Connect

    Petrie, Jonathan R.; Cooper, Valentino R.; Freeland, John W.; Meyer, Tricia L.; Zhang, Zhiyong; Lutterman, Daniel A.; Lee, Ho Nyung

    2016-03-02

    Strain is known to greatly influence low temperature oxygen electro catalysis on noble metal films, leading to significant enhancements in bifunctional activity essential for fuel cells and Metal-air batteries. However, its catalytic impact on transition-metal oxide thin films, such as perovskites, is not widely understood. Here, we epitaxially strain the conducting perovskite LaNiO3 to systematically determine its influence on both the oxygen reduction and oxygen evolution reaction. Uniquely, we found that compressive strain could significantly enhance both reactions, yielding a bifunctional catalyst that surpasses the performance of noble metals' such as Pt. We attribute the improved bifunctionality to strain induced splitting of the e(g) Orbitals, which can customize orbital asymmetry at the surface. Analogous to strain induced shifts in the d-band center of noble metals relative to the Fermi level, :such splitting can dramatically affect catalytic activity in this perovskite and other potentially more active Oxides.

  6. Reversed flow fluidized-bed combustion apparatus

    DOEpatents

    Shang, Jer-Yu; Mei, Joseph S.; Wilson, John S.

    1984-01-01

    The present invention is directed to a fluidized-bed combustion apparatus provided with a U-shaped combustion zone. A cyclone is disposed in the combustion zone for recycling solid particulate material. The combustion zone configuration and the recycling feature provide relatively long residence times and low freeboard heights to maximize combustion of combustible material, reduce nitrogen oxides, and enhance sulfur oxide reduction.

  7. Plasma-Enhanced Combustion of Hydrocarbon Fuels and Fuel Blends Using Nanosecond Pulsed Discharges

    SciTech Connect

    Cappelli, Mark; Mungal, M Godfrey

    2014-10-28

    This project had as its goals the study of fundamental physical and chemical processes relevant to the sustained premixed and non-premixed jet ignition/combustion of low grade fuels or fuels under adverse flow conditions using non-equilibrium pulsed nanosecond discharges.

  8. Experimental and Modeling Studies of the Characteristics of Liquid Biofuels for Enhanced Combustion

    SciTech Connect

    Meeks, E.; Modak, A. U.; Naik, C. V.; Puduppakkam, K. V.; Westbrook, C.; Egolfopoulos, F. N.; Tsotsis, T.; Roby, S. H.

    2009-07-01

    The objectives of this project have been to develop a comprehensive set of fundamental data regarding the combustion behavior of biodiesel fuels and appropriately associated model fuels that may represent biodiesels in automotive engineering simulation. Based on the fundamental study results, an auxiliary objective was to identify differentiating characteristics of molecular fuel components that can be used to explain different fuel behavior and that may ultimately be used in the planning and design of optimal fuel-production processes. The fuels studied in this project were BQ-9000 certified biodiesel fuels that are certified for use in automotive engine applications. Prior to this project, there were no systematic experimental flame data available for such fuels. One of the key goals has been to generate such data, and to use this data in developing and verifying effective kinetic models. The models have then been reduced through automated means to enable multi-dimensional simulation of the combustion characteristics of such fuels in reciprocating engines. Such reliable kinetics models, validated against fundamental data derived from laminar flames using idealized flow models, are key to the development and design of optimal engines, engine operation and fuels. The models provide direct information about the relative contribution of different molecular constituents to the fuel performance and can be used to assess both combustion and emissions characteristics. During this project, we completed a major and thorough validation of a set of biodiesel surrogate components, allowing us to begin to evaluate the fundamental combustion characteristics for B100 fuels.

  9. Characterization of chemical looping combustion of coal in a 1 kW{sub th} reactor with a nickel-based oxygen carrier

    SciTech Connect

    Shen, Laihong; Wu, Jiahua; Gao, Zhengping; Xiao, Jun

    2010-05-15

    Chemical looping combustion is a novel technology that can be used to meet the demand on energy production without CO{sub 2} emission. To improve CO{sub 2} capture efficiency in the process of chemical looping combustion of coal, a prototype configuration for chemical looping combustion of coal is made in this study. It comprises a fast fluidized bed as an air reactor, a cyclone, a spout-fluid bed as a fuel reactor and a loop-seal. The loop-seal connects the spout-fluid bed with the fast fluidized bed and is fluidized by steam to prevent the contamination of the flue gas between the two reactors. The performance of chemical looping combustion of coal is experimentally investigated with a NiO/Al{sub 2}O{sub 3} oxygen carrier in a 1 kW{sub th} prototype. The experimental results show that the configuration can minimize the amount of residual char entering into the air reactor from the fuel reactor with the external circulation of oxygen carrier particles giving up to 95% of CO{sub 2} capture efficiency at a fuel reactor temperature of 985 C. The effect of the fuel reactor temperature on the release of gaseous products of sulfur species in the air and fuel reactors is carried out. The fraction of gaseous sulfur product released in the fuel reactor increases with the fuel reactor temperature, whereas the one in the air reactor decreases correspondingly. The high fuel reactor temperature results in more SO{sub 2} formation, and H{sub 2}S abatement in the fuel reactor. The increase of SO{sub 2} in the fuel reactor accelerates the reaction of SO{sub 2} with CO to form COS, and COS concentration in the fuel reactor exit gas increases with the fuel reactor temperature. The SO{sub 2} in the air reactor exit gas is composed of the product of sulfur in residual char burnt with air and that of nickel sulfide oxidization with air in the air reactor. Due to the evident decrease of residual char in the fuel reactor with increasing fuel reactor temperature, it results in the

  10. Combustion synthesized TiO{sub 2} for enhanced photocatalytic activity under the direct sunlight-optimization of titanylnitrate synthesis

    SciTech Connect

    Daya Mani, A.; Laporte, V.; Ghosal, P.; Subrahmanyam, Ch.

    2012-09-15

    Graphical abstract: Effect of oxidant on the combustion synthesis of TiO{sub 2} has been studied by preparing titanylnitrate in four different ways from Ti(IV) iso-propoxide. It is observed that oxidant preparation method has a significant effect on physico-chemical as well as photocatalytic properties of TiO{sub 2}. All the catalysts showed excellent photocatalytic activity than Degussa P-25 under direct sunlight for the degradation of a textile dye (methylene blue), without the need of external light sources, oxygen supply and reactor systems. Highlights: ► Optimized synthesis of titanylnitrate. ► Influence of titanylnitrate synthesis on the physico-chemical properties of TiO{sub 2} prepared by combustion synthesis. ► Development of highly efficient TiO{sub 2} photocatalysts those are active under the direct sunlight in open atmosphere. ► Degradation of the textile dye (methylene blue) under direct sunlight. -- Abstract: Optimized synthesis of Ti-precursor ‘titanylnitrate’ for one step combustion synthesis of N- and C-doped TiO{sub 2} catalysts were reported and characterized by using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), diffused reflectance UV–vis spectroscopy, N{sub 2} adsorption and X-ray photoelectron spectroscopy (XPS). XRD confirmed the formation of TiO{sub 2} anatase and nano-crystallite size which was further confirmed by TEM. UV-DRS confirmed the decrease in the band gap to less than 3.0 eV, which was assigned due to the presence of C and N in the framework of TiO{sub 2} as confirmed by X-ray photoelectron spectroscopy. Degradation of methylene blue in aqueous solution under the direct sunlight was carried out and typical results indicated the better performance of the synthesized catalysts than Degussa P-25.

  11. Switching Oxygen Reduction Pathway by Exfoliating Graphitic Carbon Nitride for Enhanced Photocatalytic Phenol Degradation.

    PubMed

    Zhang, Hui; Guo, Liang-Hong; Zhao, Lixia; Wan, Bin; Yang, Yu

    2015-03-19

    The selectivity of molecular oxygen activation on the exfoliated graphitic carbon nitride (g-C3N4) and its influence on the photocatalytic phenol degradation process were demonstrated. Compared with bulk g-C3N4, the exfoliated nanosheet yielded a 3-fold enhancement in photocatalytic phenol degradation. ROS trapping experiments demonstrated that although the direct hole oxidation was mainly responsible for phenol photodegradation on both g-C3N4 catalysts, molecular oxygen activation processes on their surface greatly influenced the whole phenol degradation efficiency. Reactive oxygen species and Raman spectroscopy measurements revealed that oxygen was preferentially reduced to ·O2(-) by one-electron transfer on bulk g-C3N4, while on g-C3N4 nanosheet the production of H2O2 via a two-electron transfer process was favored due to the rapid formation of surface-stabilized 1,4-endoperoxide. The latter process not only promotes the separation of photogenerated electron-hole pairs but also greatly facilitates reactive oxygen species formation and subsequently enhances phenol degradation.

  12. Reactivity deterioration of NiO/Al{sub 2}O{sub 3} oxygen carrier for chemical looping combustion of coal in a 10 kW{sub th} reactor

    SciTech Connect

    Shen, Laihong; Wu, Jiahua; Gao, Zhengping; Xiao, Jun

    2009-07-15

    A relatively long-term experiment for chemical looping combustion of coal with NiO/Al{sub 2}O{sub 3} oxygen carrier was carried out in a 10 kW{sub th} continuous reactor of interconnected fluidized beds, and 100 h of operation was reached with the same batch of the oxygen carrier. The reactivity deterioration of the oxygen carriers was present during the experimental period. The reactivity deterioration of reacted oxygen carriers at different experimental stages was evaluated using X-ray diffraction (XRD), scanning electron microscope (SEM), and X-ray fluorescence spectrometer. SEM analysis showed no significant change in the morphology of the nickel-based oxygen carrier at the fuel reactor temperature {<=}940 C, but loss of surface area and porosity of reacted oxygen carriers was observed when the fuel reactor temperature exceeded 960 C. The results show that the sintering effect have mainly contributed to the reactivity deterioration of reacted oxygen carriers in the CLC process for coal, while the effects of coal ash and sulfur can be ignored. The oxidization of reduced oxygen carrier with air was an intensive exothermic process, and the high temperature of oxygen carrier particles led to sintering on the surface of oxygen carrier particles in the air reactor. Attention must be paid to control the external circulation of oxygen carrier particles in the interconnected fluidized beds in order to efficiently transport heat from the air reactor to the fuel reactor, and reduce the temperature of oxygen carrier particles in the air reactor. Improvement of reactivity deterioration of reacted oxygen carriers was achieved by the supplement of steam into the fuel reactor. Nevertheless, NiO/Al{sub 2}O{sub 3} is still one of the optimal oxygen carriers for chemical looping combustion of coal if the sintering of oxygen carrier is minimized at the suitable reactor temperature. (author)

  13. Kinetics of Oxidation of a Reduced Form of the Cu-Based Oxygen-Carrier for Use in Chemical-Looping Combustion

    NASA Astrophysics Data System (ADS)

    Chuang, S. Y.; Dennis, J. S.; Hayhurst, A. N.; Scott, S. A.

    A co-precipitated mixture of CuO and Al2O3 is a good oxygen-carrier for chemical-looping combustion. The kinetics of regeneration of this reduced oxygen-carrier (355 - 500 urn) were measured from 300 to 750°C when reacting it with O2. Care was taken to ensure these measurements were not affected by interphase mass transfer. Efforts were also made to minimise sampling problems by using a rapid-response mass spectrometer for reactions lasting for 45 s or less; otherwise, a paramagnetic analyser for O2 was used, since the mass spectrometer drifted with time. The order of reaction with respect to O2 was found to be ˜ unity at 300 to 750°C. Below 600°C, the reduced oxygen-carrier was incompletely oxidised to a mixture of CU2O and Al2O3. Above 600°C, regeneration was completely to CuO and Al2O3 and was controlled to a considerable extent by external mass transfer. At these higher temperatures, regeneration involved a shrinking core mechanism and the two consecutive steps: 2Cu + 1/2O_2 to Cu_2 O, Cu_2 O + 1/2O_2 to 2CuO. The activation energies and pre-exponential factors for both reactions were measured from initial rates. The kinetics in the first cycle of operations were found to be similar to those in the subsequent cycles.

  14. Sol-gel-derived NiO/NiAl{sub 2}O{sub 4} oxygen carriers for chemical-looping combustion by coal char

    SciTech Connect

    Haibo Zhao; Liming Liu; Baowen Wang; Di Xu; Linlin Jiang; Chuguang Zheng

    2008-03-15

    This paper focuses on the investigation of Ni-based oxygen carriers for CLC by coal char. First, Al(OC{sub 3}H{sub 7}){sub 3} and Ni(NO{sub 3}){sub 2} are selected as the main raw materials to prepare sol-gel-derived NiO/NiAl{sub 2}O{sub 4} oxygen carriers. The oxygen carrier with a mass content of 60% NiO, a sintering temperature of 1300{sup o}C, and a sintering time of 6 h performs comparatively well. Second, the reduction reaction of the NiO/NiAl{sub 2}O{sub 4} oxygen carriers with char and the circular reduction/oxidation reactions of the NiO/NiAl{sub 2}O{sub 4} oxygen carriers with char/air or hydrogen/air are carried out in a thermogravimetric analysis (TGA) instrument to investigate the reactivities and chemical life of the prepared NiO/NiAl{sub 2}O{sub 4} oxygen carriers. The experimental results show that (a) when the TGA temperature is higher than 850{sup o}C, NiO/NiAl{sub 2}O{sub 4} starts to react with coal char rapidly, which indicates that CLC of coal char using NiO/NiAl{sub 2}O{sub 4} as oxygen carriers is a feasible technology of energy utilization in principle; (b) NiO/NiAl{sub 2}O{sub 4}, which maintains its activity over single-cycle reduction/oxidation reactions with char/air or multiple-cycle reduction/oxidation reactions with hydrogen/air, exhibits extremely good recyclablity; (c) the porous beehive structure of the NiO/NiAl{sub 2}O{sub 4} particle is maintained, and the sintering behavior between different particles is not observed during cyclic studies. Those experimental results prove the sol-gel-derived oxygen carrier NiO/NiAl{sub 2}O{sub 4} is capable of being used in chemical-looping combustion fueled by coal char or H{sub 2}. 51 refs., 5 figs., 5 tabs.

  15. Out-of-Plane Coordinated Porphyrin Nanotubes with Enhanced Singlet Oxygen Generation Efficiency

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang; Wang, Yao; Xu, Yanshuang; Yan, Yun; Huang, Jianbin

    2016-08-01

    A supramolecular porphyrin nanotube displaying J-aggregation feature was constructed by out-of-plane coordinated bismuth-porphyrin. Significantly, compared to traditional J-aggregated porphyrin suffering from fluorescence and singlet oxygen quenching, the nanotube exhibits excellent bio-imaging ability and enhanced production efficiency of singlet oxygen. The out-of-plane structure of bismuth to porphyrin makes the aggregation an appropriate material for theranostics. Furthermore, it is also a potential radio-therapeutic drug owing to the presence of radio-active bismuth. Thus, the self-assembly of out-of-plane coordinated porphyrin can be a facile approach toward effective therapy of tumors and other diseases.

  16. Detection of Molecular Oxygen at Low Concentrations Using Quartz Enhanced Photoacoustic Spectroscopy

    PubMed Central

    Pohlkötter, Andreas; Köhring, Michael; Willer, Ulrike; Schade, Wolfgang

    2010-01-01

    Molecular oxygen is detected at low concentrations using photoacoustic spectroscopy despite its unfavorable photoacoustic properties. The system consists of a seed laser diode, a tapered amplifier and a quartz tuning fork based spectrophone, thus employing quartz enhanced photoacoustic spectroscopy (QEPAS). With this system a detection limit of 13 ppm is reached with a compact and long term stable setup. Further improvement of the detection limit is possible by adding suitable gases to the sample gas that promote the radiationless de-excitation of the oxygen molecules. PMID:22163666

  17. Detection of molecular oxygen at low concentrations using quartz enhanced photoacoustic spectroscopy.

    PubMed

    Pohlkötter, Andreas; Köhring, Michael; Willer, Ulrike; Schade, Wolfgang

    2010-01-01

    Molecular oxygen is detected at low concentrations using photoacoustic spectroscopy despite its unfavorable photoacoustic properties. The system consists of a seed laser diode, a tapered amplifier and a quartz tuning fork based spectrophone, thus employing quartz enhanced photoacoustic spectroscopy (QEPAS). With this system a detection limit of 13 ppm is reached with a compact and long term stable setup. Further improvement of the detection limit is possible by adding suitable gases to the sample gas that promote the radiationless de-excitation of the oxygen molecules.

  18. Utilization of spent activated carbon to enhance the combustion efficiency of organic sludge derived fuel.

    PubMed

    Chen, Wei-Sheng; Lin, Chang-Wen; Chang, Fang-Chih; Lee, Wen-Jhy; Wu, Jhong-Lin

    2012-06-01

    This study examines the heating value and combustion efficiency of organic sludge derived fuel, spent activated carbon derived fuel, and derived fuel from a mixture of organic sludge and spent activated carbon. Spent activated carbon was sampled from an air pollution control device of an incinerator and characterized by XRD, XRF, TG/DTA, and SEM. The spent activated carbon was washed with deionized water and solvent (1N sulfuric acid) and then processed by the organic sludge derived fuel manufacturing process. After washing, the salt (chloride) and sulfide content could be reduced to 99% and 97%, respectively; in addition the carbon content and heating value were increased. Different ratios of spent activated carbon have been applied to the organic sludge derived fuel to reduce the NO(x) emission of the combustion.

  19. Study of Electrostatic Modulation of Fuel Sprays to Enhance Combustion Performance in an Aviation Gas Turbine

    DTIC Science & Technology

    1987-06-01

    Electrostatic spraying has found practical application in such diverse areas as high- speed ink- jet printing , pesticide, paint and liquid metal... Electrohydrodynamically Sprayed Liquid Droplets," The Physics of Fluids, V. 10, pp. 2149-2154, October 1967. 8. Rayleigh, J. W. S., "On the Instability of Jets ...biock number) I ELD OGROUP SUB. GR. Electrohydrodynamic Spraying, Electrostatic f I Atomization, Gas Turbine Combustor, Combustion UTRACT (Continue

  20. Combustion synthesized rod-like nanostructure hematite with enhanced lithium storage properties

    SciTech Connect

    Xiong, Q.Q.; Shi, S.J.; Tang, H.; Wang, X.L.; Gu, C.D.; Tu, J.P.

    2015-01-15

    Graphical abstract: Fe{sub 2}O{sub 3} nanorods are synthesized by combustion method using alcohol as both solvent and fuel. As an anode material for lithium-ion batteries, the Fe{sub 2}O{sub 3} nanorod electrode delivers good electrochemical performance. - Highlights: • We prepared Fe{sub 2}O{sub 3} nanorod by a facile and powerful combustion method. • The Fe{sub 2}O{sub 3} nanorod shows high capacity, good cycle stability, and rate performance. • Combustion saves time and energy to meet the demand of green and sustainable industry. - Abstract: Fe{sub 2}O{sub 3} nanorods are synthesized by combustion method using alcohol as both solvent and fuel, which is a facile and effective strategy for the large-scale and inexpensive fabrication. The Fe{sub 2}O{sub 3} nanorods are with the well distributed diameters of 20–30 nm and length ranging from 80 to 100 nm. As an anode material for lithium-ion batteries, the Fe{sub 2}O{sub 3} nanorod electrode delivers a high discharge capacity of 761.7 mA h g{sup −1} after 60 cycles at 500 mA g{sup −1}, and 727.2 mA h g{sup −1} at a high current density of 2000 mA g{sup −1}. The good electrochemical performance is attributed to the sufficient contact of active material and electrolyte, large surface area, and short diffusion length of Li{sup +}.

  1. Enhanced singlet oxygen generation from PLGA loaded with verteporfin and gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Deng, Wei; Kautzka, Zofia; Goldys, Ewa M.

    2016-12-01

    In this study, poly(lactic-co-glycolic acid) (PLGA) nanocomposites were developed by incorporating a photosensitizer, verteporfin and gold nanoparticles into this polymeric matrix and utilised for enhanced photoynamic therapy. Both enhanced fluorescence and singlet oxygen generation from verteporfin were observed in this new formulation under both 425nm LED and 405nm laser illumination. A maximum enhancement factor of 2.5 for fluorescence and 1.84 for 1O2 generation was obtained when the molar ratio of gold:VP was 5:1 and excited at 425 nm, compared with PLGA doped with verteporfin only. The experiment results could be explained by the local electric field enhancement of gold nanoparticles. Furthermore, in vitro cell-killing effect on human pancreatic cancer cells was also demonstrated by using this new formulation following light exposure, indicating the utility of these nanocomposites for enhanced photodynamic therapy.

  2. Influence of different types of coals and stoves on the emissions of parent and oxygenated PAHs from residential coal combustion in China.

    PubMed

    Wang, Yan; Xu, Yue; Chen, Yingjun; Tian, Chongguo; Feng, Yanli; Chen, Tian; Li, Jun; Zhang, Gan

    2016-05-01

    To evaluate the influence of coal property and stove efficiency on the emissions of parent polycyclic aromatic hydrocarbons (pPAHs) and oxygenated PAHs (oPAHs) during the combustion, fifteen coal/stove combinations were tested in this study, including five coals of different geological maturities in briquette and chunk forms burned in two residential stoves. The emission factors (EFs) of pPAHs and oPAHs were in the range of 0.129-16.7 mg/kg and 0.059-0.882 mg/kg, respectively. The geological maturity of coal significantly affected the emissions of pPAHs and oPAHs with the lower maturity coals yielding the higher emissions. The chunk-to-briquette transformation of coal dramatically increased the emissions of pPAHs and oPAHs during the combustion of anthracite, whereas this transformation only elevated the emissions of high molecular weight PAHs for bituminous coals. The influence of stove type on the emissions of pPAHs and oPAHs was also geological-maturity-dependent. High efficiency stove significantly reduced the emissions of PAHs from those relatively high-maturity coals, but its influences on low-maturity coals were inconstant.

  3. Flame temperature measurements by radar resonance-enhanced multiphoton ionization of molecular oxygen.

    PubMed

    Wu, Yue; Sawyer, Jordan; Zhang, Zhili; Adams, Steven F

    2012-10-01

    Here we report nonintrusive local rotational temperature measurements of molecular oxygen, based on coherent microwave scattering (radar) from resonance-enhanced multiphoton ionization (REMPI) in room air and hydrogen/air flames. Analyses of the rotational line strengths of the two-photon molecular oxygen C(3)Π(v=2)←X(3)Σ(v'=0) transition have been used to determine the hyperfine rotational state distribution of the ground X(3)Σ(v'=0) state. Rotationally resolved 2+1 REMPI spectra of the molecular oxygen C(3)Π(v=2)←X(3)Σ(v'=0) transition at different temperatures were obtained experimentally by radar REMPI. Rotational temperatures have been determined from the resulting Boltzmann plots. The measurements in general had an accuracy of ~±60 K in the hydrogen/air flames at various equivalence ratios. Discussions about the decreased accuracy for the temperature measurement at elevated temperatures have been presented.

  4. Contrast Enhancement for in vivo Visible Reflectance Imaging of Tissue Oxygenation

    PubMed Central

    Crane, Nicole J.; Schultz, Zachary D.; Levin, Ira W.

    2009-01-01

    Results are presented illustrating a straightforward algorithm to be used for real time monitoring of oxygenation levels in blood cells and tissue based on the visible spectrum of hemoglobin. Absorbance images obtained from the visible reflection of white light through separate red and blue bandpass filters recorded by monochrome CCDs are combined to create enhanced images that suggest a quantitative correlation to the degree of oxygenated and deoxygenated hemoglobin in red blood cells. The filter bandpass regions are chosen specifically to mimic the color response of commercial 3-CCD cameras, representative of detectors with which the operating room laparoscopic tower systems are equipped. Adaptation of this filter approach is demonstrated for laparoscopic donor nephrectomies in which images are analyzed in terms of real time, in vivo monitoring of tissue oxygenation. PMID:17716397

  5. Reduction kinetics of Cu-, Ni-, and Fe-based oxygen carriers using syngas (CO + H{sub 2}) for chemical-looping combustion

    SciTech Connect

    Alberto Abad; Francisco Garcia-Labiano; Luis F. de Diego; Pilar Gayn; Juan Adnez

    2007-08-15

    The reactivity of three Cu-, Fe-, and Ni-based oxygen carriers to be used in a chemical-looping combustion (CLC) system using syngas as fuel has been analyzed. The oxygen carriers exhibited high reactivity during reduction with fuel gases present in syngas (H{sub 2} and CO), with average values in the range 8-30% min{sup -1}. No effect of the gas products (H{sub 2}O, CO{sub 2}) on the reduction reaction rate was detected. The kinetic parameters of reaction with H{sub 2} and CO have been determined by thermogravimetric analysis. The grain model with spherical or platelike geometry in the grain was used for the kinetic determination, in which the chemical reaction controlled the global reaction rate. The activation energies determined for these reactions were low, with values ranging from 14 to 33 kJ mol{sup -1}. The reaction order depended on the reacting gas, and values from 0.5 to 1 were found. Moreover, the reactivity of the oxygen carriers when both H{sub 2} and CO are simultaneously present in the reacting gases has been analyzed, both at atmospheric and pressurized conditions. For the Cu- and Fe-based oxygen carriers, the reaction rate of the oxygen carrier with syngas corresponded to the addition of the reaction rates for the individual fuel gases, H{sub 2} and CO. For the Ni-based oxygen carrier, the reaction rate was that corresponding to the fuel gas that reacted faster with the oxygen carrier at the reacting conditions (fuel concentration, temperature, and pressure). The consequences of the behavior of the reaction of syngas and the water-gas shift (WGS) equilibrium on the design of the fuel reactor of a CLC system have been analyzed. A preliminary estimation of the solids inventory for the use of syngas in the fuel reactor of a CLC system gave values in the range of 19-34 kg MW{sup -1} when the WGS equilibrium was considered to be instantaneous. 8 figs., 4 tabs.

  6. Oxygen-enhanced MRI accurately identifies, quantifies, and maps tumor hypoxia in preclinical cancer models

    PubMed Central

    O’Connor, James PB; Boult, Jessica KR; Jamin, Yann; Babur, Muhammad; Finegan, Katherine G; Williams, Kaye J; Little, Ross A; Jackson, Alan; Parker, Geoff JM; Reynolds, Andrew R; Waterton, John C; Robinson, Simon P

    2015-01-01

    There is a clinical need for non-invasive biomarkers of tumor hypoxia for prognostic and predictive studies, radiotherapy planning and therapy monitoring. Oxygen enhanced MRI (OE-MRI) is an emerging imaging technique for quantifying the spatial distribution and extent of tumor oxygen delivery in vivo. In OE-MRI, the longitudinal relaxation rate of protons (ΔR1) changes in proportion to the concentration of molecular oxygen dissolved in plasma or interstitial tissue fluid. Therefore, well-oxygenated tissues show positive ΔR1. We hypothesized that the fraction of tumor tissue refractory to oxygen challenge (lack of positive ΔR1, termed “Oxy-R fraction”) would be a robust biomarker of hypoxia in models with varying vascular and hypoxic features. Here we demonstrate that OE-MRI signals are accurate, precise and sensitive to changes in tumor pO2 in highly vascular 786-0 renal cancer xenografts. Furthermore, we show that Oxy-R fraction can quantify the hypoxic fraction in multiple models with differing hypoxic and vascular phenotypes, when used in combination with measurements of tumor perfusion. Finally, Oxy-R fraction can detect dynamic changes in hypoxia induced by the vasomodulator agent hydralazine. In contrast, more conventional biomarkers of hypoxia (derived from blood oxygenation-level dependent MRI and dynamic contrast-enhanced MRI) did not relate to tumor hypoxia consistently. Our results show that the Oxy-R fraction accurately quantifies tumor hypoxia non-invasively and is immediately translatable to the clinic. PMID:26659574

  7. Enhanced CO2 Resistance for Robust Oxygen Separation Through Tantalum-doped Perovskite Membranes.

    PubMed

    Zhang, Chi; Tian, Hao; Yang, Dong; Sunarso, Jaka; Liu, Jian; Liu, Shaomin

    2016-03-08

    Oxygen selective membranes with enhanced oxygen permeability and CO2 resistance are highly required in sustainable clean energy generation technologies. Here, we present novel, cobalt-free, SrFe1-x Tax O3-δ (x=0, 0.025, 0.05, 0.1, 0.2) perovskite membranes. Ta-doping induced lattice structure progression from orthorhombic (x=0) to cubic (x=0.05). SrFe0.95 Ta0.05 O3-δ (SFT0.05) showed the highest oxygen flux rates reaching 0.85 mL min(-1) cm(-2) at 950 °C on a 1.0 mm-thick membrane. Surface decoration can increase the permeation rate further. Ta inclusion within the perovskite lattice of SrFeO3-δ (SF) enhanced the CO2 resistance of the membranes significantly as evidenced by the absence of the carbonate functional groups on the FTIR spectrum when exposed to CO2 atmosphere at 850 °C. The CO2 resistance of Ta-doped SF compounds correlates with the lower basicity and the higher binding energy for the lattice oxygen. SFT0.05 demonstrated high stability during long-term permeation tests under 10% CO2 atmosphere.

  8. Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability.

    PubMed

    Dijkstra, Camelia E; Larkin, Oliver J; Anthony, Paul; Davey, Michael R; Eaves, Laurence; Rees, Catherine E D; Hill, Richard J A

    2011-03-06

    Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to reproduce aspects of weightlessness, on the Earth. We used a superconducting magnet to levitate growing bacterial cultures for up to 18 h, to determine the effect of diamagnetic levitation on all phases of the bacterial growth cycle. We find that diamagnetic levitation increases the rate of population growth in a liquid culture and reduces the sedimentation rate of the cells. Further experiments and microarray gene analysis show that the increase in growth rate is owing to enhanced oxygen availability. We also demonstrate that the magnetic field that levitates the cells also induces convective stirring in the liquid. We present a simple theoretical model, showing how the paramagnetic force on dissolved oxygen can cause convection during the aerobic phases of bacterial growth. We propose that this convection enhances oxygen availability by transporting oxygen around the liquid culture. Since this process results from the strong magnetic field, it is not present in other weightless environments, e.g. in Earth orbit. Hence, these results are of significance and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena.

  9. Diamagnetic levitation enhances growth of liquid bacterial cultures by increasing oxygen availability

    PubMed Central

    Dijkstra, Camelia E.; Larkin, Oliver J.; Anthony, Paul; Davey, Michael R.; Eaves, Laurence; Rees, Catherine E. D.; Hill, Richard J. A.

    2011-01-01

    Diamagnetic levitation is a technique that uses a strong, spatially varying magnetic field to reproduce aspects of weightlessness, on the Earth. We used a superconducting magnet to levitate growing bacterial cultures for up to 18 h, to determine the effect of diamagnetic levitation on all phases of the bacterial growth cycle. We find that diamagnetic levitation increases the rate of population growth in a liquid culture and reduces the sedimentation rate of the cells. Further experiments and microarray gene analysis show that the increase in growth rate is owing to enhanced oxygen availability. We also demonstrate that the magnetic field that levitates the cells also induces convective stirring in the liquid. We present a simple theoretical model, showing how the paramagnetic force on dissolved oxygen can cause convection during the aerobic phases of bacterial growth. We propose that this convection enhances oxygen availability by transporting oxygen around the liquid culture. Since this process results from the strong magnetic field, it is not present in other weightless environments, e.g. in Earth orbit. Hence, these results are of significance and timely to researchers considering the use of diamagnetic levitation to explore effects of weightlessness on living organisms and on physical phenomena. PMID:20667843

  10. Proliferation enhancement of budding yeast and mammalian cells with periodic oxygen radical treatment

    NASA Astrophysics Data System (ADS)

    Mori, Yosuke; Kobayashi, Jun; Murata, Tomiyasu; Hahizume, Hiroshi; Hori, Masaru; Ito, Masafumi

    2015-09-01

    Recently, nonequilibrium atmospheric-pressure plasmas have been intensively studied for biological applications. However, the each effect of species in plasmas to biological tissue has not been clarified yet because various factors exist in the plasmas. Accordingly, we have studied effects of atomic oxygen dose on cell growth such as budding yeast and mouse NIH3T3 fibroblasts of mammalian cells. Both of cells were suspended with PBS, and treated using oxygen radical source. In order to prevent the radicals from reacting with the ambient air, the treatment region was surrounded by a plastic cover and purged with Ar. The proliferative effect of 15 % was observed at the O3Pj dose of around 1 . 0 ×1017 cm-3 in NIH3T3 cells as well as in yeast cells. Moreover, periodic oxygen treatment enhanced the effect in budding yeast cells. The best interval of periodic oxygen radical treatment was around 2 hours, which is almost the same period as that of their cell cycle. With the optimum interval time, we have investigated the effect of the number of the treatments. As the number of treatments increases, the growth rate of budding yeast cells was gradually enhanced and saturated at thrice treatments. This work was partly supported by JSPS KAKENHI Grant Numbers 26286072 and project for promoting Research Center in Meijo University.

  11. Oxygenated drinking water enhances immune activity in broiler chicks and increases survivability against Salmonella Gallinarum in experimentally infected broiler chicks.

    PubMed

    Jung, Bock-Gie; Lee, Jin-A; Nam, Kyoung-Woo; Lee, Bong-Joo

    2012-03-01

    It has been suggested that drinking oxygenated water may improve oxygen availability, which may increase vitality and improving immune activity. The present study evaluated the immune enhancing effects of oxygenated drinking water in broiler chicks and demonstrated the protective efficacy of oxygenated drinking water against Salmonella Gallinarum in experimentally infected broiler chicks. Continuous drinking of oxygenated water markedly increased serum lysozyme activity, peripheral blood mononuclear cell proliferation and the CD4(+)/CD8(+) splenocyte ratio in broiler chicks. In the chicks experimentally infected with S. Gallinarum, oxygenated drinking water alleviated symptoms and increased survival. These findings suggest that oxygenated drinking water enhances immune activity in broiler chicks, and increases survivability against S. Gallinarum in experimentally infected broiler chicks.

  12. Enhancing surface functionality of reduced graphene oxide biosensors by oxygen plasma treatment for Alzheimer's disease diagnosis.

    PubMed

    Chae, Myung-Sic; Kim, Jinsik; Jeong, Dahye; Kim, YoungSoo; Roh, Jee Hoon; Lee, Sung Min; Heo, Youhee; Kang, Ji Yoon; Lee, Jeong Hoon; Yoon, Dae Sung; Kim, Tae Geun; Chang, Suk Tai; Hwang, Kyo Seon

    2017-06-15

    We performed oxygen plasma treatment on reduced graphene oxide (rGO) to improve its surface reactivity with respect to biomolecular interactions. Oxygen-plasma-treated rGO surfaces were employed as reactive interfaces for the detection of amyloid-beta (Aβ) peptides, the pathological hallmarks of Alzheimer's disease (AD), as the target analytes. By measuring the changes in electrical characteristics and confirmation through topographic analysis, the oxygen-plasma-treated rGO sensors had enhanced surface functionality for better antibody immobilization and sensing performance, with a 3.33-fold steeper slope for the electrical responses versus analyte concentration curve (logarithmic scale) compared to the untreated. The elicited biomolecular reactivity of the rGO surfaces with the oxygen plasma treatment remained at 46-51% of the initial value even after aging for 6h in ambient conditions. This phenomenon was also confirmed by pretreating the rGO surfaces with a blocking agent and subsequently subjecting them to antibody immobilization. Finally, the feasibility of the oxygen-plasma-treated rGO sensors as a diagnostic tool was evaluated with clinical samples of neural-derived exosomal Aβ peptides extracted from apparent AD patients and normal controls (NC). In contrast to the untreated sensors (p=0.0460), the oxygen-plasma-treated rGO sensors showed a significant p-value in the identification of clinical samples of AD and NC subjects (p<0.001). These results suggest that oxygen plasma treatment improves sensor performance without complicated fabrication procedures and should aid in the development of novel diagnostic tools based on carbon nanomaterials.

  13. Enhancement of oxidative vaporization of chromium (III) oxide and chromium by oxygen atoms

    NASA Technical Reports Server (NTRS)

    Fryburg, G. C.; Kohl, F. J.; Stearns, C. A.

    1974-01-01

    Rates of oxidative vaporization of Cr2O3 were found to be markedly enhanced in the presence of O atoms. Investigations were conducted over the temperature range 470 to 1520 K. For Cr2O3 the enhancement was about 10 to the 9th power at 820 K in oxygen containing 2.5 percent atoms. Rapid oxidative vaporization of bare chromium was observed below 1070 K, the rate being about one-half that of Cr2O3. Results are interpreted in terms of thermochemical analysis.

  14. Palladium–platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    SciTech Connect

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan

    2015-07-02

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. Ultimately, these results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.

  15. Palladium-platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction.

    PubMed

    Wang, Xue; Choi, Sang-Il; Roling, Luke T; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A; Mavrikakis, Manos; Xia, Younan

    2015-07-02

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. These results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.

  16. Ultraviolet irradiation-dependent fluorescence enhancement of hemoglobin catalyzed by reactive oxygen species.

    PubMed

    Pan, Leiting; Wang, Xiaoxu; Yang, Shuying; Wu, Xian; Lee, Imshik; Zhang, Xinzheng; Rupp, Romano A; Xu, Jingjun

    2012-01-01

    Ultraviolet (UV) light has a potent effect on biological organisms. Hemoglobin, an oxygen-transport protein, plays an irreplaceable role in sustaining life of all vertebrates. In this study we scrutinize the effects of ultraviolet irradiation (UVI) as well as visible irradiation on the fluorescence characteristics of bovine hemoglobin (BHb) in vitro. Data show that UVI results in fluorescence enhancement of BHb in a dose-dependent manner. Furthermore, UVI-induced fluorescence enhancement is significantly increased when BHb is pretreated with hydrogen peroxide (H(2)O(2)), a type of reactive oxygen species (ROS). Meanwhile, The water-soluble antioxidant vitamin C suppresses this UVI-induced fluorescence enhancement. In contrast, green light irradiation does not lead to fluorescence enhancement of BHb no matter whether H(2)O(2) is acting on the BHb solution or not. Taken together, these results indicate that catalysis of ROS and UVI-dependent irradiation play two key roles in the process of UVI-induced fluorescence enhancement of BHb.

  17. Toward enhanced hydrogen generation from water using oxygen permeating LCF membranes.

    PubMed

    Wu, Xiao-Yu; Chang, Le; Uddi, Mruthunjaya; Kirchen, Patrick; Ghoniem, Ahmed F

    2015-04-21

    Hydrogen production from water thermolysis can be enhanced by the use of perovskite-type mixed ionic and electronic conducting (MIEC) membranes, through which oxygen permeation is driven by a chemical potential gradient. In this work, water thermolysis experiments were performed using 0.9 mm thick La0.9Ca0.1FeO3-δ (LCF-91) perovskite membranes at 990 °C in a lab-scale button-cell reactor. We examined the effects of the operating conditions such as the gas species concentrations and flow rates on the feed and sweep sides on the water thermolysis rate and oxygen flux. A single step reaction mechanism is proposed for surface reactions, and three-resistance permeation models are derived. Results show that water thermolysis is facilitated by the LCF-91 membrane especially when a fuel is added to the sweep gas. Increasing the gas flow rate and water concentration on the feed side or the hydrogen concentration on the sweep side enhances the hydrogen production rate. In this work, hydrogen is used as the fuel by construction, so that a single-step surface reaction mechanism can be developed and water thermolysis rate parameters can be derived. Both surface reaction rate parameters for oxygen incorporation/dissociation and hydrogen-oxygen reactions are fitted at 990 °C. We compare the oxygen fluxes in water thermolysis and air separation experiments, and identify different limiting steps in the processes involving various oxygen sources and sweep gases for this 0.9 mm thick LCF-91 membrane. In the air feed-inert sweep case, the bulk diffusion and sweep side surface reaction are the two limiting steps. In the water feed-inert sweep case, surface reaction on the feed side dominates the oxygen permeation process. Yet in the water feed-fuel sweep case, surface reactions on both the feed and sweep sides are rate determining when hydrogen concentration in the sweep side is in the range of 1-5 vol%. Furthermore, long term studies show that the surface morphology changes and

  18. Simulation study of dose enhancement in a cell due to nearby carbon and oxygen in particle radiotherapy

    NASA Astrophysics Data System (ADS)

    Shin, Jae Ik; Cho, Ilsung; Cho, Sungho; Kim, Eun Ho; Song, Yongkeun; Jung, Won-Gyun; Yoo, SeungHoon; Shin, Dongho; Lee, Se Byeong; Yoon, Myonggeun; Incerti, S.´ebastian; Geso, Moshi; Rosenfeld, Anatoly B.

    2015-07-01

    The aim of this study is to investigate the dose-deposition enhancement due to alpha-particle irradiation in a cellular model by using the carbon and the oxygen chemical compositions. A simulation study was performed to study dose enhancement due to carbon and oxygen for a human cell where the Geant4 code used for alpha-particle irradiation of a cellular phantom. The characteristics of the dose enhancements based on the concentrations of carbon and oxygen in the nucleus and cytoplasm by the alpha-particle radiation was investigated and was compared with those obtained by gold and gadolinium. The results showed that both the carbon- and the oxygen-induced dose enhancements were more effective than those of gold and gadolinium. We found that the dose enhancement effect was more dominant in the nucleus than in the cytoplasm if the carbon or the oxygen were uniformly distributed in the whole cell. For the condition that the added chemical composition was inserted only into the cytoplasm, the effect of the dose enhancement in the nucleus was weak. We showed that high-stopping-power materials offer a more effective dose enhancement efficacy and suggest that carbon nanotubes and oxygenation are promising candidates for dose enhancement tools in particle therapy.

  19. Final report on the project entitled: Highly Preheated Combustion Air System with/without Oxygen Enrichment for Metal Processing Furnaces

    SciTech Connect

    Arvind Atreya

    2007-02-16

    This work develops and demonstrates a laboratory-scale high temperature natural gas furnace that can operate with/without oxygen enrichment to significantly improve energy efficiency and reduce emissions. The laboratory-scale is 5ft in diameter & 8ft tall. This furnace was constructed and tested. This report demonstrates the efficiency and pollutant prevention capabilities of this test furnace. The project also developed optical detection technology to control the furnace output.

  20. Sandwich-like PdO/CeO2 nanosheet@HZSM-5 membrane hybrid composite for methane combustion: self-redispersion, sintering-resistance and oxygen, water-tolerance

    NASA Astrophysics Data System (ADS)

    Dai, Qiguang; Bai, Shuxing; Lou, Yang; Wang, Xingyi; Guo, Yun; Lu, Guanzhong

    2016-05-01

    PdO/CeO2 nanosheets encapsulated by a monolayer of a continuous and dense HZSM-5 zeolite membrane were prepared by a facile in situ hydrothermal growth process and used as a highly efficient and thermally stable catalyst for methane combustion. Uncoated PdO/CeO2 suffered severe sintering at high temperature or high oxygen concentration. However, the encapsulation of HZSM-5 significantly improved sintering resistance by the suppressing effects of the HZSM-5 coating for the agglomeration of PdOx nanoparticles, resulting in the outstanding thermal stability of PdO/CeO2. Furthermore, the synthesized hybrid materials also exhibited good oxygen- and water-tolerance for methane combustion due to the oxygen or water barrier. In addition, a reactivation behavior was observed due to the self-redispersion of PdOx on CeO2 nanosheets in the reaction atmosphere at high temperature.PdO/CeO2 nanosheets encapsulated by a monolayer of a continuous and dense HZSM-5 zeolite membrane were prepared by a facile in situ hydrothermal growth process and used as a highly efficient and thermally stable catalyst for methane combustion. Uncoated PdO/CeO2 suffered severe sintering at high temperature or high oxygen concentration. However, the encapsulation of HZSM-5 significantly improved sintering resistance by the suppressing effects of the HZSM-5 coating for the agglomeration of PdOx nanoparticles, resulting in the outstanding thermal stability of PdO/CeO2. Furthermore, the synthesized hybrid materials also exhibited good oxygen- and water-tolerance for methane combustion due to the oxygen or water barrier. In addition, a reactivation behavior was observed due to the self-redispersion of PdOx on CeO2 nanosheets in the reaction atmosphere at high temperature. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01800a

  1. Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries

    PubMed Central

    Oh, Dahyun; Qi, Jifa; Lu, Yi-Chun; Zhang, Yong; Shao-Horn, Yang; Belcher, Angela M.

    2014-01-01

    Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by 2–3 times that of lithium-ion cells. Recent studies have focused on finding stable electrolytes to address poor cycling capability and improve practical limitations of current lithium-oxygen batteries. In this study, the catalyst electrode, where discharge products are deposited and decomposed, was investigated since it plays a critical role in the operation of rechargeable lithium-oxygen batteries. Here we report the electrode design principle to improve specific capacity and cycling performance of lithium-oxygen batteries by utilizing high efficiency nanocatalysts assembled by M13 virus with earth abundant elements, such as manganese oxides. By incorporating only 3–5 wt % of palladium nanoparticles in the electrode, this hybrid nanocatalyst achieves 13,350 mAh g−1c (7,340 mAh g−1c+catalyst) of specific capacity at 0.4 A g−1c and a stable cycle life up to 50 cycles (4,000 mAh g−1c, 400 mAh g−1c+catalyst) at 1 A g−1c. PMID:24220635

  2. Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries

    NASA Astrophysics Data System (ADS)

    Oh, Dahyun; Qi, Jifa; Lu, Yi-Chun; Zhang, Yong; Shao-Horn, Yang; Belcher, Angela M.

    2013-11-01

    Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by two to three times that of lithium ion cells. Recent studies have focused on finding stable electrolytes to address poor cycling capability and improve practical limitations of current lithium-oxygen batteries. In this study, the catalyst electrode, where discharge products are deposited and decomposed, was investigated as it has a critical role in the operation of rechargeable lithium-oxygen batteries. Here we report the electrode design principle to improve specific capacity and cycling performance of lithium-oxygen batteries by utilizing high-efficiency nanocatalysts assembled by M13 virus with earth-abundant elements such as manganese oxides. By incorporating only 3-5 wt% of palladium nanoparticles in the electrode, this hybrid nanocatalyst achieves 13,350 mAh g-1c (7,340 mAh g-1c+catalyst) of specific capacity at 0.4 A g-1c and a stable cycle life up to 50 cycles (4,000 mAh g-1c, 400 mAh g-1c+catalyst) at 1 A g-1c.

  3. Enhanced Photoelectrocatalytic Reduction of Oxygen Using Au@TiO2 Plasmonic Film.

    PubMed

    Guo, Limin; Liang, Kun; Marcus, Kyle; Li, Zhao; Zhou, Le; Mani, Prabhu Doss; Chen, Hao; Shen, Chen; Dong, Yajie; Zhai, Lei; Coffey, Kevin R; Orlovskaya, Nina; Sohn, Yong-Ho; Yang, Yang

    2016-12-28

    Novel Au@TiO2 plasmonic films were fabricated by individually placing Au nanoparticles into TiO2 nanocavity arrays through a sputtering and dewetting process. These discrete Au nanoparticles in TiO2 nanocavities showed strong visible-light absorption due to the plasmonic resonance. Photoelectrochemical studies demonstrated that the developed Au@TiO2 plasmonic films exhibited significantly enhanced catalytic activities toward oxygen reduction reactions with an onset potential of 0.92 V (vs reversible hydrogen electrode), electron transfer number of 3.94, and limiting current density of 5.2 mA cm(-2). A superior ORR activity of 310 mA mg(-1) is achieved using low Au loading mass. The isolated Au nanoparticle size remarkably affected the catalytic activities of Au@TiO2, and TiO2 coated with 5 nm Au (Au5@TiO2) exhibited the best catalytic function to reduce oxygen. The plasmon-enhanced reductive activity is attributed to the surface plasmonic resonance of isolated Au nanoparticles in TiO2 nanocavities and suppressed electron recombination. This work provides comprehensive understanding of a novel plasmonic system using isolated noble metals into nanostructured semiconductor films as a potential alternative catalyst for oxygen reduction reaction.

  4. The enhancement of oxygen sensitivity of ZnO macropore film by functionalizing with azo pigment.

    PubMed

    Peng, Liang; Zhai, Jiali; Wang, Dejun; Zhang, Yu; Zhao, Qidong; Wang, Ping; Pang, Shan; Fan, Zhiyong; Xie, Tengfeng

    2009-06-01

    Azo-ZnO hybrid films were prepared by functionalizing the ZnO macropore films with azo pigment (1,1'-(biphenyl-4,4'-diylbis(diazene-2,1-diyl))dinaphthalen-2-ol). Scanning electronic microscopy, current-voltage, UV-Vis absorption spectroscopy and Kelvin probe were used to characterize these films. The oxygen sensing characteristics of hybrid films and pure ZnO film were measured under the irradiation of UV light. The results show that the sensitivity of hybrid film is about 500 times higher than that of pure ZnO film. The high sensitivity to oxygen of hybrid films is mainly attributed to the increasing of the photo-generated electron concentration. Enhanced photo-induced charge separation after functionalization is confirmed by the pattern of transient photovoltage. Our results demonstrate that the functionalization with azo pigment is a promising approach to enhance the oxygen sensitivity of ZnO under the irradiation of UV light.

  5. Enhanced Bifunctional Oxygen Catalysis in Strained LaNiO3 Perovskites

    DOE PAGES

    Petrie, Jonathan R.; Cooper, Valentino R.; Freeland, John W.; ...

    2016-02-11

    Strain is known to greatly influence low-temperature oxygen electrocatalysis on noble metal films, leading to significant enhancements in bifunctional activity essential for fuel cells and metal-air batteries. Still, its catalytic impact on transition-metal oxide thin films, such as perovskites, is not widely understood. Here, we epitaxially strain the conducting perovskite LaNiO3 to systematically determine its influence on both the oxygen reduction and oxygen evolution reaction. Uniquely, we found that compressive strain could significantly enhance both reactions, yielding a bifunctional catalyst that surpasses the performance of noble metals such as Pt. We attribute the improved bifunctionality to strain-induced splitting of themore » eg orbitals, which can customize orbital asymmetry at the surface. Lastly, analogous to strain-induced shifts in the d-band center of noble metals relative to the Fermi level, such splitting can dramatically affect catalytic activity in this perovskite and other potentially more active oxides.« less

  6. Enhanced Bifunctional Oxygen Catalysis in Strained LaNiO3 Perovskites

    SciTech Connect

    Petrie, Jonathan R.; Cooper, Valentino R.; Freeland, John W.; Meyer, Tricia L.; Zhang, Zhiyong; Lutterman, Daniel A.; Lee, Ho Nyung

    2016-02-11

    Strain is known to greatly influence low-temperature oxygen electrocatalysis on noble metal films, leading to significant enhancements in bifunctional activity essential for fuel cells and metal-air batteries. Still, its catalytic impact on transition-metal oxide thin films, such as perovskites, is not widely understood. Here, we epitaxially strain the conducting perovskite LaNiO3 to systematically determine its influence on both the oxygen reduction and oxygen evolution reaction. Uniquely, we found that compressive strain could significantly enhance both reactions, yielding a bifunctional catalyst that surpasses the performance of noble metals such as Pt. We attribute the improved bifunctionality to strain-induced splitting of the eg orbitals, which can customize orbital asymmetry at the surface. Lastly, analogous to strain-induced shifts in the d-band center of noble metals relative to the Fermi level, such splitting can dramatically affect catalytic activity in this perovskite and other potentially more active oxides.

  7. Enhancing oxygen reduction reaction activity of Pt-shelled catalysts via subsurface alloying.

    PubMed

    Cheng, Daojian; Qiu, Xiangguo; Yu, Haiyan

    2014-10-14

    Despite remarkable efforts have been put into the field of Pt-shelled catalysts containing an atomically thin Pt surface layer for the oxygen reduction reaction (ORR) in the last decade, further development of new Pt-shelled catalysts is still necessary. Here, a new set of Pt-shelled catalysts by subsurface alloying with early transition metals such as Mn and Fe is predicted to be a good candidate for the ORR by using density functional theory (DFT) calculations. Trends in oxygen reduction activity of Pt-alloy catalysts are determined with calculations of oxygen binding by using the slab and cluster models. It is found that the subsurface alloys by the incorporation of submonolayer M (M = Mn and Fe) into Pt(111) in the slab model result in the enhancement of ORR activity, compared with the well-known Pt(111)-skin-M, pure Pt, and Pt3M alloy catalysts. For the cluster model, the Pt12Mn and Pt12Fe clusters are also found to be the optimal catalysts for the ORR. It is expected that this work can open up new opportunities for enhancing the ORR activity of Pt-alloy catalysts by subsurface alloying.

  8. Cathodic current enhancement via manganese and oxygen related reactions in marine biofilms

    NASA Astrophysics Data System (ADS)

    Strom, Matthew James

    Corrosion is a threat that has economic, and environmental impacts worldwide. Many types of corrosive attack are the subject of ongoing research. One of these areas of research is microbiologically influenced corrosion, which is the enhancement and/or initiation of corrosion events caused by microorganisms. It is well known that colonies of microorganisms can enhance cathodic currents through biofilm formation. The aim of the present work was to elucidate the role of manganese in enhancing cathodic currents in the presence of biofilms. Repeated polarizations conducted in Delaware Bay waters, on biofilm coated Cr identified potentially sustainable reduction reactions. The reduction of MnO2 and the enhancement of the oxygen reduction reaction (ORR) were proven to be factors that influence cathodic current enhancement. The removal of ambient oxygen during polarizations resulted in a shutdown of cathodic current enhancement. These field data led to an exploration of the synergistic relationship between MnO2 and the ORR. Laboratory studies of the catalysis of peroxide disproportionation by MnO2 were monitored using a hanging mercury drop electrode. Experiments were run at an ambient sweater pH of 8 and pH 9, which simulated the near-surface conditions typical of cathodes immersed in seawater. Rapid reoxidation at the more basic pH was shown to allow manganese to behave as a persistent catalyst under the typical electrochemical surface conditions of a cathode. As a result a mechanism for ORR enhancement by manganese was proposed as a unique mechanism for cathodic current enhancement in biofilms. A separate field study of Delaware biofilms on stainless steel coupled to a sacrificial Al anode was carried out to identify the ORR enhancement mechanism and sustainable redox reactions at the cathode. Chemical treatments of glutaraldehyde and formaldoxime were applied to cathodes with biofilms to distinguish between enzymatic and MnO2 related ORR enhancement. The results ruled

  9. Root Effect Haemoglobins in Fish May Greatly Enhance General Oxygen Delivery Relative to Other Vertebrates

    PubMed Central

    Rummer, Jodie L.; Brauner, Colin J.

    2015-01-01

    The teleost fishes represent over half of all extant vertebrates; they occupy nearly every body of water and in doing so, occupy a diverse array of environmental conditions. We propose that their success is related to a unique oxygen (O2) transport system involving their extremely pH-sensitive haemoglobin (Hb). A reduction in pH reduces both Hb-O2 affinity (Bohr effect) and carrying capacity (Root effect). This, combined with a large arterial-venous pH change (ΔpHa-v) relative to other vertebrates, may greatly enhance tissue oxygen delivery in teleosts (e.g., rainbow trout) during stress, beyond that in mammals (e.g., human). We generated oxygen equilibrium curves (OECs) at five different CO2 tensions for rainbow trout and determined that, when Hb-O2 saturation is 50% or greater, the change in oxygen partial pressure (ΔPO2) associated with ΔpHa-v can exceed that of the mammalian Bohr effect by at least 3-fold, but as much as 21-fold. Using known ΔpHa-v and assuming a constant arterial-venous PO2 difference (Pa-vO2), Root effect Hbs can enhance O2 release to the tissues by 73.5% in trout; whereas, the Bohr effect alone is responsible for enhancing O2 release by only 1.3% in humans. Disequilibrium states are likely operational in teleosts in vivo, and therefore the ΔpHa-v, and thus enhancement of O2 delivery, could be even larger. Modeling with known Pa-vO2 in fish during exercise and hypoxia indicates that O2 release from the Hb and therefore potentially tissue O2 delivery may double during exercise and triple during some levels of hypoxia. These characteristics may be central to performance of athletic fish species such as salmonids, but may indicate that general tissue oxygen delivery may have been the incipient function of Root effect Hbs in fish, a trait strongly associated with the adaptive radiation of teleosts. PMID:26436414

  10. Communication: Enhanced oxygen reduction reaction and its underlying mechanism in Pd-Ir-Co trimetallic alloys

    SciTech Connect

    Ham, Hyung Chul; Hwang, Gyeong S.; Manogaran, Dhivya; Lee, Kang Hee; Jin, Seon-ah; You, Dae Jong; Pak, Chanho; Kwon, Kyungjung

    2013-11-28

    Based on a combined density functional theory and experimental study, we present that the electrochemical activity of Pd{sub 3}Co alloy catalysts toward oxygen reduction reaction (ORR) can be enhanced by adding a small amount of Ir. While Ir tends to favorably exist in the subsurface layers, the underlying Ir atoms are found to cause a substantial modification in the surface electronic structure. As a consequence, we find that the activation barriers of O/OH hydrogenation reactions are noticeably lowered, which would be mainly responsible for the enhanced ORR activity. Furthermore, our study suggests that the presence of Ir in the near-surface region can suppress Co out-diffusion from the Pd{sub 3}Co substrate, thereby improving the durability of Pd-Ir-Co catalysts. We also discuss the relative roles played by Ir and Co in enhancing the ORR activity relative to monometallic Pd catalysts.

  11. Ex Vivo Machine Perfusion in CTA with a Novel Oxygen Carrier System to Enhance Graft Preservation and Immunologic Outcomes

    DTIC Science & Technology

    2014-10-01

    combination with a newly developed hemoglobin based oxygen carrier (HBOC) solution under subnormothermic (21°C) conditions as a way to enhance organ...static preservation, hemoglobin oxygen carrier solutions, vascularized composite allotransplants, ischemia/reperfusion, superior epigastric artery...Assist Liver Device (OALD) (Figure 8) and the VIR-1 solution, which contains a hemoglobin -based oxygen carrier and BMPS mixed 1:3 ratio, respectively

  12. Oxygen and relative humidity monitoring with films tailored for enhanced photoluminescence

    SciTech Connect

    Cui, Weipan; Liu, Rui; Manna, Eeshita; Park, Joong -Mok; Fungura, Fadzai; Shinar, Joseph; Shinar, Ruth

    2014-10-31

    In this study, approaches to generate porous or doped sensing films, which significantly enhance the photoluminescence (PL) of oxygen optical sensors, and thus improve the signal-to-noise (S/N) ratio, are presented. Tailored films, which enable monitoring the relative humidity (RH) as well, are also presented. Effective porous structures, in which the O2-sensitive dye Pt octaethylporphyrin (PtOEP) or the Pd analog PdOEP was embedded, were realized by first generating blend films of polyethylene glycol (PEG) with polystyrene (PS) or with ethyl cellulose (EC), and then immersing the dried films in water to remove the water-soluble PEG. This approach creates pores (voids) in the sensing films. The dielectric contrast between the films’ constituents and the voids increases photon scattering, which in turn increases the optical path of the excitation light within the film, and hence light absorption by the dye, and its PL. Optimized sensing films with a PEG:PS ratio of 1:4 (PEG’s molecular weight Mw ~8000) led to ~4.4× enhancement in the PL (in comparison to PS films). Lower Mw ~200 PEG with a PEG:EC ratio of 1:1 led to a PL enhancement of ~4.7×. Film-dependent PL enhancements were observed at all oxygen concentrations. The strong PL enhancement enables (i) using lower dye (luminophore) concentrations, (ii) reducing power consumption and enhancing the sensor’s operational lifetime when using organic light emitting diodes (OLEDs) as excitation sources, (iii) improving performance when using compact photodetectors with no internal gain, and (iv) reliably extending the dynamic range.

  13. Oxygen and relative humidity monitoring with films tailored for enhanced photoluminescence

    DOE PAGES

    Cui, Weipan; Liu, Rui; Manna, Eeshita; ...

    2014-10-31

    In this study, approaches to generate porous or doped sensing films, which significantly enhance the photoluminescence (PL) of oxygen optical sensors, and thus improve the signal-to-noise (S/N) ratio, are presented. Tailored films, which enable monitoring the relative humidity (RH) as well, are also presented. Effective porous structures, in which the O2-sensitive dye Pt octaethylporphyrin (PtOEP) or the Pd analog PdOEP was embedded, were realized by first generating blend films of polyethylene glycol (PEG) with polystyrene (PS) or with ethyl cellulose (EC), and then immersing the dried films in water to remove the water-soluble PEG. This approach creates pores (voids) inmore » the sensing films. The dielectric contrast between the films’ constituents and the voids increases photon scattering, which in turn increases the optical path of the excitation light within the film, and hence light absorption by the dye, and its PL. Optimized sensing films with a PEG:PS ratio of 1:4 (PEG’s molecular weight Mw ~8000) led to ~4.4× enhancement in the PL (in comparison to PS films). Lower Mw ~200 PEG with a PEG:EC ratio of 1:1 led to a PL enhancement of ~4.7×. Film-dependent PL enhancements were observed at all oxygen concentrations. The strong PL enhancement enables (i) using lower dye (luminophore) concentrations, (ii) reducing power consumption and enhancing the sensor’s operational lifetime when using organic light emitting diodes (OLEDs) as excitation sources, (iii) improving performance when using compact photodetectors with no internal gain, and (iv) reliably extending the dynamic range.« less

  14. Promoted combustion of nine structural metals in high-pressure gaseous oxygen - A comparison of ranking methods

    NASA Technical Reports Server (NTRS)

    Steinberg, Theodore A.; Rucker, Michelle A.; Beeson, Harold D.

    1989-01-01

    The 316, 321, 440C, and 17-4 PH stainless steels, as well as Inconel 600, Inconel 718, Waspaloy, Monel 400, and Al 2219, have been evaluated for relative nonflammability in a high-pressure oxygen environment with a view to the comparative advantages of four different flammability-ranking methods. The effects of changes in test pressure, sample diameter, promoter type, and sample configuration on ranking method results are evaluated; ranking methods employing velocity as the primary ranking criterion are limited by diameter effects, while those which use extinguishing pressure are nonselective for metals with similar flammabilities.

  15. Out-of-Plane Coordinated Porphyrin Nanotubes with Enhanced Singlet Oxygen Generation Efficiency

    PubMed Central

    Zhao, Qiang; Wang, Yao; Xu, Yanshuang; Yan, Yun; Huang, Jianbin

    2016-01-01

    A supramolecular porphyrin nanotube displaying J-aggregation feature was constructed by out-of-plane coordinated bismuth-porphyrin. Significantly, compared to traditional J-aggregated porphyrin suffering from fluorescence and singlet oxygen quenching, the nanotube exhibits excellent bio-imaging ability and enhanced production efficiency of singlet oxygen. The out-of-plane structure of bismuth to porphyrin makes the aggregation an appropriate material for theranostics. Furthermore, it is also a potential radio-therapeutic drug owing to the presence of radio-active bismuth. Thus, the self-assembly of out-of-plane coordinated porphyrin can be a facile approach toward effective therapy of tumors and other diseases. PMID:27527403

  16. Enhanced nonlinear optical properties of oxygen deficient lead-niobium-germanate film glasses

    NASA Astrophysics Data System (ADS)

    Gonzalo, J.; Fernandez, H.; Solis, J.; Munoz-Martin, D.; Fernandez-Navarro, J. M.; Afonso, C. N.; Fierro, J. L. G.

    2007-06-01

    The third order nonlinear optical properties of oxygen deficient lead-niobium-germanate film glasses with heavy metal contents beyond that of the bulk glass formation region have been investigated. Values of the nonlinear third order optical susceptibility up to /χ(3)/≈1.8×10-11esu have been measured by degenerate four wave mixing at 800nm in films having large heavy metal fractions (0.93). The fast buildup and decay times (≈130fs) of the nonlinear response confirm its nonresonant character. The partial reduction of Nb5+ to Nb4+ evidenced by x-ray photoelectron spectroscopy, which is associated with the oxygen deficiency, appears to be responsible for the strong enhancement of /χ(3)/.

  17. Global deep ocean oxygenation by enhanced ventilation in the Southern Ocean under long-term global warming

    NASA Astrophysics Data System (ADS)

    Yamamoto, A.; Abe-Ouchi, A.; Shigemitsu, M.; Oka, A.; Takahashi, K.; Ohgaito, R.; Yamanaka, Y.

    2015-10-01

    Global warming is expected to decrease ocean oxygen concentrations by less solubility of surface ocean and change in ocean circulation. The associated expansion of the oxygen minimum zone would have adverse impacts on marine organisms and ocean biogeochemical cycles. Oxygen reduction is expected to persist for a thousand years or more, even after atmospheric carbon dioxide stops rising. However, long-term changes in ocean oxygen and circulation are still unclear. Here we simulate multimillennium changes in ocean circulation and oxygen under doubling and quadrupling of atmospheric carbon dioxide, using a fully coupled atmosphere-ocean general circulation model and an offline biogeochemical model. In the first 500 years, global oxygen concentration decreases, consistent with previous studies. Thereafter, however, the oxygen concentration in the deep ocean globally recovers and overshoots at the end of the simulations, despite surface oxygen decrease and weaker Atlantic meridional overturning circulation. This is because, after the initial cessation, the recovery and overshooting of deep ocean convection in the Weddell Sea enhance ventilation and supply oxygen-rich surface waters to deep ocean. Another contributor to deep ocean oxygenation is seawater warming, which reduces the export production and shifts the organic matter remineralization to the upper water column. Our results indicate that the change in ocean circulation in the Southern Ocean potentially drives millennial-scale oxygenation in deep ocean, which is opposite to the centennial-scale global oxygen reduction and general expectation.

  18. Turbulent combustion

    SciTech Connect

    Talbot, L.; Cheng, R.K.

    1993-12-01

    Turbulent combustion is the dominant process in heat and power generating systems. Its most significant aspect is to enhance the burning rate and volumetric power density. Turbulent mixing, however, also influences the chemical rates and has a direct effect on the formation of pollutants, flame ignition and extinction. Therefore, research and development of modern combustion systems for power generation, waste incineration and material synthesis must rely on a fundamental understanding of the physical effect of turbulence on combustion to develop theoretical models that can be used as design tools. The overall objective of this program is to investigate, primarily experimentally, the interaction and coupling between turbulence and combustion. These processes are complex and are characterized by scalar and velocity fluctuations with time and length scales spanning several orders of magnitude. They are also influenced by the so-called {open_quotes}field{close_quotes} effects associated with the characteristics of the flow and burner geometries. The authors` approach is to gain a fundamental understanding by investigating idealized laboratory flames. Laboratory flames are amenable to detailed interrogation by laser diagnostics and their flow geometries are chosen to simplify numerical modeling and simulations and to facilitate comparison between experiments and theory.

  19. Metal Combustion In High Pressure Oxygen Atmosphere: Detailed Observation Of Burning Region Behavior By Using High Speed Photography

    NASA Astrophysics Data System (ADS)

    Sato, Kenji; Sato, Yoshiko; Tsuno, Takao; Nakamura, Yoshio; Hirano, Toshisuke; Sato, Jun'ichi

    1983-03-01

    Detailed process of upward fire spread along a mild steel cylinder in high pressure oxygen has been studied by using high speed photography. Fire spread experiments were conducted in a cylindrical, high pressure oxygen chamber of a capacity of about 2.5x107 mm3. The movement of a molten mass attached to the bottom end of a burning steel cylinder and that of a molten mass droplet detached from the bottom end were recorded by a 16 mm or 35 mm high speed cinecamera and analyzed. By analyzing the oscillatory behavior of the molten mass droplet, its main component was inferred to be iron oxide. The local spread rate fluctuation was observed during a period of the overall cyclic behavior. Based on the location of the observed high luminosity region and surface flow of the molten mass, convection was inferred to be a dominant mode of heat transfer at the molten-solid boundary and the fluctuation of the local spread rate was supposed to be attributable to the nonuniformity of the convective heat transfer at the molten-solid boundary.

  20. Enhanced photoluminescence in air-suspended carbon nanotubes by oxygen doping

    NASA Astrophysics Data System (ADS)

    Chen, Jihan; Dhall, Rohan; Hou, Bingya; Yang, Sisi; Wang, Bo; Kang, Daejing; Cronin, Stephen B.

    2016-10-01

    We report photoluminescence (PL) imaging and spectroscopy of air-suspended carbon nanotubes (CNTs) before and after exposure to a brief (20 s) UV/ozone treatment. These spectra show enhanced PL intensities in 10 out of 11 nanotubes that were measured, by as much as 5-fold. This enhancement in the luminescence efficiency is caused by oxygen defects which trap excitons. We also observe an average 3-fold increase in the D-band Raman intensity further indicating the creation of defects. Previous demonstrations of oxygen doping have been carried out on surfactant-coated carbon nanotubes dissolved in solution, thus requiring substantial longer ozone/UV exposure times (˜15 h). Here, the ozone treatment is more efficient because of the surface exposure of the air-suspended CNTs. In addition to enhanced PL intensities, we observe narrowing of the emission linewidth by 3-10 nm. This ability to control and engineer defects in CNTs is important for realizing several optoelectronic applications such as light-emitting diodes and single photon sources.

  1. Titanium Dioxide Nanorods with Hydrogenated Oxygen Vacancies for Enhanced Solar Water Splitting.

    PubMed

    Sun, Bo; Shi, Tielin; Tan, Xianhua; Liu, Zhiyong; Wu, Youni; Liao, Guanglan

    2016-06-01

    We demonstrate that moderate hydrogen annealing is a simple and effective approach to substantially improve the photocatalytic activity of TiO2 nanorods via increasing oxygen vacancies in outer layer. Hydrogenated TiO2 nanorods are obtained by annealing in hydrogen atmosphere at various temperatures ranging from 200 degrees C to 350 degrees C. TEM images directly illustrate the disordered layer on the surface of nanorods induced by hydrogen annealing. The photoelectrochemical measurements reveal that the photocurrent is improved first as the temperature increases and reaches to the maximum value at an appropriate temperature (250 degrees C), corresponding to about 50% enhancement compared to the pristine TiO2. Incident photon-to-electron conversion efficiency spectra reveal that the photocurrent improvement is mainly attributed to the enhanced photocatalytic activity of TiO2 in ultraviolet region. Mott-Schottky plots further betray that hydrogen annealing can significantly enhance the electric conductivity, via increasing the oxygen vacancies density in the outer layer. In addition, time-dependent measurements indicate the hydrogenated TiO2 nanorods possess excellent chemical stability. Thus, we believe the hydrogenated TiO2 nanorods would be a promising candidate for photoanode in solar water splitting.

  2. An analysis of combustion studies in shock expansion tunnels and reflected shock tunnels

    NASA Technical Reports Server (NTRS)

    Jachimowski, Casimir J.

    1992-01-01

    The effect of initial nonequilibrium dissociated air constituents on the combustion of hydrogen in high-speed flows for a simulated Mach 17 flight condition was investigated by analyzing the results of comparative combustion experiments performed in a reflected shock tunnel test gas and in a shock expansion tunnel test gas. The results were analyzed and interpreted with a one-dimensional quasi-three-stream combustor code that includes finite rate combustion chemistry. The results of this study indicate that the combustion process is kinetically controlled in the experiments in both tunnels and the presence of the nonequilibrium partially dissociated oxygen in the reflected shock tunnel enhances the combustion. Methods of compensating for the effect of dissociated oxygen are discussed.

  3. Enhancing oxygen transport through Mixed-Ionic-and-Electronic-Conducting ceramic membranes

    NASA Astrophysics Data System (ADS)

    Yu, Anthony S.

    Ceramic membranes based on Mixed-Ionic-and-Electronic-Conducting (MIEC) oxides are capable of separating oxygen from air in the presence of an oxygen partial-pressure gradient. These MIEC membranes show great promise for oxygen consuming industrial processes, such as the production of syngas from steam reforming of natural gas (SRM), as well as for electricity generation in Solid Oxide Fuel Cells (SOFC). For both applications, the overall performance is dictated by the rate of oxygen transport across the membrane. Oxygen transport across MIEC membranes is composed of a bulk oxygen-ion diffusion process and surface processes, such as surface reactions and adsorption/desorption of gaseous reactants/products. The main goal of this thesis was to determine which process is rate-limiting in order to significantly enhance the overall rate of oxygen transport in MIEC membrane systems. The rate-limiting step was determined by evaluating the total resistance to oxygen transfer, Rtot. Rtot is the sum of a bulk diffusion resistance in the membrane itself, Rb, and interfacial loss components, Rs. Rb is a function of the membrane's ionic conductivity and thickness, while Rs arises primarily from slow surface-exchange kinetics that cause the P(O2) at the surfaces of the membrane to differ from the P(O 2) in the adjacent gas phases. Rtot can be calculated from the Nernst potential across the membrane and the measured oxygen flux. The rate-limiting process can be determined by evaluating the relative contributions of the various losses, Rs and Rb, to Rtot. Using this method, this thesis demonstrates that for most membrane systems, Rs is the dominating factor. In the development of membrane systems with high oxygen transport rates, thin membranes with high ionic conductivities are required to achieve fast bulk oxygen-ion diffusion. However, as membrane thickness is decreased, surface reaction kinetics become more important in determining the overall transport rate. The two

  4. Oxygen and hydrogen peroxide enhance light-induced carotenoid synthesis in Neurospora crassa.

    PubMed

    Iigusa, Hideo; Yoshida, Yusuke; Hasunuma, Kohji

    2005-07-18

    Previously, we found that intracellular reactive oxygen species (ROS) affect photomorphogenesis in Neurospora crassa. In this study, we investigated the physiological roles of ROS in the response to light and found that the exposure of mycelia to air was important for the light-induced carotenogenesis. Mycelia treated with a high concentration of O(2) gas and H(2)O(2) to release ROS showed an enhancement of light-induced carotenoid accumulation and the expression of gene related to light-inducible carotenogenesis. These results suggested that stimuli caused by the exposure of the mycelia to air containing O(2) gas triggered the light-induced carotenoid synthesis.

  5. TECHNOLOGY DEMONSTRATION SUMMARY: THE AMERICAN COMBUSTION PYRETRON THERMAL DESTRUCTION SYSTEM AT THE U.S. EPA'S COMBUSTION FACILITY

    EPA Science Inventory

    The American Combustion Pyretron Thermal Destruction System at the U.S. EPA's Combustion Research Facility. Under the auspices of the Superfund Innovative Technology Evaluation, or SITE, program, a critical assessment was made of the American Combustion Pyretron™ oxygen enha...

  6. Supersonic Inlet with Pylons Set and Star-Shaped Forebody for Mixing, Combustion and Thrust Enhancement

    NASA Technical Reports Server (NTRS)

    Gilinsky, M.; Gonor, A. L.; Khaikine, V. A.; Blankson, I. M.

    2003-01-01

    Two new approaches are discussed in this paper for application in the Scramjet inlet of an air-breathing propulsion system: 1) In the first approach, the pylon set is installed in the rectangular inlet near the cowl front edge. For a quasi-axisymmetric inlet, a similar set is installed along the Star-shaped forebody axis. This set contains 3 - 4 airfoil-shaped strips or cross-sectional rings depending on the type of inlet. The inlets: rectangular, axisymmetric or star-shaped, are located at different distances from the forebody. Fuel injection takes place through these pylons, which provides for uniform mixing downstream. The locations, sizes and angles of these pylons are very important for efficient application. Optimal values of geometrical parameters were determined from multi-parametric NSE-based numerical simulations of the laminar and turbulent external/internal flows. These simulations have shown significant benefits for mixing, combustion and thrust of the proposed approach by comparison with traditional well-known designs. Experimental tests will be conducted soon at the NASA LaRC and Institute of Mechanics at Moscow State University. Preliminary estimates are very promising.

  7. Phosphate enhances Fgf23 expression through reactive oxygen species in UMR-106 cells.

    PubMed

    Hori, Michiko; Kinoshita, Yuka; Taguchi, Manabu; Fukumoto, Seiji

    2016-03-01

    Fibroblast growth factor 23 (FGF23) has been shown to work as a phosphotropic hormone. Although FGF23 reduces the serum phosphate level, it has not been established that phosphate directly regulates FGF23 production. In this study, we investigated whether phosphate can enhance Fgf23 expression using the rat osteoblastic cell line UMR-106, which has been shown to express Fgf23 in response to 1,25-dihydroxyvitamin D [1,25(OH)2D]. Phosphate increased Fgf23 expression in a dose- and time-dependent manner in the presence of 1,25(OH)2D. Phosphate also increased Fgf23 promoter activity, but showed no effect on the half-life of Fgf23 messenger RNA. Phosphonoformic acid and PD98059, an inhibitor of MEK, inhibited the effects of phosphate on Fgf23 expression and promoter activity. In addition, phosphate enhanced production of reactive oxygen species (ROS) in UMR-106 cells, and hydrogen peroxide enhanced FGF23 production in a dose- and time-dependent manner. Hydrogen peroxide also enhanced Elk1 reporter activity, a target of the MEK-extracellular-signal-regulated kinase (ERK) pathway. Furthermore, the effect of phosphate on ROS production and Fgf23 expression was inhibited by apocynin, an inhibitor of NADPH oxidase. These results indicate that phosphate directly enhances Fgf23 transcription without affecting the stability of Fgf23 messenger RNA by stimulating NADPH-induced ROS production and the MEK-ERK pathway in UMR-106 cells.

  8. Shell-anchor-core structures for enhanced stability and catalytic oxygen reduction activity

    NASA Astrophysics Data System (ADS)

    Ramirez-Caballero, Gustavo E.; Hirunsit, Pussana; Balbuena, Perla B.

    2010-10-01

    Density functional theory is used to evaluate activity and stability properties of shell-anchor-core structures. The structures consist of a Pt surface monolayer and a composite core having an anchor bilayer where C atoms in the interstitial sites lock 3d metals in their locations, thus avoiding their surface segregation and posterior dissolution. The modified subsurface geometry induces less strain on the top surface, thus exerting a favorable effect on the surface catalytic activity where the adsorption strength of the oxygenated species becomes more moderate: weaker than on pure Pt(111) but stronger than on a Pt monolayer having a 3d metal subsurface. Here we analyze the effect of changing the nature of the 3d metal in the subsurface anchor bilayer, and we also test the use of a Pd monolayer instead of Pt on the surface. It is found that a subsurface constituted by two layers with an approximate composition of M2C (M=Fe, Ni, and Co) provides a barrier for the migration of subsurface core metal atoms to the surface. Consequently, an enhanced resistance against dissolution in parallel to improved oxygen reduction activity is expected, as given by the values of adsorption energies of reaction intermediates, delayed onset of water oxidation, and/or low coverage of oxygenated species at surface oxidation potentials.

  9. Amorphous nickel boride membrane on a platinum-nickel alloy surface for enhanced oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    He, Daping; Zhang, Libo; He, Dongsheng; Zhou, Gang; Lin, Yue; Deng, Zhaoxiang; Hong, Xun; Wu, Yuen; Chen, Chen; Li, Yadong

    2016-08-01

    The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum-nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum-nickel catalyst, and this composite catalyst composed of crystalline platinum-nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon.

  10. Chemically Driven Enhancement of Oxygen Reduction Electrocatalysis in Supported Perovskite Oxides.

    PubMed

    Lee, Daehee; Tan, Jeiwan; Chae, Keun Hwa; Jeong, Beomgyun; Soon, Aloysius; Ahn, Sung-Jin; Kim, Joosun; Moon, Jooho

    2017-01-05

    Perovskite oxides have the capacity to efficiently catalyze the oxygen reduction reaction (ORR), which is of fundamental importance for electrochemical energy conversion. While the perovskite catalysts have been generally utilized with a support, the role of the supports, regarded as inert toward the ORR, has been emphasized mostly in terms of the thermal stability of the catalyst system and as an ancillary transport channel for oxygen ions during the ORR. We demonstrate a novel approach to improving the catalytic activity of perovskite oxides for solid oxide fuel cells by controlling the oxygen-ion conducting oxide supports. Catalytic activities of (La0.8Sr0.2)0.95MnO3 perovskite thin-film placed on different oxide supports are characterized by electrochemical impedance spectroscopy and X-ray absorption spectroscopy. These analyses confirm that the strong atomic orbital interactions between the support and the perovskite catalyst enhance the surface exchange kinetics by ∼2.4 times, in turn, improving the overall ORR activity.

  11. Amorphous nickel boride membrane on a platinum–nickel alloy surface for enhanced oxygen reduction reaction

    PubMed Central

    He, Daping; Zhang, Libo; He, Dongsheng; Zhou, Gang; Lin, Yue; Deng, Zhaoxiang; Hong, Xun; Wu, Yuen; Chen, Chen; Li, Yadong

    2016-01-01

    The low activity of the oxygen reduction reaction in polymer electrolyte membrane fuel cells is a major barrier for electrocatalysis, and hence needs to be optimized. Tuning the surface electronic structure of platinum-based bimetallic alloys, a promising oxygen reduction reaction catalyst, plays a key role in controlling its interaction with reactants, and thus affects the efficiency. Here we report that a dealloying process can be utilized to experimentally fabricate the interface between dealloyed platinum–nickel alloy and amorphous nickel boride membrane. The coating membrane works as an electron acceptor to tune the surface electronic structure of the platinum–nickel catalyst, and this composite catalyst composed of crystalline platinum–nickel covered by amorphous nickel boride achieves a 27-times enhancement in mass activity relative to commercial platinum/carbon at 0.9 V for the oxygen reduction reaction performance. Moreover, this interactional effect between a crystalline surface and amorphous membrane can be readily generalized to facilitate the 3-times higher catalytic activity of commercial platinum/carbon. PMID:27503412

  12. Enhancement Effect of Noble Metals on Manganese Oxide for the Oxygen Evolution Reaction.

    PubMed

    Seitz, Linsey C; Hersbach, Thomas J P; Nordlund, Dennis; Jaramillo, Thomas F

    2015-10-15

    Developing improved catalysts for the oxygen evolution reaction (OER) is key to the advancement of a number of renewable energy technologies, including solar fuels production and metal air batteries. In this study, we employ electrochemical methods and synchrotron techniques to systematically investigate interactions between metal oxides and noble metals that lead to enhanced OER catalysis for water oxidation. In particular, we synthesize porous MnOx films together with nanoparticles of Au, Pd, Pt, or Ag and observe significant improvement in activity for the combined catalysts. Soft X-ray absorption spectroscopy (XAS) shows that increased activity correlates with increased Mn oxidation states to 4+ under OER conditions compared to bare MnOx, which exhibits minimal OER current and remains in a 3+ oxidation state. Thickness studies of bare MnOx films and of MnOx films deposited on Au nanoparticles reveal trends suggesting that the enhancement in activity arises from interfacial sites between Au and MnOx.

  13. The application of profluorescent nitroxides to detect reactive oxygen species derived from combustion-generated particulate matter: Cigarette smoke - A case study

    NASA Astrophysics Data System (ADS)

    Miljevic, B.; Fairfull-Smith, K. E.; Bottle, S. E.; Ristovski, Z. D.

    2010-06-01

    Reactive oxygen species (ROS) and related free radicals are considered to be key factors underpinning the various adverse health effects associated with exposure to ambient particulate matter. Therefore, measurement of ROS is a crucial factor for assessing the potential toxicity of particles. In this work, a novel profluorescent nitroxide, BPEAnit, was investigated as a probe for detecting particle-derived ROS. BPEAnit has a very low fluorescence emission due to inherent quenching by the nitroxide group, but upon radical trapping or redox activity, a strong fluorescence is observed. BPEAnit was tested for detection of ROS present in mainstream and sidestream cigarette smoke. In the case of mainstream cigarette smoke, there was a linear increase in fluorescence intensity with an increasing number of cigarette puffs, equivalent to an average of 101 nmol ROS per cigarette based on the number of moles of the probe reacted. Sidestream cigarette smoke sampled from an environmental chamber exposed BPEAnit to much lower concentrations of particles, but still resulted in a clearly detectible increase in fluorescence intensity with sampling time. It was calculated that the amount of ROS was equivalent to 50 ± 2 nmol per mg of particulate matter; however, this value decreased with ageing of the particles in the chamber. Overall, BPEAnit was shown to provide a sensitive response related to the oxidative capacity of the particulate matter. These findings present a good basis for employing the new BPEAnit probe for the investigation of particle-related ROS generated from cigarette smoke as well as from other combustion sources.

  14. Effect of hydrogen sulfide on chemical looping combustion of coal-derived synthesis gas over bentonite-supported metal-oxide oxygen carriers

    SciTech Connect

    Tian, H.J.; Simonyi, T.; Poston, J.; Siriwardane, R.

    2009-09-15

    The effect of hydrogen sulfide (H{sub 2}S) on the chemical looping combustion of coal-derived synthesis gas with bentonite-supported metal oxides - such as iron oxide, nickel oxide, manganese oxide, and copper oxide - was investigated by thermogravimetric analysis, mass spectrometry, and X-ray photoelectron spectroscopy (XPS). During the reaction with synthesis gas containing H{sub 2}S, metal-oxide oxygen carriers were first reduced by carbon monoxide and hydrogen, and then interacted with H{sub 2}S to form metal sulfide, which resulted in a weight gain during the reduction/sulfidation step. The reduced/sulfurized compounds could be regenerated to form sulfur dioxide and oxides during the oxidation reaction with air. The reduction/oxidation capacities of iron oxide and nickel oxide were not affected by the presence of H{sub 2}S, but both manganese oxide and copper oxide showed decreased reduction/oxidation capacities. However, the rates of reduction and oxidation decreased in the presence of H{sub 2}S for all four metal oxides.

  15. LES of Mild Combustion using Pareto-efficient Combustion Adaptation

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Evans, Michael; Ihme, Matthias

    2015-11-01

    Moderate or Intense Low-Oxygen Dilution (MILD) combustion is a combustion regime that provides opportunities for improved thermal efficiency and reduced pollutant emissions. In this study, large-eddy simulation is used to investigate the ignition, mixing, and stabilization of a jet flame in this kinetics-controlled combustion regime. The combustion process is modeled by a Pareto-efficient combustion (PEC) formulation that optimally combines reaction-transport and chemistry combustion models. In this approach, a three-stream flamelet/progress variable model is used as a computationally efficient description of equilibrated flame regions, and a finite-rate chemistry representation is employed to accurately represent the ignition behavior and flame stabilization. Through comparisons with experiments and simulations with single-regime combustion models, it will be shown that this Pareto-efficient combustion submodel assignment accurately captures important dynamics in complex turbulent flame configurations.

  16. Hydroxyl radical-PLIF measurements and accuracy investigation in high pressure gaseous hydrogen/gaseous oxygen combustion

    NASA Astrophysics Data System (ADS)

    Vaidyanathan, Aravind

    In-flow species concentration measurements in reacting flows at high pressures are needed both to improve the current understanding of the physical processes taking place and to validate predictive tools that are under development, for application to the design and optimization of a range of power plants from diesel to rocket engines. To date, non intrusive measurements have been based on calibrations determined from assumptions that were not sufficiently quantified to provide a clear understanding of the range of uncertainty associated with these measurements. The purpose of this work is to quantify the uncertainties associated with OH measurement in a oxygen-hydrogen system produced by a shear, coaxial injector typical of those used in rocket engines. Planar OH distributions are obtained providing instantaneous and averaged distribution that are required for both LES and RANS codes currently under development. This study has evaluated the uncertainties associated with OH measurement at 10, 27, 37 and 53 bar respectively. The total rms error for OH-PLIF measurements from eighteen different parameters was quantified and found as 21.9, 22.8, 22.5, and 22.9% at 10, 27, 37 and 53 bar respectively. These results are used by collaborators at Georgia Institute of Technology (LES), Pennsylvania State University (LES), University of Michigan (RANS) and NASA Marshall (RANS).

  17. CH4 combustion cycles at Pd/Al2O3--important role of support and oxygen access.

    PubMed

    Czekaj, Izabela; Kacprzak, Katarzyna A; Mantzaras, John

    2013-07-21

    This research is focused on the analysis of adsorbed CH4 intermediates at oxidized Pd9 nanoparticles supported on γ-alumina. From first-principle density functional theory calculations, several configurations, charge transfer and electronic density of states have been analyzed in order to determine feasible paths for the oxidation process. Methane oxidation cycles have been considered as a further step at differently oxidized Pd nanoparticles. For low oxidized Pd nanoparticles, activation of methane is observed, whereby hydrogen from methane is adsorbed at one oxygen atom. This reaction is exothermic with adsorption energy equal to -0.38 eV. In a subsequent step, desorption of two water molecules is observed. Additionally, a very interesting structural effect is evident, mainly Pd-carbide formation, which is also an exothermic reaction with an energy of -0.65 eV. Furthermore, oxidation of such carbidized Pd nanoparticles leads to CO2 formation, which is an endothermic reaction. Important result is that the support is involved in CO2 formation. A different mechanism of methane oxidation has been found for highly oxidized Pd nanoparticles. When the Pd nanoparticle is more strongly exposed to oxidative conditions, adsorption of methane is also possible, but it will proceed with carbonic acid production at the interface between Pd nanoparticles and support. However, this step is endothermic.

  18. Hydrogen sulfide can inhibit and enhance oxygenic photosynthesis in a cyanobacterium from sulfidic springs.

    PubMed

    Klatt, Judith M; Haas, Sebastian; Yilmaz, Pelin; de Beer, Dirk; Polerecky, Lubos

    2015-09-01

    We used microsensors to investigate the combinatory effect of hydrogen sulfide (H2 S) and light on oxygenic photosynthesis in biofilms formed by a cyanobacterium from sulfidic springs. We found that photosynthesis was both positively and negatively affected by H2 S: (i) H2 S accelerated the recovery of photosynthesis after prolonged exposure to darkness and anoxia. We suggest that this is possibly due to regulatory effects of H2 S on photosystem I components and/or on the Calvin cycle. (ii) H2 S concentrations of up to 210 μM temporarily enhanced the photosynthetic rates at low irradiance. Modelling showed that this enhancement is plausibly based on changes in the light-harvesting efficiency. (iii) Above a certain light-dependent concentration threshold H2 S also acted as an inhibitor. Intriguingly, this inhibition was not instant but occurred only after a specific time interval that decreased with increasing light intensity. That photosynthesis is most sensitive to inhibition at high light intensities suggests that H2 S inactivates an intermediate of the oxygen evolving complex that accumulates with increasing light intensity. We discuss the implications of these three effects of H2 S in the context of cyanobacterial photosynthesis under conditions with diurnally fluctuating light and H2 S concentrations, such as those occurring in microbial mats and biofilms.

  19. Improvement of islet engrafts by enhanced angiogenesis and microparticle-mediated oxygenation.

    PubMed

    Montazeri, Leila; Hojjati-Emami, Shahriar; Bonakdar, Shahin; Tahamtani, Yaser; Hajizadeh-Saffar, Ensiyeh; Noori-Keshtkar, Marjan; Najar-Asl, Mostafa; Ashtiani, Mohammad Kazemi; Baharvand, Hossein

    2016-05-01

    A major hindrance in islet transplantation as a feasible therapeutic approach for patients with type 1 diabetes is the insufficient oxygenation of the grafts, which results in cell death in portions of the implant. Here we address this limitation through the application of oxygen-generating microparticles (MP) and a fibrin-conjugated heparin/VEGF collagen scaffold to support cell survival by using a β cell line and pancreatic rat islets. MP are composed of a polyvinylpyrrolidone/hydrogen peroxide (PVP/H2O2) core and poly(D,L-lactide-co-glycolide) (PLGA) shell, along with immobilized catalase on the shell. The presence of MP is sufficient to reduce hypoxia-induced cell dysfunction and death for both cell types, resulting in localization of hypoxia-inducible factor (HIF-1α) into the cytoplasm and enhanced metabolic function. After co-transplantation of MP and a reduced islet mass (250 islet equivalents) within an angiogenic scaffold in the omental pouch of streptozotocin-induced diabetic nude mice, we have observed significantly promoted graft function as evidenced by improved blood glucose levels, body weight, glucose tolerance, serum C-peptide, and graft revascularization. These results suggest that the developed platform has great potential to enhance the efficacy for implants in cases where the cell dosage is critical for efficacy, such as islet transplantation and ischemic tissues.

  20. Oxygen stabilization induced enhancement in superconducting characteristics of high-Tc oxides

    NASA Technical Reports Server (NTRS)

    Wu, M. K.; Chen, J. T.; Huang, C. Y.

    1991-01-01

    In an attempt to enhance the electrical and mechanical properties of the high temperature superconducting oxides, high T(sub c) composites were prepared composed of the 123 compounds and AgO. The presence of extra oxygen due to the decomposition of AgO at high temperature is found to stabilize the superconducting 123 phase. Ag is found to serve as clean flux for grain growth and precipitates as pinning center. Consequently, almost two orders of magnitude enhancement in critical current densities were also observed in these composites. In addition, these composites also show much improvement in workability and shape formation. On the other hand, proper oxygen treatment of Y5Ba6Cu11Oy was found to possibly stabilize superconducting phase with T(sub c) near 250 K. I-V, ac susceptibility, and electrical resistivity measurements indicate the existence of this ultra high T(sub c) phase in this compound. Detailed structure, microstructure, electrical, magnetic and thermal studies of the superconducting composites and the ultra high T(sub c) compound are presented and discussed.

  1. Droplet Combustion Experiment

    NASA Technical Reports Server (NTRS)

    Nayagam, Vedha

    1998-01-01

    Liquid fuel combustion provides a major portion of the world's energy supply. In most practical combustion devices, liquid burns after being separated into a droplet spray. Essential to the design of efficient combustion systems is a knowledge of droplet combustion behavior. The microgravity environment aboard spacecraft provides an opportunity to investigate the complex interactions between the physical and chemical combustion processes involved in droplet combustion without the complications of natural buoyancy. Launched on STS-83 and STS-94 (April 4 and July 1, 1997), the Droplet Combustion Experiment (DCE) investigated the fundamentals of droplet combustion under a range of pressures (0.25 to 1 atm), oxygen mole fractions (<0.5), and droplet sizes (1.5 to 5 mm). Principal DCE flight hardware features were a chamber to supply selected test environments, the use of crew-inserted bottles, and a vent system to remove unwanted gaseous combustion products. The internal apparatus contained the droplet deployment and ignition mechanisms to burn single, freely deployed droplets in microgravity. Diagnostics systems included a 35-mm high-speed motion picture camera (see the following sequence of photos) with a backlight to photograph burning droplets and a camcorder to monitor experiment operations. Additional diagnostics included an ultraviolet-light-sensitive CCD (charge couple discharge) camera to obtain flame radiation from hydroxyl radicals (see the final figure) and a 35-mm SLR (single-lens-reflex) camera to obtain color still photographs of the flames.

  2. A hybrid DNA-templated gold nanocluster for enhanced enzymatic reduction of oxygen

    SciTech Connect

    Chakraborty, Saumen; Babanova, Sofia; Rocha, Reginaldo C.; Desireddy, Anil; Artyushkova, Kateryna; Boncella, Amy E.; Atanassov, Plamen; Martinez, Jennifer S.

    2015-08-19

    We report the synthesis and characterization of a new DNA-templated gold nanocluster (AuNC) of ~1 nm in diameter and possessing ~7 Au atoms. When integrated with bilirubin oxidase (BOD) and single walled carbon nanotubes (SWNTs), the AuNC acts as an enhancer of electron transfer (ET) and lowers the overpotential of electrocatalytic oxygen reduction reaction (ORR) by ~15 mV as compared to the enzyme alone. In addition, the presence of AuNC causes significant enhancements in the electrocatalytic current densities at the electrode. Control experiments show that such enhancement of ORR by the AuNC is specific to nanoclusters and not to plasmonic gold particles. Rotating ring disk electrode (RRDE) measurements confirm 4e– reduction of O2 to H2O with minimal production of H2O2, suggesting that the presence of AuNC does not perturb the mechanism of ORR catalyzed by the enzyme. This unique role of the AuNC as enhancer of ET at the enzyme-electrode interface makes it a potential candidate for the development of cathodes in enzymatic fuel cells, which often suffer from poor electronic communication between the electrode surface and the enzyme active site. In conclusion, the AuNC displays phosphorescence with large Stokes shift and microsecond lifetime.

  3. Noble metal-comparable SERS enhancement from semiconducting metal oxides by making oxygen vacancies

    NASA Astrophysics Data System (ADS)

    Cong, Shan; Yuan, Yinyin; Chen, Zhigang; Hou, Junyu; Yang, Mei; Su, Yanli; Zhang, Yongyi; Li, Liang; Li, Qingwen; Geng, Fengxia; Zhao, Zhigang

    2015-07-01

    Surface-enhanced Raman spectroscopy (SERS) represents a very powerful tool for the identification of molecular species, but unfortunately it has been essentially restricted to noble metal supports (Au, Ag and Cu). While the application of semiconductor materials as SERS substrate would enormously widen the range of uses for this technique, the detection sensitivity has been much inferior and the achievable SERS enhancement was rather limited, thereby greatly limiting the practical applications. Here we report the employment of non-stoichiometric tungsten oxide nanostructure, sea urchin-like W18O49 nanowire, as the substrate material, to magnify the substrate-analyte molecule interaction, leading to significant magnifications in Raman spectroscopic signature. The enrichment of surface oxygen vacancy could bring additional enhancements. The detection limit concentration was as low as 10-7 M and the maximum enhancement factor was 3.4 × 105, in the rank of the highest sensitivity, to our best knowledge, among semiconducting materials, even comparable to noble metals without `hot spots'.

  4. Palladium–platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    DOE PAGES

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; ...

    2015-07-02

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can bemore » attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. Ultimately, these results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.« less

  5. Palladium–platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction

    PubMed Central

    Wang, Xue; Choi, Sang-Il; Roling, Luke T.; Luo, Ming; Ma, Cheng; Zhang, Lei; Chi, Miaofang; Liu, Jingyue; Xie, Zhaoxiong; Herron, Jeffrey A.; Mavrikakis, Manos; Xia, Younan

    2015-01-01

    Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. These results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability. PMID:26133469

  6. A hybrid DNA-templated gold nanocluster for enhanced enzymatic reduction of oxygen

    DOE PAGES

    Chakraborty, Saumen; Babanova, Sofia; Rocha, Reginaldo C.; ...

    2015-08-19

    We report the synthesis and characterization of a new DNA-templated gold nanocluster (AuNC) of ~1 nm in diameter and possessing ~7 Au atoms. When integrated with bilirubin oxidase (BOD) and single walled carbon nanotubes (SWNTs), the AuNC acts as an enhancer of electron transfer (ET) and lowers the overpotential of electrocatalytic oxygen reduction reaction (ORR) by ~15 mV as compared to the enzyme alone. In addition, the presence of AuNC causes significant enhancements in the electrocatalytic current densities at the electrode. Control experiments show that such enhancement of ORR by the AuNC is specific to nanoclusters and not to plasmonicmore » gold particles. Rotating ring disk electrode (RRDE) measurements confirm 4e– reduction of O2 to H2O with minimal production of H2O2, suggesting that the presence of AuNC does not perturb the mechanism of ORR catalyzed by the enzyme. This unique role of the AuNC as enhancer of ET at the enzyme-electrode interface makes it a potential candidate for the development of cathodes in enzymatic fuel cells, which often suffer from poor electronic communication between the electrode surface and the enzyme active site. In conclusion, the AuNC displays phosphorescence with large Stokes shift and microsecond lifetime.« less

  7. Enhanced proliferation and dopaminergic differentiation of ventral mesencephalic precursor cells by synergistic effect of FGF2 and reduced oxygen tension

    SciTech Connect

    Jensen, Pia; Gramsbergen, Jan-Bert; Zimmer, Jens; Widmer, Hans R.; Meyer, Morten

    2011-07-15

    Effective numerical expansion of dopaminergic precursors might overcome the limited availability of transplantable cells in replacement strategies for Parkinson's disease. Here we investigated the effect of fibroblast growth factor-2 (FGF2) and FGF8 on expansion and dopaminergic differentiation of rat embryonic ventral mesencephalic neuroblasts cultured at high (20%) and low (3%) oxygen tension. More cells incorporated bromodeoxyuridine in cultures expanded at low as compared to high oxygen tension, and after 6 days of differentiation there were significantly more neuronal cells in low than in high oxygen cultures. Low oxygen during FGF2-mediated expansion resulted also in a significant increase in tyrosine hydroxylase-immunoreactive (TH-ir) dopaminergic neurons as compared to high oxygen tension, but no corresponding effect was observed for dopamine release into the culture medium. However, switching FGF2-expanded cultures from low to high oxygen tension during the last two days of differentiation significantly enhanced dopamine release and intracellular dopamine levels as compared to all other treatment groups. In addition, the short-term exposure to high oxygen enhanced in situ assessed TH enzyme activity, which may explain the elevated dopamine levels. Our findings demonstrate that modulation of oxygen tension is a recognizable factor for in vitro expansion and dopaminergic differentiation of rat embryonic midbrain precursor cells.

  8. Enhancement of acute ethanol hepatotoxicity under conditions of low oxygen supply and ischemia/reperfusion. The role of oxygen radicals.

    PubMed

    Younes, M; Wagner, H; Strubelt, O

    1989-10-15

    Using isolated hemoglobin-free perfused rat livers we studied the effect of low oxygen supply on ethanol hepatotoxicity in two models. In the first model resembling low blood supply, perfusion rate was lowered from 60 to 10 ml/min after a 30 min-equilibration phase and kept low for 60 min. As a consequence, oxygen consumption fell from 1.76 +/- 0.15 mumol/min/g to 0.51 +/- 0.02 mumol/min/g. In the second model, total ischemia was accomplished by interruption of the perfusion for 30 min and was followed by reperfusion at a perfusion rate of 60 ml/min for a further 30 min. In this model, oxygen consumption returned immediately to normal values upon reperfusion. In both models, low oxygen supply had no toxic effects of its own on livers from fed rats. While ethanol (3 g/l) given under normoxic conditions led to a moderate hepatotoxicity, its application in both models of partial as well as total ischemia and reperfusion resulted in a marked liver damage as evidenced by a strong release of sorbitol dehydrogenase, glutamate-pyruvate-transaminase, lactate dehydrogenase and glutathione, as well as by an increase in hepatic calcium content. Inhibition of ethanol metabolism by 4-methylpyrazol prevented liver damage in both models indicating that metabolism of ethanol is a prerequisite for its toxicity to occur. Also, hepatotoxicity was inhibited partially by catalase and superoxide dismutase and nearly totally by deferrioxamine and allopurinol. Thus, reactive oxygen species which are produced during ethanol metabolism as well as under conditions of low oxygen supply are mediators of hepatic damage in both models employed.

  9. Tripropellant combustion process

    NASA Technical Reports Server (NTRS)

    Kmiec, T. D.; Carroll, R. G.

    1988-01-01

    The addition of small amounts of hydrogen to the combustion of LOX/hydrocarbon propellants in large rocket booster engines has the potential to enhance the system stability. Programs being conducted to evaluate the effects of hydrogen on the combustion of LOX/hydrocarbon propellants at supercritical pressures are described. Combustion instability has been a problem during the development of large hydrocarbon fueled rocket engines. At the higher combustion chamber pressures expected for the next generation of booster engines, the effect of unstable combustion could be even more destructive. The tripropellant engine cycle takes advantage of the superior cooling characteristics of hydrogen to cool the combustion chamber and a small amount of the hydrogen coolant can be used in the combustion process to enhance the system stability. Three aspects of work that will be accomplished to evaluate tripropellant combustion are described. The first is laboratory demonstration of the benefits through the evaluation of drop size, ignition delay and burning rate. The second is analytical modeling of the combustion process using the empirical relationship determined in the laboratory. The third is a subscale demonstration in which the system stability will be evaluated. The approach for each aspect is described and the analytical models that will be used are presented.

  10. Characterization study and five-cycle tests in a fixed-bed reactor of titania-supported nickel oxide as oxygen carriers for the chemical-looping combustion of methane.

    PubMed

    Corbella, Beatriz M; de Diego, Luis F; García-Labiano, Francisco; Adánez, Juan; Palaciost, José M

    2005-08-01

    Recent investigations have shown that in the combustion of carbonaceous compounds CO2 and NOx emissions to the atmosphere can be substantially reduced by using a two stage chemical-looping process. In this process, the reduction stage is undertaken in a first reactor in which the framework oxygen of a reducible inorganic oxide is used, instead of the usual atmospheric oxygen, for the combustion of a carbonaceous compound, for instance, methane. The outlet gas from this reactor is mostly composed of CO2 and steam as reaction products and further separation of these two components can be carried out easily by simple condensation of steam. Then, the oxygen carrier found in a reduced state is transported to a second reactor in which carrier regeneration with air takes place at relatively low temperatures, consequently preventing the formation of thermal NOx. Afterward, the regenerated carrier is carried to the first reactor to reinitiate a new cycle and so on for a number of repetitive cycles, while the carrier is able to withstand the severe chemical and thermal stresses involved in every cycle. In this paper, the performance of titania-supported nickel oxides has been investigated in a fixed-bed reactor as oxygen carriers for chemical-looping combustion of methane. Samples with different nickel oxide contents were prepared by successive incipient wet impregnations, and their performance as oxygen carriers was investigated at 900 degrees C and atmospheric pressure in five-cycle fixed-bed reactor tests using pure methane and pure air for the respective reduction and regeneration stages. The evolution of the outlet gas composition in each stage was followed by gas chromatography, and the involved chemical, structural, and textural changes of the carrier in the reactor bed were studied by using different characterization techniques. From the study, it is deduced that the reactivity of these nickel-based oxygen carriers is in the two involved stages and almost independent

  11. Enhancement of the Open National Combustion Code (OpenNCC) and Initial Simulation of Energy Efficient Engine Combustor

    NASA Technical Reports Server (NTRS)

    Miki, Kenji; Moder, Jeffrey; Liou, Meng-Sing

    2016-01-01

    In this paper, we present the recent enhancement of the Open National Combustion Code (OpenNCC) and apply the OpenNCC to model a realistic combustor configuration (Energy Efficient Engine (E3)). First, we perform a series of validation tests for the newly-implemented advection upstream splitting method (AUSM) and the extended version of the AUSM-family schemes (AUSM+-up). Compared with the analytical/experimental data of the validation tests, we achieved good agreement. In the steady-state E3 cold flow results using the Reynolds-averaged Navier-Stokes(RANS), we find a noticeable difference in the flow fields calculated by the two different numerical schemes, the standard Jameson- Schmidt-Turkel (JST) scheme and the AUSM scheme. The main differences are that the AUSM scheme is less numerical dissipative and it predicts much stronger reverse flow in the recirculation zone. This study indicates that two schemes could show different flame-holding predictions and overall flame structures.

  12. Integrated oxygen-doping and dye sensitization of graphitic carbon nitride for enhanced visible light photodegradation.

    PubMed

    Liu, Shizhen; Sun, Hongqi; Ang, H M; Tade, Moses O; Wang, Shaobin

    2016-08-15

    Graphitic carbon nitride (GCN) is a promising metal-free photocatalyst while suffering from low charge mobility induced inefficient photocatalysis. In this work, oxygen doping was employed to enhance the photodegradation of organic pollutants in water on graphitic carbon nitride (GCNO) under visible light. For further absorption extension, four organic dyes (Eosin-Y, Perylene, Nile-red and Coumarin) were adopted to dye-sensitize the GCNO photocatalyst. It was found that O-doping can promote dye sensitization, which was dependent on the type of dyes and influenced the photodegradation efficiencies of methylene blue (MB) and phenol. Nile-red sensitized GCNO presented the best activity in MB degradation under λ>480nm irradiations while Eosin-Y showed the best sensitization performance for phenol degradation under λ>420nm light source. However, dye sensitization was not effective for enhanced pollutant degradation on GCN without O-doping. UV-vis diffuse reflectance spectra (UV-vis DRS), photoluminescence (PL) spectra, and photocurrent analyses were applied to investigate the mechanism of carriers' transfer, which indicated that dye molecules could inject extra electrons into GCNO energy band and the energy dislocation could suppress electron/hole recombination, enhancing photocatalytic performances.

  13. Enhancement of oxygen reduction reaction activities by Pt nanoclusters decorated on ordered mesoporous porphyrinic carbons

    SciTech Connect

    Sun-Mi Hwang; Choi, YongMan; Kim, Min Gyu; Sohn, Young-Jun; Cheon, Jae Yeong; Joo, Sang Hoon; Yim, Sung-Dae; Kuttiyiel, Kurian A.; Sasaki, Kotaro; Adzic, Radoslav R.; Park, Gu-Gon

    2016-03-08

    The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs). Recently, non-precious metal-based catalysts (NPMCs) have demonstrated much enhanced activity but their oxygen reduction reaction (ORR) activity is still inferior to that of Pt-based catalysts resulting in a much thicker electrode in the MEA. For the reduction of mass transport and ohmic overpotential we adopted a new concept of catalyst that combines an ultra-low amount of Pt nanoclusters with metal–nitrogen (M–Nx) doped ordered mesoporous porphyrinic carbon (FeCo–OMPC(L)). The 5 wt% Pt/FeCo–OMPC(L) showed a 2-fold enhancement in activities compared to a higher loading of Pt. Our experimental results supported by first-principles calculations indicate that a trace amount of Pt nanoclusters on FeCo–OMPC(L) significantly enhances the ORR activity due to their electronic effect as well as geometric effect from the reduced active sites. Finally, in terms of fuel cell commercialization, this class of catalysts is a promising candidate due to the limited use of Pt in the MEA.

  14. Enhancement of oxygen reduction reaction activities by Pt nanoclusters decorated on ordered mesoporous porphyrinic carbons

    DOE PAGES

    Sun-Mi Hwang; Choi, YongMan; Kim, Min Gyu; ...

    2016-03-08

    The high cost of Pt-based membrane electrode assemblies (MEAs) is a critical hurdle for the commercialization of polymer electrolyte fuel cells (PEFCs). Recently, non-precious metal-based catalysts (NPMCs) have demonstrated much enhanced activity but their oxygen reduction reaction (ORR) activity is still inferior to that of Pt-based catalysts resulting in a much thicker electrode in the MEA. For the reduction of mass transport and ohmic overpotential we adopted a new concept of catalyst that combines an ultra-low amount of Pt nanoclusters with metal–nitrogen (M–Nx) doped ordered mesoporous porphyrinic carbon (FeCo–OMPC(L)). The 5 wt% Pt/FeCo–OMPC(L) showed a 2-fold enhancement in activities comparedmore » to a higher loading of Pt. Our experimental results supported by first-principles calculations indicate that a trace amount of Pt nanoclusters on FeCo–OMPC(L) significantly enhances the ORR activity due to their electronic effect as well as geometric effect from the reduced active sites. Finally, in terms of fuel cell commercialization, this class of catalysts is a promising candidate due to the limited use of Pt in the MEA.« less

  15. Enhanced single-particle brightness and photostability of semiconductor polymer dots by enzymatic oxygen scavenging system

    NASA Astrophysics Data System (ADS)

    Liu, Zhihe; Yang, Yingkun; Sun, Zezhou; Wu, Changfeng

    2016-12-01

    Semiconductor polymer dots (Pdots) are emerging as an excellent fluorescent probe in biology and medicine. However, the photostability of Pdots can't meet the requirements of long term single-particle imaging and tracking applications. Here we describe the enhanced single-particle brightness and photostability of Pdots by using an efficient enzymatic oxygen scavenging system (OSS). Pdots with particle diameters of 21 nm and 43 nm (PFBT21 and PFBT43) were prepared by a nanoprecipitation method. Single-particle imaging and photobleaching were performed to investigate the effect of OSS on the per-particle brightness and photostability of Pdots. Our results indicate that the single-particle brightness of the PFBT21 Pdots in OSS was enhanced nearly two times as compare to the PFBT21 Pdots in water. The photobleaching percentages of PFBT21 and PFBT43 in OSS were determined to be 29% and 33%, respectively. These values are decreased by 2-3 times as compared to those of the same Pdots in water, indicating the significantly improved photostability of Pdots by OSS. This study provides a promising approach for enhancing photostability of Pdots in long term single-particle tracking.

  16. Distance-Dependent Plasmon-Enhanced Singlet Oxygen Production and Emission for Bacterial Inactivation.

    PubMed

    Planas, Oriol; Macia, Nicolas; Agut, Montserrat; Nonell, Santi; Heyne, Belinda

    2016-03-02

    Herein, we synthesized a series of 10 core-shell silver-silica nanoparticles with a photosensitizer, Rose Bengal, tethered to their surface. Each nanoparticle possesses an identical silver core of about 67 nm, but presents a different silica shell thickness ranging from 5 to 100 nm. These hybrid plasmonic nanoparticles thus afford a plasmonic nanostructure platform with a source of singlet oxygen ((1)O2) at a well-defined distance from the metallic core. Via time-resolved and steady state spectroscopic techniques, we demonstrate the silver core exerts a dual role of enhancing both the production of (1)O2, through enhanced absorption of light, and its radiative decay, which in turn boosts (1)O2 phosphorescence emission to a greater extent. Furthermore, we show both the production and emission of (1)O2 in vitro to be dependent on proximity to the plasmonic nanostructure. Our results clearly exhibit three distinct regimes as the plasmonic nanostructure moves apart from the (1)O2 source, with a greater enhancement for silica shell thicknesses ranging between 10 and 20 nm. Moreover, these hybrid plasmonic nanoparticles can be delivered to both Gram-positive and Gram-negative bacteria boosting both photoantibacterial activity and detection limit of (1)O2 in cells.

  17. Enhancement of pyruvate production by Torulopsis glabrata using a two-stage oxygen supply control strategy.

    PubMed

    Li, Y; Hugenholtz, J; Chen, J; Lun, S-Y

    2002-10-01

    The effect of agitation speeds on the performance of producing pyruvate by a multi-vitamin auxotrophic yeast, Torulopsis glabrata, was investigated in batch fermentation. High pyruvate yield on glucose (0.797 g g(-1)) was achieved under high agitation speed (700 rpm), but the glucose consumption rate was rather low (1.14 g l(-1) h(-1)). Glucose consumption was enhanced under low agitation speed (500 rpm), but the pyruvate yield on glucose decreased to 0.483 g g(-1). Glycerol production was observed under low agitation speed and decreased with increasing agitation speed. Based on process analysis and carbon flux distribution calculation, a two-stage oxygen supply control strategy was proposed, in which the agitation speed was controlled at 700 rpm in the first 16 h and then switched to 500 rpm. This was experimentally proven to be successful. Relatively high concentration of pyruvate (69.4 g l(-1)), high pyruvate yield on glucose (0.636 g g(-1)), and high glucose consumption rate (1.95 g l(-1)h(-1)) were achieved by applying this strategy. The productivity (1.24 g l(-1) h(-1)) was improved by 36%, 23% and 31%, respectively, compared with fermentations in which agitation speeds were kept constant at 700 rpm, 600 rpm, and 500 rpm. Experimental results indicate that the difference between the performances for producing pyruvate under a favorable state of oxygen supply (dissolved oxygen concentration >50%) was caused by the different regeneration pathways of NADH generated from glycolysis.

  18. Spatially resolved measurement of singlet delta oxygen by radar resonance-enhanced multiphoton ionization.

    PubMed

    Wu, Yue; Zhang, Zhili; Ombrello, Timothy M

    2013-07-01

    Coherent microwave Rayleigh scattering (Radar) from resonance-enhanced multiphoton ionization (REMPI) was demonstrated to directly and nonintrusively measure singlet delta oxygen, O(2)(a(1)Δ(g)), with high spatial resolution. Two different approaches, photodissociation of ozone and microwave discharge plasma in an argon and oxygen flow, were utilized for O(2)(a(1)Δ(g)) generation. The d(1)Π(g)←a(1)Δ(g) (3-0) and d(1)Π(g)←a(1)Δ(g) (1-0) bands of O(2)(a(1)Δ(g)) were detected by Radar REMPI for two different flow conditions. Quantitative absorption measurements using sensitive off-axis integrated cavity output spectroscopy (ICOS) was used simultaneously to evaluate the accuracy and sensitivity of the Radar REMPI technique. The detection limit of Radar REMPI was found to be comparable to the ICOS technique with a detection threshold of approximately 10(14) molecules/cm(3) but with a spatial resolution that was 8 orders of magnitude smaller than the ICOS technique.

  19. Enhancing the photoelectrochemical properties of titanium dioxide by thermal treatment in oxygen deficient environment

    NASA Astrophysics Data System (ADS)

    Singh, Aadesh P.; Kodan, Nisha; Mehta, Bodh R.

    2016-05-01

    The effect of thermal treatment on TiO2 thin films under oxygen deficient environment (5% H2 in Ar) at partial pressure of 2 × 10-2 Torr have been studied for photoelectrochemical (PEC) water splitting application. Thermal treatment in anatase TiO2 thin films exhibits a shift in optical absorption from UV to visible region and activates TiO2 for water splitting application under visible light. X-ray photoelectron spectroscopy results showed that the thermal treated thin films contain oxygen vacancies, which suggests improved charge transport. Optical absorption, X-ray spectroscopy (XPS) and Kelvin probe force microscope (KPFM) studies show reduction in band gap by 0.36 eV, shift in valence band maximum by 0.49 eV towards the Fermi level and work function values by 0.3 eV towards the vacuum level. The pristine TiO2 thin films exhibit very less photoactivity in terms of photocurrent density, whereas thermally treated thin films displayed a markedly enhanced photocurrent density of ∼2.41 mA/cm2 at 0.23 V vs. Ag/AgCl. Higher values of photocurrent density in thermal treated TiO2 films have been explained in terms of change in the optical and electrical properties along with energy band diagram.

  20. Enhancement of chemical-oxygen demand and color removal of distillery spent-wash by ozonation.

    PubMed

    Srivastava, S; Bose, P; Tare, V

    2006-04-01

    Distillery spent-wash has very high organic content (75,000 to 125,000 mg/L chemical-oxygen demand [COD]), color, and contains difficult-to-biodegrade organic compounds. For example, anaerobic treatment of the distillery spent-wash used in this study resulted in 60% COD reduction and low color removal. Subsequent aerobic treatment of the anaerobic effluent resulted in enhancement of COD removal to 66%. In this paper, the effect of ozonation on various properties of the anaerobically treated distillery effluent, including the effect on its subsequent aerobic biodegradation, was investigated. Ozonation of the anaerobically treated distillery effluent at various ozone doses resulted in the reduction of total-organic carbon (TOC), COD, COD/TOC ratio, absorbance, color, and increase in the biochemical-oxygen demand (BOD)/COD ratio of the effluent. Further, ozonation of the anaerobically treated distillery effluent at an ozone dose of 2.08 mg/mg initial TOC and subsequent aerobic biodegradation resulted in 87.4% COD removal, as compared to 66% removal when ozonation was not used.

  1. Shock-tube measurements of excited oxygen atoms using cavity-enhanced absorption spectroscopy.

    PubMed

    Nations, Marcel; Wang, Shengkai; Goldenstein, Christopher S; Sun, Kai; Davidson, David F; Jeffries, Jay B; Hanson, Ronald K

    2015-10-10

    We report the use of cavity-enhanced absorption spectroscopy (CEAS) using two distributed feedback diode lasers near 777.2 and 844.6 nm for sensitive, time-resolved, in situ measurements of excited-state populations of atomic oxygen in a shock tube. Here, a 1% O2/Ar mixture was shock-heated to 5400-8000 K behind reflected shock waves. The combined use of a low-finesse cavity, fast wavelength scanning of the lasers, and an off-axis alignment enabled measurements with 10 μs time response and low cavity noise. The CEAS absorption gain factors of 104 and 142 for the P35←S520 (777.2 nm) and P0,1,23←S310 (844.6 nm) atomic oxygen transitions, respectively, significantly improved the detection sensitivity over conventional single-pass measurements. This work demonstrates the potential of using CEAS to improve shock-tube studies of nonequilibrium electronic-excitation processes at high temperatures.

  2. Dissolved carbonic anhydrase for enhancing post-combustion carbon dioxide hydration in aqueous ammonia

    SciTech Connect

    Collett, James R.; Heck, Robert W.; Zwoster, Andy

    2011-04-01

    Aqueous ammonia solvents that capture CO2 as ionic complexes of carbonates with ammonium have recently been advanced as alternatives to amine-based solvents due to their lower energy requirements for thermal regeneration. In ammonia based solvents, the hydration of CO2 to form bicarbonate may become a rate-limiting step as the CO2 loading increases and the resulting pH level of the solvent decreases. Variants of the enzyme carbonic anhydrase can accelerate the reversible hydration of CO2 to yield bicarbonate by more than 10(6)-fold. The possible benefit of bovine carbonic anhydrase (BCA) addition to solutions of aqueous ammonia to enhance CO2 hydration was investigated in semi-batch reactions within continuously stirred tank reactors or in a bubble column gas-liquid contactor. Adding 154 mg/liter of BCA to 2 M aqueous ammonia provided a 34.1% overall increase in the rate of CO2 hydration (as indicated by the production of [H+]) as the pH declined from 9.6 to 8.6 during sparging with a 15% CO2, 85% N-2 gas at a flow rate of 3 lpm. The benefits of adding BCA to enhance CO2 hydration were only discernable below similar to pH 9. The implications of the apparent pH limitations on the utility of BCA are discussed in the context of absorber unit operation design. Possible embodiments of carbonic anhydrase as either an immobilized catalyst or as a dissolved, recirculating catalyst in potential plant scale aqueous ammonia systems are considered as well. (C) 2010 Published by Elsevier Ltd.

  3. Pseudomonas syringae enhances herbivory by suppressing the reactive oxygen burst in Arabidopsis

    PubMed Central

    Groen, Simon C.; Humphrey, Parris T.; Chevasco, Daniela; Ausubel, Frederick M.; Pierce, Naomi E.; Whiteman, Noah K.

    2015-01-01

    Plant-herbivore interactions have evolved in the presence of plant-colonizing microbes. These microbes can have important third-party effects on herbivore ecology, as exemplified by drosophilid flies that evolved from ancestors feeding on plant-associated microbes. Leaf-mining flies in the genus Scaptomyza, which is nested within the paraphyletic genus Drosophila, show strong associations with bacteria in the genus Pseudomonas, including Pseudomonas syringae. Adult females are capable of vectoring these bacteria between plants and larvae show a preference for feeding on P. syringae-infected leaves. Here we show that Scaptomyza flava larvae can also vector P. syringae to and from feeding sites, and that they not only feed more, but also develop faster on plants previously infected with P. syringae. Our genetic and physiological data show that P. syringae enhances S. flava feeding on infected plants at least in part by suppressing anti-herbivore defenses mediated by reactive oxygen species. PMID:26205072

  4. Enhanced oxygen reduction activity and solid oxide fuel cell performance with a nanoparticles-loaded cathode.

    PubMed

    Zhang, Xiaomin; Liu, Li; Zhao, Zhe; Tu, Baofeng; Ou, Dingrong; Cui, Daan; Wei, Xuming; Chen, Xiaobo; Cheng, Mojie

    2015-03-11

    Reluctant oxygen-reduction-reaction (ORR) activity has been a long-standing challenge limiting cell performance for solid oxide fuel cells (SOFCs) in both centralized and distributed power applications. We report here that this challenge has been tackled with coloading of (La,Sr)MnO3 (LSM) and Y2O3 stabilized zirconia (YSZ) nanoparticles within a porous YSZ framework. This design dramatically improves ORR activity, enhances fuel cell output (200-300% power improvement), and enables superior stability (no observed degradation within 500 h of operation) from 600 to 800 °C. The improved performance is attributed to the intimate contacts between nanoparticulate YSZ and LSM particles in the three-phase boundaries in the cathode.

  5. Oxygen-enhanced models for globular cluster stars. III - Horizontal-branch sequences

    NASA Technical Reports Server (NTRS)

    Dorman, Ben

    1992-01-01

    A large grid of horizontal-branch (HB) evolutionary sequences which have been calculated with core expansion and semiconvection and with enhanced oxygen composition are presented and described. Tracks for 10 different metallicities are computed; they range from (Fe/H) = -0.47 to -2.26 and comprise a total of 115 sequences. The evolution is traced from the zero-age horizontal-branch (ZAHB) to the lower AGB at a point where log L/solar luminosity = 2.25. All of the sequences are illustrated on both the theoretical H-R diagram and on the B, V color-magnitude diagram. A complete set of tables for the ZAHB models and a representative sample of tabulations of the track parameters are provided. The phenomena which control HB evolution morphology, and existing certainties in theoretical HB models are discussed.

  6. [Enhancing the efficiency of sanatorium and resort rehabilitation of the liquidators of the Chernobyl accident by hyperbaric oxygenation].

    PubMed

    Ovod, V O; Shymonko, I T

    2003-01-01

    Results of our studies permit reaching the conclusion that oral intake of the mineral water Naftusya as the leading factor with an additional prescription of the course of the hyperbaric oxygenation procedures promote enhancement of functional reserves, stabilize free-radical processes and bodily system of antioxidant defence, favour stabilization of cell membranes, initiate decorporative action, diminish depression of immunity and supply oxygen to those enzymic systems whose activity has been adversely affected by hypoxia.

  7. LOX/Hydrocarbon Combustion Instability Investigation

    NASA Technical Reports Server (NTRS)

    Jensen, R. J.; Dodson, H. C.; Claflin, S. E.

    1989-01-01

    The LOX/Hydrocarbon Combustion Instability Investigation Program was structured to determine if the use of light hydrocarbon combustion fuels with liquid oxygen (LOX) produces combustion performance and stability behavior similar to the LOX/hydrogen propellant combination. In particular methane was investigated to determine if that fuel can be rated for combustion instability using the same techniques as previously used for LOX/hydrogen. These techniques included fuel temperature ramping and stability bomb tests. The hot fire program probed the combustion behavior of methane from ambient to subambient temperatures. Very interesting results were obtained from this program that have potential importance to future LOX/methane development programs. A very thorough and carefully reasoned documentation of the experimental data obtained is contained. The hot fire test logic and the associated tests are discussed. Subscale performance and stability rating testing was accomplished using 40,000 lb. thrust class hardware. Stability rating tests used both bombs and fuel temperature ramping techniques. The test program was successful in generating data for the evaluation of the methane stability characteristics relative to hydrogen and to anchor stability models. Data correlations, performance analysis, stability analyses, and key stability margin enhancement parameters are discussed.

  8. Atomic Ordering Enhanced Electrocatalytic Activity of Nanoalloys for Oxygen Reduction Reaction

    SciTech Connect

    Loukrakpam, Rameshwori; Shan, Shiyao; Petkov, Valeri; Yang, Lefu; Luo, Jin; Zhong, Chuan-Jian

    2013-10-01

    For oxygen reduction reaction (ORR) over alloy electrocatalysts, the understanding of how the atomic arrangement of the metal species in the nanocatalysts is responsible for the catalytic enhancement is challenging for achieving better design and tailoring of nanoalloy catalysts. This paper reports results of an investigation of the atomic structures and the electrocatalytic activities of ternary and binary nanoalloys, aiming at revealing a fundamental insight into the unique atomic-scale structure-electrocatalytic activity relationship. PtIrCo catalyst and its binary counterparts (PtCo and PtIr) are chosen as a model system for this study. The effect of thermochemical treatment temperature on the atomic-scale structure of the catalysts was examined as a useful probe to the structure-activity correlation. The structural characterization of the binary and ternary nanoalloy catalysts was performed by combining surface sensitive techniques such as XPS and 3D atomic ordering sensitive techniques such as high-energy X-ray diffraction (HE-XRD) coupled to atomic pair distribution function (PDF) analysis (HE-XRD/PDFs) and computer simulations. The results show that the thermal treatment temperature tunes the nanoalloy’s atomic and chemical ordering in a different way depending on the chemical composition, leading to differences in the nanoalloy’s mass and specific activities. A unique structural tunability of the atomic ordering in a platinum-iridium-cobalt nanoalloy has been revealed for enhancing greatly the electrocatalytic activity toward oxygen reduction reaction, which has significant implication for rational design and nanoengineering of advanced catalysts for electrochemical energy conversion and storage.

  9. Coal Combustion Science

    SciTech Connect

    Hardesty, D.R.; Fletcher, T.H.; Hurt, R.H.; Baxter, L.L. )

    1991-08-01

    The objective of this activity is to support the Office of Fossil Energy in executing research on coal combustion science. This activity consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency Coal Combustion Science Project. Specific tasks for this activity include: (1) coal devolatilization - the objective of this risk is to characterize the physical and chemical processes that constitute the early devolatilization phase of coal combustion as a function of coal type, heating rate, particle size and temperature, and gas phase temperature and oxidizer concentration; (2) coal char combustion -the objective of this task is to characterize the physical and chemical processes involved during coal char combustion as a function of coal type, particle size and temperature, and gas phase temperature and oxygen concentration; (3) fate of mineral matter during coal combustion - the objective of this task is to establish a quantitative understanding of the mechanisms and rates of transformation, fragmentation, and deposition of mineral matter in coal combustion environments as a function of coal type, particle size and temperature, the initial forms and distribution of mineral species in the unreacted coal, and the local gas temperature and composition.

  10. IGF-I enhances cellular senescence via the reactive oxygen species-p53 pathway

    SciTech Connect

    Handayaningsih, Anastasia-Evi; Takahashi, Michiko; Fukuoka, Hidenori; Iguchi, Genzo; Nishizawa, Hitoshi; Yamamoto, Masaaki; Suda, Kentaro; Takahashi, Yutaka

    2012-08-24

    Highlights: Black-Right-Pointing-Pointer Cellular senescence plays an important role in tumorigenesis and aging process. Black-Right-Pointing-Pointer We demonstrated IGF-I enhanced cellular senescence in primary confluent cells. Black-Right-Pointing-Pointer IGF-I enhanced cellular senescence in the ROS and p53-dependent manner. Black-Right-Pointing-Pointer These results may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging. -- Abstract: Cellular senescence is characterized by growth arrest, enlarged and flattened cell morphology, the expression of senescence-associated {beta}-galactosidase (SA-{beta}-gal), and by activation of tumor suppressor networks. Insulin-like growth factor-I (IGF-I) plays a critical role in cellular growth, proliferation, tumorigenesis, and regulation of aging. In the present study, we show that IGF-I enhances cellular senescence in mouse, rat, and human primary cells in the confluent state. IGF-I induced expression of a DNA damage marker, {gamma}H2AX, the increased levels of p53 and p21 proteins, and activated SA-{beta}-gal. In the confluent state, an altered downstream signaling of IGF-I receptor was observed. Treatment with a reactive oxygen species (ROS) scavenger, N-acetylcystein (NAC) significantly suppressed induction of these markers, indicating that ROS are involved in the induction of cellular senescence by IGF-I. In p53-null mouse embryonic fibroblasts, the IGF-I-induced augmentation of SA-{beta}-gal and p21 was inhibited, demonstrating that p53 is required for cellular senescence induced by IGF-I. Thus, these data reveal a novel pathway whereby IGF-I enhances cellular senescence in the ROS and p53-dependent manner and may explain the underlying mechanisms of IGF-I involvement in tumorigenesis and in regulation of aging.

  11. Generation mechanism of L-value dependence of oxygen flux enhancements during substorms

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Kletzing, C.

    2015-12-01

    The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures charged particles with an energy range from ~eV to ~ tens of keV. The observation shows that the energy flux of the particles increases inside the geosynchronous orbit during substorms. For some night-side events around the apogee, the energy flux of O+ ion enhances below ~10 keV at lower L shell, whereas the flux below ~8 keV sharply decreases at higher L shells. This structure of L-energy spectrogram of flux is observed only for the O+ ions. The purpose of this study is to investigate the generation mechanism of the structure by using numerical simulations. We utilized the global MHD simulation developed by Tanaka et al (2010, JGR) to simulate the electric and magnetic fields during substorms. We performed test particle simulation under the electric and magnetic fields by applying the same model introduced by Nakayama et al. (2015, JGR). In the test particle simulation each test particle carries the real number of particles in accordance with the Liouville theorem. Using the real number of particles, we reconstructed 6-dimensional phase space density and differential flux of O+ ions in the inner magnetosphere. We obtained the following results. (1) Just after the substorm onset, the dawn-to-dusk electric field is enhanced to ~ 20 mV/m in the night side tail region at L > 7. (2) The O+ ions are accelerated and transported to the inner region (L > ~5.5) by the large-amplitude electric field. (3) The reconstructed L-energy spectrogram shows a similar structure to the Van Allen Probes observation. (4) The difference in the flux enhancement between at lower L shell and higher L shells is due to two distinct acceleration processes: adiabatic and non-adiabatic. We will discuss the relationship between the particle acceleration and the structure of L-energy spectrogram of flux enhancement in detail.

  12. Multicolor tunability and upconversion enhancement of fluoride nanoparticles by oxygen dopant

    NASA Astrophysics Data System (ADS)

    Niu, Wenbin; Wu, Suli; Zhang, Shufen; Su, Liap Tat; Tok, Alfred Iing Yoong

    2013-08-01

    The ability to manipulate the upconversion luminescence of lanthanide-ion doped fluoride upconversion nanoparticles (UCNPs) is particularly important and highly desired due to their wide applications in color displays, multiplexing bioassays and multicolor imaging. Here, we developed a strategy for simultaneously tuning color output and enhancing upconversion emission of Yb/Er doped fluoride UCNPs, based on adjusting the oxygen doping level. The synthesis of multicolored multifunctional NaGdF4:Yb,Er UCNPs was used as the model host system to demonstrate this protocol. Ammonium nitrate (NH4NO3) was used as the oxygen source and added into the reaction system at the beginning stage of nucleation and growth process of fluoride UCNPs, which facilitates the formation of enough oxygen atoms and the diffusion of these into the fluoride host matrix. The results revealed that multicolour output and upconversion enhancement mainly resulted from the variation of phonon energy and crystal field symmetry of the host lattice, respectively. This strategy can be further expanded to other fluoride host matrices. As an example of an application, multicolored UCNPs were used as a color converter in light emitting diodes, which can effectively convert near-infrared light into visible light. It is expected that these multicolored UCNPs will be promising for applications in multiplexing biodetection, bioimaging (optical and magnetic resonance imaging) and other optical technologies, and the present method for the control of O2- doping may also be used in other functional nanomaterials.The ability to manipulate the upconversion luminescence of lanthanide-ion doped fluoride upconversion nanoparticles (UCNPs) is particularly important and highly desired due to their wide applications in color displays, multiplexing bioassays and multicolor imaging. Here, we developed a strategy for simultaneously tuning color output and enhancing upconversion emission of Yb/Er doped fluoride UCNPs, based

  13. Fuel properties to enable lifted-flame combustion

    SciTech Connect

    Kurtz, Eric

    2015-03-15

    The Fuel Properties to Enable Lifted-Flame Combustion project responded directly to solicitation DE-FOA-0000239 AOI 1A, Fuels and Lubricants for Advanced Combustion Regimes. This subtopic was intended to encompass clean and highly-efficient, liquid-fueled combustion engines to achieve extremely low engine-out nitrogen oxides (NOx) and particulate matter (PM) as a target and similar efficiency as state-of-the-art direct injection diesel engines. The intent of this project was to identify how fuel properties can be used to achieve controllable Leaner Lifted Flame Combustion (LLFC) with low NOx and PM emissions. Specifically, this project was expected to identify and test key fuel properties to enable LLFC and their compatibility with current fuel systems and to enhance combustion models to capture the effect of fuel properties on advanced combustion. Successful demonstration of LLFC may reduce the need for after treatment devices, thereby reducing costs and improving thermal efficiency. The project team consisted of key technical personnel from Ford Motor Company (FMC), the University of Wisconsin-Madison (UW), Sandia National Laboratories (SNL) and Lawrence Livermore National Laboratories (LLNL). Each partner had key roles in achieving project objectives. FMC investigated fuel properties relating to LLFC and sooting tendency. Together, FMC and UW developed and integrated 3D combustion models to capture fuel property combustion effects. FMC used these modeling results to develop a combustion system and define fuel properties to support a single-cylinder demonstration of fuel-enabled LLFC. UW investigated modeling the flame characteristics and emissions behavior of different fuels, including those with different cetane number and oxygen content. SNL led spray combustion experiments to quantify the effect of key fuel properties on combustion characteristics critical for LLFC, as well as single cylinder optical engine experiments to improve fundamental

  14. Low Oxygen Tension During Incubation Periods of Chondrocyte Expansion Is Sufficient to Enhance Postexpansion Chondrogenesis

    PubMed Central

    Ginley, Nell M.; Caplan, Arnold I.; Niyibizi, Christopher; Dennis, James E.

    2010-01-01

    To determine whether low oxygen (O2) tension during expansion affects the matrix density, as well as quantity, of cartilage formed, and to determine whether application of low O2 tension during incubation periods alone is sufficient to modulate chondrogenic expression, rabbit chondrocytes expanded at either 21% O2 or 5% O2 were analyzed for glycosaminoglycan (GAG) and DNA content, total collagen, and gene expression during expansion and postexpansion aggregate cultures. When cultured as aggregates at 21% O2, chondrocytes expanded at 5% O2 produced cartilage aggregates that contained more total GAG, GAG per wet weight, GAG per DNA, and total collagen than chondrocytes expanded at 21% O2. Less of an effect on GAG and collagen content was observed when aggregate culture was performed at 5% O2. Real-time polymerase chain reaction analysis of COL2A1 expression showed upregulated levels of type IIA (an early marker) and IIB (a late marker) during expansion and elevated levels of type IIB during aggregate culture in chondrocytes expanded in low O2. The application of low O2 tension during incubation periods of chondrocyte expansion enhances the ultimate cartilage matrix density and quantity, and this enhancement can be achieved through the use of an O2 control incubator. PMID:19958052

  15. Colloidal gold nanorings for improved photodynamic therapy through field-enhanced generation of reactive oxygen species

    NASA Astrophysics Data System (ADS)

    Hu, Yue; Yang, Yamin; Wang, Hongjun; Du, Henry

    2013-02-01

    Au nanostructures that exhibit strong localized surface plasmon resonance (SPR) have excellent potential for photo-medicine, among a host of other applications. Here, we report the synthesis and use of colloidal gold nanorings (GNRs) with potential for enhanced photodynamic therapy of cancer. The GNRs were fabricated via galvanic replacement reaction of sacrificial Co nanoparticles in gold salt solution with low molecular weight (Mw = 2,500) poly(vinylpyrrolidone) (PVP) as a stabilizing agent. The size and the opening of the GNRs were controlled by the size of the starting Co particles and the concentration of the gold salt. UV-Vis absorption measurements indicated the tunability of the SPR of the GNRs from 560 nm to 780 nm. MTT assay showed that GNRs were non-toxic and biocompatible when incubated with breast cancer cells as well as the healthy counterpart cells. GNRs conjugated with 5-aminolevulinic acid (5-ALA) photosensitizer precursor led to elevated formation of reactive oxygen species and improved efficacy of photodynamic therapy of breast cancer cells under light irradiation compared to 5-ALA alone. These results can be attributed to significantly enhance localized electromagnetic field of the GNRs.

  16. Fosfomycin enhances phagocyte-mediated killing of Staphylococcus aureus by extracellular traps and reactive oxygen species

    PubMed Central

    Shen, Fengge; Tang, Xudong; Cheng, Wei; Wang, Yang; Wang, Chao; Shi, Xiaochen; An, Yanan; Zhang, Qiaoli; Liu, Mingyuan; Liu, Bo; Yu, Lu

    2016-01-01

    The successful treatment of bacterial infections is the achievement of a synergy between the host’s immune defences and antibiotics. Here, we examined whether fosfomycin (FOM) could improve the bactericidal effect of phagocytes, and investigated the potential mechanisms. FOM enhanced the phagocytosis and extra- or intracellular killing of S. aureus by phagocytes. And FOM enhanced the extracellular killing of S. aureus in macrophage (MФ) and in neutrophils mediated by extracellular traps (ETs). ET production was related to NADPH oxidase-dependent reactive oxygen species (ROS). Additionally, FOM increased the intracellular killing of S. aureus in phagocytes, which was mediated by ROS through the oxidative burst process. Our results also showed that FOM alone induced S. aureus producing hydroxyl radicals in order to kill the bacterial cells in vitro. In a mouse peritonitis model, FOM treatment increased the bactericidal extra- and intracellular activity in vivo, and FOM strengthened ROS and ET production from peritoneal lavage fluid ex vivo. An IVIS imaging system assay further verified the observed in vivo bactericidal effect of the FOM treatment. This work may provide a deeper understanding of the role of the host’s immune defences and antibiotic interactions in microbial infections. PMID:26778774

  17. BODIPY-doped silica nanoparticles with reduced dye leakage and enhanced singlet oxygen generation

    PubMed Central

    Wang, Zhuyuan; Hong, Xuehua; Zong, Shenfei; Tang, Changquan; Cui, Yiping; Zheng, Qingdong

    2015-01-01

    Photodynamic therapy (PDT) is a promising modality for cancer treatment. The essential element in PDT is the photosensitizer, which can be excited by light of a specific wavelength to generate cytotoxic oxygen species (ROS) capable of killing tumor cells. The effectiveness of PDT is limited in part by the low yield of ROS from existing photosensitizers and the unwanted side effects induced by the photosensitizers toward normal cells. Thus the design of nanoplatforms with enhanced PDT is highly desirable but remains challenging. Here, we developed a heavy atom (I) containing dipyrromethene boron difluoride (BODIPY) dye with a silylated functional group, which can be covalently incorporated into a silica matrix to form dye-doped nanoparticles. The incorporated heavy atoms can enhance the generation efficiency of ROS. Meanwhile, the covalently dye-encapsulated nanoparticles can significantly reduce dye leakage and subsequently reduce unwanted side effects. The nanoparticles were successfully taken up by various tumor cells and showed salient phototoxicity against these cells upon light irradiation, demonstrating promising applications in PDT. Moreover, the incorporated iodine atom can be replaced by a radiolabeled iodine atom (e.g., I-124, I-125). The resulting nanoparticles will be good contrast agents for positron emission tomography (PET) imaging with their PDT functionality retained. PMID:26211417

  18. Warm Oxygen Enhancements in the Inner Magnetosphere and Their Relation to Geomagnetic Activity, Plasmasphere, and Ring Current.

    NASA Astrophysics Data System (ADS)

    Jahn, J. M.; Skoug, R. M.; Gkioulidou, M.; Bonnell, J. W.; Larsen, B.; Reeves, G. D.; Spence, H. E.

    2014-12-01

    Ionospheric oxygen plays an important role in the dynamics of Earth's magnetosphere. During geomagnetic storms, oxygen transported into the tail can experience significant energization and become a major contributor to the storm-time ring current. At very low energies, a dense cold oxygen torus straddles the outer plasmasphere, frequently with O+/H+ ratios approaching unity. With the Radiation Belt Storm Probes we now also observe a third oxygen population in this region. In this paper we discuss the nature of "warm" (10's eV to few keV, i.e., between plasmasphere and ring current ion energies) oxygen density enhancements over the course of the Van Allen Probes mission. We find that the composition of this warm thermal plasma is very dynamic throughout the inner magnetosphere. The warm oxygen density is highly responsive to changes in geomagnetic activity, varying by more than two orders of magnitude between quiet times and moderate storms. This variation at times is a greater than the variation of the corresponding proton density. The O+/H+ warm plasma density ration will frequently exceed unity, usually during the recovery phase of storms. The region of enhanced warm oxygen density reaches from the plasmasphere boundary out to at least geosynchronous orbit (the largest L-shells covered by the Van Allen Probes). It can be observed at all local times. Barring other geomagnetic activity, warm oxygen density enhancements disappear typically within 5 days of their first detection, which is consistent with drift times through the inner magnetosphere along open drift paths. We are putting these characteristics in context of the composition, location, and evolution of the plasmasphere and the ring current.

  19. Reactive Oxygen Species Prevent Imiquimod-Induced Psoriatic Dermatitis through Enhancing Regulatory T Cell Function

    PubMed Central

    Choi, Eun-Jeong; Hong, Min-Pyo; Kie, Jeong-Hae; Lim, Woosung; Lee, Hyeon Kook; Moon, Byung-In; Seoh, Ju-Young

    2014-01-01

    Psoriasis is a chronic inflammatory skin disease resulting from immune dysregulation. Regulatory T cells (Tregs) are important in the prevention of psoriasis. Traditionally, reactive oxygen species (ROS) are known to be implicated in the progression of inflammatory diseases, including psoriasis, but many recent studies suggested the protective role of ROS in immune-mediated diseases. In particular, severe cases of psoriasis vulgaris have been reported to be successfully treated by hyperbaric oxygen therapy (HBOT), which raises tissue level of ROS. Also it was reported that Treg function was closely associated with ROS level. However, it has been only investigated in lowered levels of ROS so far. Thus, in this study, to clarify the relationship between ROS level and Treg function, as well as their role in the pathogenesis of psoriasis, we investigated imiquimod-induced psoriatic dermatitis (PD) in association with Treg function both in elevated and lowered levels of ROS by using knockout mice, such as glutathione peroxidase-1−/− and neutrophil cytosolic factor-1−/− mice, as well as by using HBOT or chemicals, such as 2,3-dimethoxy-1,4-naphthoquinone and N-acetylcysteine. The results consistently showed Tregs were hyperfunctional in elevated levels of ROS, whereas hypofunctional in lowered levels of ROS. In addition, imiquimod-induced PD was attenuated in elevated levels of ROS, whereas aggravated in lowered levels of ROS. For the molecular mechanism that may link ROS level and Treg function, we investigated the expression of an immunoregulatory enzyme, indoleamine 2,3-dioxygenase (IDO) which is induced by ROS, in PD lesions. Taken together, it was implied that appropriately elevated levels of ROS might prevent psoriasis through enhancing IDO expression and Treg function. PMID:24608112

  20. Adhesion of polymorphonuclear leukocytes to endothelium enhances the efficiency of detoxification of oxygen-free radicals.

    PubMed Central

    Hoover, R. L.; Robinson, J. M.; Karnovsky, M. J.

    1987-01-01

    Polymorphonuclear leukocytes can produce active oxygen species such as hydrogen peroxide and superoxide under various conditions. Because these substances can be toxic to cells, it is possible that the interaction between the circulating leukocytes and the blood vessel wall, either in normal circulation or during the acute inflammatory response, could damage the endothelial lining. Using an in vitro system of cultured endothelial cells and isolated polymorphonuclear leukocytes, we have measured the levels of detectable superoxide when neutrophils are attached to either endothelial monolayers or to plastic. Our results show that the levels of superoxide, on a per-cell basis, are lower when the neutrophils are attached to endothelium than when attached to plastic, even if the neutrophils are stimulated with phorbol myristate acetate. This is also reflected in data showing that no injury occurs to the endothelial cells, as measured by 51Cr release, under these same conditions. When endothelial cells are pretreated with an inhibitor of superoxide dismutase, diethyldithiocarbamate, the levels of superoxide detected are the same for neutrophils stimulated on plastic and those on the endothelial monolayer, suggesting that endothelial superoxide dismutase may remove a portion of the neutrophil-generated superoxide from the detection system. Further evidence for the role of endothelium in destroying superoxide is suggested by results that show that the level of detectable superoxide released from neutrophils attached to formalin-fixed endothelial monolayers is the same as that for neutrophils attached to plastic. It is important to note that with the inhibitor of superoxide dismutase present, the endothelial monolayers do not display enhanced 51Cr release under the conditions employed. When both endothelial catalase and glutathione reductase are inhibited, we detect increased 51Cr release from endothelial cells in response to stimulated neutrophils. Our results show that

  1. Self-enhanced catalytic activities of functionalized graphene sheets in the combustion of nitromethane: molecular dynamic simulations by molecular reactive force field.

    PubMed

    Zhang, Chaoyang; Wen, Yushi; Xue, Xianggui

    2014-08-13

    Functionalized graphene sheet (FGS) is a promising additive that enhances fuel/propellant combustion, and the determination of its mechanism has attracted much interest. In the present study, a series of molecular dynamic simulations based on a reactive force field (ReaxFF) are performed to explore the catalytic activity (CA) of FGS in the thermal decay of nitromethane (NM, CH3NO2). FGSs and pristine graphene sheets (GSs) are oxidized in hot NM liquid to increase their functionalities and subsequently show self-enhanced CAs during the decay. The CAs result from the interatomic exchanges between the functional groups on the sheets and the NM liquid, i.e., mainly between H and O atoms. CA is dependent on the density of NM, functionalities of sheets, and temperature. The GSs and FGSs that originally exhibit different functionalities tend to possess similar functionalities and consequently similar CAs as temperature increases. Other carbon materials and their oxides can accelerate combustion of other fuels/propellants similar to NM, provided that they can be dispersed and their key reaction steps in combustion are similar to NM.

  2. Engineering of Nitrosomonas europaea to express Vitreoscilla hemoglobin enhances oxygen uptake and conversion of ammonia to nitrite.

    PubMed

    Kunkel, Stephanie A; Pagilla, Krishna R; Stark, Benjamin C

    2015-12-01

    Nitrosomonas europaea was transformed with a recombinant plasmid bearing the gene (vgb) encoding the hemoglobin (VHb) from the bacterium Vitreoscilla under control of the N. europaea amoC P1 promoter. Vgb was maintained stably and appeared to be expressed in the transformants at VHb levels of about 0.75 nmol/g wet weight. Expression of VHb in the N. europaea transformants was correlated with an approximately 2 fold increase in oxygen uptake rate by whole cells at oxygen concentrations in the range of 75-100% saturation, but no change in oxygen uptake rate at oxygen concentrations below 25% saturation. VHb expression was also correlated with an increase of as much as about 30% in conversion of ammonia to nitrite by growing cells. The results suggest that engineering of key aerobic wastewater bacteria to express bacterial hemoglobins may be a useful strategy to produce species with enhanced respiratory abilities.

  3. UNDERGROUNG PLACEMENT OF COAL PROCESSING WASTE AND COAL COMBUSTION BY-PRODUCTS BASED PASTE BACKFILL FOR ENHANCED MINING ECONOMICS

    SciTech Connect

    Y.P. Chugh; D. Biswas; D. Deb

    2002-06-01

    This project has successfully demonstrated that the extraction ratio in a room-and-pillar panel at an Illinois mine can be increased from the current value of approximately 56% to about 64%, with backfilling done from the surface upon completion of all mining activities. This was achieved without significant ground control problems due to the increased extraction ratio. The mined-out areas were backfilled from the surface with gob, coal combustion by-products (CCBs), and fine coal processing waste (FCPW)-based paste backfill containing 65%-70% solids to minimize short-term and long-term surface deformations risk. This concept has the potential to increase mine productivity, reduce mining costs, manage large volumes of CCBs beneficially, and improve the miner's health, safety, and environment. Two injection holes were drilled over the demonstration panel to inject the paste backfill. Backfilling was started on August 11, 1999 through the first borehole. About 9,293 tons of paste backfill were injected through this borehole with a maximum flow distance of 300-ft underground. On September 27, 2000, backfilling operation was resumed through the second borehole with a mixture of F ash and FBC ash. A high-speed auger mixer (new technology) was used to mix solids with water. About 6,000 tons of paste backfill were injected underground through this hole. Underground backfilling using the ''Groutnet'' flow model was simulated. Studies indicate that grout flow over 300-foot distance is possible. Approximately 13,000 tons of grout may be pumped through a single hole. The effect of backfilling on the stability of the mine workings was analyzed using SIUPANEL.3D computer program and further verified using finite element analysis techniques. Stiffness of the backfill mix is most critical for enhancing the stability of mine workings. Mine openings do not have to be completely backfilled to enhance their stability. Backfill height of about 50% of the seam height is adequate to

  4. Enhanced low-temperature CO oxidation on a stepped platinum surface for oxygen pressures above 10(-5) Torr.

    PubMed

    Lewis, Henry D; Burnett, Daniel J; Gabelnick, Aaron M; Fischer, Daniel A; Gland, John L

    2005-11-24

    The rate of CO oxidation has been characterized on the stepped Pt(411) surface for oxygen pressures up to 0.002 Torr, over the 100-1000 K temperature range. CO oxidation was characterized using both temperature-programmed reaction spectroscopy (TPRS) and in situ soft X-ray fluorescence yield near-edge spectroscopy (FYNES). New understanding of the important role surface defects play in accelerating CO oxidation for oxygen pressure above 10(-5) Torr is presented in this paper for the first time. For saturated monolayers of CO, the oxidation rate increases and the activation energy decreases significantly for oxygen pressures above 10(-5) Torr. This enhanced CO oxidation rate is caused by a change in the rate-limiting step to a surface reaction limited process above 10(-5) Torr oxygen from a CO desorption limited process at lower oxygen pressure. For example, in oxygen pressures above 0.002 Torr, CO(2) formation begins at 275 K even for the CO saturated monolayer, which is well below the 350 K onset temperature for CO desorption. Isothermal kinetic measurements in flowing oxygen for this stepped surface indicate that activation energies and preexponential factors depend strongly on oxygen pressure, a factor that has not previously been considered critical for CO oxidation on platinum. As oxygen pressure is increased from 10(-6) to 0.002 Torr, the oxidation activation energies for the saturated CO monolayer decrease from 24.1 to 13.5 kcal/mol for reaction over the 0.95-0.90 ML CO coverage range. This dramatic decrease in activation energy is associated with a simple increase in oxygen pressure from 10(-5) to 10(-3) Torr. Activation energies as low as 7.8 kcal/mol were observed for oxidation of an initially saturated CO layer reacting over the 0.4-0.25 ML coverage range in oxygen pressure of 0.002 Torr. These dramatic changes in reaction mechanism with oxygen pressure for stepped surfaces are consistent with mechanistic models involving transient low activation energy

  5. Enhancement of Electrochemical Performance by the Oxygen Vacancies in Hematite as Anode Material for Lithium-Ion Batteries.

    PubMed

    Zeng, Peiyuan; Zhao, Yueying; Lin, Yingwu; Wang, Xiaoxiao; Li, Jianwen; Wang, Wanwan; Fang, Zhen

    2017-12-01

    The application of hematite in lithium-ion batteries (LIBs) has been severely limited because of its poor cycling stability and rate performance. To solve this problem, hematite nanoparticles with oxygen vacancies have been rationally designed by a facile sol-gel method and a sequential carbon-thermic reduction process. Thanks to the existence of oxygen vacancies, the electrochemical performance of the as-obtained hematite nanoparticles is greatly enhancing. When used as the anode material in LIBs, it can deliver a reversible capacity of 1252 mAh g(-1) at 2 C after 400 cycles. Meanwhile, the as-obtained hematite nanoparticles also exhibit excellent rate performance as compared to its counterparts. This method not only provides a new approach for the development of hematite with enhanced electrochemical performance but also sheds new light on the synthesis of other kinds of metal oxides with oxygen vacancies.

  6. Enhancement of Electrochemical Performance by the Oxygen Vacancies in Hematite as Anode Material for Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Zeng, Peiyuan; Zhao, Yueying; Lin, Yingwu; Wang, Xiaoxiao; Li, Jianwen; Wang, Wanwan; Fang, Zhen

    2017-01-01

    The application of hematite in lithium-ion batteries (LIBs) has been severely limited because of its poor cycling stability and rate performance. To solve this problem, hematite nanoparticles with oxygen vacancies have been rationally designed by a facile sol-gel method and a sequential carbon-thermic reduction process. Thanks to the existence of oxygen vacancies, the electrochemical performance of the as-obtained hematite nanoparticles is greatly enhancing. When used as the anode material in LIBs, it can deliver a reversible capacity of 1252 mAh g-1 at 2 C after 400 cycles. Meanwhile, the as-obtained hematite nanoparticles also exhibit excellent rate performance as compared to its counterparts. This method not only provides a new approach for the development of hematite with enhanced electrochemical performance but also sheds new light on the synthesis of other kinds of metal oxides with oxygen vacancies.

  7. Ames Hybrid Combustion Facility

    NASA Technical Reports Server (NTRS)

    Zilliac, Greg; Karabeyoglu, Mustafa A.; Cantwell, Brian; Hunt, Rusty; DeZilwa, Shane; Shoffstall, Mike; Soderman, Paul T.; Bencze, Daniel P. (Technical Monitor)

    2003-01-01

    The report summarizes the design, fabrication, safety features, environmental impact, and operation of the Ames Hybrid-Fuel Combustion Facility (HCF). The facility is used in conducting research into the scalability and combustion processes of advanced paraffin-based hybrid fuels for the purpose of assessing their applicability to practical rocket systems. The facility was designed to deliver gaseous oxygen at rates between 0.5 and 16.0 kg/sec to a combustion chamber operating at pressures ranging from 300 to 900. The required run times were of the order of 10 to 20 sec. The facility proved to be robust and reliable and has been used to generate a database of regression-rate measurements of paraffin at oxygen mass flux levels comparable to those of moderate-sized hybrid rocket motors.

  8. Combustion Processes in the Aerospace Environment

    NASA Technical Reports Server (NTRS)

    Huggett, Clayton

    1969-01-01

    The aerospace environment introduces new and enhanced fire hazards because the special atmosphere employed may increase the frequency and intensity of fires, because the confinement associated with aerospace systems adversely affects the dynamics of fire development and control, and because the hostile external environments limit fire control and rescue operations. Oxygen enriched atmospheres contribute to the fire hazard in aerospace systems by extending the list of combustible fuels, increasing the probability of ignition, and increasing the rates of fire spread and energy release. A system for classifying atmospheres according to the degree of fire hazard, based on the heat capacity of the atmosphere per mole of oxygen, is suggested. A brief exploration of the dynamics of chamber fires shows that such fires will exhibit an exponential growth rate and may grow to dangerous size in a very short time. Relatively small quantities of fuel and oxygen can produce a catastrophic fire in a closed chamber.

  9. Phase Transformations of Cobalt Oxides in CoxOy-ZnO Multipod Nanostructures via Combustion from Thermopower Waves.

    PubMed

    Lee, Kang Yeol; Hwang, Hayoung; Choi, Wonjoon

    2015-09-01

    The study of combustion at the interfaces of materials and chemical fuels has led to developments in diverse fields such as materials chemistry and energy conversion. Recently, it has been suggested that thermopower waves can utilize chemical-thermal-electrical-energy conversion in hybrid structures comprising nanomaterials and combustible fuels to produce enhanced combustion waves with concomitant voltage generation. In this study, this is the first time that the direct phase transformation of Co-doped ZnO via instant combustion waves and its applications to thermopower waves is presented. It is demonstrated that the chemical combustion waves at the surfaces of Co3O4-ZnO multipod nanostructures (deep brown in color) enable direct phase transformations to newly formed CoO-ZnO(1-x) nanoparticles (olive green in color). The oxygen molecules are released from Co3O4-ZnO to CoO-ZnO(1-x) under high-temperature conditions in the reaction front regime in combustion, whereas the CoO-ZnO multipod nanoparticles do not undergo any transformations and thus do not experience any color change. This oxygen-release mechanism is applicable to thermopower waves, enhances the self-propagating combustion velocity, and forms lattice defects that interrupt the charge-carrier movements inside the nanostructures. The chemical transformation and corresponding energy transport observed in this study can contribute to diverse potential applications, including direct-combustion synthesis and energy conversion.

  10. Low oxygen tension enhances the generation of lung progenitor cells from mouse embryonic and induced pluripotent stem cells

    PubMed Central

    Garreta, Elena; Melo, Esther; Navajas, Daniel; Farré, Ramon

    2014-01-01

    Abstract Whole‐organ decellularization technology has emerged as a new alternative for the fabrication of bioartificial lungs. Embryonic stem cells (ESC) and induced pluripotent stem cells (iPSC) are potentially useful for recellularization since they can be directed to express phenotypic marker genes of lung epithelial cells. Normal pulmonary development takes place in a low oxygen environment ranging from 1 to 5%. By contrast, in vitro ESC and iPSC differentiation protocols are usually carried out at room‐air oxygen tension. Here, we sought to determine the role played by oxygen tension on the derivation of Nkx2.1+ lung/thyroid progenitor cells from mouse ESC and iPSC. A step‐wise differentiation protocol was used to generate Nkx2.1+ lung/thyroid progenitors under 20% and 5% oxygen tension. On day 12, gene expression analysis revealed that Nkx2.1 and Foxa2 (endodermal and early lung epithelial cell marker) were significantly upregulated at 5% oxygen tension in ESC and iPSC differentiated cultures compared to 20% oxygen conditions. In addition, quantification of Foxa2+Nkx2.1+Pax8‐ cells corresponding to the lung field, with exclusion of the potential thyroid fate identified by Pax8 expression, confirmed that the low physiologic oxygen tension exerted a significant positive effect on early pulmonary differentiation of ESC and iPSC. In conclusion, we found that 5% oxygen tension enhanced the derivation of lung progenitors from mouse ESC and iPSC compared to 20% room‐air oxygen tension. PMID:25347858

  11. Visible light-induced singlet oxygen-mediated intracellular disassembly of polymeric micelles co-loaded with a photosensitizer and an anticancer drug for enhanced photodynamic therapy.

    PubMed

    Saravanakumar, Gurusamy; Lee, Junseok; Kim, Jihoon; Kim, Won Jong

    2015-06-21

    Herein, we report a biocompatible amphiphilic block copolymer micelle bearing a singlet oxygen-sensitive vinyldithioether cleavable linker at the core-shell junction, which undergoes singlet oxygen-mediated photocleavage in the presence of visible light. The micelle facilitates the light-responsive release of singlet oxygen and an anticancer drug for enhanced photodynamic therapy.

  12. Oxygen enhancement ratio for d(800) + (Be + Ta) and d(800) + (Ta + Be) neutrons

    SciTech Connect

    Harrison, G.H.; Balcer-Kubiczek, E.K.

    1980-07-01

    Specialized experiments were performed to determine whether the neutron oxygen enhancement ratio (OER) changes significantly as the mean energy increases above 25 MeV. The experimental design called for OER measurements at two energies in the same experiment. The neutron production reaction d(80) + (Be + Ta) generated a beam with mean energy 38 MeV; upon rotation of the target, d(80) + (Ta + Be) neutrons were generated with mean energy 25 MeV. Suspensions of the bacterium Serratia marcesens were irradiated in oxic-hypoxic pairs, alternately with high- and lower-energy neutrons. Replicate experiments yielded OER values and 95% confidence limits of 2.25 (2.05, 2.50) at 25 MeV and 1.67 (1.57, 1.79) at 38 MeV. The x-ray OER was 3.3 (3.1, 3.5). The significant decrease in OER supports our results with Vicia faba showing OER values of 1.7, 1.4, and 2.6 for 25- and 38-MeV neutrons and for x rays, respectively. The yield of spallation products with mass number 6, 7, 9, 10, and 11 arising from neutrons interacting in tissue was analyzed. The tissue kerma from such product contribute kerma equal to 15 to 30% of the recoil proton kerma and thus may provide the physical basis for the observed OER reduction at high neutron energies.

  13. Enhanced electrocatalytic performance of Pt monolayer on nanoporous PdCu alloy for oxygen reduction

    NASA Astrophysics Data System (ADS)

    Hou, Linxi; Qiu, Huajun

    2012-10-01

    By selectively dealloying Al from PdxCu20-xAl80 ternary alloys in 1.0 M NaOH solution, nanoporous PdCu (np-PdCu) alloys with different Pd:Cu ratios are obtained. By a mild electrochemical dealloying treatment, the np-PdCu alloys are facilely converted into np-PdCu near-surface alloys with a nearly pure-Pd surface and PdCu alloy core. The np-PdCu near-surface alloys are then used as substrates to fabricate core-shell catalysts with a Pt monolayer as shell and np-PdCu as core by a Cu-underpotential deposition-Pt displacement strategy. Electrochemical measurements demonstrate that the Pt monolayer on np-Pd1Cu1 (Pt/np-Pd1Cu1) exhibits the highest Pt surface-specific activity towards oxygen reduction, which is ˜5.8-fold that of state-of-the-art Pt/C catalyst. The Pt/np-Pd1Cu1 also shows much enhanced stability with ˜78% active surface retained after 10,000 cycles (0.6-1.2 V vs. RHE). Under the same condition, the active surface of Pt/C drops to ˜28%.

  14. Iridium-Tin oxide solid-solution nanocatalysts with enhanced activity and stability for oxygen evolution

    NASA Astrophysics Data System (ADS)

    Li, Guangfu; Yu, Hongmei; Yang, Donglei; Chi, Jun; Wang, Xunying; Sun, Shucheng; Shao, Zhigang; Yi, Baolian

    2016-09-01

    Addressing major challenges from the material cost, efficiency and stability, it is highly desirable to develop high-performance catalysts for oxygen evolution reaction (OER). Herein we explore a facile surfactant-assisted approach for fabricating Irsbnd Sn (Ir/Sn = 0.6/0.4, by mol.) nano-oxide catalysts with good morphology control. Direct proofs from XRD and X-ray photoelectron spectra indicate hydrophilic triblock polymer (TBP, like Pluronic® F108) surfactant can boost the formation of stable solid-solution structure. With the TBP hydrophilic and block-length increase, the fabricated Irsbnd Sn oxides undergoing the rod-to-sphere transition obtain the relatively lower crystallization, decreased crystallite size, Ir-enriched surface and incremental available active sites, all of which can bolster the OER activity and stability. Meanwhile, it is observed that the coupled Ir oxidative etching takes a crucial role in determining the material structure and performance. Compared with commercial Ir black, half-cell tests confirm F108-assistant catalysts with over 40 wt% Ir loading reduction show 2-fold activity enhancement as well as significant stability improvement. The lowest cell voltage using 0.88 mg cm-2 Ir loading is only 1.621 V at 1000 mA cm-2 and 80 °C with a concomitant energy efficiency of 75.8% which is beyond the DOE 2017 efficiency target of 74%.

  15. Enhancing pyridinic nitrogen level in graphene to promote electrocatalytic activity for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Sun, Jiaguang; Wang, Lan; Song, Ranran; Yanga, Shubin

    2016-02-01

    We develop an efficient approach to fabricate nitrogen-doped graphene with tunable pyridinic nitrogen levels (from 1.1 to 1.8 at.%), abundant in-plane holes and high surface areas (623 m2 g-1) via a hydrothermal treatment of graphene oxide with hydrogen peroxide and subsequent annealing under ammonia gas. It is found that the chemical etching is beneficial to the formation of pyridinic nitrogen in graphene during the nitrogen-doping process, which is crucial to enhancing the electrocatalytic properties of graphene for oxygen reduction reaction (ORR). Hence, the optimized NG exhibits good electrocatalytic activity, more positive onset potential than Pt-C (-0.08 V versus -0.09 V), good durability, and high selectivity when it is employed as a metal-free catalyst for ORR. This approach may uncover a mechanism in escalation of pyridinic N atoms doped on the graphene basal edge and provide an efficient platform for the synthesis of a series of heteroatom-doped graphene with tunable heteroatom content for broad applications.

  16. Enhanced oxygen reduction performance by novel pyridine substituent groups of iron (II) phthalocyanine with graphene composite

    NASA Astrophysics Data System (ADS)

    Cui, Lili; Lv, Guojun; He, Xingquan

    2015-05-01

    In this paper, a novel iron (II) tetrapyridyloxyphthalocyanine decorated graphene (FeTPPc/Gr) is synthesized through a simple solvothermal method. The catalytic performance of the fabricated FeTPPc/Gr for the oxygen reduction reaction (ORR) is accessed by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and i-t chronoamperometry methods. The FeTPPc/Gr composite catalyst for the ORR displays an enhanced electrocatalytic activity compared with other FePc/Gr catalysts. More importantly, the proposed FeTPPc/Gr catalyst towards the ORR outperforms the commercial Pt/C catalyst in terms of higher diffusion-limiting current, more positive onset potential and half-wave potential, better stability and tolerance to methanol crossover. The improved ORR performance is attributed to the activity of peripheral pyridine substituents in the FePc, which facilitate O2 absorption and increase the additional active sites. Based on our experimental results, designing novel metal-N4 macrocycles and incorporating them into graphene or graphene derivatives, with both optimal activity and durability for the ORR, may hold great promise for application in alkaline direct methanol fuel cells (DMFCs).

  17. Determining Heats of Combustion of Gaseous Hydrocarbons

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Sprinkle, Danny R.; Puster, Richard L.

    1987-01-01

    Enrichment-oxygen flow rate-ratio related to heat of combustion. Technique developed for determining heats of combustion of natural-gas samples. Based on measuring ratio m/n, where m is (volmetric) flow rate of oxygen required to enrich carrier air in which test gas flowing at rate n is burned, such that mole fraction of oxygen in combustion-product gases equals that in carrier air. The m/n ratio directly related to heats of combustion of saturated hydrocarbons present in natural gas.

  18. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction

    PubMed Central

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-01-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd2+ ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction. PMID:27079897

  19. Cage-bell Pt-Pd nanostructures with enhanced catalytic properties and superior methanol tolerance for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Chen, Dong; Ye, Feng; Liu, Hui; Yang, Jun

    2016-04-01

    Precisely tailoring the structure and fully making use of the components of nanoparticles are effective to enhance their catalytic performance for a given reaction. We herein demonstrate the design of cage-bell structured Pt-Pd nanoparticles, where a Pd shell is deliberately selected to enhance the catalytic property and methanol tolerance of Pt for oxygen reduction reaction. This strategy starts with the synthesis of core-shell Pt@Ag nanoparticles, followed by galvanic replacement reaction between the Ag shell and Pd2+ ions to form core-shell-shell Pt@Ag@Ag-Pd nanoparticles with a Pt core and double shells composed of Ag at inner and alloy Ag-Pd at outer, respectively. Then, the core-shell-shell templates are agitated with saturated NaCl solution to eliminate the Ag component from the double shells, leading to the formation of bimetallic Pt-Pd nanoparticles with a cage-bell structure, defined as a movable Pt core enclosed by a porous Pd shell, which show enhanced catalytic activity for oxygen reduction compared with that of the Pt seeds due to the additional catalysis from Pd shell. In addition, owing to the different diffusion behavior of methanol and oxygen molecules in the porous Pd shell, the Pt-Pd cage-bell nanostructures also exhibit superior methanol tolerant property in catalyzing the oxygen reduction.

  20. Autoxidation in amide-based electrolyte and its suppression for enhanced oxygen efficiency and cycle performance in non-aqueous lithium oxygen battery

    NASA Astrophysics Data System (ADS)

    Kim, Dong Wook; Lee, Dong Hun; Ahn, Su Mi; Kim, Do Youb; Suk, Jungdon; Choi, Dong Hoon; Kang, Yongku

    2017-04-01

    In spite of several desirable properties such as high stability against superoxide anion and low vapor pressure, N-methyl-2-pyrrolidone (NMP) electrolyte is reported not suitable for use in lithium-oxygen (Li-O2) batteries because of severe degradation upon cycling and low oxygen efficiency. In this work, we find that NMP electrolyte is reactive with O2 gas in the presence of lithium metal and such O2-consuming reaction (i.e., autoxidation) is a possible cause for the poor performance in Li-O2 batteries with NMP electrolyte. The autoxidation of NMP is verified by direct measurement of the depletion of O2 gas in the hermetically sealed symmetric Li/Li cells via in-situ gas pressure analysis. In-situ differential electrochemical mass spectroscopy (DEMS) experiment reveals that the autoxidation resulted in significant O2 consumption upon discharge, very low O2 efficiency upon charge, and eventually fast capacity fading. Lithium nitrate (LiNO3), which provides a protective layer on the surface of lithium metal, is employed to suppress the autoxidation, leading to significantly enhanced oxygen efficiency and cycle life.

  1. Combustion noise

    NASA Technical Reports Server (NTRS)

    Strahle, W. C.

    1977-01-01

    A review of the subject of combustion generated noise is presented. Combustion noise is an important noise source in industrial furnaces and process heaters, turbopropulsion and gas turbine systems, flaring operations, Diesel engines, and rocket engines. The state-of-the-art in combustion noise importance, understanding, prediction and scaling is presented for these systems. The fundamentals and available theories of combustion noise are given. Controversies in the field are discussed and recommendations for future research are made.

  2. Low oxygen levels as a trigger for enhancement of respiratory metabolism in Saccharomyces cerevisiae

    PubMed Central

    Rintala, Eija; Toivari, Mervi; Pitkänen, Juha-Pekka; Wiebe, Marilyn G; Ruohonen, Laura; Penttilä, Merja

    2009-01-01

    Background The industrially important yeast Saccharomyces cerevisiae is able to grow both in the presence and absence of oxygen. However, the regulation of its metabolism in conditions of intermediate oxygen availability is not well characterised. We assessed the effect of oxygen provision on the transcriptome and proteome of S. cerevisiae in glucose-limited chemostat cultivations in anaerobic and aerobic conditions, and with three intermediate (0.5, 1.0 and 2.8% oxygen) levels of oxygen in the feed gas. Results The main differences in the transcriptome were observed in the comparison of fully aerobic, intermediate oxygen and anaerobic conditions, while the transcriptome was generally unchanged in conditions receiving different intermediate levels (0.5, 1.0 or 2.8% O2) of oxygen in the feed gas. Comparison of the transcriptome and proteome data suggested post-transcriptional regulation was important, especially in 0.5% oxygen. In the conditions of intermediate oxygen, the genes encoding enzymes of the respiratory pathway were more highly expressed than in either aerobic or anaerobic conditions. A similar trend was also seen in the proteome and in enzyme activities of the TCA cycle. Further, genes encoding proteins of the mitochondrial translation machinery were present at higher levels in all oxygen-limited and anaerobic conditions, compared to fully aerobic conditions. Conclusion Global upregulation of genes encoding components of the respiratory pathway under conditions of intermediate oxygen suggested a regulatory mechanism to control these genes as a response to the need of more efficient energy production. Further, cells grown in three different intermediate oxygen levels were highly similar at the level of transcription, while they differed at the proteome level, suggesting post-transcriptional mechanisms leading to distinct physiological modes of respiro-fermentative metabolism. PMID:19804647

  3. Combustion of White Phosphorus

    NASA Astrophysics Data System (ADS)

    Keiter, Richard L.; Gamage, Chaminda P.

    2001-07-01

    The reaction of white phosphorus with pure oxygen is conveniently and safely demonstrated by carrying out the reaction in a retort that has its open end submerged in water. After filling the retort with oxygen gas, a small amount of white phosphorus is introduced and heated with a hot-plate until it ignites. The spectacular reaction leads to consumption and expulsion of oxygen gas, creation of a partial vacuum in the retort, and back suction of water that extinguishes the combustion. Featured on the Cover

  4. Oxygen-enhanced in situ bioremediation in a sand and gravel aquifer

    SciTech Connect

    Carter, S.R.; Clark, J.E.

    1995-12-31

    In situ bioremediation was chosen to remediate shallow oxygen-limited groundwater contaminated with volatile and semivolatile aromatic hydrocarbons from a fuel release. The remediation system included groundwater recovery at rates up to 100 L/min and treatment with a packed-tower air stripper to remove volatiles and increase dissolved oxygen levels. Dissolved oxygen was further increased using a pressure-swing adsorption (PSA) oxygen generator and hollow-fiber oxygen dissolution membranes. This oxygenated water was injected back to the subsurface through two horizontal injection galleries. Prior to start-up of the remediation system, groundwater in contaminated wells was oxygen-limited, with levels from 0 to less than 1 mg/L. After several months of groundwater injection, dissolved oxygen levels began to increase in contaminated wells by 1 to 2 mg/L. A significant decrease in dissolved-phase hydrocarbons was observed in a well nearest an injection gallery once dissolved oxygen was increased to background levels. A decrease in nitrogen was also observed, suggesting that aerobic biodegradation was a significant factor in the hydrocarbon decrease.

  5. CHARACTERIZATION OF MERCURY-ENRICHED COAL COMBUSTION RESIDUES FROM ELECTRIC UTILITIES USING ENHANCED SORBENTS FOR MERCURY CONTROL

    EPA Science Inventory

    Leaching of mercury and other constituents of potential concern during land disposal or beneficial use of coal combustion residues (CCRs) is the environmental impact pathway evaluated in this report. The specific objectives of the research was to: (1) evaluate mercury, arsenic an...

  6. Central enhancement of the nitrogen-to-oxygen abundance ratio in barred galaxies

    NASA Astrophysics Data System (ADS)

    Florido, E.; Zurita, A.; Pérez, I.; Pérez-Montero, E.; Coelho, P. R. T.; Gadotti, D. A.

    2015-12-01

    Context. Bar-induced gas inflows towards galaxy centres are recognised as a key agent for the secular evolution of galaxies. One immediate consequence of this inflow is the accumulation of gas in the centre of galaxies where it can form stars and alter the chemical and physical properties. Aims: Our aim is to study whether the properties of the ionised gas in the central parts of barred galaxies are altered by the presence of a bar and whether the change in central properties is related to bar and/or parent galaxy properties. Methods: We use a sample of nearby face-on disc galaxies with available SDSS spectra, morphological decomposition, and information on the stellar population of their bulges, to measure the internal Balmer extinction from the Hα to Hβ line ratio, star formation rate, and relevant line ratios to diagnose chemical abundances and gas density. Results: The distributions of all the parameters analysed (internal Balmer extinction at Hβ (c(Hβ)), star formation rate per unit area, electron density, [N ii]λ6583/Hα emission-line ratio, ionisation parameter, and nitrogen-to-oxygen (N/O) abundance ratio) are different for barred and unbarred galaxies, except for the R23 metallicity tracer and the oxygen abundance obtained from photoionisation models. The median values of the distributions of these parameters point towards (marginally) larger dust content, star formation rate per unit area, electron density, and ionisation parameter in the centres of barred galaxies than in their unbarred counterparts. The most remarkable difference between barred and unbarred galaxies appears in the [N ii]λ6583/Hα line ratio that is, on average, ~25% higher in barred galaxies, due to an increased N/O abundance ratio in the centres of these galaxies compared to the unbarred ones. We analyse these differences as a function of galaxy morphological type (as traced by bulge-to-disc light ratios and bulge mass), total stellar mass, and bulge Sérsic index. We observe an

  7. Surface cleaning for enhanced adhesion to packaging surfaces: Effect of oxygen and ammonia plasma

    SciTech Connect

    Gaddam, Sneha; Dong, Bin; Driver, Marcus; Kelber, Jeffry; Kazi, Haseeb

    2015-03-15

    The effects of direct plasma chemistries on carbon removal from silicon nitride (SiN{sub x}) and oxynitride (SiO{sub x}N{sub y}) surfaces have been studied by in-situ x-ray photoelectron spectroscopy (XPS) and ex-situ contact angle measurements. The data indicate that O{sub 2} and NH{sub 3} capacitively coupled plasmas are effective at removing adventitious carbon from silicon nitride (SiN{sub x}) and Si oxynitride (SiO{sub x}N{sub y}) surfaces. O{sub 2} plasma treatment results in the formation of a silica overlayer. In contrast, the exposure to NH{sub 3} plasma results in negligible additional oxidation of the SiN{sub x} or SiO{sub x}N{sub y} surface. Ex-situ contact angle measurements show that SiN{sub x} and SiO{sub x}N{sub y} surfaces exposed to oxygen plasma are initially more hydrophilic than surfaces exposed to NH{sub 3} plasma, indicating that the O{sub 2} plasma-induced SiO{sub 2} overlayer is highly reactive toward ambient. At longer ambient exposures (≳10 h), however, surfaces treated by either O{sub 2} or NH{sub 3} plasma exhibit similar steady state contact angles, correlated with rapid uptake of adventitious carbon, as determined by XPS. Surface passivation by exposure to molecular hydrogen prior to ambient exposure significantly retards the increase in contact angle upon exposure to ambient. The results suggest a practical route to enhancing the time available for effective bonding to surfaces in microelectronics packaging applications.

  8. Enhanced Cell Capture on Functionalized Graphene Oxide Nanosheets through Oxygen Clustering.

    PubMed

    Bardhan, Neelkanth M; Kumar, Priyank V; Li, Zeyang; Ploegh, Hidde L; Grossman, Jeffrey C; Belcher, Angela M; Chen, Guan-Yu

    2017-02-28

    With the global rise in incidence of cancer and infectious diseases, there is a need for the development of techniques to diagnose, treat, and monitor these conditions. The ability to efficiently capture and isolate cells and other biomolecules from peripheral whole blood for downstream analyses is a necessary requirement. Graphene oxide (GO) is an attractive template nanomaterial for such biosensing applications. Favorable properties include its two-dimensional architecture and wide range of functionalization chemistries, offering significant potential to tailor affinity toward aromatic functional groups expressed in biomolecules of interest. However, a limitation of current techniques is that as-synthesized GO nanosheets are used directly in sensing applications, and the benefits of their structural modification on the device performance have remained unexplored. Here, we report a microfluidic-free, sensitive, planar device on treated GO substrates to enable quick and efficient capture of Class-II MHC-positive cells from murine whole blood. We achieve this by using a mild thermal annealing treatment on the GO substrates, which drives a phase transformation through oxygen clustering. Using a combination of experimental observations and MD simulations, we demonstrate that this process leads to improved reactivity and density of functionalization of cell capture agents, resulting in an enhanced cell capture efficiency of 92 ± 7% at room temperature, almost double the efficiency afforded by devices made using as-synthesized GO (54 ± 3%). Our work highlights a scalable, cost-effective, general approach to improve the functionalization of GO, which creates diverse opportunities for various next-generation device applications.

  9. Curcumin enhances the cytogenotoxic effect of etoposide in leukemia cells through induction of reactive oxygen species

    PubMed Central

    Papież, Monika A; Krzyściak, Wirginia; Szade, Krzysztof; Bukowska-Straková, Karolina; Kozakowska, Magdalena; Hajduk, Karolina; Bystrowska, Beata; Dulak, Jozef; Jozkowicz, Alicja

    2016-01-01

    Curcumin may exert a more selective cytotoxic effect in tumor cells with elevated levels of free radicals. Here, we investigated whether curcumin can modulate etoposide action in myeloid leukemia cells and in normal cells of hematopoietic origin. HL-60 cell line, normal myeloid progenitor cluster of differentiation (CD)-34+ cells, and granulocytes were incubated for 4 or 24 hours at different concentrations of curcumin and/or etoposide. Brown Norway rats with acute myeloid leukemia (BNML) were used to prove the influence of curcumin on etoposide action in vivo. Rats were treated with curcumin for 23 days and etoposide was administered for the final 3 days of the experiment. Curcumin synergistically potentiated the cytotoxic effect of etoposide, and it intensified apoptosis and phosphorylation of the histone H2AX induced by this cytostatic drug in leukemic HL-60 cells. In contrast, curcumin did not significantly modify etoposide-induced cytotoxicity and H2AX phosphorylation in normal CD34+ cells and granulocytes. Curcumin modified the cytotoxic action of etoposide in HL-60 cells through intensification of free radical production because preincubation with N-acetyl-l-cysteine (NAC) significantly reduced the cytotoxic effect of curcumin itself and a combination of two compounds. In contrast, NAC did not decrease the cytotoxic effect of etoposide. Thus, oxidative stress plays a greater role in the cytotoxic effect of curcumin than that of etoposide in HL-60 cells. In vitro results were confirmed in a BNML model. Pretreatment with curcumin enhanced the antileukemic activity of etoposide in BNML rats (1.57-fold tumor reduction versus etoposide alone; P<0.05) and induced apoptosis of BNML cells more efficiently than etoposide alone (1.54-fold change versus etoposide alone; P<0.05), but this treatment protected nonleukemic B-cells from apoptosis. Thus, curcumin can increase the antileukemic effect of etoposide through reactive oxygen species in sensitive myeloid leukemia

  10. Enhanced singlet oxygen production by photodynamic therapy and a novel method for its intracellular measurement.

    PubMed

    Pena Luengas, Sandra L; Marin, Gustavo Horacio; Aviles, Kevin; Cruz Acuña, Ricardo; Roque, Gustavo; Rodríguez Nieto, Felipe; Sanchez, Francisco; Tarditi, Adrián; Rivera, Luis; Mansilla, Eduardo

    2014-12-01

    The generation of singlet oxygen (SO) in the presence of specific photosensitizers (PSs) or semiconductor quantum dots (QDs) and its application in photodynamic therapy (PDT) is of great interest to develop cancer therapies with no need of surgery, chemotherapy, and/or radiotherapy. This work was focused on the identification of the main factors leading to the enhancement of SO production using Rose Bengal (RB), and Methylene Blue (MB) as PS species in organic and aqueous mediums. Subsequently, the capacity of zinc oxide (ZnO), zinc sulfide (ZnS), and ZnO/ZnS core-shell QDs as well as manganese (Mn(+2)) doped ZnO and ZnS nanoparticles (NPs) as potential PS was also investigated. Many variable parameters such as type of quencher, PSs, NPs, as well as its different concentrations, light source, excitation wavelength, reaction time, distance from light source, and nature of solvent were used. The degradation kinetics of the quenchers generated by SO species and the corresponding quantum yields were determined by monitoring the photo-oxidation of the chemical quencher and measuring its disappearance by fluorometry and spectrophotometry in the presence of NPs. Small intracellular changes of SO induced by these metal Zn (zinc) NPs and PDT could execute and accelerate deadly programs in these leukemic cells, providing in this way an innovative modality of treatment. In order to perform further more specific in vitro cytotoxic studies on B-chronic lymphocytic leukemia cells exposed to Zn NPs and PDT, we needed first to measure and ascertain those possible intracellular SO variations generated by this type of treatment; for this purpose, we have also developed and tested a novel method first described by us.

  11. Enhanced Singlet Oxygen Production by Photodynamic Therapy and a Novel Method for Its Intracellular Measurement

    PubMed Central

    Marin, Gustavo Horacio; Aviles, Kevin; Acuña, Ricardo Cruz; Roque, Gustavo; Nieto, Felipe Rodríguez; Sanchez, Francisco; Tarditi, Adrián; Rivera, Luis; Mansilla, Eduardo

    2014-01-01

    Abstract The generation of singlet oxygen (SO) in the presence of specific photosensitizers (PSs) or semiconductor quantum dots (QDs) and its application in photodynamic therapy (PDT) is of great interest to develop cancer therapies with no need of surgery, chemotherapy, and/or radiotherapy. This work was focused on the identification of the main factors leading to the enhancement of SO production using Rose Bengal (RB), and Methylene Blue (MB) as PS species in organic and aqueous mediums. Subsequently, the capacity of zinc oxide (ZnO), zinc sulfide (ZnS), and ZnO/ZnS core-shell QDs as well as manganese (Mn+2) doped ZnO and ZnS nanoparticles (NPs) as potential PS was also investigated. Many variable parameters such as type of quencher, PSs, NPs, as well as its different concentrations, light source, excitation wavelength, reaction time, distance from light source, and nature of solvent were used. The degradation kinetics of the quenchers generated by SO species and the corresponding quantum yields were determined by monitoring the photo-oxidation of the chemical quencher and measuring its disappearance by fluorometry and spectrophotometry in the presence of NPs. Small intracellular changes of SO induced by these metal Zn (zinc) NPs and PDT could execute and accelerate deadly programs in these leukemic cells, providing in this way an innovative modality of treatment. In order to perform further more specific in vitro cytotoxic studies on B-chronic lymphocytic leukemia cells exposed to Zn NPs and PDT, we needed first to measure and ascertain those possible intracellular SO variations generated by this type of treatment; for this purpose, we have also developed and tested a novel method first described by us. PMID:25490599

  12. Enhanced brain stem 5HT₂A receptor function under neonatal hypoxic insult: role of glucose, oxygen, and epinephrine resuscitation.

    PubMed

    Anju, T R; Korah, P K; Jayanarayanan, S; Paulose, C S

    2011-08-01

    Molecular processes regulating brain stem serotonergic receptors play an important role in the control of respiration. We evaluated 5-HT(2A) receptor alterations in the brain stem of neonatal rats exposed to hypoxic insult and the effect of glucose, oxygen, and epinephrine resuscitation in ameliorating these alterations. Hypoxic stress increased the total 5-HT and 5-HT(2A) receptor number along with an up regulation of 5-HT Transporter and 5-HT(2A) receptor gene in the brain stem of neonates. These serotonergic alterations were reversed by glucose supplementation alone and along with oxygen to hypoxic neonates. The enhanced brain stem 5-HT(2A) receptors act as a modulator of ventilatory response to hypoxia, which can in turn result in pulmonary vasoconstriction and cognitive dysfunction. The adverse effects of 100% oxygenation and epinephrine administration to hypoxic neonates were also reported. This has immense clinical significance in neonatal care.

  13. Self-Monitoring Artificial Red Cells with Sufficient Oxygen Supply for Enhanced Photodynamic Therapy

    NASA Astrophysics Data System (ADS)

    Luo, Zhenyu; Zheng, Mingbin; Zhao, Pengfei; Chen, Ze; Siu, Fungming; Gong, Ping; Gao, Guanhui; Sheng, Zonghai; Zheng, Cuifang; Ma, Yifan; Cai, Lintao

    2016-03-01

    Photodynamic therapy has been increasingly applied in clinical cancer treatments. However, native hypoxic tumoural microenvironment and lacking oxygen supply are the major barriers hindering photodynamic reactions. To solve this problem, we have developed biomimetic artificial red cells by loading complexes of oxygen-carrier (hemoglobin) and photosensitizer (indocyanine green) for boosted photodynamic strategy. Such nanosystem provides a coupling structure with stable self-oxygen supply and acting as an ideal fluorescent/photoacoustic imaging probe, dynamically monitoring the nanoparticle biodistribution and the treatment of PDT. Upon exposure to near-infrared laser, the remote-triggered photosensitizer generates massive cytotoxic reactive oxygen species (ROS) with sufficient oxygen supply. Importantly, hemoglobin is simultaneously oxidized into the more active and resident ferryl-hemoglobin leading to persistent cytotoxicity. ROS and ferryl-hemoglobin synergistically trigger the oxidative damage of xenograft tumour resulting in complete suppression. The artificial red cells with self-monitoring and boosted photodynamic efficacy could serve as a versatile theranostic platform.

  14. Hydrogen-Enhanced Lunar Oxygen Extraction and Storage Using Only Solar Power

    NASA Technical Reports Server (NTRS)

    Burton, rodney; King, Darren

    2013-01-01

    The innovation consists of a thermodynamic system for extracting in situ oxygen vapor from lunar regolith using a solar photovoltaic power source in a reactor, a method for thermally insulating the reactor, a method for protecting the reactor internal components from oxidation by the extracted oxygen, a method for removing unwanted chemical species produced in the reactor from the oxygen vapor, a method for passively storing the oxygen, and a method for releasing high-purity oxygen from storage for lunar use. Lunar oxygen exists in various types of minerals, mostly silicates. The energy required to extract the oxygen from the minerals is 30 to 60 MJ/kg O. Using simple heating, the extraction rate depends on temperature. The minimum temperature is approximately 2,500 K, which is at the upper end of available oven temperatures. The oxygen is released from storage in a purified state, as needed, especially if for human consumption. This method extracts oxygen from regolith by treating the problem as a closed batch cycle system. The innovation works equally well in Earth or Lunar gravity fields, at low partial pressure of oxygen, and makes use of in situ regolith for system insulation. The innovation extracts oxygen from lunar regolith using a method similar to vacuum pyrolysis, but with hydrogen cover gas added stoichiometrically to react with the oxygen as it is produced by radiatively heating regolith to 2,500 K. The hydrogen flows over and through the heating element (HE), protecting it from released oxygen. The H2 O2 heat of reaction is regeneratively recovered to assist the heating process. Lunar regolith is loaded into a large-diameter, low-height pancake reactor powered by photovoltaic cells. The reactor lid contains a 2,500 K HE that radiates downward onto the regolith to heat it and extract oxygen, and is shielded above by a multi-layer tungsten radiation shield. Hydrogen cover gas percolates through the perforated tungsten shielding and HE, preventing

  15. Oxygen-implanted induced formation of oxide layer enhances blood compatibility on titanium for biomedical applications.

    PubMed

    Hung, Wei-Chiang; Chang, Fang-Mo; Yang, Tzu-Sen; Ou, Keng-Liang; Lin, Che-Tong; Peng, Pei-Wen

    2016-11-01

    Titanium dioxide (TiO2) layers were prepared on a Ti substrate by using oxygen plasma immersion ion implantation (oxygen PIII). The surface chemical states, structure, and morphology of the layers were studied using X-ray photoelectron spectroscopy, X-ray diffraction, Raman microscopy, atomic force microscopy and scanning electron microscope. The mechanical properties, such as the Young's modulus and hardness, of the layers were investigated using nanoindentation testing. The Ti(4+) chemical state was determined to be present on oxygen-PIII-treated surfaces, which consisted of nanocrystalline TiO2 with a rutile structure. Compared with Ti substrates, the oxygen-PIII-treated surfaces exhibited decreased Young's moduli and hardness. Parameters indicating the blood compatibility of the oxygen-PIII-treated surfaces, including the clotting time and platelet adhesion and activation, were studied in vitro. Clotting time assays indicated that the clotting time of oxygen-PIII-treated surfaces was longer than that of the Ti substrate, which was associated with decreased fibrinogen adsorption. In conclusion, the surface characteristics and the blood compatibility of Ti implants can be modified and improved using oxygen PIII.

  16. Combining oxygen plasma treatment with anchorage of cationized gelatin for enhancing cell affinity of poly(lactide-co-glycolide).

    PubMed

    Shen, Hong; Hu, Xixue; Yang, Fei; Bei, Jianzhong; Wang, Shenguo

    2007-10-01

    Surface characteristics greatly influence attachment and growth of cells on biomaterials. Although polylactone-type biodegradable polymers have been widely used as scaffold materials for tissue engineering, lack of cell recognition sites, poor hydrophilicity and low surface energy lead to a bad cell affinity of the polymers, which limit the usage of polymers as scaffolds in tissue engineering. In the present study, surface of poly (L-lactide-co-glycolide) (PLGA) was modified by a method of combining oxygen plasma treatment with anchorage of cationized gelatin. Modification effect of the method was compared with other methods of oxygen plasma treatment, cationized gelatin or gelatin coating and combining oxygen plasma treatment with anchorage of gelatin. The change of surface property was compared by contact angles, surface energy, X-ray photoelectron spectra (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) measurement. The optimum oxygen pretreatment time determined by surface energy was 10 min when the power was 50 W and the oxygen pressure was 20 Pa. Analysis of the stability of gelatin and cationized gelatin anchored on PLGA by XPS, ATR-FTIR, contact angles and surface energy measurement indicated the cationized gelatin was more stable than gelatin. The result using mouse NIH 3T3 fibroblasts as model cells to evaluate cell affinity in vitro showed the cationized gelatin-anchored PLGA (OCG-PLGA) was more favorable for cell attachment and growth than oxygen plasma treated PLGA (O-PLGA) and gelatin-anchored PLGA (OG-PLGA). Moreover cell affinity of OCG-PLGA could match that of collagen-anchored PLGA (AC-PLGA). So the surface modification method combining oxygen plasma treatment with anchorage of cationized gelatin provides a universally effective way to enhance cell affinity of polylactone-type biodegradable polymers.

  17. 3-D CFD Simulation and Validation of Oxygen-Rich Hydrocarbon Combustion in a Gas-Centered Swirl Coaxial Injector using a Flamelet-Based Approach

    NASA Technical Reports Server (NTRS)

    Richardson, Brian; Kenny, Jeremy

    2015-01-01

    Injector design is a critical part of the development of a rocket Thrust Chamber Assembly (TCA). Proper detailed injector design can maximize propulsion efficiency while minimizing the potential for failures in the combustion chamber. Traditional design and analysis methods for hydrocarbon-fuel injector elements are based heavily on empirical data and models developed from heritage hardware tests. Using this limited set of data produces challenges when trying to design a new propulsion system where the operating conditions may greatly differ from heritage applications. Time-accurate, Three-Dimensional (3-D) Computational Fluid Dynamics (CFD) modeling of combusting flows inside of injectors has long been a goal of the fluid analysis group at Marshall Space Flight Center (MSFC) and the larger CFD modeling community. CFD simulation can provide insight into the design and function of an injector that cannot be obtained easily through testing or empirical comparisons to existing hardware. However, the traditional finite-rate chemistry modeling approach utilized to simulate combusting flows for complex fuels, such as Rocket Propellant-2 (RP-2), is prohibitively expensive and time consuming even with a large amount of computational resources. MSFC has been working, in partnership with Streamline Numerics, Inc., to develop a computationally efficient, flamelet-based approach for modeling complex combusting flow applications. In this work, a flamelet modeling approach is used to simulate time-accurate, 3-D, combusting flow inside a single Gas Centered Swirl Coaxial (GCSC) injector using the flow solver, Loci-STREAM. CFD simulations were performed for several different injector geometries. Results of the CFD analysis helped guide the design of the injector from an initial concept to a tested prototype. The results of the CFD analysis are compared to data gathered from several hot-fire, single element injector tests performed in the Air Force Research Lab EC-1 test facility

  18. Oxygen vacancy enhanced the room temperature ferromagnetism in Ni-doped TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Hou, D. L.; Meng, H. J.; Jia, L. Y.; Ye, X. J.; Zhou, H. J.; Li, X. L.

    2007-04-01

    Ni-doped TiO2 anatase thin films were fabricated by reactive magnetron sputtering on SiO2 substrates. The doping and annealing effects on structure and magnetism for the films have been systematically investigated. The results show that ferromagnetism originated from the doped matrix and enhancement (suppression) of ferromagnetism is strongly correlated with the increase (decrease) of oxygen vacancies in TiO2.

  19. ENHANCED BIOREMEDIATION UTILIZING HYDROGEN PEROXIDE AS A SUPPLEMENTAL SOURCE OF OXYGEN: A LABORATORY AND FIELD STUDY

    EPA Science Inventory

    Laboratory and field scale studies were conducted to investigate the feasibility of using hydrogen peroxide as a supplemental source of oxygen for bioremediation of an aviation gasoline fuel spill. Field samples of aviation gasoline contaminated aquifer material were artificially...

  20. Enhanced spin-orbit torques by oxygen incorporation in tungsten films

    NASA Astrophysics Data System (ADS)

    Demasius, Kai-Uwe; Phung, Timothy; Zhang, Weifeng; Hughes, Brian P.; Yang, See-Hun; Kellock, Andrew; Han, Wei; Pushp, Aakash; Parkin, Stuart S. P.

    2016-02-01

    The origin of spin-orbit torques, which are generated by the conversion of charge-to-spin currents in non-magnetic materials, is of considerable debate. One of the most interesting materials is tungsten, for which large spin-orbit torques have been found in thin films that are stabilized in the A15 (β-phase) structure. Here we report large spin Hall angles of up to approximately -0.5 by incorporating oxygen into tungsten. While the incorporation of oxygen into the tungsten films leads to significant changes in their microstructure and electrical resistivity, the large spin Hall angles measured are found to be remarkably insensitive to the oxygen-doping level (12-44%). The invariance of the spin Hall angle for higher oxygen concentrations with the bulk properties of the films suggests that the spin-orbit torques in this system may originate dominantly from the interface rather than from the interior of the films.

  1. Enhanced electrocatalysis of the oxygen reduction reaction based on pattering of platinum surfaces with cyanide.

    SciTech Connect

    Strmcnik, D.; Escudero-Escribano, M.; Kodama, K.; Stamenkovic, V. R.; Cuesta, A.; Markovic, N. M.; Materials Science Division; Inst. de Quimica Fisica; Toyota Central R&D Labs., Inc.

    2010-08-15

    The slow rate of the oxygen reduction reaction in the phosphoric acid fuel cell is the main factor limiting its wide application. Here, we present an approach that can be used for the rational design of cathode catalysts with potential use in phosphoric acid fuel cells, or in any environments containing strongly adsorbing tetrahedral anions. This approach is based on molecular patterning of platinum surfaces with cyanide adsorbates that can efficiently block the sites for adsorption of spectator anions while the oxygen reduction reaction proceeds unhindered. We also demonstrate that, depending on the supporting electrolyte anions and cations, on the same CN-covered Pt(111) surface, the oxygen reduction reaction activities can range from a 25-fold increase to a 50-fold decrease. This behaviour is discussed in the light of the role of covalent and non-covalent interactions in controlling the ensemble of platinum active sites required for high turn over rates of the oxygen reduction reaction.

  2. Enhanced electrocatalysis of the oxygen reduction reaction based on patterning of platinum surfaces with cyanide

    SciTech Connect

    Strmcnik, D.; Escudero, M.; Kodama, K.; Stamenkovic, V. R.; Cuesta, A.; Markovic, N. M.

    2010-10-01

    The slow rate of the oxygen reduction reaction in the phosphoric acid fuel cell is the main factor limiting its wide application. Here, we present an approach that can be used for the rational design of cathode catalysts with potential use in phosphoric acid fuel cells, or in any environments containing strongly adsorbing tetrahedral anions. This approach is based on molecular patterning of platinum surfaces with cyanide adsorbates that can efficiently block the sites for adsorption of spectator anions while the oxygen reduction reaction proceeds unhindered. We also demonstrate that, depending on the supporting electrolyte anions and cations, on the same CN-covered Pt(111) surface, the oxygen reduction reaction activities can range from a 25-fold increase to a 50-fold decrease. This behaviour is discussed in the light of the role of covalent and non-covalent interactions in controlling the ensemble of platinum active sites required for high turn over rates of the oxygen reduction reaction.

  3. Thermal Model of the Promoted Combustion Test

    NASA Technical Reports Server (NTRS)

    Jones, Peter D.

    1996-01-01

    Flammability of metals in high pressure, pure oxygen environments, such as rocket engine turbopumps, is commonly evaluated using the Promoted Combustion Test (PCT). The PCT emphasizes the ability of an ignited material to sustain combustion, as opposed to evaluating the sample's propensity to ignite in the first place. A common arrangement is a rod of the sample material hanging in a chamber in which a high pressure, pure oxygen environment is maintained. An igniter of some energetically combusting material is fixed to the bottom of the rod and fired. This initiates combustion, and the sample burns and melts at its bottom tip. A ball of molten material forms, and this ball detaches when it grows too large to be supported by surface tension with the rod. In materials which do not sustain combustion, the combustion then extinguishes. In materials which do sustain combustion, combustion re-initiates from molten residue left on the bottom of the rod, and the melt ball burns and grows until it detaches again. The purpose of this work is development of a PCT thermal simulation model, detailing phase change, melt detachment, and the several heat transfer modes. Combustion is modeled by a summary rate equation, whose parameters are identified by comparison to PCT results. The sensitivity of PCT results to various physical and geometrical parameters is evaluated. The identified combustion parameters may be used in design of new PCT arrangements, as might be used for flammability assessment in flow-dominated environments. The Haynes 214 nickel-based superalloy, whose PCT results are applied here, burns heterogeneously (fuel and oxidizer are of different phases; combustion takes place on the fuel surface). Heterogeneous combustion is not well understood. (In homogeneous combustion, the metal vaporizes, and combustion takes place in an analytically treatable cloud above the surface). Thermal modeling in heterogeneous combustion settings provides a means for linking test

  4. Droplet Combustion Experiment movie

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Droplet Combustion Experiment (DCE) was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1 mission (STS-83, April 4-8 1997; the shortened mission was reflown as MSL-1R on STS-94). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.1 MB, 12-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available)A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300164.html.

  5. Computational Combustion

    SciTech Connect

    Westbrook, C K; Mizobuchi, Y; Poinsot, T J; Smith, P J; Warnatz, J

    2004-08-26

    Progress in the field of computational combustion over the past 50 years is reviewed. Particular attention is given to those classes of models that are common to most system modeling efforts, including fluid dynamics, chemical kinetics, liquid sprays, and turbulent flame models. The developments in combustion modeling are placed into the time-dependent context of the accompanying exponential growth in computer capabilities and Moore's Law. Superimposed on this steady growth, the occasional sudden advances in modeling capabilities are identified and their impacts are discussed. Integration of submodels into system models for spark ignition, diesel and homogeneous charge, compression ignition engines, surface and catalytic combustion, pulse combustion, and detonations are described. Finally, the current state of combustion modeling is illustrated by descriptions of a very large jet lifted 3D turbulent hydrogen flame with direct numerical simulation and 3D large eddy simulations of practical gas burner combustion devices.

  6. Simulating Combustion

    NASA Astrophysics Data System (ADS)

    Merker, G.; Schwarz, C.; Stiesch, G.; Otto, F.

    The content spans from simple thermodynamics of the combustion engine to complex models for the description of the air/fuel mixture, ignition, combustion and pollutant formation considering the engine periphery of petrol and diesel engines. Thus the emphasis of the book is on the simulation models and how they are applicable for the development of modern combustion engines. Computers can be used as the engineers testbench following the rules and recommendations described here.

  7. Pyrolysis reactor and fluidized bed combustion chamber

    DOEpatents

    Green, Norman W.

    1981-01-06

    A solid carbonaceous material is pyrolyzed in a descending flow pyrolysis reactor in the presence of a particulate source of heat to yield a particulate carbon containing solid residue. The particulate source of heat is obtained by educting with a gaseous source of oxygen the particulate carbon containing solid residue from a fluidized bed into a first combustion zone coupled to a second combustion zone. A source of oxygen is introduced into the second combustion zone to oxidize carbon monoxide formed in the first combustion zone to heat the solid residue to the temperature of the particulate source of heat.

  8. Surface oxygen vacancies on WO3 contributed to enhanced photothermo-synergistic effect

    NASA Astrophysics Data System (ADS)

    Li, Yingying; Wang, Changhua; Zheng, Han; Wan, Fangxu; Yu, Fei; Zhang, Xintong; Liu, Yichun

    2017-01-01

    Photothermooxidation has demonstrated a high efficiency in the removal of volatile organic compounds in air. Among photothermocatalysts, attention is presently focused on composites of noble metal/metal oxide or metal oxide/metal oxide. Instead, in this work, we present a case of single oxide WO3 subjected to hydrogen treatment as photothermocatalyst. With the increase of hydrogen treatment temperature, the color of WO3 changes from yellow to blue to dark blue and a phase transition from WO3 to WO2.72 to WO2 is accompanied, suggesting an increase of concentration of oxygen vacancy. Photothermocatalytic test against degradation of gaseous acetaldehyde at 60 °C under UV light shows that WO3-x sample with low concentration of oxygen vacancy displays the most significant synergetic effect between photocatalysis and thermocatalysis. Its photothermocatalytic activity in terms of CO2 evolution rate is 5.2 times higher than that of photocatalytic activity. However, WO3-WO2.72 and WO2 with high degree of oxygen deficiency show insignificant synergetic effect between photocatalysis and thermocatalysis. The reason for the different synergistic effect over above samples is believed to lie in balance between decreased activation energy of lattice oxygen and recombination of photogenerated electrons and holes induced by oxygen deficiency.

  9. Effects of oxygen-containing terpenes as skin permeation enhancers on the lipoidal pathways of human epidermal membrane.

    PubMed

    Chantasart, Doungdaw; Pongjanyakul, Thaned; Higuchi, William I; Li, S Kevin

    2009-10-01

    The present study investigated the effects of oxygen-containing terpenes as skin permeation enhancers on the lipoidal pathways of human epidermal membrane (HEM). The enhancement (E(HEM)) effects of menthol, thymol, carvacrol, menthone, and cineole on the transport of a probe permeant, corticosterone, across HEM were determined. It was found that the enhancer potencies of menthol, thymol, carvacrol, and menthone were essentially the same and higher than that of cineole based on their aqueous concentration in the diffusion cell chamber at E(HEM) = 4. Thymol and carvacrol also had the same E(HEM) = 10 concentration further supporting that they had the same enhancer potency based on the aqueous concentration. The uptake amounts of terpene into the HEM stratum corneum (SC) intercellular lipid under the same conditions indicate that the intrinsic potencies of the studied terpenes are the same based on their concentration in the SC and similar to those of n-alkanol and n-alkylphenyl alcohol. Moreover, they are all better enhancers compared to branched-chain alkanol. The approximately same uptake enhancement of beta-estradiol induced by the studied terpenes and alcohols at E(HEM) conditions into the SC intercellular lipids suggests that the mechanism of enhancement action for the terpenes and those of alcohols are essentially the same.

  10. Proton enhanced dynamic battery chemistry for aprotic lithium-oxygen batteries.

    PubMed

    Zhu, Yun Guang; Liu, Qi; Rong, Yangchun; Chen, Haomin; Yang, Jing; Jia, Chuankun; Yu, Li-Juan; Karton, Amir; Ren, Yang; Xu, Xiaoxiong; Adams, Stefan; Wang, Qing

    2017-02-06

    Water contamination is generally considered to be detrimental to the performance of aprotic lithium-air batteries, whereas this view is challenged by recent contrasting observations. This has provoked a range of discussions on the role of water and its impact on batteries. In this work, a distinct battery chemistry that prevails in water-contaminated aprotic lithium-oxygen batteries is revealed. Both lithium ions and protons are found to be involved in the oxygen reduction and evolution reactions, and lithium hydroperoxide and lithium hydroxide are identified as predominant discharge products. The crystallographic and spectroscopic characteristics of lithium hydroperoxide monohydrate are scrutinized both experimentally and theoretically. Intriguingly, the reaction of lithium hydroperoxide with triiodide exhibits a faster kinetics, which enables a considerably lower overpotential during the charging process. The battery chemistry unveiled in this mechanistic study could provide important insights into the understanding of nominally aprotic lithium-oxygen batteries and help to tackle the critical issues confronted.

  11. Proton enhanced dynamic battery chemistry for aprotic lithium-oxygen batteries

    NASA Astrophysics Data System (ADS)

    Zhu, Yun Guang; Liu, Qi; Rong, Yangchun; Chen, Haomin; Yang, Jing; Jia, Chuankun; Yu, Li-Juan; Karton, Amir; Ren, Yang; Xu, Xiaoxiong; Adams, Stefan; Wang, Qing

    2017-02-01

    Water contamination is generally considered to be detrimental to the performance of aprotic lithium-air batteries, whereas this view is challenged by recent contrasting observations. This has provoked a range of discussions on the role of water and its impact on batteries. In this work, a distinct battery chemistry that prevails in water-contaminated aprotic lithium-oxygen batteries is revealed. Both lithium ions and protons are found to be involved in the oxygen reduction and evolution reactions, and lithium hydroperoxide and lithium hydroxide are identified as predominant discharge products. The crystallographic and spectroscopic characteristics of lithium hydroperoxide monohydrate are scrutinized both experimentally and theoretically. Intriguingly, the reaction of lithium hydroperoxide with triiodide exhibits a faster kinetics, which enables a considerably lower overpotential during the charging process. The battery chemistry unveiled in this mechanistic study could provide important insights into the understanding of nominally aprotic lithium-oxygen batteries and help to tackle the critical issues confronted.

  12. Proton enhanced dynamic battery chemistry for aprotic lithium–oxygen batteries

    PubMed Central

    Zhu, Yun Guang; Liu, Qi; Rong, Yangchun; Chen, Haomin; Yang, Jing; Jia, Chuankun; Yu, Li-Juan; Karton, Amir; Ren, Yang; Xu, Xiaoxiong; Adams, Stefan; Wang, Qing

    2017-01-01

    Water contamination is generally considered to be detrimental to the performance of aprotic lithium–air batteries, whereas this view is challenged by recent contrasting observations. This has provoked a range of discussions on the role of water and its impact on batteries. In this work, a distinct battery chemistry that prevails in water-contaminated aprotic lithium–oxygen batteries is revealed. Both lithium ions and protons are found to be involved in the oxygen reduction and evolution reactions, and lithium hydroperoxide and lithium hydroxide are identified as predominant discharge products. The crystallographic and spectroscopic characteristics of lithium hydroperoxide monohydrate are scrutinized both experimentally and theoretically. Intriguingly, the reaction of lithium hydroperoxide with triiodide exhibits a faster kinetics, which enables a considerably lower overpotential during the charging process. The battery chemistry unveiled in this mechanistic study could provide important insights into the understanding of nominally aprotic lithium–oxygen batteries and help to tackle the critical issues confronted. PMID:28165008

  13. Oxygen plasma immersion ion implantation treatment to enhance data retention of tungsten nanocrystal nonvolatile memory

    SciTech Connect

    Wang, Jer-Chyi Chang, Wei-Cheng; Lai, Chao-Sung; Chang, Li-Chun; Ai, Chi-Fong; Tsai, Wen-Fa

    2014-03-15

    Data retention characteristics of tungsten nanocrystal (W-NC) memory devices using an oxygen plasma immersion ion implantation (PIII) treatment are investigated. With an increase of oxygen PIII bias voltage and treatment time, the capacitance–voltage hysteresis memory window is increased but the data retention characteristics become degraded. High-resolution transmission electron microscopy images show that this poor data retention is a result of plasma damage on the tunneling oxide layer, which can be prevented by lowering the bias voltage to 7 kV. In addition, by using the elevated temperature retention measurement technique, the effective charge trapping level of the WO{sub 3} film surrounding the W-NCs can be extracted. This measurement reveals that a higher oxygen PIII bias voltage and treatment time induces more shallow traps within the WO{sub 3} film, degrading the retention behavior of the W-NC memory.

  14. Modeling of Laser-Induced Metal Combustion

    SciTech Connect

    Boley, C D; Rubenchik, A M

    2008-02-20

    Experiments involving the interaction of a high-power laser beam with metal targets demonstrate that combustion plays an important role. This process depends on reactions within an oxide layer, together with oxygenation and removal of this layer by the wind. We present an analytical model of laser-induced combustion. The model predicts the threshold for initiation of combustion, the growth of the combustion layer with time, and the threshold for self-supported combustion. Solutions are compared with detailed numerical modeling as benchmarked by laboratory experiments.

  15. Creatine supplementation enhances corticomotor excitability and cognitive performance during oxygen deprivation.

    PubMed

    Turner, Clare E; Byblow, Winston D; Gant, Nicholas

    2015-01-28

    Impairment or interruption of oxygen supply compromises brain function and plays a role in neurological and neurodegenerative conditions. Creatine is a naturally occurring compound involved in the buffering, transport, and regulation of cellular energy, with the potential to replenish cellular adenosine triphosphate without oxygen. Creatine is also neuroprotective in vitro against anoxic/hypoxic damage. Dietary creatine supplementation has been associated with improved symptoms in neurological disorders defined by impaired neural energy provision. Here we investigate, for the first time in humans, the utility of creatine as a dietary supplement to protect against energetic insult. The aim of this study was to assess the influence of oral creatine supplementation on the neurophysiological and neuropsychological function of healthy young adults during acute oxygen deprivation. Fifteen healthy adults were supplemented with creatine and placebo treatments for 7 d, which increased brain creatine on average by 9.2%. A hypoxic gas mixture (10% oxygen) was administered for 90 min, causing global oxygen deficit and impairing a range of neuropsychological processes. Hypoxia-induced decrements in cognitive performance, specifically attentional capacity, were restored when participants were creatine supplemented, and corticomotor excitability increased. A neuromodulatory effect of creatine via increased energy availability is presumed to be a contributing factor of the restoration, perhaps by supporting the maintenance of appropriate neuronal membrane potentials. Dietary creatine monohydrate supplementation augments neural creatine, increases corticomotor excitability, and prevents the decline in attention that occurs during severe oxygen deficit. This is the first demonstration of creatine's utility as a neuroprotective supplement when cellular energy provision is compromised.

  16. The role of spray-enhanced swirl flow for combustion stabilization in a stratified-charge DISI engine

    SciTech Connect

    Zeng, Wei; Sjöberg, Magnus; Reuss, David L.; Hu, Zongjie

    2016-06-01

    Implementing spray-guided stratified-charge direct-injection spark-ignited (DISI) engines is inhibited by the occurrence of misfire and partial burns. Engine-performance tests demonstrate that increasing engine speed induces combustion instability, but this deterioration can be prevented by generating swirling flow during the intake stroke. In-cylinder pressure-based heat-release analysis reveals that the appearance of poor-burn cycles is not solely dependent on the variability of early flame-kernel growth. Moreover, cycles can experience burning-rate regression during later combustion stages and may or may not recover before the end of the cycle. Thermodynamic analysis and optical diagnostics are used here to clarify why swirl improves the combustion repeatability from cycle to cycle. The fluid dynamics of swirl/spray interaction was previously demonstrated using high-speed PIV measurements of in-cylinder motored flow. It was found that the sprays of the multi-hole injector redistribute the intake-generated swirl flow momentum, thereby creating a better-centered higher angular-momentum vortex with reduced variability. The engine operation with high swirl was found to have significant improvement in cycle-to-cycle variations of both flow pattern and flow momentum. This paper is an extension of the previous work. Here, PIV measurements and flame imaging are applied to fired operation for studying how the swirl flow affects variability of ignition and subsequent combustion phases. PIV results for fired operation are consistent with the measurements made of motored flow. They demonstrate that the spark-plasma motion is highly correlated with the direction of the gas flow in the vicinity of the spark-plug gap. Without swirl, the plasma is randomly stretched towards either side of the spark plug, causing variability in the ignition of the two spray plumes that are straddling the spark plug. Conversely, swirl flow always convects the spark plasma towards one spray plume

  17. Enhanced Activity and Stability of Pt catalysts on Functionalized Graphene Sheets for Electrocatalytic Oxygen Reduction

    SciTech Connect

    Kou, Rong; Shao, Yuyan; Wang, Donghai; Engelhard, Mark H.; Kwak, Ja Hun; Wang, Jun; Viswanathan, Vilayanur V.; Wang, Chong M.; Lin, Yuehe; Wang, Yong; Aksay, Ilhan A.; Liu, Jun

    2009-04-30

    Electrocatalysis of oxygen reduction using Pt nanoparticles supported on functionalized graphene sheets (FGSs) was studied. FGSs were prepared by thermal expansion of graphite oxide. Pt nanoparticles with average diameter of 2 nm were uniformly loaded on FGSs by impregnation methods. Pt-FGS showed a higher electrochemical surface area and oxygen reduction activity with improved stability as compared with commercial catalyst. Transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical characterization suggest that the improved performance of Pt-FGS can be attributed to smaller particle size and less aggregation of Pt nanoparticles on the functionalized graphene sheets.

  18. Singlet oxygen generation by photoactive polymeric microparticles with enhanced aqueous compatibility.

    PubMed

    Fabregat, Víctor; Burguete, M Isabel; Galindo, Francisco; Luis, Santiago V

    2014-10-01

    Two new photoactive materials compatible with environmentally friendly solvents (water and methanol) have been synthesized and characterized. They are comprised of a porous matrix of polystyrene and divinylbenzene with bound Rose Bengal and additional pendant groups added to increase the hydrophilicity (ethylenediamine and γ-gluconolactone). The new polymers are efficient photocatalysts capable of generating singlet oxygen after irradiation with visible light. Photochemical oxygenations of 9,10-anthracenedipropionic acid and 2-furoic acid have been carried out. The measured conversions indicate that the new supported photosensitizers are more effective than the parent hydrophobic polymer.

  19. Peculiar surface-interface properties of nanocrystalline ceria-cobalt oxides with enhanced oxygen storage capacity.

    PubMed

    Qiu, Nan; Zhang, Jing; Wu, Ziyu

    2014-11-07

    Peculiar surface-interface properties of nanocrystalline ceria-cobalt oxides were evidenced by X-ray diffraction, transmission electron microscopy and X-ray absorption spectroscopy. It was found that cobalt foreign cations modify the surface oxygen vacancies of ceria at the atomic level, inducing the exposure of well-defined reactive faces between the ceria-host and the cobalt oxide interface. These modifications of the surface-interface structure promoted a remarkable increase in the oxygen storage capacity of ceria nanocrystals.

  20. Droplet Combustion Experiment (DCE)

    NASA Technical Reports Server (NTRS)

    Haggard, John B., Jr.; Nayagan, Vedha; Dryer, Frederick L.; Williams, Forman A.

    1998-01-01

    The first space-based experiments were performed on the combustion of free, individual liquid fuel droplets in oxidizing atmospheres. The fuel was heptane, with initial droplet diameters ranging about from 1 mm to 4 mm. The atmospheres were mixtures of helium and oxygen, at pressures of 1.00, 0.50 and 0.25 bar, with oxygen mole fractions between 20% and 40%, as well as normal Spacelab cabin air. The temperatures of the atmospheres and of the initial liquid fuel were nominally 300 K. A total of 44 droplets were burned successfully on the two flights, 8 on the shortened STS-83 mission and 36 on STS-94. The results spanned the full range of heptane droplet combustion behavior, from radiative flame extinction at larger droplet diameters in the more dilute atmospheres to diffusive extinction in the less dilute atmospheres, with the droplet disappearing prior to flame extinction at the highest oxygen concentrations. Quasisteady histories of droplet diameters were observed along with unsteady histories of flame diameters. New and detailed information was obtained on burning rates, flame characteristics and soot behavior. The results have motivated new computational and theoretical investigations of droplet combustion, improving knowledge of the chemical kinetics, fluid mechanics and heat and mass transfer processes involved in burning liquid fuels.

  1. Enhanced spin–orbit torques by oxygen incorporation in tungsten films

    PubMed Central

    Demasius, Kai-Uwe; Phung, Timothy; Zhang, Weifeng; Hughes, Brian P.; Yang, See-Hun; Kellock, Andrew; Han, Wei; Pushp, Aakash; Parkin, Stuart S. P.

    2016-01-01

    The origin of spin–orbit torques, which are generated by the conversion of charge-to-spin currents in non-magnetic materials, is of considerable debate. One of the most interesting materials is tungsten, for which large spin–orbit torques have been found in thin films that are stabilized in the A15 (β-phase) structure. Here we report large spin Hall angles of up to approximately –0.5 by incorporating oxygen into tungsten. While the incorporation of oxygen into the tungsten films leads to significant changes in their microstructure and electrical resistivity, the large spin Hall angles measured are found to be remarkably insensitive to the oxygen-doping level (12–44%). The invariance of the spin Hall angle for higher oxygen concentrations with the bulk properties of the films suggests that the spin–orbit torques in this system may originate dominantly from the interface rather than from the interior of the films. PMID:26912203

  2. Enhancement of ferromagnetism by oxygen isotope substitution in strontium ruthenate SrRuO3

    PubMed Central

    Kawanaka, Hirofumi; Aiura, Yoshihiro; Hasebe, Takayuki; Yokoyama, Makoto; Masui, Takahiko; Nishihara, Yoshikazu; Yanagisawa, Takashi

    2016-01-01

    The oxygen isotope effect of the ferromagnetic transition in itinerant ferromagnet strontium ruthenate SrRuO3 with a Curie temperature Tc of 160 K is studied. We observed for the first time a shift of ∆Tc ~ 1 K by oxygen isotope substitution of 16O → 18O in SrRuO3 by precise measurements of DC and AC magnetizations. The results surprisingly lead to the noteworthy inverse isotope effect with negative coefficient α = −∂ lnTc/∂ lnM. The Raman spectra indicate that the main vibration frequency of 16O at 363 cm−1 shifts to 341 cm−1 following oxygen isotope substitution 18O. This shift is remarkably consistent with the Debye frequency being proportional to ∝ 1√M where M is the mass of an oxygen atom. The positive isotope shift of ∆Tc can be understood by taking account of the electron-phonon interaction. PMID:27739475

  3. Field-scale investigation of enhanced petroleum hydrocarbon biodegradation in the vadose zone combining soil venting as an oxygen source with moisture and nutrient addition. Appendices. Doctoral thesis

    SciTech Connect

    Miller, R.N.

    1990-01-01

    This document contains appendices regarding a reprint on a field scale investigation of enhanced petroleum hydrocarbon biodegradation in the vadose zone combining soil venting as a oxygen source with moisture and nutrient addition.

  4. Enhanced Adhesion of Campylobacter jejuni to Abiotic Surfaces Is Mediated by Membrane Proteins in Oxygen-Enriched Conditions

    PubMed Central

    Sulaeman, Sheiam; Hernould, Mathieu; Schaumann, Annick; Coquet, Laurent; Bolla, Jean-Michel; Dé, Emmanuelle; Tresse, Odile

    2012-01-01

    Campylobacter jejuni is responsible for the major foodborne bacterial enteritis in humans. In contradiction with its fastidious growth requirements, this microaerobic pathogen can survive in aerobic food environments, suggesting that it must employ a variety of protection mechanisms to resist oxidative stress. For the first time, C. jejuni 81–176 inner and outer membrane subproteomes were analyzed separately using two-dimensional protein electrophoresis (2-DE) of oxygen-acclimated cells and microaerobically grown cells. LC-MS/MS analyses successfully identified 42 and 25 spots which exhibited a significantly altered abundance in the IMP-enriched fraction and in the OMP-enriched fraction, respectively, in response to oxidative conditions. These spots corresponded to 38 membrane proteins that could be grouped into different functional classes: (i) transporters, (ii) chaperones, (iii) fatty acid metabolism, (iv) adhesion/virulence and (v) other metabolisms. Some of these proteins were up-regulated at the transcriptional level in oxygen-acclimated cells as confirmed by qRT-PCR. Downstream analyses revealed that adhesion of C. jejuni to inert surfaces and swarming motility were enhanced in oxygen-acclimated cells or paraquat-stressed cells, which could be explained by the higher abundance of membrane proteins involved in adhesion and biofilm formation. The virulence factor CadF, over-expressed in the outer membrane of oxygen-acclimated cells, contributes to the complex process of C. jejuni adhesion to inert surfaces as revealed by a reduction in the capability of C. jejuni 81–176 ΔCadF cells compared to the isogenic strain. Taken together, these data demonstrate that oxygen-enriched conditions promote the over-expression of membrane proteins involved in both the biofilm initiation and virulence of C. jejuni. PMID:23029510

  5. Barium carbonate nanoparticle to enhance oxygen reduction activity of strontium doped lanthanum ferrite for solid oxide fuel cell

    NASA Astrophysics Data System (ADS)

    Hong, Tao; Chen, Fanglin; Xia, Changrong

    2015-03-01

    BaCO3 nanoparticles are demonstrated as outstanding catalysts for high-temperature oxygen reduction reaction (ORR) on the La0.8Sr0.2FeO3-δ (LSF) cathode for solid oxide fuel cells (SOFCs) based on ytrria-stabilized zirconia (YSZ) electrolytes. Thermal gravitational and X-ray diffraction measurements show that BaCO3 is stable and chemically compatible with LSF under the fabrication and operation conditions of intermediate-temperature SOFCs. The BaCO3 nanoparticles can greatly reduce the interfacial polarization resistance; from 2.96 to 0.84 Ω cm2 at 700 °C when 12.9wt% BaCO3 is infiltrated to the porous LSF electrode on the YSZ electrolyte. Electrochemical impedance spectroscopy shows that there is about one order of magnitude decrease in the low-frequency resistance, indicating that BaCO3 nanoparticles can greatly enhance the surface steps for ORR. Electrical conductivity relaxation investigation indicates about one order of magnitude increase in the chemical oxygen surface exchange coefficient when BaCO3 is applied, directly demonstrating significant increase in the kinetics for ORR. In addition, LSF cathodes with infiltrated BaCO3 nanoparticles have shown excellent stability and substantially enhanced cell performance as demonstrated with single cells, suggesting BaCO3 nanoparticles are very effective in enhancing ORR on LSF.

  6. Light-triggered liposomal cargo delivery platform incorporating photosensitizers and gold nanoparticles for enhanced singlet oxygen generation and increased cytotoxicity

    PubMed Central

    Kautzka, Zofia; Clement, Sandhya; Goldys, Ewa M; Deng, Wei

    2017-01-01

    We developed light-triggered liposomes incorporating 3–5 nm hydrophobic gold nanoparticles and Rose Bengal (RB), a well-known photosensitizer used for photodynamic therapy. Singlet oxygen generated by these liposomes with 532 nm light illumination was characterized for varying the molar ratio of lipids and gold nanoparticles while keeping the amount of RB constant. Gold nanoparticles were found to enhance the singlet oxygen generation rate, with a maximum enhancement factor of 1.75 obtained for the molar ratio of hydrogenated soy l-α-phosphatidylcholine:1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(hexanoylamine):gold of 57:5:17 compared with liposomes loaded with RB alone. The experimental results could be explained by the local electric field enhancement caused by gold nanoparticles. We further assessed cellular cytotoxicity of gold-loaded liposomes by encapsulating an antitumor drug, doxorubicin (Dox); such Dox-loaded liposomes were applied to human colorectal cancer cells (HCT116) and exposed to light. Gold-loaded liposomes containing RB and Dox where Dox release was triggered by light were found to exhibit higher cytotoxicity compared with the liposomes loaded with RB and Dox alone. Our results indicate that gold-loaded liposomes incorporating photosensitizers may serve as improved agents in photodynamic therapy and chemotherapy. PMID:28203076

  7. Co-enhancement of fluorescence and singlet oxygen generation by silica-coated gold nanorods core-shell nanoparticle

    NASA Astrophysics Data System (ADS)

    Ke, Xuebin; Wang, Dong; Chen, Changqing; Yang, Anqi; Han, Yu; Ren, Lei; Li, Donghui; Wang, Hongjun

    2014-12-01

    Metal-enhanced fluorescence (MEF) as a newly recognized technology has been attracting considerable attention and is widely used in fluorescence-based technology. In this paper, we reported a novel distance-dependent MEF and metal-enhanced singlet oxygen generation phenomenon based on silica-coated gold nanorods (AuNRs@SiO2) core-shell structure with tetra-substituted carboxyl aluminum phthalocyanine (AlC4Pc) that serve as both fluorophore and photosensitizer. When the AlC4Pc was linked on the surface of AuNRs@SiO2, the fluorescence intensity and singlet oxygen productivity varied with the thickness difference of silica shell from 2.1 to 28.6 nm. The co-enhancement effect reached the maximum of 7-fold and 2.1-fold, respectively, when the separation distance was 10.6 nm. These unique characteristics make the prepared core-shell nanoparticles promising for MEF-based biological imaging and photodynamics therapy.

  8. Flame Propagation Enhancement by Plasma Excitation of Oxygen. Part 1. Effects of O3

    DTIC Science & Technology

    2010-01-01

    gradient, marked as A in Fig. 7, the enhancement is the largest as shown in Fig. 9. The factor of four difference in the flame speed enhancement...earlier in this section. For a small mixture fraction gradient, marked as B in Fig. 7, the local flame speed enhancement is less, approaching the...0.99 and agreed well with numerical simu- lation results, marked as C in Fig. 7. Note that the deviation be- tween experimental and numerical results

  9. Oxygen-17 dynamic nuclear polarisation enhanced solid-state NMR spectroscopy at 18.8 T.

    PubMed

    Brownbill, Nick J; Gajan, David; Lesage, Anne; Emsley, Lyndon; Blanc, Frédéric

    2017-02-23

    We report (17)O dynamic nuclear polarisation (DNP) enhanced solid-state NMR experiments at 18.8 T. Several formulations were investigated on the Mg(OH)2 compound. A signal enhancement factor of 17 could be obtained when the solid particles were incorporated into a glassy o-terphenyl matrix doped with BDPA using the Overhauser polarisation transfer scheme whilst the cross effect mechanism enabled by TEKPol yielded a slightly lower enhancement but more time efficient data acquisition.

  10. Investigation of chemical looping combustion by solid fuels. 2. redox reaction kinetics and product characterization with coal, biomass, and solid waste as solid fuels and CuO as an oxygen carrier

    SciTech Connect

    Yan Cao; Bianca Casenas; Wei-Ping Pan

    2006-10-15

    This paper is the second in a series of two on the investigation of the chemical looping combustion (CLC) of solid fuels. The first paper put forward the concept of the CLC of solid fuels using a circulating fluidized bed as a reactor and Cu-CuO as the oxygen carrier, which was based on an analysis of oxygen transfer capability, reaction enthalpy, and chemical equilibrium. In this second paper, we report the results of the evaluation of the reduction of CuO reduced by solid fuels such as coal and some other 'opportunity' solid fuels. Tests on the reduction of CuO by the selected solid fuels were conducted using simultaneous differential scanning calorimetry and thermogravimetric analysis, which simulates a microreactor. An attached mass spectrometer (MS) was used for the characterization of evolved gaseous products. The X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used for the characterization of the solid residues. Results strongly supported the feasibility of CuO reduction by selected solid fuels. CuO can be fully converted into Cu in a reduction process, either in a direct path by solid fuels, which was verified by MS analysis under a N{sub 2} atmosphere, or in an indirect path by pyrolysis and gasification products of solid fuels in the reducer. No Cu{sub 2}O exists in reducing atmospheres, which was characterized by an XRD analysis and mass balance calculations. No carbon deposit was found on the surface of the reduced Cu, which was characterized by SEM analysis. CuO reduction by solid fuels can start at temperatures as low as approximately 500 C. Tests indicated that the solid fuels with higher reactivity (higher volatile matter) would be desirable for the development of the chemical looping combustion process of solid fuels, such as sub-bituminous Powder River Basin coal and solid waste and biomass. 4 refs., 12 figs., 3 tabs.

  11. The role of spray-enhanced swirl flow for combustion stabilization in a stratified-charge DISI engine

    DOE PAGES

    Zeng, Wei; Sjöberg, Magnus; Reuss, David L.; ...

    2016-06-01

    Implementing spray-guided stratified-charge direct-injection spark-ignited (DISI) engines is inhibited by the occurrence of misfire and partial burns. Engine-performance tests demonstrate that increasing engine speed induces combustion instability, but this deterioration can be prevented by generating swirling flow during the intake stroke. In-cylinder pressure-based heat-release analysis reveals that the appearance of poor-burn cycles is not solely dependent on the variability of early flame-kernel growth. Moreover, cycles can experience burning-rate regression during later combustion stages and may or may not recover before the end of the cycle. Thermodynamic analysis and optical diagnostics are used here to clarify why swirl improves the combustionmore » repeatability from cycle to cycle. The fluid dynamics of swirl/spray interaction was previously demonstrated using high-speed PIV measurements of in-cylinder motored flow. It was found that the sprays of the multi-hole injector redistribute the intake-generated swirl flow momentum, thereby creating a better-centered higher angular-momentum vortex with reduced variability. The engine operation with high swirl was found to have significant improvement in cycle-to-cycle variations of both flow pattern and flow momentum. This paper is an extension of the previous work. Here, PIV measurements and flame imaging are applied to fired operation for studying how the swirl flow affects variability of ignition and subsequent combustion phases. PIV results for fired operation are consistent with the measurements made of motored flow. They demonstrate that the spark-plasma motion is highly correlated with the direction of the gas flow in the vicinity of the spark-plug gap. Without swirl, the plasma is randomly stretched towards either side of the spark plug, causing variability in the ignition of the two spray plumes that are straddling the spark plug. Conversely, swirl flow always convects the spark plasma towards one

  12. Flammability of Heterogeneously Combusting Metals

    NASA Technical Reports Server (NTRS)

    Jones, Peter D.

    1998-01-01

    Most engineering materials, including some metals, most notably aluminum, burn in homogeneous combustion. 'Homogeneous' refers to both the fuel and the oxidizer being in the same phase, which is usually gaseous. The fuel and oxidizer are well mixed in the combustion reaction zone, and heat is released according to some relation like q(sub c) = delta H(sub c)c[((rho/rho(sub 0))]exp a)(exp -E(sub c)/RT), Eq. (1) where the pressure exponent a is usually close to unity. As long as there is enough heat released, combustion is sustained. It is useful to conceive of a threshold pressure beyond which there is sufficient heat to keep the temperature high enough to sustain combustion, and beneath which the heat is so low that temperature drains away and the combustion is extinguished. Some materials burn in heterogeneous combustion, in which the fuel and oxidizer are in different phases. These include iron and nickel based alloys, which burn in the liquid phase with gaseous oxygen. Heterogeneous combustion takes place on the surface of the material (fuel). Products of combustion may appear as a solid slag (oxide) which progressively covers the fuel. Propagation of the combustion melts and exposes fresh fuel. Heterogeneous combustion heat release also follows the general form of Eq.(1), except that the pressure exponent a tends to be much less than 1. Therefore, the increase in heat release with increasing pressure is not as dramatic as it is in homogeneous combustion. Although the concept of a threshold pressure still holds in heterogeneous combustion, the threshold is more difficult to identify experimentally, and pressure itself becomes less important relative to the heat transfer paths extant in any specific application. However, the constants C, a, and E(sub c) may still be identified by suitable data reduction from heterogeneous combustion experiments, and may be applied in a heat transfer model to judge the flammability of a material in any particular actual

  13. Electron Beam Induced Etching of Carbon Nanotubes Enhanced by Secondary Electrons in Oxygen.

    PubMed

    Yoshida, Hideto; Tomita, Yuto; Soma, Kentaro; Takeda, Seiji

    2017-03-30

    Multi-walled carbon nanotubes (CNTs) are subjected to electron-beam-induced etching (EBIE) in oxygen. The EBIE process is observed in-situ by environmental transmission electron microscopy (ETEM). The partial pressure of oxygen (10 Pa and 100 Pa), energy of the primary electrons (80 and 200 keV), and environment of the CNTs (suspended or supported on a silicon nitride membrane) are investigated as factors affecting the etching rate. The EBIE rate of CNTs was markedly promoted by the effects of secondary electrons that were emitted from a silicon nitride membrane under irradiation by primary electrons. Membrane supported CNTs can be cut by EBIE with a spatial accuracy better than 3 nm, and a nanogap of 2 nm can be successfully achieved between the ends of two suspended CNTs.

  14. Acute cocoa flavanol improves cerebral oxygenation without enhancing executive function at rest or after exercise.

    PubMed

    Decroix, Lieselot; Tonoli, Cajsa; Soares, Danusa D; Tagougui, Semah; Heyman, Elsa; Meeusen, Romain

    2016-12-01

    Acute exercise-induced improvements in cognitive function are accompanied by increased (cerebral) blood flow and increased brain-derived neurotrophic factor (BDNF) levels. Acute cocoa flavanol (CF) intake may improve cognitive function, cerebral blood flow (in humans), and BNDF levels (in animals). This study investigated (i) the effect of CF intake in combination with exercise on cognitive function and (ii) cerebral hemodynamics and BDNF in response to CF intake and exercise. Twelve healthy men participated in this randomized, double-blind, crossover study. Participants performed a cognitive task (CT) at 100 min after acute 903-mg CF or placebo (PL) intake, followed by a 30-min time-trial. Immediately after this exercise, the same CT was performed. Prefrontal near-infrared spectroscopy was applied during CT and exercise to measure changes in oxygenated (ΔHbO2), deoxygenated (ΔHHb), and total haemoglobin (ΔHbtot) and blood samples were drawn and analyzed for BDNF. Reaction time was faster postexercise, but was not influenced by CF. ΔHbO2 during the resting CT was increased by CF, compared with PL. ΔHbO2, ΔHHb, and ΔHbtot increased in response to exercise without any effect of CF. During the postexercise cognitive task, there were no hemodynamic differences between CF or PL. Serum BDNF was increased by exercise, but was not influenced by CF. In conclusion, at rest, CF intake increased cerebral oxygenation, but not BDNF concentrations, and no impact on executive function was detected. This beneficial effect of CF on cerebral oxygenation at rest was overruled by the strong exercise-induced increases in cerebral perfusion and oxygenation.

  15. Effects of Enhanced Oxygen Delivery by Perfluorocarbons in Spinal Cord Injury

    DTIC Science & Technology

    2013-01-01

    cerebral oxygenation and mitochondrial function after fluid percussion brain injury in rats. Neurosurgery 2004; 54:1223–1230. 11. Spiess B...recovery after lateral fluid percussion brain injury in rats. Neurosurgery 2008; 4 :799-806. 14. Basso DM, Beattie MS, Bresnahan JC, Anderson DK, Faden AI...been shown to cause significant mechanical damage to the parenchyma, in particular the microvasculature leading to plasma fluid leaks, reduction of

  16. Energy transfer enhancement by oxygen perturbation of spin-forbidden electronic transitions in aromatic systems

    NASA Astrophysics Data System (ADS)

    Monguzzi, A.; Tubino, R.; Salamone, M. M.; Meinardi, F.

    2010-09-01

    Triplet-triplet energy transfer in multicomponent organic systems is usually entirely ascribed to a Dexter-type mechanism involving only short-range donor/acceptor interactions. We demonstrate that the presence of molecular oxygen introduces a perturbation to the electronic structure of one of the involved moieties which can induce a large increase in the spin-forbidden transition oscillator strength so that the otherwise negligible Förster contribution dominates the overall energy transfer rate.

  17. Time- and energy-efficient solution combustion synthesis of binary metal tungstate nanoparticles with enhanced photocatalytic activity.

    PubMed

    Thomas, Abegayl; Janáky, Csaba; Samu, Gergely F; Huda, Muhammad N; Sarker, Pranab; Liu, J Ping; van Nguyen, Vuong; Wang, Evelyn H; Schug, Kevin A; Rajeshwar, Krishnan

    2015-05-22

    In the search for stable and efficient photocatalysts beyond TiO2 , the tungsten-based oxide semiconductors silver tungstate (Ag2 WO4 ), copper tungstate (CuWO4 ), and zinc tungstate (ZnWO4 ) were prepared using solution combustion synthesis (SCS). The tungsten precursor's influence on the product was of particular relevance to this study, and the most significant effects are highlighted. Each sample's photocatalytic activity towards methyl orange degradation was studied and benchmarked against their respective commercial oxide sample obtained by solid-state ceramic synthesis. Based on the results herein, we conclude that SCS is a time- and energy-efficient method to synthesize crystalline binary tungstate nanomaterials even without additional excessive heat treatment. As many of these photocatalysts possess excellent photocatalytic activity, the discussed synthetic strategy may open sustainable materials chemistry avenues to solar energy conversion and environmental remediation.

  18. Polydopamine-Coated Manganese Complex/Graphene Nanocomposite for Enhanced Electrocatalytic Activity Towards Oxygen Reduction

    NASA Astrophysics Data System (ADS)

    Parnell, Charlette M.; Chhetri, Bijay; Brandt, Andrew; Watanabe, Fumiya; Nima, Zeid A.; Mudalige, Thilak K.; Biris, Alexandru S.; Ghosh, Anindya

    2016-08-01

    Platinum electrodes are commonly used electrocatalysts for oxygen reduction reactions (ORR) in fuel cells. However, this material is not economical due to its high cost and scarcity. We prepared an Mn(III) catalyst supported on graphene and further coated with polydopamine, resulting in superior ORR activity compared to the uncoated PDA structures. During ORR, a peak potential at 0.433 V was recorded, which is a significant shift compared to the uncoated material’s ‑0.303 V (both versus SHE). All the materials reduced oxygen in a wide pH range via a four-electron pathway. Rotating disk electrode and rotating ring disk electrode studies of the polydopamine-coated material revealed ORR occurring via 4.14 and 4.00 electrons, respectively. A rate constant of 6.33 × 106 mol‑1s‑1 was observed for the polydopamine-coated material–over 4.5 times greater than the uncoated nanocomposite and superior to those reported for similar carbon-supported metal catalysts. Simply integrating an inexpensive bioinspired polymer coating onto the Mn-graphene nanocomposite increased ORR performance significantly, with a peak potential shift of over +730 mV. This indicates that the material can reduce oxygen at a higher rate but with lower energy usage, revealing its excellent potential as an ORR electrocatalyst in fuel cells.

  19. Enhancement of oxygen transfer efficiency in diffused aeration systems using liquid-film-forming apparatus.

    PubMed

    Zhu, H; Imai, T; Tani, K; Ukita, M; Sekine, M; Higuchi, T; Zhang, Z J

    2007-05-01

    Surface transfer and bubble transfer both contribute significantly to oxygen transfer in a diffused aeration system. In the present study, liquid-film-forming apparatus is successfully developed on a laboratory scale to improve considerably the surface transfer via the unique liquid film transfer technique. The experimental results show that the volumetric mass transfer coefficient for liquid-film-forming apparatus alone is found to be as much as 5.3 times higher than that for water surface and that the total volumetric mass transfer coefficient for liquid film aeration system increases by 37 % in comparison with conventional aeration system. Additionally, by tuning finely the structural parameters of the liquid-film-forming apparatus, it can also lead to high dissolved oxygen water with the dissolved oxygen percent saturation greater than 90 %. More importantly, this result is accomplished by simply offering a single-pass aeration at the depth as shallow as 26 cm. As a result, the objective of economical energy consumption in diffused aeration systems can be realized by lowering the aeration depth without sacrificing the aeration efficiency.

  20. Polydopamine-Coated Manganese Complex/Graphene Nanocomposite for Enhanced Electrocatalytic Activity Towards Oxygen Reduction

    PubMed Central

    Parnell, Charlette M.; Chhetri, Bijay; Brandt, Andrew; Watanabe, Fumiya; Nima, Zeid A.; Mudalige, Thilak K.; Biris, Alexandru S.; Ghosh, Anindya

    2016-01-01

    Platinum electrodes are commonly used electrocatalysts for oxygen reduction reactions (ORR) in fuel cells. However, this material is not economical due to its high cost and scarcity. We prepared an Mn(III) catalyst supported on graphene and further coated with polydopamine, resulting in superior ORR activity compared to the uncoated PDA structures. During ORR, a peak potential at 0.433 V was recorded, which is a significant shift compared to the uncoated material’s −0.303 V (both versus SHE). All the materials reduced oxygen in a wide pH range via a four-electron pathway. Rotating disk electrode and rotating ring disk electrode studies of the polydopamine-coated material revealed ORR occurring via 4.14 and 4.00 electrons, respectively. A rate constant of 6.33 × 106 mol−1s−1 was observed for the polydopamine-coated material–over 4.5 times greater than the uncoated nanocomposite and superior to those reported for similar carbon-supported metal catalysts. Simply integrating an inexpensive bioinspired polymer coating onto the Mn-graphene nanocomposite increased ORR performance significantly, with a peak potential shift of over +730 mV. This indicates that the material can reduce oxygen at a higher rate but with lower energy usage, revealing its excellent potential as an ORR electrocatalyst in fuel cells. PMID:27528439

  1. N-doped P25 TiO2-amorphous Al2O3 composites: one-step solution combustion preparation and enhanced visible-light photocatalytic activity.

    PubMed

    Li, Fa-tang; Zhao, Ye; Hao, Ying-juan; Wang, Xiao-jing; Liu, Rui-hong; Zhao, Di-shun; Chen, Dai-mei

    2012-11-15

    Nitrogen-doped Degussa P25 TiO2-amorphous Al2O3 composites were prepared via facile solution combustion. The composites were characterised using X-ray diffraction, high-resolution transmission microscopy, scanning electron microscopy, nitrogen adsorption-desorption measurements, X-ray photoelectron spectroscopy, UV-vis light-diffusion reflectance spectrometry (DRS), zeta-potential measurements, and photoluminescence spectroscopy. The DRS results showed that TiO2 and amorphous Al2O3 exhibited absorption in the UV region. However, the Al2O3/TiO2 composite exhibited visible-light absorption, which was attributed to N-doping during high-temperature combustion and to alterations in the electronic structure of Ti species induced by the addition of Al. The optimal molar ratio of TiO2 to Al2O3 was 1.5:1, and this composite exhibited a large specific surface area of 152 m2/g, surface positive charges, and enhanced photocatalytic activity. These characteristics enhanced the degradation rate of anionic methylene orange, which was 43.6 times greater than that of pure P25 TiO2. The high visible-light photocatalytic activity was attributed to synthetic effects between amorphous Al2O3 and TiO2, low recombination efficiency of photo-excited electrons and holes, N-doping, and a large specific surface area. Experiments that involved radical scavengers indicated that OH and O2- were the main reactive species. A potential photocatalytic mechanism was also proposed.

  2. Exposure of Pt(5 5 3) and Rh(1 1 1) to atomic and molecular oxygen: do defects enhance subsurface oxygen formation?

    PubMed

    Farber, Rachael G; Turano, Marie E; Oskorep, Eleanor C N; Wands, Noelle T; Juurlink, Ludo B F; Killelea, Daniel R

    2017-04-26

    Subsurface oxygen is known to form in transition metals, and is thought to be an important aspect of their ability to catalyze chemical reactions. The formation of subsurface oxygen is not, however, equivalent across all catalytically relevant metals. As a result, it is difficult to predict the stability and ease of the formation of subsurface oxygen in metals, as well as how the absorbed oxygen affects the chemical and physical properties of the metal. In comparing how a stepped platinum surface, Pt(5 5 3), responds to exposure to gas-phase oxygen atoms under ultra-high vacuum conditions to planar Rh(1 1 1), we are able to determine what role, if any, steps have on the capacity of a metal for subsurface oxygen formation. Despite the presence of regular defects, we found that only surface-bound oxygen formed on Pt(5 5 3). Alternatively, on the Rh(1 1 1) surface, oxygen readily absorbed into the selvedge of the metal. These results suggest that defects alone are insufficient for the formation of subsurface oxygen, and the ability of the metal to absorb oxygen is the primary factor in the formation and stabilization of subsurface oxygen.

  3. Exposure of Pt(5 5 3) and Rh(1 1 1) to atomic and molecular oxygen: do defects enhance subsurface oxygen formation?

    NASA Astrophysics Data System (ADS)

    Farber, Rachael G.; Turano, Marie E.; Oskorep, Eleanor C. N.; Wands, Noelle T.; Juurlink, Ludo B. F.; Killelea, Daniel R.

    2017-04-01

    Subsurface oxygen is known to form in transition metals, and is thought to be an important aspect of their ability to catalyze chemical reactions. The formation of subsurface oxygen is not, however, equivalent across all catalytically relevant metals. As a result, it is difficult to predict the stability and ease of the formation of subsurface oxygen in metals, as well as how the absorbed oxygen affects the chemical and physical properties of the metal. In comparing how a stepped platinum surface, Pt(5 5 3), responds to exposure to gas-phase oxygen atoms under ultra-high vacuum conditions to planar Rh(1 1 1), we are able to determine what role, if any, steps have on the capacity of a metal for subsurface oxygen formation. Despite the presence of regular defects, we found that only surface-bound oxygen formed on Pt(5 5 3). Alternatively, on the Rh(1 1 1) surface, oxygen readily absorbed into the selvedge of the metal. These results suggest that defects alone are insufficient for the formation of subsurface oxygen, and the ability of the metal to absorb oxygen is the primary factor in the formation and stabilization of subsurface oxygen.

  4. Enhancement of YBCO thin film thermal stability under 1 ATM oxygen pressure by intermediate Cu2O nanolayer.

    PubMed

    Cheng, L; Wang, X; Yao, X; Wan, W; Li, F H; Xiong, J; Tao, B W; Jirsa, M

    2010-06-10

    The melting process of YBa(2)Cu(3)O(x) (YBCO or Y123) films under an oxygen atmosphere was observed in situ by means of high-temperature optical microscopy. The films were classified by pole figure measurement as c-axis oriented, with two different in-plane orientations (denoted as 0 and 45 degrees). In the 45 degrees-oriented films, electron diffraction and high-resolution transmission electron microscopy (HRTEM) detected an intermediate Cu(2)O nanolayer in the vicinity of the interface. The melting mode and the thermal stability of the YBCO thin films with different in-plane orientations were greatly influenced by oxygen partial pressure. Notably, the thermal stability of the 45 degrees-oriented YBCO films dramatically grew with increasing oxygen partial pressure. We attributed this effect to a change in the intermediate Cu(2)O nanolayer thermal stability. We conclude and suggest that the thermal stability of YBCO films can be significantly enhanced by inserting a Cu(2)O buffer nanolayer.

  5. Engineering the Electrical Conductivity of Lamellar Silver-Doped Cobalt(II) Selenide Nanobelts for Enhanced Oxygen Evolution.

    PubMed

    Zhao, Xu; Zhang, Hantao; Yan, Yu; Cao, Jinhua; Li, Xingqi; Zhou, Shiming; Peng, Zhenmeng; Zeng, Jie

    2017-01-02

    Precisely engineering the electrical conductivity represents a promising strategy to design efficient catalysts towards oxygen evolution reaction (OER). Here, we demonstrate a versatile partial cation exchange method to fabricate lamellar Ag-CoSe2 nanobelts with controllable conductivity. The electrical conductivity of the materials was significantly enhanced by the addition of Ag(+) cations of less than 1.0 %. Moreover, such a trace amount of Ag induced a negligible loss of active sites which was compensated through the effective generation of active sites as shown by the excellent conductivity. Both the enhanced conductivity and the retained active sites contributed to the remarkable electrocatalytic performance of the Ag-CoSe2 nanobelts. Relative to the CoSe2 nanobelts, the as-prepared Ag-CoSe2 nanobelts exhibited a higher current density and a lower Tafel slope towards OER. This strategy represents a rational design of efficient electrocatalysts through finely tuning their electrical conductivities.

  6. The oxycoal process with cryogenic oxygen supply

    NASA Astrophysics Data System (ADS)

    Kather, Alfons; Scheffknecht, Günter

    2009-09-01

    ash or the deposits that form. In particular, detailed nitrogen and sulphur chemistry was investigated by combustion tests in a laboratory-scale facility. Oxidant staging, in order to reduce NO formation, turned out to work with similar effectiveness as for conventional air combustion. With regard to sulphur, a considerable increase in the SO2 concentration was found, as expected. However, the H2S concentration in the combustion atmosphere increased as well. Further results were achieved with a pilot-scale test facility, where acid dew points were measured and deposition probes were exposed to the combustion environment. Besides CO2 and water vapour, the flue gas contains impurities like sulphur species, nitrogen oxides, argon, nitrogen, and oxygen. The CO2 liquefaction is strongly affected by these impurities in terms of the auxiliary power requirement and the CO2 capture rate. Furthermore, the impurity of the liquefied CO2 is affected as well. Since the requirements on the liquid CO2 with regard to geological storage or enhanced oil recovery are currently undefined, the effects of possible flue gas treatment and the design of the liquefaction plant are studied over a wide range.

  7. The oxycoal process with cryogenic oxygen supply.

    PubMed

    Kather, Alfons; Scheffknecht, Günter

    2009-09-01

    ash or the deposits that form. In particular, detailed nitrogen and sulphur chemistry was investigated by combustion tests in a laboratory-scale facility. Oxidant staging, in order to reduce NO formation, turned out to work with similar effectiveness as for conventional air combustion. With regard to sulphur, a considerable increase in the SO2 concentration was found, as expected. However, the H2S concentration in the combustion atmosphere increased as well. Further results were achieved with a pilot-scale test facility, where acid dew points were measured and deposition probes were exposed to the combustion environment. Besides CO2 and water vapour, the flue gas contains impurities like sulphur species, nitrogen oxides, argon, nitrogen, and oxygen. The CO2 liquefaction is strongly affected by these impurities in terms of the auxiliary power requirement and the CO2 capture rate. Furthermore, the impurity of the liquefied CO2 is affected as well. Since the requirements on the liquid CO2 with regard to geological storage or enhanced oil recovery are currently undefined, the effects of possible flue gas treatment and the design of the liquefaction plant are studied over a wide range.

  8. Structural features and enhanced high-temperature oxygen ion transport in SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}

    SciTech Connect

    Markov, Alexey A.; Shalaeva, Elizaveta V.; Tyutyunnik, Alexander P.; Kuchin, Vasily V.; Patrakeev, Mikhail V.; Leonidov, Ilya A.; Kozhevnikov, Victor L.

    2013-01-15

    Structural features, oxygen non-stoichiometry and transport properties are studied in the oxide series SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}, where x=0.2, 0.3 and 0.4. X-ray diffraction and electron microscopy data evidence formation of the inhomogeneous materials at x=0.3 and 0.4, which include phase constituents with a cubic perovskite and a double perovskite structure types. The composition, the amount and the typical grain size of the phase inhomogeneities are shown to depend both on doping and oxygen content. The increased oxygen-ion conductivity is observed in oxygen depleted materials, which is explained by the increase in the amount of cubic perovskite-like phase and development of interfacial pathways favorable for enhanced oxygen ion transport. - Graphical abstract: The structural studies, oxygen content and conductivity measurements suggest that oxygen depletion from the double perovskite phase constituent of SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}} for x>0.2 is accompanied by formation of pathways for fast ion transport. Black-Small-Square Highlights: Black-Right-Pointing-Pointer The double perovskite type regions are shown to exist in SrFe{sub 1-x}Ta{sub x}O{sub 3-{delta}}. Black-Right-Pointing-Pointer The oxygen depletion is accompanied with phase separation. Black-Right-Pointing-Pointer The phase separation favors formation of pathways for enhanced oxygen ion transport.

  9. Multicycle study on chemical-looping combustion of simulated coal gas with a CaSO{sub 4} oxygen carrier in a fluidized bed reactor

    SciTech Connect

    Qilei Song; Rui Xiao; Zhongyi Deng; Wenguang Zheng; Laihong Shen; Jun Xiao

    2008-11-15

    The cyclic test of a CaSO{sub 4}-based oxygen carrier (natural anhydrite) in alternating reducing simulated coal gas and oxidizing conditions was performed at 950{degree}C in a fluidized bed reactor at atmospheric pressure. A high concentration of CO{sub 2} was obtained in the reduction. The H{sub 2} and CO conversions and CO{sub 2} yield increased initially and final decreased significantly. The release of SO{sub 2} and H{sub 2}S during the cyclic test was found to be responsible for the decrease of reactivity of a CaSO{sub 4} oxygen carrier. The oxygen carrier conversion after the reduction reaction decreased gradually in the cyclic test. Through the comparison of mass-based reaction rates as a function of mass conversion at typical cycles, it was also evident that the reactivity of a CaSO{sub 4} oxygen carrier increased for the initial cycles but finally decreased after around 15 cycles. X-ray diffraction analysis revealed that the presence and intensity of the reduction sulfur species was in accordance with the results of gas conversion. The content of CaO was higher than expected, suggesting the formation of SO{sub 2} and H{sub 2}S during the cycles. Surface morphology analysis demonstrates that the natural anhydrite particle surface varied from impervious to porous after the cyclic test. It was also observed that the small grains on the surface of the oxygen carrier sintered in the cyclic tests. Energy-dispersive spectrum analysis also demonstrated the decrease of oxygen intensity after reduction, and CaO became the main component after the 20th oxidation. Pore structure analysis suggested that the particles agglomerated or sintered in the cyclic tests. The possible method for sulfur mitigation is proposed. Finally, some basic consideration on the design criteria of a CLC system for solid fuels using a CaSO{sub 4} oxygen carrier is discussed by the references and provides direction for future work. 49 refs., 10 figs., 5 tabs.

  10. Enhanced Shrinkage of Lanthanum Strontium Manganite (La0.90Sr0.10MnO3+δ) Resulting from Thermal and Oxygen Partial Pressure Cycling

    SciTech Connect

    McCarthy, Ben; Pederson, Larry R.; Anderson, Harlan U.; Zhou, Xiao Dong; Singh, Prabhakar; Coffey, Greg W.; Thomsen, Ed C.

    2007-10-01

    Exposure of La0.9Sr0.1MnO3+δ to repeated oxygen partial pressure cycles (air/10 ppm O2) resulted in enhanced densification rates, similar to behavior shown previously due to thermal cycling. Shrinkage rates in the temperature range 700 to 1000oC were orders of magnitude higher than Makipirtti-Meng model estimations based on stepwise isothermal dilatometry results at high temperature. A maximum in enhanced shrinkage due to oxygen partial pressure cycling occurred at 900oC. Shrinkage was greatest when LSM-10 bars that were first equilibrated in air were exposed to gas flows of lower oxygen fugacity than in the reverse direction. The former creates transient cation and oxygen vacancies well above the equilibrium concentration, resulting in enhanced mobility. These vacancies annihilate as Schottky equilibria is re-established, whereas the latter condition does not lead to excess vacancy concentrations.

  11. Microgravity Smoldering Combustion Takes Flight

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Microgravity Smoldering Combustion (MSC) experiment lifted off aboard the Space Shuttle Endeavour in September 1995 on the STS-69 mission. This experiment is part of series of studies focused on the smolder characteristics of porous, combustible materials in a microgravity environment. Smoldering is a nonflaming form of combustion that takes place in the interior of combustible materials. Common examples of smoldering are nonflaming embers, charcoal briquettes, and cigarettes. The objective of the study is to provide a better understanding of the controlling mechanisms of smoldering, both in microgravity and Earth gravity. As with other forms of combustion, gravity affects the availability of air and the transport of heat, and therefore, the rate of combustion. Results of the microgravity experiments will be compared with identical experiments carried out in Earth's gravity. They also will be used to verify present theories of smoldering combustion and will provide new insights into the process of smoldering combustion, enhancing our fundamental understanding of this frequently encountered combustion process and guiding improvement in fire safety practices.

  12. Non-equilibrium Plasma-Assisted Combustion

    NASA Astrophysics Data System (ADS)

    Sun, Wenting

    As a promising method to enhance combustion, plasma-assisted combustion has drawn considerable attention. Due to the fast electron impact excitation and dissociation of molecules at low temperatures, plasma introduces new reaction pathways, changes fuel oxidation timescales, and can dramatically modify the combustion processes. In this dissertation, the radical generation from the plasma and its effect on flame extinction and ignition were investigated experimentally together with detailed numerical simulation on a counterflow CH4 diffusion flame. It was found that the atomic oxygen production played a dominant role in enhancing the chain-branching reaction pathways and accelerating fuel oxidation at near limit flame conditions. To understand the direct coupling effect between plasma and flame, a novel plasma-assisted combustion system with in situ discharge in a counterflow diffusion flame was developed. The ignition and extinction characteristics of CH4/O 2/He diffusion flames were investigated. For the first time, it was demonstrated that the strong plasma-flame coupling in in situ discharge could significantly modify the ignition/extinction characteristics and create a new fully stretched ignition S-curve. To understand low temperature kinetics of combustion, it is critical to measure the formation and decomposition of H2O2. A molecular beam mass spectrometry (MBMS) system was developed and integrated with a laminar flow reactor. H2O2 measurements were directly calibrated, and compared to kinetic models. The results confirmed that low and intermediate temperature DME oxidation produced significant amounts of H2O2. The experimental characterizations of important intermediate species including H2O2, CH2O and CH3OCHO provided new capabilities to investigate and improve the chemical kinetics especially at low temperatures. A numerical scheme for model reduction was developed to improve the computational efficiency in the simulation of combustion with detailed

  13. Baicalin inhibits the fenton reaction by enhancing electron transfer from Fe (2+) to dissolved oxygen.

    PubMed

    Nishizaki, Daisuke; Iwahashi, Hideo

    2015-01-01

    Sho-saiko-to is an herbal medicine that is known to have diverse pharmacological activities and has been used for the treatment of various infectious diseases. Here, we examined the effects of baicalin, a compound isolated from Sho-saiko-to, and the effects of the iron chelator quinolinic acid on the Fenton reaction. The control reaction mixture contained 0.1 M 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 0.2 mM H 2 O 2, 0.2 mM FeSO 4( NH 4)2 SO 4, and 40 mM sodium phosphate buffer (pH 7.4). Upon the addition of 0.6 mM baicalin or quinolinic acid to the control reaction mixture, the ESR peak heights of DMPO/OH radical adducts were measured as 32% ± 1% (baicalin) and 166% ± 27% (quinolinic acid) of that of the control mixture. In order to clarify why baicalin and quinolinic acid exerted opposite effects on the formation of hydroxyl radicals, we measured oxygen consumption in the presence of either compound. Upon the addition of 0.6 mM baicalin (or quinolinic acid) to the control reaction mixture without DMPO and H 2 O 2, the relative oxygen consumption rates were found to be 449% ± 40% (baicalin) and 18% ± 9% (quinolinic acid) of that of the control mixture without DMPO and H 2 O 2, indicating that baicalin facilitated the transfer of electrons from Fe (2+) to dissolved oxygen. Thus, the great majority of Fe (2+) turned into Fe (3+), and the formation of hydroxyl radicals was subsequently inhibited in this reaction.

  14. Oxy Coal Combustion at the US EPA

    EPA Science Inventory

    Oxygen enriched coal (oxy-coal) combustion is a developing, and potentially a strategically key technology intended to accommodate direct CO2 recovery and sequestration. Oxy-coal combustion is also intended for retrofit application to existing power plants. During oxy-coal comb...

  15. Deep hypothermia-enhanced autophagy protects PC12 cells against oxygen glucose deprivation via a mitochondrial pathway.

    PubMed

    Tang, Dang; Wang, Cheng; Gao, Yongjun; Pu, Jun; Long, Jiang; Xu, Wei

    2016-10-06

    Deep hypothermia is known for its organ-preservation properties, which is introduced into surgical operations on the brain and heart, providing both safety in stopping circulation as well as an attractive bloodless operative field. However, the molecular mechanisms have not been clearly identified. This study was undertaken to determine the influence of deep hypothermia on neural apoptosis and the potential mechanism of these effects in PC12 cells following oxygen-glucose deprivation. Deep hypothermia (18°C) was given to PC12 cells while the model of oxygen-glucose deprivation (OGD) induction for 1h. After 24h of reperfusion, the results showed that deep hypothermia decreased the neural apoptosis, and significantly suppressed overexpression of Bax, CytC, Caspase 3, Caspase 9 and cleaved PARP-1, and inhibited the reduction of Bcl-2 expression. While deep hypothermia increased the LC3II/LC3I and Beclin 1, an autophagy marker, which can be inhibited by 3-methyladenine (3-MA), indicating that deep hypothermia-enhanced autophagy ameliorated apoptotic cell death in PC12 cells subjected to OGD. Based on these findings we propose that deep hypothermia protects against neural apoptosis after the induction of OGD by attenuating the mitochondrial apoptosis pathway, moreover, the mechanism of these antiapoptosis effects is related to the enhancement of autophagy, which autophagy might provide a means of neuroprotection against OGD.

  16. Enhanced superconductivity, Kondo behavior, and negative-curvature resistivity of oxygen-irradiated thin films of aluminium

    NASA Astrophysics Data System (ADS)

    Sinnecker, E. H. C. P.; Sant'Anna, M. M.; ElMassalami, M.

    2017-02-01

    We followed the evolution of the normal and superconducting properties of Al thin films after each session of various successive oxygen irradiations at ambient temperature. Such irradiated films, similar to the granular ones, exhibit enhanced superconductivity, Kondo behavior, and negative-curvature resistivity. Two distinct roles of oxygen are identified: as a damage-causing projectile and as an implanted oxidizing agent. The former gives rise to the processes involved in the conventional recovery stages. The latter, considered within the context of the Cabrera-Mott model, gives rise to a multistep process which involves charges transfer and creation of stabilized vacancies and charged defects. Based on the outcome of this multistep process, we consider (i) the negative-curvature resistivity as a manifestation of a thermally assisted liberation of trapped electric charges, (ii) the Kondo contribution as a spin-flip scattering from paramagnetic, color-center-type defects, and (iii) the enhancement of Tc as being due to a lattice softening facilitated by the stabilized defects and vacancies. The similarity in the phase diagrams of granular and irradiated films as well as the aging effects are discussed along the same line of reasoning.

  17. 3D Late Gadolinium Enhancement in a Single Prolonged Breath-hold using Supplemental Oxygenation and Hyperventilation

    PubMed Central

    Roujol, Sébastien; Basha, Tamer A.; Akçakaya, Mehmet; Foppa, Murilo; Chan, Raymond H.; Kissinger, Kraig V.; Goddu, Beth; Berg, Sophie; Manning, Warren J.; Nezafat, Reza

    2013-01-01

    Purpose: To evaluate the feasibility of 3D single breath-hold late gadolinium enhancement (LGE) of the left ventricle (LV) using supplemental oxygen and hyperventilation and compressed-sensing acceleration. Methods: Breath-hold metrics (breath-hold duration, diaphragmatic/LV position drift, and maximum variation of RR interval) without and with supplemental oxygen and hyperventilation were assessed in healthy adult subjects using a real time single shot acquisition. Ten healthy subjects and 13 patients then underwent assessment of the proposed 3D breath-hold LGE acquisition (FOV=320×320×100 mm3, resolution=1.6×1.6×5.0 mm3, acceleration rate of 4) and a free breathing acquisition with right hemidiaphragm navigator (NAV) respiratory gating. Semi-quantitative grading of overall image quality, motion artifact, myocardial nulling, and diagnostic value was performed by consensus of two blinded observers. Results: Supplemental oxygenation and hyperventilation increased the breath-hold duration (35±11 s to 58±21 s, p<0.0125) without significant impact on diaphragmatic/LV position drift or maximum variation of RR interval (both p>0.01). LGE images were of similar quality when compared to free breathing acquisitions but with reduced total scan time (85±22 s to 35±6 s, p<0.001). Conclusions: Supplemental oxygenation and hyperventilation allow for prolonged breath-holding and enable single breath-hold 3D accelerated LGE with similar image quality as free breathing with NAV. PMID:24186772

  18. Intensity enhancement of the vibrational spectrum of oxygen when attached to a platinum nanocluster

    NASA Astrophysics Data System (ADS)

    Seminario, Jorge M.; Saenz, Lina R.

    2006-11-01

    Detecting single molecules is a technical and scientific challenge and requires to increase the number of molecules or their cross section to a radiation field in order to have a detectable signal. We demonstrate for a single molecule of oxygen that, by attaching the molecule to a nanocluster, the molecule signature spectrum is transferred to the larger complex (molecule cluster). Therefore, the detection can focus on the complex, which can have a much larger cross section, rather than on the small molecule. This is based on the concept of signature transfer, which can be used to detect in the cluster several other properties of the attached molecule.

  19. Enhancement of Tc in Pb-based cuprate superconductors prepared at high-oxygen-pressure

    NASA Astrophysics Data System (ADS)

    Ohta, M.; Tsutsumi, M.; Yoshimoto, J.; Okai, B.

    1991-12-01

    Samples of nominal compositions, In 0.3Pb 0.7Sr 2Y 0.2Ca 0.6Cu 2O y and Pb 0.5Sr 2.0Y 0.1Ca 0.8Cu 2O y were heat-treated under high oxygen pressure of 6 GPa at 1150°C. The recovered specimens showed superconductivity above 85 K, in the former Tc being nearly 90 K. The content of Indium incorporated in the superconducting phase was found to be less than about 2 atomic% of the total constituting cations.

  20. Antipollution combustion chamber

    SciTech Connect

    Caruel, J.E.; Gastebois, P.M.

    1981-01-27

    The invention concerns a combustion chamber for turbojet engines. The combustion chamber is of the annular type and consists of two coaxial flame tubes opening into a common dilution and mixing zone. The inner tube is designed for low operating ratings of the engine, the outer tube for high ratings. Air is injected as far upstream as possible into the dilution zone, to enhance the homogenization of the gaseous flow issuing from the two tubes prior to their passage into the turbine and to assure the optimum radial distribution of temperatures. The combustion chamber according to the invention finds application in a particularly advantageous manner in turbojet engines used in aircraft propulsion because of the reduced emission of pollutants it affords.

  1. Protoporphyrin IX Functionalised AgSiO2 Core-shell Nanoparticle: Plasmonic Enhancement of Fluorescence and Singlet Oxygen Production.

    PubMed

    Lismont, Marjorie; Dreesen, Laurent; Heinrichs, Benoît; Páez, Carlos A

    2015-12-15

    Metal-enhanced processes arising from the coupling of a dye with metallic nanoparticles (NPs) have been widely reported. However, few studies have simultaneously investigated these mechanisms from the viewpoint of dye fluorescence and photoactivity. Herein, protoporphyrin IX (PpIX) is grafted onto the surface of silver core silica shell NPs in order to investigate the effect of silver (Ag) localised surface plasmon resonance (LSPR) on PpIX fluorescence and PpIX singlet oxygen ((1) O2 ) production. Using two Ag core sizes, we report a systematic study of these photophysical processes as a function of silica (SiO2 ) spacer thickness, LSPR band position and excitation wavelength. The excitation of Ag NP LSPR, which overlaps the PpIX absorption band, leads to the concomitant enhancement of PpIX fluorescence and (1) O2 production independently of the Ag core size, but in a more pronounced way for larger Ag cores. These enhancements result from the increase of the PpIX excitation rate through the LSPR excitation and decrease when the distance between PpIX and Ag NPs increases. A maximum fluorescence enhancement of up to 14-fold, together with an increase of photogenerated (1) O2 production of up to 5 times are obtained using 100 nm Ag cores coated with a 5 nm thick silica coating. This article is protected by copyright. All rights reserved.

  2. Three-dimensional ordered mesoporous Co3O4 enhanced by Pd for oxygen evolution reaction

    NASA Astrophysics Data System (ADS)

    Qu, Qing; Zhang, Jian-Hua; Wang, Jing; Li, Qing-Yu; Xu, Chang-Wei; Lu, Xihong

    2017-01-01

    Considerable efforts have been devoted recently to design and fabrication of high performance and low cost electrocatalysts for oxygen evolution reaction (OER). However, catalytic activity of current electrocatalysts is usually restricted by high onset potential and limited active sites. Herein, we fabricated three-dimensional (3D) highly ordered mesoporous Pd-Co3O4 composite materials as excellent electrocatalysts for OER in alkaline solution with high activity and stability. Three-dimensional highly ordered mesoporous Co3O4 material was firstly synthesized using mesoporous silica KIT-6 as hard template. Then, Pd-Co3O4 nanomaterials were prepared by a simple reduction method. The as-prepared 3D mesoporous Pd-Co3O4 catalysts have ordered mesoporous structure with a high surface area of 81.0 m2 g‑1. Three-dimensional highly ordered mesoporous structure can facilitate diffusion and penetration of electrolyte and oxygen. Moreover, the catalysts can also keep catalyst particles in a well dispersed condition with more catalytic active sites. Electrochemical measurements reveal that the 3D mesoporous Pd-Co3O4 catalysts exhibit superior performance in alkaline solution with low onset potential (0.415 V vs. SCE) and excellent long-duration cycling stability.

  3. Heterogeneous Au-Pt nanostructures with enhanced catalytic activity toward oxygen reduction.

    PubMed

    Ye, Feng; Liu, Hui; Hu, Weiwei; Zhong, Junyu; Chen, Yingying; Cao, Hongbin; Yang, Jun

    2012-03-14

    Heterogeneous Au-Pt nanostructures have been synthesized using a sacrificial template-based approach. Typically, monodispersed Au nanoparticles are prepared first, followed by Ag coating to form core-shell Au-Ag nanoparticles. Next, the galvanic replacement reaction between Ag shells and an aqueous H(2)PtCl(6) solution, whose chemical reaction can be described as 4Ag + PtCl(6)(2-)→ Pt + 4AgCl + 2Cl(-), is carried out at room temperature. Pure Ag shell is transformed into a shell made of Ag/Pt alloy by galvanic replacement. The AgCl formed simultaneously roughens the surface of alloy Ag-Pt shells, which can be manipulated to create a porous Pt surface for oxygen reduction reaction. Finally, Ag and AgCl are removed from core-shell Au-Ag/Pt nanoparticles using bis(p-sulfonatophenyl)phenylphosphane dihydrate dipotassium salt to produce heterogeneous Au-Pt nanostructures. The heterogeneous Au-Pt nanostructures have displayed superior catalytic activity towards oxygen reduction in direct methanol fuel cells because of the electronic coupling effect between the inner-placed Au core and the Pt shell.

  4. Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

    PubMed Central

    Hensling, Felix V. E.; Xu, Chencheng; Gunkel, Felix; Dittmann, Regina

    2017-01-01

    The reduction of oxides during annealing and growth in low pressure processes is a widely known problem. We hence investigate the influence of mere annealing and of growth in vacuum systems to shed light on the reasons behind the reduction of perovskites. When comparing the existing literature regarding the reduction of the perovskite model material SrTiO3 it is conspicuous that one finds different oxygen pressures required to achieve reduction for vacuum annealing and for chemically controlled reducing atmospheres. The unraveling of this discrepancy is of high interest for low pressure physical vapor depositions of thin films heterostructures to gain further understanding of the reduction of the SrTiO3. For thermal annealing, our results prove the attached measurement devices (mass spectrometer/ cold cathode gauge) to be primarily responsible for the reduction of SrTiO3 in the deposition chamber by shifting the thermodynamic equilibrium to a more reducing atmosphere. We investigated the impact of our findings on the pulsed laser deposition growth at low pressure for LaAlO3/SrTiO3. During deposition the reduction triggered by the presence of the laser plume dominates and the impact of the measurement devices plays a minor role. During post annealing a complete reoxidization of samples is inhibited by an insufficient supply of oxygen. PMID:28091517

  5. Nanoparticle-enhanced spectral photoacoustic tomography: effect of oxygen saturation and tissue heterogeneity

    NASA Astrophysics Data System (ADS)

    Vogt, William C.; Jia, Congxian; Wear, Keith A.; Garra, Brian S.; Pfefer, T. Joshua

    2016-03-01

    Molecular imaging for breast cancer detection, infectious disease diagnostics and preclinical animal research may be achievable through combined use of targeted exogenous agents - such as nanoparticles - and spectral Photoacoustic Tomography (PAT). However, tissue heterogeneity can alter fluence distributions and acoustic propagation, corrupting measured PAT absorption spectra and complicating in vivo nanoparticle detection and quantitation. Highly absorptive vascular structures represent a common confounding factor, and variations in vessel hemoglobin saturation (SO2) may alter spectral content of signals from adjacent/deeper regions. To evaluate the impact of this effect on PAT nanoparticle detectability, we constructed heterogeneous phantoms with well-characterized channel-inclusion geometries and biologically relevant optical and acoustic properties. Phantoms contained an array of tubes at several depths filled with hemoglobin solutions doped with varying concentrations of gold nanorods with an absorption peak at 780 nm. Both overlying and target network SO2 was tuned using sodium dithionite. Phantoms were imaged from 700 to 900 nm using a custom PAT system comprised of a tunable pulsed laser and a research-grade ultrasound system. Recovered nanoparticle spectra were analyzed and compared with results from both spectrophotometry and PAT data from waterimmersed tubes containing blood and nanoparticle solutions. Results suggested that nanoparticle selection for a given PAT application should take into account expected oxygenation states of both target blood vessel and background tissue oxygenation to achieve optimal performance.

  6. Reduction of blood oxygen levels enhances postprandial cardiac hypertrophy in Burmese python (Python bivittatus).

    PubMed

    Slay, Christopher E; Enok, Sanne; Hicks, James W; Wang, Tobias

    2014-05-15

    Physiological cardiac hypertrophy is characterized by reversible enlargement of cardiomyocytes and changes in chamber architecture, which increase stroke volume and via augmented convective oxygen transport. Cardiac hypertrophy is known to occur in response to repeated elevations of O2 demand and/or reduced O2 supply in several species of vertebrate ectotherms, including postprandial Burmese pythons (Python bivittatus). Recent data suggest postprandial cardiac hypertrophy in P. bivittatus is a facultative rather than obligatory response to digestion, though the triggers of this response are unknown. Here, we hypothesized that an O2 supply-demand mismatch stimulates postprandial cardiac enlargement in Burmese pythons. To test this hypothesis, we rendered animals anemic prior to feeding, essentially halving blood oxygen content during the postprandial period. Fed anemic animals had heart rates 126% higher than those of fasted controls, which, coupled with a 71% increase in mean arterial pressure, suggests fed anemic animals were experiencing significantly elevated cardiac work. We found significant cardiac hypertrophy in fed anemic animals, which exhibited ventricles 39% larger than those of fasted controls and 28% larger than in fed controls. These findings support our hypothesis that those animals with a greater magnitude of O2 supply-demand mismatch exhibit the largest hearts. The 'low O2 signal' stimulating postprandial cardiac hypertrophy is likely mediated by elevated ventricular wall stress associated with postprandial hemodynamics.

  7. Three-dimensional ordered mesoporous Co3O4 enhanced by Pd for oxygen evolution reaction

    PubMed Central

    Qu, Qing; Zhang, Jian-Hua; Wang, Jing; Li, Qing-Yu; Xu, Chang-Wei; Lu, Xihong

    2017-01-01

    Considerable efforts have been devoted recently to design and fabrication of high performance and low cost electrocatalysts for oxygen evolution reaction (OER). However, catalytic activity of current electrocatalysts is usually restricted by high onset potential and limited active sites. Herein, we fabricated three-dimensional (3D) highly ordered mesoporous Pd-Co3O4 composite materials as excellent electrocatalysts for OER in alkaline solution with high activity and stability. Three-dimensional highly ordered mesoporous Co3O4 material was firstly synthesized using mesoporous silica KIT-6 as hard template. Then, Pd-Co3O4 nanomaterials were prepared by a simple reduction method. The as-prepared 3D mesoporous Pd-Co3O4 catalysts have ordered mesoporous structure with a high surface area of 81.0 m2 g−1. Three-dimensional highly ordered mesoporous structure can facilitate diffusion and penetration of electrolyte and oxygen. Moreover, the catalysts can also keep catalyst particles in a well dispersed condition with more catalytic active sites. Electrochemical measurements reveal that the 3D mesoporous Pd-Co3O4 catalysts exhibit superior performance in alkaline solution with low onset potential (0.415 V vs. SCE) and excellent long-duration cycling stability. PMID:28134348

  8. Unraveling the enhanced Oxygen Vacancy Formation in Complex Oxides during Annealing and Growth

    NASA Astrophysics Data System (ADS)

    Hensling, Felix V. E.; Xu, Chencheng; Gunkel, Felix; Dittmann, Regina

    2017-01-01

    The reduction of oxides during annealing and growth in low pressure processes is a widely known problem. We hence investigate the influence of mere annealing and of growth in vacuum systems to shed light on the reasons behind the reduction of perovskites. When comparing the existing literature regarding the reduction of the perovskite model material SrTiO3 it is conspicuous that one finds different oxygen pressures required to achieve reduction for vacuum annealing and for chemically controlled reducing atmospheres. The unraveling of this discrepancy is of high interest for low pressure physical vapor depositions of thin films heterostructures to gain further understanding of the reduction of the SrTiO3. For thermal annealing, our results prove the attached measurement devices (mass spectrometer/ cold cathode gauge) to be primarily responsible for the reduction of SrTiO3 in the deposition chamber by shifting the thermodynamic equilibrium to a more reducing atmosphere. We investigated the impact of our findings on the pulsed laser deposition growth at low pressure for LaAlO3/SrTiO3. During deposition the reduction triggered by the presence of the laser plume dominates and the impact of the measurement devices plays a minor role. During post annealing a complete reoxidization of samples is inhibited by an insufficient supply of oxygen.

  9. Microgravity Combustion Diagnostics Workshop

    NASA Technical Reports Server (NTRS)

    Santoro, Gilbert J. (Editor); Greenberg, Paul S. (Editor); Piltch, Nancy D. (Editor)

    1988-01-01

    Through the Microgravity Science and Applications Division (MSAD) of the Office of Space Science and Applications (OSSA) at NASA Headquarters, a program entitled, Advanced Technology Development (ATD) was promulgated with the objective of providing advanced technologies that will enable the development of future microgravity science and applications experimental flight hardware. Among the ATD projects one, Microgravity Combustion Diagnostics (MCD), has the objective of developing advanced diagnostic techniques and technologies to provide nonperturbing measurements of combustion characteristics and parameters that will enhance the scientific integrity and quality of microgravity combustion experiments. As part of the approach to this project, a workshop was held on July 28 and 29, 1987, at the NASA Lewis Research Center. A small group of laser combustion diagnosticians met with a group of microgravity combustion experimenters to discuss the science requirements, the state-of-the-art of laser diagnostic technology, and plan the direction for near-, intermediate-, and long-term programs. This publication describes the proceedings of that workshop.

  10. Enhanced acetone-sensing performance of Au/ZnO hybrids synthesized using a solution combustion method

    NASA Astrophysics Data System (ADS)

    Li, Yan; Lv, Tan; Zhao, Fang-Xian; Wang, Qiong; Lian, Xiao-Xue; Zou, Yun-Ling

    2015-09-01

    ZnO semiconductor hybrids with high response and selectivity to various gases have received enormous attention for practical applications. In this work, Au/ZnO nanoparticles were synthesized via a facile solution combustion method, using chlorauric acid and zinc nitrate as the raw materials. X-ray diffraction and field-emission scanning microscopy revealed that the Au/ZnO nanoparticles, with diameters of 50-300 nm, were mainly composed of the ZnO wurtzite phase and Au metal phase with a face-centered structure. The gas-sensing results indicated that the Au (4 at. %)/ZnO-based sensor exhibited the highest response and selectivity among all the as-obtained Au/ZnO products; moreover, its response to acetone was approximately 3 times greater than that of the pure ZnO, and the response (173) of the sensor to acetone was 2.4, 9.8, 17, and 22 times higher than that to C2H5OH, H2, CO, and CH4 at 300°C, respectively. [Figure not available: see fulltext.

  11. Evidence for enhanced phosphorus regeneration from marine sediments overlain by oxygen depleted waters

    SciTech Connect

    Ingall, E.; Jahnki, R.

    1994-06-01

    Phosphorus regeneration and burial fluxes determined from in situ benthic flux chamber and solid phase measurements at sites on the Californian continental margin, Peruvian continental slope, North Carolina continental slope, and from the Santa Monica basin, California are reported. Comparison of these sites indicates that O{sub 2}-depleted bottomwaters enhance P regeneration from sediments, diminishing overall phosphorus burial efficiency. Based on these observations, a positive feedback, linking ocean anoxia, enhanced benthic phosphorus regeneration, and marine productivity is proposed. On shorter timescales, these results also suggest that O{sub 2} depletion in coastal regions caused by eutrophication may enhance P regeneration from sediments, thereby providing additional P necessary for increased biological productivity. 42 refs., 2 figs., 2 tabs.

  12. Reproducibility and comparison of oxygen-enhanced T1 quantification in COPD and asthma patients

    PubMed Central

    Jobst, Bertram J.; Anjorin, Angela; Sedlaczek, Oliver; Wolf, Ursula; Terekhov, Maxim; Hoffmann, Christian; Ley, Sebastian; Düber, Christoph; Biederer, Jürgen; Kauczor, Hans-Ulrich; Jakob, Peter M.; Wielpütz, Mark O.

    2017-01-01

    T1 maps have been shown to yield useful diagnostic information on lung function in patients with chronic obstructive pulmonary disease (COPD) and asthma, both for native T1 and ΔT1, the relative reduction while breathing pure oxygen. As parameter quantification is particularly interesting for longitudinal studies, the purpose of this work was both to examine the reproducibility of lung T1 mapping and to compare T1 found in COPD and asthma patients using IRSnapShotFLASH embedded in a full MRI protocol. 12 asthma and 12 COPD patients (site 1) and further 15 COPD patients (site 2) were examined on two consecutive days. In each patient, T1 maps were acquired in 8 single breath-hold slices, breathing first room air, then pure oxygen. Maps were partitioned into 12 regions each to calculate average values. In asthma patients, the average T1,RA = 1206ms (room air) was reduced to T1,O2 = 1141ms under oxygen conditions (ΔT1 = 5.3%, p < 5⋅10−4), while in COPD patients both native T1,RA = 1125ms was significantly shorter (p < 10−3) and the relative reduction to T1,O2 = 1081ms on average ΔT1 = 4.2%(p < 10−5). On the second day, with T1,RA = 1186ms in asthma and T1,RA = 1097ms in COPD, observed values were slightly shorter on average in all patient groups. ΔT1 reduction was the least repeatable parameter and varied from day to day by up to 23% in individual asthma and 30% in COPD patients. While for both patient groups T1 was below the values reported for healthy subjects, the T1 and ΔT1 found in asthmatics lies between that of the COPD group and reported values for healthy subjects, suggesting a higher blood volume fraction and better ventilation. However, it could be demonstrated that lung T1 quantification is subject to notable inter-examination variability, which here can be attributed both to remaining contrast agent from the previous day and the increased dependency of lung T1 on perfusion and thus current lung state. PMID:28207845

  13. Partial neuromuscular blockade in humans enhances muscle blood flow during exercise independently of muscle oxygen uptake and acetylcholine receptor blockade.

    PubMed

    Hellsten, Ylva; Krustrup, Peter; Iaia, F Marcello; Secher, Niels H; Bangsbo, Jens

    2009-04-01

    This study examined the role of acetylcholine for skeletal muscle blood flow during exercise by use of the competitive neuromuscular blocking agent cisatracurium in combination with the acetylcholine receptor blocker glycopyrrone. Nine healthy male subjects performed a 10-min bout of one-legged knee-extensor exercise (18 W) during control conditions and with cisatracurium blockade, as well as with cisatracurium blockade with prior glycopyrrone infusion. Thigh blood flow and vascular conductance in control and with cisatracurium infusion were similar at rest and during passive movement of the leg, but higher (P < 0.05) during exercise with cisatracurium than in control (3.83 +/- 0.42 vs. 2.78 +/- 0.21 l/min and 26.9 +/- 3.4 vs. 21.8 +/- 2.0 ml.min(-1).mmHg(-1) at the end of exercise). Thigh oxygen uptake was similar in control and with cisatracurium infusion both at rest and during exercise, being 354 +/- 33 and 406 +/- 34 ml/min, at the end of exercise. Combined infusion of cisatracurium and glycopyrrone caused a similar increase in blood flow as cisatracurium infusion alone. The current results demonstrate that neuromuscular blockade leads to enhanced thigh blood flow and vascular conductance during exercise, events that are not associated with either acetylcholine or an increased oxygen demand. The results do not support an essential role for acetylcholine, released form the neuromuscular junction, in exercise hyperemia or for the enhanced blood flow during neuromuscular blockade. The enhanced exercise hyperemia during partial neuromuscular blockade may be related to a greater recruitment of fast-twitch muscle fibers.

  14. Low dose gamma irradiation enhances defined signaling components of intercellular reactive oxygen-mediated apoptosis induction

    NASA Astrophysics Data System (ADS)

    Bauer, G.

    2011-01-01

    Transformed cells are selectively removed by intercellular ROS-mediated induction of apoptosis. Signaling is based on the HOCl and the NO/peroxynitrite pathway (major pathways) and the nitryl chloride and the metal-catalyzed Haber-Weiss pathway (minor pathways). During tumor progression, resistance against intercellular induction of apoptosis is acquired through expression of membrane-associated catalase. Low dose radiation of nontransformed cells has been shown to enhance intercellular induction of apoptosis. The present study was performed to define the signaling components which are modulated by low dose gamma irradiation. Low dose radiation induced the release of peroxidase from nontransformed, transformed and tumor cells. Extracellular superoxide anion generation was strongly enhanced in the case of transformed cells and tumor cells, but not in nontransformed cells. Enhancement of peroxidase release and superoxide anion generation either increased intercellular induction of apoptosis of transformed cells, or caused a partial protection under specific signaling conditions. In tumor cells, low dose radiation enhanced the production of major signaling components, but this had no effect on apoptosis induction, due to the strong resistance mechanism of tumor cells. Our data specify the nature of low dose radiation-induced effects on specific signaling components of intercellular induction of apoptosis at defined stages of multistep carcinogenesis.

  15. Covalent grafting of carbon nanotubes with a biomimetic heme model compound to enhance oxygen reduction reactions.

    PubMed

    Wei, Ping-Jie; Yu, Guo-Qiang; Naruta, Yoshinori; Liu, Jin-Gang

    2014-06-23

    The oxygen reduction reaction (ORR) is one of the most important reactions in both life processes and energy conversion systems. The replacement of noble-metal Pt-based ORR electrocatalysts by nonprecious-metal catalysts is crucial for the large-scale commercialization of automotive fuel cells. Inspired by the mechanisms of dioxygen activation by metalloenzymes, herein we report a structurally well-defined, bio-inspired ORR catalyst that consists of a biomimetic model compound-an axial imidazole-coordinated porphyrin-covalently attached to multiwalled carbon nanotubes. Without pyrolysis, this bio-inspired electrocatalyst demonstrates superior ORR activity and stability compared to those of the state-of-the-art Pt/C catalyst in both acidic and alkaline solutions, thus making it a promising alternative as an ORR electrocatalyst for application in fuel-cell technology.

  16. Tc enhancement of excess Sr-doped Bi-2223 oxides by control of oxygen content

    NASA Astrophysics Data System (ADS)

    Miura, N.; Sakata, F.; Shimizu, Y.; Deshimaru, Y.; Yamazoe, N.

    1994-12-01

    The superconducting properties of excess Sr-doped 2223 phase samples, Bi 1.84Pb 0.34Sr 1.91+xCa 2.03Cu 3.06O y ( x=0.1, 0.3, 0.5, 1.0, 1.5), were examined. All the oxides as-prepared showed almost the same Tc of 109∼110 K, After heat-treatment in He at 600 °C for 3h, however, Tc increased up to 114∼115 K for the oxides with x=0.3∼, and decreased down to 102∼106 K for x=0∼0.1. The oxygen contents of the oxides as determined by iodometry increased with increasing x and slightly decreased with the heat-treatment in He. The heat treatment also brough about small increases in lattice constant of c-axis.

  17. Enhanced Oxygen Reduction Activity In Acid By Tin-Oxide Supported Au Nanoparticle Catalysts

    SciTech Connect

    Baker,W.; Pietron, J.; Teliska, M.; Bouwman, P.; Ramaker, D.; Swider-Lyons, K.

    2006-01-01

    Gold nanoparticles supported on hydrous tin-oxide (Au-SnO{sub x}) are active for the four-electron oxygen reduction reaction in an acid electrolyte. The unique electrocatalytic of the Au-SnO is confirmed by the low amount of peroxide detected with rotating ring-disk electrode voltammetry and Koutecky-Levich analysis. In comparison, 10 wt % Au supported on Vulcan carbon and SnO{sub x} catalysts both produce significant peroxide in the acid electrolyte, indicating only a two-electron reduction reaction. Characterization of the Au-SnO{sub x} catalyst reveals a high-surface area, amorphous support with 1.7 nm gold metal particles. The high catalytic activity of the Au-SnO is attributed to metal support interactions. The results demonstrate a possible path to non-Pt catalysts for proton exchange membrane fuel cell cathodes.

  18. Enhanced electrocatalytic oxygen evolution of α-Co(OH)2 nanosheets on carbon nanotube/polyimide films

    NASA Astrophysics Data System (ADS)

    Jiang, Yimin; Li, Xin; Wang, Tingxia; Wang, Chunming

    2016-05-01

    The future of energy supply depends on innovative breakthroughs in the development of highly efficient, sustainable and low-cost systems for renewable energy conversion and storage. Water splitting is a promising and appealing solution. In this work, we report Co(OH)2 on the carbon nanotube/polyimide film (PI/CNT-Co(OH)2) as an efficient electrocatalyst for the oxygen evolution reaction (OER). The PI/CNT film allows intimate growth of Co(OH)2 nanosheets on its surface. The nanosheet structure of Co(OH)2 and the underlying PI/CNT film facilitate the good OER performance of the PI/CNT-Co(OH)2 film. Co(OH)2 nanosheets on the PI/CNT film afford an earlier onset of oxygen evolution, a low overpotential of 317 mV and a small Tafel slope of 49 mV per decade in alkaline media. This work applies the PI/CNT film in water splitting to enhance the OER electrocatalytic activity of Co(OH)2, which opens up a promising avenue for the exploration of highly active electrocatalysts that can replace noble-metal based catalysts for the OER.The future of energy supply depends on innovative breakthroughs in the development of highly efficient, sustainable and low-cost systems for renewable energy conversion and storage. Water splitting is a promising and appealing solution. In this work, we report Co(OH)2 on the carbon nanotube/polyimide film (PI/CNT-Co(OH)2) as an efficient electrocatalyst for the oxygen evolution reaction (OER). The PI/CNT film allows intimate growth of Co(OH)2 nanosheets on its surface. The nanosheet structure of Co(OH)2 and the underlying PI/CNT film facilitate the good OER performance of the PI/CNT-Co(OH)2 film. Co(OH)2 nanosheets on the PI/CNT film afford an earlier onset of oxygen evolution, a low overpotential of 317 mV and a small Tafel slope of 49 mV per decade in alkaline media. This work applies the PI/CNT film in water splitting to enhance the OER electrocatalytic activity of Co(OH)2, which opens up a promising avenue for the exploration of highly active

  19. Labor Contractions Enhance Oxygenation and Behavioral Activity of Newborn Rat Pups

    NASA Technical Reports Server (NTRS)

    Mills, N. A.; Baer, L. A.; Ronca, A. E.; Balton, Bonnie (Technical Monitor)

    2002-01-01

    Labor contractions help instigate behavioral responses at birth (viz., breathing and suckling) that are vital for the newborn's adaptation to the extrauterine world (Ronca et al., 1996). In the present study, we analyzed the role of labor contractions in postpartum oxygenation and behavioral activity of newborn rat pups. Newborns were observed following either vaginal (V) or cesarean delivery. For cesarean delivery, day 21 pregnant dams' were administered a spinal transaction to eliminate lower body sensation, a laparotomy was performed and the uterus was maintained in a heated (37.5 C) bath. Four rat fetuses in one of the dams' paired uterine horn were compressed (C) to Simulate labor contractions (20 sec/min for 10 min) while four fetuses in the opposite horn were not compressed (NC). Fetuses were surgically removed from the uterus, stroked with a soft brush to mimic postnatal licking by the dam, the umbilical cord occluded. Pups were exposed to room temperature (22 C) for one hr, then nest temperature (33 C) for one hr. PO2, CO2, and O2, saturation were determined at 0, 30, 60, or 120 min post delivery using a blood gas analyzer. V and C delivered neonates showed comparable rates of PO2, CO2 and O2 saturation whereas NC neonates showed depressed levels at all time points (p<0.05). Respiratory rates of V, C and NC neonates increased significantly (p<0.05) over the first two postpartum hrs and did not differ across groups. Postpartum behavioral activity was significantly greater in V and C conditions and positively correlated with postnatal oxygenation. These findings provide further evidence for importance of labor contractions in early postpartum adaptation.

  20. Flameless Combustion for Gas Turbines

    NASA Astrophysics Data System (ADS)

    Gutmark, Ephraim; Li, Guoqiang; Overman, Nick; Cornwell, Michael; Stankovic, Dragan; Fuchs, Laszlo; Milosavljevic, Vladimir

    2006-11-01

    An experimental study of a novel flameless combustor for gas turbine engines is presented. Flameless combustion is characterized by distributed flame and even temperature distribution for high preheat air temperature and large amount of recirculating low oxygen exhaust gases. Extremely low emissions of NOx, CO, and UHC are reported. Measurements of the flame chemiluminescence, CO and NOx emissions, acoustic pressure, temperature and velocity fields as a function of the preheat temperature, inlet air mass flow rate, exhaust nozzle contraction ratio, and combustor chamber diameter are described. The data indicate that larger pressure drop promotes flameless combustion and low NOx emissions at the same flame temperature. High preheated temperature and flow rates also help in forming stable combustion and therefore are favorable for flameless combustion.

  1. On-line measurement of heat of combustion

    NASA Technical Reports Server (NTRS)

    Chaturvedi, S. K.; Chegini, H.

    1988-01-01

    An experimental method for an on-line measurement of heat of combustion of a gaseous hydrocarbon fuel mixture of unknown composition is developed. It involves combustion of a test gas with a known quantity of air to achieve a predetermined oxygen concentration level in the combustion products. This is accomplished by a feedback controller which maintains the gas volumetric flow rate at a level consistent with the desired oxygen concentration in the products. The heat of combustion is determined from a known correlation with the gas volumetric flow rate. An on-line microcomputer accesses the gas volumetric flow data, and displays the heat of combustion values at desired time intervals.

  2. Enhanced Intrinsic Catalytic Activity of λ-MnO2 by Electrochemical Tuning and Oxygen Vacancy Generation.

    PubMed

    Lee, Sanghan; Nam, Gyutae; Sun, Jie; Lee, Jang-Soo; Lee, Hyun-Wook; Chen, Wei; Cho, Jaephil; Cui, Yi

    2016-07-18

    Chemically prepared λ-MnO2 has not been intensively studied as a material for metal-air batteries, fuel cells, or supercapacitors because of their relatively poor electrochemical properties compared to α- and δ-MnO2 . Herein, through the electrochemical removal of lithium from LiMn2 O4 , highly crystalline λ-MnO2 was prepared as an efficient electrocatalyst for the oxygen reduction reaction (ORR). The ORR activity of the material was further improved by introducing oxygen vacancies (OVs) that could be achieved by increasing the calcination temperature during LiMn2 O4 synthesis; a concentration of oxygen vacancies in LiMn2 O4 could be characterized by its voltage profile as the cathode in a lithiun-metal half-cell. λ-MnO2-z prepared with the highest OV exhibited the highest diffusion-limited ORR current (5.5 mA cm(-2) ) among a series of λ-MnO2-z electrocatalysts. Furthermore, the number of transferred electrons (n) involved in the ORR was >3.8, indicating a dominant quasi-4-electron pathway. Interestingly, the catalytic performances of the samples were not a function of their surface areas, and instead depended on the concentration of OVs, indicating enhancement in the intrinsic catalytic activity of λ-MnO2 by the generation of OVs. This study demonstrates that differences in the electrochemical behavior of λ-MnO2 depend on the preparation method and provides a mechanism for a unique catalytic behavior of cubic λ-MnO2 .

  3. Enhanced nitrogen removal in constructed wetlands: effects of dissolved oxygen and step-feeding.

    PubMed

    Li, Fengmin; Lu, Lun; Zheng, Xiang; Ngo, Huu Hao; Liang, Shuang; Guo, Wenshan; Zhang, Xiuwen

    2014-10-01

    Four horizontal subsurface flow constructed wetlands (HSFCWs), named HSFCW1 (three-stage, without step-feeding), HSFCW2 (three-stage, with step-feeding), HSFCW3 (five-stage, without step-feeding) and HSFCW4 (five-stage, with step-feeding) were designed to investigate the effects of dissolved oxygen (DO) and step-feeding on nitrogen removal. High removal of 90.9% COD, 99.1% ammonium nitrogen and 88.1% total nitrogen (TN) were obtained simultaneously in HSFCW4 compared with HSFCW1-3. The excellent TN removal of HSFCW4 was due to artificial aeration provided sufficient DO for nitrification and the favorable anoxic environment created for denitrification. Step-feeding was a crucial factor because it provided sufficient carbon source (high COD: nitrate ratio of 14.3) for the denitrification process. Microbial activities and microbial abundance in HSFCW4 was found to be influenced by DO distribution and step-feeding, and thus improve TN removal. These results suggest that artificial aeration combined with step-feeding could achieve high nitrogen removal in HSFCWs.

  4. Proton enhanced dynamic battery chemistry for aprotic lithium–oxygen batteries

    DOE PAGES

    Zhu, Yun Guang; Liu, Qi; Rong, Yangchun; ...

    2017-02-06

    Water is generally considered to be deteriorating to the performance of aprotic Li-air batteries, while it is challenged by the disparate effects observed recently. This has provoked a range of discussion on the role of water and its impact on the battery operation. In this work, a distinct battery chemistry that prevails in water-contaminated aprotic Li-O2 batteries was discovered. Both lithium ions and protons were found to be involved in the oxygen reduction (ORR) and evolution reactions (OER), and LiOOH and LiOH were identified as predominant materials in the discharge product. As a new lithium compound, the crystallographic and spectroscopicmore » characteristics of LiOOH∙H2O were scrutinized both experimentally and theoretically. The structure of LiOOH∙H2O was found to be closely related to that of LiOH∙H2O implying a fast conversion kinetics between the two phases. Intriguingly, LiOOH∙H2O exhibits superior dynamic property towards the reaction with I3-, which renders considerably lower overpotential during the charging process. We anticipate that the new battery chemistry unveiled in this mechanistic study would provide important insights to the understanding of nominally aprotic Li-O2 batteries and help to tackle the critical issues confronted.« less

  5. Triggering comprehensive enhancement in oxygen evolution reaction by using newly created solvent

    PubMed Central

    Chen, Hsiao-Chien; Mai, Fu-Der; Yang, Kuang-Hsuan; Chen, Liang-Yih; Yang, Chih-Ping; Liu, Yu-Chuan

    2016-01-01

    Theoretical calculations indicate that the properties of confined liquid water, or liquid water at surfaces, are dramatically different from those of liquid bulk water. Here we present an experimentally innovative strategy on comprehensively efficient oxygen evolution reaction (OER) utilizing plasmon-induced activated water, creating from hot electron decay at resonantly illuminated Au nanoparticles (NPs). Compared to conventional deionized (DI) water, the created water owns intrinsically reduced hydrogen-bonded structure and a higher chemical potential. The created water takes an advantage in OER because the corresponding activation energy can be effectively reduced by itself. Compared to DI water-based solutions, the OER efficiencies at Pt electrodes increased by 69.3%, 21.1% and 14.5% in created water-based acidic, neutral and alkaline electrolyte solutions, respectively. The created water was also effective for OERs in photoelectrochemically catalytic and in inert systems. In addition, the efficiency of OER increased by 47.5% in created water-based alkaline electrolyte solution prepared in situ on a roughened Au electrode. These results suggest that the created water has emerged as an innovative activator in comprehensively effective OERs. PMID:27328821

  6. Superparamagnetic iron oxide nanoparticles as radiosensitizer via enhanced reactive oxygen species formation

    SciTech Connect

    Klein, Stefanie; Sommer, Anja; Distel, Luitpold V.R.; Neuhuber, Winfried; Kryschi, Carola

    2012-08-24

    Highlights: Black-Right-Pointing-Pointer Ultrasmall citrate-coated SPIONs with {gamma}Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} structure were prepared. Black-Right-Pointing-Pointer SPIONs uptaken by MCF-7 cells increase the ROS production for about 240%. Black-Right-Pointing-Pointer The SPION induced ROS production is due to released iron ions and catalytically active surfaces. Black-Right-Pointing-Pointer Released iron ions and SPION surfaces initiate the Fenton and Haber-Weiss reaction. Black-Right-Pointing-Pointer X-ray irradiation of internalized SPIONs leads to an increase of catalytically active surfaces. -- Abstract: Internalization of citrate-coated and uncoated superparamagnetic iron oxide nanoparticles by human breast cancer (MCF-7) cells was verified by transmission electron microscopy imaging. Cytotoxicity studies employing metabolic and trypan blue assays manifested their excellent biocompatibility. The production of reactive oxygen species in iron oxide nanoparticle loaded MCF-7 cells was explained to originate from both, the release of iron ions and their catalytically active surfaces. Both initiate the Fenton and Haber-Weiss reaction. Additional oxidative stress caused by X-ray irradiation of MCF-7 cells was attributed to the increase of catalytically active iron oxide nanoparticle surfaces.

  7. Improvement of islet function in a bioartificial pancreas by enhanced oxygen supply and growth hormone releasing hormone agonist

    PubMed Central

    Ludwig, Barbara; Rotem, Avi; Schmid, Janine; Weir, Gordon C.; Colton, Clark K.; Brendel, Mathias D.; Neufeld, Tova; Block, Norman L.; Yavriyants, Karina; Steffen, Anja; Ludwig, Stefan; Chavakis, Triantafyllos; Reichel, Andreas; Azarov, Dimitri; Zimermann, Baruch; Maimon, Shiri; Balyura, Mariya; Rozenshtein, Tania; Shabtay, Noa; Vardi, Pnina; Bloch, Konstantin; de Vos, Paul; Schally, Andrew V.; Bornstein, Stefan R.; Barkai, Uriel

    2012-01-01

    Islet transplantation is a feasible therapeutic alternative for metabolically labile patients with type 1 diabetes. The primary therapeutic target is stable glycemic control and prevention of complications associated with diabetes by reconstitution of endogenous insulin secretion. However, critical shortage of donor organs, gradual loss in graft function over time, and chronic need for immunosuppression limit the indication for islet transplantation to a small group of patients. Here we present a promising approach to address these limitations by utilization of a macrochamber specially engineered for islet transplantation. The s.c. implantable device allows for controlled and adequate oxygen supply and provides immunological protection of donor islets against the host immune system. The minimally invasive implantable chamber normalized blood glucose in streptozotocin-induced diabetic rodents for up to 3 mo. Sufficient graft function depended on oxygen supply. Pretreatment with the growth hormone-releasing hormone (GHRH) agonist, JI-36, significantly enhanced graft function by improving glucose tolerance and increasing β-cell insulin reserve in rats thereby allowing for a reduction of the islet mass required for metabolic control. As a result of hypervascularization of the tissue surrounding the device, no relevant delay in insulin response to glucose changes has been observed. Consequently, this system opens up a fundamental strategy for therapy of diabetes and may provide a promising avenue for future approaches to xenotransplantation. PMID:22393012

  8. Structurally ordered intermetallic platinum-cobalt core-shell nanoparticles with enhanced activity and stability as oxygen reduction electrocatalysts.

    PubMed

    Wang, Deli; Xin, Huolin L; Hovden, Robert; Wang, Hongsen; Yu, Yingchao; Muller, David A; DiSalvo, Francis J; Abruña, Héctor D

    2013-01-01

    To enhance and optimize nanocatalyst performance and durability for the oxygen reduction reaction in fuel-cell applications, we look beyond Pt-metal disordered alloys and describe a new class of Pt-Co nanocatalysts composed of ordered Pt(3)Co intermetallic cores with a 2-3 atomic-layer-thick platinum shell. These nanocatalysts exhibited over 200% increase in mass activity and over 300% increase in specific activity when compared with the disordered Pt(3)Co alloy nanoparticles as well as Pt/C. So far, this mass activity for the oxygen reduction reaction is the highest among the Pt-Co systems reported in the literature under similar testing conditions. Stability tests showed a minimal loss of activity after 5,000 potential cycles and the ordered core-shell structure was maintained virtually intact, as established by atomic-scale elemental mapping. The high activity and stability are attributed to the Pt-rich shell and the stable intermetallic Pt(3)Co core arrangement. These ordered nanoparticles provide a new direction for catalyst performance optimization for next-generation fuel cells.

  9. A bioinspired approach to protectively decorate platinum-carbon for enhanced activity and durability in oxygen reduction

    NASA Astrophysics Data System (ADS)

    Huang, Yiyin; Fu, Fang; Wu, Peng; Wang, Yaobing; Yao, Jiannian

    2014-12-01

    This work develops a versatile and effective approach of protective decoration to improve the catalytic performance of nanostructured catalysts. The commercial platinum-carbon catalyst is decorated with polydopamine carbide via self-polymerization and pyrolysis processes. The electrocatalytic performance of the novel polydopamine carbide decorated platinum-carbon catalyst is characterized by voltammogram. Origin of improvement in its performance is analyzed by X-ray photoelectron spectroscopy and transmission electron microscope. It is exhibited that the catalytic activity and durability for oxygen reduction reaction and methanol tolerance of the polydopamine carbide decorated platinum-carbon catalyst are enhanced. The promoted effects result from the thermal treatment and decoration of polydopamine carbide which provides N species, slightly alters the Pt electronic structure and prevents Pt from agglomeration during long-term potential cycling.

  10. Combustion mechanism of ultralean rotating counterflow twin premixed flame

    NASA Astrophysics Data System (ADS)

    Uemichi, Akane; Nishioka, Makihito

    2015-01-01

    In our previous numerical studies [Nishioka Makihito, Zhenyu Shen, and Akane Uemichi. "Ultra-lean combustion through the backflow of burned gas in rotating counterflow twin premixed flames." Combustion and Flame 158.11 (2011): 2188-2198. Uemichi Akane, and Makihito Nishioka. "Numerical study on ultra-lean rotating counterflow twin premixed flame of hydrogen-air." Proceedings of the Combustion Institute 34.1 (2013): 1135-1142]. we found that methane- and hydrogen-air rotating counterflow twin flames (RCTF) can achieve ultralean combustion when backward flow of burned gas occurs due to the centrifugal force created by rotation. In this study, we investigated the mechanisms of ultralean combustion in these flames by the detailed numerical analyses of the convective and diffusive transport of the main species. We found that, under ultralean conditions, the diffusive transport of fuel exceeds its backward convective transport in the flame zone, which is located on the burned-gas side of the stagnation point. In contrast, the relative magnitudes of diffusive and convective transport for oxygen are reversed compared to those for the fuel. The resulting flows for fuel and oxygen lead to what we call a 'net flux imbalance'. This net flux imbalance increases the flame temperature and concentrations of active radicals. For hydrogen-air RCTF, a very large diffusivity of hydrogen enhances the net flux imbalance, significantly increasing the flame temperature. This behaviour is intrinsic to a very lean premixed flame in which the reaction zone is located in the backflow of its own burned gas.

  11. Biofuels Combustion

    NASA Astrophysics Data System (ADS)

    Westbrook, Charles K.

    2013-04-01

    This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly.

  12. Biofuels combustion.

    PubMed

    Westbrook, Charles K

    2013-01-01

    This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly.

  13. Biofuels combustion*

    SciTech Connect

    Westbrook, Charles K.

    2013-01-04

    This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. As a result, research efforts on so-called second- and third-generation biofuels are discussed briefly.

  14. Bubble Combustion

    NASA Technical Reports Server (NTRS)

    Corrigan, Jackie

    2004-01-01

    A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM

  15. Biofuels combustion*

    DOE PAGES

    Westbrook, Charles K.

    2013-01-04

    This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acidsmore » and used primarily to replace or supplement conventional diesel fuels. As a result, research efforts on so-called second- and third-generation biofuels are discussed briefly.« less

  16. Enhanced Nitrogen Loss by Eddy-Induced Vertical Transport in the Offshore Peruvian Oxygen Minimum Zone.

    PubMed

    Callbeck, Cameron M; Lavik, Gaute; Stramma, Lothar; Kuypers, Marcel M M; Bristow, Laura A

    2017-01-01

    The eastern tropical South Pacific (ETSP) upwelling region is one of the ocean's largest sinks of fixed nitrogen, which is lost as N2 via the anaerobic processes of anammox and denitrification. One-third of nitrogen loss occurs in productive shelf waters stimulated by organic matter export as a result of eastern boundary upwelling. Offshore, nitrogen loss rates are lower, but due to its sheer size this area accounts for ~70% of ETSP nitrogen loss. How nitrogen loss and primary production are regulated in the offshore ETSP region where coastal upwelling is less influential remains unclear. Mesoscale eddies, ubiquitous in the ETSP region, have been suggested to enhance vertical nutrient transport and thereby regulate primary productivity and hence organic matter export. Here, we investigated the impact of mesoscale eddies on anammox and denitrification activity using 15N-labelled in situ incubation experiments. Anammox was shown to be the dominant nitrogen loss process, but varied across the eddy, whereas denitrification was below detection at all stations. Anammox rates at the eddy periphery were greater than at the center. Similarly, depth-integrated chlorophyll paralleled anammox activity, increasing at the periphery relative to the eddy center; suggestive of enhanced organic matter export along the periphery supporting nitrogen loss. This can be attributed to enhanced vertical nutrient transport caused by an eddy-driven submesoscale mechanism operating at the eddy periphery. In the ETSP region, the widespread distribution of eddies and the large heterogeneity observed in anammox rates from a compilation of stations suggests that eddy-driven vertical nutrient transport may regulate offshore primary production and thereby nitrogen loss.

  17. Enhanced Nitrogen Loss by Eddy-Induced Vertical Transport in the Offshore Peruvian Oxygen Minimum Zone

    PubMed Central

    Callbeck, Cameron M.; Lavik, Gaute; Stramma, Lothar; Kuypers, Marcel M. M.; Bristow, Laura A.

    2017-01-01

    The eastern tropical South Pacific (ETSP) upwelling region is one of the ocean’s largest sinks of fixed nitrogen, which is lost as N2 via the anaerobic processes of anammox and denitrification. One-third of nitrogen loss occurs in productive shelf waters stimulated by organic matter export as a result of eastern boundary upwelling. Offshore, nitrogen loss rates are lower, but due to its sheer size this area accounts for ~70% of ETSP nitrogen loss. How nitrogen loss and primary production are regulated in the offshore ETSP region where coastal upwelling is less influential remains unclear. Mesoscale eddies, ubiquitous in the ETSP region, have been suggested to enhance vertical nutrient transport and thereby regulate primary productivity and hence organic matter export. Here, we investigated the impact of mesoscale eddies on anammox and denitrification activity using 15N-labelled in situ incubation experiments. Anammox was shown to be the dominant nitrogen loss process, but varied across the eddy, whereas denitrification was below detection at all stations. Anammox rates at the eddy periphery were greater than at the center. Similarly, depth-integrated chlorophyll paralleled anammox activity, increasing at the periphery relative to the eddy center; suggestive of enhanced organic matter export along the periphery supporting nitrogen loss. This can be attributed to enhanced vertical nutrient transport caused by an eddy-driven submesoscale mechanism operating at the eddy periphery. In the ETSP region, the widespread distribution of eddies and the large heterogeneity observed in anammox rates from a compilation of stations suggests that eddy-driven vertical nutrient transport may regulate offshore primary production and thereby nitrogen loss. PMID:28122044

  18. 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.

  19. 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 mixtu