Premixed calcium phosphate cements: synthesis, physical properties, and cell cytotoxicity.

PubMed

Xu, Hockin H K; Carey, Lisa E; Simon, Carl G; Takagi, Shozo; Chow, Laurence C

2007-04-01

Calcium phosphate cement (CPC) is a promising material for dental, periodontal, and craniofacial repairs. However, its use requires on-site powder-liquid mixing that increases the surgical placement time and raises concerns of insufficient and inhomogeneous mixing. The objective of this study was to determine a formulation of premixed CPC (PCPC) with rapid setting, high strength, and good in vitro cell viability. PCPCs were formulated from CPC powder+non-aqueous liquid+gelling agent+hardening accelerator. Five PCPCs were thus developed: PCPC-Tartaric, PCPC-Malonic, PCPC-Citric, PCPC-Glycolic, and PCPC-Malic. Formulations and controls were compared for setting time, diametral tensile strength, and osteoblast cell compatibility. Setting time (mean+/-S.D.; n=4) for PCPC-Tartaric was 8.2+/-0.8 min, significantly less than the 61.7+/-1.5 min for the Premixed Control developed previously (p<0.001). On 7th day immersion, the diametral tensile strength of PCPC-Tartaric reached 6.5+/-0.8 MPa, higher than 4.5+/-0.8 MPa of Premixed Control (p=0.036). Osteoblast cells displayed a polygonal morphology and attached to the nano-hydroxyapatite crystals in the PCPCs. All cements had similar live cell density values (p=0.126), indicating that the new PCPCs were as cell compatible as a non-premixed CPC control known to be biocompatible. Each of the new PCPCs had a cell viability that was not significantly different (p>0.1) from that of the non-premixed CPC control. PCPCs will eliminate the powder-liquid mixing during surgery and may also improve the cement performance. The new PCPCs supported cell attachment and yielded a high cell density and viability. Their mechanical strengths approached the reported strengths of sintered porous hydroxyapatite implants and cancellous bone. These nano-crystalline hydroxyapatite cements may be useful in dental, periodontal, and craniofacial repairs.

GAIN Premix Facility: an innovative approach for improving access to quality vitamin and mineral premix in fortification initiatives.

PubMed

Guinot, Philippe; Jallier, Vincent; Blasi, Alessandro; Guyondet, Christophe; Van Ameringen, Marc

2012-12-01

Vitamin and mineral premix is one of the most significant recurring input costs for large-scale food fortification programs. A number of barriers exist to procuring adequate quality premix, including accessing suppliers, volatile prices for premix, lack of quality assurance and monitoring of delivered products, and lack of funds to purchase premix. To develop and test a model to procure premix through a transparent and efficient process in which an adequate level of quality is guaranteed and a financial mechanism is in place to support countries or specific target groups when there are insufficient resources to cover the cost of premix. Efforts focused on premixes used to fortify flour, such as wheat or maize (iron, zinc, B vitamins, and vitamin A), edible oils (vitamins A and D), and other food vehicles, such as fortified complementary foods, complementary food supplements, and condiments. A premix procurement model was set up with three distinct components: a certification process that establishes industry-wide standards and guidelines for premix, a procurement facility that makes premix more accessible to countries and private industry engaged in fortification, and a credit facility mechanism that helps projects finance premix purchases. After three years of operation, 15 premix suppliers and 29 micronutrient manufacturers have been certified, and more than US$23 million worth of premix that met quality standards has been supplied in 34 countries in Africa, Central and Southern Asia, and Eastern Europe, reaching an estimated 242 million consumers. The Premix Facility demonstrated its effectiveness in ensuring access to high-quality premixes, therefore enabling the success of various fortification programs.

Influence of membrane material on the production of colloidal emulsions by premix membrane emulsification.

PubMed

Gehrmann, Sandra; Bunjes, Heike

2018-05-01

Premix membrane emulsification is a possibility to produce colloidal emulsions as carrier systems for poorly water soluble drugs. During the extrusion of a coarse pre-emulsion through a porous membrane, the emulsion droplets are disrupted into smaller droplets. The influence of the membrane material on the emulsification success was investigated in dependence on the emulsifier. Premixed medium chain triglyceride (MCT) emulsions stabilized with five different emulsifiers were extruded through seven different hydrophilic polymeric membrane materials with pore sizes of 200nm. The resulting emulsions differed strongly in particle size and particle size distribution with a range of median particle sizes between 0.08μm and 11μm. The particle size of the emulsions did not depend mainly on the structure or thickness of the membrane but on the combination of emulsifier and membrane material. Contact angle measurements indicated that the wetting of the membrane with the continuous phase of the emulsion was decisive for achieving emulsions with colloidal particle sizes. The type of dispersed phase was of minor importance as basically the same results were obtained with peanut oil instead of MCT. To prove the assumption that only sufficiently hydrophilic membrane materials led to emulsions with colloidal particle sizes, two membrane materials were hydrophilized by plasma treatment. After hydrophilization, the emulsifying process led to emulsions with smaller particle sizes. The use of an alumina membrane (Anodisc®) improved the process even more. With this type of membrane, emulsions with a median particle size below 250nm and a narrow particle size distribution could be obtained with all investigated emulsifiers. Copyright © 2016 Elsevier B.V. All rights reserved.

24. Plutonium Recovery From Contaminated Materials, Architectural Details, Building 232z, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

24. Plutonium Recovery From Contaminated Materials, Architectural Details, Building 232-z, U.S. Atomic Energy Commission, Hanford Atomic Products Operation, General Electric Company, Dwg. No. H-2-23106, 1959. - Plutonium Finishing Plant, Waste Incinerator Facility, 200 West Area, Richland, Benton County, WA

Premixer assembly for mixing air and fuel for combustion

DOEpatents

York, William David; Johnson, Thomas Edward; Keener, Christopher Paul

2016-12-13

A premixer assembly for mixing air and fuel for combustion includes a plurality of tubes disposed at a head end of a combustor assembly. Also included is a tube of the plurality of tubes, the tube including an inlet end and an outlet end. Further included is at least one non-circular portion of the tube extending along a length of the tube, the at least one non-circular portion having a non-circular cross-section, and the tube having a substantially constant cross-sectional area along its length

Stratospheric cruise emission reduction program

NASA Technical Reports Server (NTRS)

Diehl, L. A.; Reck, G. M.; Marek, C. J.; Szaniszlo, A. J.

1977-01-01

A recently implemented NASA effort specifically aimed at reducing cruise oxides of nitrogen from high-altitude aircraft is discussed. The desired emission levels and the combustor technology required to achieve them are discussed. A brief overview of the SCERP operating plan is given. Lean premixed-prevaporized combustion and some of the potential difficulties that are associated with applying this technique to gas turbine combustors are examined. Base technology was developed in several key areas. These fundamental studies are viewed as a requirement for successful implementation of the lean premixed combustion technique.

Flashback resistant pre-mixer assembly

DOEpatents

Laster, Walter R [Oviedo, FL; Gambacorta, Domenico [Oviedo, FL

2012-02-14

A pre-mixer assembly associated with a fuel supply system for mixing of air and fuel upstream from a main combustion zone in a gas turbine engine. The pre-mixer assembly includes a swirler assembly disposed about a fuel injector of the fuel supply system and a pre-mixer transition member. The swirler assembly includes a forward end defining an air inlet and an opposed aft end. The pre-mixer transition member has a forward end affixed to the aft end of the swirler assembly and an opposed aft end defining an outlet of the pre-mixer assembly. The aft end of the pre-mixer transition member is spaced from a base plate such that a gap is formed between the aft end of the pre-mixer transition member and the base plate for permitting a flow of purge air therethrough to increase a velocity of the air/fuel mixture exiting the pre-mixer assembly.

Premixed calcium silicate cement for endodontic applications

PubMed Central

Persson, Cecilia; Engqvist, Håkan

2011-01-01

Calcium silicate-based materials (also called MTA) are increasingly being used in endodontic applications. However, the handling properties of MTA are not optimal when it comes to injectability and cohesion. Premixing the cements using glycerol avoids these issues. However, there is a lack of data on the effect of common cement variables on important properties of premixed cements for endodontic applications. In this study, the effects of liquid-to-powder ratio, amount of radiopacifier and amount of calcium sulfate (added to control the setting time) were screened using a statistical model. In the second part of the study, the liquid-to-powder ratio was optimized for cements containing three different amounts of radiopacifier. Finally, the effect of using glycerol rather than water was evaluated in terms of radiopacity. The setting time was found to increase with the amount of radiopacifier when the liquid-to-powder ratio was fixed. This was likely due to the higher density of the radiopacifier in comparison to the calcium silicate, which gave a higher liquid-to-powder ratio in terms of volume. Using glycerol rather than water to mix the cements led to a decrease in radiopacity of the cement. In conclusion, we were able to produce premixed calcium silicate cements with acceptable properties for use in endodontic applications. PMID:23507729

Premixed calcium silicate cement for endodontic applications: injectability, setting time and radiopacity.

PubMed

Persson, Cecilia; Engqvist, Håkan

2011-01-01

Calcium silicate-based materials (also called MTA) are increasingly being used in endodontic applications. However, the handling properties of MTA are not optimal when it comes to injectability and cohesion. Premixing the cements using glycerol avoids these issues. However, there is a lack of data on the effect of common cement variables on important properties of premixed cements for endodontic applications. In this study, the effects of liquid-to-powder ratio, amount of radiopacifier and amount of calcium sulfate (added to control the setting time) were screened using a statistical model. In the second part of the study, the liquid-to-powder ratio was optimized for cements containing three different amounts of radiopacifier. Finally, the effect of using glycerol rather than water was evaluated in terms of radiopacity. The setting time was found to increase with the amount of radiopacifier when the liquid-to-powder ratio was fixed. This was likely due to the higher density of the radiopacifier in comparison to the calcium silicate, which gave a higher liquid-to-powder ratio in terms of volume. Using glycerol rather than water to mix the cements led to a decrease in radiopacity of the cement. In conclusion, we were able to produce premixed calcium silicate cements with acceptable properties for use in endodontic applications.

A stochastic multi-scale method for turbulent premixed combustion

NASA Astrophysics Data System (ADS)

Cha, Chong M.

2002-11-01

The stochastic chemistry algorithm of Bunker et al. and Gillespie is used to perform the chemical reactions in a transported probability density function (PDF) modeling approach of turbulent combustion. Recently, Kraft & Wagner have demonstrated a 100-fold gain in computational speed (for a 100 species mechanism) using the stochastic approach over the conventional, direct integration method of solving for the chemistry. Here, the stochastic chemistry algorithm is applied to develop a new transported PDF model of turbulent premixed combustion. The methodology relies on representing the relevant spatially dependent physical processes as queuing events. The canonical problem of a one-dimensional premixed flame is used for validation. For the laminar case, molecular diffusion is described by a random walk. For the turbulent case, one of two different material transport submodels can provide the necessary closure: Taylor dispersion or Kerstein's one-dimensional turbulence approach. The former exploits ``eddy diffusivity'' and hence would be much more computationally tractable for practical applications. Various validation studies are performed. Results from the Monte Carlo simulations compare well to asymptotic solutions of laminar premixed flames, both with and without high activation temperatures. The correct scaling of the turbulent burning velocity is predicted in both Damköhler's small- and large-scale turbulence limits. The effect of applying the eddy diffusivity concept in the various regimes is discussed.

Laser-saturated fluorescence of nitric oxide and chemiluminescence measurements in premixed ethanol flames

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

Marques, Carla S.T.; Barreta, Luiz G.; Sbampato, Maria E.

In this study, nitric oxide laser-saturated fluorescence (LSF) measurements were acquired from premixed ethanol flames at atmospheric pressure in a burner. NO-LSF experimental profiles for fuel-rich premixed ethanol flames ({phi} = 1.34 and {phi} = 1.66) were determined through the excitation/detection scheme of the Q{sub 2}(26.5) rotational line in the A{sup 2}{sigma}{sup +} - X{sup 2}{pi} (0,0) vibronic band and {gamma}(0,1) emission band. A calibration procedure by NO doping into the flame was applied to establish the NO concentration profiles in these flames. Chemiluminescent emission measurements in the (0, 0) vibronic emission bands of the OH{sup *} (A{sup 2}{sigma}{sup +}more » - X{sup 2}{pi}) and CH{sup *}(A{sup 2}{delta} - X{sup 2}{pi}) radicals were also obtained with high spatial and spectral resolution for fuel-rich premixed ethanol flames to correlate them with NO concentrations. Experimental chemiluminescence profiles and the ratios of the integrated areas under emission spectra (A{sub CH*}/A{sub CH*}(max.) and A{sub CH*}/A{sub OH*}) were determined. The relationships between chemiluminescence and NO concentrations were established along the premixed ethanol flames. There was a strong connection between CH{sup *} radical chemiluminescence and NO formation and the prompt-NO was identified as the governing mechanism for NO production. The results suggest the optimum ratio of the chemiluminescence of two radicals (A{sub CH*}/A{sub OH*}) for NO diagnostic purposes. (author)« less

Premixed calcium phosphate cements: Synthesis, physical properties, and cell cytotoxicity

PubMed Central

Xu, Hockin H.K.; Carey, Lisa E.; Simon, Carl G.; Takagi, Shozo; Chow, Laurence C.

2009-01-01

Objectives Calcium phosphate cement (CPC) is a promising material for dental, periodontal, and craniofacial repairs. However, its use requires on-site powder–liquid mixing that increases the surgical placement time and raises concerns of insufficient and inhomogeneous mixing. The objective of this study was to determine a formulation of premixed CPC (PCPC) with rapid setting, high strength, and good in vitro cell viability. Methods PCPCs were formulated from CPC powder + non-aqueous liquid + gelling agent + hardening accelerator. Five PCPCs were thus developed: PCPC-Tartaric, PCPC-Malonic, PCPC-Citric, PCPC-Glycolic, and PCPC-Malic. Formulations and controls were compared for setting time, diametral tensile strength, and osteoblast cell compatibility. Results Setting time (mean ± S.D.; n = 4) for PCPC-Tartaric was 8.2 ± 0.8 min, significantly less than the 61.7 ± 1.5 min for the Premixed Control developed previously (p < 0.001). On 7th day immersion, the diametral tensile strength of PCPC-Tartaric reached 6.5 ± 0.8 MPa, higher than 4.5 ± 0.8 MPa of Premixed Control (p = 0.036). Osteoblast cells displayed a polygonal morphology and attached to the nano-hydroxyapatite crystals in the PCPCs. All cements had similar live cell density values (p = 0.126), indicating that the new PCPCs were as cell compatible as a non-premixed CPC control known to be biocompatible. Each of the new PCPCs had a cell viability that was not significantly different (p > 0.1) from that of the non-premixed CPC control. Significance PCPCs will eliminate the powder–liquid mixing during surgery and may also improve the cement performance. The new PCPCs supported cell attachment and yielded a high cell density and viability. Their mechanical strengths approached the reported strengths of sintered porous hydroxyapatite implants and cancellous bone. These nano-crystalline hydroxyapatite cements may be useful in dental, periodontal, and craniofacial repairs. PMID:16678895

Safety, cost, and clinical considerations for the use of premixed parenteral nutrition.

PubMed

Hall, Jacob W

2015-06-01

Premixed parenteral nutrition (PN) can be used for PN therapy in place of traditional compounded or customized PN. Premixed PN may have a number of advantages over compounded PN such as decreased costs, decreased compounding time, reduced chance for error, and reduced incidence of bloodstream infections. However, premixed PN may not be appropriate for all patients and may have other additional costs associated with its use. This article discusses the data available with regard to the use of premixed PN, focusing on the potential advantages and disadvantages of using premixed PN, and also discusses the implementation of premixed PN in a large tertiary cancer center. © 2015 American Society for Parenteral and Enteral Nutrition.

Premixed Turbulent Flame Propagation in Microgravity

NASA Technical Reports Server (NTRS)

Menon, S.; Disseau, M.; Chakravarthy, V. K.; Jagoda, J.

1997-01-01

Papers included address the following topics: (1) Turbulent premixed flame propagation in microgravity; (2) The effect of gravity on turbulent premixed flame propagation - a preliminary cold flow study; and (3) Characteristics of a subgrid model for turbulent premixed combustion.

New evaluation parameter for wearable thermoelectric generators

NASA Astrophysics Data System (ADS)

Wijethunge, Dimuthu; Kim, Woochul

2018-04-01

Wearable devices constitute a key application area for thermoelectric devices. However, owing to new constraints in wearable applications, a few conventional device optimization techniques are not appropriate and material evaluation parameters, such as figure of merit (zT) and power factor (PF), tend to be inadequate. We illustrated the incompleteness of zT and PF by performing simulations and considering different thermoelectric materials. The results indicate a weak correlation between device performance and zT and PF. In this study, we propose a new evaluation parameter, zTwearable, which is better suited for wearable applications compared to conventional zT. Owing to size restrictions, gap filler based device optimization is extremely critical in wearable devices. With respect to the occasions in which gap fillers are used, expressions for power, effective thermal conductivity (keff), and optimum load electrical ratio (mopt) are derived. According to the new parameters, the thermal conductivity of the material has become much more critical now. The proposed new evaluation parameter, namely, zTwearable, is extremely useful in the selection of an appropriate thermoelectric material among various candidates prior to the commencement of the actual design process.

Evaluation of fuel preparation systems for lean premixing-prevaporizing combustors

NASA Technical Reports Server (NTRS)

Dodds, W. J.; Ekstedt, E. E.

1985-01-01

A series of experiments was carried out in order to produce design data for a premixing prevaporizing fuel-air mixture preparation system for aircraft gas turbine engine combustors. The fuel-air mixture uniformity of four different system design concepts was evaluated over a range of conditions representing the cruise operation of a modern commercial turbofan engine. Operating conditions including pressure, temperature, fuel-to-air ratio, and velocity, exhibited no clear effect on mixture uniformity of systems using pressure-atomizing fuel nozzles and large-scale mixing devices. However, the performance of systems using atomizing fuel nozzles and large-scale mixing devices was found to be sensitive to operating conditions. Variations in system design variables were also evaluated and correlated. Mixing uniformity was found to improve with system length, pressure drop, and the number of fuel injection points per unit area. A premixing system capable of providing mixing uniformity to within 15 percent over a typical range of cruise operating conditions is demonstrated.

CO2 Suppression of PMMA Flames In Low-Gravity

NASA Technical Reports Server (NTRS)

Ruff, G. A.; Hicks, M.; Mell, W.; Pettegrew, R.; Malcolm, A.

2003-01-01

Even though much has been learned about the effects of microgravity on material flammability, flame spread, and suppressant effectiveness, uncertainties remain regarding some of the practical aspects of fire protection in spacecraft. The experiments and simulations underway in this project are aimed directly at testing, understanding and improving NASA's existing policies and practices toward fire safety in spacecraft and extraterrestrial habitats. Specifically, the objectives of this research are: 1) Determine systematically the conditions that will ignite onboard flammable materials upon passage of an initial premixed gas, firebrand, or aerosol flame over these materials; 2) Test the effect of firebrands and configuration spacing; and 3) Determine the effectiveness of the flow of CO2 extinguisher or other extinguishing agents. Experimental and computational investigations are planned to achieve each of the three objectives above. Even though progress has been made in all of the areas, the majority of data has been collected for objective (3). Current results from these investigations are discussed.

Encapsulating Reactive Nanoparticles in Carbon Nanotubes Using Flame-Based Synthesis

DTIC Science & Technology

2008-12-22

Results from the Aerosol Catalyst Method using Ferrocene as Precursor Running the experiment using a rich premixed flame seeded with ferrocene allows...flames with ferrocene seeding. There is significant catalyst nanoparticle production, encased within carbon material, namely CNTs. Resonant Raman

Dual-pump CARS temperature and major species concentration measurements in counter-flow methane flames using narrowband pump and broadband Stokes lasers

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

Thariyan, Mathew P.; Ananthanarayanan, Vijaykumar; Bhuiyan, Aizaz H.

2010-07-15

Dual-pump coherent anti-Stokes Raman scattering (CARS) is used to measure temperature and species profiles in representative non-premixed and partially-premixed CH{sub 4}/O{sub 2}/N{sub 2} flames. A new laser system has been developed to generate a tunable single-frequency beam for the second pump beam in the dual-pump N{sub 2}-CO{sub 2} CARS process. The second harmonic output ({proportional_to}532 nm) from an injection-seeded Nd:YAG laser is used as one of the narrowband pump beams. The second single-longitudinal-mode pump beam centered near 561 nm is generated using an injection-seeded optical parametric oscillator, consisting of two non-linear {beta}-BBO crystals, pumped using the third harmonic output ({proportional_to}355more » nm) of the same Nd:YAG laser. A broadband dye laser (BBDL), pumped using the second harmonic output of an unseeded Nd:YAG laser, is employed to produce the Stokes beam centered near 607 nm with full-width-at-half-maximum of {proportional_to}250 cm{sup -1}. The three beams are focused between two opposing nozzles of a counter-flow burner facility to measure temperature and major species concentrations in a variety of CH{sub 4}/O{sub 2}/N{sub 2} non-premixed and partially-premixed flames stabilized at a global strain rate of 20 s{sup -1} at atmospheric-pressure. For the non-premixed flames, excellent agreement is observed between the measured profiles of temperature and CO{sub 2}/N{sub 2} concentration ratios with those calculated using an opposed-flow flame code with detailed chemistry and molecular transport submodels. For partially-premixed flames, with the rich side premixing level beyond the stable premixed flame limit, the calculations overestimate the distance between the premixed and the non-premixed flamefronts. Consequently, the calculated temperatures near the rich, premixed flame are higher than those measured. Accurate prediction of the distance between the premixed and the non-premixed flames provides an interesting challenge for future computations. (author)« less

Large Eddy Simulation of High-Speed, Premixed Ethylene Combustion

NASA Technical Reports Server (NTRS)

Ramesh, Kiran; Edwards, Jack R.; Chelliah, Harsha; Goyne, Christopher; McDaniel, James; Rockwell, Robert; Kirik, Justin; Cutler, Andrew; Danehy, Paul

2015-01-01

A large-eddy simulation / Reynolds-averaged Navier-Stokes (LES/RANS) methodology is used to simulate premixed ethylene-air combustion in a model scramjet designed for dual mode operation and equipped with a cavity for flameholding. A 22-species reduced mechanism for ethylene-air combustion is employed, and the calculations are performed on a mesh containing 93 million cells. Fuel plumes injected at the isolator entrance are processed by the isolator shock train, yielding a premixed fuel-air mixture at an equivalence ratio of 0.42 at the cavity entrance plane. A premixed flame is anchored within the cavity and propagates toward the opposite wall. Near complete combustion of ethylene is obtained. The combustor is highly dynamic, exhibiting a large-scale oscillation in global heat release and mass flow rate with a period of about 2.8 ms. Maximum heat release occurs when the flame front reaches its most downstream extent, as the flame surface area is larger. Minimum heat release is associated with flame propagation toward the cavity and occurs through a reduction in core flow velocity that is correlated with an upstream movement of the shock train. Reasonable agreement between simulation results and available wall pressure, particle image velocimetry, and OH-PLIF data is obtained, but it is not yet clear whether the system-level oscillations seen in the calculations are actually present in the experiment.

Studies of Premixed Laminar and Turbulent Flames at Microgravity

NASA Technical Reports Server (NTRS)

Abid, M.; Aung, K.; Ronney, P. D.; Sharif, J. A.; Wu, M.-S.

1999-01-01

Several topics relating to combustion limits in premixed flames at reduced gravity have been studied. These topics include: (1) flame balls; (2) numerical simulation of flame ball and planar flame structure and stability; (3) experimental simulation of buoyancy effects in premixed flames using aqueous autocatalytic reactions; and (4) premixed flame propagation in Hele-Shaw cells.

The production of premixed flame surface area in turbulent shear flow

NASA Technical Reports Server (NTRS)

Trouve, A.

1993-01-01

In the present work, we use three-dimensional Direct Numerical Simulation (DNS) of premixed flames in turbulent shear flow to characterize the effect of a mean shear motion on flame surface production. The shear is uniform in the unburnt gas, and simulations are performed for different values of the mean shear rate, S. The data base is then used to estimate and compare the different terms appearing in the Sigma-equation as a function of S. The analysis gives in particular the relative weights f the turbulent flow and mean flow components, a(sub T) and A(sub T), of the flame surface production term. This comparison indicates whether the dominant effects of a mean flow velocity gradient on flame surface area are implicit and scale with the modified turbulent flow parameters, kappa and epsilon, or explicit and scale directly with the rate of deformation.

Fully Premixed Low Emission, High Pressure Multi-Fuel Burner

NASA Technical Reports Server (NTRS)

Nguyen, Quang-Viet (Inventor)

2012-01-01

A low-emissions high-pressure multi-fuel burner includes a fuel inlet, for receiving a fuel, an oxidizer inlet, for receiving an oxidizer gas, an injector plate, having a plurality of nozzles that are aligned with premix face of the injector plate, the plurality of nozzles in communication with the fuel and oxidizer inlets and each nozzle providing flow for one of the fuel and the oxidizer gas and an impingement-cooled face, parallel to the premix face of the injector plate and forming a micro-premix chamber between the impingement-cooled face and the in injector face. The fuel and the oxidizer gas are mixed in the micro-premix chamber through impingement-enhanced mixing of flows of the fuel and the oxidizer gas. The burner can be used for low-emissions fuel-lean fully-premixed, or fuel-rich fully-premixed hydrogen-air combustion, or for combustion with other gases such as methane or other hydrocarbons, or even liquid fuels.

Fuel nozzle tube retention

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

Cihlar, David William; Melton, Patrick Benedict

A system for retaining a fuel nozzle premix tube includes a retention plate and a premix tube which extends downstream from an outlet of a premix passage defined along an aft side of a fuel plenum body. The premix tube includes an inlet end and a spring support feature which is disposed proximate to the inlet end. The premix tube extends through the retention plate. The spring retention feature is disposed between an aft side of the fuel plenum and the retention plate. The system further includes a spring which extends between the spring retention feature and the retention plate.

Using HT and DT gamma rays to diagnose mix in Omega capsule implosions

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

Schmitt, M. J.; Herrmann, H. W.; Kim, Y. H.

Experimental evidence [1] indicates that shell material can be driven into the core of Omega capsule implosions on the same time scale as the initial convergent shock. It has been hypothesized that shock-generated temperatures at the fuel/shell interface in thin exploding pusher capsules diffusively drives shell material into the gas core between the time of shock passage and bang time. Here, we propose a method to temporally resolve and observe the evolution of shell material into the capsule core as a function of fuel/shell interface temperature (which can be varied by varying the capsule shell thickness). Our proposed method usesmore » a CD plastic capsule filled with 50/50 HT gas and diagnosed using gas Cherenkov detection (GCD) to temporally resolve both the HT "clean" and DT "mix" gamma ray burn histories. Simulations using Hydra [2] for an Omega CD-lined capsule with a sub-micron layer of the inside surface of the shell pre-mixed into a fraction of the gas region produce gamma reaction history profiles that are sensitive to the depth to which this material is mixed. Furthermore, we observe these differences as a function of capsule shell thickness is proposed to determine if interface mixing is consistent with thermal diffusion λ ii~T 2/Z 2ρ at the gas/shell interface. Finally, since hydrodynamic mixing from shell perturbations, such as the mounting stalk and glue, could complicate these types of capsule-averaged temporal measurements, simulations including their effects also have been performed showing minimal perturbation of the hot spot geometry.« less

Using HT and DT gamma rays to diagnose mix in Omega capsule implosions

DOE PAGES

Schmitt, M. J.; Herrmann, H. W.; Kim, Y. H.; ...

2016-05-26

Experimental evidence [1] indicates that shell material can be driven into the core of Omega capsule implosions on the same time scale as the initial convergent shock. It has been hypothesized that shock-generated temperatures at the fuel/shell interface in thin exploding pusher capsules diffusively drives shell material into the gas core between the time of shock passage and bang time. Here, we propose a method to temporally resolve and observe the evolution of shell material into the capsule core as a function of fuel/shell interface temperature (which can be varied by varying the capsule shell thickness). Our proposed method usesmore » a CD plastic capsule filled with 50/50 HT gas and diagnosed using gas Cherenkov detection (GCD) to temporally resolve both the HT "clean" and DT "mix" gamma ray burn histories. Simulations using Hydra [2] for an Omega CD-lined capsule with a sub-micron layer of the inside surface of the shell pre-mixed into a fraction of the gas region produce gamma reaction history profiles that are sensitive to the depth to which this material is mixed. Furthermore, we observe these differences as a function of capsule shell thickness is proposed to determine if interface mixing is consistent with thermal diffusion λ ii~T 2/Z 2ρ at the gas/shell interface. Finally, since hydrodynamic mixing from shell perturbations, such as the mounting stalk and glue, could complicate these types of capsule-averaged temporal measurements, simulations including their effects also have been performed showing minimal perturbation of the hot spot geometry.« less

Using HT and DT gamma rays to diagnose mix in Omega capsule implosions

NASA Astrophysics Data System (ADS)

Schmitt, M. J.; Herrmann, H. W.; Kim, Y. H.; McEvoy, A. M.; Zylstra, A.; Hammel, B. A.; Sepke, S. M.; Leatherland, A.; Gales, S.

2016-05-01

Experimental evidence [1] indicates that shell material can be driven into the core of Omega capsule implosions on the same time scale as the initial convergent shock. It has been hypothesized that shock-generated temperatures at the fuel/shell interface in thin exploding pusher capsules diffusively drives shell material into the gas core between the time of shock passage and bang time. We propose a method to temporally resolve and observe the evolution of shell material into the capsule core as a function of fuel/shell interface temperature (which can be varied by varying the capsule shell thickness). Our proposed method uses a CD plastic capsule filled with 50/50 HT gas and diagnosed using gas Cherenkov detection (GCD) to temporally resolve both the HT “clean” and DT “mix” gamma ray burn histories. Simulations using Hydra [2] for an Omega CD-lined capsule with a sub-micron layer of the inside surface of the shell pre-mixed into a fraction of the gas region produce gamma reaction history profiles that are sensitive to the depth to which this material is mixed. An experiment to observe these differences as a function of capsule shell thickness is proposed to determine if interface mixing is consistent with thermal diffusion λii∼T2/Z2ρ at the gas/shell interface. Since hydrodynamic mixing from shell perturbations, such as the mounting stalk and glue, could complicate these types of capsule-averaged temporal measurements, simulations including their effects also have been performed showing minimal perturbation of the hot spot geometry.

Study on Combustion Oscillation of Premixed Flame with Pilot Fuel at Elevated Pressures

NASA Astrophysics Data System (ADS)

Ohtsuka, Masaya; Yoshida, Shohei; Hirata, Yoshitaka; Kobayashi, Nariyoshi

Acoustically-coupled combustion oscillation is studied for premixed flame with pilot fuel to be used in gas turbine combustors. Premixed gas is passed through swirl vanes and burnt with the centrally injected pilot fuel. The dependencies of pressure, fuel to air ratio, premixed fuel rate, inlet velocity and air temperature on the combustion oscillation are investigated. Two kinds of oscillation modes of ˜100Hz and ˜350Hz are activated according to inlet velocities. Fluctuating pressures are amplified when the premixed fuel rate is over ˜80% at elevated pressures. The fluctuating pressure peak moves to a higher premixed fuel ratio region with increased pressure or fuel to air ratio for the Helmholz type mode. Combustion oscillation occurs when the pilot fuel velocity is changed proportionally with the flame length.

Multidimensional flamelet-generated manifolds for partially premixed combustion

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

Nguyen, Phuc-Danh; Vervisch, Luc; Subramanian, Vallinayagam

2010-01-15

Flamelet-generated manifolds have been restricted so far to premixed or diffusion flame archetypes, even though the resulting tables have been applied to nonpremixed and partially premixed flame simulations. By using a projection of the full set of mass conservation species balance equations into a restricted subset of the composition space, unsteady multidimensional flamelet governing equations are derived from first principles, under given hypotheses. During the projection, as in usual one-dimensional flamelets, the tangential strain rate of scalar isosurfaces is expressed in the form of the scalar dissipation rates of the control parameters of the multidimensional flamelet-generated manifold (MFM), which ismore » tested in its five-dimensional form for partially premixed combustion, with two composition space directions and three scalar dissipation rates. It is shown that strain-rate-induced effects can hardly be fully neglected in chemistry tabulation of partially premixed combustion, because of fluxes across iso-equivalence-ratio and iso-progress-of-reaction surfaces. This is illustrated by comparing the 5D flamelet-generated manifold with one-dimensional premixed flame and unsteady strained diffusion flame composition space trajectories. The formal links between the asymptotic behavior of MFM and stratified flame, weakly varying partially premixed front, triple-flame, premixed and nonpremixed edge flames are also evidenced. (author)« less

Multiple tube premixing device

DOEpatents

Uhm, Jong Ho; Naidu, Balachandar; Ziminksy, Willy Steve; Kraemer, Gilbert Otto; Yilmaz, Ertan; Lacy, Benjamin; Stevenson, Christian; Felling, David

2013-08-13

The present application provides a premixer for a combustor. The premixer may include a fuel plenum with a number of fuel tubes and a burner tube with a number of air tubes. The fuel tubes extend about the air tubes.

Multiple tube premixing device

DOEpatents

Uhm, Jong Ho; Varatharajan, Balachandar; Ziminsky, Willy Steve; Kraemer, Gilbert Otto; Yilmaz, Ertan; Lacy, Benjamin; Stevenson, Christian; Felling, David

2012-12-11

The present application provides a premixer for a combustor. The premixer may include a fuel plenum with a number of fuel tubes and a burner tube with a number of air tubes. The fuel tubes extend about the air tubes.

The effects of laser absorption on direct-drive capsule experiments at OMEGA

NASA Astrophysics Data System (ADS)

Dodd, E. S.; Benage, J. F.; Kyrala, G. A.; Wilson, D. C.; Wysocki, F. J.; Seka, W.; Glebov, V. Yu.; Stoeckl, C.; Frenje, J. A.

2012-04-01

The yield of an inertial confinement fusion capsule can be greatly affected by the inclusion of high-Z material in the fuel, either intentionally as a diagnostic or from mixing due to hydrodynamic instabilities. To validate calculations of these conditions, glass shell targets filled with a D2 and 3He fuel mixture were fielded in experiments with controlled amounts of pre-mixed Ar, Kr, or Xe. The experiments were fielded at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using 1.0 ns square laser pulses having a total energy 23 kJ and direct drive illumination of shells with an outer diameter of ˜925 μm and a thickness of ˜5 μm. Data were collected and compared to one-dimensional integrated models for yield and burn-temperature measurements. This paper presents a critical examination of the calculational assumptions used in our experimental modeling. A modified treatment of laser-capsule interaction improves the match to the measured scattered laser light and also improves agreement for yields, burn-temperatures, and the fuel compression as measured by the ratio of two yields. Remaining discrepancies between measurement and calculation will also be discussed.

Studies of Premixed Laminar and Turbulent Flames at Microgravity

NASA Technical Reports Server (NTRS)

Kwon, O. C.; Abid, M.; Porres, J.; Liu, J. B.; Ronney, P. D.; Struk, P. M.; Weiland, K. J.

2003-01-01

Several topics relating to premixed flame behavior at reduced gravity have been studied. These topics include: (1) flame balls; (2) flame structure and stability at low Lewis number; (3) experimental simulation of buoyancy effects in premixed flames using aqueous autocatalytic reactions; and (4) premixed flame propagation in Hele-Shaw cells. Because of space limitations, only topic (1) is discussed here, emphasizing results from experiments on the recent STS-107 Space Shuttle mission, along with numerical modeling efforts.

Combustor flame flashback

NASA Technical Reports Server (NTRS)

Proctor, M. P.; Tien, J. S.

1985-01-01

A stainless steel, two-dimensional (rectangular), center-dump, premixed-prevaporized combustor with quartz window sidewalls for visual access was designed, built, and used to study flashback. A parametric study revealed that the flashback equivalence ratio decreased slightly as the inlet air temperature increased. It also indicated that the average premixer velocity and premixer wall temperature were not governing parameters of flashback. The steady-state velocity balance concept as the flashback mechanism was not supported. From visual observation several stages of burning were identified. High speed photography verified upstream flame propagation with the leading edge of the flame front near the premixer wall. Combustion instabilities (spontaneous pressure oscillations) were discovered during combustion at the dump plane and during flashback. The pressure oscillation frequency ranged from 40 to 80 Hz. The peak-to-peak amplitude (up to 1.4 psi) increased as the fuel/air equivalence ratio was increased attaining a maximum value just before flashback. The amplitude suddenly decreased when the flame stabilized in the premixer. The pressure oscillations were large enough to cause a local flow reversal. A simple test using ceramic fiber tufts indicated flow reversals existed at the premixer exit during flickering. It is suspected that flashback occurs through the premixer wall boundary layer flow reversal caused by combustion instability. A theoretical analysis of periodic flow in the premixing channel has been made. The theory supports the flow reversal mechanism.

Search for hidden high-Z materials inside containers with the Muon Portal Project

NASA Astrophysics Data System (ADS)

La Rocca, P.; Antonuccio, V.; Bandieramonte, M.; Becciani, U.; Belluomo, F.; Belluso, M.; Billotta, S.; Blancato, A. A.; Bonanno, D.; Bonanno, G.; Costa, A.; Fallica, G.; Garozzo, S.; Indelicato, V.; Leonora, E.; Longhitano, F.; Longo, S.; Lo Presti, D.; Massimino, P.; Petta, C.; Pistagna, C.; Pugliatti, C.; Puglisi, M.; Randazzo, N.; Riggi, F.; Riggi, S.; Romeo, G.; Russo, G. V.; Santagati, G.; Valvo, G.; Vitello, F.; Zaia, A.; Zappalà, G.

2014-01-01

The Muon Portal is a recently born project that plans to build a large area muon detector for a noninvasive inspection of shipping containers in the ports, searching for the presence of potential fissile (U, Pu) threats. The technique employed by the project is the well-known muon tomography, based on cosmic muon scattering from high-Z materials. The design and operational parameters of the muon portal under construction will be described in this paper, together with preliminary simulation and test results.

Simulation study into the identification of nuclear materials in cargo containers using cosmic rays

NASA Astrophysics Data System (ADS)

Blackwell, T. B.; Kudryavtsev, V. A.

2015-04-01

Muon tomography represents a new type of imaging technique that can be used in detecting high-Z materials. Monte Carlo simulations for muon scattering in different types of target materials are presented. The dependence of the detector capability to identify high-Z targets on spatial resolution has been studied. Muon tracks are reconstructed using a basic point of closest approach (PoCA) algorithm. In this article we report the development of a secondary analysis algorithm that is applied to the reconstructed PoCA points. This algorithm efficiently ascertains clusters of voxels with high average scattering angles to identify `areas of interest' within the inspected volume. Using this approach the effect of other parameters, such as the distance between detectors and the number of detectors per set, on material identification is also presented. Finally, false positive and false negative rates for detecting shielded HEU in realistic scenarios with low-Z clutter are presented.

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

Reigel, M. M.; Fowley, M. D.; Pickenheim, B. R.

A soft metal with low wear resistance (6000 series aluminum), was used to minimize run time while maximizing wear rate. Two paddle configurations were tested, with the first four paddles after the augers replaced by the wear paddles. The first configuration was all flat paddles, with the first paddle not aligned with the augers and is consistent with present SPF mixer. The second configuration had helical paddles for the first three stages after the augers and a flat paddle at the fourth stage. The first helical paddle was aligned with the auger flight for the second configuration. The all flatmore » paddle configuration wear rate was approximately double the wear rate of the helical paddles for the first two sets of paddles after the augers. For both configurations, there was little or no wear on the third and fourth paddle sets based on mass change, indicating that the fully wetted premix materials are much less abrasive than the un-wetted or partially wetted premix. Additionally, inspection of the wear surface of the paddles at higher magnification showed the flat paddles were worn much more than the helical and is consistent with the wear rates. Aligning the auger discharge flight with the first set of helical paddles was effective in reducing the wear rate as compared to the flat paddle configuration. Changing the paddle configuration from flat to helical resulted in a slight increase in rheological properties. Although, both tests produced grout-like material that is within the processing rage of the SPF, it should be noted that cement is not included in the premix and water was used rather than salt solution, which does affect the rheology of the fresh grout. The higher rheological properties from the helical wear test are most likely due to the reduced number of shearing paddles in the mixer. In addition, there is variation in the rheological data for each wear test. This is most likely due to the way that the dry feeds enter the mixer from the dry feeder. The premix is discharged from the hopper in an unsteady fashion, where irregular sized clumps were observed leaving the discharge of the auger, though the auger speed is constant.« less

Use of Piggyback Electrolytes for Patients Receiving Individually Prescribed vs Premixed Parenteral Nutrition.

PubMed

Busch, Rebecca A; Curtis, Caitlin S; Leverson, Glen E; Kudsk, Kenneth A

2015-07-01

Parenteral nutrition (PN) is available as individualized prescriptions frequently prepared with an automated compounding device or as commercially prepared premixed solutions. Our institution exclusively used individualized PN until an amino acid shortage forced a temporary switch to premixed solutions. In general, premixed solutions contain lower electrolyte levels than individualized formulations prescribed for patients with normal organ function. We aimed to quantify supplemental intravenous piggyback (IVPB) electrolyte use in adult patients receiving individualized and premixed PN and to quantify any effect on difference in the cost of therapy. We compared use of supplemental IVPB electrolytes administered to patients receiving PN during consecutive periods prior to and during the amino acid shortage. Electrolyte IVPBs tabulated were potassium chloride, 10 and 20 mEq; magnesium sulfate, 2 g and 4 g; potassium phosphate, 7.5 and 15 mmol; and sodium phosphate, 7.5 and 15 mmol IVPB. There was no statistical difference in the number of PN formulations administered per day during each period (14.7 ± 3.9 vs 14.0 ± 2.6, individualized vs premixed, respectively). Total IVPB electrolytes prescribed per day increased significantly from the individualized PN period to the premixed PN period (7.03 ± 3.8 vs 13.8 ± 6.8; P < .0001). The additional IVPB electrolyte supplementation required in patients receiving premixed PN was associated with an additional $11,855.74 cost per 30 days of therapy compared with those who received individualized PN. Inpatient use of premixed PN results in a significant increase in IVPB electrolyte supplementation and cost compared with individualized PN use. © 2014 American Society for Parenteral and Enteral Nutrition.

Three-Dimensional Direct Numerical Simulation of Methane-Air Turbulent Premixed Flames with Reduced Kinetic Mechanism

NASA Astrophysics Data System (ADS)

Tanahashi, Mamoru; Kikuta, Satoshi; Miyauchi, Toshio

2004-11-01

Three-dimensional DNS of methane-air turbulent premixed flames have been conducted to investigate local extinction mechanism of turbulent premixed flames. A reduced kinetic mechanism (MeCH-19), which is created from GRI-Mech. 2.11 and includes 23 reactive species and 19 step reactions, are used to simulate CH_4-O_2-N2 reaction in turbulence. The effectiveness of this reduced kinetic mechanism has been conformed by preliminary two-dimensional DNS with the reduced kinetic mechanism and two detailed kinetic mechanisms; GRI-Mech. 2.11 and Miller & Bowman. Flame structures of methane-air turbulent premixed flames are compared with those of hydrogen-air turbulent premixed flames which have been obtained by 3D-DNS with a detailed kinetic mechanism in our previous study. Local extinctions occur in methane-air turbulent premixed flames, whereas no extinction is observed for hydrogen-air flames in nearly same turbulence condition. The local extinction mechanism is discussed based on eddy/flame interaction in small scales.

Versatile Vials

NASA Technical Reports Server (NTRS)

2001-01-01

Advanced Fuel Research, Inc. (AFR) developed a new sol-gel material coating for sample vials to be used in surface-enhanced Raman (SER) spectroscopy. In the fields of biomedical and forensic science, the coated vials are used to identify physiological chemicals present in blood and urine. The vials are used in the pharmaceutical industry in the area of drug development and discovery. In the drug enforcement field, using the vials helps with detection of trace amounts of drugs on surfaces. The SER vials will also help to identify contaminants in water sources, such as various inorganics and pesticides. The new vials have advantages over other SER materials. Former products required that samples be pre-mixed or dissolved into specific solvents or reagents. The SER vials do not have these limitations, and measurements can be performed using any solvent. Furthermore, the signal appears in less than one second. The sol-gel material will stay active for at least one year and the vials are compatible with any Raman spectrometer. Most importantly, the SER activity can be duplicated from vial-to-vial, allowing for reproducible results.

Results Outbrief from the 2014 CombustionLab Workshop

NASA Technical Reports Server (NTRS)

Urban, David

2015-01-01

On October 24-25, 2014, NASA Headquarters and the NASA Glenn Research Center sponsored the CombustionLab Workshop in Pasadena, CA as part of the 30th Annual Meeting of the American Society for Gravitational and Space Research. The two-day event brought together scientists and engineers from academia, industry, other government agencies, and international space agencies. The goal of the workshop was to identify key engineering drivers and research priorities, and to provide overall recommendations for the development of the next generation of combustion science experiments for the International Space Station (ISS). The workshop was divided in to 6 topical areas: Droplets, Sprays and Aerosols; Non-Premixed Flames; Premixed Flames; High Pressure and Supercritical Reacting Systems; Fire Safety; Heterogeneous Reaction Processes. Each of these areas produced summary findings which were assembled into a report and were integrated into the NASA budget planning process. The summary results of this process are presented with implementation plans and options for the future.

Fuel injection nozzle and method of manufacturing the same

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

Monaghan, James Christopher; Johnson, Thomas Edward; Ostebee, Heath Michael

A fuel injection head for use in a fuel injection nozzle comprises a monolithic body portion comprising an upstream face, an opposite downstream face, and a peripheral wall extending therebetween. A plurality of pre-mix tubes are integrally formed with and extend axially through the body portion. Each of the pre-mix tubes comprises an inlet adjacent the upstream face, an outlet adjacent the downstream face, and a channel extending between the inlet and the outlet. Each pre-mix tube also includes at least one fuel injector that at least partially extends outward from an exterior surface of the pre-mix tube, wherein themore » fuel injector is integrally formed with the pre-mix tube and is configured to facilitate fuel flow between the body portion and the channel.« less

Effects of percentage of blockage and flameholder downstream counterbores on lean combustion limits of premixed, prevaporized propane-air mixture

NASA Technical Reports Server (NTRS)

Fernandez, M. A. B.

1983-01-01

Lean combustion limits were determined for a premixed prevaporized propane air mixture with flat plate flame stabilizers. Experiments were conducted in a constant area flame tube combustor utilizing flameholders of varying percentages of blockage and downstream counterbores. Combustor inlet air velocity at ambient conditions was varied from 4 to 9 meters per second. Flameholders with a center hole and four half holes surrounding it were tested with 63, 73, and 85 percent blockage and counterbore diameters of 112 and 125 percent of the thru hole diameter, in addition to the no counterbore configuration. Improved stability was obtained by using counterbore flameholders and higher percentages of blockage. Increases in mixture velocity caused the equivalence ratio at blowout to increase in all cases.

Gas turbine premixer with internal cooling

DOEpatents

York, William David; Johnson, Thomas Edward; Lacy, Benjamin Paul; Stevenson, Christian Xavier

2012-12-18

A system that includes a turbine fuel nozzle comprising an air-fuel premixer. The air-fuel premixed includes a swirl vane configured to swirl fuel and air in a downstream direction, wherein the swirl vane comprises an internal coolant path from a downstream end portion in an upstream direction through a substantial length of the swirl vane.

21 CFR 170.60 - Nitrites and/or nitrates in curing premixes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Nitrites and/or nitrates in curing premixes. 170... and Decisions § 170.60 Nitrites and/or nitrates in curing premixes. (a) Nitrites and/or nitrates are.... (b) Nitrites and/or nitrates, when packaged separately from flavoring and seasoning in curing...

21 CFR 170.60 - Nitrites and/or nitrates in curing premixes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Nitrites and/or nitrates in curing premixes. 170... and Decisions § 170.60 Nitrites and/or nitrates in curing premixes. (a) Nitrites and/or nitrates are.... (b) Nitrites and/or nitrates, when packaged separately from flavoring and seasoning in curing...

21 CFR 170.60 - Nitrites and/or nitrates in curing premixes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Nitrites and/or nitrates in curing premixes. 170... and Decisions § 170.60 Nitrites and/or nitrates in curing premixes. (a) Nitrites and/or nitrates are.... (b) Nitrites and/or nitrates, when packaged separately from flavoring and seasoning in curing...

Methods and systems for combustion dynamics reduction

DOEpatents

Kraemer, Gilbert Otto [Greer, SC; Varatharajan, Balachandar [Cincinnati, OH; Srinivasan, Shiva [Greer, SC; Lynch, John Joseph [Wilmington, NC; Yilmaz, Ertan [Albany, NY; Kim, Kwanwoo [Greer, SC; Lacy, Benjamin [Greer, SC; Crothers, Sarah [Greenville, SC; Singh, Kapil Kumar [Rexford, NY

2009-08-25

Methods and systems for combustion dynamics reduction are provided. A combustion chamber may include a first premixer and a second premixer. Each premixer may include at least one fuel injector, at least one air inlet duct, and at least one vane pack for at least partially mixing the air from the air inlet duct or ducts and fuel from the fuel injector or injectors. Each vane pack may include a plurality of fuel orifices through which at least a portion of the fuel and at least a portion of the air may pass. The vane pack or packs of the first premixer may be positioned at a first axial position and the vane pack or packs of the second premixer may be positioned at a second axial position axially staggered with respect to the first axial position.

Evaluation of an unsteady flamelet progress variable model for autoignition and flame development in compositionally stratified mixtures

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Saumyadip; Abraham, John

2012-07-01

The unsteady flamelet progress variable (UFPV) model has been proposed by Pitsch and Ihme ["An unsteady/flamelet progress variable method for LES of nonpremixed turbulent combustion," AIAA Paper No. 2005-557, 2005] for modeling the averaged/filtered chemistry source terms in Reynolds averaged simulations and large eddy simulations of reacting non-premixed combustion. In the UFPV model, a look-up table of source terms is generated as a function of mixture fraction Z, scalar dissipation rate χ, and progress variable C by solving the unsteady flamelet equations. The assumption is that the unsteady flamelet represents the evolution of the reacting mixing layer in the non-premixed flame. We assess the accuracy of the model in predicting autoignition and flame development in compositionally stratified n-heptane/air mixtures using direct numerical simulations (DNS). The focus in this work is primarily on the assessment of accuracy of the probability density functions (PDFs) employed for obtaining averaged source terms. The performance of commonly employed presumed functions, such as the dirac-delta distribution function, the β distribution function, and statistically most likely distribution (SMLD) approach in approximating the shapes of the PDFs of the reactive and the conserved scalars is evaluated. For unimodal distributions, it is observed that functions that need two-moment information, e.g., the β distribution function and the SMLD approach with two-moment closure, are able to reasonably approximate the actual PDF. As the distribution becomes multimodal, higher moment information is required. Differences are observed between the ignition trends obtained from DNS and those predicted by the look-up table, especially for smaller gradients where the flamelet assumption becomes less applicable. The formulation assumes that the shape of the χ(Z) profile can be modeled by an error function which remains unchanged in the presence of heat release. We show that this assumption is not accurate.

Lean, premixed, prevaporized combustion for aircraft gas turbine engines

NASA Technical Reports Server (NTRS)

Mularz, E. J.

1979-01-01

The application of lean, premixed, prevaporized combustion to aircraft turbine engine systems can result in benefits in terms of superior combustion performance, improved combustor and turbine durability, and environmentally acceptable pollutant emissions. Lean, premixed prevaporized combustion is particularly attractive for reducing the oxides of nitrogen emissions during high altitude cruise. The NASA stratospheric cruise emission reduction program will evolve and demonstrate lean, premixed, prevaporized combustion technology for aircraft engines. This multiphased program is described. In addition, the various elements of the fundamental studies phase of the program are reviewed, and results to date of many of these studies are summarized.

25. Plutonium Recovery From Contaminated Materials, Architectural Plans & Details, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

25. Plutonium Recovery From Contaminated Materials, Architectural Plans & Details, Building 232-Z, U.S. Atomic Energy Commission, Hanford Atomic Products Operation, General Electric Company, Dwg. No. H-2-23105, 1959. - Plutonium Finishing Plant, Waste Incinerator Facility, 200 West Area, Richland, Benton County, WA

26. Plutonium Recovery From Contaminated Materials, Architectural Elevations, Sections & ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

26. Plutonium Recovery From Contaminated Materials, Architectural Elevations, Sections & Dets., Building 232-Z, U.S. Atomic Energy Commission, Hanford Atomic Products Operation, General Electric Company, Dwg. No. H-2-23106, 1959. - Plutonium Finishing Plant, Waste Incinerator Facility, 200 West Area, Richland, Benton County, WA

The Effect of Premixed Al-Cu Powder on the Stir Zone in Friction Stir Welding of AA3003-H18

NASA Astrophysics Data System (ADS)

Abnar, B.; Kazeminezhad, M.; Kokabi, A. H.

2015-02-01

In this research, 3-mm-thick AA3003-H18 non-heat-treatable aluminum alloy plates were joined by friction stir welding (FSW). It was performed by adding pure Cu and premixed Cu-Al powders at various rotational speeds of 800, 1000, and 1200 rpm and constant traveling speeds of 100 mm/min. At first, the powder was filled into the gap (0.2 or 0.4 mm) between two aluminum alloy plates, and then the FSW process was performed in two passes. The microstructure, mechanical properties, and formation of intermetallic compounds were investigated in both cases of using pure Cu and premixed Al-Cu powders. The results of using pure Cu and premixed Al-Cu powders were compared in the stir zone at various rotational speeds. The copper particle distribution and formation of Al-Cu intermetallic compounds (Al2Cu and AlCu) in the stir zone were desirable using premixed Al-Cu powder into the gap. The hardness values were significantly increased by formation of Al-Cu intermetallic compounds in the stir zone and it was uniform throughout the stir zone when premixed Al-Cu powder was used. Also, longitudinal tensile strength from the stir zone was higher when premixed Al-Cu powder was used instead of pure Cu powder.

21 CFR 558.311 - Lasalocid.

Code of Federal Regulations, 2010 CFR

2010-04-01

... mineral premix1 0.5 Vitamin premix1 0.2 Lasalocid Type A medicated article (90.7 g/lb)2 0.083 1 Content of... medicated article (68 g/lb)2 0.80 1 Content of the vitamin and trace mineral premixes may be varied; however... derived from lasalocid A. (b) Approvals. Type A medicated articles approved for sponsors identified in...

LIF measurements and chemical kinetic analysis of methylidyne formation in high-pressure counter-flow partially premixed and non-premixed flames

NASA Astrophysics Data System (ADS)

Naik, S. V.; Laurendeau, N. M.

2004-11-01

We report quantitative, spatially resolved, linear laser-induced fluorescence (LIF) measurements of methylidyne concentration ([CH]) in laminar, methane air, counter-flow partially premixed and non-premixed flames using excitation near 431.5 nm in the A X (0,0) band. For partially premixed flames, fuel-side equivalence ratios (ϕB) of 1.45, 1.6 and 2.0 are studied at pressures of 1, 3, 6, 9 and 12 atm. For non-premixed flames, the fuel-side mixture consists of 25% CH4 and 75% N2; measurements are obtained at pressures of 1, 2, 3, 4, 5, 6, 9 and 12 atm. The quantitative CH measurements are compared with predictions from an opposed-flow flame code utilizing two GRI chemical kinetic mechanisms (versions 2.11 and 3.0). LIF measurements of [CH] are corrected for variations in the quenching rate coefficient by using major species concentrations and temperatures generated by the code along with suitable quenching cross sections for CH available from the literature. A pathway analysis provides relative contributions from important elementary reactions to the total amount of CH produced at various pressures. Key reactions controlling peak CH concentrations are also identified by using a sensitivity analysis. For the partially premixed flames, measured CH profiles are reproduced reasonably well by GRI 3.0, although some quantitative disagreement exists at all pressures. Two CH radical peaks are observed for ϕB=1.45 and ϕB=1.6 at pressures above 3 atm. Peak CH concentrations for the non-premixed flames are significantly underpredicted by GRI 3.0. The latter agrees with previously reported NO concentrations, which are also underpredicted in these same high-pressure counter-flow diffusion flames.

Comparison Between Premixed and Compounded Parenteral Nutrition Solutions in Hospitalized Patients Requiring Parenteral Nutrition.

PubMed

Beattie, Colleen; Allard, Johane; Raman, Maitreyi

2016-04-01

Parenteral nutrition (PN) may be provided through compounded or premixed solutions. To determine the proportion of stable custom-compounded PN prescriptions that would fit within a 20% deviance of an existing premixed PN solution. A retrospective study design was used. Inpatients who received PN in non-critical care units in the preceding year were screened for eligibility. Results are reported descriptively as means (95% confidence intervals) and proportions. We reviewed 97 PN prescriptions that met inclusion criteria. Stable hospital PN prescriptions compared with the reference premixed prescription provided 1838 (1777-1898) vs 1843 (1781-1905) kcal/d, P = .43; dextrose, 266 (254-277) vs 225 (216-234) g/d, P < .001; amino acids, 100 (95.9-104) vs 95.2 (91.7-98.7) g/d, P < .001; and lipids, 53.2 (51.3-55.1) vs 76.5 (73.8-79.2) g/d, P < .001. Fifty-eight of 97 (59.8%) matched for 2 of 3 macronutrients. Hospital compared with premixed lipid was lower 53.6 (43-64.2) g/d vs 75.5 (60.5-90.5) g/d, P < .001. Electrolytes differed between hospital and premixed solutions: sodium, 98.6 (95.0-102) vs 66.9 (64.6-69.9) mmol/L, P < .001; potassium, 93.7 (89.0-98.3) vs 57.4 (55.4-59.4) mmol/L, P < .001; and magnesium, 5.4 (4.8-5.4) vs 7.6 (7.4-7.9) mmol/L. Calories and protein were remarkably similar, but dextrose, lipid, and electrolytes differed between hospital PN and the reference premixed prescription. We believe that there may be a role for premixed solutions in quaternary centers in stable non-critically ill patients. © 2016 American Society for Parenteral and Enteral Nutrition.

Linac based photofission inspection system employing novel detection concepts

NASA Astrophysics Data System (ADS)

Stevenson, John; Gozani, Tsahi; Elsalim, Mashal; Condron, Cathie; Brown, Craig

2011-10-01

Rapiscan Systems is developing a LINAC based cargo inspection system for detection of special nuclear material (SNM) in cargo containers. The system, called Photofission Based Alarm Resolution (PBAR) is being developed under a DHD/DNDO Advanced Technology Demonstration (ATD) program. The PBAR system is based on the Rapiscan Eagle P9000 X-ray system, which is a portal system with a commercial 9 MeV LINAC X-ray source. For the purposes of the DNDO ATD program, a conveyor system was installed in the portal to allow scanning and precise positioning of 20 ft ISO cargo containers. The system uses a two step inspection process. In the first step, the basic scan, the container is quickly and completely inspected using two independent radiography arrays: the conventional primary array with high spatial resolution and a lower resolution spectroscopic array employing the novel Z-Spec method. The primary array uses cadmium tungstate (CdWO 4) detectors with conventional current mode readouts using photodiodes. The Z-Spec array uses small plastic scintillators capable of performing very fast (up to 10 8 cps) gamma-ray spectroscopy. The two radiography arrays are used to locate high-Z objects in the image such as lead, tungsten, uranium, which could be potential shielding materials as well as SNM itself. In the current system, the Z-Spec works by measuring the energy spectrum of transmitted X-rays. For high-Z materials the higher end of the energy spectrum is more attenuated than for low-Z materials and thus has a lower mean energy and a narrower width than low- and medium-Z materials. The second step in the inspection process is the direct scan or alarm clearing scan. In this step, areas of the container image, which were identified as high Z, are re-inspected. This is done by precisely repositioning the container to the location of the high-Z object and performing a stationary irradiation of the area with X-ray beam. Since there are a large number of photons in the 9 MV Bremsstrahlung spectrum above the photofission "threshold" of about 6 MeV, the X-ray beam induces numerous fissions if nuclear material is present. The PBAR system looks for the two most prolific fission signatures to confirm the presence of special nuclear materials (SNM). These are prompt neutrons and delayed gamma rays. The PBAR system uses arrays of two types of fast and highly efficient gamma ray detectors: plastic and fluorocarbon scintillators. The latter serves as a detector of fission prompt neutrons using the novel threshold activation detector (TAD) concept as well as a very efficient delayed gamma ray detector. The major advantage of TAD for detecting the prompt neutrons is its insensitivity to the intense source related backgrounds. The current status of the system and experimental results will be shown and discussed.

An Investigation of a Hybrid Mixing Model for PDF Simulations of Turbulent Premixed Flames

NASA Astrophysics Data System (ADS)

Zhou, Hua; Li, Shan; Wang, Hu; Ren, Zhuyin

2015-11-01

Predictive simulations of turbulent premixed flames over a wide range of Damköhler numbers in the framework of Probability Density Function (PDF) method still remain challenging due to the deficiency in current micro-mixing models. In this work, a hybrid micro-mixing model, valid in both the flamelet regime and broken reaction zone regime, is proposed. A priori testing of this model is first performed by examining the conditional scalar dissipation rate and conditional scalar diffusion in a 3-D direct numerical simulation dataset of a temporally evolving turbulent slot jet flame of lean premixed H2-air in the thin reaction zone regime. Then, this new model is applied to PDF simulations of the Piloted Premixed Jet Burner (PPJB) flames, which are a set of highly shear turbulent premixed flames and feature strong turbulence-chemistry interaction at high Reynolds and Karlovitz numbers. Supported by NSFC 51476087 and NSFC 91441202.

Gas turbine engine combustor can with trapped vortex cavity

DOEpatents

Burrus, David Louis; Joshi, Narendra Digamber; Haynes, Joel Meier; Feitelberg, Alan S.

2005-10-04

A gas turbine engine combustor can downstream of a pre-mixer has a pre-mixer flowpath therein and circumferentially spaced apart swirling vanes disposed across the pre-mixer flowpath. A primary fuel injector is positioned for injecting fuel into the pre-mixer flowpath. A combustion chamber surrounded by an annular combustor liner disposed in supply flow communication with the pre-mixer. An annular trapped dual vortex cavity located at an upstream end of the combustor liner is defined between an annular aft wall, an annular forward wall, and a circular radially outer wall formed therebetween. A cavity opening at a radially inner end of the cavity is spaced apart from the radially outer wall. Air injection first holes are disposed through the forward wall and air injection second holes are disposed through the aft wall. Fuel injection holes are disposed through at least one of the forward and aft walls.

Combustion diagnostic for active engine feedback control

DOEpatents

Green, Jr., Johney Boyd; Daw, Charles Stuart; Wagner, Robert Milton

2007-10-02

This invention detects the crank angle location where combustion switches from premixed to diffusion, referred to as the transition index, and uses that location to define integration limits that measure the portions of heat released during the combustion process that occur during the premixed and diffusion phases. Those integrated premixed and diffusion values are used to develop a metric referred to as the combustion index. The combustion index is defined as the integrated diffusion contribution divided by the integrated premixed contribution. As the EGR rate is increased enough to enter the low temperature combustion regime, PM emissions decrease because more of the combustion process is occurring over the premixed portion of the heat release rate profile and the diffusion portion has been significantly reduced. This information is used to detect when the engine is or is not operating in a low temperature combustion mode and provides that feedback to an engine control algorithm.

Innovative scheme for high-repetition-rate imaging of CN radical.

PubMed

Satija, Aman; Ruesch, Morgan D; Powell, Michael S; Son, Steven F; Lucht, Robert P

2018-02-01

We have employed, to the best of our knowledge, a novel excitation scheme to perform the first high-repetition-rate planar laser-induced fluorescence (PLIF) measurements of a CN radical in combustion. The third harmonic of a Nd:YVO 4 laser at 355 nm due to its relatively large linewidth overlaps with several R branch transitions in a CN ground electronic state. Therefore, the 355 nm beam was employed to directly excite the CN transitions with good efficiency. The CN measurements were performed in premixed CH 4 -N 2 O flames with varying equivalence ratios. A detailed characterization of the high-speed CN PLIF imaging system is presented via its ability to capture statistical and dynamical information in these premixed flames. Single-shot CN PLIF images obtained over a HMX pellet undergoing self-supported deflagration are presented as an example of the imaging system being applied towards characterizing the flame structure of energetic materials.

[Ulcerative contact dermitis caused by premixed concrete (cement burns)].

PubMed

Ancona Alayón; Aranda Martínez, J G

1978-01-01

Cement dermatitis manifests clinically as a chronic dermatitis of irritative character, due to its alkaline nature and as allergic contact dermatitis produced by sensitization to chromium and cobalt occurring as trace elements. the present report deals with a mason without previous dermatitis, presenting bullae, ulcers and necrosis in lower limbs, short time after incidental contact at work, with premixed concrete. The clinical manifestations, such as short evolution, clear limitation to sites in close contact with concrete, negativity to standard patch testing and good prognosis with early treatment, are mentioned. The acute irritant nature of the disease is clear, in opposition to the classical manifestations of cement dermatitis. The need of studies of the chemical properties of this material including pH, alkalinity and the possible roll of additives employed, is part of the strategy for prevention of occupational dermatitis in the building trade, which should include also, information of hazards and proper training in their trade.

Gas turbine premixing systems

DOEpatents

Kraemer, Gilbert Otto; Varatharajan, Balachandar; Evulet, Andrei Tristan; Yilmaz, Ertan; Lacy, Benjamin Paul

2013-12-31

Methods and systems are provided for premixing combustion fuel and air within gas turbines. In one embodiment, a combustor includes an upstream mixing panel configured to direct compressed air and combustion fuel through premixing zone to form a fuel-air mixture. The combustor includes a downstream mixing panel configured to mix additional combustion fuel with the fule-air mixture to form a combustion mixture.

Lean premixed/prevaporized combustion

NASA Technical Reports Server (NTRS)

Lefebvre, A. H. (Editor)

1977-01-01

Recommendations were formulated on the status and application of lean premixed/prevaporized combustion to the aircraft gas turbine for the reduction of pollutant emissions. The approach taken by the NASA Stratospheric Cruise Emission Reduction Program (SCERP) in pursuing the lean premixed/prevaporized combustion technique was also discussed. The proceedings contains an overview of the SCERP program, the discussions and recommendations of the participants, and an overall summary.

Dry low NOx combustion system with pre-mixed direct-injection secondary fuel nozzle

DOEpatents

Zuo, Baifang; Johnson, Thomas; Ziminsky, Willy; Khan, Abdul

2013-12-17

A combustion system includes a first combustion chamber and a second combustion chamber. The second combustion chamber is positioned downstream of the first combustion chamber. The combustion system also includes a pre-mixed, direct-injection secondary fuel nozzle. The pre-mixed, direct-injection secondary fuel nozzle extends through the first combustion chamber into the second combustion chamber.

Decision analysis applied to the purchase of frozen premixed intravenous admixtures.

PubMed

Witte, K W; Eck, T A; Vogel, D P

1985-04-01

A structured decision-analysis model was used to evaluate frozen premixed cefazolin admixtures. Decision analysis is a process of stating the desired outcome, establishing and weighting evaluation criteria, identifying options for reaching the outcome, evaluating and numerically ranking each option for each criterion, multiplying the ranking by the weight for each criterion, and calculating total points for each option. It was used to compare objectively frozen premixed cefazolin admixtures with batch reconstitution from vials and reconstitution of lyophilized, ready-to-mix containers. In this institution the model numerically demonstrated a distinct preference for the premixed frozen admixture over these other alternatives. A comparison of these results with the total cost impact of each option resulted in a decision to purchase the frozen premixed solution. The advantages of the frozen premixed solution that contributed most to this decision were decreased waste and personnel time. The latter was especially important since it allowed for the reallocation of personnel resources to other potentially cost-reducing clinical functions. Decision analysis proved to be an effective tool for formalizing the process of selecting among various alternatives to reach a desired outcome in this hospital pharmacy.

Measurements and Modeling of Nitric Oxide Formation in Counterflow, Premixed CH4/O2/N2 Flames

NASA Technical Reports Server (NTRS)

Thomsen, D. Douglas; Laurendeau, Normand M.

2000-01-01

Laser-induced fluorescence (LIF) measurements of NO concentration in a variety of CH4/O2/N2 flames are used to evaluate the chemical kinetics of NO formation. The analysis begins with previous measurements in flat, laminar, premixed CH4/O2/N2 flames stabilized on a water-cooled McKenna burner at pressures ranging from 1 to 14.6 atm, equivalence ratios from 0.5 to 1.6, and volumetric nitrogen/oxygen dilution ratios of 2.2, 3.1 and 3.76. These measured results are compared to predictions to determine the capabilities and limitations of the comprehensive kinetic mechanism developed by the Gas Research Institute (GRI), version 2.11. The model is shown to predict well the qualitative trends of NO formation in lean-premixed flames, while quantitatively underpredicting NO concentration by 30-50%. For rich flames, the model is unable to even qualitatively match the experimental results. These flames were found to be limited by low temperatures and an inability to separate the flame from the burner surface. In response to these limitations, a counterflow burner was designed for use in opposed premixed flame studies. A new LIF calibration technique was developed and applied to obtain quantitative measurements of NO concentration in laminar, counterflow premixed, CH4/O2/N2 flames at pressures ranging from 1 to 5.1 atm, equivalence ratios of 0.6 to 1.5, and an N2/O2 dilution ratio of 3.76. The counterflow premixed flame measurements are combined with measurements in burner-stabilized premixed flames and counterflow diffusion flames to build a comprehensive database for analysis of the GRI kinetic mechanism. Pathways, quantitative reaction path and sensitivity analyses are applied to the GRI mechanism for these flame conditions. The prompt NO mechanism is found to severely underpredict the amount of NO formed in rich premixed and nitrogen-diluted diffusion flames. This underprediction is traced to uncertainties in the CH kinetics as well as in the nitrogen oxidation chemistry. Suggestions are made which significantly improve the predictive capability of the GRI mechanism in near-stoichiometric, rich, premixed flames and in atmospheric-pressure, diffusion flames. However, the modified reaction mechanism is unable to model the formation of NO in ultra-rich, premixed or in high-pressure, nonpremixed flames, thus indicating the need for additional study under these conditions.

Studies of Premixed Laminar and Turbulent Flames at Microgravity

NASA Technical Reports Server (NTRS)

Ronney, Paul D.

1993-01-01

The work of the Principal Investigator (PI) has encompassed four topics related to the experimental and theoretical study of combustion limits in premixed flames at microgravity, as discussed in the following sections. These topics include: (1) radiation effects on premixed gas flames; (2) flame structure and stability at low Lewis number; (3) flame propagation and extinction is cylindrical tubes; and (4) experimental simulation of combustion processes using autocatalytic chemical reactions.

Dry low combustion system with means for eliminating combustion noise

DOEpatents

Verdouw, Albert J.; Smith, Duane; McCormick, Keith; Razdan, Mohan K.

2004-02-17

A combustion system including a plurality of axially staged tubular premixers to control emissions and minimize combustion noise. The combustion system includes a radial inflow premixer that delivers the combustion mixture across a contoured dome into the combustion chamber. The axially staged premixers having a twist mixing apparatus to rotate the fluid flow and cause improved mixing without causing flow recirculation that could lead to pre-ignition or flashback.

LEM-CF Premixed Tool Kit

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

2015-01-19

The purpose of LEM-CF Premixed Tool Kit is to process premixed flame simulation data from the LEM-CF solver (https://fileshare.craft-tech.com/clusters/view/lem-cf) into a large-eddy simulation (LES) subgrid model database. These databases may be used with a user-defined-function (UDF) that is included in the Tool Kit. The subgrid model UDF may be used with the ANSYS FLUENT flow solver or other commercial flow solvers.

Design of a Premixed Gaseous Rocket Engine Injector for Ethylene and Oxygen

DTIC Science & Technology

2006-12-01

and uniform combustion zone. An engine will benefit by having a greater characteristic exhaust velocity efficiency (ηc*), less soot production and...the challenges of designing a premixed injector. The design requirements for the engine are to provide a wide range of combustion pressure... Engineering Original Premixed Injector1 Downstream of the three inch combustion chamber a bolt-on conical nozzle was attached. This nozzle had a

Design and evaluation of a low nitrogen oxides natural gas-fired conical wire-mesh duct burner for a micro-cogeneration unit

NASA Astrophysics Data System (ADS)

Ramadan, Omar Barka Ab

A novel low NOx conical wire-mesh duct burner was designed, built and tested in the present research. This thesis documents the design process and the in-depth evaluation of this novel duct burner for the development of a more efficient micro-cogeneration unit. This duct burner provides the thermal energy necessary to raise the microturbine exhaust gases temperature to increase the heat recovery capability. The duct burner implements both lean-premixed and surface combustion techniques to achieve low NOx and CO emissions. The design of the duct burner was supported by a qualitative flow visualization study for the duct burner premixer to provide insight into the premixer flow field (mixing process). Different premixer geometries were used to control the homogeneity of the fuel-oxidant mixture at the exit of the duct burner premixer. Laser sheet illumination (LSI) technique was used to capture images of the mixing process, for each configuration studied. A quasi-quantitative analysis technique was developed to rank the different premixer geometries in terms of mixing effectiveness. The premixer geometries that provided better mixing were selected and used for the combustion tests. The full-scale gas-fired duct burner was installed in the exhaust duct of a micro-cogeneration unit for the evaluation. Three wire-mesh burners with different pressure drops were used. Each burner has a conical shape made from FeCrAL alloy mat and was designed based on a heat release per unit area of 2500 kW/m2 and a total heat release of 240kW at 100 percent excess air. The local momentum of the gaseous mixture introduced through the wire-mesh was adjusted so that the flame stabilized outside the burner mesh (surface combustion). Cold flow tests (i.e., the duct burner was off, but the microturbine was running) were conducted to measure the effect of different duct burner geometrical parameters on flow split between the combustion zone and the bypass channel, and on pressure drop across the duct burner. A considerable amount of detailed parametric experimental data was collected to investigate the performance characteristics of the duct burner. The variables studied (firing rate, mass flow ratio, conical burner pressure drop, blockage ratio, conical burner shield length, premixer geometry and inlet conditions) were all found to play an important role on emissions (NOx and CO), overall duct burner pressure drop and flame stability. The range of firing rates at which surface combustion was maintained for the duct burner was defined by direct observation of the burner surface and monitoring of the temperature in the combustion zone. Flame images were captured for qualitative assessment. The combustion tests results presented in this thesis proved that the design procedures that were implemented to design this novel microturbine conical wire-mesh duct burner were successful. During the course of the combustion tests, the duct burner displayed stable, low emissions operation throughout the surface firing rate range of 148 kW to 328 kW (1574 kW/m 2 to 3489 kW/m2). Emissions of less than 5 ppm (corrected to 15 percent 02) for NOx and CO emissions were recorded, while the duct burner successfully raised the microturbine exhaust gases temperature from about 227°C to as high as 700°C. The overall duct burner pressure drop throughout was consistently below the design limit of 249 Pa.

Food Fortification Stability Study

NASA Technical Reports Server (NTRS)

Abdulmalik, T. O.; Cooper, M. R.; Douglas, G. L.

2015-01-01

NASA has established the goal of traveling beyond low-Earth orbit and extending manned exploration to Mars. The extended length of a Mars mission, along with the lack of resupply missions increases the importance of nutritional content in the food system. The purpose of this research is to assess the stability of vitamin supplementation in traditionally processed spaceflight foods. It is expected that commercially available fortificants will remain stable through long-duration missions if proper formulation, processing, and storage temperatures are all achieved. Five vitamins (vitamin E, vitamin K, pantothenic acid, folic acid, and thiamin) were blended into a vitamin premix (DSM, Freeport, TX); premixes were formulated to be compatible with current processing techniques (retort or freeze-dried), varied water activities (high or low), and packaging material. The overall goal of this process is to provide 25% of the recommended daily intake of each vitamin (per serving), following processing and two years of ambient storage. Four freeze-dried foods (Scrambled Eggs, Italian Vegetables, Potatoes Au Gratin, Noodles and Chicken) and four thermostabilized foods (Curry Sauce with Vegetables, Chicken Noodle Soup, Grilled Pork Chop, Rice with Butter) were produced (with and without the vitamin premix), to assess the impact of the added fortificant on color and taste, and to determine the stability of supplemental vitamins in spaceflight foods. The use of fortification in spaceflight foods appears to be a plausible mitigation step to inadequate nutrition. This is due to the ease of vitamin addition as well as the sustainability of the premixes through initial processing steps. Postprocessing analysis indicated that vitamin fortification with this premix did not immediately impact organoleptic properties of the food. At this stage, the largest hurdle to fortification is the preciseness to which vitamins can be added; the total amount of vitamins required for production is 10 - 20 grams, a minor percentage of the formulation. As demonstrated by the over-fortification measured in Italian Vegetables and Grilled Pork Chop, homogeneity may be difficult to achieve with such small amounts. Thus, pouch-to-pouch variability, over-fortification, and underfortification may ensue if a method for precise addition is not identified. Stability will continue to be evaluated over two years of storage at three temperatures, and future analysis should reveal the extent to which this issue should be a concern

The cell division protein MinD from Pseudomonas aeruginosa dominates the assembly of the MinC-MinD copolymers.

PubMed

Huang, Haiyan; Wang, Ping; Bian, Li; Osawa, Masaki; Erickson, Harold P; Chen, Yaodong

2018-05-18

Cell division of rod-shaped bacteria requires the Z ring, a ring of FtsZ filaments associated with the inner-membrane wall. The MinCDE proteins help localize the Z ring to the center of the Escherichia coli cell. MinC, which inhibits Z-ring assembly, is a passenger on MinD. Previous studies have shown that MinC-MinD from E. coli and Aquifex aeolicus assemble in vitro into extended filaments with a 1:1 stoichiometry. However, a recent study has raised questions about the function of the MinC-MinD copolymer in vivo , because its assembly appears to require a high concentration of these two proteins and has a long lag time, and its blockade does not affect in vivo activities. Here, we found that MinC and MinD from Pseudomonas aeruginosa coassemble into filaments with a 1:1 stoichiometry. We also found that the minimal concentration of ∼4 μm required for assembly applies only to MinD because above 4 μm MinD, even very low MinC concentrations sustained coassembly. As previously reported, the MinC-MinD coassembly exhibited a long lag of ∼100 s when initiated by ATP. Premixing MinD with ATP eliminated this lag, suggesting that it may be due to slow MinD dimerization following ATP activation. We also discovered that MinC-MinD copolymers quickly bound FtsZ filaments and formed huge bundles. Our results resolve previous questions about the low concentration of MinC and the lag time, insights that may inform future investigations into the exact role of the MinC-MinD copolymer in vivo . © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Effects of Non-Equilibrium Plasmas on Low-Pressure, Premixed Flames. Part 1: CH* Chemiluminescence, Temperature, and OH

DTIC Science & Technology

2018-01-16

1    Effects of Non -Equilibrium Plasmas on Low-Pressure, Premixed Flames. Part 1: CH* Chemiluminescence, Temperature, and OH Ting Li, Igor V...investigate the effects of nanosecond, repetitively-pulsed, non -equilibrium plasma discharges on laminar, low-pressure, premixed burner-stabilized hydrogen/O2...sources, both of which generate uniform, low-temperature, volumetric, non -equilibrium plasma discharges, are used to study changes in

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

Kalantari, Alireza; Sullivan-Lewis, Elliot; McDonell, Vincent

Due to increasingly stringent air quality requirements stationary power gas turbines have moved to lean-premixed operation, which reduces pollutant emissions but can result in flashback. Curtailing flashback can be difficult with hydrocarbon fuels and becomes even more challenging when hydrogen is used as the fuel. In fact, flashback is a key operability issue associated with low emission combustion of high hydrogen content fuels. Flashback can cause serious damage to the premixer hardware. Hence, design tools to predict flashback propensity are of interest. Such a design tool has been developed based on the data gathered by experimental study to predict boundarymore » layer flashback using non-dimensional parameters. The flashback propensity of a premixed jet flame has been studied experimentally. Boundary layer flashback has been investigated under turbulent flow conditions at elevated pressures and temperatures (i.e. 3 atm to 8 atm and 300 K to 500 K). The data presented in this study are for hydrogen fuel at various Reynolds numbers, which are representative of practical gas turbine premixer conditions and are significantly higher than results currently available in the literature. Three burner heads constructed of different materials (stainless steel, copper, and zirconia ceramic) were used to evaluate the effect of tip temperature, a parameter found previously to be an important factor in triggering flashback. This study characterizes flashback systematically by developing a comprehensive non-dimensional model which takes into account all effective parameters in boundary layer flashback propensity. The model was optimized for new data and captures the behavior of the new results well. Further, comparison of the model with the single existing study of high pressure jet flame flashback also indicates good agreement. The model developed using the high pressure test rig is able to predict flashback tendencies for a commercial gas turbine engine and can thus serve as a design tool for identifying when flashback is likely to occur for a given geometry and condition.« less

Sealed, nozzle-mix burners for silica deposition

DOEpatents

Adler, Meryle D. M.; Brown, John T.; Misra, Mahendra K.

2003-07-08

Burners (40) for producing fused silica boules are provided. The burners employ a tube-in-tube (301-306) design with flats (56, 50) on some of the tubes (305, 301) being used to limit the cross-sectional area of certain passages (206, 202) within the burner and/or to atomize a silicon-containing, liquid source material, such as OMCTS. To avoid the possibility of flashback, the burner has separate passages for fuel (205) and oxygen (204, 206), i.e., the burner employs nozzle mixing, rather than premixing, of the fuel and oxygen. The burners are installed in burner holes (26) formed in the crown (20) of a furnace and form a seal with those holes so that ambient air cannot be entrained into the furnace through the holes. An external air cooled jacket (60) can be used to hold the temperature of the burner below a prescribed upper limit, e.g., 400.degree. C.

Joining of ceramics of different biofunction by hot isostatic pressing

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

Li, Jianguo; Harmansson, L.; Soeremark, R.

1993-10-01

Monolithic zirconia (Z) and zirconia-hydroxyapatite (Z/HA) composites were joined by cold isostatic pressing (CIP at 300 MPa) and subsequently by glass-encapsulated hot isostatic pressing (HIP at 1225 C, 1 h and 200 MPa). The physical and mechanical properties of the materials were measured. The fracture surface was studied using a light microscope. The results indicate a strength level of the joint similar to that of the corresponding composite material (Z/HA), 845 and 860 MPa, respectively. Similar experiments with monolithic alumina (A) and alumina-hydroxyapatite (A/HA) were carried out without success. Cracking occurred in the joint area during the cold isostatic pressingmore » process. It seems that ceramics with high green strength and similar green density are essential when joining ceramics by combined CIP and HIP processes.« less

Using Sandia's Z Machine and Density Functional Theory Simulations to Understand Planetary Materials

NASA Astrophysics Data System (ADS)

Root, Seth

2017-06-01

The use of Z, NIF, and Omega have produced many breakthrough results in high pressure physics. One area that has greatly benefited from these facilities is the planetary sciences. The high pressure behavior of planetary materials has implications for numerous geophysical and planetary processes. The continuing discovery of exosolar super-Earths demonstrates the need for accurate equation of state data to better inform our models of their interior structures. Planetary collision processes, such as the moon-forming giant impact, require understanding planetary materials over a wide-range of pressures and temperatures. Using Z, we examined the shock compression response of some common planetary materials: MgO, Mg2SiO4, and Fe2O3 (hematite). We compare the experimental shock compression measurements with density functional theory (DFT) based quantum molecular dynamics (QMD) simulations. The combination of experiment and theory provides clearer understanding of planetary materials properties at extreme conditions. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Experimental Investigation of Turbulence-Chemistry Interaction in High-Reynolds-Number Turbulent Partially Premixed Flames

DTIC Science & Technology

2016-06-23

4 . TITLE AND SUBTITLE [U] Experimental investigation of turbulence-chemistry interaction in high-Reynolds-number 5a. CONTRACT NUMBER turbulent...nonpremixed/partially premixed flames and turbulence-chemistry interaction. Turbulent mixing of mixture fraction has been studied extensively [ 4 , 14]. In a...two-feed non-premixed flame, the mixture fraction is defined as: ξ = Y − Yo YF − Yo (1) where Y is a conserved quantity such as the mass fraction of any

Swozzle based burner tube premixer including inlet air conditioner for low emissions combustion

DOEpatents

Tuthill, Richard Sterling; Bechtel, II, William Theodore; Benoit, Jeffrey Arthur; Black, Stephen Hugh; Bland, Robert James; DeLeonardo, Guy Wayne; Meyer, Stefan Martin; Taura, Joseph Charles; Battaglioli, John Luigi

2002-01-01

A burner for use in a combustion system of a heavy-duty industrial gas turbine includes a fuel/air premixer having an air inlet, a fuel inlet, and an annular mixing passage. The fuel/air premixer mixes fuel and air into a uniform mixture for injection into a combustor reaction zone. The burner also includes an inlet flow conditioner disposed at the air inlet of the fuel/air premixer for controlling a radial and circumferential distribution of incoming air. The pattern of perforations in the inlet flow conditioner is designed such that a uniform air flow distribution is produced at the swirler inlet annulus in both the radial and circumference directions. The premixer includes a swozzle assembly having a series of preferably air foil shaped turning vanes that impart swirl to the airflow entering via the inlet flow conditioner. Each air foil contains internal fuel flow passages that introduce natural gas fuel into the air stream via fuel metering holes that pass through the walls of the air foil shaped turning vanes. By injecting fuel in this manner, an aerodynamically clean flow field is maintained throughout the premixer. By injecting fuel via two separate passages, the fuel/air mixture strength distribution can be controlled in the radial direction to obtain optimum radial concentration profiles for control of emissions, lean blow outs, and combustion driven dynamic pressure activity as machine and combustor load are varied.

Drug utilization review of potassium chloride injection formulations available in a private hospital in kuching, sarawak, malaysia.

PubMed

Melissa, Mohammad Hirman; Azmi, Sarriff

2013-07-01

The concentrated potassium chloride injection is a high-alert medication and replacing it with a pre-mixed formulation can reduce the risks associated with its use. The aim of this study was to determine the clinical characteristics of patients receiving different potassium chloride formulations available at a private institution. The study also assessed the effectiveness and safety of pre-mixed formulations in the correction of hypokalaemia. This was a retrospective observational study consisting of 296 cases using concentrated and pre-mixed potassium chloride injections in 2011 in a private hospital in Kuching, Sarawak, Malaysia. There were 135 (45.6%) cases that received concentrated potassium chloride, and 161 (54.4%) cases that received pre-mixed formulations. The patients' clinical characteristics that were significantly related to the utilization of the different formulations were diagnosis (P < 0.001), potassium serum blood concentration (P < 0.05), and fluid overload risk (P < 0.05). The difference observed for the cases that achieved or maintained normokalaemia was statistically insignificant (P = 0.172). Infusion-related adverse effects were seen more in pre-mixes compared to concentrated formulations (6.8% versus 2.2%, P < 0.05). This study provides insight into the utilization of potassium chloride injections at this specific institution. The results support current recommendations to use pre-mixed formulations whenever possible.

Soot Formation in Freely-Propagating Laminar Premixed Flames

NASA Technical Reports Server (NTRS)

Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

1997-01-01

Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

Intrauterine-like growth rates can be achieved with premixed parenteral nutrition solution in preterm infants.

PubMed

Rigo, Jacques; Senterre, Thibault

2013-12-01

Growth failure in neonatal intensive care units is a major challenge for pediatricians and neonatologists. The use of early "aggressive" parenteral nutrition (PN), with >2.5 g/(kg ·d) of amino acids and at least 40 kcal/(kg ·d) of energy from the first day of life, has been shown to provide nutritional intakes in the range recommended by international guidelines, reducing nutritional deficit and the incidence of postnatal growth restriction in preterm infants. However, nutritional practices and adherence to recommendations may vary in different hospitals. Two ready-to-use (RTU), premixed parenteral solutions (PSs) designed for preterm infants have been prospectively evaluated: a binary RTU premixed PS from our hospital pharmacy and a commercially premixed 3-chamber bag (Baxter Healthcare). These premixed PSs provide nitrogen and energy intakes in the range of the most recent recommendations, reducing or eliminating the early cumulative nutritional deficit in very-low-birth-weight infants, and avoiding the development of postnatal growth restriction. A further rationale for RTU premixed PSs is that preterm infants require balanced PN that contains not only amino acids and energy but also minerals and electrolytes from the first day of life in order to reduce the incidence of metabolic disorders frequently reported in extremely-low-birth-weight infants during the early weeks of life.

Study of premixing phase of steam explosion with JASMINE code in ALPHA program

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

Moriyama, Kiyofumi; Yamano, Norihiro; Maruyama, Yu

Premixing phase of steam explosion has been studied in ALPHA Program at Japan Atomic Energy Research Institute (JAERI). An analytical model to simulate the premixing phase, JASMINE (JAERI Simulator for Multiphase Interaction and Explosion), has been developed based on a multi-dimensional multi-phase thermal hydraulics code MISTRAL (by Fuji Research Institute Co.). The original code was extended to simulate the physics in the premixing phenomena. The first stage of the code validation was performed by analyzing two mixing experiments with solid particles and water: the isothermal experiment by Gilbertson et al. (1992) and the hot particle experiment by Angelini et al.more » (1993) (MAGICO). The code predicted reasonably well the experiments. Effectiveness of the TVD scheme employed in the code was also demonstrated.« less

PREMIX: PRivacy-preserving EstiMation of Individual admiXture.

PubMed

Chen, Feng; Dow, Michelle; Ding, Sijie; Lu, Yao; Jiang, Xiaoqian; Tang, Hua; Wang, Shuang

2016-01-01

In this paper we proposed a framework: PRivacy-preserving EstiMation of Individual admiXture (PREMIX) using Intel software guard extensions (SGX). SGX is a suite of software and hardware architectures to enable efficient and secure computation over confidential data. PREMIX enables multiple sites to securely collaborate on estimating individual admixture within a secure enclave inside Intel SGX. We implemented a feature selection module to identify most discriminative Single Nucleotide Polymorphism (SNP) based on informativeness and an Expectation Maximization (EM)-based Maximum Likelihood estimator to identify the individual admixture. Experimental results based on both simulation and 1000 genome data demonstrated the efficiency and accuracy of the proposed framework. PREMIX ensures a high level of security as all operations on sensitive genomic data are conducted within a secure enclave using SGX.

One-pot hydrothermal synthesis of mesoporous Zn(x)Cd(1-x)S/reduced graphene oxide hybrid material and its enhanced photocatalytic activity.

PubMed

Wang, Xinwei; Tian, Hongwei; Cui, Xiaoqiang; Zheng, Weitao; Liu, Yichun

2014-09-14

We successfully synthesized mesoporous Zn(x)Cd(1-x)S/reduced graphene oxide (Z(x)CSG) hybrid materials as photocatalysts using a facile one-pot hydrothermal reaction, in which graphene oxide (GO) was easily reduced (RGO), and simultaneously Zn(x)Cd(1-x)S (Z(x)CS) nanoparticles (NPs) with a mesoporous structure were uniformly dispersed on the RGO sheets. By well tuning the band gap from 3.42 to 2.21 eV by changing the molar ratio of Zn/Cd (or Zn content), Z(x)CSG with an optimal zinc content has been found to have a significant absorption in the visible light (VL) region. In addition, under VL irradiation (λ > 420 nm), Z(x)CSG also showed zinc content-dependent photocatalytic efficiencies for the degradation of methylene blue (MB). Our findings are that, among Z(x)CSG, Z(0.4)CSG displayed not only a superior photodegradation efficiency of MB (98%), but also good removal efficiency of total organic carbon (TOC) (67%). Furthermore, Z(0.4)CSG had a high photocatalytic stability, and could be used repeatedly. The enhanced photocatalytic activity for Z(0.4)CSG could be attributed to a synergistic effect between mesoporous Z(x)CS NPs and RGO, including the optimal band gap and the moderate conduction band position for ZxCS (compared to CdS), efficient separation and transfer ability of photogenerated electron/hole pairs in the presence of RGO sheets, and relatively high surface area for both mesoporous Z(x)CS NPs and RGO.

Comparison of tokamak behaviour with tungsten and low-Z plasma facing materials

NASA Astrophysics Data System (ADS)

Philipps, V.; Neu, R.; Rapp, J.; Samm, U.; Tokar, M.; Tanabe, T.; Rubel, M.

2000-12-01

Graphite wall materials are used in present day fusion devices in order to optimize plasma core performance and to enable access to a large operational space. A large physics database exists for operation with these plasma facing materials, which also indicate their use in future devices with extended burn times. The radiation from carbon impurities in the edge and divertor regions strongly helps to reduce the peak power loads on the strike areas, but carbon radiation also supports the formation of MARFE instabilities which can hinder access to high densities. The main concerns with graphite are associated with its strong chemical affinity to hydrogen, which leads to chemical erosion and to the formation of hydrogen-rich carbon layers. These layers can store a significant fraction of the total tritium fuel, which might prevent the use of these materials in future tritium devices. High-Z plasma facing materials are much more advantageous in this sense, but these advantages compete with the strong poisoning of the plasma if they enter the plasma core. New promising experiences have been obtained with high-Z wall materials in several devices, about which a survey is given in this paper and which also addresses open questions for future research and development work.

Joint Symposium on Compatibility of Plastics/Materials with Explosives Processing Explosives Held in Albuquerque, New Mexico on 15-17 May 1979.

DTIC Science & Technology

1979-05-01

250 A. S. Tompa REAL-TIME LOW TEMPERATURE NC AND PBX 9404 DECOMPOSITION STUDIES ....................................... 276 ._- Dr. Hermann...the five major unit operations for multi-base cannon propellant; nitrocellulose dehydration , premixing, mixing, extruding and cutting. Throughout the...during facility design, a general process description is presented as follows: Thermal Dehydration Nitrocellulose (NC) slurry is fed to a continuous

Investigating the reversibility of structural modifications of Li xNi yMn zCo 1-y-zO₂ cathode materials during initial charge/discharge, at multiple length scales

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

Hwang, Sooyeon; Bak, Seong -Min; Kim, Seung Min

2015-08-11

In this work, we investigate the structural modifications occurring at the bulk, subsurface, and surface scales of Li xNi yMn zCo 1-y-zO₂ (NMC; y, z = 0.8, 0.1 and 0.4, 0.3, respectively) cathode materials during the initial charge/discharge. Various analytical tools, such as X-ray diffraction, selected-area electron diffraction, electron energy-loss spectroscopy, and high-resolution electron microscopy, are used to examine the structural properties of the NMC cathode materials at the three different scales. Cut-off voltages of 4.3 and 4.8 V are applied during the electrochemical tests as the normal and extreme conditions, respectively. The high-Ni-content NMC cathode materials exhibit unusual behaviors,more » which is deviate from the general redox reactions during the charge or discharge. The transition metal (TM) ions in the high-Ni-content NMC cathode materials, which are mostly Ni ions, are reduced at 4.8 V, even though TMs are usually oxidized to maintain charge neutrality upon the removal of Li. It was found that any changes in the crystallographic and electronic structures are mostly reversible down to the sub-surface scale, despite the unexpected reduction of Ni ions. However, after the discharge, traces of the phase transitions remain at the edges of the NMC cathode materials at the scale of a few nanometers (i.e., surface scale). This study demonstrates that the structural modifications in NMC cathode materials are induced by charge as well as discharge at multiple length scales. These changes are nearly reversible after the first cycle, except at the edges of the samples, which should be avoided because these highly localized changes can initiate battery degradation.« less

21 CFR 170.60 - Nitrites and/or nitrates in curing premixes.

Code of Federal Regulations, 2010 CFR

2010-04-01

... additives when combined in curing premixes with spices and/or other flavoring or seasoning ingredients that... hydrolyzed vegetable protein), oleoresins of spices, soy products, and spice extractives. Such food additives...

Vortex combustor for low NOX emissions when burning lean premixed high hydrogen content fuel

DOEpatents

Steele, Robert C; Edmonds, Ryan G; Williams, Joseph T; Baldwin, Stephen P

2012-11-20

A trapped vortex combustor. The trapped vortex combustor is configured for receiving a lean premixed gaseous fuel and oxidant stream, where the fuel includes hydrogen gas. The trapped vortex combustor is configured to receive the lean premixed fuel and oxidant stream at a velocity which significantly exceeds combustion flame speed in a selected lean premixed fuel and oxidant mixture. The combustor is configured to operate at relatively high bulk fluid velocities while maintaining stable combustion, and low NOx emissions. The combustor is useful in gas turbines in a process of burning synfuels, as it offers the opportunity to avoid use of diluent gas to reduce combustion temperatures. The combustor also offers the possibility of avoiding the use of selected catalytic reaction units for removal of oxides of nitrogen from combustion gases exiting a gas turbine.

Vortex combustor for low NOx emissions when burning lean premixed high hydrogen content fuel

DOEpatents

Steele, Robert C [Woodinville, WA; Edmonds, Ryan G [Renton, WA; Williams, Joseph T [Kirkland, WA; Baldwin, Stephen P [Winchester, MA

2009-10-20

A trapped vortex combustor. The trapped vortex combustor is configured for receiving a lean premixed gaseous fuel and oxidant stream, where the fuel includes hydrogen gas. The trapped vortex combustor is configured to receive the lean premixed fuel and oxidant stream at a velocity which significantly exceeds combustion flame speed in a selected lean premixed fuel and oxidant mixture. The combustor is configured to operate at relatively high bulk fluid velocities while maintaining stable combustion, and low NOx emissions. The combustor is useful in gas turbines in a process of burning synfuels, as it offers the opportunity to avoid use of diluent gas to reduce combustion temperatures. The combustor also offers the possibility of avoiding the use of selected catalytic reaction units for removal of oxides of nitrogen from combustion gases exiting a gas turbine.

LES/PDF studies of joint statistics of mixture fraction and progress variable in piloted methane jet flames with inhomogeneous inlet flows

NASA Astrophysics Data System (ADS)

Zhang, Pei; Barlow, Robert; Masri, Assaad; Wang, Haifeng

2016-11-01

The mixture fraction and progress variable are often used as independent variables for describing turbulent premixed and non-premixed flames. There is a growing interest in using these two variables for describing partially premixed flames. The joint statistical distribution of the mixture fraction and progress variable is of great interest in developing models for partially premixed flames. In this work, we conduct predictive studies of the joint statistics of mixture fraction and progress variable in a series of piloted methane jet flames with inhomogeneous inlet flows. The employed models combine large eddy simulations with the Monte Carlo probability density function (PDF) method. The joint PDFs and marginal PDFs are examined in detail by comparing the model predictions and the measurements. Different presumed shapes of the joint PDFs are also evaluated.

Numerical evaluation of equivalence ratio measurement using OH{sup *} and CH{sup *} chemiluminescence in premixed and non-premixed methane-air flames

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

Panoutsos, C.S.; Hardalupas, Y.; Taylor, A.M.K.P.

This work presents results from detailed chemical kinetics calculations of electronically excited OH (A{sup 2}{sigma}, denoted as OH{sup *}) and CH (A{sup 2}{delta}, denoted as CH{sup *}) chemiluminescent species in laminar premixed and non-premixed counterflow methane-air flames, at atmospheric pressure. Eight different detailed chemistry mechanisms, with added elementary reactions that account for the formation and destruction of the chemiluminescent species OH{sup *} and CH{sup *}, are studied. The effects of flow strain rate and equivalence ratio on the chemiluminescent intensities of OH{sup *}, CH{sup *} and their ratio are studied and the results are compared to chemiluminescent intensity ratio measurementsmore » from premixed laminar counterflow natural gas-air flames. This is done in order to numerically evaluate the measurement of equivalence ratio using OH{sup *} and CH{sup *} chemiluminescence, an experimental practise that is used in the literature. The calculations reproduced the experimental observation that there is no effect of strain rate on the chemiluminescent intensity ratio of OH{sup *} to CH{sup *}, and that the ratio is a monotonic function of equivalence ratio. In contrast, the strain rate was found to have an effect on both the OH{sup *} and CH{sup *} intensities, in agreement with experiment. The calculated OH{sup *}/CH{sup *} values showed that only five out of the eight mechanisms studied were within the same order of magnitude with the experimental data. A new mechanism, proposed in this work, gave results that agreed with experiment within 30%. It was found that the location of maximum emitted intensity from the excited species OH{sup *} and CH{sup *} was displaced by less than 65 and 115 {mu}m, respectively, away from the maximum of the heat release rate, in agreement with experiments, which is small relative to the spatial resolution of experimental methods applied to combustion applications, and, therefore, it is expected that intensity from the OH{sup *} and CH{sup *} excited radicals can be used to identify the location of the reaction zone. Calculations of the OH{sup *}/CH{sup *} intensity ratio for strained non-premixed counterflow methane-air flames showed that the intensity ratio takes different values from those for premixed flames, and therefore has the potential to be used as a criterion to distinguish between premixed and non-premixed reaction in turbulent flames. (author)« less

HSCT Sector Combustor Evaluations for Demonstration Engine

NASA Technical Reports Server (NTRS)

Greenfield, Stuart; Heberling, Paul; Kastl, John; Matulaitis, John; Huff, Cynthia

2004-01-01

In LET Task 10, critical development issues of the HSCT lean-burn low emissions combustor were addressed with a range of engineering tools. Laser diagnostics and CFD analysis were applied to develop a clearer understanding of the fuel-air premixing process and premixed combustion. Subcomponent tests evaluated the emissions and operability performance of the fuel-air premixers. Sector combustor tests evaluated the performance of the integrated combustor system. A 3-cup sector was designed and procured for laser diagnostics studies at NASA Glenn. The results of these efforts supported the earlier selection of the Cyclone Swirler as the pilot stage premixer and the IMFH (Integrated Mixer Flame Holder) tube as the main stage premixer of the LPP combustor. In the combustor system preliminary design subtask, initial efforts to transform the sector combustor design into a practical subscale engine combustor met with significant challenges. Concerns about the durability of a stepped combustor dome and the need for a removable fuel injection system resulted in the invention and refinement of the MRA (Multistage Radial Axial) combustor system in 1994. The MRA combustor was selected for the HSR Phase II LPP subscale combustor testing in the CPC Program.

Chaos in an imperfectly premixed model combustor.

PubMed

Kabiraj, Lipika; Saurabh, Aditya; Karimi, Nader; Sailor, Anna; Mastorakos, Epaminondas; Dowling, Ann P; Paschereit, Christian O

2015-02-01

This article reports nonlinear bifurcations observed in a laboratory scale, turbulent combustor operating under imperfectly premixed mode with global equivalence ratio as the control parameter. The results indicate that the dynamics of thermoacoustic instability correspond to quasi-periodic bifurcation to low-dimensional, deterministic chaos, a route that is common to a variety of dissipative nonlinear systems. The results support the recent identification of bifurcation scenarios in a laminar premixed flame combustor (Kabiraj et al., Chaos: Interdiscip. J. Nonlinear Sci. 22, 023129 (2012)) and extend the observation to a practically relevant combustor configuration.

Lean Premixed Combustion Stabilized by Low Swirl a Promising Concept for Practical Applications

NASA Technical Reports Server (NTRS)

Cheng, R. K.

1999-01-01

Since its inception, the low-swirl burner (LSB) has shown to be a useful laboratory apparatus for fundamental studies of premixed turbulent flames. The LSB operates under wide ranges of equivalence ratios, flow rates, and turbulence intensities. Its flame is lifted and detached from the burner and allows easy access for laser diagnostics. The flame brush is axisymmetric and propagates normal to the incident reactants. Therefore, the LSB is well suited for investigating detailed flame structures and empirical coefficients such as flame speed, turbulence transport, and flame generated turbulence. Due to its capability to stabilize ultra-lean premixed turbulent flames (phi approx. = 0.55), the LSB has generated interest from the gas appliance industry for use as an economical low-NO(x) burner. Lean premixed combustion emits low levels of NO(x), due primarily to the low flame temperature. Therefore, it is a very effective NO(x) prevention method without involving selective catalytic reduction (SCR), fuel-air staging, or flue gas recirculation (FGR). En the gas turbine industry, substantial research efforts have already been undertaken and engines with lean premixed combustors are already in use. For commercial and residential applications, premixed pulsed combustors and premixed ceramic matrix burners are commercially available. These lean premixed combustion technologies, however, tend to be elaborate but have relatively limited operational flexibility, and higher capital, operating and maintenance costs. Consequently, these industries are continuing the development of lean premixed combustion technologies as well as exploring new concepts. This paper summarizes the research effects we have undertaken in the past few years to demonstrate the feasibility of applying the low-swirl flame stabilization method for a wide range of heating and power generation systems. The principle of flame stabilization by low-swirl is counter to the conventional high-swirl methods that rely on a recirculation zone to anchor the flame. In LSBS, flow recirculation is not promoted to allow the premixed turbulent flames to propagate freely. A LSB with an air-jet swirler is essentially an open tube with the swirler at its mid section. The small air-jets generate swirling motion only in the annular region and leaving the central core of the flow undisturbed, When this flow exits the burner tube, the angular momentum generates radial mean pressure gradient to diverge the non-swirling reactants stream. Consequently, the mean flow velocity decreases linearly. Propagating against this decelerating flow, the flame self-sustains at the position where the local flow velocity equals the flame speed, S(sub f). The LSB operates with a swirl number, S, between 0.02 to 0.1. This is much lower than the minimum S of 0.6 required for the high-swirl burners. We found that the swirl number needed for flame stabilization varies only slightly with fuel type, flow velocity, turbulent conditions and burner dimensions (i.e. throat diameter and swirl injection angle).

Personalized intensification of insulin therapy in type 2 diabetes - does a basal-bolus regimen suit all patients?

PubMed

Giugliano, D; Sieradzki, J; Stefanski, A; Gentilella, R

2016-08-01

Many patients with type 2 diabetes mellitus (T2DM) require insulin therapy. If basal insulin fails to achieve glycemic control, insulin intensification is one possible treatment intensification strategy. We summarized clinical data from randomized clinical trials designed to compare the efficacy and safety of basal-bolus and premixed insulin intensification regimens. We defined a between-group difference of ≥0.3% in end-of-study glycated hemoglobin (HbA1c) as clinically meaningful. A PubMed database search supplemented by author-identified papers yielded 15 trials which met selection criteria: randomized design, patients with T2DM receiving basal-bolus (bolus injection ≤3 times/day) vs. premixed (≤3 injections/day) insulin regimens, primary/major endpoint(s) HbA1c- and/or hypoglycemia-related, and trial duration ≥12 weeks. Glycemic control improved with both basal-bolus and premixed insulin regimens with - in most cases - acceptable levels of weight gain and hypoglycemia. A clinically meaningful difference between regimens in glycemic control was recorded in only four comparisons, all of which favored basal-bolus therapy. The incidence of hypoglycemia was significantly different between regimens in only three comparisons, one of which favored premixed insulin and two basal-bolus therapy. Of the four trials that reported a significant difference between regimens in bodyweight change, two favored basal-bolus therapy and two favored premixed insulin. Thus, on a population level, neither basal-bolus therapy nor premixed insulin showed a consistent advantage in terms of glycemic control, hypoglycemic risk, or bodyweight gain. It is therefore recommended that clinicians should adopt an individualized approach to insulin intensification - taking into account the benefits and risks of each treatment approach and the attitude and preferences of each patient - in the knowledge that both basal-bolus and premixed regimens may be successful.

Premixed polymer concrete overlays.

DOT National Transportation Integrated Search

1990-01-01

The results of a study undertaken to evaluate premixed polymer concrete overlays (PMPCO) over a 3-year period are presented. The PMPCO evaluated were constructed with polyester amide para resin and silica sand 1;. polyester styrene resin 1 and silica...

Mechanisms of combustion limits in premixed gas flames at microgravity

NASA Technical Reports Server (NTRS)

Ronney, Paul D.

1991-01-01

A three-year experimental and theoretical research program on the mechanisms of combustion limits of premixed gasflames at microgravity was conducted. Progress during this program is identified and avenues for future studies are discussed.

An Investigation of a Hybrid Mixing Timescale Model for PDF Simulations of Turbulent Premixed Flames

NASA Astrophysics Data System (ADS)

Zhou, Hua; Kuron, Mike; Ren, Zhuyin; Lu, Tianfeng; Chen, Jacqueline H.

2016-11-01

Transported probability density function (TPDF) method features the generality for all combustion regimes, which is attractive for turbulent combustion simulations. However, the modeling of micromixing due to molecular diffusion is still considered to be a primary challenge for TPDF method, especially in turbulent premixed flames. Recently, a hybrid mixing rate model for TPDF simulations of turbulent premixed flames has been proposed, which recovers the correct mixing rates in the limits of flamelet regime and broken reaction zone regime while at the same time aims to properly account for the transition in between. In this work, this model is employed in TPDF simulations of turbulent premixed methane-air slot burner flames. The model performance is assessed by comparing the results from both direct numerical simulation (DNS) and conventional constant mechanical-to-scalar mixing rate model. This work is Granted by NSFC 51476087 and 91441202.

Laminar Premixed and Diffusion Flames (Ground-Based Study)

NASA Technical Reports Server (NTRS)

Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2000-01-01

Ground-based studies of soot processes in laminar flames proceeded in two phases, considering laminar premixed flames and laminar diffusion flames, in turn. The test arrangement for laminar premixed flames involved round flat flame burners directed vertically upward at atmospheric pressure. The test arrangement for laminar jet diffusion flames involved a round fuel port directed vertically upward with various hydrocarbon fuels burning at atmospheric pressure in air. In both cases, coflow was used to prevent flame oscillations and measurements were limited to the flame axes. The measurements were sufficient to resolve soot nucleation, growth and oxidation rates, as well as the properties of the environment needed to evaluate mechanisms of these processes. The experimental methods used were also designed to maintain capabilities for experimental methods used in corresponding space-based experiments. This section of the report will be limited to consideration of flame structure for both premixed and diffusion flames.

Internal baffling for fuel injector

DOEpatents

Johnson, Thomas Edward; Lacy, Benjamin; Stevenson, Christian

2014-08-05

A fuel injector includes a fuel delivery tube; a plurality of pre-mixing tubes, each pre-mixing tube comprising at least one fuel injection hole; an upstream tube support plate that supports upstream ends of the plurality of pre-mixing tubes; a downstream tube support plate that supports downstream ends of the plurality of pre-mixing tubes; an outer wall connecting the upstream tube support plate and the downstream tube support plate and defining a plenum therewith; and a baffle provided in the plenum. The baffle includes a radial portion. A fuel delivered in the upstream direction by the fuel delivery tube is directed radially outwardly in the plenum between the radial portion of the baffle and the downstream tube support plate, then in the downstream direction around an outer edge portion of the radial portion, and then radially inwardly between the radial portion and the upstream tube support plate.

[Methods quantitative for determination of water-soluble vitamins in premixes and fortified food products by micellar electrokinetic chromatography on short end of the capillary].

PubMed

Bogachuk, M N; Bessonov, V V; Perederiaev, O I

2011-01-01

It was purposed new technique by micellar electrokinetic chromatography on short end of the capillary (capillary electrophoresis system Agilent 3D CE, DAD, quartz capillary HPCE stndrd cap 56 cm, 50 microm, 50 mM borate buffer pH=9,3, 100 mM sodium dodecil sulfate) for simultaneous determination of water-soluble vitamins (B1, B2, B6, B12, PP, B5, B9, C, B8) in fortified food products and premixes. It was observed on 6 samples of vitamin premixes and 28 samples of fortified food products using this technique. Our findings are consistent with the results of research on certain vitamins, conducted by other methods. The developed technique can be used in analysis of water-soluble vitamins in premixes and fortified food products.

Effectiveness of insulin glargine in type 2 diabetes mellitus patients failing glycaemic control with premixed insulin: Adriatic countries data meta-analysis.

PubMed

Cigrovski Berkovic, Maja; Petrovski, Goran; Grulovic, Natasa

2016-10-01

Type 2 diabetes mellitus (T2DM) is a progressive disease, often requiring exogenous insulin therapy and treatment intensification. Despite new therapies, most patients do not reach the recommended HbA1c targets, among them a significant proportion of patients on premixed insulins. The aim was to summarize published data in Adriatic countries on effectiveness of insulin glargine based therapy in type 2 diabetic patients suboptimally controlled on premix insulin. A meta-analysis was carried out in major medical databases up to April 2014, focusing on Adriatic region. We searched observational studies with duration of at least 6 months, evaluating effectiveness and safety of insulin glargine (IGlar), in combination with OAD or bolus insulin in patients with T2 failing premixed insulin therapy. Outcomes included values of HbA1c, fasting blood glucose and two hours post-prandial glucose concentration as well as changes in body mass index after at least 6 months of study duration. Three prospective, observational, multicentric trials (698 patients in total) were included. The basal bolus regimen with glargine significantly reduced HbA1c (Mean Difference, MD=2.27, CI [1.76, 2.78]), fasting glucose (MD=5.15, CI [4.86, 5.44]) and 2-hours postprandial glucose concentration (MD=6.94, CI [6.53, 7.34]). No significant changes were found in BMI after switching from premixes to IGlar based treatment. Insulin glargine based therapy following premix failure is efficacious and safe option of type 2 diabetes treatment intensification.

Combustor with two stage primary fuel tube with concentric members and flow regulating

DOEpatents

Parker, David Marchant; Whidden, Graydon Lane; Zolyomi, Wendel

1999-01-01

A combustor for a gas turbine having a centrally located fuel nozzle and inner, middle and outer concentric cylindrical liners, the inner liner enclosing a primary combustion zone. The combustor has an air inlet that forms two passages for pre-mixing primary fuel and air to be supplied to the primary combustion zone. Each of the pre-mixing passages has a circumferential array of swirl vanes. A plurality of primary fuel tube assemblies extend through both pre-mixing passages, with each primary fuel tube assembly located between a pair of swirl vanes. Each primary fuel tube assembly is comprised of two tubular members. The first member supplies fuel to the first pre-mixing passage, while the second member, which extends through the first member, supplies fuel to the second pre-mixing passage. An annular fuel manifold is divided into first and second chambers by a circumferentially extending baffle. The proximal end of the first member is attached to the manifold itself while the proximal end of the second member is attached to the baffle. The distal end of the first member is attached directly to the second member at around its mid-point. The inlets of the first and second members are in flow communication with the first and second manifold chambers, respectively. Control valves separately regulate the flow of fuel to the two chambers and, therefore, to the two members of the fuel tube assemblies, thereby allowing the flow of fuel to the first and second pre-mixing passages to be separately controlled.

Studies of premixed laminar and turbulent flames at microgravity

NASA Technical Reports Server (NTRS)

Ronney, Paul D.

1993-01-01

A two and one-half year experimental and theoretical research program on the properties of laminar and turbulent premixed gas flames at microgravity was conducted. Progress during this program is identified and avenues for future studies are discussed.

Implementation of Premixed Equilibrium Chemistry Capability in OVERFLOW

NASA Technical Reports Server (NTRS)

Olsen, M. E.; Liu, Y.; Vinokur, M.; Olsen, T.

2003-01-01

An implementation of premixed equilibrium chemistry has been completed for the OVERFLOW code, a chimera capable, complex geometry flow code widely used to predict transonic flowfields. The implementation builds on the computational efficiency and geometric generality of the solver.

Implementation of Premixed Equilibrium Chemistry Capability in OVERFLOW

NASA Technical Reports Server (NTRS)

Olsen, Mike E.; Liu, Yen; Vinokur, M.; Olsen, Tom

2004-01-01

An implementation of premixed equilibrium chemistry has been completed for the OVERFLOW code, a chimera capable, complex geometry flow code widely used to predict transonic flowfields. The implementation builds on the computational efficiency and geometric generality of the solver.

Turbulent premixed flames on fractal-grid-generated turbulence

NASA Astrophysics Data System (ADS)

Soulopoulos, N.; Kerl, J.; Sponfeldner, T.; Beyrau, F.; Hardalupas, Y.; Taylor, A. M. K. P.; Vassilicos, J. C.

2013-12-01

A space-filling, low blockage fractal grid is used as a novel turbulence generator in a premixed turbulent flame stabilized by a rod. The study compares the flame behaviour with a fractal grid to the behaviour when a standard square mesh grid with the same effective mesh size and solidity as the fractal grid is used. The isothermal gas flow turbulence characteristics, including mean flow velocity and rms of velocity fluctuations and Taylor length, were evaluated from hot-wire measurements. The behaviour of the flames was assessed with direct chemiluminescence emission from the flame and high-speed OH-laser-induced fluorescence. The characteristics of the two flames are considered in terms of turbulent flame thickness, local flame curvature and turbulent flame speed. It is found that, for the same flow rate and stoichiometry and at the same distance downstream of the location of the grid, fractal-grid-generated turbulence leads to a more turbulent flame with enhanced burning rate and increased flame surface area.

The effect of cesium carbonate on 1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C{sub 61} aggregation in films

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

Lindemann, William R.; Wang, Wenjie; Shinar, Joseph

2014-11-10

Surface-pressure versus molecular area isotherms, X-ray reflectivity, and X-ray near-total reflection fluorescence were used to study the properties of 1-(3-methoxycarbonyl)propyl-1-phenyl[6,6]C{sub 61} (PCBM) that was pre-mixed with cesium carbonate and spread as a film at the air-water interface. The pre-mixed PCBM with cesium carbonate demonstrated a strikingly strong effect on the organization of the film. Whereas films formed from pure PCBM solution were rough due to strong inter-molecular interactions, the films formed from the mixture were much smoother. This indicates that the cesium carbonate moderates the inter-molecular interactions among PCBM molecules, hinting that the cesium diffusion observed in inverted organic photovoltaicmore » structures and the likely ensuing ionic Cs-PCBM interaction decrease aggregation tendency of PCBM. This implies that the use of cesium salts affects the morphology of the organic layer and consequently improves the efficiency of these devices.« less

Direct numerical simulation of a high Ka CH 4/air stratified premixed jet flame

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

Wang, Haiou; Hawkes, Evatt R.; Savard, Bruno

Here, direct numerical simulation (DNS) of a high Karlovitz number (Ka) CH 4/air stratified premixed jet flame was performed and used to provide insights into fundamentals of turbulent stratified premixed flames and their modelling implications. The flame exhibits significant stratification where the central jet has an equivalence ratio of 0.4, which is surrounded by a pilot flame with an equivalence ratio of 0.9. A reduced chemical mechanism for CH 4/air combustion based on GRI-Mech3.0 was used, including 268 elementary reactions and 28 transported species.

A high-pressure premixed flat-flame burner for chemical process studies. [of pollutant formation in hydrocarbon flames

NASA Technical Reports Server (NTRS)

Miller, I. M.

1978-01-01

A premixed flat-flame burner was designed and tested with methane-air mixtures at pressures from 1.1 to 20 atm and equivalence ratios from 0.7 to 1.1. Reactant velocity in the burner mixing chamber was used to characterize the range of stable flames at each pressure-equivalence-ratio condition. Color photographs of the flames were used to determine flame zone thickness and flame height. The results show that this burner can be used for chemical process studies in premixed high pressure methane-air flames up to 20 atm.

Direct numerical simulation of a high Ka CH 4/air stratified premixed jet flame

DOE PAGES

Wang, Haiou; Hawkes, Evatt R.; Savard, Bruno; ...

2018-04-24

Here, direct numerical simulation (DNS) of a high Karlovitz number (Ka) CH 4/air stratified premixed jet flame was performed and used to provide insights into fundamentals of turbulent stratified premixed flames and their modelling implications. The flame exhibits significant stratification where the central jet has an equivalence ratio of 0.4, which is surrounded by a pilot flame with an equivalence ratio of 0.9. A reduced chemical mechanism for CH 4/air combustion based on GRI-Mech3.0 was used, including 268 elementary reactions and 28 transported species.

Flow-combustion interactions in ducted flameholder-stabilized premixed flames

NASA Astrophysics Data System (ADS)

Soteriou, Marios; Arienti, Marco; Erickson, Robert

2006-11-01

Turbulent premixed combustion is present in many power generation and propulsion systems due to its large energy conversion rate (as compared to non-premixed combustion) and its potential for reduced emissions (at the lean limit). As a result, the study of turbulent premixed flames has received substantial attention in the past through experiment, analysis and simulation. In the recent past, unsteady Computational Fluid Dynamics (CFD) based models have been increasingly leveraged towards the in depth study of the physics of turbulent premixed flames. The bulk of this effort focuses on the response of the flame to turbulence. In contrast, we focus on the opposite problem, i.e. the modification of the turbulent flowfield by the flame. This topic has also received some attention but with a strong emphasis on planar (in the mean), flames propagating normal to the flow. Instead, we focus on flameholder-stabilized ducted flames, i.e. ones in which the flame is confined and substantially inclined to the incoming flow. The fundamental mechanisms by which the flame impacts the flow, i.e. dilatation, baroclinic vorticity generation and molecular diffusion enhancement are discussed in detail and their relative impact quantified. Limitations of modeling these mechanisms in current state of the art CFD models are also addressed.

Additive Manufacturing of Reactive In Situ Zr Based Ultra-High Temperature Ceramic Composites

NASA Astrophysics Data System (ADS)

Sahasrabudhe, Himanshu; Bandyopadhyay, Amit

2016-03-01

Reactive in situ multi-material additive manufacturing of ZrB2-based ultra-high-temperature ceramics in a Zr metal matrix was demonstrated using LENS™. Sound metallurgical bonding was achieved between the Zr metal and Zr-BN composites with Ti6Al4V substrate. Though the feedstock Zr power had α phase, LENS™ processing of the Zr powder and Zr-BN premix powder mixture led to the formation of some β phase of Zr. Microstructure of the Zr-BN composite showed primary grains of zirconium diboride phase in zirconium metal matrix. The presence of ZrB2 ceramic phase was confirmed by X-ray diffraction (XRD) analysis. Hardness of pure Zr was measured as 280 ± 12 HV and, by increasing the BN content in the feedstock, the hardness was found to increase. In Zr-5%BN composite, the hardness was 421 ± 10 HV and the same for Zr-10%BN composite was 562 ± 10 HV. It is envisioned that such multi-materials additive manufacturing will enable products in the future that cannot be manufactured using traditional approaches particularly in the areas of high-temperature metal-ceramic composites with compositional and functional gradation.

A grey incidence algorithm to detect high-Z material using cosmic ray muons

NASA Astrophysics Data System (ADS)

He, W.; Xiao, S.; Shuai, M.; Chen, Y.; Lan, M.; Wei, M.; An, Q.; Lai, X.

2017-10-01

Muon scattering tomography (MST) is a method for using cosmic muons to scan cargo containers and vehicles for special nuclear materials. However, the flux of cosmic ray muons is low, in the real life application, the detection has to be done a short timescale with small numbers of muons. In this paper, we present a novel approach to detection of special nuclear material by using cosmic ray muons. We use the degree of grey incidence to distinguish typical waste fuel material, uranium, from low-Z material, medium-Z material and other high-Z materials of tungsten and lead. The result shows that using this algorithm, it is possible to detect high-Z materials with an acceptable timescale.

Stability of Vitamin A, Iron and Zinc in Fortified Rice during Storage and Its Impact on Future National Standards and Programs—Case Study in Cambodia

PubMed Central

Kuong, Khov; Laillou, Arnaud; Chea, Chantum; Chamnan, Chhoun; Berger, Jacques; Wieringa, Frank T.

2016-01-01

Fortified rice holds great potential for bringing essential micronutrients to a large part of the world population. The present study quantified the losses of three different micronutrients (vitamin A, iron, zinc) in fortified rice that were produced using three different techniques (hot extrusion, cold extrusion, and coating) and stored at two different environments (25 ± 5 °C at a humidity of 60% and 40 ± 5 °C at a humidity of 75%) for up to one year. Fortified rice premix from the different techniques was mixed with normal rice in a 1:100 ratio. Each sample was analyzed in triplicate. The study confirmed the high stability of iron and zinc during storage while the retention of vitamin A was significantly affected by storage and the type of techniques used to make rice premix. Losses for iron and zinc were typically <10% for any type of rice premix. After 12 months at mild conditions (25 °C and humidity of 60%), losses for vitamin A ranged from 20% for cold extrusion, 30% for hot extruded rice 77% for coated rice premix. At higher temperatures and humidity, losses of vitamin A were 40%–50% for extruded premix and 93% for coated premix after 6 months. We conclude that storage does lead to a major loss of vitamin A and question whether rice is a suitable food vehicle to fortify with vitamin A. For Cambodia, fortification of rice with iron and zinc could be an effective strategy to improve the micronutrient status of the population if no other food vehicles are available. PMID:26784227

Worldwide Environmental Compliance Assessment and Management Program (ECAMP). German Supplement

DTIC Science & Technology

1991-01-01

auditing of technical installations. The law for the Protection from Harmful Effects from Air Pollution, Noise, Vibrations, and Similar Processes (The...when handling carcinogenic work materials); - Standard Publication number ZH 1/140 (Safety regulations for air polution prevention in work areas); - Z111

Embedded computer controlled premixing inline injection system for air-assisted variable-rate sprayers

USDA-ARS?s Scientific Manuscript database

Improvements to reduce chemical waste and environmental pollution for variable-rate sprayers used in orchards and ornamental nurseries require inline injection techniques. A microprocessor controlled premixing inline injection system implementing a ceramic piston chemical metering pump and two small...

Premix formulation for making the Indonesian otak-otak

NASA Astrophysics Data System (ADS)

Tawali, A. B.; Wakiah, N.; Ramli, A. R.; Mahendradatta, M.; Tawali, S.; Made, S.

2018-05-01

Otak-otak is one indigenous foods from Indonesia which made from fish paste, tapioca flour and spices. The aim of this research was to produce premix flour for making otak-otak using mackerel surimi, tapioca flour and spices and to evaluate their chemical properties and sensory acceptability of the product. Mackerel surimi was first dried, miled into powder form then mixed with tapioca flour and spices. The result showed that, otak-otak which made from Premix-B formula (40% mackerel surimi powder and 60% tapioca flour) was the best result for all sensory attributes. It presented “like moderately” for hedonic score. Protein, ash, moisture, carbohydrate, and fat contents of the premix-B formula were 23.51%, 2.44%, 7.31%, 71.02%, 4.28%, respectively, which met the SNI requirements. Overall, this study clearly showed that it was possible to make otak-otak with less complicated process and the product did not have any negative results on sensory perception.

The structure of partially-premixed methane/air flames under varying premixing

NASA Astrophysics Data System (ADS)

Kluzek, Celine; Karpetis, Adonios

2008-11-01

The present work examines the spatial and scalar structure of laminar, partially premixed methane/air flames with the objective of developing flamelet mappings that capture the effect of varying premixture strength (air addition in fuel.) Experimental databases containing full thermochemistry measurements within laminar axisymmetric flames were obtained at Sandia National Laboratories, and the measurements of all major species and temperature are compared to opposed-jet one-dimensional flow simulation using Cantera and the full chemical kinetic mechanism of GRI 3.0. Particular emphasis is placed on the scalar structure of the laminar flames, and the formation of flamelet mappings that capture all of the salient features of thermochemistry in a conserved scalar representation. Three different premixture strengths were examined in detail: equivalence ratios of 1.8, 2.2, and 3.17 resulted in clear differences in the flame scalar structure, particularly in the position of the rich premixed flame zone and the attendant levels of major and intermediate species (carbon monoxide and hydrogen).

Pdf modeling for premixed turbulent combustion based on the properties of iso-concentration surfaces

NASA Technical Reports Server (NTRS)

Vervisch, L.; Kollmann, W.; Bray, K. N. C.; Mantel, T.

1994-01-01

In premixed turbulent flames the presence of intense mixing zones located in front of and behind the flame surface leads to a requirement to study the behavior of iso-concentration surfaces defined for all values of the progress variable (equal to unity in burnt gases and to zero in fresh mixtures). To support this study, some theoretical and mathematical tools devoted to level surfaces are first developed. Then a database of direct numerical simulations of turbulent premixed flames is generated and used to investigate the internal structure of the flame brush, and a new pdf model based on the properties of iso-surfaces is proposed.

The effect of incomplete fuel-air mixing on the lean blowout limit, lean stability limit and NO(x) emissions in lean premixed gas turbine combustors

NASA Technical Reports Server (NTRS)

Shih, W.-P.; Lee, J. G.; Santavicca, D. A.

1994-01-01

Gas turbine engines for both land-based and aircraft propulsion applications are facing regulations on NOx emissions which cannot be met with current combustor technology. A number of alternative combustor strategies are being investigated which have the potential capability of achieving ultra-low NOx emissions, including lean premixed combustors, direct injection combustors, rich burn-quick quench-lean burn combustors and catalytic combustors. The research reported in this paper addresses the effect of incomplete fuel-air mixing on the lean limit performance and the NOx emissions characteristics of lean premixed combustors.

Dynamic properties of combustion instability in a lean premixed gas-turbine combustor.

PubMed

Gotoda, Hiroshi; Nikimoto, Hiroyuki; Miyano, Takaya; Tachibana, Shigeru

2011-03-01

We experimentally investigate the dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor from the viewpoint of nonlinear dynamics. A nonlinear time series analysis in combination with a surrogate data method clearly reveals that as the equivalence ratio increases, the dynamic behavior of the combustion instability undergoes a significant transition from stochastic fluctuation to periodic oscillation through low-dimensional chaotic oscillation. We also show that a nonlinear forecasting method is useful for predicting the short-term dynamic behavior of the combustion instability in a lean premixed gas-turbine combustor, which has not been addressed in the fields of combustion science and physics.

Laser Hybrid Fabrication of Nanoporous Structures on Metallic Material Surface

DTIC Science & Technology

2009-06-01

Research Center, Department of Mechanical Engineering,Beijing, 100084&# 65292 ;China, 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING...rials, 2005, 15: 989-994. [9]Jia F, Yu C, Ai Z, et al. Fabrication of nanoporous gold film electrodes with ultrahigh surface area and electro

A uniaxial cyclic compression method for characterizing the rheological and textural behaviors of mechanically dewatered sewage sludge.

PubMed

Liang, Fenglin; Sauceau, Martial; Dusserre, Gilles; Arlabosse, Patricia

2017-04-15

The mechanically dewatered sewage sludge with total solid content around 20% on a weight basis is very similar to yield stress fluid, its complex transition between solid and fluid states is not perfectly reversible and especially challenging in terms of pumping, land spreading and drying. To characterize the rheological and textural properties of highly concentrated sludge, a specific methodology based on uniaxial single and cyclic compression tests is developed. Three types of sludge samples (fresh original, fresh premixed and aged original ones) are extruded into cylinders and pressed between two parallel plates using a material testing machine. In single compression, the bioyield point beyond which the sludge fractures is around 7.3 kPa with true strain equal to 0.21. The cyclic compression tests reveal that the sludge behaves as a viscoelastic body when the true strain is smaller than 0.05 and as a visco-elasto-plastic once exceeding the yield stress. The elastic module is around 78 kPa; the viscosity is deduced, in the order of magnitude 10 4 -10 5  Pa·s and the yield stress is estimated about 4 kPa. In the unloading phase, the sludge behaves again as a viscoelastic body with clear hysteresis. With the increase of compression speed, the viscosity declines, which confirms that the sludge is a shear-thinning material. The yield stress and the bioyield increase with compression speed, but it does not induce extra internal damage in the samples since the resilience and the cohesiveness are unaltered. The reliability and sensitivity of the method is justified by highlighting the changes of sludge behavior due to aging and premixing effects: both decrease the strain energy density, but do aggravate the adhesiveness of the sludge; the aging makes the sludge less cohesive, while the premixing does not modify its cohesiveness. In spite of changes in test conditions, the elastic module of sludge samples remains unchanged. Copyright © 2017 Elsevier Ltd. All rights reserved.

Does the newer preparation of propofol, an emulsion of medium/long chain triglycerides cause less injection pain in children when premixed with lignocaine?

PubMed

Varghese, Elsa; Krishna, Handattu Mahabaleswara; Nittala, Anuradha

2010-04-01

Injection pain during propofol administration can be particularly distressing in children. The newly available emulsion of propofol in medium and long chain triglycerides (LCT) is reported to cause less injection pain because of lower concentrations of free propofol. This study compared the incidence of injection pain during administration of propofol emulsion of LCT and propofol emulsion of medium and long chain triglycerides (MCT/LCT) both premixed with lignocaine in children. This prospective, randomized, double blind study was conducted after obtaining institutional ethics committee approval, parental consent and included 84 children aged 5-15 years. Preoperatively, an intravenous cannula was inserted in all children. four children were excluded. Those included, depending on the randomization, received 3 mg x kg(-1) of either propofol LCT or propofol MCT/LCT both premixed with lignocaine (0.1%). The incidence and intensity of injection pain was assessed. Pain on injection of propofol LCT with lignocaine was observed in 16/40 children (40%), five of these children complained of severe pain. In comparison, 14/40 (35%) children complained of pain following propofol MCT/LCT premixed with lignocaine (P = 0.644), the intensity being severe in two children (P = 0.698). Propofol MCT/LCT and propofol LCT premixed with lignocaine are both associated with pain on injection in children; the incidence and intensity of the injection pain are similar.

Turbulent flame propagation in partially premixed flames

NASA Technical Reports Server (NTRS)

Poinsot, T.; Veynante, D.; Trouve, A.; Ruetsch, G.

1996-01-01

Turbulent premixed flame propagation is essential in many practical devices. In the past, fundamental and modeling studies of propagating flames have generally focused on turbulent flame propagation in mixtures of homogeneous composition, i.e. a mixture where the fuel-oxidizer mass ratio, or equivalence ratio, is uniform. This situation corresponds to the ideal case of perfect premixing between fuel and oxidizer. In practical situations, however, deviations from this ideal case occur frequently. In stratified reciprocating engines, fuel injection and large-scale flow motions are fine-tuned to create a mean gradient of equivalence ratio in the combustion chamber which provides additional control on combustion performance. In aircraft engines, combustion occurs with fuel and secondary air injected at various locations resulting in a nonuniform equivalence ratio. In both examples, mean values of the equivalence ratio can exhibit strong spatial and temporal variations. These variations in mixture composition are particularly significant in engines that use direct fuel injection into the combustion chamber. In this case, the liquid fuel does not always completely vaporize and mix before combustion occurs, resulting in persistent rich and lean pockets into which the turbulent flame propagates. From a practical point of view, there are several basic and important issues regarding partially premixed combustion that need to be resolved. Two such issues are how reactant composition inhomogeneities affect the laminar and turbulent flame speeds, and how the burnt gas temperature varies as a function of these inhomogeneities. Knowledge of the flame speed is critical in optimizing combustion performance, and the minimization of pollutant emissions relies heavily on the temperature in the burnt gases. Another application of partially premixed combustion is found in the field of active control of turbulent combustion. One possible technique of active control consists of pulsating the fuel flow rate and thereby modulating the equivalence ratio (Bloxsidge et al. 1987). Models of partially premixed combustion would be extremely useful in addressing all these questions related to practical systems. Unfortunately, the lack of a fundamental understanding regarding partially premixed combustion has resulted in an absence of models which accurately capture the complex nature of these flames. Previous work on partially premixed combustion has focused primarily on laminar triple flames. Triple flames correspond to an extreme case where fuel and oxidizer are initially totally separated (Veynante et al. 1994 and Ruetsch et al. 1995). These flames have a nontrivial propagation speed and are believed to be a key element in the stabilization process of jet diffusion flames. Different theories have also been proposed in the literature to describe a turbulent flame propagating in a mixture with variable equivalence ratio (Muller et al. 1994), but few validations are available. The objective of the present study is to provide basic information on the effects of partial premixing in turbulent combustion. In the following, we use direct numerical simulations to study laminar and turbulent flame propagation with variable equivalence ratio.

An experimental and numerical study of the inwardly-propagating premixed flame

NASA Astrophysics Data System (ADS)

Ibarreta, Alfonso F.

Flame stretch, described as the time rate of change of the flame surface area, can cause large changes in burning velocity of laminar premixed flames. Many experimental studies have been conducted to quantify the effects of flame stretch, but most only deal with the hydrodynamic strain component of stretch rate. In this thesis, a new experimental technique was used to study the inwardly-propagating premixed flame. This flame configuration is significant because it is subjected to the curvature component of stretch rate without the competing effects of hydrodynamic strain. Inwardly-propagating premixed flames were formed using a vortex to wrinkle a flame and create a pocket of reactants. Experiments using lean propane/air mixtures were run at both one-g and microgravity conditions to optimize the formation of large pockets of reactants. Numerical simulations of the inwardly-propagating flame (IPF) and outwardly-propagating flame (OPF) were performed for lean propane/air, methane/air and hydrogen/air mixtures. Complex chemistry as well as three different one-step reaction models were employed. Markstein numbers obtained from the experiments and computations were compared to OPF experimental data available in the literature. Researchers have used different definitions of flame location and burning velocity; the effects of these differences on the Markstein number were assessed. Experimental and numerical results indicate that the Markstein numbers obtained for the IPF are typically two to three times larger than those for the OPF. It was concluded that the observed difference in Markstein number was not caused by the IPF flame-flame interaction or the presence of intermediate species. Analysis of results obtained from the one-step reaction models identified the reasons for the difference between IPFs and OPFs: (A) the thermo-diffusive mechanism, (B) the pure curvature mechanism and (C) gas expansion. The consumption speed (Sc) was found to depend only on the thermo-diffusive mechanism and to be less sensitive to the flame geometry than the displacement velocity (Su). Observed differences between IPF and OPF results lead to the conclusion that the effects of curvature and strain cannot be grouped into a single term, but two separate Markstein numbers should be defined, one for curvature and one for strain.

Composite analysis E-area vaults and saltstone disposal facilities

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

Cook, J.R.

1997-09-01

This report documents the Composite Analysis (CA) performed on the two active Savannah River Site (SRS) low-level radioactive waste (LLW) disposal facilities. The facilities are the Z-Area Saltstone Disposal Facility and the E-Area Vaults (EAV) Disposal Facility. The analysis calculated potential releases to the environment from all sources of residual radioactive material expected to remain in the General Separations Area (GSA). The GSA is the central part of SRS and contains all of the waste disposal facilities, chemical separations facilities and associated high-level waste storage facilities as well as numerous other sources of radioactive material. The analysis considered 114 potentialmore » sources of radioactive material containing 115 radionuclides. The results of the CA clearly indicate that continued disposal of low-level waste in the saltstone and EAV facilities, consistent with their respective radiological performance assessments, will have no adverse impact on future members of the public.« less

LeRC in-house experimental research

NASA Technical Reports Server (NTRS)

Lyons, Valerie J.

1992-01-01

The topics covered include the following: LeRC in-house experimental research; combustion concepts; schedule for in-house experiments; lean premixed prevaporized combustion; comparisons of low NO(x) lean premixed/prevaporized data; rich burn/quick quench/lean burn (RQL); RQL combustion; fuel rich catalytic combustion; advanced diagnostics; and ceramic matrix liner test rig.

21 CFR 573.685 - Natamycin.

Code of Federal Regulations, 2011 CFR

2011-04-01

... composed of calcium carbonate, natamycin, and lactose) is used for retarding the growth of Aspergillus... g of lactose. The premix shall be mixed into broiler chicken feed at the rate of 1 pound (0.454... consisting of calcium carbonate, the additive, and lactose and their proportions in the premix as prescribed...

21 CFR 573.685 - Natamycin.

Code of Federal Regulations, 2010 CFR

2010-04-01

... composed of calcium carbonate, natamycin, and lactose) is used for retarding the growth of Aspergillus... g of lactose. The premix shall be mixed into broiler chicken feed at the rate of 1 pound (0.454... consisting of calcium carbonate, the additive, and lactose and their proportions in the premix as prescribed...

Dynamics and structure of turbulent premixed flames

NASA Technical Reports Server (NTRS)

Bilger, R. W.; Swaminathan, N.; Ruetsch, G. R.; Smith, N. S. A.

1995-01-01

In earlier work (Mantel & Bilger, 1994) the structure of the turbulent premixed flame was investigated using statistics based on conditional averaging with the reaction progress variable as the conditioning variable. The DNS data base of Trouve and Poinsot (1994) was used in this investigation. Attention was focused on the conditional dissipation and conditional axial velocity in the flame with a view to modeling these quantities for use in the conditional moment closure (CMC) approach to analysis of kinetics in premixed flames (Bilger, 1993). Two remarkable findings were made: there was almost no acceleration of the axial velocity in the flame front itself; and the conditional scalar dissipation remained as high, or higher, than that found in laminar premixed flames. The first finding was surprising since in laminar flames all the fluid acceleration occurs through the flame front, and this could be expected also for turbulent premixed flames at the flamelet limit. The finding gave hope of inventing a new approach to the dynamics of turbulent premixed flames through use of rapid distortion theory or an unsteady Bernoulli equation. This could lead to a new second order closure for turbulent premixed flames. The second finding was contrary to our measurements with laser diagnostics in lean hydrocarbon flames where it is found that conditional scalar dissipation drops dramatically below that for laminar flamelets when the turbulence intensity becomes high. Such behavior was not explainable with a one-step kinetic model, even at non-unity Lewis number. It could be due to depletion of H2 from the reaction zone by preferential diffusion. The capacity of the flame to generate radicals is critically dependent on the levels of H2 present (Bilger, et al., 1991). It seemed that a DNS computation with a multistep reduced mechanism would be worthwhile if a way could be found to make this feasible. Truly innovative approaches to complex problems often come only when there is the opportunity to work close at hand with the (in this case numerical) experimental data. Not only can one spot patterns and relationships in the data which could be important, but one can also get to know the limitations of the technique being used, so that when the next experiment is being designed it will address resolvable questions. A three-year grant from the Australian Research Council has enabled us to develop a small capability at the University of Sydney to work on DNS of turbulent reacting flow, and to analyze data bases generated at CTR. Collaboration between the University of Sydney and CTR is essential to this project and finding a workable modus operandum for this collaboration, given the constraints involved, has been a major objective of the past year's effort. The overall objectives of the project are: (1) to obtain a quantitative understanding of the dynamics of turbulent premixed flames at high turbulence levels with a view to developing improved second order closure models; and (2) to carry out new DNS experiments on turbulent premixed flames using a carefully chosen multistep reduced mechanism for the chemical kinetics, with a view to elucidating the laser diagnostic findings that are contrary to the findings for DNS using one-step kinetics. In this first year the objectives have been to make the existing CTR data base more accessible to coworkers at the University of Sydney, to make progress on understanding the dynamics of the flame in this existing CTR data base, and to carefully construct a suitable multistep reduced mechanism for use in a new set of DNS experiments on turbulent premixed flames.

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

Pickenheim, B.; Hansen, E.; Leishear, R.

A 10-inch READCO mixer is used for mixing the premix (45 (wt%) fly ash, 45 wt% slag, and 10 wt% portland cement) with salt solution in the Saltstone Production Facility (SPF). The Saltstone grout free falls into the grout hopper which feeds the suction line leading to the Watson SPX 100 duplex hose pump. The Watson SPX 100 pumps the grout through approximately 1500 feet of piping prior to being discharged into the Saltstone Disposal Facility (SDF) vaults. The existing grout hopper has been identified by the Saltstone Enhanced Low Activity Waste Disposal (ELAWD) project for re-design. The current nominalmore » working volume of this hopper is 12 gallons and does not permit handling an inadvertent addition of excess dry feeds. Saltstone Engineering has proposed a new hopper tank that will have a nominal working volume of 300 gallons and is agitated with a mechanical agitator. The larger volume hopper is designed to handle variability in the output of the READCO mixer and process upsets without entering set back during processing. The objectives of this task involve scaling the proposed hopper design and testing the scaled hopper for the following processing issues: (1) The effect of agitation on radar measurement. Formation of a vortex may affect the ability to accurately measure the tank level. The agitator was run at varying speeds and with varying grout viscosities to determine what parameters cause vortex formation and whether measurement accuracy is affected. (2) A dry feeds over addition. Engineering Calculating X-ESR-Z-00017 1 showed that an additional 300 pounds of dry premix added to a 300 gallon working volume would lower the water to premix ratio (W/P) from the nominal 0.60 to 0.53 based on a Salt Waste Processing Facility (SWPF) salt simulant. A grout with a W/P of 0.53 represents the upper bound of grout rheology that could be processed at the facility. A scaled amount of dry feeds will be added into the hopper to verify that this is a recoverable situation. (3) The necessity of baffles in the hopper. The preference of the facility is not to have baffles in the hopper; however, if the initial testing indicates inadequate agitation or difficulties with the radar measurement, baffles will be tested.« less

Large eddy simulation of premixed and non-premixed combustion in a Stagnation Point Reverse Flow combustor

NASA Astrophysics Data System (ADS)

Undapalli, Satish

A new combustor referred to as Stagnation Point Reverse Flow (SPRF) combustor has been developed at Georgia Tech to meet the increasingly stringent emission regulations. The combustor incorporates a novel design to meet the conflicting requirements of low pollution and high stability in both premixed and non-premixed modes. The objective of this thesis work is to perform Large Eddy Simulations (LES) on this lab-scale combustor and elucidate the underlying physics that has resulted in its excellent performance. To achieve this, numerical simulations have been performed in both the premixed and non-premixed combustion modes, and velocity field, species field, entrainment characteristics, flame structure, emissions, and mixing characteristics have been analyzed. Simulations have been carried out first for a non-reactive case to resolve relevant fluid mechanics without heat release by the computational grid. The computed mean and RMS quantities in the non-reacting case compared well with the experimental data. Next, the simulations were extended for the premixed reactive case by employing different sub-grid scale combustion chemistry closures: Eddy Break Up (EBU), Artificially Thickened Flame (TF) and Linear Eddy Mixing (LEM) models. Results from the EBU and TF models exhibit reasonable agreement with the experimental velocity field. However, the computed thermal and species fields have noticeable discrepancies. Only LEM with LES (LEMLES), which is an advanced scalar approach, has been able to accurately predict both the velocity and species fields. Scalar mixing plays an important role in combustion, and this is solved directly at the sub-grid scales in LEM. As a result, LEM accurately predicts the scalar fields. Due to the two way coupling between the super-grid and sub-grid quantities, the velocity predictions also compare very well with the experiments. In other approaches, the sub-grid effects have been either modeled using conventional approaches (EBU) or need some ad hoc adjustments to account these effects accurately (TF). The results from LEMLES, using a reduced chemical mechanism, have been analyzed in the premixed mode. The results show that mass entrainment occurs along the shear layer in the combustor. The entrained mass carries products into the reactant stream and provides reactant preheating. Thus, product entrainment enhances the reaction rates and help stabilize the flame even at very lean conditions. These products have been shown to enter into the flame through local extinction zones present on the flame surface. The flame structure has been further analyzed, and the combustion mode was found to be primarily in thin reaction zones. Closer to the injector, there are isolated regions, where the combustion mode is in broken reaction zones, while the downstream flame structure is closer to a flamelet regime. The emissions in the combustor have been studied using simple global mechanisms for NO x. Computations have shown extremely low NOx values, comparable to the measured emissions. These low emissions have been shown to be primarily due to the low temperatures in the combustor. LEMLES computations have also been performed with a detailed chemistry to capture more accurate flame structure. The flame in the detailed chemistry case shows more extinction zones close to the injector than that in the reduced chemical mechanism. The LEMLES approach has also been used to resolve the combustion mode in the non-premixed case. The studies have indicated that the mixing of the fuel and air close to the injector controls the combustion process. The predictions in the near field have been shown to be very sensitive to the inflow conditions. Analysis has shown that the fuel and air mixing occurs to lean proportions in the combustor before any burning takes place. The flame structure in the non-premixed mode was very similar to the premixed mode. Along with the fuel air mixing, the products also mixed with the reactants and provided the preheating effects to stabilize the flame in the downstream region of the combustor.

Flame tolerant secondary fuel nozzle

DOEpatents

Khan, Abdul Rafey; Ziminsky, Willy Steve; Wu, Chunyang; Zuo, Baifang; Stevenson, Christian Xavier

2015-02-24

A combustor for a gas turbine engine includes a plurality of primary nozzles configured to diffuse or premix fuel into an air flow through the combustor; and a secondary nozzle configured to premix fuel with the air flow. Each premixing nozzle includes a center body, at least one vane, a burner tube provided around the center body, at least two cooling passages, a fuel cooling passage to cool surfaces of the center body and the at least one vane, and an air cooling passage to cool a wall of the burner tube. The cooling passages prevent the walls of the center body, the vane(s), and the burner tube from overheating during flame holding events.

Study of Turbulent Premixed Flame Propagation using a Laminar Flamelet Model

NASA Technical Reports Server (NTRS)

Im, H. G.

1995-01-01

The laminar flamelet concept in turbulent reacting flows is considered applicable to many practical combustion systems (Linan & Williams 1993). For turbulent premixed combustion, the laminar flamelet regime is valid when turbulent Karlovitz number is less than unity, which is equivalent to stating that the characteristic thickness of the flame is less than that of a Kolmogorov eddy; this is known as the Klimov-Williams criterion (Williams 1985). In such a case, the flame maintains its laminar structure, and the effect of turbulent flow is merely to wrinkle and strain the flame front. The propagating wrinkled premixed flame can then be described as an infinitesimally thin surface dividing the unburnt fresh mixture and the burnt product.

Properties of calcium silicate-monobasic calcium phosphate materials for endodontics containing tantalum pentoxide and zirconium oxide.

PubMed

Zamparini, Fausto; Siboni, Francesco; Prati, Carlo; Taddei, Paola; Gandolfi, Maria Giovanna

2018-05-08

The aim of the study was to evaluate chemical-physical properties and apatite-forming ability of three premixed calcium silicate materials containing monobasic calcium phosphate (CaH 4 P 2 O 8 ) bioceramic, tantalum pentoxide and zirconium oxide, recently marketed for endodontics (TotalFill BC-Sealer, BC-RRM-Paste, BC-RRM-Putty). Microchemical and micromorphological analyses, radiopacity, initial and final setting times, calcium release and alkalising activity were tested. The nucleation of calcium phosphates (CaPs) and/or apatite after 28 days ageing was evaluated by ESEM-EDX and micro-Raman spectroscopy. BC-Sealer and BC-RRM-Paste showed similar initial (23 h), prolonged final (52 h) setting times and good radiopacity (> 7 mm Al); BC-RRM-Putty showed fast initial (2 h) and final setting times (27 h) and excellent radiopacity (> 9 mm Al). All materials induced a marked alkalisation (pH 11-12) up to 28 days and showed the release of calcium ions throughout the entire test period (cumulative calcium release 641-806 ppm). After 28 days ageing, a well-distributed mineral layer was present on all samples surface; EDX demonstrated relevant calcium and phosphorous peaks. B-type carbonated apatite and calcite deposits were identified by micro-Raman spectroscopy on all the 28-day-aged samples; the deposit thickness was higher on BC-RRM-Paste and BC-RRM-Putty, in agreement with calcium release data. These materials met the required chemical and physical standards and released biologically relevant ions. The CaSi-CaH 4 P 2 O 8 system present in the materials provided Ca and OH ions release with marked abilities to nucleate a layer of B-type carbonated apatite favoured/accelerated by the bioceramic presence. The ability to nucleate apatite may lead many clinical advantages: In orthograde endodontics, it may improve the sealing ability by the deposition of CaPs at the material-root dentine interface, and in endodontic surgery, it could promote bone and periodontal tissue regeneration. As premixed materials, their application in endodontics may result easier in several complex endodontic situations (apicoectomy, root perforation, presence of wide/wet apices).

THE EFFECTS OF EQUIVALENCE RATIO ON THE FORMATION OF POLYCYCLIC AROMATIC HYDROCARBONS AND SOOT IN PREMIXED ETHANE FLAMES. (R825412)

EPA Science Inventory

Abstract

The formation of polycyclic aromatic hydrocarbons (PAH) and soot has been investigated in atmospheric-pressure, laminar, ethane/oxygen/argon premixed flames as a function of mixture equivalence ratio. Mole fraction profiles of major products, trace aromatics, ...

Premixed Digestion Salts for Kjeldahl Determination of Total Nitrogen in Selected Forest Soils

Treesearch

B. G. Blackmon

1971-01-01

Estimates of total soil nitrogen by a standard Kjeldahl procedure and a modified procedure employing packets of premixed digestion salts were closely correlated. (r2 = 0.983). The modified procedure appears to be as reliable all the standard method for determining total nitrogen in southern alluvial forest soils.

AROMATIC AND POLYCYCLIC AROMATIC HYDROCARBON FORMATION IN A LAMINAR PREMIXED N-BUTANE FLAME. (R825412)

EPA Science Inventory

Abstract

Experimental and detailed chemical kinetic modeling work has been performed to investigate aromatic and polycyclic aromatic hydrocarbon (PAH) formation pathways in a premixed, rich, sooting, n-butane_¯oxygen_¯argon burner s...

21 CFR 170.60 - Nitrites and/or nitrates in curing premixes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Nitrites and/or nitrates in curing premixes. 170... guanylate, hydrolysates of animal or plant origin (such as hydrolyzed vegetable protein), oleoresins of... of an authorizing food additive regulation. A food additive petition submitted pursuant to §§ 171.1...

Gravitational Influences on Flame Propagation Through Non-Uniform, Premixed Gas Systems

NASA Technical Reports Server (NTRS)

Miller, Fletcher J.; Easton, John; Marchese, Anthony; Hovermann, Fred

2003-01-01

Flame propagation through non-uniformly premixed (or layered) gases has importance both in useful combustion systems and in unintentional fires. As summarized recently and in previous Microgravity Workshop papers, non-uniform premixed gas combustion receives scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames, especially regarding the role gravity plays. This paper summarizes our recent findings on gravitational effects on layered combustion along a floor, in which the fuel concentration gradient exists normal to the direction of flame spread. In an effort to understand the mechanism by which the flames spread faster in microgravity (and much faster, in laboratory coordinates, than the laminar burning velocity for uniform mixtures), we have begun making pressure measurements across the spreading flame front that are described here. Earlier researchers, testing in 1g, claimed that hydrostatic pressure differences could account for the rapid spread rates. Additionally, we present the development of a new apparatus to study flame spread in free (i.e., far from walls), non-homogeneous fuel layers formed in a flow tunnel behind an airfoil that has been tested in normal gravity.

Gravitational Influences on Flame Propagation through Non-Uniform, Premixed Gas Systems

NASA Technical Reports Server (NTRS)

Miller, Fletcher J.; Easton, John; Ross, Howard D.; Marchese, Anthony; Perry, David; Kulis, Michael

2001-01-01

Flame propagation through non-uniformly premixed (or layered) gases has importance both in useful combustion systems and in unintentional fires. As summarized previously, non-uniform premixed gas combustion receives scant attention compared to the more usual limiting cases of diffusion or uniformly premixed flames, especially regarding the role gravity plays. This paper summarizes our progress on furthering the knowledge of layered combustion, in which a fuel concentration gradient exists normal to the direction of flame spread. We present experimental and numerical results for flame spread through propanol-air layers formed near the flash point temperature (25 C) or near the stoichiometric temperature (33 C). Both the model and experimental results show that the removal of gravity results in a faster spreading flame, by as much as 80% depending on conditions. This is exactly the opposite effect as that predicted by an earlier model reported. We also found that having a gallery lid results in faster flame spread, an effect more pronounced at normal gravity, demonstrating the importance of enclosure geometry. Also reported here is the beginning of our spectroscopic measurements of fuel vapor.

The effect of stratification on premixed swirl-flame flashback by using porous center-body injection

NASA Astrophysics Data System (ADS)

McCaslin, Andrew; Ranjan, Rakesh; Clemens, Noel

2016-11-01

Boundary layer flashback must be prevented in order to stably operate stationary gas turbines. One strategy to avoid flashback is to create equivalence-ratio stratification, such as by reducing the fuel/air ratio in the boundary layer below the flammability limit. Typically, stratification is achieved by using radially non-uniform fuel injection. The goal of the current study is to reduce the propensity of flashback in a premixed annular swirl combustor that uses a premix section with center-body. A porous metal center-body (10 micron pore size) is used to bleed air directly into the boundary layer and thus locally reduce the equivalence ratio. Planar laser-induced fluorescence imaging of anisole-seeded flow is carried out to assess the stratification in the flow. Time-resolved PIV and chemiluminescence imaging are used to investigate flashback at atmospheric pressure conditions. A comparative study between fully premixed and stratified flame flashback is conducted to determine how stratification influences flashback physics. This work was sponsored by the DOE NETL under Grant DEFC2611-FE0007107. This source of funding is gratefully acknowledged.

Computations of turbulent lean premixed combustion using conditional moment closure

NASA Astrophysics Data System (ADS)

Amzin, Shokri; Swaminathan, Nedunchezhian

2013-12-01

Conditional Moment Closure (CMC) is a suitable method for predicting scalars such as carbon monoxide with slow chemical time scales in turbulent combustion. Although this method has been successfully applied to non-premixed combustion, its application to lean premixed combustion is rare. In this study the CMC method is used to compute piloted lean premixed combustion in a distributed combustion regime. The conditional scalar dissipation rate of the conditioning scalar, the progress variable, is closed using an algebraic model and turbulence is modelled using the standard k-ɛ model. The conditional mean reaction rate is closed using a first order CMC closure with the GRI-3.0 chemical mechanism to represent the chemical kinetics of methane oxidation. The PDF of the progress variable is obtained using a presumed shape with the Beta function. The computed results are compared with the experimental measurements and earlier computations using the transported PDF approach. The results show reasonable agreement with the experimental measurements and are consistent with the transported PDF computations. When the compounded effects of shear-turbulence and flame are strong, second order closures may be required for the CMC.

Direct numerical simulations of premixed autoignition in compressible uniformly-sheared turbulence

NASA Astrophysics Data System (ADS)

Towery, Colin; Darragh, Ryan; Poludnenko, Alexei; Hamlington, Peter

2017-11-01

High-speed combustion systems, such as scramjet engines, operate at high temperatures and pressures, extremely short combustor residence times, very high rates of shear stress, and intense turbulent mixing. As a result, the reacting flow can be premixed and have highly-compressible turbulence fluctuations. We investigate the effects of compressible turbulence on the ignition delay time, heat-release-rate (HRR) intermittency, and mode of autoignition of premixed Hydrogen-air fuel in uniformly-sheared turbulence using new three-dimensional direct numerical simulations with a multi-step chemistry mechanism. We analyze autoignition in both the Eulerian and Lagrangian reference frames at eight different turbulence Mach numbers, Mat , spanning the quasi-isentropic, linear thermodynamic, and nonlinear compressibility regimes, with eddy shocklets appearing in the nonlinear regime. Results are compared to our previous study of premixed autoignition in isotropic turbulence at the same Mat and with a single-step reaction mechanism. This previous study found large decreases in delay times and large increases in HRR intermittency between the linear and nonlinear compressibility regimes and that detonation waves could form in both regimes.

Optimization of instant dalia dessert pre-mix production by using response surface methodology.

PubMed

Jha, Alok; Shalini, B N; Patel, Ashok Ambalal; Singh, Mithilesh; Rasane, Prasad

2015-02-01

Dalia, a wheat-based, particulate containing dairy dessert is popularly consumed as a breakfast food and is also considered as a health food. Though popular throughout Northern parts of the country, its limited shelf-life even under refrigeration imposes severe restrictions on its organized manufacture and marketing. In order to promote dalia dessert as a marketable product, in the present study, a process was developed for manufacture of instant dalia pre-mix, as a dry product with long shelf-life, which could be attractively packaged and easily reconstituted for consumption. During the investigation, the effect of different levels of milk solids and wheat solids was studied on dalia pre-mix quality by employing a central composite rotatable design (CCRD). The suggested formulation had 17.82 % milk solids and 2.87 % wheat solids. This formulation was found to be most appropriate for manufacture of instant dalia pre-mix with predicted sensory scores (Max. 100) of 85.35, 41.98 and 67.27 for mouthfeel, consistency and flavor, respectively; the viscosity of the product was 941.0 cp.

Spectral kinetic energy transfer in turbulent premixed reacting flows.

PubMed

Towery, C A Z; Poludnenko, A Y; Urzay, J; O'Brien, J; Ihme, M; Hamlington, P E

2016-05-01

Spectral kinetic energy transfer by advective processes in turbulent premixed reacting flows is examined using data from a direct numerical simulation of a statistically planar turbulent premixed flame. Two-dimensional turbulence kinetic-energy spectra conditioned on the planar-averaged reactant mass fraction are computed through the flame brush and variations in the spectra are connected to terms in the spectral kinetic energy transport equation. Conditional kinetic energy spectra show that turbulent small-scale motions are suppressed in the burnt combustion products, while the energy content of the mean flow increases. An analysis of spectral kinetic energy transfer further indicates that, contrary to the net down-scale transfer of energy found in the unburnt reactants, advective processes transfer energy from small to large scales in the flame brush close to the products. Triadic interactions calculated through the flame brush show that this net up-scale transfer of energy occurs primarily at spatial scales near the laminar flame thermal width. The present results thus indicate that advective processes in premixed reacting flows contribute to energy backscatter near the scale of the flame.

The route of liquid precursor to ZnO nanoparticles in premixed combustion spray pyrolysis

NASA Astrophysics Data System (ADS)

Widiyastuti, W.; Machmudah, Siti; Nurtono, Tantular; Winardi, Sugeng

2018-04-01

Zinc oxide nanoparticles had been successfully synthesized by premixed combustion spray pyrolysis. Zinc acetate was dissolved in distilled water was selected as a liquid precursor. Zinc nitrate was also used for comparison the effect of precursor type on the generated particles morphology and the crystallinity. The premixed combustion reaction used liquefied petroleum gas (LPG) mainly consisting of butane and propane as a fuel and compressed air used as an oxidizer. The liquid precursor was atomized using a custom two fluid nozzle to generate droplets. Then, the droplets were sprayed by the flow of air as a carrier gas into the premixed combustion reactor. The zinc precursor was decomposed to zinc oxide due to the high temperature as a result of combustion reaction inside the reactor resulting in nanoparticles formation. The particle size decreased with the increase of the fuel flow rate. In addition, it can be found that at the same flow rate of fuel, the particle size of zinc oxide synthesized using zinc nitrate is larger than that of the use of zinc acetate as a precursor.

Analgesic efficacy of equimolar 50% nitrous oxide/oxygen gas premix (Kalinox®) as compared with a 5% eutectic mixture of lidocaine/prilocaine (EMLA®) in chronic leg ulcer debridement.

PubMed

Traber, Juerg; Held, Ulrike; Signer, Maria; Huebner, Tobias; Arndt, Stefan; Neff, Thomas A

2017-08-01

Chronic foot and leg ulcers are a common health problem worldwide. A mainstay of chronic ulcer therapy is sharp mechanical wound debridement requiring potent analgesia. In this prospective, controlled, single-centre, crossover design study, patients were assigned to either the administration of topical analgesia with 5% lidocaine/prilocaine cream or the inhalation of an analgesic 50% N 2 O/O 2 gas premix. Primary outcome parameter was level of pain at maximum wound depth during debridement as measured by a visual analogue scale. Secondary outcomes included level of pain after debridement, overall duration of treatment session, duration and completeness of debridement, and the patient's subjective perception of analgesic quality during debridement. Pain level increased from 0·60/0·94 (first/second debridement; baseline) to 1·76/2·50 (debridement) with 5% lidocaine/prilocaine and from 1·00/1·35 (baseline) to 3·95/3·29 (debridement) with 50% N 2 O/O 2 gas premix. Patient satisfaction was 90·48%/94·44% (first/second debridement) with topical 5% lidocaine/prilocaine analgesia and 90·48%/76·47% with the inhalation of 50% N 2 O/O 2 gas premix. Debridement was completed in a significantly higher percentage of 85·71%/88·89% (first/second debridement) with 5% lidocaine/prilocaine than with 50% N 2 O/O 2 gas premix (42·86%/58·82%) (odds ratio 6·7; P = 0·001). This study provides sound evidence that analgesia with topically administered 5% lidocaine/prilocaine cream is superior to the use of inhaled 50% N 2 O/O 2 gas premix in chronic leg ulcer debridement. © 2016 Medicalhelplines.com Inc and John Wiley & Sons Ltd.

Criteria Development for Gas Turbine Premixer Flameholding Tendencies of Natural Gas and High Hydrogen Content Fuels

NASA Astrophysics Data System (ADS)

Sullivan-Lewis, Elliot Gregory

Due to increasingly stringent air quality requirements, stationary power gas turbines have moved to lean-premixed operation, which reduces pollutant emissions but can result in flashback. Flashback can cause serious damage to the premixer hardware. Curtailing flashback can be difficult with hydrocarbon fuels and becomes even more challenging when the fuel contains hydrogen. The two main approaches for coping with flashback are either to design a combustor that is resistant to flashback, or to design a premixer that will not anchor a flame if flashback occurs. Even with a well-designed combustor, flashback can occur under certain circumstances. Thus it is necessary to determine how to avoid flameholding within the premixer passageways of a gas turbine. To this end, an experiment was designed that would determine the flameholding propensities at elevated pressures and temperatures of three different classes of geometric features commonly found in gas turbine premixers, with both natural gas and hydrogen containing fuel. Experiments to find the equivalence ratio at blow off were conducted within an optically accessible test apparatus with four flameholders: 0.25 and 0.50 inch diameter cylinders, a reverse facing step with a height of 0.25 inches, and a symmetric airfoil with a thickness of 0.25 inches and a chord length of one inch. Tests were carried out at temperatures between 300 K and 750 K, at pressures up to 9 atmospheres. Typical bulk velocities were between 40 and 100 m/s. The effect of the airfoil's angle of rotation was also investigated. Blow off for hydrogen reactions was found to occur at much lower adiabatic flame temperatures than natural gas reactions. Additionally it was observed that at high pressures and high turbulence intensities, reactant velocity does not have a noticeable effect on the point of blow off due in large part to corresponding increases in turbulent flame speed. Finally a semi empirical correlation was developed that predicts flame extinction for both natural gas and hydrogen containing reactions.

Pumpable rockbolt method

DOEpatents

Steinberg, Meyer; Manowitz, Bernard; Waide, Charles H.

1976-01-06

Method and apparatus for producing rockbolts in the roof of a subterranean cavity in which two components of an ambient temperature curable resin system are premixed and then inserted into a bore hole. The mixture is permitted to polymerize in situ and then the hardened material is cut off at the entrance to the hole leaving a hardened portion for insertion into the next hole as a precursor. In a preferred embodiment a flexible glass roving is employed to reinforce the material in the hole and a metal tube inserted to support the roving while it is fed into the hole and also to provide venting. The roving and tube is then cut off and left in the hole.

Effect of dietary canthaxanthin and 25-hydroxycholecalciferol supplementation on the performance of duck breeders under two different vitamin regimens.

PubMed

Ren, Zhouzheng; Jiang, Shizhen; Zeng, Qiufeng; Ding, Xuemei; Bai, Shiping; Wang, Jianping; Luo, Yuheng; Su, Zhuowei; Xuan, Yue; Yao, Bing; Cisneros, Fernando; Zhang, Keying

2016-01-01

Dietary canthaxanthin (CX), 25-hydroxycholecalciferol (25-OH-D 3 ) and vitamins have been widely reported to be involved in productive and reproductive performance of broiler breeders. However, limited information is available for duck breeders. In this study, a total of 1,560 Cherry Valley SM3 duck breeder females and 312 males were used to assess if the addition of CX and 25-OH-D3 could increase the performance of duck breeders under two different dietary vitamin regimens. Four diets were used under a 2 × 2 factorial arrangement with 2 kinds of vitamin premixes (REGULAR and HIGH; HIGH premix had higher levels of all vitamins except K3 than REGULAR premix), and with or without the supplementation of the mixture of CX (6 mg/kg) and 25-OH-D3 (0.069 mg/kg). The ducks were fed ad libitum with pelleted diets based on corn-soybean meal from 38 to 77 wk of age. HIGH vitamin premix decreased malondialdehyde (MDA) level (P < 0.001) of egg yolk, increased hatchability of fertile eggs (P = 0.029), increased hatchability of total eggs (P = 0.029), and decreased serum protein carbonyl level (P = 0.037) of breeder males. The mixture of CX and 25-OH-D3 increased serum calcium of breeder females (P = 0.010), decreased the cracked egg rate (P = 0.001), increased the pigmentation of egg yolk (P < 0.001) and male bill (P < 0.001), and decreased MDA level of egg yolk (P < 0.001) and male serum (P = 0.034). Interactive effects were observed in cracked egg rate (P = 0.038), shell thickness (P = 0.011) and serum phosphorus (P = 0.026) of breeder females. HIGH vitamin premix together with the mixture of CX and 25-OH-D3 decreased cracked egg rate and increased shell thickness of duck breeders. Serum phosphorus was decreased in duck breeder females fed REGULAR vitamin premix without the addition of the CX and 25-OH-D3 mixture. Dietary HIGH vitamin premix increased antioxidant status of eggs and breeder males, and increased hatchability. The mixture of CX and 25-OH-D3 enhanced egg shell quality, and promoted pigmentation and antioxidant status of eggs and breeder males.

X-ray radiography for container inspection

DOEpatents

Katz, Jonathan I [Clayton, MO; Morris, Christopher L [Los Alamos, NM

2011-06-07

Arrangements of X-ray inspection systems are described for inspecting high-z materials in voluminous objects such as containers. Inspection methods may involve generating a radiographic image based on detected attenuation corresponding to a pulsed beams of radiation transmitted through a voluminous object. The pulsed beams of radiation are generated by a high-energy source and transmitted substantially downward along an incident angle, of approximately 1.degree. to 30.degree., to a vertical axis extending through the voluminous object. The generated radiographic image may be analyzed to detect on localized high attenuation representative of high-z materials and to discriminate high-z materials from lower and intermediate-z materials on the basis of the high density and greater attenuation of high-z material for higher energy (3-10 MeV) X-rays, and the compact nature of threatening masses of fissionable materials.

Angelica sinensis (Oliv.) Diels: Influence of Value Chain on Quality Criteria and Marker Compounds Ferulic Acid and Z-Ligustilide.

PubMed

Giacomelli, Nino; Yongping, Yang; Huber, Franz K; Ankli, Anita; Weckerle, Caroline S

2017-03-14

Background: Dang gui (Apiaceae; Angelica sinensis radix) is among the most often used Chinese medicinal plants. However, hardly anything is known about its value chain and its influence on the main marker compounds of the drug. The aim of this study is to investigate the value chain of dang gui in Gansu and Yunnan, and the analysis of the marker compounds ferulic acid and Z-ligustilide concentration in relation to quality criteria such as the production area and size of the roots. Methods: During six months of field research in China, semi-structured interviews with various stakeholders of the value chain were undertaken and plant material was collected. High-performance thin layer chromatography (HPTLC) was used for semi-quantitative analysis of ferulic acid and Z-ligustilide. Results: Small-scale household cultivation prevails and in Gansu-in contrast to Yunnan-the cultivation of dang gui is often the main income source of farmers. Farmers and dealers use size and odor of the root as main quality criteria. For Chinese medicine doctors, Gansu as the production area is the main criterion. Higher amounts of ferulic acid in plant material from Yunnan compared to Gansu were found. Additionally, a negative relation of root length with both ferulic acid and Z-ligustilide as well as head diameter with ferulic acid were found. Conclusions: HPTLC is a valid method for semi-quantitative analysis of the marker compounds of dang gui . However, the two main marker compounds cannot explain why size and smell of the root or production area are seen as quality criteria. This hints at the inherent difficulty to correlate quality notions of medicinal plants with specific chemical compounds. With respect to this, more attention should be paid to quality in terms of cultivation and processing techniques.

EFFECTS OF EQUIVALENCE RATIO ON SPECIES AND SOOT CONCENTRATIONS IN PREMIXED N-HEPTANE FLAMES. (R828193)

EPA Science Inventory

The micro-structure of laminar premixed, atmospheric-pressure, fuel-rich flames of n-heptane/oxygen/argon has been studied at two equivalence ratios (C/O = 0.63 and C/O = 0.67). A heated quartz microprobe coupled to an online gas chromatography/mass spectrometry (HP 5890 Serie...

Statistics of premixed flame cells

NASA Technical Reports Server (NTRS)

Noever, David A.

1991-01-01

The statistics of random cellular patterns in premixed flames are analyzed. Agreement is found with a variety of topological relations previously found for other networks, namely, Lewis's law and Aboav's law. Despite the diverse underlying physics, flame cells are shown to share a broad class of geometric properties with other random networks-metal grains, soap foams, bioconvection, and Langmuir monolayers.

Management of Type 2 diabetes in Ramadan: Low-ratio premix insulin working group practical advice

PubMed Central

Hassanein, Mohamed; Belhadj, Mohamed; Abdallah, Khalifa; Bhattacharya, Arpan D.; Singh, Awadhesh K.; Tayeb, Khaled; Al-Arouj, Monira; Elghweiry, Awad; Iraqi, Hinde; Nazeer, Mohamed; Jamoussi, Henda; Mnif, Mouna; Al-Madani, Abdulrazzaq; Al-Ali, Hossam; Ligthelm, Robert

2014-01-01

The challenge of insulin use during Ramadan could be minimized, if people with diabetes are metabolically stable and are provided with structured education for at least 2–3 months pre-Ramadan. Although, American diabetes association (ADA) recommendations 2010 and South Asian Consensus Guideline 2012 deal with management of diabetes in Ramadan and changes in insulin dosage, no specific guidance on widely prescribed low-ratio premix insulin is currently available. Hence, the working group for insulin therapy in Ramadan, after collective analysis, evaluation, and opinion from clinical practice, have formulated a practical advice to empower physicians with pre-Ramadan preparation, dose adjustment, and treatment algorithm for self-titration of low-ratio premix insulin. PMID:25364673

Planar SiC MEMS flame ionization sensor for in-engine monitoring

NASA Astrophysics Data System (ADS)

Rolfe, D. A.; Wodin-Schwartz, S.; Alonso, R.; Pisano, A. P.

2013-12-01

A novel planar silicon carbide (SiC) MEMS flame ionization sensor was developed, fabricated and tested to measure the presence of a flame from the surface of an engine or other cooled surface while withstanding the high temperature and soot of a combustion environment. Silicon carbide, a ceramic semiconductor, was chosen as the sensor material because it has low surface energy and excellent mechanical and electrical properties at high temperatures. The sensor measures the conductivity of scattered charge carriers in the flame's quenching layer. This allows for flame detection, even when the sensor is situated several millimetres from the flame region. The sensor has been shown to detect the ionization of premixed methane and butane flames in a wide temperature range starting from room temperature. The sensors can measure both the flame chemi-ionization and the deposition of water vapour on the sensor surface. The width and speed of a premixed methane laminar flame front were measured with a series of two sensors fabricated on a single die. This research points to the feasibility of using either single sensors or arrays in internal combustion engine cylinders to optimize engine performance, or for using sensors to monitor flame stability in gas turbine applications.

Outbreak of Mycobacterium chelonae infection associated with tattoo ink.

PubMed

Kennedy, Byron S; Bedard, Brenden; Younge, Mary; Tuttle, Deborah; Ammerman, Eric; Ricci, John; Doniger, Andrew S; Escuyer, Vincent E; Mitchell, Kara; Noble-Wang, Judith A; O'Connell, Heather A; Lanier, William A; Katz, Linda M; Betts, Robert F; Mercurio, Mary Gail; Scott, Glynis A; Lewis, Matthew A; Goldgeier, Mark H

2012-09-13

In January 2012, on the basis of an initial report from a dermatologist, we began to investigate an outbreak of tattoo-associated Mycobacterium chelonae skin and soft-tissue infections in Rochester, New York. The main goals were to identify the extent, cause, and form of transmission of the outbreak and to prevent further cases of infection. We analyzed data from structured interviews with the patients, histopathological testing of skin-biopsy specimens, acid-fast bacilli smears, and microbial cultures and antimicrobial susceptibility testing. We also performed DNA sequencing, pulsed-field gel electrophoresis (PFGE), cultures of the ink and ingredients used in the preparation and packaging of the ink, assessment of source water and faucets at tattoo parlors, and investigation of the ink manufacturer. Between October and December 2011, a persistent, raised, erythematous rash in the tattoo area developed in 19 persons (13 men and 6 women) within 3 weeks after they received a tattoo from a single artist who used premixed gray ink; the highest occurrence of tattooing and rash onset was in November (accounting for 15 and 12 patients, respectively). The average age of the patients was 35 years (range, 18 to 48). Skin-biopsy specimens, obtained from 17 patients, showed abnormalities in all 17, with M. chelonae isolated from 14 and confirmed by means of DNA sequencing. PFGE analysis showed indistinguishable patterns in 11 clinical isolates and one of three unopened bottles of premixed ink. Eighteen of the 19 patients were treated with appropriate antibiotics, and their condition improved. The premixed ink was the common source of infection in this outbreak. These findings led to a recall by the manufacturer.

Direct numerical simulations of a high Karlovitz number laboratory premixed jet flame – an analysis of flame stretch and flame thickening [Direct numerical simulations of a high Ka laboratory premixed jet flame - an analysis of flame stretch and flame thickening

DOE PAGES

Wang, Haiou; Hawkes, Evatt R.; Chen, Jacqueline H.; ...

2017-02-23

This article reports an analysis of the first detailed chemistry direct numerical simulation (DNS) of a high Karlovitz number laboratory premixed flame. The DNS results are first compared with those from laser-based diagnostics with good agreement. The subsequent analysis focuses on a detailed investigation of the flame area, its local thickness and their rates of change in isosurface following reference frames, quantities that are intimately connected. The net flame stretch is demonstrated to be a small residual of large competing terms: the positive tangential strain term and the negative curvature stretch term. The latter is found to be driven bymore » flame speed–curvature correlations and dominated in net by low probability highly curved regions. Flame thickening is demonstrated to be substantial on average, while local regions of flame thinning are also observed. The rate of change of the flame thickness (as measured by the scalar gradient magnitude) is demonstrated, analogously to flame stretch, to be a competition between straining tending to increase gradients and flame speed variations in the normal direction tending to decrease them. The flame stretch and flame thickness analyses are connected by the observation that high positive tangential strain rate regions generally correspond with low curvature regions; these regions tend to be positively stretched in net and are relatively thinner compared with other regions. Finally, high curvature magnitude regions (both positive and negative) generally correspond with lower tangential strain; these regions are in net negatively stretched and thickened substantially.« less

Direct numerical simulations of a high Karlovitz number laboratory premixed jet flame – an analysis of flame stretch and flame thickening [Direct numerical simulations of a high Ka laboratory premixed jet flame - an analysis of flame stretch and flame thickening

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

Wang, Haiou; Hawkes, Evatt R.; Chen, Jacqueline H.

This article reports an analysis of the first detailed chemistry direct numerical simulation (DNS) of a high Karlovitz number laboratory premixed flame. The DNS results are first compared with those from laser-based diagnostics with good agreement. The subsequent analysis focuses on a detailed investigation of the flame area, its local thickness and their rates of change in isosurface following reference frames, quantities that are intimately connected. The net flame stretch is demonstrated to be a small residual of large competing terms: the positive tangential strain term and the negative curvature stretch term. The latter is found to be driven bymore » flame speed–curvature correlations and dominated in net by low probability highly curved regions. Flame thickening is demonstrated to be substantial on average, while local regions of flame thinning are also observed. The rate of change of the flame thickness (as measured by the scalar gradient magnitude) is demonstrated, analogously to flame stretch, to be a competition between straining tending to increase gradients and flame speed variations in the normal direction tending to decrease them. The flame stretch and flame thickness analyses are connected by the observation that high positive tangential strain rate regions generally correspond with low curvature regions; these regions tend to be positively stretched in net and are relatively thinner compared with other regions. Finally, high curvature magnitude regions (both positive and negative) generally correspond with lower tangential strain; these regions are in net negatively stretched and thickened substantially.« less

The evolution equation for the flame surface density in turbulent premixed combustion

NASA Technical Reports Server (NTRS)

Trouve, A.; Poinsot, T.

1992-01-01

One central ingredient in flamelet models for turbulent premixed combustion is the flame surface density. This quantity conveys most of the effects of the turbulence on the rate of energy release and is obtained via a modeled transport equation, called the Sigma-equation. Past theoretical work has produced a rigorous approach that leads to an exact, but unclosed, formulation for the turbulent Sigma-equation. In this exact Sigma-equation, it appears that the dynamical properties of the flame surface density are determined by a single parameter, namely the turbulent flame stretch. Unfortunately, the flame surface density and the turbulent flame stretch are not available from experiments and, in the absence of experimental data, little is known on the validity of the closure assumptions used in current flamelet models. Direct Numerical Simulation (DNS) is the obvious, complementary approach to get basic information on these fundamental quantities. Three-dimensional DNS of premixed flames in isotropic turbulent flow is used to estimate the different terms appearing in the Sigma-equation. A new methodology is proposed to provide the source and sink terms for the flame surface density, resolved both temporally and spatially throughout the turbulent flame brush. Using this methodology, the effects of the Lewis number on the rate of production of flame surface area are described in great detail and meaningful comparisons with flamelet models can be performed. The analysis reveals in particular the tendency of the models to overpredict flame surface dissipation as well as their inability to reproduce variations due to thermo-diffusive phenomena. Thanks to the detailed information produced by a DNS-based analysis, this type of comparison not only underscores the shortcomings of current models but also suggests ways to improve them.

Heat release and flame structure measurements of self-excited acoustically-driven premixed methane flames

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

Kopp-Vaughan, Kristin M.; Tuttle, Steven G.; Renfro, Michael W.

An open-open organ pipe burner (Rijke tube) with a bluff-body ring was used to create a self-excited, acoustically-driven, premixed methane-air conical flame, with equivalence ratios ranging from 0.85 to 1.05. The feed tube velocities corresponded to Re = 1780-4450. Coupled oscillations in pressure, velocity, and heat release from the flame are naturally encouraged at resonant frequencies in the Rijke tube combustor. This coupling creates sustainable self-excited oscillations in flame front area and shape. The period of the oscillations occur at the resonant frequency of the combustion chamber when the flame is placed {proportional_to}1/4 of the distance from the bottom ofmore » the tube. In this investigation, the shape of these acoustically-driven flames is measured by employing both OH planar laser-induced fluorescence (PLIF) and chemiluminescence imaging and the images are correlated to simultaneously measured pressure in the combustor. Past research on acoustically perturbed flames has focused on qualitative flame area and heat release relationships under imposed velocity perturbations at imposed frequencies. This study reports quantitative empirical fits with respect to pressure or phase angle in a self-generated pressure oscillation. The OH-PLIF images were single temporal shots and the chemiluminescence images were phase averaged on chip, such that 15 exposures were used to create one image. Thus, both measurements were time resolved during the flame oscillation. Phase-resolved area and heat release variations throughout the pressure oscillation were computed. A relation between flame area and the phase angle before the pressure maximum was derived for all flames in order to quantitatively show that the Rayleigh criterion was satisfied in the combustor. Qualitative trends in oscillating flame area were found with respect to feed tube flow rates. A logarithmic relation was found between the RMS pressure and both the normalized average area and heat release rate for all flames. (author)« less

The dynamics of turbulent premixed flames: Mechanisms and models for turbulence-flame interaction

NASA Astrophysics Data System (ADS)

Steinberg, Adam M.

The use of turbulent premixed combustion in engines has been garnering renewed interest due to its potential to reduce NOx emissions. However there are many aspects of turbulence-flame interaction that must be better understood before such flames can be accurately modeled. The focus of this dissertation is to develop an improved understanding for the manner in which turbulence interacts with a premixed flame in the 'thin flamelet regime'. To do so, two new diagnostics were developed and employed in a turbulent slot Bunsen flame. These diagnostics, Cinema-Stereoscopic Particle Image Velocimetry and Orthogonal-Plane Cinema-Stereoscopic Particle Image Velocimetry, provided temporally resolved velocity and flame surface measurements in two- and three-dimensions with rates of up to 3 kHz and spatial resolutions as low as 280 mum. Using these measurements, the mechanisms with which turbulence generates flame surface area were studied. It was found that the previous concept that flame stretch is characterized by counter-rotating vortex pairs does not accurately describe real turbulence-flame interactions. Analysis of the experimental data showed that the straining of the flame surface is determined by coherent structures of fluid dynamic strain rate, while the wrinkling is caused by vortical structures. Furthermore, it was shown that the canonical vortex pair configuration is not an accurate reflection of the real interaction geometry. Hence, models developed based on this geometry are unlikely to be accurate. Previous models for the strain rate, curvature stretch rate, and turbulent burning velocity were evaluated. It was found that the previous models did not accurately predict the measured data for a variety of reasons: the assumed interaction geometries did not encompass enough possibilities to describe the possible effects of real turbulence, the turbulence was not properly characterized, and the transport of flame surface area was not always considered. New models therefore were developed that accurately reflect real turbulence-flame interactions and agree with the measured data. These can be implemented in Large Eddy Simulations to provide improved modeling of turbulence-flame interaction.

A new tissue segmentation method to calculate 3D dose in small animal radiation therapy.

PubMed

Noblet, C; Delpon, G; Supiot, S; Potiron, V; Paris, F; Chiavassa, S

2018-02-26

In pre-clinical animal experiments, radiation delivery is usually delivered with kV photon beams, in contrast to the MV beams used in clinical irradiation, because of the small size of the animals. At this medium energy range, however, the contribution of the photoelectric effect to absorbed dose is significant. Accurate dose calculation therefore requires a more detailed tissue definition because both density (ρ) and elemental composition (Z eff ) affect the dose distribution. Moreover, when applied to cone beam CT (CBCT) acquisitions, the stoichiometric calibration of HU becomes inefficient as it is designed for highly collimated fan beam CT acquisitions. In this study, we propose an automatic tissue segmentation method of CBCT imaging that assigns both density (ρ) and elemental composition (Z eff ) in small animal dose calculation. The method is based on the relationship found between CBCT number and ρ*Z eff product computed from known materials. Monte Carlo calculations were performed to evaluate the impact of ρZ eff variation on the absorbed dose in tissues. These results led to the creation of a tissue database composed of artificial tissues interpolated from tissue values published by the ICRU. The ρZ eff method was validated by measuring transmitted doses through tissue substitute cylinders and a mouse with EBT3 film. Measurements were compared to the results of the Monte Carlo calculations. The study of the impact of ρZ eff variation over the range of materials, from ρZ eff  = 2 g.cm - 3 (lung) to 27 g.cm - 3 (cortical bone) led to the creation of 125 artificial tissues. For tissue substitute cylinders, the use of ρZ eff method led to maximal and average relative differences between the Monte Carlo results and the EBT3 measurements of 3.6% and 1.6%. Equivalent comparison for the mouse gave maximal and average relative differences of 4.4% and 1.2%, inside the 80% isodose area. Gamma analysis led to a 94.9% success rate in the 10% isodose area with 4% and 0.3 mm criteria in dose and distance. Our new tissue segmentation method was developed for 40kVp CBCT images. Both density and elemental composition are assigned to each voxel by using a relationship between HU and the product ρZ eff . The method, validated by comparing measurements and calculations, enables more accurate small animal dose distribution calculated on low energy CBCT images.

High-capacity nanostructured germanium-containing materials and lithium alloys thereof

DOEpatents

Graetz, Jason A.; Fultz, Brent T.; Ahn, Channing; Yazami, Rachid

2010-08-24

Electrodes comprising an alkali metal, for example, lithium, alloyed with nanostructured materials of formula Si.sub.zGe.sub.(z-1), where 0

Gravity Effects Observed In Partially Premixed Flames

NASA Technical Reports Server (NTRS)

Puri, Ishwar K.; Aggarwal, Suresh K.; Lock, Andrew J.; Gauguly, Ranjan; Hegde, Uday

2003-01-01

Partially premixed flames (PPFs) contain a rich premixed fuel air mixture in a pocket or stream, and, for complete combustion to occur, they require the transport of oxidizer from an appropriately oxidizer-rich (or fuel-lean) mixture that is present in another pocket or stream. Partial oxidation reactions occur in fuel-rich portions of the mixture and any remaining unburned fuel and/or intermediate species are consumed in the oxidizer-rich portions. Partial premixing, therefore, represents that condition when the equivalence ratio (phi) in one portion of the flowfield is greater than unity, and in another section its value is less than unity. In general, for combustion to occur efficiently, the global equivalence ratio is in the range fuel-lean to stoichiometric. These flames can be established by design by placing a fuel-rich mixture in contact with a fuel-lean mixture, but they also occur otherwise in many practical systems, which include nonpremixed lifted flames, turbulent nonpremixed combustion, spray flames, and unwanted fires. Other practical applications of PPFs are reported elsewhere. Although extensive experimental studies have been conducted on premixed and nonpremixed flames under microgravity, there is a absence of previous experimental work on burner stabilized PPFs in this regard. Previous numerical studies by our group employing a detailed numerical model showed gravity effects to be significant on the PPF structure. We report on the results of microgravity experiments conducted on two-dimensional (established on a Wolfhard-Parker slot burner) and axisymmetric flames (on a coannular burner) that were investigated in a self-contained multipurpose rig. Thermocouple and radiometer data were also used to characterize the thermal transport in the flame.

The global, centralized approach of the GAIN Premix Facility has made oil fortification in Indonesia more affordable.

PubMed

Jallier, Vincent; Guyondet, Christophe; Provent, Adeline; Laillou, Arnaud; Soekirman; Moench-Pfanner, Regina

2013-06-01

Access to high-grade micronutrients is a recurring challenge that often threatens the long-term sustainability of food fortification programs. To assess the efficiency of the Global Alliance for Improved Nutrition (GAIN) Premix Facility in procuring quality, affordable vitamin A for fortification of edible oil in Indonesia. A global approach to procurement of standard items was used by combining volumes across various demand streams in order to reduce the total cost of acquisition through economies of scale. The GAIN Premix Facility undertook a detailed analysis of vitamin A requirements across its existing customer base, which served as a basis for developing a reliable demand forecast. A consolidated, competitive tender was launched that resulted in the setting up of a long-term commercial agreement with the selected supplier to lock in the most competitive price for a given period of time. The direct benefit to oil manufacturers of fortifying with vitamin A is that the cost of fortification went down significantly compared with prices they would have been offered had they ordered vitamin A individually. In Indonesia, this consolidated procurement approach has allowed a 14.5% decrease in the unit price of vitamin A. The GAIN Premix Facility demonstrated its effectiveness in acting as a global procurement platform by aggregating demand across different customers and leveraging improved prices through increased volumes. Building on the success of this effort, the GAIN Premix Facility is replicating this global approach for procurement of other standard items being procured across fortification programs worldwide.

Combustor with two stage primary fuel assembly

DOEpatents

Sharifi, Mehran; Zolyomi, Wendel; Whidden, Graydon Lane

2000-01-01

A combustor for a gas turbine having first and second passages for pre-mixing primary fuel and air supplied to a primary combustion zone. The flow of fuel to the first and second pre-mixing passages is separately regulated using a single annular fuel distribution ring having first and second row of fuel discharge ports. The interior portion of the fuel distribution ring is divided by a baffle into first and second fuel distribution manifolds and is located upstream of the inlets to the two pre-mixing passages. The annular fuel distribution ring is supplied with fuel by an annular fuel supply manifold, the interior portion of which is divided by a baffle into first and second fuel supply manifolds. A first flow of fuel is regulated by a first control valve and directed to the first fuel supply manifold, from which the fuel is distributed to first fuel supply tubes that direct it to the first fuel distribution manifold. From the first fuel distribution manifold, the first flow of fuel is distributed to the first row of fuel discharge ports, which direct it into the first pre-mixing passage. A second flow of fuel is regulated by a second control valve and directed to the second fuel supply manifold, from which the fuel is distributed to second fuel supply tubes that direct it to the second fuel distribution manifold. From the second fuel distribution manifold, the second flow of fuel is distributed to the second row of fuel discharge ports, which direct it into the second pre-mixing passage.

New Non-Intrusive Inspection Technologies for Nuclear Security and Nonproliferation

NASA Astrophysics Data System (ADS)

Ledoux, Robert J.

2015-10-01

Comprehensive monitoring of the supply chain for nuclear materials has historically been hampered by non-intrusive inspection systems that have such large false alarm rates that they are impractical in the flow of commerce. Passport Systems, Inc. (Passport) has developed an active interrogation system which detects fissionable material, high Z material, and other contraband in land, sea and air cargo. Passport's design utilizes several detection modalities including high resolution imaging, passive radiation detection, effective-Z (EZ-3D™) anomaly detection, Prompt Neutrons from Photofission (PNPF), and Nuclear Resonance Fluorescence (NRF) isotopic identification. These technologies combine to: detect fissionable, high-Z, radioactive and contraband materials, differentiate fissionable materials from high-Z shielding materials, and isotopically identify actinides, Special Nuclear Materials (SNM), and other contraband (e.g. explosives, drugs, nerve agents). Passport's system generates a 3-D image of the scanned object which contains information such as effective-Z and density, as well as a 2-D image and isotopic and fissionable information for regions of interest.

Ultrastructure of myocardial widened Z bands and endocardial cells in two teleostean species.

PubMed

Leknes, I L

1981-01-01

Widened myocardial Z bands and endocardial cells are described in two teleostean species Cichlasoma meeki and Corydoras aeneus. Widened Z bands containing mainly amorphous and electron-dense material were seen in a number of myocardial cells. Further, similar material may occur in large amounts beneath the sarcolemma and at intercellular junctions. Occasionally, we observed continuity between the latter material and that in expanded Z bands. In C. meeki the ventricular endocardial layer consists of two structurally different cell types, whereas in C. aeneus only one cell type was seen. The functional aspects of widened Z bands are discussed.

Direct Numerical Simulation of a Cavity-Stabilized Ethylene/Air Premixed Flame

NASA Astrophysics Data System (ADS)

Chen, Jacqueline; Konduri, Aditya; Kolla, Hemanth; Rauch, Andreas; Chelliah, Harsha

2016-11-01

Cavity flame holders have been shown to be important for flame stabilization in scramjet combustors. In the present study the stabilization of a lean premixed ethylene/air flame in a rectangular cavity at thermo-chemical conditions relevant to scramjet combustors is simulated using a compressible reacting multi-block direct numerical simulation solver, S3D, incorporating a 22 species ethylene-air reduced chemical model. The fuel is premixed with air to an equivalence ratio of 0.4 and enters the computational domain at Mach numbers between 0.3 and 0.6. An auxiliary inert channel flow simulation is used to provide the turbulent velocity profile at the inlet for the reacting flow simulation. The detailed interaction between intense turbulence, nonequilibrium concentrations of radical species formed in the cavity and mixing with the premixed main stream under density variations due to heat release rate and compressibility effects is quantified. The mechanism for flame stabilization is quantified in terms of relevant non-dimensional parameters, and detailed analysis of the flame and turbulence structure will be presented. We acknowledge the sponsorship of the AFOSR-NSF Joint Effort on Turbulent Combustion Model Assumptions and the DOE Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences.

Theoretical and experimental investigation of turbulent premixed flames

NASA Astrophysics Data System (ADS)

Azzazy, M. T. F.

1982-11-01

A model is proposed to describe the propagation of a plane oblique flame into a turbulent flow of premixed reactants. The model incorporates a transport equation for the single or joint PDF's of passive scalers, in addition to the conservation equations of mass, momentum, energy and K.E. of turbulence. In the first phase of developing the model, the reaction mechanism was treated as a single step irreversible exothermic reaction. In this case, the PDF of the progress variable was parameterized and solved with the conservation equations. The second phase considered a two step reaction mechanism in an attempt to explore the role played by the radicals in the propagation of turbulent premixed flames. For both the two phases, the flame speed and angle are eigenvalues of the solution. Laser induced fluorescence spectroscopy (LIFS) was used to measure the PDF of OH concentration in a laboratory scale burner simulating the flame studied by the model. The premixed methane-air flame is stabilized on a rod flame holder downstream of a turbulence producing grid. The experimentally observed PDF's of the hydroxil radical concentration, and the statistical moments, used to describe and compare the PDF's and moments of the two reaction model.

Application of near-infrared spectroscopy in the detection of fat-soluble vitamins in premix feed

NASA Astrophysics Data System (ADS)

Jia, Lian Ping; Tian, Shu Li; Zheng, Xue Cong; Jiao, Peng; Jiang, Xun Peng

2018-02-01

Vitamin is the organic compound and necessary for animal physiological maintenance. The rapid determination of the content of different vitamins in premix feed can help to achieve accurate diets and efficient feeding. Compared with high-performance liquid chromatography and other wet chemical methods, near-infrared spectroscopy is a fast, non-destructive, non-polluting method. 168 samples of premix feed were collected and the contents of vitamin A, vitamin E and vitamin D3 were detected by the standard method. The near-infrared spectra of samples ranging from 10 000 to 4 000 cm-1 were obtained. Partial least squares regression (PLSR) and support vector machine regression (SVMR) were used to construct the quantitative model. The results showed that the RMSEP of PLSR model of vitamin A, vitamin E and vitamin D3 were 0.43×107 IU/kg, 0.09×105 IU/kg and 0.17×107 IU/kg, respectively. The RMSEP of SVMR model was 0.45×107 IU/kg, 0.11×105 IU/kg and 0.18×107 IU/kg. Compared with nonlinear regression method (SVMR), linear regression method (PLSR) is more suitable for the quantitative analysis of vitamins in premix feed.

The influence of breed and sex on the incidence of mortalities and skin tears in broiler carcasses.

PubMed

Casey, N H; Smith, G A; Crosley, R I

1989-06-01

The effects of nutrition, breed and sex on the incidence of mortalities and of skin tears on broiler carcasses were studied. Both sexes of 2 breeds, Hubbard and Ross, were given 4 dietary treatments consisting of a normal level of vitamin and mineral premix plus 300 ppm furazolidone, twice normal premix inclusion level plus 300 ppm furazolidone, a normal level of vitamin and mineral premix, and twice normal mineral premix inclusion level. A coccidiostat containing the active ingredient halofuginone was included at 6 ppm, twice the recommended dosage. Starter, grower and finisher diets were fed respectively up to Day 20, Day 30 and Day 48. Group growth performances, mortalities and the incidence of torn skin were monitored on both the live birds and carcasses. The effect of the different nutritional treatments on skin tears was not significant (P = 0.9533), as was the breed effect (P = 0.0547). However, the effect of sex was significant (P = 0.0044), the incidence in hens being higher. Mortalities among the Hubbard were significantly greater than among the Ross (P = 0.0001). Hens showed a slightly higher mortality rate than roosters, tending towards significance at the 5% level (P = 0.0554).

Comparability of the effect of storage time and temperature on serum anti-Müllerian hormone measurement between original and modified enzyme-linked immunosorbent assay.

PubMed

Yue, Chao-Yan; Ying, Chun-Mei

2017-01-01

To explore the effect of modified enzyme-linked immunosorbent assay on the AMH results is increased or decreased, and to investigate the effect of storage time and temperature on AMH measurements with and without sample premixing assay buffer using the Kangrun ELISA method. Serum AMH concentration were measured by ELISA, consistency between two kits, and comparability between original and the modified assay under different stored conditions were analyzed by Passing-Bablok regression analysis and Bland-Altman bias evaluation. There was a strong consistency between AMH concentrations measured in Kangrun ELISA and Ansh Labs ultra-sensitive AMH ELISA. Pre-mixing serum specimens with assay buffer gave consistent results compared with original assay. Modified protocol can reduce the amplitude of increase affected by sample aged and give the most consistent results regardless of storage conditions. Pre-mixing protocol did not influence the results of fresh serum or frozen serum incubation <3days at 4°C and -80°C, but when specimens detected after collection and stored in other storage conditions, should be pre-mixed with assay buffer to insure its accuracy. Copyright © 2016 Elsevier B.V. All rights reserved.

Preliminary assessment of combustion modes for internal combustion wave rotors

NASA Technical Reports Server (NTRS)

Nalim, M. Razi

1995-01-01

Combustion within the channels of a wave rotor is examined as a means of obtaining pressure gain during heat addition in a gas turbine engine. Several modes of combustion are considered and the factors that determine the applicability of three modes are evaluated in detail; premixed autoignition/detonation, premixed deflagration, and non-premixed compression ignition. The last two will require strong turbulence for completion of combustion in a reasonable time in the wave rotor. The compression/autoignition modes will require inlet temperatures in excess of 1500 R for reliable ignition with most hydrocarbon fuels; otherwise, a supplementary ignition method must be provided. Examples of combustion mode selection are presented for two core engine applications that had been previously designed with equivalent 4-port wave rotor topping cycles using external combustion.

Partially Premixed Flame (PPF) Research for Fire Safety

NASA Technical Reports Server (NTRS)

Puri, Ishwar K.; Aggarwal, Suresh K.; Lock, Andrew J.; Hegde, Uday

2004-01-01

Incipient fires typically occur after the partial premixing of fuel and oxidizer. The mixing of product species into the fuel/oxidizer mixture influences flame stabilization and fire spread. Therefore, it is important to characterize the impact of different levels of fuel/oxidizer/product mixing on flame stabilization, liftoff and extinguishment under different gravity conditions. With regard to fire protection, the agent concentration required to achieve flame suppression is an important consideration. The initial stage of an unwanted fire in a microgravity environment will depend on the level of partial premixing and the local conditions such as air currents generated by the fire itself and any forced ventilation (that influence agent and product mixing into the fire). The motivation of our investigation is to characterize these impacts in a systematic and fundamental manner.

[The application of artificial protein premixes for nutritive support of patients with chronic renal insufficiency, being treated by perinateal dialysis].

PubMed

Pichugina, I S; Vetchinnikova, O N; Vereshchagina, V M; Gapparov, M M; Vatazin, A V

2008-01-01

As a result of a survey of 56 patients with chronic renal insufficiency, who undergone hemodialysis, it was established, that clinical condition of patients, biochemical and hematological blood indices as well as results of anthropometric research improve upon application of artificial balanced high-protein premixes -"Nutrinil" and "Nutrien-Nefro". Irrespective of way of administration - introperitoneal ("Nutrinil" solution) or enteral ("Nutrien-Nefro" mixture) protein-energetic insufficiency diminishes or totally disappears, body weight, fat and muscle content of the body weight, as well as indices of whole protein, albumine, lymphocytes, haemoglobin, pH approache the norm. Intraperitoneal way of administration of artificial protein premixes increase patients adherence to this procedure, though enteral way of their administration is more preferable from economic point of view.

Anomalous Z2 antiferromagnetic topological phase in pressurized SmB6

NASA Astrophysics Data System (ADS)

Chang, Kai-Wei; Chen, Peng-Jen

2018-05-01

Antiferromagnetic materials, whose time-reversal symmetry is broken, can be classified into the Z2 topology if they respect some specific symmetry. Since the theoretical proposal, however, no materials have been found to host such Z2 antiferromagnetic topological (Z2-AFT ) phase to date. Here we demonstrate that the topological Kondo insulator SmB6 can be a Z2-AFT system when pressurized to undergo an antiferromagnetic phase transition. In addition to proposing the possible candidate for a Z2-AFT material, in this work we also illustrate the anomalous topological surface states of the Z2-AFT phase which have not been discussed before. Originating from the interplay between the topological properties and the antiferromagnetic surface magnetization, the topological surface states of the Z2-AFT phase behave differently as compared with those of a topological insulator. Besides, the Z2-AFT insulators are also found promising in the generation of tunable spin currents, which is an important application in spintronics.

Tunable polymeric sorbent materials for fractionation of model naphthenates.

PubMed

Mohamed, Mohamed H; Wilson, Lee D; Headley, John V

2013-04-04

The sorption properties are reported for several examples of single-component carboxylic acids representing naphthenic acids (NAs) with β-cyclodextrin (β-CD) based polyurethane sorbents. Seven single-component examples of NAs were chosen with variable z values, carbon number, and chemical structure as follows: 2-hexyldecanoic acid (z = 0 and C = 16; S1), n-caprylic acid (z = 0 and C = 8; S2), trans-4-pentylcyclohexanecarboxylic acid (z = -2 and C = 12; S3), 4-methylcyclohexanecarboxylic acid (z = -2 and C = 8; S4), dicyclohexylacetic acid (z = -4; C = 14; S5), 4-pentylbicyclo[2.2.2]octane-1-carboxylic acid (z = -4; C = 14; S6), and lithocholic acid (z = -6; C = 24; S7). The copolymer sorbents were synthesized at three relative β-CD:diisocyanate mole ratios (i.e., 1:1, 1:2, and 1:3) using 4,4'-dicyclohexylmethane diisocyanate (CDI) and 4,4'-diphenylmethane diisocyanate (MDI). The sorption properties of the copolymer sorbents were characterized using equilibrium sorption isotherms in aqueous solution at pH 9.00 with electrospray ionization mass spectrometry. The equilibrium fraction of the unbound carboxylate anions was monitored in the aqueous phase. The sorption properties of the copolymer sorbents (i.e., Qm) were obtained from the Sips isotherm model. The Qm values generally decrease as the number of accessible β-CD inclusion sites in the copolymer framework decreases. The chemical structure of the adsorbates played an important role in their relative uptake, as evidenced by the adsorbate lipophilic surface area (LSA) and the involvement of hydrophobic effects. The copolymers exhibit molecular selective sorption of the single-component carboxylates in mixtures which suggests their application as sorbents for fractionation of mixtures of NAs. By comparison, granular activated carbon (GAC) and chitosan sorbents did not exhibit any significant molecular selective sorption relative to the copolymer materials; however, evidence of variable sorption capacity was observed among the sorbents investigated.

The conditional moment closure method for modeling lean premixed turbulent combustion

NASA Astrophysics Data System (ADS)

Martin, Scott Montgomery

Natural gas fired lean premixed gas turbines have become the method of choice for new power generation systems due to their high efficiency and low pollutant emissions. As emission regulations for these combustion systems become more stringent, the use of numerical modeling has become an important a priori tool in designing clean and efficient combustors. Here a new turbulent combustion model is developed in an attempt to improve the state of the art. The Conditional Moment Closure (CMC) method is a new theory that has been applied to non-premixed combustion with good success. The application of the CMC method to premixed systems has been proposed, but has not yet been done. The premixed CMC method replaces the species mass fractions as independent variables with the species mass fractions that are conditioned on a reaction progress variable (RPV). Conservation equations for these new variables are then derived and solved. The general idea behind the CMC method is that the behavior of the chemical species is closely coupled to the reaction progress variable. Thus, species conservation equations that are conditioned on the RPV will have terms involving the fluctuating quantities that are much more likely to be negligible. The CMC method accounts for the interaction between scalar dissipation (micromixing) and chemistry, while de-coupling the kinetics from the bulk flow (macromixing). Here the CMC method is combined with a commercial computational fluid dynamics program, which calculates the large-scale fluid motions. The CMC model is validated by comparison to 2-D reacting backward facing step data. Predicted species, temperature and velocity fields are compared to experimental data with good success. The CMC model is also validated against the University of Washington's 3-D jet stirred reactor (JSR) data, which is an idealized lean premixed combustor. The JSR results are encouraging, but not as good as the backward facing step. The largest source of error is from the turbulence models, which are inadequate for the variable density and recirculating flows modeled here. The limitations of the turbulence models affected the calculation of the flow statistics, which are used to calculate the variance of the RPV, the scalar dissipation and the PDF.

Development of Criteria for Flameholding Tendencies within Premixer Passages for High Hydrogen Content Fuels

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

Lewis, Elliot Sullivan-; McDonell, Vincent G.

Due to increasingly stringent air quality requirements stationary power gas turbines have moved to lean-premixed operation, which reduces pollutant emissions but can result in flashback. Flashback can cause serious damage to the premixer hardware. Curtailing flashback can be difficult with hydrocarbon fuels and becomes even more challenging when hydrogen is used as the fuel. The two main approaches for coping with flashback are either to design a combustor that is resistant to flashback, or to design a premixer that will not anchor a flame if flashback occurs. Even with a well-designed combustor flashback can occur under certain circumstances, thus itmore » is necessary to determine how to avoid flameholding within the premixer passageways of a gas turbine. To this end, an experiment was designed that would determine the flameholding propensities at elevated pressures and temperatures of three different classes of geometric features commonly found in gas turbine premixers, with both natural gas and hydrogen fuel. Experiments to find the equivalence ratio at blow off were conducted within an optically accessible test apparatus with four flameholders: 0.25 and 0.50 inch diameter cylinders, a reverse facing step with a height of 0.25 inches, and a symmetric airfoil with a thickness of 0.25 inches and a chord length of one inch. Tests were carried out at temperatures between 300 K and 750 K, at pressures up to 9 atmospheres. Typical bulk velocities were between 40 and 100 m/s. The effect of airfoil’s angle of rotation was also investigated. Blow off for hydrogen flames was found to occur at much lower adiabatic flame temperatures than natural gas flames. Additionally it was observed that at high pressures and high turbulence intensities, reactant velocity does not have a noticeable effect on the point of blow off due in large part to corresponding increases in turbulent flame speed. Finally a semi empirical correlation was developed that predicts flame extinction for both natural gas and hydrogen flames.« less

Turbulent piloted partially-premixed flames with varying levels of O2/N2: stability limits and PDF calculations

NASA Astrophysics Data System (ADS)

Juddoo, Mrinal; Masri, Assaad R.; Pope, Stephen B.

2011-12-01

This paper reports measured stability limits and PDF calculations of piloted, turbulent flames of compressed natural gas (CNG) partially-premixed with either pure oxygen, or with varying levels of O2/N2. Stability limits are presented for flames of CNG fuel premixed with up to 20% oxygen as well as CNG-O2-N2 fuel where the O2 content is varied from 8 to 22% by volume. Calculations are presented for (i) Sydney flame B [Masri et al. 1988] which uses pure CNG as well as flames B15 to B25 where the CNG is partially-premixed with 15-25% oxygen by volume, respectively and (ii) Sandia methane-air (1:3 by volume) flame E [Barlow et al. 2005] as well as new flames E15 and E25 that are partially-premixed with 'reconstituted air' where the O2 content in nitrogen is 15 and 25% by volume, respectively. The calculations solve a transported PDF of composition using a particle-based Monte Carlo method and employ the EMST mixing model as well as detailed chemical kinetics. The addition of oxygen to the fuel increases stability, shortens the flames, broadens the reaction zone, and shifts the stoichiometric mixture fraction towards the inner side of the jet. It is found that for pure CNG flames where the reaction zone is narrow (∼0.1 in mixture fraction space), the PDF calculations fail to reproduce the correct level of local extinction on approach to blow-off. A broadening in the reaction zone up to about 0.25 in mixture fraction space is needed for the PDF/EMST approach to be able to capture these finite-rate chemistry effects. It is also found that for the same level of partial premixing, increasing the O2/N2 ratio increases the maximum levels of CO and NO but shifts the peak to richer mixture fractions. Over the range of oxygenation investigated here, stability limits have shown to improve almost linearly with increasing oxygen levels in the fuel and with increasing the contribution of release rate from the pilot.

High-Z material erosion and its control in DIII-D carbon divertor

DOE PAGES

Ding, Rui; Rudakov, Dimitry L.; Stangeby, Peter C.; ...

2017-03-16

It is expected that high-Z materials will be used as plasma-facing components (PFCs) in future fusion devices, making the erosion of high-Z material a key issue for high-power, long pulse operation. High-Z material erosion and redeposition have been studied using tungsten and molybdenum coated samples exposed in well-diagnosed DIII-D divertor plasma discharges. By coupling dedicated experiments and modelling using the 3D Monte Carlo code ERO, the roles of sheath potential and background carbon impurities in determining high-Z material erosion are identified. Different methods suggested by modelling have been investigated to control high-Z material erosion in DIII-D experiments. The erosion ofmore » Mo and W are found to be strongly suppressed by local injection of methane and deuterium gases. The 13C deposition resulting from local 13CH 4 injection also provides information on radial transport due to E×B drifts and cross field diffusion. Finally, D 2 gas puffing is found to cause 2 local plasma perturbation, suppressing W erosion because of the lower effective sputtering yield of W at lower plasma temperature and for higher carbon concentration in the mixed surface layer.« less

Effects of combined dimension reduction and tabulation on the simulations of a turbulent premixed flame using a large-eddy simulation/probability density function method

NASA Astrophysics Data System (ADS)

Kim, Jeonglae; Pope, Stephen B.

2014-05-01

A turbulent lean-premixed propane-air flame stabilised by a triangular cylinder as a flame-holder is simulated to assess the accuracy and computational efficiency of combined dimension reduction and tabulation of chemistry. The computational condition matches the Volvo rig experiments. For the reactive simulation, the Lagrangian Large-Eddy Simulation/Probability Density Function (LES/PDF) formulation is used. A novel two-way coupling approach between LES and PDF is applied to obtain resolved density to reduce its statistical fluctuations. Composition mixing is evaluated by the modified Interaction-by-Exchange with the Mean (IEM) model. A baseline case uses In Situ Adaptive Tabulation (ISAT) to calculate chemical reactions efficiently. Its results demonstrate good agreement with the experimental measurements in turbulence statistics, temperature, and minor species mass fractions. For dimension reduction, 11 and 16 represented species are chosen and a variant of Rate Controlled Constrained Equilibrium (RCCE) is applied in conjunction with ISAT to each case. All the quantities in the comparison are indistinguishable from the baseline results using ISAT only. The combined use of RCCE/ISAT reduces the computational time for chemical reaction by more than 50%. However, for the current turbulent premixed flame, chemical reaction takes only a minor portion of the overall computational cost, in contrast to non-premixed flame simulations using LES/PDF, presumably due to the restricted manifold of purely premixed flame in the composition space. Instead, composition mixing is the major contributor to cost reduction since the mean-drift term, which is computationally expensive, is computed for the reduced representation. Overall, a reduction of more than 15% in the computational cost is obtained.

Clinical use of the co-formulation of insulin degludec and insulin aspart.

PubMed

Kumar, A; Awata, T; Bain, S C; Ceriello, A; Fulcher, G R; Unnikrishnan, A G; Arechavaleta, R; Gonzalez-Gálvez, G; Hirose, T; Home, P D; Kaku, K; Litwak, L; Madsbad, S; Pinget, M; Mehta, R; Mithal, A; Tambascia, M; Tibaldi, J; Christiansen, J S

2016-08-01

To provide a review of the available data and practical use of insulin degludec with insulin aspart (IDegAsp). Premixed insulins provide basal and prandial glucose control; however, they have an intermediate-acting prandial insulin component and do not provide as effective basal coverage as true long-acting insulins, owing to the physicochemical incompatibility of their individual components, coupled with the inflexibility of adjustment. The molecular structure of the co-formulation of IDegAsp, a novel insulin preparation, allows these two molecules to coexist without affecting their individual pharmacodynamic profiles. Clinical evidence in phase 2/3 trials of IDegAsp efficacy and safety in type 1 and type 2 diabetes mellitus (T1DM and T2DM) have been assessed and summarised. In people with T2DM, once- and twice-daily dosing provides similar overall glycaemic control (HbA1c ) to current modern insulins, but with lower risk of nocturnal hypoglycaemia. In prior insulin users, glycaemic control was achieved with lower or equal insulin doses vs. other basal+meal-time or premix insulin regimens. In insulin-naïve patients with T2DM, IDegAsp can be started once or twice-daily, based on individual need. People switching from more than once-daily basal or premix insulin therapy can be converted unit-to-unit to once-daily IDegAsp, although this strategy should be assessed by the physician on an individual basis. IDegAsp offers physicians and people with T2DM a simpler insulin regimen than other available basal-bolus or premix-based insulin regimens, with stable daytime basal coverage, a lower rate of hypoglycaemia and some flexibility in injection timing compared with premix insulins. © 2016 John Wiley & Sons Ltd.

Oscillatory Extinction Of Spherical Diffusion Flames

NASA Technical Reports Server (NTRS)

Law, C. K.; Yoo, S. W.; Christianson, E. W.

2003-01-01

Since extinction has been observed in an oscillatory manner in Le greater than 1 premixed flames, it is not unreasonable to expect that extinction could occur in an unsteady manner for diffusion flames. Indeed, near-limit oscillations have been observed experimentally under microgravity conditions for both candle flames and droplet flames. Furthermore, the analysis of Cheatham and Matalon on the unsteady behavior of diffusion flames with heat loss, identified an oscillatory regime which could be triggered by either a sufficiently large Lewis number (even without heat loss) or an appreciable heat loss (even for Le=1). In light of these recent understanding, the present investigation aims to provide a well-controlled experiment that can unambiguously demonstrate the oscillation of diffusion flames near both the transport- and radiation-induced limits. That is, since candle and jet flames are stabilized through flame segments that are fundamentally premixed in nature, and since premixed flames are prone to oscillate, there is the possibility that the observed oscillation of these bulk diffusion flames could be triggered and sustained by the oscillation of the premixed flame segments. Concerning the observed oscillatory droplet extinction, it is well-known that gas-phase oscillation in heterogeneous burning can be induced by and is thereby coupled with condensed-phase unsteadiness. Consequently, a convincing experiment on diffusion flame oscillation must exclude any ingredients of premixed flames and other sources that may either oscillate themselves or promote the oscillation of the diffusion flame. The present experiment on burner-generated spherical flames with a constant reactant supply endeavored to accomplish this goal. The results are further compared with those from computational simulation for further understanding and quantification of the flame dynamics and extinction.

Quantification of trace metals in infant formula premixes using laser-induced breakdown spectroscopy

NASA Astrophysics Data System (ADS)

Cama-Moncunill, Raquel; Casado-Gavalda, Maria P.; Cama-Moncunill, Xavier; Markiewicz-Keszycka, Maria; Dixit, Yash; Cullen, Patrick J.; Sullivan, Carl

2017-09-01

Infant formula is a human milk substitute generally based upon fortified cow milk components. In order to mimic the composition of breast milk, trace elements such as copper, iron and zinc are usually added in a single operation using a premix. The correct addition of premixes must be verified to ensure that the target levels in infant formulae are achieved. In this study, a laser-induced breakdown spectroscopy (LIBS) system was assessed as a fast validation tool for trace element premixes. LIBS is a promising emission spectroscopic technique for elemental analysis, which offers real-time analyses, little to no sample preparation and ease of use. LIBS was employed for copper and iron determinations of premix samples ranging approximately from 0 to 120 mg/kg Cu/1640 mg/kg Fe. LIBS spectra are affected by several parameters, hindering subsequent quantitative analyses. This work aimed at testing three matrix-matched calibration approaches (simple-linear regression, multi-linear regression and partial least squares regression (PLS)) as means for precision and accuracy enhancement of LIBS quantitative analysis. All calibration models were first developed using a training set and then validated with an independent test set. PLS yielded the best results. For instance, the PLS model for copper provided a coefficient of determination (R2) of 0.995 and a root mean square error of prediction (RMSEP) of 14 mg/kg. Furthermore, LIBS was employed to penetrate through the samples by repetitively measuring the same spot. Consequently, LIBS spectra can be obtained as a function of sample layers. This information was used to explore whether measuring deeper into the sample could reduce possible surface-contaminant effects and provide better quantifications.

Joint inversion of high resolution S-wave velocity structure underneath North China Basin

NASA Astrophysics Data System (ADS)

Yang, C.; Li, G.; Niu, F.

2017-12-01

North China basin is one of earthquake prone areas in China. Many devastating earthquakes occurred in the last century and before, such as the 1937 M7.0 Heze Earthquake in Shandong province, the 1966 M7.2 Xingtai Earthquake and 1976 Tangshan Earthquake in Hebei province. Knowing the structure of the sediment cover is of great importance to predict strong ground motion caused by earthquakes. Unconsolidated sediments are loose materials, ranging from clay to sand to gravel. Earthquakes can liquefy unconsolidated sediments, thus knowing the distribution and thickness of the unconsolidated sediments has significant implication in seismic hazard analysis of the area. Quantitative estimates of the amount of extension of the North China basin is important to understand the thinning and evolution of the eastern North China craton and the underlying mechanism. In principle, the amount of lithospheric stretching can be estimated from sediment and crustal thickness. Therefore an accurate estimate of the sediment and crustal thickness of the area is also important in understanding regional tectonics. In this study, we jointly invert the Rayleigh wave phase-velocity dispersion and Z/H ratio data to construct a 3-D S-wave velocity model beneath North China area. We use 4-year ambient noise data recorded from 249 temporary stations, and 139 earthquake events to extract Rayleigh wave Z/H ratios. The Z/H ratios obtained from ambient noise data and earthquake data show a good agreement within the overlapped periods. The phase velocity dispersion curve was estimated from the same ambient noise data. The preliminary result shows a relatively low Z/H ratio and low velocity anomaly at the shallow part of sediment basins.

Partially premixed prevalorized kerosene spray combustion in turbulent flow

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

Chrigui, M.; Ahmadi, W.; Sadiki, A.

2010-04-15

A detailed numerical simulation of kerosene spray combustion was carried out on a partially premixed, prevaporized, three-dimensional configuration. The focus was on the flame temperature profile dependency on the length of the pre-vaporization zone. The results were analyzed and compared to experimental data. A fundamental study was performed to observe the temperature variation and flame flashback. Changes were made to the droplet diameter, kerosene flammability limits, a combustion model parameter and the location of the combustion initialization. Investigations were performed for atmospheric pressure, inlet air temperature of 90 C and a global equivalence ratio of 0.7. The simulations were carriedmore » out using the Eulerian Lagrangian procedure under a fully two-way coupling. The Bray-Moss-Libby model was adjusted to account for the partially premixed combustion. (author)« less

Systems and methods for preventing flashback in a combustor assembly

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

Johnson, Thomas Edward; Ziminsky, Willy Steve; Stevenson, Christian Xavier

2016-04-05

Embodiments of the present application include a combustor assembly. The combustor assembly may include a combustion chamber, a first plenum, a second plenum, and one or more elongate air/fuel premixing injection tubes. Each of the elongate air/fuel premixing injection tubes may include a first length at least partially disposed within the first plenum and configured to receive a first fluid from the first plenum. Moreover, each of the elongate air/fuel premixing injection tubes may include a second length disposed downstream of the first length and at least partially disposed within the second plenum. The second length may be formed ofmore » a porous wall configured to allow a second fluid from the second plenum to enter the second length and create a boundary layer about the porous wall.« less

Premixing quality and flame stability: A theoretical and experimental study

NASA Technical Reports Server (NTRS)

Radhakrishnan, K.; Heywood, J. B.; Tabaczynski, R. J.

1979-01-01

Models for predicting flame ignition and blowout in a combustor primary zone are presented. A correlation for the blowoff velocity of premixed turbulent flames is developed using the basic quantities of turbulent flow, and the laminar flame speed. A statistical model employing a Monte Carlo calculation procedure is developed to account for nonuniformities in a combustor primary zone. An overall kinetic rate equation is used to describe the fuel oxidation process. The model is used to predict the lean ignition and blow out limits of premixed turbulent flames; the effects of mixture nonuniformity on the lean ignition limit are explored using an assumed distribution of fuel-air ratios. Data on the effects of variations in inlet temperature, reference velocity and mixture uniformity on the lean ignition and blowout limits of gaseous propane-air flames are presented.

UV treatments on the physicochemical properties of tilapia skin and pig skin gelatin.

PubMed

Wu, C K; Tsai, J S; Chen, Z Y; Sung, W C

2015-06-01

Tilapia skin gelatin, pig skin gelatin, and their mousse premixes were exposed to UV irradiation for 103, 206, and 309 kJ/cm(2). All samples after 309 kJ/cm(2) exposure exhibited a significant increase in gel strength, gel forming ability as well as viscosity of solutions. It was shown that UV treatment could also improve the pig skin gelatin foam stability and foam formation ability compared to those of tilapia skin gelatin. Nevertheless, the panelists gave the lowest scores to mousse made with 309 kJ/cm(2) UV-irradiated premix mousse pig skin gelatin. Tilapia skin gelatin could be used as a substitute ingredient for premix mousse made from pig skin gelatin. © The Author(s) 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Turbulent transport in premixed flames

NASA Technical Reports Server (NTRS)

Rutland, C. J.; Cant, R. S.

1994-01-01

Simulations of planar, premixed turbulent flames with heat release were used to study turbulent transport. Reynolds stress and Reynolds flux budgets were obtained and used to guide the investigation of important physical effects. Essentially all pressure terms in the transport equations were found to be significant. In the Reynolds flux equations, these terms are the major source of counter-gradient transport. Viscous and molecular terms were also found to be significant, with both dilatational and solenoidal terms contributing to the Reynolds stress dissipation. The BML theory of premixed turbulent combustion was critically examined in detail. The BML bimodal pdf was found to agree well with the DNS data. All BML decompositions, through the third moments, show very good agreement with the DNS results. Several BML models for conditional terms were checked using the DNS data and were found to require more extensive development.

Why does preferential diffusion strongly affect premixed turbulent combustion?

NASA Technical Reports Server (NTRS)

Kuznetsov, Vadim R.

1993-01-01

Combustion of premixed reactants in a turbulent flow is a classical but unresolved problem. The key problem is to explain the following data: the maximal turbulent and laminar burning velocities u(sub t) and u(sub L) occur at different equivalence ratios Phi. It is known that the equivalence ratio varies along a curved flame if molecular diffusivity D(sub fuel) does not equal D(sub oxygen). However, the mean flame radius of curvature is much larger than the laminar flame thickness delta-L. Therefore, significant influence of preferential diffusion should occur only if the flame propagation speed varies with flame curvature. This conclusion agrees with Zel'dovich's long-standing idea about the important role of leading points of a flame. The main objective of this paper is to prove Zel'dovich's hypothesis. An equation for the mean flame surface area density (MFSAD) is employed for this purpose. The second objective of this paper is to suggest a different approach to the derivation of the equation for MFSAD. It is based on the pdf equation for the reaction progress variable C and the relation between the pdf and MFSAD. This treatment suggests an entirely different closure assumption.

Template-free hydrothermal synthesis of beaded nanochain bundles of ZnO and their application as photoanode in dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Ballal, Reshma; Shinde, Manish; Waghadkar, Yogesh; Arbuj, Sudhir; Rane, Sunit; Chauhan, Ratna

2018-02-01

ZnO shows promising candidature as photoanode material for dye-sensitized solar cells (DSSCs) due to its high bulk electron mobility and easily tailorable geometrical structures. The objective of this study is to facilitate the development of highly porous hierarchical ZnO for enhanced power conversion efficiency in dye-sensitized solar cells (DSSC) due to its greater dye adsorption. This study investigated the influence of reaction temperatures of 120 °C (sample Z-1) and 180 °C (sample Z-2) in hydrothermal synthesis on structural, morphological and optical properties of resultant ZnO nanostructures and their performance as photoanode material in DSSCs. The synthesized beaded nanochain bundles of ZnO, with multilayered and highly ordered texture, have diameters of several micrometers. Structural and morphological analysis shows that the ZnO beaded nanochain-like architectures possess wurtzite crystalline nature. These morphological improvements (beaded nanochains) of ZnO were found to exhibit higher dye loading and conversion efficiency due to increase in the surface area while reducing charge recombination. The maximum conversion efficiency was obtained with Z-1 and Z-2 is 2.95 and 3.56% with photocurrent of 7.73 and 9.24 mA/cm2, respectively. The obtained results pertaining to the DSSC performance studies were corroborated by the impedance spectroscopy data.

Asymptotic Methods Especially in Combustion.

DTIC Science & Technology

1981-11-01

1980.) Invited paper. 101. G.S.S. Ludford & Asok K. Sen: Burning rate maximum of a plane premixed flame. Proceedings of the Seventh International...Reactive Systems, ed. by J. Ray Bowen, N. Manson, Antoni K. Ompenheim, and R.I. Soloukhin.) 102. G.S.S. Ludford: Premixed cylindrical flames...106. Asok K. Sen & 0.S.S. Ludford: Effects of mass diffusion on the burning rate of non-4ilute mixtures. Proceedings of the Eighteenth Symposium

Modeling of Dissipation Element Statistics in Turbulent Non-Premixed Jet Flames

NASA Astrophysics Data System (ADS)

Denker, Dominik; Attili, Antonio; Boschung, Jonas; Hennig, Fabian; Pitsch, Heinz

2017-11-01

The dissipation element (DE) analysis is a method for analyzing and compartmentalizing turbulent scalar fields. DEs can be described by two parameters, namely the Euclidean distance l between their extremal points and the scalar difference in the respective points Δϕ . The joint probability density function (jPDF) of these two parameters P(Δϕ , l) is expected to suffice for a statistical reconstruction of the scalar field. In addition, reacting scalars show a strong correlation with these DE parameters in both premixed and non-premixed flames. Normalized DE statistics show a remarkable invariance towards changes in Reynolds numbers. This feature of DE statistics was exploited in a Boltzmann-type evolution equation based model for the probability density function (PDF) of the distance between the extremal points P(l) in isotropic turbulence. Later, this model was extended for the jPDF P(Δϕ , l) and then adapted for the use in free shear flows. The effect of heat release on the scalar scales and DE statistics is investigated and an extended model for non-premixed jet flames is introduced, which accounts for the presence of chemical reactions. This new model is validated against a series of DNS of temporally evolving jet flames. European Research Council Project ``Milestone''.

Theoretical and experimental investigation of turbulent premixed flames

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

Azzazy, M.T.F.

1982-01-01

A model is proposed to describe the propagation of a plane oblique flame into a turbulent flow of premixed reactants. The model incorporates a transport equation for the single or joint PDF's of passive scalers, in addition to the conservation equations of mass, momentum, energy and K.E. of turbulence. In the first phase of developing the model, the reaction mechanism was treated as a single step irreversible exothermic reaction. In this case, the PDF of the progress variable was parameterized and solved with the conservation equations. The second phase considered a two step reaction mechanism in an attempt to exploremore » the role played by the radicals in the propagation of turbulent premixed flames. For both the two phases, the flame speed and angle are Eigenvalues of the solution. Laser Induced Fluoresence Spectroscopy (LIFS) was used to measure the PDF of OH concentration in a laboratory scale burner simulating the flame studied by the model. The premixed Methane-Air flame was stabilized on a rod flame holder downstream of a turbulence producing grid. Measurements in both the streamwise and transverse directions were made for a variety of flow conditions. The experimentally observed PDF's of the hydroxil radical concentration, and the statistical moments, were used to describe and compare the PDF's and moments of the two reaction model.« less

A Study of Strain Rate Effects for Turbulent Premixed Flames with Application to LES of a Gas Turbine Combustor Model

DOE PAGES

Kemenov, Konstantin A.; Calhoon, William H.

2015-03-24

Large-scale strain rate field, a resolved quantity which is easily computable in large-eddy simulations (LES), could have profound effects on the premixed flame properties by altering the turbulent flame speed and inducing local extinction. The role of the resolved strain rate has been investigated in a posterior LES study of GE lean premixed dry low NOx emissions LM6000 gas turbine combustor model. A novel approach which is based on the coupling of the lineareddy model with a one-dimensional counter-flow solver has been applied to obtain the parameterizations of the resolved premixed flame properties in terms of the reactive progress variable,more » the local strain rate measure, and local Reynolds and Karlovitz numbers. The strain rate effects have been analyzed by comparing LES statistics for several models of the turbulent flame speed, i.e, with and without accounting for the local strain rate effects, with available experimental data. The sensitivity of the simulation results to the inflow velocity conditions as well as the grid resolution have been also studied. Overall, the results suggest the necessity to represent the strain rate effects accurately in order to improve LES modeling of the turbulent flame speed.« less

A Priori Analysis of Flamelet-Based Modeling for a Dual-Mode Scramjet Combustor

NASA Technical Reports Server (NTRS)

Quinlan, Jesse R.; McDaniel, James C.; Drozda, Tomasz G.; Lacaze, Guilhem; Oefelein, Joseph

2014-01-01

An a priori investigation of the applicability of flamelet-based combustion models to dual-mode scramjet combustion was performed utilizing Reynolds-averaged simulations (RAS). For this purpose, the HIFiRE Direct Connect Rig (HDCR) flowpath, fueled with a JP-7 fuel surrogate and operating in dual- and scram-mode was considered. The chemistry of the JP-7 fuel surrogate was modeled using a 22 species, 18-step chemical reaction mechanism. Simulation results were compared to experimentally-obtained, time-averaged, wall pressure measurements to validate the RAS solutions. The analysis of the dual-mode operation of this flowpath showed regions of predominately non-premixed, high-Damkohler number, combustion. Regions of premixed combustion were also present but associated with only a small fraction of the total heat-release in the flow. This is in contrast to the scram-mode operation, where a comparable amount of heat is released from non-premixed and premixed combustion modes. Representative flamelet boundary conditions were estimated by analyzing probability density functions for temperature and pressure for pure fuel and oxidizer conditions. The results of the present study reveal the potential for a flamelet model to accurately model the combustion processes in the HDCR and likely other high-speed flowpaths of engineering interest.

DNS of turbulent premixed slot flames with mixture inhomogeneity: a study of NOx formation

NASA Astrophysics Data System (ADS)

Luca, Stefano; Attili, Antonio; Bisetti, Fabrizio

2016-11-01

A set of Direct Numerical Simulations of three-dimensional methane/air lean flames in a spatially developing turbulent slot burner are performed. The flames are in the thin-reaction zone regimes and the jet Reynolds number is 5600. This configuration is of interest since it displays turbulent production by mean shear as in real devices. The gas phase hydrodynamics are modeled with the reactive, unsteady Navier-Stokes equations in the low Mach number limit. Combustion is treated with finite-rate chemistry. The jet is characterized by a non-uniform equivalence ratio at the inlet and varying levels of incomplete premixing for the methane/air mixture are considered. The global equivalence ratio is 0.7 and temperature is 800 K. All simulations are performed at 4 atm. The instantaneous profiles of the mass fractions of methane and air at the inlet are sampled from a set of turbulent channel simulations that provide realistic, fully turbulent fields. The data are analyzed to study the influence of partial premixing on the flame structure. Particular focus is devoted to the assessment of heat release rate fluctuations and NOx formation. In particular, the effects of partial premixing on the production rates for the various pathways to NOx formation are investigated.

On the Structure and Stabilization Mechanisms of Planar and Cylindrical Premixed Flames

NASA Technical Reports Server (NTRS)

Eng, James A.; Zhu, Delin; Law, Chung K.

1993-01-01

The configurational simplicity of the stationary one-dimensional flames renders them intrinsically attractive for fundamental flame structure studies. The possibility and fidelity of studies of such flames on earth, however, have been severely restricted by the unidirectional nature of the gravity vector. To demonstrate these complications, let us first consider the premixed flame. Here a stationary, one-dimensional flame can be established by using the flat-flame burner. We next consider nonpremixed flames. First it may be noted that in an unbounded gravity-free environment, the only stationary one-dimensional flame is the spherical flame. Indeed, this is a major motivation for the study of microgravity droplet combustion, in which the gas-phase processes can be approximated to be quasi-steady because of the significant disparity between the gas and liquid densities for subcritical combustion. In view of the above considerations, an experimental and theoretical program on cylindrical and spherical premixed and nonpremixed flames in microgravity has been initiated. For premixed flames, we are interested in: (1) assessing the heat loss versus flow divergence as the dominant stabilization mechanism; (2) determining the laminar flame speed by using this configuration; and (3) understanding the development of flamefront instability and the effects of the flame curvature on the burning intensity.

Large eddy simulation of bluff body stabilized premixed and partially premixed combustion

NASA Astrophysics Data System (ADS)

Porumbel, Ionut

Large Eddy Simulation (LES) of bluff body stabilized premixed and partially premixed combustion close to the flammability limit is carried out in this thesis. The main goal of the thesis is the study of the equivalence ratio effect on flame stability and dynamics in premixed and partially premixed flames. An LES numerical algorithm able to handle the entire range of combustion regimes and equivalence ratios is developed for this purpose. The algorithm has no ad-hoc adjustable model parameters and is able to respond automatically to variations in the inflow conditions, without user intervention. Algorithm validation is achieved by conducting LES of reactive and non-reactive flow. Comparison with experimental data shows good agreement for both mean and unsteady flow properties. In the reactive flow, two scalar closure models, Eddy Break-Up (EBULES) and Linear Eddy Mixing (LEMLES), are used and compared. Over important regions, the flame lies in the Broken Reaction Zone regime. Here, the EBU model assumptions fail. In LEMLES, the reaction-diffusion equation is not filtered, but resolved on a linear domain and the model maintains validity. The flame thickness predicted by LEMLES is smaller and the flame is faster to respond to turbulent fluctuations, resulting in a more significant wrinkling of the flame surface when compared to EBULES. As a result, LEMLES captures better the subtle effects of the flame-turbulence interaction, the flame structure shows higher complexity, and the far field spreading of the wake is closer to the experimental observations. Three premixed (φ = 0.6, 0.65, and 0.75) cases are simulated. As expected, for the leaner case (φ = 0.6) the flame temperature is lower, the heat release is reduced and vorticity is stronger. As a result, the flame in this case is found to be unstable. In the rich case (φ = 0.75), the flame temperature is higher, and the spreading rate of the wake is increased due to the higher amount of heat release. The ignition delay in the lean case (φ = 0.6) is larger when compared to the rich case (φ = 0.75), in correlation with the instantaneous flame stretch. Partially premixed combustion is simulated for cases where the transverse profile of the inflow equivalence ratio is variable. The simulations show that for mixtures leaner in the core the vortical pattern tends towards anti-symmetry and the heat release decreases, resulting also in instability of the flame. For mixtures richer in the core, the flame displays sinusoidal flapping that results in larger wake spreading. The numerical simulations presented in this study employed simple, one-step chemical mechanisms. More accurate predictions of flame stability will require the use of detailed chemistry, raising the computational cost of the simulation. To address this issue, a novel algorithm for training Artificial Neural Networks (ANN) for prediction of the chemical source terms has been implemented and tested. Compared to earlier methods, such as reaction rate tabulation, the main advantages of the ANN method are in CPU time and disk space and memory reduction. The results of the testing indicate reasonable algorithm accuracy although some regions of the flame exhibit relatively significant differences compared to direct integration.

Analysis of macamides in samples of Maca (Lepidium meyenii) by HPLC-UV-MS/MS.

PubMed

McCollom, Megan M; Villinski, Jacquelyn R; McPhail, Kerry L; Craker, Lyle E; Gafner, Stefan

2005-01-01

The macamides are a distinct class of secondary metabolites that have so far been found only in Lepidium meyenii Walp. (Maca). Using HPLC-UV-MS/MS, the main macamides have been identified as n-benzylhexadecanamide, n-benzyl-(9Z)-octadecenamide, n-benzyl-(9Z, 12Z)-octadecadienamide, n-benzyl-(9Z, 12Z, 15Z)-octadecatrienamide and n-benzyloctadecanamide. The identities of n-benzyl-(9Z)-octadecenamide and n-benzyl-(9Z, 12Z)-octadecadienamide were confirmed by comparison of chromatographic and spectral properties with synthetic analogues. Total macamides have been quantified by HPLC-UV in plant material from different vendors using n-benzylhexadecanamide as an external standard. The amount of macamides in the dried plant material ranged from 0.0016 to 0.0123%.

[Health needs of the diabetic user of primary care].

PubMed

Salinas-Martínez, A M; Muñoz-Moreno, F; Barraza de León, A R; Villarreal-Ríos, E; Núñez-Rocha, G M; Garza-Elizondo, M E

2001-01-01

To determine the extent and importance of unmet health needs of type 2 diabetic patients seen at primary care services. A cross-sectional study was conducted in 1999, among rural and urban patients of the Mexican Institute of Social Security, in Nuevo Leon, Mexico. The study population consisted of 256 subjects selected at random, diagnosed with type-II diabetes for at least two years. Data were obtained by interview and complemented with medical charts and provider interviews. Five health areas and four health determinants were evaluated, through Mexican Official Standards and American Diabetes Association standards of medical care for diabetic patients. Analysis consisted of descriptive statistics and estimation of z scores. Health needs were met in 49% of cases. A lower mean of health need satisfaction was found in rural regions as compared to urban regions (36.8% vs. 53.3%, p < .01). Nutrition was the most affected health area (z score = -6), followed by the physical exercise (z score = -1), the metabolic health area (z score = +1), the non-smoking health area (z score = +2), the prevention and early detection of complications health area (z score = +2), and the cognitive health area (z score = +3). The health determinant with the highest requirement corresponded to utilization (z score = -5), followed by resource availability (z score = -4), perceived health need (z score = +4), and access barriers (z score = +6). Health need measurement allows evaluating the effectiveness of existing interventions, in addition to identifying areas with higher unmet health needs. These findings facilitate analysis and decision-making to devise specific health policies and actions directed at improving the quality of care for diabetic patients. The English version of this paper is available at: http://www.insp.mx/salud/index.html

Lean, Premixed-Prevaporized (LPP) combustor conceptual design study

NASA Technical Reports Server (NTRS)

Dickman, R. A.; Dodds, W. J.; Ekstedt, E. E.

1979-01-01

Four combustion systems were designed and sized for the energy efficient engine. A fifth combustor was designed for the cycle and envelope of the twin-spool, high bypass ratio, high pressure ratio turbofan engine. Emission levels, combustion performance, life, and reliability assessments were made for these five combustion systems. Results of these design studies indicate that cruise NOx emission can be reduced by the use of lean, premixed-prevaporaized combustion and airflow modulation.

Variable tolerance among Palmer amaranth (Amaranthus palmeri) biotypes to glyphosate, 2,4-D amine, and premix formulation of glyphosate plus 2,4-D choline (Enlist Duo®) herbicide

USDA-ARS?s Scientific Manuscript database

Adoption of soybean that is resistant to 2,4-D will result in more use of glyphosate plus 2,4-D premixes and tank-mixtures. Preliminary whole-plant greenhouse assays confirm most Palmer amaranth found in Indiana are glyphosate-resistant (GR) and some biotypes exhibit tolerance to 2,4-D amine. Dose r...

Direct-Coupled Plasma-Assisted Combustion Using a Microwave Waveguide Torch

DTIC Science & Technology

2011-12-01

enhance combustion by coupling an atmospheric plasma dis- charge to a premixed methane/air flame. The absorbed microwave power ranges from 60 to 150 W...The plasma system allows for complete access of the plasma- enhanced flame for laser and optical diagnostics 0093-3813/$26.00 © 2011 IEEE Report...microwave waveguide is used to initiate and enhance combustion by coupling an atmospheric plasma discharge to a premixed methane/air flame. The

Mechanism of Combustion of Heterogeneous Solid Propellants

DTIC Science & Technology

1998-09-01

This suggests that under these conditions the matrix outflow is essentially premixed at the LLEF standoff height and premixed canopy flames (Figs. 4a...graphs like that in Fig. 5 are not available (or economically obtainable) for all the combinations of possible interest (O/F ratio, size of fine AP...HNIW matrix and the AP/matrix/AP sandwiches were essentially the same, suggesting that the matrix controlled the rate. In contrast, the rate of the

Experimental study on the flame behaviors of premixed methane/air mixture in horizontal rectangular ducts

NASA Astrophysics Data System (ADS)

Chen, Dongliang; Sun, Jinhua; Chen, Sining; Liu, Yi; Chu, Guanquan

2007-01-01

In order to explore the flame propagation characteristics and tulip flame formation mechanism of premixed methane/air mixture in horizontal rectangular ducts, the techniques of Schlieren and high-speed video camera are used to study the flame behaviors of the premixed gases in a closed duct and opened one respectively, and the propagation characteristics in both cases and the formation mechanism of the tulip flame are analyzed. The results show that, the propagation flame in a closed duct is prior to form a tulip flame structure than that in an opened duct, and the tulip flame structure formation in a closed duct is related to the flame propagation velocity decrease. The sharp decrease of the flame propagation velocity is one of the reasons to the tulip flame formation, and the decrease of the flame propagation velocity is due to the decrease of the burned product flow velocity mainly.

Large Eddy Simulation of Flame Flashback in Swirling Premixed Flames

NASA Astrophysics Data System (ADS)

Lietz, Christopher; Raman, Venkatramanan

2014-11-01

In the design of high-hydrogen content gas turbines for power generation, flashback of the turbulent flame by propagation through the low velocity boundary layers in the premixing region is an operationally dangerous event. Predictive models that could accurately capture the onset and subsequent behavior of flashback would be indispensable in gas turbine design. The large eddy simulation (LES) approach is used here to model this process. The goal is to examine the validity of a probability distribution function (PDF) based model in the context of a lean premixed flame in a confined geometry. A turbulent swirling flow geometry and corresponding experimental data is used for validation. A suite of LES calculations are performed on a large unstructured mesh for varying fuel compositions operating at several equivalence ratios. It is shown that the PDF based method can predict some statistical properties of the flame front, with improvement over other models in the same application.

Monolithic fuel injector and related manufacturing method

DOEpatents

Ziminsky, Willy Steve [Greenville, SC; Johnson, Thomas Edward [Greenville, SC; Lacy, Benjamin [Greenville, SC; York, William David [Greenville, SC; Stevenson, Christian Xavier [Greenville, SC

2012-05-22

A monolithic fuel injection head for a fuel nozzle includes a substantially hollow vesicle body formed with an upstream end face, a downstream end face and a peripheral wall extending therebetween, an internal baffle plate extending radially outwardly from a downstream end of the bore, terminating short of the peripheral wall, thereby defining upstream and downstream fuel plenums in the vesicle body, in fluid communication by way of a radial gap between the baffle plate and the peripheral wall. A plurality of integral pre-mix tubes extend axially through the upstream and downstream fuel plenums in the vesicle body and through the baffle plate, with at least one fuel injection hole extending between each of the pre-mix tubes and the upstream fuel plenum, thereby enabling fuel in the upstream plenum to be injected into the plurality of pre-mix tubes. The fuel injection head is formed by direct metal laser sintering.

Examination of ionic wind and cathode sheath effects in a E-field premixed flame with ion density measurements

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

Jacobs, Stewart V., E-mail: svj0001@uah.edu; Xu, Kunning G., E-mail: gabe.xu@uah.edu

2016-04-15

The effect of the ionic wind on a premixed methane-air flame under a DC electric field is studied via mapping of the ion density with Langmuir probes. Ion densities were observed to increase near the burner with increasing electrode voltage up to 6 kV. Past this electrode supply voltage, ion densities ceased increasing and began to decline in some locations within the premixed flame. The increased ion density is caused by an increase in ionic wind force and cathode sheath thickness. The plateau in density is due to the cathode sheath fully encompassing the flame front which is the ion source,more » thereby collecting all ions in the flame. The spatial density data support the ionic wind hypothesis and provide further explanation of its limits based on the plasma sheath.« less

PREMIXED FLAME PROPAGATION AND MORPHOLOGY IN A CONSTANT VOLUME COMBUSTION CHAMBER

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

Hariharan, A; Wichman, IS

2014-06-04

This work presents an experimental and numerical investigation of premixed flame propagation in a constant volume rectangular channel with an aspect ratio of six (6) that serves as a combustion chamber. Ignition is followed by an accelerating cusped finger-shaped flame-front. A deceleration of the flame is followed by the formation of a "tulip"-shaped flame-front. Eventually, the flame is extinguished when it collides with the cold wall on the opposite channel end. Numerical computations are performed to understand the influence of pressure waves, instabilities, and flow field effects causing changes to the flame structure and morphology. The transient 2D numerical simulationmore » results are compared with transient 3D experimental results. Issues discussed are the appearance of oscillatory motions along the flame front and the influences of gravity on flame structure. An explanation is provided for the formation of the "tulip" shape of the premixed flame front.« less

Commercial premixed parenteral nutrition: Is it right for your institution?

PubMed

Miller, Sarah J

2009-01-01

Two-compartment premixed parenteral nutrition (PN) products are heavily promoted in the United States. These products may present safety advantages over PN solutions mixed by a local pharmacy, although clinical data to support this assertion are scarce. Multicompartment products can be labor-saving for pharmacy and therefore may be cost-effective for some institutions. Before adopting such products for use, an institution must determine that standardized PN solutions are acceptable for many or most of their patients compared with customized PN compounded specifically for individual patients. A larger selection of premixed products is available in Europe and some other parts of the world compared with the United States. Availability of a broader selection of products in the United States, including 3-compartment bags and a wider range of macronutrient concentrations and volumes, may make the use of such products more desirable in the future.

Premixed direct injection nozzle

DOEpatents

Zuo, Baifang [Simpsonville, SC; Johnson, Thomas Edward [Greer, SC; Lacy, Benjamin Paul [Greer, SC; Ziminsky, Willy Steve [Simpsonville, SC

2011-02-15

An injection nozzle having a main body portion with an outer peripheral wall is disclosed. The nozzle includes a plurality of fuel/air mixing tubes disposed within the main body portion and a fuel flow passage fluidly connected to the plurality of fuel/air mixing tubes. Fuel and air are partially premixed inside the plurality of the tubes. A second body portion, having an outer peripheral wall extending between a first end and an opposite second end, is connected to the main body portion. The partially premixed fuel and air mixture from the first body portion gets further mixed inside the second body portion. The second body portion converges from the first end toward said second end. The second body portion also includes cooling passages that extend along all the walls around the second body to provide thermal damage resistance for occasional flame flash back into the second body.

The species-area relationship, self-similarity, and the true meaning of the z-value.

PubMed

Tjørve, Even; Tjørve, Kathleen M Calf

2008-12-01

The power model, S= cA(z) (where S is number of species, A is area, and c and z are fitted constants), is the model most commonly fitted to species-area data assessing species diversity. We use the self-similarity properties of this model to reveal patterns implicated by the z parameter. We present the basic arithmetic leading both to the fraction of new species added when two areas are combined and to species overlap between two areas of the same size, given a continuous sampling scheme. The fraction of new species resulting from expansion of an area can be expressed as alpha(z)-1, where alpha is the expansion factor. Consequently, z-values can be converted to a scale-invariant species overlap between two equally sized areas, since the proportion of species in common between the two areas is 2-2(z). Calculating overlap when adding areas of the same size reveals the intrinsic effect of distance assumed by the bisectional scheme. We use overlap area relationships from empirical data sets to illustrate how answers to the single large or several small reserves (SLOSS) question vary between data sets and with scale. We conclude that species overlap and the effect of distance between sample areas or isolates should be addressed when discussing species area relationships, and lack of fit to the power model can be caused by its assumption of a scale-invariant overlap relationship.

Cherenkov detectors for spatial imaging applications using discrete-energy photons

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

Rose, Paul B.; Erickson, Anna S., E-mail: erickson@gatech.edu

Cherenkov detectors can offer a significant advantage in spatial imaging applications when excellent timing response, low noise and cross talk, large area coverage, and the ability to operate in magnetic fields are required. We show that an array of Cherenkov detectors with crude energy resolution coupled with monochromatic photons resulting from a low-energy nuclear reaction can be used to produce a sharp image of material while providing large and inexpensive detector coverage. The analysis of the detector response to relative transmission of photons with various energies allows for reconstruction of material's effective atomic number further aiding in high-Z material identification.

Testing of felt-ceramic materials for combustor applications

NASA Technical Reports Server (NTRS)

Venkat, R. S.; Roffe, G.

1983-01-01

The feasibility of using composite felt ceramic materials as combustor liners was experimentally studied. The material consists of a porous felt pad sandwiched between a layer of ceramic and one of solid metal. Flat, rectangular test panels, which encompassed several design variations of the basic composite material, were tested, two at a time, in a premixed gas turbine combustor as sections of the combustor wall. Tests were conducted at combustor inlet conditions of 0.5 MPa and 533 K with a reference velocity of 25 m/s. The panels were subjected to a hot gas temperature of 2170 K with 1% of the total airflow used to film cool the ceramic surface of the test panel. In general, thin ceramic layers yield low ceramic stress levels with high felt ceramic interface temperatures. On the other hand, thick ceramic layers result in low felt ceramic interface temperatures but high ceramic stress levels. Extensive thermal cycling appears to cause material degradation, but for a limited number of cycles, the survivability of felt ceramic materials, even under extremely severe combustor operating conditions, was conclusively demonstrated.

Low and medium heating value coal gas catalytic combustor characterization

NASA Technical Reports Server (NTRS)

Schwab, J. A.

1982-01-01

Catalytic combustion with both low and medium heating value coal gases obtained from an operating gasifier was demonstrated. A practical operating range for efficient operation was determined, and also to identify potential problem areas were identified for consideration during stationary gas turbine engine design. The test rig consists of fuel injectors, a fuel-air premixing section, a catalytic reactor with thermocouple instrumentation and a single point, water cooled sample probe. The test rig included inlet and outlet transition pieces and was designed for installation into an existing test loop.

Effectiveness of ready-to-use therapeutic food compared to a corn/soy-blend-based pre-mix for the treatment of childhood moderate acute malnutrition in Niger.

PubMed

Nackers, Fabienne; Broillet, France; Oumarou, Diakité; Djibo, Ali; Gaboulaud, Valérie; Guerin, Philippe J; Rusch, Barbara; Grais, Rebecca F; Captier, Valérie

2010-12-01

Standard nutritional treatment of moderate acute malnutrition (MAM) relies on fortified blended flours though their importance to treat this condition is a matter of discussion. With the newly introduced World Health Organization growth standards, more children at an early stage of malnutrition will be treated following the dietary protocols as for severe acute malnutrition, including ready-to-use therapeutic food (RUTF). We compared the effectiveness of RUTF and a corn/soy-blend (CSB)-based pre-mix for the treatment of MAM in the supplementary feeding programmes (SFPs) supported by Médecins Sans Frontières, located in the Zinder region (south of Niger). Children measuring 65 to <110 cm, newly admitted with MAM [weight-for-height (WHM%) between 70% and <80% of the NCHS median] were randomly allocated to receive either RUTF (Plumpy'Nut®, 1000 kcal day(-1)) or a CSB pre-mix (1231 kcal day(-1)). Other interventions were similar in both groups (e.g. weekly family ration and ration at discharge). Children were followed weekly up to recovery (WHM% ≥ 85% for 2 consecutive weeks). In total, 215 children were recruited in the RUTF group and 236 children in the CSB pre-mix group with an overall recovery rate of 79.1 and 64.4%, respectively (p < 0.001). There was no evidence for a difference between death, defaulter and non-responder rates. More transfers to the inpatient Therapeutic Feeding Centre (I-TFC) were observed in the CSB pre-mix group (19.1%) compared to the RUTF group (9.3%) (p = 0.003). The average weight gain up to discharge was 1.08 g kg(-1) day(-1) higher in the RUTF group [95% confidence interval: 0.46-1.70] and the length of stay was 2 weeks shorter in the RUTF group (p < 0.001). For the treatment of childhood MAM in Niger, RUTF resulted in a higher weight gain, a higher recovery rate, a shorter length of stay and a lower transfer rate to the I-TFC compared to a CSB pre-mix. This might have important implications on the efficacy and the quality of SFPs.

PantherPix hybrid pixel γ-ray detector for radio-therapeutic applications

NASA Astrophysics Data System (ADS)

Neue, G.; Benka, T.; Havránek, M.; Hejtmánek, M.; Janoška, Z.; Kafka, V.; Korchak, O.; Lednický, D.; Marčišovská, M.; Marčišovský, M.; Popule, J.; Şmarhák, J.; Şvihra, P.; Tomášek, L.; Vrba, V.; Konček, O.; Semmler, M.

2018-02-01

This work focuses on the design of a semiconductor pixelated γ-ray camera with a pixel size of 1 mm2. The cost of semiconductor manufacturing is mainly driven by economies of scale, which makes silicon the cheapest semiconductor material due to its widespread utilization. The energy of γ-photons used in radiation therapy are in a range, in which the dominant interaction mechanism is Compton scattering in every conceivable sensor material. Since the Compton scattering cross section is linearly dependent upon Z, it is less rewarding to utilize high Z sensor materials, than it is in the case of X-ray detectors (X-rays interact also via the photoelectric effect whose cross section scales proportional to Zn, where n is ≈ 4,5). For the stated reasons it was decided to use the low Z material silicon (Z = 14) despite its worse detection efficiency. The proposed detector is designed as a portal detector to be used in radiation cancer therapy. The purpose of the detector is to ensure correct patient alignment, spatial dose monitoring and to provide the feedback necessary for an emergency shutdown should the spatial dose rate profile deviate from the treatment plan. Radiation therapy equipment is complex and thus failure prone and the consequences of malfunction are often life threatening. High spatial resolution and high detection efficiency are not a high design priority. The detector design priorities are focused up on radiation hardness, robustness and the ability to cover a large area cost efficiently. The quintessential idea of the PanterPix detector exploits the relaxed spatial resolution requirement to achieve the stated goals. The detector is composed of submodules, each submodule consisting of a Si sensor with an array of fully depleted detection diodes and 8 miniature custom design readout ASICs collecting and measuring the minuscule charge packets generated due to ionization in the PN junctions.

In situ measurement of low-Z material coating thickness on high Z substrate for tokamaks.

PubMed

Mueller, D; Roquemore, A L; Jaworski, M; Skinner, C H; Miller, J; Creely, A; Raman, P; Ruzic, D

2014-11-01

Rutherford backscattering of energetic particles can be used to determine the thickness of a coating of a low-Z material over a heavier substrate. Simulations indicate that 5 MeV alpha particles from an (241)Am source can be used to measure the thickness of a Li coating on Mo tiles between 0.5 and 15 μm thick. Using a 0.1 mCi source, a thickness measurement can be accomplished in 2 h of counting. This technique could be used to measure any thin, low-Z material coating (up to 1 mg/cm(2) thick) on a high-Z substrate, such as Be on W, B on Mo, or Li on Mo. By inserting a source and detector on a moveable probe, this technique could be used to provide an in situ measurement of the thickness of Li coating on NSTX-U Mo tiles. A test stand with an alpha source and an annular solid-state detector was used to investigate the measurable range of low-Z material thicknesses on Mo tiles.

In situ measurement of low-Z material coating thickness on high Z substrate for tokamaks

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

Mueller, D., E-mail: dmueller@pppl.gov; Roquemore, A. L.; Jaworski, M.

Rutherford backscattering of energetic particles can be used to determine the thickness of a coating of a low-Z material over a heavier substrate. Simulations indicate that 5 MeV alpha particles from an {sup 241}Am source can be used to measure the thickness of a Li coating on Mo tiles between 0.5 and 15 μm thick. Using a 0.1 mCi source, a thickness measurement can be accomplished in 2 h of counting. This technique could be used to measure any thin, low-Z material coating (up to 1 mg/cm{sup 2} thick) on a high-Z substrate, such as Be on W, B on Mo, or Limore » on Mo. By inserting a source and detector on a moveable probe, this technique could be used to provide an in situ measurement of the thickness of Li coating on NSTX-U Mo tiles. A test stand with an alpha source and an annular solid-state detector was used to investigate the measurable range of low-Z material thicknesses on Mo tiles.« less

Studies of Flame Structure in Microgravity

NASA Technical Reports Server (NTRS)

Law, C. K.; Sung, C. J.; Zhu, D. L.

1997-01-01

The present research endeavor is concerned with gaining fundamental understanding of the configuration, structure, and dynamics of laminar premixed and diffusion flames under conditions of negligible effects of gravity. Of particular interest is the potential to establish and hence study the properties of spherically- and cylindrically-symmetric flames and their response to external forces not related to gravity. For example, in an earlier experimental study of the burner-stabilized cylindrical premixed flames, the possibility of flame stabilization through flow divergence was established, while the resulting one-dimensional, adiabatic, stretchless flame also allowed an accurate means of determining the laminar flame speeds of combustible mixtures. We have recently extended our studies of the flame structure in microgravity along the following directions: (1) Analysis of the dynamics of spherical premixed flames; (2) Analysis of the spreading of cylindrical diffusion flames; (3) Experimental observation of an interesting dual luminous zone structure of a steady-state, microbuoyancy, spherical diffusion flame of air burning in a hydrogen/methane mixture environment, and its subsequent quantification through computational simulation with detailed chemistry and transport; (4) Experimental quantification of the unsteady growth of a spherical diffusion flame; and (5) Computational simulation of stretched, diffusionally-imbalanced premixed flames near and beyond the conventional limits of flammability, and the substantiation of the concept of extended limits of flammability. Motivation and results of these investigations are individually discussed.

Interactions of short-acting, intermediate-acting and pre-mixed human insulins with free radicals--Comparative EPR examination.

PubMed

Olczyk, Paweł; Komosinska-Vassev, Katarzyna; Ramos, Paweł; Mencner, Łukasz; Olczyk, Krystyna; Pilawa, Barbara

2015-07-25

Electron paramagnetic resonance (EPR) spectroscopy was used to examine insulins interactions with free radicals. Human recombinant DNA insulins of three groups were studied: short-acting insulin (Insuman Rapid); intermediate-acting insulins (Humulin N, Insuman Basal), and pre-mixed insulins (Humulin M3, Gensulin M50, Gensulin M40, Gensulin M30). The aim of an X-band (9.3GHz) study was comparative analysis of antioxidative properties of the three groups of human insulins. DPPH was used as a stable free radical model. Amplitudes of EPR lines of DPPH as the paramagnetic free radical reference, and DPPH interacting with the individual tested insulins were compared. For all the examined insulins kinetics of their interactions with free radicals up to 60 min were obtained. The strongest interactions with free radicals were observed for the short-acting insulin - Insuman Rapid. The lowest interactions with free radicals were characteristic for intermediate-acting insulin - Insuman Basal. The pre-mixed insulins i.e. Humulin M3 and Gensulin M50 revealed the fastest interactions with free radicals. The short acting, intermediate acting and premixed insulins have been found to be effective agents in reducing free radical formation in vitro and should be further considered as potential useful tools in attenuation of oxidative stress in diabetic patients. Copyright © 2015 Elsevier B.V. All rights reserved.

Premixed Turbulent Flame Propagation in Microgravity

NASA Technical Reports Server (NTRS)

Menon, Suresh

1999-01-01

A combined numerical-experimental study has been carried out to investigate the structure and propagation characteristics of turbulent premixed flames with and without the influence of buoyancy. Experimentally, the premixed flame characteristics are studied in the wrinkled regime using a Couette flow facility and an isotropic flow facility in order to resolve the scale of flame wrinkling. Both facilities were chosen for their ability to achieve sustained turbulence at low Reynolds number. This implies that conventional diagnostics can be employed to resolve the smallest scales of wrinkling. The Couette facility was also built keeping in mind the constraints imposed by the drop tower requirements. Results showed that the flow in this Couette flow facility achieves full-developed turbulence at low Re and all turbulence statistics are in good agreement with past measurements on large-scale facilities. Premixed flame propagation studies were then carried out both using the isotropic box and the Couette facility. Flame imaging showed that fine scales of wrinkling occurs during flame propagation. Both cases in Ig showed significant buoyancy effect. To demonstrate that micro-g can remove this buoyancy effect, a small drop tower was built and drop experiments were conducted using the isotropic box. Results using the Couette facility confirmed the ability to carry out these unique reacting flow experiments at least in 1g. Drop experiments at NASA GRC were planned but were not completed due to termination of this project.

Experimental study on a comparison of typical premixed combustible gas-air flame propagation in a horizontal rectangular closed duct.

PubMed

Jin, Kaiqiang; Duan, Qiangling; Liew, K M; Peng, Zhongjing; Gong, Liang; Sun, Jinhua

2017-04-05

Research surrounding premixed flame propagation in ducts has a history of more than one hundred years. Most previous studies focus on the tulip flame formation and flame acceleration in pure gas fuel-air flame. However, the premixed natural gas-air flame may show different behaviors and pressure dynamics due to its unique composition. Natural gas, methane and acetylene are chosen here to conduct a comparison study on different flame behaviors and pressure dynamics, and to explore the influence of different compositions on premixed flame dynamics. The characteristics of flame front and pressure dynamics are recorded using high-speed schlieren photography and a pressure transducer, respectively. The results indicate that the compositions of the gas mixture greatly influence flame behaviors and pressure. Acetylene has the fastest flame tip speed and the highest pressure, while natural gas has a faster flame tip speed and higher pressure than methane. The Bychkov theory for predicting the flame skirt motion is verified, and the results indicate that the experimental data coincide well with theory in the case of equivalence ratios close to 1.00. Moreover, the Bychkov theory is able to predict flame skirt motion for acetylene, even outside of the best suitable expansion ratio range of 6

Soot Formation in Laminar Premixed Methane/Oxygen Flames at Atmospheric Pressure

NASA Technical Reports Server (NTRS)

Xu, F.; Lin, K.-C.; Faeth, G. M.

1998-01-01

Flame structure and soot formation were studied within soot-containing laminar premixed mc1hane/oxygen flames at atmospheric pressure. The following measurements were made: soot volume fractions by laser extinction, soot temperatures by multiline emission, gas temperatures (where soot was absent) by corrected fine-wire thermocouples, soot structure by thermophoretic sampling and transmission electron microscope (TEM), major gas species concentrations by sampling and gas chromatography, and gas velocities by laser velocimetry. Present measurements of gas species concentrations were in reasonably good agreement with earlier measurements due to Ramer et al. as well as predictions based on the detailed mechanisms of Frenklach and co-workers and Leung and Lindstedt: the predictions also suggest that H atom concentrations are in local thermodynamic equilibrium throughout the soot formation region. Using this information, it was found that measured soot surface growth rates could be correlated successfully by predictions based on the hydrogen-abstraction/carbon-addition (HACA) mechanisms of both Frenklach and co-workers and Colket and Hall, extending an earlier assessment of these mechanisms for premixed ethylene/air flames to conditions having larger H/C ratios and acetylene concentrations. Measured primary soot particle nucleation rates were somewhat lower than the earlier observations for laminar premixed ethylene/air flames and were significantly lower than corresponding rates in laminar diffusion flames. for reasons that still must be explained.

Soot Formation in Laminar Premixed Methane/Oxygen Flames at Atmospheric Pressure. Appendix H

NASA Technical Reports Server (NTRS)

Xu, F.; Lin, K.-C.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2001-01-01

Flame structure and soot formation were studied within soot-containing laminar premixed methanefoxygen flames at atmospheric pressure. The following measurements were made: soot volume fractions by laser extinction, soot temperatures by multiline emission, gas temperatures (where soot was absent) by corrected fine-wire thermocouples, soot structure by thermophoretic sampling and transmission electron microscope (TEM), major gas species concentrations by sampling and gas chromatography, and gas velocities by laser velocimetry. Present measurements of gas species concentrations were in reasonably good agreement with earlier measurements due to Ramer et al. as well as predictions based on the detailed mechanisms of Frenklach and co-workers and Leung and Lindstedt; the predictions also suggest that H atom concentrations are in local thermodynamic equilibrium throughout the soot formation region. Using this information, it was found that measured soot surface growth rates could be correlated successfully by predictions based on the hydrogenabstraction/carbon-addition (HACA) mechanisms of both Frenklach and co-workers and Colket and Hall, extending an earlier assessment of these mechanisms for premixed ethylene/air flames to conditions having larger H/C ratios and acetylene concentrations. Measured primary soot particle nucleation rates were somewhat lower than the earlier observations for laminar premixed ethylene/air flames and were significantly lower than corresponding rates in laminar diffusion flames, for reasons that still must be explained.

The influence of cavity parameters on the combustion oscillation in a single-side expansion scramjet combustor

NASA Astrophysics Data System (ADS)

Ouyang, Hao; Liu, Weidong; Sun, Mingbo

2017-08-01

Cavity has been validated to be efficient flameholders for scramjet combustors, but the influence of its parameters on the combustion oscillation in scramjet combustor has barely been studied. In the present work, a series of experiments focusing on this issue have been carried out. The influence of flameholding cavity position, its length to depth ratio L/D and aft wall angle θ and number on ethylene combustion oscillation characteristics in scramjet combustor has been researched. The obtained experimental results show that, as the premixing distance between ethylene injector and flameholding cavity varies, the ethylene combustion flame will take on two distinct forms, small-amplitude high frequency fluctuation, and large-amplitude low frequency oscillation. The dominant frequency of the large-amplitude combustion oscillation is in inverse proportion to the pre-mixing distance. Moreover, the influence of cavity length to depth ratio and the aft wall angleθexists diversity when the flameholding cavity position is different and can be recognized as unnoticeable compared to the impact of the premixing distance. In addition, we also find that, when the premixing distance is identical and sufficient, increasing the number of tandem flameholding cavities can change the dominant frequency of combustion oscillation hardly, let alone avoid the combustion oscillation. It is believed that the present investigation will provide a useful reference for the design of the scramjet combustor.

Structural Evolution and Atom Clustering in β-SiAlON: β-Si 6–z Al z O z N 8–z

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

Cozzan, Clayton; Griffith, Kent J.; Laurita, Geneva

2017-02-06

SiAlON ceramics, solid solutions based on the Si 3N 4 structure, are important, lightweight structural materials with intrinsically high strength, high hardness, and high thermal and chemical stability. Described by the chemical formula β-Si 6–zAl zO zN 8–z, from a compositional viewpoint, these materials can be regarded as solid solutions between Si 3N 4 and Al 3O 3N. A key aspect of the structural evolution with increasing Al and O (z in the formula) is to understand how these elements are distributed on the β-Si 3N 4 framework. The average and local structural evolution of highly phase-pure samples of β-Simore » 6–zAl zO zN 8–z with z = 0.050, 0.075, and 0.125 are studied here, using a combination of X-ray diffraction, NMR studies, and density functional theory calculations. Synchrotron X-ray diffraction establishes sample purity and indicates subtle changes in the average structure with increasing Al content in these compounds. Solid-state magic-angle-spinning 27Al NMR experiments, coupled with detailed ab initio calculations of NMR spectra of Al in different AlO qN 4–q tetrahedra (0 ≤ q ≤ 4), reveal a tendency of Al and O to cluster in these materials. Independently, the calculations suggest an energetic preference for Al–O bond formation, instead of a random distribution, in the β-SiAlON system.« less

Direct numerical simulations and spectral modeling of premixed turbulent combustion in the flamelet regime

NASA Astrophysics Data System (ADS)

Ulitsky, Mark

1997-11-01

A model for premixed turbulent combustion in the so called 'flamelet regime' has been developed. This regime, often referred to as the fast chemistry or high Damkohler number regime, is characterized by turbulent length and time scales that are much larger and slower than the flame thickness and reaction time scales respectively. There is currently great interest in trying to better understand flamelet combustion, as many practical devices (i.e., spark ignition engines, gas turbines, etc.) have been found to operate in this regime. Before a model could be developed however, it was first necessary to ascertain which part of the turbulence (either the nearly Gaussian background turbulence or the tube-like coherent vortical structures) was responsible for the multi-scale wrinkling of the flame surface. This question motivated a DNS study of flames passing through both structure containing the structure free isotropic turbulence. After it was determined that the presence of the coherent structures was merely ancillary in terms of increasing the surface area of the flame, a spectral model based on the EDQNM (Eddy Damped Quasi Normal Markovian) theory of turbulence was developed. This theory implicitly assumes that joint distributions of the fluctuating velocity components are nearly Gaussian, and as only spectra are transported in this model, there is no direct information about any of the coherent structures which might be embedded within the flow field. One of the advantages of this model is that both the Reynolds number and the ratio of the rms fluctuating velocity to the laminar flame speed can be varied independently. To test the model's ability to capture the nonlinear dynamics of the governing field equation a DNS study was performed and both steady-state and transient single- and two-point statistics were compared. Finally, the model was compared to two-point experimental measurements taken from a lean premixed methane-air flame.

Rare earth-iron magnetostrictive materials and devices using these materials

DOEpatents

Savage, Howard T.; Clark, Arthur E.; McMasters, O. Dale

1981-12-29

Grain-oriented polycrystalline or single crystal magnetostrictive materials n the general formula Tb.sub.x Dy.sub.1-x Fe.sub.2-w, Tb.sub.x Ho.sub.1-x Fe.sub.2-w, Sm.sub.x Dy.sub.1-x Fe.sub.x-w, Sm.sub.x Ho.sub.1-x Fe.sub.2-w, Tb.sub.x Ho.sub.y Dy.sub.z Fe.sub.2-w, or Sm.sub.x Ho.sub.y Dy.sub.z Fe.sub.2-w, wherein O.ltoreq.w.ltoreq.0.20, and x+y+z=1. X, y, and z are selected to maximize the magnetostrictive effect and the magnetomechanical coupling coefficient K.sub.33. These material may be used in magnetostrictive transducers, delay lines, variable frequency resonators, and filters.

Electrode materials for rechargeable battery

DOEpatents

Johnson, Christopher; Kang, Sun-Ho

2015-09-08

A positive electrode is disclosed for a non-aqueous electrolyte lithium rechargeable cell or battery. The electrode comprises a lithium containing material of the formula Na.sub.yLi.sub.xNi.sub.zMn.sub.1-z-z'M.sub.z'O.sub.d, wherein M is a metal cation, x+y>1, 0

Poly- Versus Mono-Energetic Dual-Spectrum Non-Intrusive Inspection of Cargo Containers

NASA Astrophysics Data System (ADS)

Martz, Harry E.; Glenn, Steven M.; Smith, Jerel A.; Divin, Charles J.; Azevedo, Stephen G.

2017-07-01

In this paper, based on an invited talk at SORMA (May 2016), we present an overview of x-ray sources, detectors and system configurations for non-intrusive inspection (NII) of cargo containers. Our emphasis is on dual-energy x-ray NII for detecting high-atomic-number (Z ≥ 72) materials such as tungsten shielding and special nuclear materials (SNM). Standard single-energy (MeV and above) x-rays needed to penetrate and image cargo provide little SNM contrast, whereas dual-energy x-ray NII is demonstrated as a way to improve the selectivity of materials with Z<;72 vs. those with Z ≥ 72. For two possible dual-energy x-ray source technologies - polyenergetic dual-energy (PDE) and quasi-monoenergetic x-ray sources (QMXS) - we investigate their trade-offs and future prospects using experimental and simulated results. The reduced scatter and larger separation of low- and high-energy photons provided by QMXS offers improved high-Z material contrast, but practical considerations such as flux and pulse rate need to be solved before making a deployable system. Straight-ray simulations show factor of four increases in contrast for QMXS over PDE scans of tin (Z=50) and iron (Z=26) relative to a uranium plate (Z=92) behind 20 cm of iron simulated cargo.

Stochastic modeling of unsteady extinction in turbulent non-premixed combustion

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

Lackmann, T.; Hewson, J. C.; Knaus, R. C.

Turbulent fluctuations of the scalar dissipation rate have a major impact on extinction in non-premixed combustion. Recently, an unsteady extinction criterion has been developed (Hewson, 2013) that predicts extinction dependent on the duration and the magnitude of dissipation rate fluctuations exceeding a critical quenching value; this quantity is referred to as the dissipation impulse. Furthermore, the magnitude of the dissipation impulse corresponding to unsteady extinction is related to the difficulty with which a flamelet is exintguished, based on the steady-state S-curve.

Stochastic modeling of unsteady extinction in turbulent non-premixed combustion

DOE PAGES

Lackmann, T.; Hewson, J. C.; Knaus, R. C.; ...

2016-07-19

Turbulent fluctuations of the scalar dissipation rate have a major impact on extinction in non-premixed combustion. Recently, an unsteady extinction criterion has been developed (Hewson, 2013) that predicts extinction dependent on the duration and the magnitude of dissipation rate fluctuations exceeding a critical quenching value; this quantity is referred to as the dissipation impulse. Furthermore, the magnitude of the dissipation impulse corresponding to unsteady extinction is related to the difficulty with which a flamelet is exintguished, based on the steady-state S-curve.

Incipient Soot Formation in Rich Partially Premixed Flames under High Pressure Conditions of Relevance to Compression-Ignition Engines

DTIC Science & Technology

2017-09-09

chemically. Such flames were systematically studied by measuring temperature, species 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13...pressure) but are still well suited to quantitative diagnostics; 2) Study soot inception by measuring gaseous soot precursors and focusing on the gas-to...downstream across an envelope diffusion flame that is formed between the products of the rich premixed flame and the oxidizer. To mimic this situation, a

Pulsed jet combustion generator for non-premixed charge engines

DOEpatents

Oppenheim, A. K.; Stewart, H. E.

1990-01-01

A device for introducing fuel into the head space of cylinder of non-premixed charge (diesel) engines is disclosed, which distributes fuel in atomized form in a plume, whose fluid dynamic properties are such that the compression heated air in the cylinder head space is entrained into the interior of the plume where it is mixed with and ignites the fuel in the plume interior, to thereby control combustion, particularly by use of a multiplicity of individually controllable devices per cylinder.

Modeling of turbulent chemical reaction

NASA Technical Reports Server (NTRS)

Chen, J.-Y.

1995-01-01

Viewgraphs are presented on modeling turbulent reacting flows, regimes of turbulent combustion, regimes of premixed and regimes of non-premixed turbulent combustion, chemical closure models, flamelet model, conditional moment closure (CMC), NO(x) emissions from turbulent H2 jet flames, probability density function (PDF), departures from chemical equilibrium, mixing models for PDF methods, comparison of predicted and measured H2O mass fractions in turbulent nonpremixed jet flames, experimental evidence of preferential diffusion in turbulent jet flames, and computation of turbulent reacting flows.

Attractiveness of a Four-component Pheromone Blend to Male Navel Orangeworm Moths

PubMed Central

Kanno, Hiroo; Kuenen, L. P. S.; Klingler, Kimberly A.; Millar, Jocelyn G.

2010-01-01

The attractiveness to male navel orangeworm moth, Amyelois transitella, of various combinations of a four-component pheromone blend was measured in wind-tunnel bioassays. Upwind flight along the pheromone plume and landing on the odor source required the simultaneous presence of two components, (11Z,13Z)-hexadecadienal and (3Z,6Z,9Z,12Z,15Z)-tricosapentaene, and the addition of either (11Z,13Z)-hexadecadien-1-ol or (11Z,13E)-hexadecadien-1-ol. A mixture of all four components produced the highest levels of rapid source location and source contact. In wind-tunnel assays, males did not seem to distinguish among a wide range of ratios of any of the three components added to (11Z,13Z)-hexadecadienal. Dosages of 10 and 100 ng of the 4-component blend produced higher levels of source location than dosages of 1 and 1,000 ng. Electronic supplementary material The online version of this article (doi:10.1007/s10886-010-9799-x) contains supplementary material, which is available to authorized users. PMID:20473710

Testing fireproof materials in a combustion chamber

NASA Astrophysics Data System (ADS)

Kulhavy, Petr; Martinec, Tomas; Novak, Ondrej; Petru, Michal; Srb, Pavel

This article deals with a prototype concept, real experiment and numerical simulation of a combustion chamber, designed for testing fire resistance some new insulating composite materials. This concept of a device used for testing various materials, providing possibility of monitoring temperatures during controlled gas combustion. As a fuel for the combustion process propane butane mixture has been used and also several kinds of burners with various conditions of inlet air (forced, free) and fuel flows were tested. The tested samples were layered sandwich materials based on various materials or foams, used as fillers in fire shutters. The temperature distribution was measured by using thermocouples. A simulation of whole concept of experimental chamber has been carried out as the non-premixed combustion process in the commercial final volume sw Pyrosim. The result was to design chamber with a construction suitable, according to the international standards, achieve the required values (temperature in time). Model of the combustion based on a stoichiometric defined mixture of gas and the tested layered samples showed good conformity with experimental results - i.e. thermal distribution inside and heat release rate that has gone through the sample.

EVALUATION OF FABRIC MEMBRANES FOR USE IN SALTSTONE DRAIN WATER SYSTEM

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

Pickenheim, B.; Miller, D.; Burket, P.

2012-03-08

Saltstone Disposal Unit 2 contains a sheet drain fabric intended to separate solids from drain water to be returned to the Salt Feed Tank. A similar system installed in Vault 4 appears to be ineffective in keeping solids out of the drain water return lines. Waste Solidification Engineering is considering installation of an additional fabric membrane to supplement the existing sheet drain in SDU 2. Amerdrain 200 is the product currently installed in SDU 2. This product is no longer available, so Sitedrain 94 was used as the replacement product in this testing. Fabrics with apparent opening sizes of 10,more » 25, 50 and 100 microns were evaluated. These fabrics were evaluated under three separate test conditions, a water flow test, a solids retention test and a grout pour test. A flow test with water showed that installation of an additional filter layer will predictably reduce the theoretical flux through the sheet drain. The manufacturer reports the flux for Sitedrain 94 as 150 gpm/ft{sup 2} by ASTM D-4491. This compares reasonably well with the 117 gpm/ft{sup 2} obtained in this testing. A combination of the 10 micron fabric with Sitedrain 94 could be expected to decrease flux by about 10 times as compared to Sitedrain 94 alone. The different media were used to filter a slag and fly ash mixture from water. Slag historically has the smallest nominal particle size of the premix components. Cement was omitted from the test because of its reactivity with water would prohibit accurately particle size measurements of the filtered samples. All four media sizes were able to remove greater than 95% of particles larger than 100 microns from the slurry. The smaller opening sizes were increasingly effective in removing more particles. The 10 micron filter captured 15% of the total amount of solids used in the test. This result implies that some insoluble particles may still be able to enter the drain water collection system, although the overall solids rejection is significantly improved over the current design. Test boxes were filled with grout to evaluate the performance of the sheet drain and fabrics in a simulated vault environment. All of the tests produced a similar amount of drain water, between 8-11% of the amount of water in the mix, which is expected with the targeted formulation. All of the collected drain waters contained some amount of solids, although the 10 micron filter did not appear to allow any premix materials to pass through. The solids collected from this box are believed to consist of calcium carbonate based on one ICP-AES measurement. Any of the four candidate fabrics would be an improvement over the sheet drain alone relative to solids removal. The 10 micron fabric is the only candidate that stopped all premix material from passing. The 10 micron fabric will also cause the largest decrease in flux. This decrease in flux was not enough to inhibit the total amount of drain water removed, but may lead to increased time to remove standing water prior to subsequent pours in the facility. The acceptability of reduced liquid flux through the 10 micron fabric will depend on the amount of excess water to be removed, the time available for water removal and the total area of fabric installed at the disposal cell.« less

High Thermal Conductivity NARloy-Z-Diamond Composite Combustion Chamber Liner For Advanced Rocket Engines

NASA Technical Reports Server (NTRS)

Bhat, Biliyar N.; Ellis, David; Singh, Jogender

2014-01-01

Advanced high thermal conductivity materials research conducted at NASA Marshall Space Flight Center (MSFC) with state of the art combustion chamber liner material NARloy-Z showed that its thermal conductivity can be increased significantly by adding diamond particles and sintering it at high temperatures. For instance, NARloy-Z containing 40 vol. percent diamond particles, sintered at 975C to full density by using the Field assisted Sintering Technology (FAST) showed 69 percent higher thermal conductivity than baseline NARloy-Z. Furthermore, NARloy-Z-40vol. percent D is 30 percent lighter than NARloy-Z and hence the density normalized thermal conductivity is 140 percent better. These attributes will improve the performance and life of the advanced rocket engines significantly. By one estimate, increased thermal conductivity will directly translate into increased turbopump power up to 2X and increased chamber pressure for improved thrust and ISP, resulting in an expected 20 percent improvement in engine performance. Follow on research is now being conducted to demonstrate the benefits of this high thermal conductivity NARloy-Z-D composite for combustion chamber liner applications in advanced rocket engines. The work consists of a) Optimizing the chemistry and heat treatment for NARloy-Z-D composite, b) Developing design properties (thermal and mechanical) for the optimized NARloy-Z-D, c) Fabrication of net shape subscale combustion chamber liner, and d) Hot fire testing of the liner for performance. FAST is used for consolidating and sintering NARlo-Z-D. The subscale cylindrical liner with built in channels for coolant flow is also fabricated near net shape using the FAST process. The liner will be assembled into a test rig and hot fire tested in the MSFC test facility to determine performance. This paper describes the development of this novel high thermal conductivity NARloy-Z-D composite material, and the advanced net shape technology to fabricate the combustion chamber liner. Properties of optimized NARloy-Z-D composite material will also be presented.

Thermal Protection Supplement for Reducing Interface Thermal Mismatch

NASA Technical Reports Server (NTRS)

Stewart, David A. (Inventor); Leiser, Daniel B. (Inventor)

2017-01-01

A thermal protection system that reduces a mismatch of thermal expansion coefficients CTE between a first material layer (CTE1) and a second material layer (CTE2) at a first layer-second layer interface. A portion of aluminum borosilicate (abs) or another suitable additive (add), whose CTE value, CTE(add), satisfies (CTE(add)-CTE1)(CTE(add)-CTE2)<0, is distributed with variable additive density,.rho.(z;add), in the first material layer and/or in the second material layer, with.rho.(z;add) near the materials interface being relatively high (alternatively, relatively low) and.rho.(z;add) in a region spaced apart from the interface being relatively low (alternatively, relatively high).

TABULATED EQUIVALENT SDR FLAMELET (TESF) MODEFL

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

KUNDU, PRITHWISH; AMEEN, mUHSIN MOHAMMED; UNNIKRISHNAN, UMESH

The code consists of an implementation of a novel tabulated combustion model for non-premixed flames in CFD solvers. This novel technique/model is used to implement an unsteady flamelet tabulation without using progress variables for non-premixed flames. It also has the capability to include history effects which is unique within tabulated flamelet models. The flamelet table generation code can be run in parallel to generate tables with large chemistry mechanisms in relatively short wall clock times. The combustion model/code reads these tables. This framework can be coupled with any CFD solver with RANS as well as LES turbulence models. This frameworkmore » enables CFD solvers to run large chemistry mechanisms with large number of grids at relatively lower computational costs. Currently it has been coupled with the Converge CFD code and validated against available experimental data. This model can be used to simulate non-premixed combustion in a variety of applications like reciprocating engines, gas turbines and industrial burners operating over a wide range of fuels.« less

Inadequacy representation of flamelet-based RANS model for turbulent non-premixed flame

NASA Astrophysics Data System (ADS)

Lee, Myoungkyu; Oliver, Todd; Moser, Robert

2017-11-01

Stochastic representations for model inadequacy in RANS-based models of non-premixed jet flames are developed and explored. Flamelet-based RANS models are attractive for engineering applications relative to higher-fidelity methods because of their low computational costs. However, the various assumptions inherent in such models introduce errors that can significantly affect the accuracy of computed quantities of interest. In this work, we develop an approach to represent the model inadequacy of the flamelet-based RANS model. In particular, we pose a physics-based, stochastic PDE for the triple correlation of the mixture fraction. This additional uncertain state variable is then used to construct perturbations of the PDF for the instantaneous mixture fraction, which is used to obtain an uncertain perturbation of the flame temperature. A hydrogen-air non-premixed jet flame is used to demonstrate the representation of the inadequacy of the flamelet-based RANS model. This work was supported by DARPA-EQUiPS(Enabling Quantification of Uncertainty in Physical Systems) program.

Thiabendazole uptake in shimeji, king oyster, and oyster mushrooms and its persistence in sterile and nonsterile substrates.

PubMed

Zhang, Zhiyong; Jiang, Wayne; Jian, Qiu; Song, Wencheng; Zheng, Zuntao; Ke, Changjie; Liu, Xianjin

2014-02-12

Thiabendazole in the substrates incurred from spraying and premixing was translocated to the pileus, stipe, and volva of selected mushrooms. The spraying on the substrates resulted in higher residues of thiabendazole in all three mushrooms than the premixing treatment. For premixing, in the five substrates, half-lives of thiabendazole were found to be 13.6 days for shimeji, 10.0 days for king oyster, 13.7 days for oyster, 19.1 days for sterilized substrate, and 8.4 days for nonsterilized substrate, respectively. For spraying, the longest and shortest half-lives were found to be 19.5 and 8.1 days for the nonsterilized and sterilized substrates, respectively. The residues of thiabendazole in three edible fungi were increased with the incubation days from 3 to 5 to 7. The residues of thiabendazole in king oyster were the highest among the three fungi while those in shimeji and oyster showed similar patterns.

Flame Structure and Dynamics for an Array of Premixed Methane-Air Jets

NASA Astrophysics Data System (ADS)

Nigam, Siddharth P.; Lapointe, Caelan; Christopher, Jason D.; Wimer, Nicholas T.; Hayden, Torrey R. S.; Rieker, Gregory B.; Hamlington, Peter E.

2017-11-01

Premixed flames have been studied extensively, both experimentally and computationally, and their properties are reasonably well characterized for a range of conditions and configurations. However, the premixed combustion process is potentially much more difficult to predict when many such flames are arranged in a closely spaced array. These arrays must be better understood, in particular, for the design of industrial burners used in chemical and heat treatment processes. Here, the effects of geometric array parameters (e.g., angle and diameter of jet inlets, number of inlets and their respective orientation) and operating conditions (e.g., jet velocities, fuel-air ratio) on flame structure and dynamics are studied using large eddy simulations (LES). The simulations are performed in OpenFOAM using multi-step chemistry for a methane-air mixture, and temperature and chemical composition fields are characterized for a variety of configurations as functions of height above the array. Implications of these results for the design and operation of industrial burners are outlined.

Establishing bioequivalence of veterinary premixes (Type A medicated articles).

PubMed

Hunter, R P; Lees, P; Concordet, D; Toutain, P-L

2012-04-01

a) Key issues concerning Premix (Type A medicated articles) Bioequivalence evaluations: 1) This is a complex issue concerning both route of administration and formulation. 2) If the animal is not at the bunk/trough, the animal is not self-administering (eating medicated feed), thus there can be no drug absorption. b) Differing opinions among scientists and regulatory authorities/expert bodies regarding: 1) No harmonization on how to design, conduct, and interpret in vivo studies. 2) Applicability of biowaivers to Type A (premix) products. 3) Why are topdress and complete feed considered differently? Are they different formulations or different routes of administration? 4) Single dose vs. multi-dose studies. 5) What is the final formulation? c) What are the next steps: 1) Harmonize current bioequivalence guidelines through the VICH process. 2) Determine the applicability/non-applicability of the Biopharmaceutical Classification System (BCS). 3) Establish the Total Mixed Ration (i.e. formulation) effects. 4) Define the test subject (individual, pen, etc.). © 2012 Blackwell Publishing Ltd.

Studies in premixed combustion. [Benjamin Levich Inst. for Physico-Chemical Hydrodynamics, City College of CUNY, New York, New York

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

Sivashinsky, G.I.

1993-01-01

During the period under review, significant progress was been made in studying the intrinsic dynamics of premixed flames and the problems of flame-flow interaction. (1) A weakly nonlinear model for Bunsen burner stabilized flames was proposed and employed for the simulation of three-dimensional polyhedral flames -- one of the most graphic manifestations of thermal-diffusive instability in premixed combustion. (2) A high-precision large-scale numerical simulation of Bunsen burner tip structure was conducted. The results obtained supported the earlier conjecture that the tip opening observed in low Lewis number systems is a purely optical effect not involving either flame extinction or leakagemore » of unburned fuel. (3) A one-dimensional model describing a reaction wave moving through a unidirectional periodic flow field is proposed and studied numerically. For long-wavelength fields the system exhibits a peculiar non-uniqueness of possible propagation regimes. The transition from one regime to another occurs in a manner of hysteresis.« less

A Numerical Study of Spray Injected in a Gas Turbine Lean Pre-Mixed Pre-Vaporized Combustor

NASA Astrophysics Data System (ADS)

Amoresano, Amedeo; Cameretti, Maria Cristina; Tuccillo, Raffaele

2015-04-01

The authors have performed a numerical study to investigate the spray evolution in a modern gas turbine combustor of the Lean Pre-Mixed Pre-vaporized type. The CFD tool is able to simulate the injection conditions, by isolating and studying some specific phenomena. The calculations have been performed by using a 3-D fluid dynamic code, the FLUENT flow solver, by choosing the injection models on the basis of a comparative analysis with some experimental data, in terms of droplet diameters, obtained by PDA technique. In a first phase of the investigation, the numerical simulation refers to non-evaporating flow conditions, in order to validate the estimation of the fundamental spray parameters. Next, the calculations employ boundary conditions close to those occurring in the actual combustor operation, in order to predict the fuel vapour distribution throughout the premixing chamber. The results obtained allow the authors to perform combustion simulation in the whole domain.

DNS and modeling of the interaction between turbulent premixed flames and walls

NASA Technical Reports Server (NTRS)

Poinsot, T. J.; Haworth, D. C.

1992-01-01

The interaction between turbulent premixed flames and walls is studied using a two-dimensional full Navier-Stokes solver with simple chemistry. The effects of wall distance on the local and global flame structure are investigated. Quenching distances and maximum wall heat fluxes during quenching are computed in laminar cases and are found to be comparable to experimental and analytical results. For turbulent cases, it is shown that quenching distances and maximum heat fluxes remain of the same order as for laminar flames. Based on simulation results, a 'law-of-the-wall' model is derived to describe the interaction between a turbulent premixed flame and a wall. This model is constructed to provide reasonable behavior of flame surface density near a wall under the assumption that flame-wall interaction takes place at scales smaller than the computational mesh. It can be implemented in conjunction with any of several recent flamelet models based on a modeled surface density equation, with no additional constraints on mesh size or time step.

Facilities for microgravity combustion research

NASA Technical Reports Server (NTRS)

Sacksteder, Kurt R.

1988-01-01

Combustion science and applications have benefited in unforeseen ways from experimental research performed in the low-gravity environment. The capability to control for the first time the influence of gravitational buoyancy has provided some insight into soot formation in droplet combustion, the nature of flammability limits in premixed gases, and the relationship between normal-gravity and low-gravity material flammability that may influence how materials are best selected for routine use in habitable spacecraft. The opportunity to learn about these complex phenomena is derived from the control of the ambient body-force field and, perhaps as importantly, the simplified boundary conditions that can be established in well designed low-gravity combustion experiments. A description of the test facilities and typical experimental apparatus are provided; and conceptual plans for a Space Station Freedom capability, the Modular Combustion Facility, are described.

Development of fire shutters based on numerical optimizations

NASA Astrophysics Data System (ADS)

Novak, Ondrej; Kulhavy, Petr; Martinec, Tomas; Petru, Michal; Srb, Pavel

2018-06-01

This article deals with a prototype concept, real experiment and numerical simulation of a layered industrial fire shutter, based on some new insulating composite materials. The real fire shutter has been developed and optimized in laboratory and subsequently tested in the certified test room. A simulation of whole concept has been carried out as the non-premixed combustion process in the commercial final volume sw Pyrosim. Model of the combustion based on a stoichiometric defined mixture of gas and the tested layered samples showed good conformity with experimental results - i.e. thermal distribution inside and heat release rate that has gone through the sample.

Process for preparing high-transition-temperature superconductors in the Nb-Al-Ge system

DOEpatents

Giorgi, A.L.; Szklarz, E.G.

1973-01-30

The patent describes a process for preparing superconducting materials in the Nb-Al-Ge system having transition temperatures in excess of 19K. The process comprises premixing powdered constituents, pressing them into a plug, heating the plug to 1,450-1,800C for 30 minutes to an hour under vacuum or an inert atmosphere, and annealing at moderate temperatures for reasonably long times (approximately 50 hours). High transition-temperature superconductors, including those in the Nb3(Al,Ge) system, prepared in accordance with this process exhibit little degradation in the superconducting transition temperature on being ground to -200 mesh powder. (GRA)

Hydrodynamic and shock heating instabilities of liquid metal strippers for RIA

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

Hassanein, Ahmed

2013-05-24

Stripping of accelerated ions is a key problem for the design of RIA to obtain high efficiency. Thin liquid Lithium film flow is currently considered as stripper for RIA ion beams to obtain higher Z for following acceleration: in extreme case of Uranium from Z=29 to Z=60-70 (first stripper) and from Z=70 till full stripping Z=92 (second stripper). Ionization of ion occurs due to the interaction of the ion with electrons of target material (Lithium) with the loss of parts of the energy due to ionization, Q{sub U}, which is also accompanied with ionization energy losses, Q{sub Li} of themore » lithium. The resulting heat is so high that can be removed not by heat conduction but mainly by convection, i.e., flowing of liquid metal across beam spot area. The interaction of the beam with the liquid metal generates shock wave propagating along direction perpendicular to the beam as well as excites oscillations along beam direction. We studied the dynamics of these excited waves to determine conditions for film stability at the required velocities for heat removal. It will allow optimizing jet nozzle shapes and flow parameters to prevent film fragmentation and to ensure stable device operation.« less

Coupling between premixed flame propagation and swirl flow during boundary layer flashback

NASA Astrophysics Data System (ADS)

Ebi, Dominik; Ranjan, Rakesh; Clemens, Noel T.

2018-07-01

Flashback of premixed methane-air flames in the turbulent boundary layer of swirling flows is investigated experimentally. The premix section of the atmospheric model swirl combustor features an axial swirler with an attached center-body. Our previous work with this same configuration investigated the flame propagation during flashback using particle image velocimetry (PIV) with liquid droplets as seed particles that precluded making measurements in the burnt gases. The present study investigates the transient velocity field in the unburnt and burnt gas region by means of solid-particle seeding and high-speed stereoscopic PIV. The global axial and circumferential lab-frame flame propagation speed is obtained simultaneously based on high-speed chemiluminescence movies. By combining the PIV data with the global flame propagation speed, the quasi-instantaneous swirling motion of the velocity field is constructed on annular shells, which provides a more intuitive view on the complex three-dimensional flow-flame interaction. Previous works showed that flashback is led by flame tongues. We find that the important flow-flame interaction occurs on the far side of these flame tongues relative to the approach flow, which we henceforth refer to as the leading side. The leading side is found to propagate as a classical premixed flame front relative to the strongly modified approach flow field. The blockage imposed by flame tongues is not limited to the immediate vicinity of the flame base, but occurs along the entire leading side.

Flow field and scalar measurements in a series of turbulent partially-premixed dimethyl ether/air jet flames

DOE PAGES

Coriton, Bruno; Im, Seong -Kyun; Gamba, Mirko; ...

2017-03-12

Here, we present a series of benchmark flames consisting of six partially-premixed piloted dimethyl ether (DME)/air jet flames. These flames provide an opportunity to understand turbulence-flame interactions for oxygenated fuels and to develop predictive models for these interactions using a canonical burner geometry. The development of accurate models for DME/air flames would establish a foundation for studies of more complex oxygenated fuels. The flames are stabilized on a piloted jet burner similar to that of the partially-premixed methane/air jet flames that have been studied extensively within the context of the TNF Workshop. This series of six jet flames spans jetmore » exit Reynolds numbers, ReD, from 29,300 to 73,300 and stoichiometric mixture fractions, ξ st, from 0.35 to 0.60. Flame conditions range from very low probability of localized extinction to a high probability of localized extinction and subsequent re-ignition. Measurements in the flames are compared at downstream locations from 5 to 25 diameters above the nozzle exit. Mean and fluctuating velocity components are measured using stereo particle image velocimetry (SPIV). Simultaneous laser-induced fluorescence (LIF) imaging of OH and CH 2O provides insights into the distribution of these intermediate species in partially-premixed DME/air flames. OH LIF imaging is also combined with SPIV to investigate the strain rate field across the reaction zone.« less

Laser-based investigations in gas turbine model combustors

NASA Astrophysics Data System (ADS)

Meier, W.; Boxx, I.; Stöhr, M.; Carter, C. D.

2010-10-01

Dynamic processes in gas turbine (GT) combustors play a key role in flame stabilization and extinction, combustion instabilities and pollutant formation, and present a challenge for experimental as well as numerical investigations. These phenomena were investigated in two gas turbine model combustors for premixed and partially premixed CH4/air swirl flames at atmospheric pressure. Optical access through large quartz windows enabled the application of laser Raman scattering, planar laser-induced fluorescence (PLIF) of OH, particle image velocimetry (PIV) at repetition rates up to 10 kHz and the simultaneous application of OH PLIF and PIV at a repetition rate of 5 kHz. Effects of unmixedness and reaction progress in lean premixed GT flames were revealed and quantified by Raman scattering. In a thermo-acoustically unstable flame, the cyclic variation in mixture fraction and its role for the feedback mechanism of the instability are addressed. In a partially premixed oscillating swirl flame, the cyclic variations of the heat release and the flow field were characterized by chemiluminescence imaging and PIV, respectively. Using phase-correlated Raman scattering measurements, significant phase-dependent variations of the mixture fraction and fuel distributions were revealed. The flame structures and the shape of the reaction zones were visualized by planar imaging of OH distribution. The simultaneous OH PLIF/PIV high-speed measurements revealed the time history of the flow field-flame interaction and demonstrated the development of a local flame extinction event. Further, the influence of a precessing vortex core on the flame topology and its dynamics is discussed.

Flow field and scalar measurements in a series of turbulent partially-premixed dimethyl ether/air jet flames

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

Coriton, Bruno; Im, Seong -Kyun; Gamba, Mirko

Here, we present a series of benchmark flames consisting of six partially-premixed piloted dimethyl ether (DME)/air jet flames. These flames provide an opportunity to understand turbulence-flame interactions for oxygenated fuels and to develop predictive models for these interactions using a canonical burner geometry. The development of accurate models for DME/air flames would establish a foundation for studies of more complex oxygenated fuels. The flames are stabilized on a piloted jet burner similar to that of the partially-premixed methane/air jet flames that have been studied extensively within the context of the TNF Workshop. This series of six jet flames spans jetmore » exit Reynolds numbers, ReD, from 29,300 to 73,300 and stoichiometric mixture fractions, ξ st, from 0.35 to 0.60. Flame conditions range from very low probability of localized extinction to a high probability of localized extinction and subsequent re-ignition. Measurements in the flames are compared at downstream locations from 5 to 25 diameters above the nozzle exit. Mean and fluctuating velocity components are measured using stereo particle image velocimetry (SPIV). Simultaneous laser-induced fluorescence (LIF) imaging of OH and CH 2O provides insights into the distribution of these intermediate species in partially-premixed DME/air flames. OH LIF imaging is also combined with SPIV to investigate the strain rate field across the reaction zone.« less

Numerical study of transient evolution of lifted jet flames: partially premixed flame propagation and influence of physical dimensions

NASA Astrophysics Data System (ADS)

Chen, Zhi; Ruan, Shaohong; Swaminathan, Nedunchezhian

2016-07-01

Three-dimensional (3D) unsteady Reynolds-averaged Navier-Stokes simulations of a spark-ignited turbulent methane/air jet flame evolving from ignition to stabilisation are conducted for different jet velocities. A partially premixed combustion model is used involving a correlated joint probability density function and both premixed and non-premixed combustion mode contributions. The 3D simulation results for the temporal evolution of the flame's leading edge are compared with previous two-dimensional (2D) results and experimental data. The comparison shows that the final stabilised flame lift-off height is well predicted by both 2D and 3D computations. However, the transient evolution of the flame's leading edge computed from 3D simulation agrees reasonably well with experiment, whereas evident discrepancies were found in the previous 2D study. This difference suggests that the third physical dimension plays an important role during the flame transient evolution process. The flame brush's leading edge displacement speed resulting from reaction, normal and tangential diffusion processes are studied at different typical stages after ignition in order to understand the effect of the third physical dimension further. Substantial differences are found for the reaction and normal diffusion components between 2D and 3D simulations especially in the initial propagation stage. The evolution of reaction progress variable scalar gradients and its interaction with the flow and mixing field in the 3D physical space have an important effect on the flame's leading edge propagation.

A binned clustering algorithm to detect high-Z material using cosmic muons

NASA Astrophysics Data System (ADS)

Thomay, C.; Velthuis, J. J.; Baesso, P.; Cussans, D.; Morris, P. A. W.; Steer, C.; Burns, J.; Quillin, S.; Stapleton, M.

2013-10-01

We present a novel approach to the detection of special nuclear material using cosmic rays. Muon Scattering Tomography (MST) is a method for using cosmic muons to scan cargo containers and vehicles for special nuclear material. Cosmic muons are abundant, highly penetrating, not harmful for organic tissue, cannot be screened against, and can easily be detected, which makes them highly suited to the use of cargo scanning. Muons undergo multiple Coulomb scattering when passing through material, and the amount of scattering is roughly proportional to the square of the atomic number Z of the material. By reconstructing incoming and outgoing tracks, we can obtain variables to identify high-Z material. In a real life application, this has to happen on a timescale of 1 min and thus with small numbers of muons. We have built a detector system using resistive plate chambers (RPCs): 12 layers of RPCs allow for the readout of 6 x and 6 y positions, by which we can reconstruct incoming and outgoing tracks. In this work we detail the performance of an algorithm by which we separate high-Z targets from low-Z background, both for real data from our prototype setup and for MC simulation of a cargo container-sized setup. (c) British Crown Owned Copyright 2013/AWE

Using real-time electron microscopy to explore the effects of transition-metal composition on the local thermal stability in charged Li xNi yMn zCo 1-y-zO 2 cathode materials

DOE PAGES

Hwang, Sooyeon; Kim, Seung Min; Bak, Seong -Min; ...

2015-05-08

In this study, we use in-situ transmission electron microcopy (TEM) to investigate the thermal decomposition that occurs at the surface of charged Li xNi yMn zCo 1-y-zO 2 (NMC) cathode materials of different composition (with y, z=0.8, 0.1 and 0.6, 0.2 and 0.4, 0.3), after they have been charged to their practical upper limit voltage (4.3V). By heating these materials inside the TEM, we are able to directly characterize near surface changes in both their electronic structure (using electron energy loss spectroscopy) and crystal structure and morphology (using electron diffraction and bright-field imaging). The most Ni-rich material (y, z =more » 0.8, 0.1) is found to be thermally unstable at significantly lower temperatures than the other compositions – this is manifested by changes in both the electronic structure and the onset of phase transitions at temperatures as low as 100°C. Electron energy loss spectroscopy indicates that the thermally induced reduction of Ni ions drives these changes, and that this is exacerbated by the presence of an additional redox reaction that occurs at 4.2V in the y, z = 0.8, 0.1 material. Exploration of individual particles shows that there are substantial variations in the onset temperatures and overall extent of these changes. Of the compositions studied, the composition of y, z = 0.6, 0.2 has the optimal combination of high energy density and reasonable thermal stability. The observations herein demonstrate that real time electron microscopy provide direct insight into the changes that occur in cathode materials with temperature, allowing optimization of different alloy concentrations to maximize overall performance.« less

Modeling and simulation of combustion dynamics in lean-premixed swirl-stabilized gas-turbine engines

NASA Astrophysics Data System (ADS)

Huang, Ying

This research focuses on the modeling and simulation of combustion dynamics in lean-premixed gas-turbines engines. The primary objectives are: (1) to establish an efficient and accurate numerical framework for the treatment of unsteady flame dynamics; and (2) to investigate the parameters and mechanisms responsible for driving flow oscillations in a lean-premixed gas-turbine combustor. The energy transfer mechanisms among mean flow motions, periodic motions and background turbulent motions in turbulent reacting flow are first explored using a triple decomposition technique. Then a comprehensive numerical study of the combustion dynamics in a lean-premixed swirl-stabilized combustor is performed. The analysis treats the conservation equations in three dimensions and takes into account finite-rate chemical reactions and variable thermophysical properties. Turbulence closure is achieved using a large-eddy-simulation (LES) technique. The compressible-flow version of the Smagorinsky model is employed to describe subgrid-scale turbulent motions and their effect on large-scale structures. A level-set flamelet library approach is used to simulate premixed turbulent combustion. In this approach, the mean flame location is modeled using a level-set G-equation, where G is defined as a distance function. Thermophysical properties are obtained using a presumed probability density function (PDF) along with a laminar flamelet library. The governing equations and the associated boundary conditions are solved by means of a four-step Runge-Kutta scheme along with the implementation of the message passing interface (MPI) parallel computing architecture. The analysis allows for a detailed investigation into the interaction between turbulent flow motions and oscillatory combustion of a swirl-stabilized injector. Results show good agreement with an analytical solution and experimental data in terms of acoustic properties and flame evolution. A study of flame bifurcation from a stable state to an unstable state indicates that the inlet flow temperature and equivalence ratio are the two most important variables determining the stability characteristics of the combustor. Under unstable operating conditions, several physical processes responsible for driving combustion instabilities in the chamber have been identified and quantified. These processes include vortex shedding and acoustic interaction, coupling between the flame evolution and local flow oscillations, vortex and flame interaction and coupling between heat release and acoustic motions. The effects of inlet swirl number on the flow development and flame dynamics in the chamber are also carefully studied. In the last part of this thesis, an analytical model is developed using triple decomposition techniques to model the combustion response of turbulent premixed flames to acoustic oscillations.

Chord-length and free-path distribution functions for many-body systems

NASA Astrophysics Data System (ADS)

Lu, Binglin; Torquato, S.

1993-04-01

We study fundamental morphological descriptors of disordered media (e.g., heterogeneous materials, liquids, and amorphous solids): the chord-length distribution function p(z) and the free-path distribution function p(z,a). For concreteness, we will speak in the language of heterogeneous materials composed of two different materials or ``phases.'' The probability density function p(z) describes the distribution of chord lengths in the sample and is of great interest in stereology. For example, the first moment of p(z) is the ``mean intercept length'' or ``mean chord length.'' The chord-length distribution function is of importance in transport phenomena and problems involving ``discrete free paths'' of point particles (e.g., Knudsen diffusion and radiative transport). The free-path distribution function p(z,a) takes into account the finite size of a simple particle of radius a undergoing discrete free-path motion in the heterogeneous material and we show that it is actually the chord-length distribution function for the system in which the ``pore space'' is the space available to a finite-sized particle of radius a. Thus it is shown that p(z)=p(z,0). We demonstrate that the functions p(z) and p(z,a) are related to another fundamentally important morphological descriptor of disordered media, namely, the so-called lineal-path function L(z) studied by us in previous work [Phys. Rev. A 45, 922 (1992)]. The lineal path function gives the probability of finding a line segment of length z wholly in one of the ``phases'' when randomly thrown into the sample. We derive exact series representations of the chord-length and free-path distribution functions for systems of spheres with a polydispersivity in size in arbitrary dimension D. For the special case of spatially uncorrelated spheres (i.e., fully penetrable spheres) we evaluate exactly the aforementioned functions, the mean chord length, and the mean free path. We also obtain corresponding analytical formulas for the case of mutually impenetrable (i.e., spatially correlated) polydispersed spheres.

Tibia and radius bone geometry and volumetric density in obese compared to non-obese adolescents.

PubMed

Leonard, Mary B; Zemel, Babette S; Wrotniak, Brian H; Klieger, Sarah B; Shults, Justine; Stallings, Virginia A; Stettler, Nicolas

2015-04-01

Childhood obesity is associated with biologic and behavioral characteristics that may impact bone mineral density (BMD) and structure. The objective was to determine the association between obesity and bone outcomes, independent of sexual and skeletal maturity, muscle area and strength, physical activity, calcium intake, biomarkers of inflammation, and vitamin D status. Tibia and radius peripheral quantitative CT scans were obtained in 91 obese (BMI>97th percentile) and 51 non-obese adolescents (BMI>5th and <85th percentiles). Results were converted to sex- and race-specific Z-scores relative to age. Cortical structure, muscle area and muscle strength (by dynamometry) Z-scores were further adjusted for bone length. Obese participants had greater height Z-scores (p<0.001), and advanced skeletal maturity (p<0.0001), compared with non-obese participants. Tibia cortical section modulus and calf muscle area Z-scores were greater in obese participants (1.07 and 1.63, respectively, both p<0.0001). Tibia and radius trabecular and cortical volumetric BMD did not differ significantly between groups. Calf muscle area and strength Z-scores, advanced skeletal maturity, and physical activity (by accelerometry) were positively associated with tibia cortical section modulus Z-scores (all p<0.01). Adjustment for muscle area Z-score attenuated differences in tibia section modulus Z-scores between obese and non-obese participants from 1.07 to 0.28. After multivariate adjustment for greater calf muscle area and strength Z-scores, advanced maturity, and less moderate to vigorous physical activity, tibia section modulus Z-scores were 0.32 (95% CI -0.18, 0.43, p=0.06) greater in obese, vs. non-obese participants. Radius cortical section modulus Z-scores were 0.45 greater (p=0.08) in obese vs. non-obese participants; this difference was attenuated to 0.14 with adjustment for advanced maturity. These findings suggest that greater tibia cortical section modulus in obese adolescents is attributable to advanced skeletal maturation and greater muscle area and strength, while less moderate to vigorous physical activities offset the positive effects of these covariates. The impact of obesity on cortical structure was greater at weight bearing sites. Copyright © 2014 Elsevier Inc. All rights reserved.

Flame holding tolerant fuel and air premixer for a gas turbine combustor

DOEpatents

York, William David; Johnson, Thomas Edward; Ziminsky, Willy Steve

2012-11-20

A fuel nozzle with active cooling is provided. It includes an outer peripheral wall, a nozzle center body concentrically disposed within the outer wall in a fuel and air pre-mixture. The fuel and air pre-mixture includes an air inlet, a fuel inlet and a premixing passage defined between the outer wall in the center body. A gas fuel flow passage is provided. A first cooling passage is included within the center body in a second cooling passage is defined between the center body and the outer wall.

Characterization of complexities in combustion instability in a lean premixed gas-turbine model combustor.

PubMed

Gotoda, Hiroshi; Amano, Masahito; Miyano, Takaya; Ikawa, Takuya; Maki, Koshiro; Tachibana, Shigeru

2012-12-01

We characterize complexities in combustion instability in a lean premixed gas-turbine model combustor by nonlinear time series analysis to evaluate permutation entropy, fractal dimensions, and short-term predictability. The dynamic behavior in combustion instability near lean blowout exhibits a self-affine structure and is ascribed to fractional Brownian motion. It undergoes chaos by the onset of combustion oscillations with slow amplitude modulation. Our results indicate that nonlinear time series analysis is capable of characterizing complexities in combustion instability close to lean blowout.

Experimental study of the operating characteristics of premixing-prevaporizing fuel/air mixing passages

NASA Technical Reports Server (NTRS)

Rohy, D. A.; Meier, J. G.

1983-01-01

Fuel spray and air flow characteristics were determined using nonintrusive (optical) measurement techniques in a fuel preparation duct. A very detailed data set was obtained at high pressures (to 10 atm) and temperatures (to 750 K). The data will be used to calibrate an analytical model which will facilitate the design of a lean premixed prevaporized combustor. This combustor has potential for achieving low pollutant emissions and low levels of flame radiation and pattern factors conductive to improved durability and performance for a variety of fuels.

Errors induced by catalytic effects in premixed flame temperature measurements

NASA Astrophysics Data System (ADS)

Pita, G. P. A.; Nina, M. N. R.

The evaluation of instantaneous temperature in a premixed flame using fine-wire Pt/Pt-(13 pct)Rh thermocouples was found to be subject to significant errors due to catalytic effects. An experimental study was undertaken to assess the influence of local fuel/air ratio, thermocouple wire diameter, and gas velocity on the thermocouple reading errors induced by the catalytic surface reactions. Measurements made with both coated and uncoated thermocouples showed that the catalytic effect imposes severe limitations on the accuracy of mean and fluctuating gas temperature in the radical-rich flame zone.

Frontiers in Fluid Mechanics: A Collection of Research Papers Written in Commemoration of the 65th Birthday of Stanley Corrsin.

DTIC Science & Technology

1985-04-30

analogous fashion. If the flow variable lFtis taken at x and F 6(xi,t) > d , - 1, . n, n > 1 is required, various subsets of the flow domain atare obtained...discussed: non-premixed and premixed combustion. The chemistry of combustion in the gas phase involves complex systems of reaction steps with numerous...components. In order to keep the problem tractable, only a greatly simplified and global description of chemistry will be employed. In both cases V

Analysis of effect of flameholder characteristics on lean, premixed, partially vaporized fuel-air mixtures quality and nitrogen oxides emissions

NASA Technical Reports Server (NTRS)

Cooper, L. P.

1981-01-01

An analysis was conducted of the effect of flameholding devices on the precombustion fuel-air characteristics and on oxides of nitrogen (NOx) emissions for combustion of premixed partially vaporized mixtures. The analysis includes the interrelationships of flameholder droplet collection efficiency, reatomization efficiency and blockage, and the initial droplet size distribution and accounts for the contribution of droplet combustion in partially vaporized mixtures to NOx emissions. Application of the analytical procedures is illustrated and parametric predictions of NOx emissions are presented.

Origami interleaved tube cellular materials

NASA Astrophysics Data System (ADS)

Cheung, Kenneth C.; Tachi, Tomohiro; Calisch, Sam; Miura, Koryo

2014-09-01

A novel origami cellular material based on a deployable cellular origami structure is described. The structure is bi-directionally flat-foldable in two orthogonal (x and y) directions and is relatively stiff in the third orthogonal (z) direction. While such mechanical orthotropicity is well known in cellular materials with extruded two dimensional geometry, the interleaved tube geometry presented here consists of two orthogonal axes of interleaved tubes with high interfacial surface area and relative volume that changes with fold-state. In addition, the foldability still allows for fabrication by a flat lamination process, similar to methods used for conventional expanded two dimensional cellular materials. This article presents the geometric characteristics of the structure together with corresponding kinematic and mechanical modeling, explaining the orthotropic elastic behavior of the structure with classical dimensional scaling analysis.

Multiple imaging mode X-ray computed tomography for distinguishing active and inactive phases in lithium-ion battery cathodes

NASA Astrophysics Data System (ADS)

Komini Babu, Siddharth; Mohamed, Alexander I.; Whitacre, Jay F.; Litster, Shawn

2015-06-01

This paper presents the use of nanometer scale resolution X-ray computed tomography (nano-CT) in the three-dimensional (3D) imaging of a Li-ion battery cathode, including the separate volumes of active material, binder plus conductive additive, and pore. The different high and low atomic number (Z) materials are distinguished by sequentially imaging the lithium cobalt oxide electrode in absorption and then Zernike phase contrast modes. Morphological parameters of the active material and the additives are extracted from the 3D reconstructions, including the distribution of contact areas between the additives and the active material. This method could provide a better understanding of the electric current distribution and structural integrity of battery electrodes, as well as provide detailed geometries for computational models.

Fluid Phase Separation (FPS) experiment for flight on a space shuttle Get Away Special (GAS) canister

NASA Technical Reports Server (NTRS)

Peters, Bruce; Wingo, Dennis; Bower, Mark; Amborski, Robert; Blount, Laura; Daniel, Alan; Hagood, Bob; Handley, James; Hediger, Donald; Jimmerson, Lisa

1990-01-01

The separation of fluid phases in microgravity environments is of importance to environmental control and life support systems (ECLSS) and materials processing in space. A successful fluid phase separation experiment will demonstrate a proof of concept for the separation technique and add to the knowledge base of material behavior. The phase separation experiment will contain a premixed fluid which will be exposed to a microgravity environment. After the phase separation of the compound has occurred, small samples of each of the species will be taken for analysis on the Earth. By correlating the time of separation and the temperature history of the fluid, it will be possible to characterize the process. The experiment has been integrated into space available on a manifested Get Away Special (GAS) experiment, CONCAP 2, part of the Consortium for Materials Complex Autonomous Payload (CAP) Program, scheduled for STS-42. The design and the production of a fluid phase separation experiment for rapid implementation at low cost is presented.

Materials, devices, techniques, and applications for Z-plane focal plane array technology II; Proceedings of the Meeting, San Diego, CA, July 12, 13, 1990

NASA Astrophysics Data System (ADS)

Carson, John C.

1990-11-01

Various papers on materials, devices, techniques, and applications for X-plane focal plane array technology are presented. Individual topics addressed include: application of Z-plane technology to the remote sensing of the earth from GEO, applications of smart neuromorphic focal planes, image-processing of Z-plane technology, neural network Z-plane implementation with very high interconnection rates, using a small IR surveillance satellite for tactical applications, establishing requirements for homing applications, Z-plane technology. Also discussed are: on-array spike suppression signal processing, algorithms for on-focal-plane gamma circumvention and time-delay integration, current HYMOSS Z-technology, packaging of electrons for on- and off-FPA signal processing, space/performance qualification of tape automated bonded devices, automation in tape automated bonding, high-speed/high-volume radiometric testing of Z-technology focal planes, 128-layer HYMOSS-module fabrication issues, automation of IRFPA production processes.

Insight into synergistically enhanced adsorption and visible light photocatalytic performance of Z-scheme heterojunction of SrTiO3(La,Cr)-decorated WO3 nanosheets

NASA Astrophysics Data System (ADS)

Liu, Xin; Jiang, Junzhe; Jia, Yushuai; Qiu, Jinmin; Xia, Tonglin; Zhang, Yuhong; Li, Yuqin; Chen, Xiangshu

2017-08-01

The efficient treatment of dye wastewater has been a hot topic of environment field. The integration of adsorption and photocatalytic degradation via fabrication of bi-component heterojunction photocatalyst is considered as a facile and effective strategy to enhance the dye elimination efficiency. In this report, a Z-scheme heterojunction material, SrTiO3(La,Cr)/WO3 with bifunction of adsorption and photocatalysis was successfully synthesized for efficient removal of methylene blue (MB) under visible light irradiation. The morphology and microstructure characterization demonstrates that the SrTiO3(La,Cr) nanoparticles are uniformly decorated on the WO3 nanosheets, forming an intimate heterojunction interface. MB degradation results indicate that the removal efficiency by the synergistic adsorption-photocatalysis process is greatly improved compared to pure WO3 and SrTiO3(La,Cr) with the adsorption and photocatalytic activity closely related to the composition of the material. The possible mechanism for the enhanced photocatalytic activity could be ascribed to the formation of a Z-scheme heterojunction system based on active species trapping experiments. Furthermore, the investigations of adsorption kinetics and isotherm show that the adsorption process follows pseudo-second-order kinetic model and Langmuir isotherm, respectively. Due to the synergistic advantages of negative zeta potential, large surface area and accelerated separation of photogenerated carriers driven by Z-scheme heterojunction, SrTiO3(La,Cr)/WO3 exhibits excellent adsorption-photocatalytic performance and stability on MB removal, which could be potentially used for practical wastewater treatment.

Femtosecond Z-scan measurements of the nonlinear refractive index of fused silica

NASA Astrophysics Data System (ADS)

Zhang, Lin; Shi, Zhendong; Ma, Hua; Ren, Huan; Yuan, Quan; Ma, Yurong; Feng, Xiaoxuan; Chen, Bo; Yang, Yi

2018-01-01

Z-scan technology is a popular experimental technique for determining the nonlinear refractive index of the material. However, it encounters a great difficulty in measuring the weak nonlinear material like fused silica which is about two orders of magnitude below the nonlinear refractive index of most of the materials studied with the nanosecond and picosecond Z-scan methods. In this case, the change of refractive index introduced by accumulation of thermal effects cannot be neglected. In order to have a reliable measurement of the nonlinear refractive index, a metrology bench based on the femtosecond Z-scan technology is developed. The intensity modulation component and the differential measurement system are applied to guarantee the accuracy of the measuring system. Based on the femtosecond Z-scan theory, the femtosecond laser Z-scan technique is performed on fused silica, and the nonlinear refractive index of Fused silica is determined to be 9.2039×10-14esu for 800nm, 37fs pulse duration at I0=50GW/cm2 with a good repeatability of 6.7%.

Impact of computerized order entry and pre-mixed dialysis solutions for continuous veno-venous hemodiafiltration on selection of therapy for acute renal failure.

PubMed

Saadulla, Lawand; Reeves, W Brian; Irey, Brittany; Ghahramani, Nasrollah

2012-02-01

To investigate the impacts of availability of pre-mixed solutions and computerized order entry on nephrologists' choice of the initial mode of renal replacement therapy in acute renal failure. We studied 898 patients with acute renal failure in 3 consecutive eras: era 1 (custom-mixed solution; n = 309), era 2 (pre-mixed commercial solution; n = 324), and era 3 (post-computerized order entry; n = 265). The proportion of patients treated with renal replacement therapy and the time from consult to initiation of continuous renal replacement therapy was similar in the 3 eras. Following introduction of the pre-mixed solution, the proportion of patients treated with continuous renal replacement therapy increased (20% vs. 33%; p < 0.05), it was initiated at a lower serum creatinine (353 ± 123 μmol/L vs. 300 ± 80 μmol/L; p < 0.05) and in older patients (53 ± 12 vs. 61 ± 14 years; p < 0.05). There was a progressive increase in the use of continuous veno-venous hemodialysis (18% vs. 79% vs. 100%; p < 0.05) and in the total prescribed flow rate (1,382 ± 546 vs. 2,324 ± 737 vs. 2,900 ± 305 mL/hr 3; p < 0.05). There was no significant impact on mortality. The availability of a pre-mixed solution increases the likelihood of initiating continuous renal replacement therapy in acute renal failure, initiating it at a lower creatinine and for older patients, use of continuous veno-venous hemodialysis and higher prescribed continuous renal replacement therapy dose. Computerized order entry implementation is associated with an additional increase in the use of continuous veno-venous hemodialysis, higher total prescribed dialysis dose, and use of CRRT among an increasing number of patients not on mechanical ventilation. The effect of these changes on patient survival is not significant.

Understanding and predicting soot generation in turbulent non-premixed jet flames.

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

Wang, Hai; Kook, Sanghoon; Doom, Jeffrey

2010-10-01

This report documents the results of a project funded by DoD's Strategic Environmental Research and Development Program (SERDP) on the science behind development of predictive models for soot emission from gas turbine engines. Measurements of soot formation were performed in laminar flat premixed flames and turbulent non-premixed jet flames at 1 atm pressure and in turbulent liquid spray flames under representative conditions for takeoff in a gas turbine engine. The laminar flames and open jet flames used both ethylene and a prevaporized JP-8 surrogate fuel composed of n-dodecane and m-xylene. The pressurized turbulent jet flame measurements used the JP-8 surrogatemore » fuel and compared its combustion and sooting characteristics to a world-average JP-8 fuel sample. The pressurized jet flame measurements demonstrated that the surrogate was representative of JP-8, with a somewhat higher tendency to soot formation. The premixed flame measurements revealed that flame temperature has a strong impact on the rate of soot nucleation and particle coagulation, but little sensitivity in the overall trends was found with different fuels. An extensive array of non-intrusive optical and laser-based measurements was performed in turbulent non-premixed jet flames established on specially designed piloted burners. Soot concentration data was collected throughout the flames, together with instantaneous images showing the relationship between soot and the OH radical and soot and PAH. A detailed chemical kinetic mechanism for ethylene combustion, including fuel-rich chemistry and benzene formation steps, was compiled, validated, and reduced. The reduced ethylene mechanism was incorporated into a high-fidelity LES code, together with a moment-based soot model and models for thermal radiation, to evaluate the ability of the chemistry and soot models to predict soot formation in the jet diffusion flame. The LES results highlight the importance of including an optically-thick radiation model to accurately predict gas temperatures and thus soot formation rates. When including such a radiation model, the LES model predicts mean soot concentrations within 30% in the ethylene jet flame.« less

Interaction of turbulent premixed flames with combustion products: Role of stoichiometry

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

Coriton, Bruno Rene Leon; Frank, Jonathan H.; Gomez, Alessandro

Stabilization methods of turbulent flames often involve mixing of reactants with hot products of combustion. The stabilizing effect of combustion product enthalpy has been long recognized, but the role played by the chemical composition of the product gases is typically overlooked. We employ a counterflow system to pinpoint the effects of the combustion product stoichiometry on the structure of turbulent premixed flames under conditions of both stable burning and local extinction. To that end, a turbulent jet of lean-to-rich, CH 4/O 2/N 2-premixed reactants at a turbulent Reynolds number of 1050 was opposed to a stream of hot products ofmore » combustion that were generated in a preburner. While the combustion product stream temperature was kept constant, its stoichiometry was varied independently from that of the reactant stream, leading to reactant-to-product stratification of relevance to practical combustion systems. The detailed structure of the turbulent flame front was analyzed in two series of experiments using laser-induced fluorescence (LIF): joint CH 2O LIF and OH LIF measurements and joint CO LIF and OH LIF measurements. Results revealed that a decrease in local CH 2O+OH and CO+OH reaction rates coincide with the depletion of OH radicals in the vicinity of the combustion product stream. These critical combustion reaction rates were more readily quenched in the presence of products of combustion from a stoichiometric flame, whereas they were favored by lean combustion products. As a result, stoichiometric combustion products contributed to a greater occurrence of local extinction. Furthermore, they limited the capacity of premixed reactants to ignite and of the turbulent premixed flames to stabilize. In contrast, lean and rich combustion products facilitated flame ignition and stability and reduced the rate of local extinction. The influence of the combustion product stream on the turbulent flame front was limited to a zone of approximately two millimeters from the gas mixing layer interface (GMLI) of the product stream. As a result, flame fronts that were separated from the GMLI by larger distances were unaffected by the product stream stoichiometry.« less

Structure of the Soot Growth Region of Laminar Premixer Methane/Oxygen Flames

NASA Technical Reports Server (NTRS)

Xu, F.; Faeth, G. M.

1999-01-01

Soot is a dominant feature of hydrocarbon/air flames, affecting their reaction mechanisms and structure. As a result, soot processes affect capabilities for computational combustion as well as predictions of flame radiation and pollution emissions. Motivated by these observations, the present investigation extended past work on soot growth in laminar premixed flames, seeking to evaluate model predictions of flame structure. Xu et al. report direct measurements of soot residence times, soot concentrations, soot structure, gas temperatures and gas compositions for premixed flames similar to those studied by Harris and Weiner and Ramer et al. respectively. It was found that predictions of major stable gas species concentrations based on mechanisms of Leung and Lindstedt and Frenklach and coworkers, were in good agreement with the measurements. The results were also used to evaluate the hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms of Frenklach and coworkers and Colket and Hall. It was found that these mechanisms were effective using quite reasonable correlations for the steric factors appearing in the theories. The successful evaluation of the HACA mechanism of soot growth in Refs. 1 and 2 is encouraging but one aspect of this evaluation is a concern. In particular, H-atom concentrations play a crucial role in the HACA mechanism and it was necessary to estimate these concentrations because they were not measured directly. These estimates were made assuming local thermodynamic equilibrium between H, and H based on measured temperatures and H2 concentrations and the equilibrium constant data of Kee et al.. This approach was justified by the flame structure predictions; nevertheless, direct evaluation of equilibrium estimates of H-atom concentrations in the soot growth regions of laminar premixed flames is needed to provide more convincing proof of this behavior. Thus, the objective of the present investigation was to complete new measurements of the structure of the soot growth region of laminar premixed flames and to use these results to evaluate whether H and H2 are in thermodynamic equilibrium and to extend the earlier evaluation of predictions of concentrations of major gas species.

Flame stabilization and mixing characteristics in a Stagnation Point Reverse Flow combustor

NASA Astrophysics Data System (ADS)

Bobba, Mohan K.

A novel combustor design, referred to as the Stagnation Point Reverse-Flow (SPRF) combustor, was recently developed that is able to operate stably at very lean fuel-air mixtures and with low NOx emissions even when the fuel and air are not premixed before entering the combustor. The primary objective of this work is to elucidate the underlying physics behind the excellent stability and emissions performance of the SPRF combustor. The approach is to experimentally characterize velocities, species mixing, heat release and flame structure in an atmospheric pressure SPRF combustor with the help of various optical diagnostic techniques: OH PLIF, chemiluminescence imaging, PIV and Spontaneous Raman Scattering. Results indicate that the combustor is primarily stabilized in a region downstream of the injector that is characterized by low average velocities and high turbulence levels; this is also the region where most of the heat release occurs. High turbulence levels in the shear layer lead to increased product entrainment levels, elevating the reaction rates and thereby enhancing the combustor stability. The effect of product entrainment on chemical timescales and the flame structure is illustrated with simple reactor models. Although reactants are found to burn in a highly preheated (1300 K) and turbulent environment due to mixing with hot product gases, the residence times are sufficiently long compared to the ignition timescales such that the reactants do not autoignite. Turbulent flame structure analysis indicates that the flame is primarily in the thin reaction zones regime throughout the combustor, and it tends to become more flamelet like with increasing distance from the injector. Fuel-air mixing measurements in case of non-premixed operation indicate that the fuel is shielded from hot products until it is fully mixed with air, providing nearly premixed performance without the safety issues associated with premixing. The reduction in NOx emissions in the SPRF combustor are primarily due to its ability to stably operate under ultra lean (and nearly premixed) condition within the combustor. Further, to extend the usefulness of this combustor configuration to various applications, combustor geometry scaling rules were developed with the help of simplified coaxial and opposed jet models.

Interaction of turbulent premixed flames with combustion products: Role of stoichiometry

DOE PAGES

Coriton, Bruno Rene Leon; Frank, Jonathan H.; Gomez, Alessandro

2016-05-30

Stabilization methods of turbulent flames often involve mixing of reactants with hot products of combustion. The stabilizing effect of combustion product enthalpy has been long recognized, but the role played by the chemical composition of the product gases is typically overlooked. We employ a counterflow system to pinpoint the effects of the combustion product stoichiometry on the structure of turbulent premixed flames under conditions of both stable burning and local extinction. To that end, a turbulent jet of lean-to-rich, CH 4/O 2/N 2-premixed reactants at a turbulent Reynolds number of 1050 was opposed to a stream of hot products ofmore » combustion that were generated in a preburner. While the combustion product stream temperature was kept constant, its stoichiometry was varied independently from that of the reactant stream, leading to reactant-to-product stratification of relevance to practical combustion systems. The detailed structure of the turbulent flame front was analyzed in two series of experiments using laser-induced fluorescence (LIF): joint CH 2O LIF and OH LIF measurements and joint CO LIF and OH LIF measurements. Results revealed that a decrease in local CH 2O+OH and CO+OH reaction rates coincide with the depletion of OH radicals in the vicinity of the combustion product stream. These critical combustion reaction rates were more readily quenched in the presence of products of combustion from a stoichiometric flame, whereas they were favored by lean combustion products. As a result, stoichiometric combustion products contributed to a greater occurrence of local extinction. Furthermore, they limited the capacity of premixed reactants to ignite and of the turbulent premixed flames to stabilize. In contrast, lean and rich combustion products facilitated flame ignition and stability and reduced the rate of local extinction. The influence of the combustion product stream on the turbulent flame front was limited to a zone of approximately two millimeters from the gas mixing layer interface (GMLI) of the product stream. As a result, flame fronts that were separated from the GMLI by larger distances were unaffected by the product stream stoichiometry.« less

A dynamic subgrid-scale model for LES of the G-equation

NASA Technical Reports Server (NTRS)

Bourlioux, A.; Im, H. G.; Ferziger, J. H.

1996-01-01

Turbulent combustion is a difficult subject as it must deal with all of the issues found in both turbulence and combustion. (We consider only premixed flames in this paper, but some of the ideas can be applied to the non-premixed case.) As in many other fields, there are two limiting cases that are easier to deal with than the general case. These are the situations in which the chemical time scale is either much shorter or much longer than the time scale associated with the turbulence. We deal with the former case. In this limit, the flame is thin compared to the turbulence length scales and can be idealized as an infinitely thin sheet. This is commonly called the flamelet regime; it has been the subject of many papers and the basis for many models (see, e.g., Linan & Williams 1993). In the flamelet model, the local flame structure is assumed to be identical to the laminar flame structure; thus the flame propagates normal to itself at the laminar flame speed, S(sub L). This allows the use of simple approximations. For example, one expects the rate of consumption of fuel to be proportional to the area of the flame surface. This idea allowed Damkohler (1940) to propose that the wrinkled flame could be replaced by a smooth one which travels at the turbulent flame speed, S(sub T), defined by S(sub T)/S(sub L) = A(sub L) /A(sub P) where A(sub L) is the total flame surface area and AP is the area projected onto the mean direction of propagation. This relation can be expected to be valid when the flame structure is modified only slightly by the turbulence. More recent approaches have attempted to relate the turbulent flame speed to turbulence intensity, u(sub '), which presumably, characterizes the wrinkling of the flame.

Advances in understanding of high- Z material erosion and re-deposition in low- Z wall environment in DIII-D

DOE PAGES

Ding, R.; Rudakov, D. L.; Stangeby, P. C.; ...

2017-03-24

Dedicated DIII-D experiments coupled with modeling reveal that the net erosion rate of high-Z materials, i.e. Mo and W, is strongly affected by carbon concentration in the plasma and the magnetic pre-sheath properties. We have investigated different methods such as electrical biasing and local gas injection to control high-Z material erosion. The net erosion rate of high-Z materials is significantly reduced due to the high local re-deposition ratio. The ERO modeling shows that the local re-deposition ratio is mainly controlled by the electric field and plasma density within the magnetic pre-sheath. The net erosion can be significantly suppressed by reducingmore » the sheath potential drop. A high carbon impurity concentration in the background plasma is also found to reduce the net erosion rate of high-Z materials. Both DIII-D experiments and modeling show that local 13CH 4 injection can create a carbon coating on the metal surface. The profile of 13C deposition provides quantitative information on radial transport due to E × B drift and the cross-field diffusion. The deuterium gas injection upstream of the W sample can reduce W net erosion rate by plasma perturbation. The inter-ELM W erosion we measured in H-mode plasmas, rates at different radial locations are well reproduced by ERO modeling taking into account charge-state-resolved carbon ion flux in the background plasma calculated using the OEDGE code.« less

Linear response of stretch-affected premixed flames to flow oscillations

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

Wang, H.Y.; Law, C.K.; Lieuwen, T.

2009-04-15

The linear response of 2D wedge-shaped premixed flames to harmonic velocity disturbances was studied, allowing for the influence of flame stretch manifested as variations in the local flame speed along the wrinkled flame front. Results obtained from analyzing the G-equation show that the flame response is mainly characterized by a Markstein number {sigma}{sub C}, which measures the curvature effect of the wrinkles, and a Strouhal number, St{sub f}, defined as the angular frequency of the disturbance normalized by the time taken for the disturbance to propagate the flame length. Flame stretch is found to become important when the disturbance frequencymore » satisfies {sigma}{sub C}St{sub f}{sup 2}{proportional_to} O(1), i.e. St{sub f}{proportional_to} O({sigma}{sub C}{sup -1/2}). Specifically, for disturbance frequencies below this order, stretch effects are small and the flame responds as an unstretched one. When the disturbance frequencies are of this order, the transfer function, defined as the ratio of the normalized fluctuation of the heat release rate to that of the velocity, is contributed mostly from fluctuations of the flame surface area, which is now affected by stretch. Finally, as the disturbance frequency increases to St{sub f}{proportional_to} O({sigma}{sub C}{sup -1}), i.e. {sigma}{sub C}St{sub f}{proportional_to} O(1), the direct contribution from the stretch-affected flame speed fluctuation to the transfer function becomes comparable to that of the flame surface area. The present study phenomenologically explains the experimentally observed filtering effect in which the flame wrinkles developed at the flame base decay along the flame surface for large frequency disturbances as well as for thermal-diffusively stable and weakly unstable mixtures. (author)« less

Determination of elemental impurities and U and O isotopic compositions with a view to identify the geographical and industrial origins of uranium ore concentrates

NASA Astrophysics Data System (ADS)

Salaun, A.; Hubert, A.; Pointurier, F.; Aupiais, J.; Pili, E.; Richon, P.; Fauré, A.; Diallo, S.

2012-12-01

First events of illicit trafficking of nuclear and radiological materials occurred 50 years ago. Nuclear forensics expertise are aiming at determining the use of seized material, its industrial history and provenance (geographical area, place of production or processing), at assisting in the identification and dismantling of illicit trafficking networks. This information is also valuable in the context of inspections of declared facilities to verify the consistency of operator's declaration. Several characteristics can be used to determine the origin of uranium ore concentrates such as trace elemental impurity patterns (Keegan et al., 2008 ; Varga et al., 2010a, 2010b) or uranium, oxygen and lead isotopic compositions (Tamborini et al., 2002a, 2002b ; Wallenius et al., 2006; Varga et al., 2009). We developed analytical procedures for measuring the isotopic compositions of uranium (234U/238U and 235U/238U) and oxygen (18O/16O) and levels of elemental impurities (e.g. REE, Th) from very small amounts of uranium ore concentrates (or yellow cakes). Micrometer particles and few milligrams of material are used for oxygen isotope measurements and REE determination, respectively. Reference materials were analyzed by mass spectrometry (TIMS, SF-ICP-MS and SIMS) to validate testing protocols. Finally, materials of unknown origin were analyzed to highlight significant differences and determine whether these differences allow identifying the origin of these ore concentrates. References: Keegan, E., et al. (2008). Applied Geochemistry 23, 765-777. Tamborini, G., et al. (2002a). Analytical Chemistry 74, 6098-6101. Tamborini, G., et al. (2002b). Microchimica Acta 139, 185-188. Varga, Z., et al. (2009). Analytical Chemistry 81, 8327-8334. Varga, Z., et al. (2010a). Talanta 80, 1744-1749. Varga, Z., et al. (2010b). Radiochimica Acta 98, 771-778 Wallenius, M., et al. (2006). Forensic Science International 156, 55-62.

Gas-phase measurements of combustion interaction with materials for radiation-cooled chambers

NASA Technical Reports Server (NTRS)

Barlow, R. S.; Lucht, R. P.; Jassowski, D. M.; Rosenberg, S. D.

1991-01-01

Foil samples of Ir and Pt are exposed to combustion products in a controlled premixed environment at atmospheric pressure. Electrical heating of the foil samples is used to control the surface temperature and to elevate it above the radiative equilibrium temperature within the test apparatus. Profiles of temperature and OH concentration in the boundary layer adjacent to the specimen surface are measured by laser-induced fluorescence. Measured OH concentrations are significantly higher than equilibrium concentrations calculated for the known mixture ratio and the measured temperature profiles. This result indicates that superequilibrium concentrations of H-atoms and O-atoms are also present in the boundary layer, due to partial equilibrium of the rapid binary reactions of the H2/O2 chemical kinetic system. These experiments are conducted as part of a research program to investigate fundamental aspects of the interaction of combustion gases with advanced high-temperature materials for radiation-cooled thrusters.

Effect of fuel stratification on detonation wave propagation

NASA Astrophysics Data System (ADS)

Masselot, Damien; Fievet, Romain; Raman, Venkat

2016-11-01

Rotating detonation engines (RDEs) form a class of pressure-gain combustion systems of higher efficiency compared to conventional gas turbine engines. One of the key features of the design is the injection system, as reactants need to be continuously provided to the detonation wave to sustain its propagation speed. As inhomogeneities in the reactant mixture can perturb the detonation wave front, premixed fuel jet injectors might seem like the most stable solution. However, this introduces the risk of the detonation wave propagating through the injector, causing catastrophic failure. On the other hand, non-premixed fuel injection will tend to quench the detonation wave near the injectors, reducing the likelihood of such failure. Still, the effects of such non-premixing and flow inhomogeneities ahead of a detonation wave have yet to be fully understood and are the object of this study. A 3D channel filled with O2 diluted in an inert gas with circular H2 injectors is simulated as a detonation wave propagates through the system. The impact of key parameters such as injector spacing, injector size, mixture composition and time variations will be discussed. PhD Candidate.

Effects of pressure fluctuations on the combustion process in turbulent premixed flames

NASA Astrophysics Data System (ADS)

Beardsell, Guillaume; Lapointe, Simon; Blanquart, Guillaume

2016-11-01

The need for a thorough understanding of turbulence-combustion interactions in compressible flows is driven by recent technological developments in propulsion as well as renewed interest in the development of next generation supersonic and hypersonic vehicles. In such flows, pressure fluctuations displaying a wide range of length and timescales are present. These fluctuations are expected to impact the combustion process to varying degrees, depending amongst other things on the amplitude of the pressure variations and the timescales of the chemical reactions taking place in the flame. In this context, numerical simulations of these flows can provide insight into the impact of pressure fluctuations on the combustion process. In the present work, we analyze data from simulations of statistically-flat premixed n-heptane/air flames at high Karlovitz numbers. The compressible Navier-Stokes equations are solved exactly (DNS) and results obtained with both detailed kinetic modeling and one-step chemistry are considered. The effects of pressure fluctuations on the fuel burning rate are investigated. The findings are compared with results obtained from simulations of one-dimensional premixed flames subjected to various pressure waves.

Impact of biogenic nanoscale metals Fe, Cu, Zn and Se on reproductive LV chickens

NASA Astrophysics Data System (ADS)

Khiem Nguyen, Quy; Dieu Nguyen, Duy; Kien Nguyen, Van; Thinh Nguyen, Khac; Chau Nguyen, Hoai; Tin Tran, Xuan; Nguyen, Huu Cuong; Tien Phung, Duc

2015-09-01

Using biogenic nanoscale metals (Fe, Cu, ZnO, Se) to supplement into diet premix of reproductive LV (a Vietnamese Luong Phuong chicken breed) chickens resulted in certain improvement of poultry farming. The experimental data obtained showed that the farming indices depend mainly on the quantity of nanocrystalline metals which replaced the inorganic mineral component in the feed premix. All four experimental groups with different quantities of the replacement nano component grew and developed normally with livability reaching 91 to 94%, hen’s bodyweight at 38 weeks of age and egg weight ranged from 2.53-2.60 kg/hen and 50.86-51.55 g/egg, respectively. All these farming indices together with laying rate, egg productivity and chick hatchability peaked at group 5 with 25% of nanoscale metals compared to the standard inorganic mineral supplement, while feed consumption was lowest. The results also confirmed that nanocrystalline metals Fe, Cu, ZnO and Se supplemented to chicken feed were able to decrease inorganic minerals in the diet premixes at least four times, allowing animals to more effectively absorb feed minerals, consequently decreasing environmental pollution risks.

Velocity and Reactive Scalar Dissipation Spectra in Turbulent Premixed Flames

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

Kolla, Hemanth; Zhao, Xin-Yu; Chen, Jacqueline H.

Dissipation spectra of velocity and reactive scalars—temperature and fuel mass fraction—in turbulent premixed flames are studied using direct numerical simulation data of a temporally evolving lean hydrogen-air premixed planar jet (PTJ) flame and a statistically stationary planar lean methane-air (SP) flame. Furthermore, the equivalence ratio in both cases was 0.7, the pressure 1 atm while the unburned temperature was 700 K for the hydrogen-air PTJ case and 300 K for methane-air SP case, that resulted in data sets with a density ratio of 3 and 5, respectively. The turbulent Reynolds numbers for the cases ranged from 200 to 428.4, themore » Damköhler number from 3.1 to 29.1, and the Karlovitz number from 0.1 to 4.5. The dissipation spectra collapse when normalized by the respective Favre-averaged dissipation rates. But, the normalized dissipation spectra in all the cases deviate noticeably from those predicted by classical scaling laws for constant-density turbulent flows and bear a clear influence of the chemical reactions on the dissipative range of the energy cascade.« less

A conservative, thermodynamically consistent numerical approach for low Mach number combustion. Part I: Single-level integration

NASA Astrophysics Data System (ADS)

Nonaka, Andrew; Day, Marcus S.; Bell, John B.

2018-01-01

We present a numerical approach for low Mach number combustion that conserves both mass and energy while remaining on the equation of state to a desired tolerance. We present both unconfined and confined cases, where in the latter the ambient pressure changes over time. Our overall scheme is a projection method for the velocity coupled to a multi-implicit spectral deferred corrections (SDC) approach to integrate the mass and energy equations. The iterative nature of SDC methods allows us to incorporate a series of pressure discrepancy corrections naturally that lead to additional mass and energy influx/outflux in each finite volume cell in order to satisfy the equation of state. The method is second order, and satisfies the equation of state to a desired tolerance with increasing iterations. Motivated by experimental results, we test our algorithm on hydrogen flames with detailed kinetics. We examine the morphology of thermodiffusively unstable cylindrical premixed flames in high-pressure environments for confined and unconfined cases. We also demonstrate that our algorithm maintains the equation of state for premixed methane flames and non-premixed dimethyl ether jet flames.

Laminar soot processes

NASA Technical Reports Server (NTRS)

Sunderland, P. B.; Lin, K.-C.; Faeth, G. M.

1995-01-01

Soot processes within hydrocarbon fueled flames are important because they affect the durability and performance of propulsion systems, the hazards of unwanted fires, the pollutant and particulate emissions from combustion processes, and the potential for developing computational combustion. Motivated by these observations, the present investigation is studying soot processes in laminar diffusion and premixed flames in order to better understand the soot and thermal radiation emissions of luminous flames. Laminar flames are being studied due to their experimental and computational tractability, noting the relevance of such results to practical turbulent flames through the laminar flamelet concept. Weakly-buoyant and nonbuoyant laminar diffusion flames are being considered because buoyancy affects soot processes in flames while most practical flames involve negligible effects of buoyancy. Thus, low-pressure weakly-buoyant flames are being observed during ground-based experiments while near atmospheric pressure nonbuoyant flames will be observed during space flight experiments at microgravity. Finally, premixed laminar flames also are being considered in order to observe some aspects of soot formation for simpler flame conditions than diffusion flames. The main emphasis of current work has been on measurements of soot nucleation and growth in laminar diffusion and premixed flames.

Experimental study of wood downdraft gasification for an improved producer gas quality through an innovative two-stage air and premixed air/gas supply approach.

PubMed

Jaojaruek, Kitipong; Jarungthammachote, Sompop; Gratuito, Maria Kathrina B; Wongsuwan, Hataitep; Homhual, Suwan

2011-04-01

This study conducted experiments on three different downdraft gasification approaches: single stage, conventional two-stage, and an innovative two-stage air and premixed air/gas supply approach. The innovative two-stage approach has two nozzle locations, one for air supply at combustion zone and the other located at the pyrolysis zone for supplying the premixed gas (air and producer gas). The producer gas is partially bypassed to mix with air and supplied to burn at the pyrolysis zone. The result shows that producer gas quality generated by the innovative two-stage approach improved as compared to conventional two-stage. The higher heating value (HHV) increased from 5.4 to 6.5 MJ/Nm(3). Tar content in producer gas reduced to less than 45 mg/Nm(3). With this approach, gas can be fed directly to an internal combustion engine. Furthermore, the gasification thermal efficiency also improved by approximately 14%. The approach gave double benefits on gas qualities and energy savings. Copyright © 2010 Elsevier Ltd. All rights reserved.

Effects of porous insert on flame dynamics in a lean premixed swirl-stabilized combustor

NASA Astrophysics Data System (ADS)

Brown, Marcus; Agrawal, Ajay; Allen, James; Kornegay, John

2016-11-01

In this study, we investigated different methods of determining the effect a porous insert has on flame dynamics during lean premixed combustion. A metallic porous insert is used to mitigate instabilities in a swirl-stabilized combustor. Thermoacoustic instabilities are seen as negative consequences of lean premixed combustion and eliminating them is the motivation for our research. Three different diagnostics techniques with high-speed Photron SA5 cameras were used to monitor flame characteristics. Particle image velocimetry (PIV) was used to observe vortical structures and recirculation zones within the combustor. Using planar laser induced fluorescence (PLIF), we were able to observe changes in the reaction zones during instabilities. Finally, utilizing a color high-speed camera, visual images depicting a flame's oscillations during the instability were captured. Using these monitoring techniques, we are able to support the claims made in previous studies stating that the porous insert in the combustor significantly reduces the thermoacoustic instability. Funding for this research was provided by the NSF REU site Grant EEC 1358991 and NASA Grant NNX13AN14A.

Velocity and Reactive Scalar Dissipation Spectra in Turbulent Premixed Flames

DOE PAGES

Kolla, Hemanth; Zhao, Xin-Yu; Chen, Jacqueline H.; ...

2016-06-09

Dissipation spectra of velocity and reactive scalars—temperature and fuel mass fraction—in turbulent premixed flames are studied using direct numerical simulation data of a temporally evolving lean hydrogen-air premixed planar jet (PTJ) flame and a statistically stationary planar lean methane-air (SP) flame. Furthermore, the equivalence ratio in both cases was 0.7, the pressure 1 atm while the unburned temperature was 700 K for the hydrogen-air PTJ case and 300 K for methane-air SP case, that resulted in data sets with a density ratio of 3 and 5, respectively. The turbulent Reynolds numbers for the cases ranged from 200 to 428.4, themore » Damköhler number from 3.1 to 29.1, and the Karlovitz number from 0.1 to 4.5. The dissipation spectra collapse when normalized by the respective Favre-averaged dissipation rates. But, the normalized dissipation spectra in all the cases deviate noticeably from those predicted by classical scaling laws for constant-density turbulent flows and bear a clear influence of the chemical reactions on the dissipative range of the energy cascade.« less

On the modelling of non-reactive and reactive turbulent combustor flows

NASA Technical Reports Server (NTRS)

Nikjooy, Mohammad; So, Ronald M. C.

1987-01-01

A study of non-reactive and reactive axisymmetric combustor flows with and without swirl is presented. Closure of the Reynolds equations is achieved by three models: kappa-epsilon, algebraic stress and Reynolds stress closure. Performance of two locally nonequilibrium and one equilibrium algebraic stress models is analyzed assuming four pressure strain models. A comparison is also made of the performance of a high and a low Reynolds number model for combustor flow calculations using Reynolds stress closures. Effects of diffusion and pressure-strain models on these closures are also investigated. Two models for the scalar transport are presented. One employs the second-moment closure which solves the transport equations for the scalar fluxes, while the other solves the algebraic equations for the scalar fluxes. In addition, two cases of non-premixed and one case of premixed combustion are considered. Fast- and finite-rate chemistry models are applied to non-premixed combustion. Both show promise for application in gas turbine combustors. However, finite rate chemistry models need to be examined to establish a suitable coupling of the heat release effects on turbulence field and rate constants.

Direct numerical simulations of flow-chemistry interactions in statistically turbulent premixed flames

NASA Astrophysics Data System (ADS)

Arias, Paul; Uranakar, Harshavardhana; Chaudhuri, Swetaprovo; Im, Hong

2015-11-01

The effects of Damköhler number and Karlovitz number on the flame dynamics of three-dimensional statistically planar turbulent premixed flames are investigated by direct numerical simulation incorporating detailed chemistry and transport for a hydrogen-air mixture. The mean inlet velocity was dynamically adjusted to ensure a stable flame within the computational domain, allowing the investigation of time-averaged quantities of interest. A particular interest was on understanding the effects of turbulence on the displacement speed of the flame relative to the local fluid flow. Results show a linear dependence on the displacement speed as a function of total strain, consistent with earlier work on premixed-laminar flames. Additional analysis on the local flame thickness reveals that the effect of turbulence is twofold: (1) the increase in mixing results in flame thinning due to the enhancement of combustion at early onset of the flame, and (2) for large Reynolds number flows, the penetration of the turbulence far into the preheat zone and into the reaction zone results in localized flame broadening.

Compact low-noise preamplifier for noise spectroscopy with biased photodiodes in cargo inspection systems

NASA Astrophysics Data System (ADS)

Benetti, Bob; Langeveld, Willem G. J.

2013-09-01

Noise Spectroscopy, a.k.a. Z-determination by Statistical Count-rate ANalysis (Z-SCAN), is a statistical technique to determine a quantity called the "noise figure" from digitized waveforms of pulses of transmitted x-rays in cargo inspection systems. Depending only on quantities related to the x-ray energies, it measures a characteristic of the transmitted x-ray spectrum, which depends on the atomic number, Z, of the material penetrated. The noise figure can thus be used for material separation. In an 80-detector prototype, scintillators are used with large-area photodiodes biased at 80V and digitized using 50-MSPS 12-bit ADC boards. We present an ultra-compact low-noise preamplifier design, with one high-gain and one low-gain channel per detector for improved dynamic range. To achieve adequate detection sensitivity and spatial resolution each dual-gain preamplifier channel must fit within a 12.7 mm wide circuit board footprint and maintain adequate noise immunity to conducted and radiated interference from adjacent channels. The novel design included iterative SPICE analysis of transient response, dynamic range, frequency response, and noise analysis to optimize the selection and configuration of amplifiers and filter response. We discuss low-noise active and passive components and low-noise techniques for circuit board layout that are essential to achieving the design goals, and how the completed circuit board performed in comparison to the predicted responses.

The Difference Quantity of Urinary Peptides between Two Groups of Type 2 Diabetic Patients with or without Coronary Artery Disease

PubMed Central

Fu, Guangzhen; Hu, Mei; Chu, Lina; Zhang, Man

2015-01-01

Objectives. We aim to explore urinary biomarkers that could monitor CAD in type 2 diabetic patients. Materials and Methods. Urine samples from two groups, twenty-eight type 2 diabetic patients with coexisting CAD and thirty type 2 diabetic patients without CAD, were purified by MB-WCX and then analyzed by MALDI-TOF-MS. Subsequently, we compared the urinary peptide signatures of the two groups by use of ClinProTools2.1 and evaluated the potential ability of the differently expressed peptides to distinguish type 2 diabetic patients with coexisting CAD from type 2 diabetic patients without CAD by ROC analysis. Finally, the differently expressed peptides were identified by nanoliquid chromatography-tandem mass spectrometry. Results. There were six differently expressed peptides (m/z 1305.2, 1743.9, 2184.9, 2756.1, 3223.2, and 6196.1) between the two groups of subjects, and they were identified as fragments of isoform 1 of fibrinogen alpha chain precursor, prothrombin precursor, and interalpha-trypsin inhibitor heavy chain H4. The diagnostic efficacy of m/z 2756.1 and m/z 3223.2 was better than the other peptides. Area under ROC of the m/z 2756.1, and m/z 3223.2 was 0.98 and 0.93, respectively. Conclusions. These urinary peptides are potential urinary biomarkers for monitoring of type 2 diabetic patients with CAD. PMID:26089891

Department of Defense Advisory Group on Electron Devices. Special Technology Area Review on Microwave Packaging Technology. Appendix

DTIC Science & Technology

1993-02-01

sintered in hydrogen furnace at very high temperatures . Multiple furnace firing occurs until the binders are removed and part density is achieved "* Process...and base Low temperature co-fired ceramic - Metallized for shielding and grounding - Low resistance thick-film metallization - High thermal resistance...ESPECIALLY LOW TEMPERATURE COFIRED CERAMIC CERAMICS HIGH THERMAL CONDUCTIVITY,MATCHED GaAS AND SILICON SUBSTRATE MATERIALS I I,1Z#A,17Mr1 J, TI

New Standard Weir Design for Dredged Material Management Area, Jacksonville District

DTIC Science & Technology

2014-08-01

dock access, Bartram Island Cell B2, Jacksonville, Florida. Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for...Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 ERDC/TN DOTS-14-01 August 2014 2 US Army Corps of Engineers • Engineer Research...and through the riser stack of weir boards. This requires secondary sealing measures in the form of plastic sheeting, geotextiles, and/or burlap

Ultra-wideband impedance sensor

DOEpatents

McEwan, Thomas E.

1999-01-01

The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks.

Ultra-wideband impedance sensor

DOEpatents

McEwan, T.E.

1999-03-16

The ultra-wideband impedance sensor (UWBZ sensor, or Z-sensor) is implemented in differential and single-ended configurations. The differential UWBZ sensor employs a sub-nanosecond impulse to determine the balance of an impedance bridge. The bridge is configured as a differential sample-and-hold circuit that has a reference impedance side and an unknown impedance side. The unknown impedance side includes a short transmission line whose impedance is a function of the near proximity of objects. The single-ended UWBZ sensor eliminates the reference side of the bridge and is formed of a sample and hold circuit having a transmission line whose impedance is a function of the near proximity of objects. The sensing range of the transmission line is bounded by the two-way travel time of the impulse, thereby eliminating spurious Doppler modes from large distant objects that would occur in a microwave CW impedance bridge. Thus, the UWBZ sensor is a range-gated proximity sensor. The Z-sensor senses the near proximity of various materials such as metal, plastic, wood, petroleum products, and living tissue. It is much like a capacitance sensor, yet it is impervious to moisture. One broad application area is the general replacement of magnetic sensors, particularly where nonferrous materials need to be sensed. Another broad application area is sensing full/empty levels in tanks, vats and silos, e.g., a full/empty switch in water or petroleum tanks. 2 figs.

Infrared Preheating to Enhance Interlayer Strength of Components Printed on the Big Area Additive Manufacturing (BAAM) System

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

Kishore, Vidya; Ajinjeru, Christine; Duty, Chad E

The Big Area Additive Manufacturing (BAAM) system has the capacity to print structures on the order of several meters at a rate exceeding 50 kg/h, thereby having the potential to significantly impact the production of components in automotive, aerospace and energy sectors. However, a primary issue that limits the functional use of such parts is mechanical anisotropy. The strength of printed parts across successive layers in the build direction (z-direction) is significantly lower than the corresponding in-plane strength (x-y directions). This is largely due to poor bonding between the printed layers as the lower layers cool below the glass transitionmore » temperature (Tg) before the next layer is deposited. This work explores the use of infrared heating to increase the surface temperature of the printed layer just prior to deposition of new material to improve the interlayer strength of the components. The material used in this study was acrylonitrile butadiene styrene (ABS) reinforced with 20% chopped carbon fiber by weight. Significant improvements in z-strength were observed for the parts whose surface temperature was increased from below Tg to close to or above Tg using infrared heating. Parameters such as print speed, nozzle diameter and extrusion temperature were also found to impact the heat input required to enhance interlayer adhesion without significantly degrading the polymer and compromising on surface finish.« less

High-Resolution OH and CH2O Visualization in a Premixed Cavity-Anchored Ethylene-Air Flame in a M = 0.6 Flowfield

NASA Technical Reports Server (NTRS)

Geipel, Clayton M.; Rockwell, Robert D.; Chelliah, Harsha K.; Cutler, Andrew D.; Spelker, Christopher A.; Hashem, Zeid; Danehy, Paul M.

2017-01-01

OH and CH2O were imaged in a premixed, cavity-anchored, ethylene-air turbulent flame using a high resolution planar laser-induced fluorescence (PLIF) system. The electrically-heated, continuous flow facility (UVa Supersonic Combustion Facility, Configuration E) consisted of a Mach 2 nozzle, an isolator with fuel injectors, a test section with a cavity flame holder and optical access, and an extender. Standard test conditions comprised total temperature 1200 K, total pressure 300 kPa, local equivalence ratio near 0.4, and local Mach number near 0.6. OH PLIF data was also collected for a case with reduced total temperature and another with reduced equivalence ratio. OH and CH2O were excited in separate experiments with light sheets at 283.55 nm and 352.48 nm, respectively. A light sheet of approximate thickness 25 ?m illuminated the stream-wise midplane. This plane was imaged for 120 mm downstream of the backward-facing step. The intensified camera system imaged OH with magnification 1.97, a square 6.67 mm field of view, and in-plane resolution of 39 ?m. The smallest observed OH structures observed were approximately 100 ?m wide. The CH2O PLIF image signal was much weaker; the smallest observed structures were approximately 200 ?m wide. Composite fluorescence images were computed for the observed area.

Emission characteristics of a premix combustor fueled with a simulated partial-oxidation product gas

NASA Technical Reports Server (NTRS)

Clayton, R. M.

1979-01-01

A two-stage gas turbine combustor concept employing a very fuel-rich partial oxidation stage is being explored for broadening the combustion margin between ultralow emissions and the lean stability limit. Combustion and emission results are presented for a series of experiments where a simulated partial oxidation product gas was used in a premix combustor operated with inlet air state conditions typical of cruise power for high-performance aviation engines (12 atm and 850 F). Ultralow NOx, CO, and HC emissions and an extended lean burning limit were achieved simultaneously.

Pdf prediction of supersonic hydrogen flames

NASA Technical Reports Server (NTRS)

Eifler, P.; Kollmann, W.

1993-01-01

A hybrid method for the prediction of supersonic turbulent flows with combustion is developed consisting of a second order closure for the velocity field and a multi-scalar pdf method for the local thermodynamic state. It is shown that for non-premixed flames and chemical equilibrium mixture fraction, the logarithm of the (dimensionless) density, internal energy per unit mass and the divergence of the velocity have several advantages over other sets of scalars. The closure model is applied to a supersonic non-premixed flame burning hydrogen with air supplied by a supersonic coflow and the results are compared with a limited set of experimental data.

The A to Z of pharmaceutical cocrystals: a decade of fast-moving new science and patents.

PubMed

Almarsson, Örn; Peterson, Matthew L; Zaworotko, Michael

2012-07-01

From aspirin to zoledronic acid, pharmaceutical cocrystals emerged in the past decade as a promising new weapon in the arsenal of drug development. Resurgence of interest in multicomponent crystal compositions has led to significant advances in the science of cocrystal design and discovery. These advances have built upon crystal engineering, which provides a deep understanding of supramolecular interactions between molecules that govern crystal packing and physicochemical properties of crystalline materials. Concomitantly, the patent landscape of pharmaceutical cocrystals developed rapidly in the last decade. This review presents a broad survey of patents issued in the area of pharmaceutical cocrystals. In addition, the review contains analyses of key patents in the area involving compositions and methodologies. Along the way, the main events of the past decade representing a renaissance of cocrystals of pharmaceutical materials are chronicled. Future directions in the area are discussed in light of key pending patent applications and recent publications of seminal interest.

Prototype of a Muon Tomography Station with GEM detectors for Detection of Shielded Nuclear Contraband

NASA Astrophysics Data System (ADS)

Staib, Michael; Bhopatkar, Vallary; Bittner, William; Hohlmann, Marcus; Locke, Judson; Twigger, Jessie; Gnanvo, Kondo

2012-03-01

Muon tomography for homeland security aims at detecting well-shielded nuclear contraband in cargo and imaging it in 3D. The technique exploits multiple scattering of atmospheric cosmic ray muons, which is stronger in dense, high-Z materials, e.g. enriched uranium, than in low-Z and medium-Z shielding materials. We have constructed and are operating a compact Muon Tomography Station (MTS) that tracks muons with eight 30 cm x 30 cm Triple Gas Electron Multiplier (GEM) detectors placed on the sides of a cubic-foot imaging volume. A point-of-closest-approach algorithm applied to reconstructed incident and exiting tracks is used to create a tomographic reconstruction of the material within the active volume. We discuss the performance of this MTS prototype including characterization and commissioning of the GEM detectors and the data acquisition systems. We also present experimental tomographic images of small high-Z objects including depleted uranium with and without shielding and discuss the performance of material discrimination using this method.

Compound refractive X-ray lens

DOEpatents

Nygren, David R.; Cahn, Robert; Cederstrom, Bjorn; Danielsson, Mats; Vestlund, Jonas

2000-01-01

An apparatus and method for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point.

Mitigating the Effects of the Space Radiation Environment: A Novel Approach of Using Graded-Z Materials

NASA Technical Reports Server (NTRS)

Atwell, William; Rojdev, Kristina; Aghara, Sukesh; Sriprisan, Sirikul

2013-01-01

In this paper we present a novel space radiation shielding approach using various material lay-ups, called "Graded-Z" shielding, which could optimize cost, weight, and safety while mitigating the radiation exposures from the trapped radiation and solar proton environments, as well as the galactic cosmic radiation (GCR) environment, to humans and electronics. In addition, a validation and verification (V&V) was performed using two different high energy particle transport/dose codes (MCNPX & HZETRN). Inherently, we know that materials having high-hydrogen content are very good space radiation shielding materials. Graded-Z material lay-ups are very good trapped electron mitigators for medium earth orbit (MEO) and geostationary earth orbit (GEO). In addition, secondary particles, namely neutrons, are produced as the primary particles penetrate a spacecraft, which can have deleterious effects to both humans and electronics. The use of "dopants," such as beryllium, boron, and lithium, impregnated in other shielding materials provides a means of absorbing the secondary neutrons. Several examples of optimized Graded-Z shielding layups that include the use of composite materials are presented and discussed in detail. This parametric shielding study is an extension of some earlier pioneering work we (William Atwell and Kristina Rojdev) performed in 20041 and 20092.

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

Sharp, D.J.; Panitz, J.K.G.; Mattox, D.M.

The erosion of materials by low energy ions is of concern in fusion reactors since high Z impurities in the plasma cause radiation cooling. Ion bombardment of the fusion reactor chamber walls arises from ions of fuel (D, T) material, gaseous impurities (O, C), and impurities from eroded components (Fe, Co, Ni, C, Mo, etc.) being accelerated across the wall sheath potential (0.1 to 1 keV). A Kaufman type ion source has been characterized for use with hydrogen, and subsequently used to determine the relative erosion rates of bulk Mo, C, Cu, coating of TiB/sub 2/, B/sub 4/C, Be, VBe/submore » 12/ and other materials. Ions of hydrogen (Z=1), argon (Z=18), and xenon (Z=54) at acceleration potentials of 250, 500, and 1000 V have been used to determine erosion yields.« less

Effect of different impression materials and techniques on the dimensional accuracy of implant definitive casts

PubMed Central

Ebadian, Behnaz; Rismanchian, Mansor; Dastgheib, Badrosadat; Bajoghli, Farshad

2015-01-01

Background: Different factors such as impression techniques and materials can affect the passive fit between the superstructure and implant. The aim of this study was to determine the effect of different impression materials and techniques on the dimensional accuracy of implant definitive casts. Materials and Methods: Four internal hex implants (Biohorizons Ø4 mm) were placed on a metal maxillary model perpendicular to the horizontal plane in maxillary lateral incisors, right canine and left first premolar areas. Three impression techniques including open tray, closed tray using ball top screw abutments and closed tray using short impression copings and two impression materials (polyether and polyvinyl siloxane) were evaluated (n = 60). The changes in distances between implant analogues in mediolateral (x) and anteroposterior (y) directions and analogue angles in x/z and y/z directions in the horizontal plane on the definitive casts were measured by coordinate measuring machine. The data were analyzed by multivariate two-way analysis of variance and one sample t-test (α = 0.05). Results: No statistical significant differences were observed between different impression techniques and materials. However, deviation and distortion of definitive casts had a significant difference with the master model when short impression copings and polyvinyl siloxane impression material were used (P < 0.05). In open tray technique, there was a significant difference in the rotation of analogs compared with the master model with both impression materials (P < 0.05). Conclusion: There was no difference between open and closed tray impression techniques; however, less distortion and deviation were observed in the open tray technique. In the closed tray impression technique, ball top screw was more accurate than short impression copings. PMID:25878678

Multi-MW accelerator target material properties under proton irradiation at Brookhaven National Laboratory linear isotope producer

DOE PAGES

Simos, N.; Ludewig, H.; Kirk, H.; ...

2018-05-29

The effects of proton beams irradiating materials considered for targets in high-power accelerator experiments have been studied using the Brookhaven National Laboratory’s (BNL) 200 MeV proton linac. A wide array of materials and alloys covering a wide range of the atomic number (Z) are being scoped by the high-power accelerator community prompting the BNL studies to focus on materials representing each distinct range, i.e. low-Z, mid-Z and high-Z. The low range includes materials such as beryllium and graphite, the midrange alloys such as Ti-6Al-4V, gum metal and super-Invar and finally the high-Z range pure tungsten and tantalum. Of interest inmore » assessing proton irradiation effects are (a) changes in physiomechanical properties which are important in maintaining high-power target functionality, (b) identification of possible limits of proton flux or fluence above which certain materials cease to maintain integrity, (c) the role of material operating temperature in inducing or maintaining radiation damage reversal, and (d) phase stability and microstructural changes. The paper presents excerpt results deduced from macroscopic and microscopic post-irradiation evaluation (PIE) following several irradiation campaigns conducted at the BNL 200 MeV linac and specifically at the isotope producer beam-line/target station. The microscopic PIE relied on high energy x-ray diffraction at the BNL NSLS X17B1 and NSLS II XPD beam lines. The studies reveal the dramatic effects of irradiation on phase stability in several of the materials, changes in physical properties and ductility loss as well as thermally induced radiation damage reversal in graphite and alloys such as super-Invar.« less

Multi-MW accelerator target material properties under proton irradiation at Brookhaven National Laboratory linear isotope producer

NASA Astrophysics Data System (ADS)

Simos, N.; Ludewig, H.; Kirk, H.; Dooryhee, E.; Ghose, S.; Zhong, Z.; Zhong, H.; Makimura, S.; Yoshimura, K.; Bennett, J. R. J.; Kotsinas, G.; Kotsina, Z.; McDonald, K. T.

2018-05-01

The effects of proton beams irradiating materials considered for targets in high-power accelerator experiments have been studied using the Brookhaven National Laboratory's (BNL) 200 MeV proton linac. A wide array of materials and alloys covering a wide range of the atomic number (Z) are being scoped by the high-power accelerator community prompting the BNL studies to focus on materials representing each distinct range, i.e. low-Z, mid-Z and high-Z. The low range includes materials such as beryllium and graphite, the midrange alloys such as Ti-6Al-4V, gum metal and super-Invar and finally the high-Z range pure tungsten and tantalum. Of interest in assessing proton irradiation effects are (a) changes in physiomechanical properties which are important in maintaining high-power target functionality, (b) identification of possible limits of proton flux or fluence above which certain materials cease to maintain integrity, (c) the role of material operating temperature in inducing or maintaining radiation damage reversal, and (d) phase stability and microstructural changes. The paper presents excerpt results deduced from macroscopic and microscopic post-irradiation evaluation (PIE) following several irradiation campaigns conducted at the BNL 200 MeV linac and specifically at the isotope producer beam-line/target station. The microscopic PIE relied on high energy x-ray diffraction at the BNL NSLS X17B1 and NSLS II XPD beam lines. The studies reveal the dramatic effects of irradiation on phase stability in several of the materials, changes in physical properties and ductility loss as well as thermally induced radiation damage reversal in graphite and alloys such as super-Invar.

Multi-MW accelerator target material properties under proton irradiation at Brookhaven National Laboratory linear isotope producer

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

Simos, N.; Ludewig, H.; Kirk, H.

The effects of proton beams irradiating materials considered for targets in high-power accelerator experiments have been studied using the Brookhaven National Laboratory’s (BNL) 200 MeV proton linac. A wide array of materials and alloys covering a wide range of the atomic number (Z) are being scoped by the high-power accelerator community prompting the BNL studies to focus on materials representing each distinct range, i.e. low-Z, mid-Z and high-Z. The low range includes materials such as beryllium and graphite, the midrange alloys such as Ti-6Al-4V, gum metal and super-Invar and finally the high-Z range pure tungsten and tantalum. Of interest inmore » assessing proton irradiation effects are (a) changes in physiomechanical properties which are important in maintaining high-power target functionality, (b) identification of possible limits of proton flux or fluence above which certain materials cease to maintain integrity, (c) the role of material operating temperature in inducing or maintaining radiation damage reversal, and (d) phase stability and microstructural changes. The paper presents excerpt results deduced from macroscopic and microscopic post-irradiation evaluation (PIE) following several irradiation campaigns conducted at the BNL 200 MeV linac and specifically at the isotope producer beam-line/target station. The microscopic PIE relied on high energy x-ray diffraction at the BNL NSLS X17B1 and NSLS II XPD beam lines. The studies reveal the dramatic effects of irradiation on phase stability in several of the materials, changes in physical properties and ductility loss as well as thermally induced radiation damage reversal in graphite and alloys such as super-Invar.« less

Local curvature measurements of a lean, partially premixed swirl-stabilised flame

NASA Astrophysics Data System (ADS)

Bayley, Alan E.; Hardalupas, Yannis; Taylor, Alex M. K. P.

2012-04-01

A swirl-stabilised, lean, partially premixed combustor operating at atmospheric conditions has been used to investigate the local curvature distributions in lifted, stable and thermoacoustically oscillating CH4-air partially premixed flames for bulk cold-flow Reynolds numbers of 15,000 and 23,000. Single-shot OH planar laser-induced fluorescence has been used to capture instantaneous images of these three different flame types. Use of binary thresholding to identify the reactant and product regions in the OH planar laser-induced fluorescence images, in order to extract accurate flame-front locations, is shown to be unsatisfactory for the examined flames. The Canny-Deriche edge detection filter has also been examined and is seen to still leave an unacceptable quantity of artificial flame-fronts. A novel approach has been developed for image analysis where a combination of a non-linear diffusion filter, Sobel gradient and threshold-based curve elimination routines have been used to extract traces of the flame-front to obtain local curvature distributions. A visual comparison of the effectiveness of flame-front identification is made between the novel approach, the threshold binarisation filter and the Canny-Deriche filter. The novel approach appears to most accurately identify the flame-fronts. Example histograms of the curvature for six flame conditions and of the total image area are presented and are found to have a broader range of local flame curvatures for increasing bulk Reynolds numbers. Significantly positive values of mean curvature and marginally positive values of skewness of the histogram have been measured for one lifted flame case, but this is generally accounted for by the effect of flame brush curvature. The mean local flame-front curvature reduces with increasing axial distance from the burner exit plane for all flame types. These changes are more pronounced in the lifted flames but are marginal for the thermoacoustically oscillating flames. It is concluded that additional fuel mixture fraction and velocimetry studies are required to examine whether processes such as the degree of partial-premixedness close to the burner exit plane, the velocity field and the turbulence field have a strong correlation with the curvature characteristics of the investigated flames.

An experimental investigation of flame behavior during cylindrical vessel explosions

NASA Astrophysics Data System (ADS)

Starke, R.; Roth, P.

1986-12-01

The propagation of premixed flames centrally ignited at one of the end flanges of a closed cylindrical vessel and the flame-induced flow have been investigated. Photographic records show that under specific geometrical conditions the flame exhibits a cone form with a backward directed top, called tulip-shaped. This appears after the flame has lost a main part of its area by side wall quenching. The instantaneous flow velocity during the short explosion process was measured, together with pressure records, with an LDV. An analogy to the experiments of Markstein (1964), is shown, and the explanations of several authors for the 'tulip' formation are given.

Dimpled/grooved face on a fuel injection nozzle body for flame stabilization and related method

DOEpatents

Uhm, Jong Ho; Johnson, Thomas Edward; Kim, Kwanwoo; Zuo, Baifang

2013-08-20

A fuel injection head for a fuel nozzle used in a gas turbine combustor includes a substantially hollow body formed with an upstream end face, a downstream end face and a peripheral wall extending therebetween. A plurality of pre-mix tubes or passages extend axially through the hollow body with inlets at the upstream end face and outlets at the downstream end face. An exterior surface of the downstream end face is formed with three-dimensional surface features that increase a total surface area of the exterior surface as compared to a substantially flat, planar downstream end face.

Preparation of Nanoemulsions by Premix Membrane Emulsification: Which Parameters Have a Significant Influence on the Resulting Particle Size?

PubMed

Gehrmann, Sandra; Bunjes, Heike

2017-08-01

Oil-in-water emulsions with particle sizes smaller than 200 nm are interesting carrier systems for poorly water-soluble drugs. Such emulsions can be produced by premix membrane emulsification. In this study, it was systematically investigated which process and formulation parameters have a strong influence on the resulting quality of a triglyceride emulsion. The influence of the pre-emulsion quality and the emulsifier concentration was examined. Also a design of experiments (DoE) approach was carried out: variables included were emulsifier (poloxamer 188, Tween 80, and sucrose laurate [SL]), flow rate, cycle number, and membrane material (polyester, nylon, cellulose acetate, and aluminum oxide; pore sizes, 200 nm), and responses were d 50 value and span for particle size and distribution width. The quality of the pre-emulsion had no influence on the quality of the nanoemulsion after 5 extrusion cycles. The DoE evaluation indicated that an increase in flow rate was of minor importance, whereas an increase in cycle number had a strong impact on the decrease of particle size. The very hydrophilic alumina membrane in combination with the emulsifier which caused the lowest interfacial tension (SL) was the most suitable combination. However, in general, the favorable emulsifier was membrane dependent. Even smaller particle sizes (∼100 nm) could be achieved by using an alumina membrane with smaller pore sizes (100 nm). Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Study of Unsteady, Sphere-Driven, Shock-Induced Combustion for Application to Hypervelocity Airbreathing Propulsion

NASA Technical Reports Server (NTRS)

Axdahl, Erik; Kumar, Ajay; Wilhite, Alan

2011-01-01

A premixed, shock-induced combustion engine has been proposed in the past as a viable option for operating in the Mach 10 to 15 range in a single stage to orbit vehicle. In this approach, a shock is used to initiate combustion in a premixed fuel/air mixture. Apparent advantages over a conventional scramjet engine include a shorter combustor that, in turn, results in reduced weight and heating loads. There are a number of technical challenges that must be understood and resolved for a practical system: premixing of fuel and air upstream of the combustor without premature combustion, understanding and control of instabilities of the shock-induced combustion front, ability to produce sufficient thrust, and the ability to operate over a range of Mach numbers. This study evaluated the stability of the shock-induced combustion front in a model problem of a sphere traveling in a fuel/air mixture at high Mach numbers. A new, rapid analysis method was developed and applied to study such flows. In this method the axisymmetric, body-centric Navier-Stokes equations were expanded about the stagnation streamline of a sphere using the local similarity hypothesis in order to reduce the axisymmetric equations to a quasi-1D set of equations. These reduced sets of equations were solved in the stagnation region for a number of flow conditions in a premixed, hydrogen/air mixture. Predictions from the quasi-1D analysis showed very similar stable or unstable behavior of the shock-induced combustion front as compared to experimental studies and higher-fidelity computational results. This rapid analysis tool could be used in parametric studies to investigate effects of fuel rich/lean mixtures, non-uniformity in mixing, contaminants in the mixture, and different chemistry models.

Evaluation of the equivalence ratio of the reacting mixture using intensity ratio of chemiluminescence in laminar partially premixed CH{sub 4}-air flames

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

Jeong, Yong Ki; Jeon, Chung Hwan; Chang, Young June

An experimental study was performed to investigate the effects of partially premixing, varying the equivalence ratios from 0.79 to 9.52, on OH*, CH* and C{sub 2}* in laminar partially premixed flames. The signals from the electronically excited states of OH*, CH* and C{sub 2}* were detected through interference filters using a photo multiplier tube, which were processed to the intensity ratios (C{sub 2}*/CH*, C{sub 2}*/OH* and CH*/OH*) to determine a correlation with the local equivalence ratios. Furthermore, the consistency between the results of the tomographic reconstruction; Abel inversion technique, image with CCD (Couple Charged Detector) camera and the local radicalmore » intensity with PMT was investigated. The results demonstrated that (1) the flames at F=<1.36 exhibited classical double flame structure, at F>=4.76, the flames exhibited non-premixed-like flame structure and the intermediate flames at 1.36

pH-sensitive polymer-modified liposome-based immunity-inducing system: Effects of inclusion of cationic lipid and CpG-DNA.

PubMed

Yoshizaki, Yuta; Yuba, Eiji; Sakaguchi, Naoki; Koiwai, Kazunori; Harada, Atsushi; Kono, Kenji

2017-10-01

Efficient vaccine carriers for cancer immunotherapy require two functions: antigen delivery to dendritic cells (DCs) and the activation of DCs, a so-called adjuvant effect. We previously reported antigen delivery system using liposomes modified with pH-sensitive polymers, such as 3-methylglutarylated hyperbranched poly(glycidol) (MGlu-HPG), for the induction of antigen-specific immune responses. We reported that inclusion of cationic lipids to MGlu-HPG-modified liposomes activates DCs and enhances antitumor effects. In this study, CpG-DNA, a ligand to Toll-like receptor 9 (TLR9) expressing in endosomes of DCs, was introduced to MGlu-HPG-modified liposomes containing cationic lipids using two complexation methods (Pre-mix and Post-mix) for additional activation of antigen-specific immunity. For Pre-mix, thin membrane of lipids and polymers were dispersed by a mixture of antigen/CpG-DNA. For Post-mix, CpG-DNA was added to pre-formed liposomes. Both Pre-mix and Post-mix delivered CpG-DNA to DC endosomes, where TLR9 is expressing, more efficiently than free CpG-DNA solution did. These liposomes promoted cytokine production from DCs and the expression of co-stimulatory molecules in vitro and induced antigen-specific immune responses in vivo. Both Pre-mix and Post-mix exhibited strong antitumor effects compared with conventional pH-sensitive polymer-modified liposomes. Results show that inclusion of multiple adjuvant molecules into pH-sensitive polymer-modified liposomes and suitable CpG-DNA complexation methods are important to design potent vaccine carriers. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterization of Reactivity Controlled Compression Ignition (RCCI) Using Premixed Gasoline and Direct-Injected Gasoline with a Cetane Improver on a Multi-Cylinder Engine

DOE PAGES

Dempsey, Adam B.; Curran, Scott; Reitz, Rolf D.

2015-04-14

The focus of the present paper was to characterize Reactivity Controlled Compression Ignition (RCCI) using a single-fuel approach of gasoline and gasoline mixed with a commercially available cetane improver on a multi-cylinder engine. RCCI was achieved by port-injecting a certification grade 96 research octane gasoline and direct-injecting the same gasoline mixed with various levels of a cetane improver, 2-ethylhexyl nitrate (EHN). The EHN volume percentages investigated in the direct-injected fuel were 10, 5, and 2.5%. The combustion phasing controllability and emissions of the different fueling combinations were characterized at 2300 rpm and 4.2 bar brake mean effective pressure over amore » variety of parametric investigations including direct injection timing, premixed gasoline percentage, and intake temperature. Comparisons were made to gasoline/diesel RCCI operation on the same engine platform at nominally the same operating condition. The experiments were conducted on a modern four cylinder light-duty diesel engine that was modified with a port-fuel injection system while maintaining the stock direct injection fuel system. The pistons were modified for highly premixed operation and feature an open shallow bowl design. The results indicate that the authority to control the combustion phasing through the fuel delivery strategy (e.g., direct injection timing or premixed gasoline percentage) is not a strong function of the EHN concentration in the direct-injected fuel. It was also observed that NOx emissions are a strong function of the global EHN concentration in-cylinder and the combustion phasing. Finally, in general, NOx emissions are significantly elevated for gasoline/gasoline+EHN operation compared with gasoline/diesel RCCI operation at a given operating condition.« less

Detailed Studies on Flame Extinction by Inert Particles in Normal- and Micro-gravity

NASA Technical Reports Server (NTRS)

Andac, M. G.; Egolfopoulos, F. N.; Campbell, C. S.

2001-01-01

The combustion of dusty flows has been studied to lesser extent than pure gas phase flows and sprays. Particles can have a strong effect by modifying the dynamic response and detailed structure of flames through the dynamic, thermal, and chemical couplings between the two phases. A rigorous understanding of the dynamics and structure of two-phase flows can be attained in stagnation flow configurations, which have been used by others to study spray combustion as well as reacting dusty flows. In earlier studies on reacting dusty flows, the thermal coupling between the two phases as well as the effect of gravity on the flame response were not considered. However, in Ref. 6, the thermal coupling between chemically inert particles and the gas was addressed in premixed flames. The effects of gravity was also studied showing that it can substantially affect the profiles of the particle velocity, number density, mass flux, and temperature. The results showed a strong dynamic and thermal dependence of reacting dusty flows to particle number density. However, the work was only numerical and limited to twin-flames, stagnation, premixed flames. In Ref. 7 the effects of chemically inert particle clouds on the extinction of strained premixed and non-premixed flames were studied both experimentally and numerically at 1-g. It was shown and explained that large particles can cause more effective flame cooling compared to smaller particles. The effects of flame configuration and particle injection orientation were also addressed. The complexity of the coupling between the various parameters in such flows was demonstrated and it was shown that it was impossible to obtain a simple and still meaningful scaling that captured all the pertinent physics.

Flame thickness and conditional scalar dissipation rate in a premixed temporal turbulent reacting jet

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

Chaudhuri, Swetaprovo; Kolla, Hemanth; Dave, Himanshu L.

The flame structure corresponding to lean hydrogen–air premixed flames in intense sheared turbulence in the thin reaction zone regime is quantified from flame thickness and conditional scalar dissipation rate statistics, obtained from recent direct numerical simulation data of premixed temporally-evolving turbulent slot jet flames. It is found that, on average, these sheared turbulent flames are thinner than their corresponding planar laminar flames. Extensive analysis is performed to identify the reason for this counter-intuitive thinning effect. The factors controlling the flame thickness are analyzed through two different routes i.e., the kinematic route, and the transport and chemical kinetics route. The kinematicmore » route is examined by comparing the statistics of the normal strain rate due to fluid motion with the statistics of the normal strain rate due to varying flame displacement speed or self-propagation. It is found that while the fluid normal straining is positive and tends to separate iso-scalar surfaces, the dominating normal strain rate due to self-propagation is negative and tends to bring the iso-scalar surfaces closer resulting in overall thinning of the flame. The transport and chemical kinetics route is examined by studying the non-unity Lewis number effect on the premixed flames. The effects from the kinematic route are found to couple with the transport and chemical kinetics route. In addition, the intermittency of the conditional scalar dissipation rate is also examined. It is found to exhibit a unique non-monotonicity of the exponent of the stretched exponential function, conventionally used to describe probability density function tails of such variables. As a result, the non-monotonicity is attributed to the detailed chemical structure of hydrogen-air flames in which heat release occurs close to the unburnt reactants at near free-stream temperatures.« less

Flame thickness and conditional scalar dissipation rate in a premixed temporal turbulent reacting jet

DOE PAGES

Chaudhuri, Swetaprovo; Kolla, Hemanth; Dave, Himanshu L.; ...

2017-07-07

The flame structure corresponding to lean hydrogen–air premixed flames in intense sheared turbulence in the thin reaction zone regime is quantified from flame thickness and conditional scalar dissipation rate statistics, obtained from recent direct numerical simulation data of premixed temporally-evolving turbulent slot jet flames. It is found that, on average, these sheared turbulent flames are thinner than their corresponding planar laminar flames. Extensive analysis is performed to identify the reason for this counter-intuitive thinning effect. The factors controlling the flame thickness are analyzed through two different routes i.e., the kinematic route, and the transport and chemical kinetics route. The kinematicmore » route is examined by comparing the statistics of the normal strain rate due to fluid motion with the statistics of the normal strain rate due to varying flame displacement speed or self-propagation. It is found that while the fluid normal straining is positive and tends to separate iso-scalar surfaces, the dominating normal strain rate due to self-propagation is negative and tends to bring the iso-scalar surfaces closer resulting in overall thinning of the flame. The transport and chemical kinetics route is examined by studying the non-unity Lewis number effect on the premixed flames. The effects from the kinematic route are found to couple with the transport and chemical kinetics route. In addition, the intermittency of the conditional scalar dissipation rate is also examined. It is found to exhibit a unique non-monotonicity of the exponent of the stretched exponential function, conventionally used to describe probability density function tails of such variables. As a result, the non-monotonicity is attributed to the detailed chemical structure of hydrogen-air flames in which heat release occurs close to the unburnt reactants at near free-stream temperatures.« less

Studies on nonequilibrium phenomena in supersonic chemically reacting flows

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Chandrasekhar, Rajnish

1993-01-01

This study deals with a systematic investigation of nonequilibrium processes in supersonic combustion. The two-dimensional, elliptic Navier-Stokes equations are used to investigate supersonic flows with nonequilibrium chemistry and thermodynamics, coupled with radiation, for hydrogen-air systems. The explicit, unsplit MacCormack finite-difference scheme is used to advance the governing equations in time, until convergence is achieved. For a basic understanding of the flow physics, premixed flows undergoing finite rate chemical reactions are investigated. Results obtained for specific conditions indicate that the radiative interactions vary substantially, depending on reactions involving HO2 and NO species, and that this can have a noticeable influence on the flowfield. The second part of this study deals with premixed reacting flows under thermal nonequilibrium conditions. Here, the critical problem is coupling of the vibrational relaxation process with the radiative heat transfer. The specific problem considered is a premixed expanding flow in a supersonic nozzle. Results indicate the presence of nonequilibrium conditions in the expansion region of the nozzle. This results in reduction of the radiative interactions in the flowfield. Next, the present study focuses on investigation of non-premixed flows under chemical nonequilibrium conditions. In this case, the main problem is the coupled turbulence-chemistry interaction. The resulting formulation is validated by comparison with experimental data on reacting supersonic coflowing jets. Results indicate that the effect of heat release is to lower the turbulent shear stress and the mean density. The last part of this study proposes a new theoretical formulation for the coupled turbulence-radiation interactions. Results obtained for the coflowing jets experiment indicate that the effect of turbulence is to enhance the radiative interactions.

Cathodes and electrolytes for rechargeable magnesium batteries and methods of manufacture

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

Kumta, Prashant N.; Saha, Partha; Datta, Moni Kanchan

The invention relates to Chevrel-phase materials and methods of preparing these materials utilizing a precursor approach. The Chevrel-phase materials are useful in assembling electrodes, e.g., cathodes, for use in electrochemical cells, such as rechargeable batteries. The Chevrel-phase materials have a general formula of Mo 6Z 8 and the precursors have a general formula of M xMo 6Z 8. The cathode containing the Chevrel-phase material in accordance with the invention can be combined with a magnesium-containing anode and an electrolyte.

--No Title--

Science.gov Websites

Column descriptions ID : Unique integer for each control time simulation LABEL : Description unique to each ID (see paper) Z : Redshift TIMEAREA : Observer-frame control time x area at 'Z' (year-arcmin ^2) Z2 : Second redshift TIMEVOL : Total rest-frame control time x volume between 'Z' and 'Z2' (year

Thrust chamber life prediction. Volume 1: Mechanical and physical properties of high performance rocket nozzle materials

NASA Technical Reports Server (NTRS)

Esposito, J. J.; Zabora, R. F.

1975-01-01

Pertinent mechanical and physical properties of six high conductivity metals were determined. The metals included Amzirc, NARloy Z, oxygen free pure copper, electroformed copper, fine silver, and electroformed nickel. Selection of these materials was based on their possible use in high performance reusable rocket nozzles. The typical room temperature properties determined for each material included tensile ultimate strength, tensile yield strength, elongation, reduction of area, modulus of elasticity, Poisson's ratio, density, specific heat, thermal conductivity, and coefficient of thermal expansion. Typical static tensile stress-strain curves, cyclic stress-strain curves, and low-cycle fatigue life curves are shown. Properties versus temperature are presented in graphical form for temperatures from 27.6K (-410 F) to 810.9K (1000 F).

A Selection of Composites Simulation Practices at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Ratcliffe, James G.

2007-01-01

One of the major areas of study at NASA Langley Research Center is the development of technologies that support the use of advanced composite materials in aerospace applications. Amongst the supporting technologies are analysis tools used to simulate the behavior of these materials. This presentation will discuss a number of examples of analysis tools and simulation practices conducted at NASA Langley. The presentation will include examples of damage tolerance analyses for both interlaminar and intralaminar failure modes. Tools for modeling interlaminar failure modes include fracture mechanics and cohesive methods, whilst tools for modeling intralaminar failure involve the development of various progressive failure analyses. Other examples of analyses developed at NASA Langley include a thermo-mechanical model of an orthotropic material and the simulation of delamination growth in z-pin reinforced laminates.

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

Yang, Jinyi; Wu, Xue-Bing; Wang, Feige

We present initial results from the first systematic survey of luminous z  ∼ 5.5 quasars. Quasars at z ∼ 5.5, the post-reionization epoch, are crucial tools to explore the evolution of intergalactic medium, quasar evolution, and the early super-massive black hole growth. However, it has been very challenging to select quasars at redshifts 5.3 ≤ z ≤ 5.7 using conventional color selections, due to their similar optical colors to late-type stars, especially M dwarfs, resulting in a glaring redshift gap in quasar redshift distributions. We develop a new selection technique for z ∼ 5.5 quasars based on optical, near-IR, and mid-IRmore » photometric data from Sloan Digital Sky Survey (SDSS), UKIRT InfraRed Deep Sky Surveys—Large Area Survey (ULAS), VISTA Hemisphere Survey (VHS), and Wide Field Infrared Survey Explorer . From our pilot observations in the SDSS-ULAS/VHS area, we have discovered 15 new quasars at 5.3 ≤ z ≤ 5.7 and 6 new lower redshift quasars, with SDSS z band magnitude brighter than 20.5. Including other two z ∼ 5.5 quasars already published in our previous work, we now construct a uniform quasar sample at 5.3 ≤ z ≤ 5.7, with 17 quasars in a ∼4800 square degree survey area. For further application in a larger survey area, we apply our selection pipeline to do a test selection by using the new wide field J-band photometric data from a preliminary version of the UKIRT Hemisphere Survey (UHS). We successfully discover the first UHS selected z ∼ 5.5 quasar.« less

Mechanical Property Evaluation at Elevated Temperatures of Sintered Beta Silicon Carbide.

DTIC Science & Technology

1986-03-01

a co mercial- sintered product. 1-7 It is fabricated from a submicron (beta) silicon carbide powder with small additions (f-0.5 wtZ each) of goron and...majority of the material-is beta silicon carbide with a small percentage of the alpha phase and a small amount of graphite. In a parallel study being...surface-connected porosity (Figures 12 and 13). This porosity was often an area of small interconnected porosity and not necessarily a discrete void

High-Throughput and Label-Free Single Nanoparticle Sizing Based on Time-Resolved On-Chip Microscopy

DTIC Science & Technology

2015-02-17

12,13 soot ,6,14 ice crystals in clouds,15 and engineered nano- materials,16 among others. While there exist various nanoparticle detection and sizing...the sample of interest is placed on an optoelectronic sensor -array with typically less than 0.5 mm gap (z2) between the sample and sensor planes such...that, under unit mag- nification, the entire sensor active area serves as the imaging FOV, easily reaching >2030 mm2 with state-of-the-art CMOS

Atomic-Ordering-Induced Quantum Phase Transition between Topological Crystalline Insulator and Z 2 Topological Insulator

NASA Astrophysics Data System (ADS)

Deng, Hui-Xiong; Song, Zhi-Gang; Li, Shu-Shen; Wei, Su-Huai; Luo, Jun-Wei

2018-05-01

Topological phase transition in a single material usually refers to transitions between a trivial band insulator and a topological Dirac phase, but the transition may also occur between different classes of topological Dirac phases. However, it is a fundamental challenge to realize quantum transition between Z2 nontrivial topological insulator (TI) and topological crystalline insulator (TCI) in one material because Z2 TI and TCI are hardly both co-exist in a single material due to their contradictory requirement on the number of band inversions. The Z2 TIs must have an odd number of band inversions over all the time-reversal invariant momenta, whereas, the newly discovered TCIs, as a distinct class of the topological Dirac materials protected by the underlying crystalline symmetry, owns an even number of band inversions. Here, take PbSnTe2 alloy as an example, we show that at proper alloy composition the atomic-ordering is an effective way to tune the symmetry of the alloy so that we can electrically switch between TCI phase and Z2 TI phase when the alloy is ordered from a random phase into a stable CuPt phase. Our results suggest that atomic-ordering provides a new platform to switch between different topological phases.

Effect of different impression materials and techniques on the dimensional accuracy of implant definitive casts.

PubMed

Ebadian, Behnaz; Rismanchian, Mansor; Dastgheib, Badrosadat; Bajoghli, Farshad

2015-01-01

Different factors such as impression techniques and materials can affect the passive fit between the superstructure and implant. The aim of this study was to determine the effect of different impression materials and techniques on the dimensional accuracy of implant definitive casts. Four internal hex implants (Biohorizons Ø4 mm) were placed on a metal maxillary model perpendicular to the horizontal plane in maxillary lateral incisors, right canine and left first premolar areas. Three impression techniques including open tray, closed tray using ball top screw abutments and closed tray using short impression copings and two impression materials (polyether and polyvinyl siloxane) were evaluated (n = 60). The changes in distances between implant analogues in mediolateral (x) and anteroposterior (y) directions and analogue angles in x/z and y/z directions in the horizontal plane on the definitive casts were measured by coordinate measuring machine. The data were analyzed by multivariate two-way analysis of variance and one sample t-test (α = 0.05). No statistical significant differences were observed between different impression techniques and materials. However, deviation and distortion of definitive casts had a significant difference with the master model when short impression copings and polyvinyl siloxane impression material were used (P < 0.05). In open tray technique, there was a significant difference in the rotation of analogs compared with the master model with both impression materials (P < 0.05). There was no difference between open and closed tray impression techniques; however, less distortion and deviation were observed in the open tray technique. In the closed tray impression technique, ball top screw was more accurate than short impression copings.

Electrodes and electrochemical storage cells utilizing tin-modified active materials

DOEpatents

Anani, Anaba; Johnson, John; Lim, Hong S.; Reilly, James; Schwarz, Ricardo; Srinivasan, Supramaniam

1995-01-01

An electrode has a substrate and a finely divided active material on the substrate. The active material is ANi.sub.x-y-z Co.sub.y Sn.sub.z, wherein A is a mischmetal or La.sub.1-w M.sub.w, M is Ce, Nd, or Zr, w is from about 0.05 to about 1.0, x is from about 4.5 to about 5.5, y is from 0 to about 3.0, and z is from about 0.05 to about 0.5. An electrochemical storage cell utilizes such an electrode as the anode. The storage cell further has a cathode, a separator between the cathode and the anode, and an electrolyte.

Turbulent transport measurements in a model of GT-combustor

NASA Astrophysics Data System (ADS)

Chikishev, L. M.; Gobyzov, O. A.; Sharaborin, D. K.; Lobasov, A. S.; Dulin, V. M.; Markovich, D. M.; Tsatiashvili, V. V.

2016-10-01

To reduce NOx formation modern industrial power gas-turbines utilizes lean premixed combustion of natural gas. The uniform distribution of local fuel/air ratio in the combustion chamber plays one of the key roles in the field of lean combustion to prevent thermo-acoustic pulsations. Present paper reports on simultaneous Particle Image Velocimetry and acetone Planar Laser Induced Fluorescence measurements in a cold model of GT-combustor to investigate mixing processes which are relevant to the organization of lean premixed combustion. Velocity and passive admixture pulsations correlations were measured to verify gradient closer model, which is often used in Reynolds-Averaged Navier-Stokes (RANS) simulation of turbulent mixing.

Analysis of Lean Premixed/Prevaporized Combustion with KIVA-2

NASA Technical Reports Server (NTRS)

Deur, J. M.; Kundu, K. P.; Darling, D. D.; Cline, M. C.; Micklow, G. J.; Harper, M. R.; Simons, T. A.

1994-01-01

Requirements to reduce the emissions of pollutants from gas turbines used in aircraft propulsion and ground based power generation have led to consideration of lean premixed/prevaporized (LPP) combustion concept. This paper describes some of the LPP flame tube analyses performed at the NASA Research Center with KIVA-2, a well-known multi-dimensional CFD code for problems including sprays, turbulence, and combustion. Modifications to KIVA-2's boundary condition and chemistry treatments have been made to meet the needs of the present study. The study itself focuses on two key aspects of the LPP concept, low emissions and flame stability (including flashback and lean blowoff.

Understanding Combustion Processes Through Microgravity Research

NASA Technical Reports Server (NTRS)

Ronney, Paul D.

1998-01-01

A review of research on the effects of gravity on combustion processes is presented, with an emphasis on a discussion of the ways in which reduced-gravity experiments and modeling has led to new understanding. Comparison of time scales shows that the removal of buoyancy-induced convection leads to manifestations of other transport mechanisms, notably radiative heat transfer and diffusional processes such as Lewis number effects. Examples from premixed-gas combustion, non-premixed gas-jet flames, droplet combustion, flame spread over solid and liquid fuels, and other fields are presented. Promising directions for new research are outlined, the most important of which is suggested to be radiative reabsorption effects in weakly burning flames.

Investigating the effects of critical phenomena in premixed methane-oxygen flames at cryogenic conditions

NASA Astrophysics Data System (ADS)

Gopal, Abishek; Yellapantula, Shashank; Larsson, Johan

2017-11-01

Methane is increasingly becoming viable as a rocket fuel in the latest generation of launch vehicles. In liquid rocket engines, fuel and oxidizer are injected under cryogenic conditions into the combustion chamber. At high pressures, typical of rocket combustion chambers, the propellants exist in supercritical states where the ideal gas thermodynamics are no longer valid. We investigate the effects of real-gas thermodynamics on transcritical laminar premixed methane-oxygen flames. The effect of the real-gas cubic equations of state and high-pressure transport properties on flame dynamics is presented. We also study real-gas effects on the extinction limits of the methane-oxygen flame.

Emission measurements for a lean premixed propane/air system at pressures up to 30 atmospheres

NASA Technical Reports Server (NTRS)

Roffe, G.; Venkataramani, K. S.

1978-01-01

The emissions of a lean premixed system of propane/air were measured in a flametube apparatus. Tests were conducted at inlet temperatures of 600K and 800K and pressures of 10 atm and 30 atm over a range of equivalence ratios. The data obtained were combined with previous data taken in the same apparatus to correlate nitrogen oxide emissions with operating conditions. Sampling probe design was found to have a pronounced effect on measured CO levels but did not influence measurements. The most effective probe tested was one which combined thermal and pressure quenching of the gas sample.

EXPERIMENTAL AND MODELING STUDY OF PREMIXED LAMINAR FLAMES OF ETHANOL AND METHANE.

PubMed

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

2013-04-18

To better understand the chemistry of the combustion of ethanol, the structure of five low pressure laminar premixed flames has been investigated: a pure methane flame (φ=1), three pure ethanol flames (φ=0.7, 1.0, and 1.3), and an ethanol/methane mixture flames (φ=1). The flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 64.3 cm/s at 333 K. The results consist of mole fraction profiles of 20 species measured as a function of the height above the burner by probe sampling followed by online gas chromatography analyses. A mechanism for the oxidation of ethanol was proposed. The reactions of ethanol and acetaldehyde were updated and include recent theoretical calculations while that of ethenol, dimethyl ether, acetone, and propanal were added in the mechanism. This mechanism was also tested against experimental results available in the literature for laminar burning velocities and laminar premixed flame where ethenol was detected. The main reaction pathways of consumption of ethanol are analyzed. The effect of the branching ratios of reaction C 2 H 5 OH+OH→Products+H 2 O is also discussed.

Experimental analysis of an oblique turbulent flame front propagating in a stratified flow

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

Galizzi, C.; Escudie, D.

2010-12-15

This paper details the experimental study of a turbulent V-shaped flame expanding in a nonhomogeneous premixed flow. Its aim is to characterize the effects of stratification on turbulent flame characteristics. The setup consists of a stationary V-shaped flame stabilized on a rod and expanding freely in a lean premixed methane-air flow. One of the two oblique fronts interacts with a stratified slice, which has an equivalence ratio close to one and a thickness greater than that of the flame front. Several techniques such as PIV and CH{sup *} chemiluminescence are used to investigate the instantaneous fields, while laser Doppler anemometrymore » and thermocouples are combined with a concentration probe to provide information on the mean fields. First, in order to provide a reference, the homogeneous turbulent case is studied. Next, the stratified turbulent premixed flame is investigated. Results show significant modifications of the whole flame and of the velocity field upstream of the flame front. The analysis of the geometric properties of the stratified flame indicates an increase in flame brush thickness, closely related to the local equivalence ratio. (author)« less

Simulating the Impact of Premixed Charge Compression Ignition on Light-Duty Diesel Fuel Economy and Emissions of Particulates and NOx

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

Gao, Zhiming; Daw, C Stuart; Wagner, Robert M

2013-01-01

We utilize the Powertrain Systems Analysis Toolkit (PSAT) combined with transient engine and aftertreatment component models implemented in Matlab/Simulink to simulate the effect of premixed charge compression ignition (PCCI) on the fuel economy and emissions of light-duty diesel-powered conventional and hybrid electric vehicles (HEVs). Our simulated engine is capable of both conventional diesel combustion (CDC) and premixed charge compression ignition (PCCI) over real transient driving cycles. Our simulated aftertreatment train consists of a diesel oxidation catalyst (DOC), lean NOx trap (LNT), and catalyzed diesel particulate filter (DPF). The results demonstrate that, in the simulated conventional vehicle, PCCI can significantly reducemore » fuel consumption and emissions by reducing the need for LNT and DPF regeneration. However, the opportunity for PCCI operation in the simulated HEV is limited because the engine typically experiences higher loads and multiple stop-start transients that are outside the allowable PCCI operating range. Thus developing ways of extending the PCCI operating range combined with improved control strategies for engine and emissions control management will be especially important for realizing the potential benefits of PCCI in HEVs.« less

Importance of atomic oxygen in preheating zone in plasma-assisted combustion of a steady-state premixed burner flame

NASA Astrophysics Data System (ADS)

Zaima, K.; Akashi, H.; Sasaki, K.

2015-09-01

It is widely believed that electron impact processes play essential roles in plasma-assisted combustion. However, the concrete roles of high-energy electrons have not been fully understood yet. In this work, we examined the density of atomic oxygen in a premixed burner flame with the superposition of dielectric barrier discharge (DBD). The density of atomic oxygen in the reaction zone was not affected by the superposition of DBD, indicating that the amount of atomic oxygen produced by combustion reactions was much larger than that produced by electron impact processes. On the other hand, in the preheating zone, we observed high-frequency oscillation of the density of atomic oxygen at the timings of the pulsed current of DBD. The oscillation suggests the rapid consumption of additional atomic oxygen by combustion reactions. A numerical simulation using Chemkin indicates the shortened ignition delay time when adding additional atomic oxygen in the period of low-temperature oxidation. The present results reveals the importance of atomic oxygen, which is produced by the effect of high-energy electrons, in the preheating zone in plasma-assisted combustion of the steady-state premixed burner flame.

Effects of mesh type on a non-premixed model in a flameless combustion simulation

NASA Astrophysics Data System (ADS)

Komonhirun, Seekharin; Yongyingsakthavorn, Pisit; Nontakeaw, Udomkiat

2018-01-01

Flameless combustion is a recently developed combustion system, which provides zero emission product. This phenomenon requires auto-ignition by supplying high-temperature air with low oxygen concentration. The flame is vanished and colorless. Temperature of the flameless combustion is less than that of a conventional case, where NOx reactions can be well suppressed. To design a flameless combustor, the computational fluid dynamics (CFD) is employed. The designed air-and-fuel injection method can be applied with the turbulent and non-premixed models. Due to the fact that nature of turbulent non-premixed combustion is based on molecular randomness, inappropriate mesh type can lead to significant numerical errors. Therefore, this research aims to numerically investigate the effects of mesh type on flameless combustion characteristics, which is a primary step of design process. Different meshes, i.e. tetrahedral, hexagonal are selected. Boundary conditions are 5% of oxygen and 900 K of air-inlet temperature for the flameless combustion, and 21% of oxygen and 300 K of air-inlet temperature for the conventional case. The results are finally presented and discussed in terms of velocity streamlines, and contours of turbulent kinetic energy and viscosity, temperature, and combustion products.

Alcohol industry and government revenue derived from underage drinking by Australian adolescents 2005.

PubMed

Doran, Christopher M; Shakeshaft, Anthony P; Hall, Wayne; Petrie, Dennis

2009-01-01

The purpose of this study was to estimate the revenue gained from consumption of alcohol by adolescents for each beverage type for the year 2005. Secondary analysis of self-reported alcohol use in the 2005 Australian Secondary School Surveys Alcohol and Drug Use. Australia. Over 506,000 adolescents aged between 12 and 17 years (29% of all Australian adolescents) consumed approximately 175.69 million standard drinks in 2005. The total revenue generated by the consumption of these beverages was estimated to be $218 million, of which the government received approximately $107 million or 49% in taxation revenue. Total revenue per underage drinker is estimated at $430.84 with revenue increasing with age. Males tend to spend more on spirits and beer while females spend more on pre-mixed spirits. Females aged 12-15 years spend around $121 per year (or 50% of total expenditure) on pre-mixed spirits compared to females aged 16-17 years old that spend around $257 per year (or 62% of total expenditure) on pre-mixed spirits. The Australian government and the alcohol industry receive substantial financial benefit from the sale of alcoholic beverages to under age drinkers.

Effect of Premixed Fuel Preparation for Partially Premixed Combustion with a Low Octane Gasoline on a Light-Duty Multi-Cylinder Compression Ignition Engine

DOE PAGES

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

2015-05-12

Gasoline compression ignition concepts with the majority of the fuel being introduced early in the cycle are known as partially premixed combustion (PPC). Previous research on single- and multi-cylinder engines has shown that PPC has the potential for high thermal efficiency with low NOx and soot emissions. A variety of fuel injection strategies has been proposed in the literature. These injection strategies aim to create a partially stratified charge to simultaneously reduce NOx and soot emissions while maintaining some level of control over the combustion process through the fuel delivery system. The impact of the direct injection strategy to createmore » a premixed charge of fuel and air has not previously been explored, and its impact on engine efficiency and emissions is not well understood. This paper explores the effect of sweeping the direct injected pilot timing from -91° to -324° ATDC, which is just after the exhaust valve closes for the engine used in this study. During the sweep, the pilot injection consistently contained 65% of the total fuel (based on command duration ratio), and the main injection timing was adjusted slightly to maintain combustion phasing near top dead center. A modern four cylinder, 1.9 L diesel engine with a variable geometry turbocharger, high pressure common rail injection system, wide included angle injectors, and variable swirl actuation was used in this study. The pistons were modified to an open bowl configuration suitable for highly premixed combustion modes. The stock diesel injection system was unmodified, and the gasoline fuel was doped with a lubricity additive to protect the high pressure fuel pump and the injectors. The study was conducted at a fixed speed/load condition of 2000 rpm and 4.0 bar brake mean effective pressure (BMEP). The pilot injection timing sweep was conducted at different intake manifold pressures, swirl levels, and fuel injection GTP-15-1067, Dempsey 2 pressures. The gasoline used in this study has relatively high fuel reactivity with a research octane number of 68. The results of this experimental campaign indicate that the highest brake thermal efficiency and lowest emissions are achieved simultaneously with the earliest pilot injection timings (i.e., during the intake stroke).« less

Land surface temperature as an indicator of the unsaturated zone thickness: A remote sensing approach in the Atacama Desert.

PubMed

Urqueta, Harry; Jódar, Jorge; Herrera, Christian; Wilke, Hans-G; Medina, Agustín; Urrutia, Javier; Custodio, Emilio; Rodríguez, Jazna

2018-01-15

Land surface temperature (LST) seems to be related to the temperature of shallow aquifers and the unsaturated zone thickness (∆Z uz ). That relationship is valid when the study area fulfils certain characteristics: a) there should be no downward moisture fluxes in an unsaturated zone, b) the soil composition in terms of both, the different horizon materials and their corresponding thermal and hydraulic properties, must be as homogeneous and isotropic as possible, c) flat and regular topography, and d) steady state groundwater temperature with a spatially homogeneous temperature distribution. A night time Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image and temperature field measurements are used to test the validity of the relationship between LST and ∆Z uz at the Pampa del Tamarugal, which is located in the Atacama Desert (Chile) and meets the above required conditions. The results indicate that there is a relation between the land surface temperature and the unsaturated zone thickness in the study area. Moreover, the field measurements of soil temperature indicate that shallow aquifers dampen both the daily and the seasonal amplitude of the temperature oscillation generated by the local climate conditions. Despite empirically observing the relationship between the LST and ∆Z uz in the study zone, such a relationship cannot be applied to directly estimate ∆Z uz using temperatures from nighttime thermal satellite images. To this end, it is necessary to consider the soil thermal properties, the soil surface roughness and the unseen water and moisture fluxes (e.g., capillarity and evaporation) that typically occur in the subsurface. Copyright © 2017 Elsevier B.V. All rights reserved.

Cast Stone Formulation At Higher Sodium Concentrations

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

Fox, K. M.; Roberts, K. A.; Edwards, T. B.

2013-09-17

A low temperature waste form known as Cast Stone is being considered to provide supplemental Low Activity Waste (LAW) immobilization capacity for the Hanford site. Formulation of Cast Stone at high sodium concentrations is of interest since a significant reduction in the necessary volume of Cast Stone and subsequent disposal costs could be achieved if an acceptable waste form can be produced with a high sodium molarity salt solution combined with a high water to premix (or dry blend) ratio. The objectives of this study were to evaluate the factors involved with increasing the sodium concentration in Cast Stone, includingmore » production and performance properties and the retention and release of specific components of interest. Three factors were identified for the experimental matrix: the concentration of sodium in the simulated salt solution, the water to premix ratio, and the blast furnace slag portion of the premix. The salt solution simulants used in this study were formulated to represent the overall average waste composition. The cement, blast furnace slag, and fly ash were sourced from a supplier in the Hanford area in order to be representative. The test mixes were prepared in the laboratory and fresh properties were measured. Fresh density increased with increasing sodium molarity and with decreasing water to premix ratio, as expected given the individual densities of these components. Rheology measurements showed that all of the test mixes produced very fluid slurries. The fresh density and rheology data are of potential value in designing a future Cast Stone production facility. Standing water and density gradient testing showed that settling is not of particular concern for the high sodium compositions studied. Heat of hydration measurements may provide some insight into the reactions that occur within the test mixes, which may in turn be related to the properties and performance of the waste form. These measurements showed that increased sodium concentration in the salt solution reduced the time to peak heat flow, and reducing the amount of slag in the premix increased the time to peak heat flow. These observations may help to describe some of the cured properties of the samples, in particular the differences in compressive strength observed after 28 and 90 days of curing. Samples were cured for at least 28 days at ambient temperature in the laboratory prior to cured properties analyses. The low activity waste form for disposal at the Hanford Site is required to have a compressive strength of at least 500 psi. After 28 days of curing, several of the test mixes had mean compressive strengths that were below the 500 psi requirement. Higher sodium concentrations and higher water to premix ratios led to reduced compressive strength. Higher fly ash concentrations decreased the compressive strength after 28 days of curing. This may be explained in that the cementitious phases matured more quickly in the mixes with higher concentrations of slag, as evidenced by the data for the time to peak heat generation. All of the test mixes exhibited higher mean compressive strengths after 90 days of curing, with only one composition having a mean compressive strength of less than 500 psi. Leach indices were determined for the test mixes for contaminants of interest. The leaching performance of the mixes evaluated in this study was not particularly sensitive to the factors used in the experimental design. This may be beneficial in demonstrating that the performance of the waste form is robust with respect to changes in the mix composition. The results of this study demonstrate the potential to achieve significantly higher waste loadings in Cast Stone and other low temperature, cementitious waste forms. Additional work is needed to elucidate the hydration mechanisms occurring in Cast Stone formulated with highly concentrated salt solutions since these reactions are responsible for determining the performance of the cured waste form. The thermal analyses completed in this study provide some preliminary insight, although the limited range of the factors in the test matrix hindered the identification of individual component effects. Future work should involve broader factor ranges to identify the roles played by each of the components in the mix via thermal analyses, analytical microscopy, and characterization of phase formation.« less

Cast Stone Formulation At Higher Sodium Concentrations

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

Fox, K. M.; Edwards, T. A.; Roberts, K. B.

2013-10-02

A low temperature waste form known as Cast Stone is being considered to provide supplemental Low Activity Waste (LAW) immobilization capacity for the Hanford site. Formulation of Cast Stone at high sodium concentrations is of interest since a significant reduction in the necessary volume of Cast Stone and subsequent disposal costs could be achieved if an acceptable waste form can be produced with a high sodium molarity salt solution combined with a high water to premix (or dry blend) ratio. The objectives of this study were to evaluate the factors involved with increasing the sodium concentration in Cast Stone, includingmore » production and performance properties and the retention and release of specific components of interest. Three factors were identified for the experimental matrix: the concentration of sodium in the simulated salt solution, the water to premix ratio, and the blast furnace slag portion of the premix. The salt solution simulants used in this study were formulated to represent the overall average waste composition. The cement, blast furnace slag, and fly ash were sourced from a supplier in the Hanford area in order to be representative. The test mixes were prepared in the laboratory and fresh properties were measured. Fresh density increased with increasing sodium molarity and with decreasing water to premix ratio, as expected given the individual densities of these components. Rheology measurements showed that all of the test mixes produced very fluid slurries. The fresh density and rheology data are of potential value in designing a future Cast Stone production facility. Standing water and density gradient testing showed that settling is not of particular concern for the high sodium compositions studied. Heat of hydration measurements may provide some insight into the reactions that occur within the test mixes, which may in turn be related to the properties and performance of the waste form. These measurements showed that increased sodium concentration in the salt solution reduced the time to peak heat flow, and reducing the amount of slag in the premix increased the time to peak heat flow. These observations may help to describe some of the cured properties of the samples, in particular the differences in compressive strength observed after 28 and 90 days of curing. Samples were cured for at least 28 days at ambient temperature in the laboratory prior to cured properties analyses. The low activity waste form for disposal at the Hanford Site is required to have a compressive strength of at least 500 psi. After 28 days of curing, several of the test mixes had mean compressive strengths that were below the 500 psi requirement. Higher sodium concentrations and higher water to premix ratios led to reduced compressive strength. Higher fly ash concentrations decreased the compressive strength after 28 days of curing. This may be explained in that the cementitious phases matured more quickly in the mixes with higher concentrations of slag, as evidenced by the data for the time to peak heat generation. All of the test mixes exhibited higher mean compressive strengths after 90 days of curing, with only one composition having a mean compressive strength of less than 500 psi. Leach indices were determined for the test mixes for contaminants of interest. The leaching performance of the mixes evaluated in this study was not particularly sensitive to the factors used in the experimental design. This may be beneficial in demonstrating that the performance of the waste form is robust with respect to changes in the mix composition. The results of this study demonstrate the potential to achieve significantly higher waste loadings in Cast Stone and other low temperature, cementitious waste forms. Additional work is needed to elucidate the hydration mechanisms occurring in Cast Stone formulated with highly concentrated salt solutions since these reactions are responsible for determining the performance of the cured waste form. The thermal analyses completed in this study provide some preliminary insight, although the limited range of the factors in the test matrix hindered the identification of individual component effects. Future work should involve broader factor ranges to identify the roles played by each of the components in the mix via thermal analyses, analytical microscopy, and characterization of phase formation.« less

Cast Stone Formulation At Higher Sodium Concentrations

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

Fox, K. M.; Roberts, K. A.; Edwards, T. B.

2014-02-28

A low temperature waste form known as Cast Stone is being considered to provide supplemental Low Activity Waste (LAW) immobilization capacity for the Hanford site. Formulation of Cast Stone at high sodium concentrations is of interest since a significant reduction in the necessary volume of Cast Stone and subsequent disposal costs could be achieved if an acceptable waste form can be produced with a high sodium molarity salt solution combined with a high water to premix (or dry blend) ratio. The objectives of this study were to evaluate the factors involved with increasing the sodium concentration in Cast Stone, includingmore » production and performance properties and the retention and release of specific components of interest. Three factors were identified for the experimental matrix: the concentration of sodium in the simulated salt solution, the water to premix ratio, and the blast furnace slag portion of the premix. The salt solution simulants used in this study were formulated to represent the overall average waste composition. The cement, blast furnace slag, and fly ash were sourced from a supplier in the Hanford area in order to be representative. The test mixes were prepared in the laboratory and fresh properties were measured. Fresh density increased with increasing sodium molarity and with decreasing water to premix ratio, as expected given the individual densities of these components. Rheology measurements showed that all of the test mixes produced very fluid slurries. The fresh density and rheology data are of potential value in designing a future Cast Stone production facility. Standing water and density gradient testing showed that settling is not of particular concern for the high sodium compositions studied. Heat of hydration measurements may provide some insight into the reactions that occur within the test mixes, which may in turn be related to the properties and performance of the waste form. These measurements showed that increased sodium concentration in the salt solution reduced the time to peak heat flow, and reducing the amount of slag in the premix increased the time to peak heat flow. These observations may help to describe some of the cured properties of the samples, in particular the differences in compressive strength observed after 28 and 90 days of curing. Samples were cured for at least 28 days at ambient temperature in the laboratory prior to cured properties analyses. The low activity waste form for disposal at the Hanford Site is required to have a compressive strength of at least 500 psi. After 28 days of curing, several of the test mixes had mean compressive strengths that were below the 500 psi requirement. Higher sodium concentrations and higher water to premix ratios led to reduced compressive strength. Higher fly ash concentrations decreased the compressive strength after 28 days of curing. This may be explained in that the cementitious phases matured more quickly in the mixes with higher concentrations of slag, as evidenced by the data for the time to peak heat generation. All of the test mixes exhibited higher mean compressive strengths after 90 days of curing, with only one composition having a mean compressive strength of less than 500 psi. Leachability indices were determined for the test mixes for contaminants of interest. The leaching performance of the mixes evaluated in this study was not particularly sensitive to the factors used in the experimental design. This may be beneficial in demonstrating that the performance of the waste form is robust with respect to changes in the mix composition. The results of this study demonstrate the potential to achieve significantly higher waste loadings in Cast Stone and other low temperature, cementitious waste forms. Additional work is needed to elucidate the hydration mechanisms occurring in Cast Stone formulated with highly concentrated salt solutions since these reactions are responsible for determining the performance of the cured waste form. The thermal analyses completed in this study provide some preliminary insight, although the limited range of the factors in the test matrix hindered the identification of individual component effects. Future work should involve broader factor ranges to identify the roles played by each of the components in the mix via thermal analyses, analytical microscopy, and characterization of phase formation.« less

Structural and mechanical properties of evaporated pure and mixed MgF2-BaF2 thin films

NASA Astrophysics Data System (ADS)

Thielsch, Roland; Pommies, Matthieu; Heber, Joerg; Kaiser, Norbert; Ullmann, Jens

1999-09-01

To grow dense and hard MgF2 films substrate temperatures of about 300 degrees C are required, which unfortunately leads to high tensile film stress and the ability of crack formation. Lowering tensile stress in MgF2 films can be achieved by admixture a second fluoride material of higher cation radius than Mg2+. While former investigation were performed with non-heated films the purpose of the present work was to verify the behavior of mixed films when deposited at elevated substrate temperatures. One of the promising add material is BaF2 which enables evaporation of appropriate pre-mixed materials from a single source. The BaF2 content in the mixed films was varied from 3 to 55 mol percent in the MgF2 host. Optical, mechanical, and structural properties of samples deposited at different substrate temperatures have been studied by spectral photometry, IR spectroscopy, ex situ measurement of mechanical stress, x-ray diffraction, and -reflectometry, RBS, as well as investigation of surface morphology.

Masked-backlighter technique used to simultaneously image x-ray absorption and x-ray emission from an inertial confinement fusion plasma.

PubMed

Marshall, F J; Radha, P B

2014-11-01

A method to simultaneously image both the absorption and the self-emission of an imploding inertial confinement fusion plasma has been demonstrated on the OMEGA Laser System. The technique involves the use of a high-Z backlighter, half of which is covered with a low-Z material, and a high-speed x-ray framing camera aligned to capture images backlit by this masked backlighter. Two strips of the four-strip framing camera record images backlit by the high-Z portion of the backlighter, while the other two strips record images aligned with the low-Z portion of the backlighter. The emission from the low-Z material is effectively eliminated by a high-Z filter positioned in front of the framing camera, limiting the detected backlighter emission to that of the principal emission line of the high-Z material. As a result, half of the images are of self-emission from the plasma and the other half are of self-emission plus the backlighter. The advantage of this technique is that the self-emission simultaneous with backlighter absorption is independently measured from a nearby direction. The absorption occurs only in the high-Z backlit frames and is either spatially separated from the emission or the self-emission is suppressed by filtering, or by using a backlighter much brighter than the self-emission, or by subtraction. The masked-backlighter technique has been used on the OMEGA Laser System to simultaneously measure the emission profiles and the absorption profiles of polar-driven implosions.

Development and validation of a habitat suitability model for ...

EPA Pesticide Factsheets

We developed a spatially-explicit, flexible 3-parameter habitat suitability model that can be used to identify and predict areas at higher risk for non-native dwarf eelgrass (Zostera japonica) invasion. The model uses simple environmental parameters (depth, nearshore slope, and salinity) to quantitatively describe habitat suitable for Z. japonica invasion based on ecology and physiology from the primary literature. Habitat suitability is defined with values ranging from zero to one, where one denotes areas most conducive to Z. japonica and zero denotes areas not likely to support Z. japonica growth. The model was applied to Yaquina Bay, Oregon, USA, an area that has well documented Z. japonica expansion over the last two decades. The highest suitability values for Z. japonica occurred in the mid to upper portions of the intertidal zone, with larger expanses occurring in the lower estuary. While the upper estuary did contain suitable habitat, most areas were not as large as in the lower estuary, due to inappropriate depth, a steeply sloping intertidal zone, and lower salinity. The lowest suitability values occurred below the lower intertidal zone, within the Yaquina River channel. The model was validated by comparison to a multi-year time series of Z. japonica maps, revealing a strong predictive capacity. Sensitivity analysis performed to evaluate the contribution of each parameter to the model prediction revealed that depth was the most important factor. Sh

Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: comparison of beam pitch and detector coverage with 128-detector row CT.

PubMed

Shirasaka, Takashi; Funama, Yoshinori; Hayashi, Mutsukazu; Awamoto, Shinichi; Kondo, Masatoshi; Nakamura, Yasuhiko; Hatakenaka, Masamitsu; Honda, Hiroshi

2012-01-01

Our purpose in this study was to assess the radiation dose reduction and the actual exposed scan length of over-range areas using a spiral dynamic z-collimator at different beam pitches and detector coverage. Using glass rod dosimeters, we measured the unilateral over-range scan dose between the beginning of the planned scan range and the beginning of the actual exposed scan range. Scanning was performed at detector coverage of 80.0 and 40.0 mm, with and without the spiral dynamic z-collimator. The dose-saving ratio was calculated as the ratio of the unnecessary over-range dose, with and without the spiral dynamic z-collimator. In 80.0 mm detector coverage without the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 108, 120, and 126 mm, corresponding to a beam pitch of 0.60, 0.80, and 0.99, respectively. With the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 48, 66, and 84 mm with a beam pitch of 0.60, 0.80, and 0.99, respectively. The dose-saving ratios with and without the spiral dynamic z-collimator for a beam pitch of 0.60, 0.80, and 0.99 were 35.07, 24.76, and 13.51%, respectively. With 40.0 mm detector coverage, the dose-saving ratios with and without the spiral dynamic z-collimator had the highest value of 27.23% with a low beam pitch of 0.60. The spiral dynamic z-collimator is important for a reduction in the unnecessary over-range dose and makes it possible to reduce the unnecessary dose by means of a lower beam pitch.

Barochemistry: Predictive Solid State Chemistry

NASA Astrophysics Data System (ADS)

Yoo, Choong-Shik

The application of compression energy comparable to that of chemical bonds, but substantially greater than those of defects and grain boundaries in solids allows us to pursue novel concepts of high-pressure chemistry (or barochemistry) in materials development by design. At such extreme pressures, simple molecular solids covert into densely packed extended network structures that can be predicted from first principles. In recent years, a significant number of new materials and novel extended structures have been designed and discovered in highly compressed states of the first- and second- row elemental solids, including Li, C, H2,N2, O2, CO, CO2, and H2O. These extended solids are extremely hard, have high energy density, and exhibit novel electronic and nonlinear optical properties that are superior to other known materials at ambient conditions. However, these materials are often formed at formidable pressures and are highly metastable at ambient conditions; only a few systems have been recovered, limiting the materials within a realm of fundamental scientific discoveries. Therefore, an exciting new research area has emerged on the barochemistry to understand and, ultimately, control the stability, bonding, structure, and properties of low Z extended solids. In this paper, we will present our recent research to develop hybrid low Z extended solids amenable to scale up synthesis and ambient stabilization, utilizing kinetically controlled processes in dense solid mixtures and discuss the governing fundamental principles of barochemistry. This work was performed in support of the NSF (DMR-1203834), DTRA (HDTRA1-12-01-0020), and DARPA (W31P4Q-12-1-0009).

Evaluation of flamelet/progress variable model for laminar pulverized coal combustion

NASA Astrophysics Data System (ADS)

Wen, Xu; Wang, Haiou; Luo, Yujuan; Luo, Kun; Fan, Jianren

2017-08-01

In the present work, the flamelet/progress variable (FPV) approach based on two mixture fractions is formulated for pulverized coal combustion and then evaluated in laminar counterflow coal flames under different operating conditions through both a priori and a posteriori analyses. Two mixture fractions, Zvol and Zchar, are defined to characterize the mixing between the oxidizer and the volatile matter/char reaction products. A coordinate transformation is conducted to map the flamelet solutions from a unit triangle space (Zvol, Zchar) to a unit square space (Z, X) so that a more stable solution can be achieved. To consider the heat transfers between the coal particle phase and the gas phase, the total enthalpy is introduced as an additional manifold. As a result, the thermo-chemical quantities are parameterized as a function of the mixture fraction Z, the mixing parameter X, the normalized total enthalpy Hnorm, and the reaction progress variable YPV. The validity of the flamelet chemtable and the selected trajectory variables is first evaluated in a priori tests by comparing the tabulated quantities with the results obtained from numerical simulations with detailed chemistry. The comparisons show that the major species mass fractions can be predicted by the FPV approach in all combustion regions for all operating conditions, while the CO and H2 mass fractions are over-predicted in the premixed flame reaction zone. The a posteriori study shows that overall good agreement between the FPV results and those obtained from detailed chemistry simulations can be achieved, although the coal particle ignition is predicted to be slightly earlier. Overall, the validity of the FPV approach for laminar pulverized coal combustion is confirmed and its performance in turbulent pulverized coal combustion will be tested in future work.

New monoaromatic steroids in organic matter of the apocatagenesis zone

NASA Astrophysics Data System (ADS)

Kashirtsev, V. A.; Fomin, A. N.; Shevchenko, N. P.; Dolzhenko, K. V.

2016-08-01

According to the materials of geochemical study in the core of the ultradeep hole SV-27 of aromatic fractions of bitumoids of the Vilyui syneclise (East Siberia) by the method of chromatography-mass spectrometry, starting from the depth of >5000 m, four diastereomers of previously unknown hydrocarbons, which become predominant in the fraction at a depth of ˜6500 m, were distinguished. Similar hydrocarbons were found in organic matter of Upper Paleozoic rocks of the Kharaulakh anticlinorium in the Verkhoyansk folded area. According to the intense molecular ion m/z 366 and the character of the basic fragmental ions (m/z 238, 309, and 323), the major structure of the compounds studied was determined as 17-desmethyl-23-methylmonoaromatic steroid C27. The absence of such steroids in oil of the Vilyui syneclise shows that deep micro-oils did not participate in the formation of oil fringes of gas condensate deposits of the region.

Multi-component hydrogen storage material

DOEpatents

Faheem, Syed A.; Lewis, Gregory J.; Sachtler, J.W. Adriaan; Low, John J.; Lesch, David A.; Dosek, Paul M.; Wolverton, Christopher M.; Siegel, Donald J.; Sudik, Andrea C.; Yang, Jun

2010-09-07

A reversible hydrogen storage composition having an empirical formula of: Li.sub.(x+z)N.sub.xMg.sub.yB.sub.zH.sub.w where 0.4.ltoreq.x.ltoreq.0.8; 0.2.ltoreq.y.ltoreq.0.6; 0

Thermal-stability studies of electrode materials for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Jiang, Junwei

2005-07-01

The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes will increase the energy density of lithium-ion cells meaning even an 18650-size cell may face safety concerns. This thesis presents studies of the thermal stability of electrode materials in electrolytes to understand their reactivity. A search for new positive electrode materials with high thermal stability was made. The thermal stability of two common electrode materials (Li0.81 C6 and Li0.5CoO2) in lithium-ion cells was studied by Accelerating Rate Calorimeter (ARC). Li0.81C 6 has much lower reactivity with lithium bis(oxalato)borate (LiBOB) electrolyte compared to LiPF6 electrolyte. It is not the case, however, for Li0.5CoO2. Oven tests of full LiCoO 2/C 18650-size cells with LiBOB or LiPF6 electrolytes, confirmed the ARC results. ARC was then used to study the reactivity of existing electrode materials. The thermal stability of a negative electrode material was found to increase with the binding energy of Li atoms hosted in the material. Li0.5VO 2 (B) has a higher lithium binding energy (2.45 eV vs. Li) than Li 0.81C6 (0.1 eV vs. Li) and Li7Ti5O 12 (1.55 eV) and it shows the highest thermal stability in EC/DEC among the three materials. The reactivity of two existing positive electrode materials, LiMn2O4 and LiFePO4, was studied. Cell systems expected to be highly tolerant to thermal abuse were suggested: LiFePO 4/C or Li4Ti5O12 in LiBOB electrolytes. The system, x Li[Ni1/2Mn1/2]O2 • y LiCoO2 • z Li[Li1/3Mn2/3]O2 (x + y + z = 1), was explored for new positive electrode materials with large capacity and high thermal stability. Li[(Ni0.5Mn0.5) xCo1-x]O2 (0.4 ≤ x ≤ 0.7) samples have excellent electrochemical properties and thermal stability and are being commercialized by industry. Li[(Ni0.5Mn0.5)xCo y(Li1/3Mn2/3)z]O2 (1/12 ≤ y ≤ 1/4, 1/6 ≤ z ≤ 1/3) samples have high specific capacity (200 mA h g-1), excellent cycling performance, and are safer than LiCoO2. The materials are suggested for energy cells used in cell phones, laptops, and so on.

Optical polarizer material

DOEpatents

Ebbers, C.A.

1999-08-31

Several crystals have been identified which can be grown using standard single crystals growth techniques and which have a high birefringence. The identified crystals include Li.sub.2 CO.sub.3, LiNaCO.sub.3, LiKCO.sub.3, LiRbCO.sub.3 and LiCsCO.sub.3. The condition of high birefringence leads to their application as optical polarizer materials. In one embodiment of the invention, the crystal has the chemical formula LiK.sub.(1-w-x-y) Na.sub.(1-w-x-z) Rb.sub.(1-w-y-z) Cs.sub.(1-x-y-z) CO.sub.3, where w+x+y+z=1. In another embodiment, the crystalline material may be selected from a an alkali metal carbonate and a double salt of alkali metal carbonates, where the polarizer has a Wollaston configuration, a Glan-Thompson configuration or a Glan-Taylor configuration. A method of making an LiNaCO.sub.3 optical polarizer is described. A similar method is shown for making an LiKCO.sub.3 optical polarizer.

Complicated spastic paraplegia in patients with AP5Z1 mutations (SPG48)

PubMed Central

Hirst, Jennifer; Madeo, Marianna; Smets, Katrien; Edgar, James R.; Schols, Ludger; Li, Jun; Yarrow, Anna; Deconinck, Tine; Baets, Jonathan; Van Aken, Elisabeth; De Bleecker, Jan; Datiles, Manuel B.; Roda, Ricardo H.; Liepert, Joachim; Züchner, Stephan; Mariotti, Caterina; De Jonghe, Peter; Blackstone, Craig

2016-01-01

Objective: Biallelic mutations in the AP5Z1 gene encoding the AP-5 ζ subunit have been described in a small number of patients with hereditary spastic paraplegia (HSP) (SPG48); we sought to define genotype–phenotype correlations in patients with homozygous or compound heterozygous sequence variants predicted to be deleterious. Methods: We performed clinical, radiologic, and pathologic studies in 6 patients with biallelic mutations in AP5Z1. Results: In 4 of the 6 patients, there was complete loss of AP-5 ζ protein. Clinical features encompassed not only prominent spastic paraparesis but also sensory and motor neuropathy, ataxia, dystonia, myoclonus, and parkinsonism. Skin fibroblasts from affected patients tested positive for periodic acid Schiff and autofluorescent storage material, while electron microscopic analysis demonstrated lamellar storage material consistent with abnormal storage of lysosomal material. Conclusions: Our findings expand the spectrum of AP5Z1-associated neurodegenerative disorders and point to clinical and pathophysiologic overlap between autosomal recessive forms of HSP and lysosomal storage disorders. PMID:27606357

Optical polarizer material

DOEpatents

Ebbers, Christopher A.

1999-01-01

Several crystals have been identified which can be grown using standard single crystals growth techniques and which have a high birefringence. The identified crystals include Li.sub.2 CO.sub.3, LiNaCO.sub.3, LiKCO.sub.3, LiRbCO.sub.3 and LiCsCO.sub.3. The condition of high birefringence leads to their application as optical polarizer materials. In one embodiment of the invention, the crystal has the chemical formula LiK.sub.(1-w-x-y) Na.sub.(1-w-x-z) Rb.sub.(1-w-y-z) Cs.sub.(1-x-y-z) CO.sub.3, where w+x+y+z=1. In another embodiment, the crystalline material may be selected from a an alkali metal carbonate and a double salt of alkali metal carbonates, where the polarizer has a Wollaston configuration, a Glan-Thompson configuration or a Glan-Taylor configuration. A method of making an LiNaCO.sub.3 optical polarizer is described. A similar method is shown for making an LiKCO.sub.3 optical polarizer.

Flame exposure time on Langmuir probe degradation, ion density, and thermionic emission for flame temperature.

PubMed

Doyle, S J; Salvador, P R; Xu, K G

2017-11-01

The paper examines the effect of exposure time of Langmuir probes in an atmospheric premixed methane-air flame. The effects of probe size and material composition on current measurements were investigated, with molybdenum and tungsten probe tips ranging in diameter from 0.0508 to 0.1651 mm. Repeated prolonged exposures to the flame, with five runs of 60 s, resulted in gradual probe degradations (-6% to -62% area loss) which affected the measurements. Due to long flame exposures, two ion saturation currents were observed, resulting in significantly different ion densities ranging from 1.16 × 10 16 to 2.71 × 10 19 m -3 . The difference between the saturation currents is caused by thermionic emissions from the probe tip. As thermionic emission is temperature dependent, the flame temperature could thus be estimated from the change in current. The flame temperatures calculated from the difference in saturation currents (1734-1887 K) were compared to those from a conventional thermocouple (1580-1908 K). Temperature measurements obtained from tungsten probes placed in rich flames yielded the highest percent error (9.66%-18.70%) due to smaller emission current densities at lower temperatures. The molybdenum probe yielded an accurate temperature value with only 1.29% error. Molybdenum also demonstrated very low probe degradation in comparison to the tungsten probe tips (area reductions of 6% vs. 58%, respectively). The results also show that very little exposure time (<5 s) is needed to obtain a valid ion density measurement and that prolonged flame exposures can yield the flame temperature but also risks damage to the Langmuir probe tip.

Flame surface statistics of constant-pressure turbulent expanding premixed flames

NASA Astrophysics Data System (ADS)

Saha, Abhishek; Chaudhuri, Swetaprovo; Law, Chung K.

2014-04-01

In this paper we investigate the local flame surface statistics of constant-pressure turbulent expanding flames. First the statistics of local length ratio is experimentally determined from high-speed planar Mie scattering images of spherically expanding flames, with the length ratio on the measurement plane, at predefined equiangular sectors, defined as the ratio of the actual flame length to the length of a circular-arc of radius equal to the average radius of the flame. Assuming isotropic distribution of such flame segments we then convolute suitable forms of the length-ratio probability distribution functions (pdfs) to arrive at the corresponding area-ratio pdfs. It is found that both the length ratio and area ratio pdfs are near log-normally distributed and shows self-similar behavior with increasing radius. Near log-normality and rather intermittent behavior of the flame-length ratio suggests similarity with dissipation rate quantities which stimulates multifractal analysis.

The premixed flame in uniform straining flow

NASA Technical Reports Server (NTRS)

Durbin, P. A.

1982-01-01

Characteristics of the premixed flame in uniform straining flow are investigated by the technique of activation-energy asymptotics. An inverse method is used, which avoids some of the restrictions of previous analyses. It is shown that this method recovers known results for adiabatic flames. New results for flames with heat loss are obtained, and it is shown that, in the presence of finite heat loss, straining can extinguish flames. A stability analysis shows that straining can suppress the cellular instability of flames with Lewis number less than unity. Strain can produce instability of flames with Lewis number greater than unity. A comparison shows quite good agreement between theoretical deductions and experimental observations of Ishizuka, Miyasaka & Law (1981).

Flame-Generated Vorticity Production in Premixed Flame-Vortex Interactions

NASA Technical Reports Server (NTRS)

Patnaik, G.; Kailasanath, K.

2003-01-01

In this study, we use detailed time-dependent, multi-dimensional numerical simulations to investigate the relative importance of the processes leading to FGV in flame-vortex interactions in normal gravity and microgravity and to determine if the production of vorticity in flames in gravity is the same as that in zero gravity except for the contribution of the gravity term. The numerical simulations will be performed using the computational model developed at NRL, FLAME3D. FLAME3D is a parallel, multi-dimensional (either two- or three-dimensional) flame model based on FLIC2D, which has been used extensively to study the structure and stability of premixed hydrogen and methane flames.

Quantifying real-gas effects on a laminar n-dodecane - air premixed flame

NASA Astrophysics Data System (ADS)

Gopal, Abishek; Yellapantula, Shashank; Larsson, Johan

2015-11-01

With the increasing demand for higher efficiencies in aircraft gas-turbine engines, there has been a progressive march towards high pressure-ratio cycles. Under these conditions, the aviation fuel, Jet A, is injected into the combustor at supercritical pressures. In this work, we study and quantify the effects of transcriticality on a 1D freely propagating laminar n-dodecane - air premixed flame. The impact of the constitutive state relations arising from the Ideal Gas equation of state(EOS) and Peng-Robinson EOS on flame structure and propagation is presented. The effects of real-gas models of transport properties, such as viscosity on laminar flame speed, are also presented.

A numerical investigation of premixed combustion in wave rotors

NASA Technical Reports Server (NTRS)

Nalim, M. Razi; Paxson, Daniel E.

1996-01-01

Wave rotor cycles which utilize premixed combustion processes within the passages are examined numerically using a one-dimensional CFD-based simulation. Internal-combustion wave rotors are envisioned for use as pressure-gain combustors in gas turbine engines. The simulation methodology is described, including a presentation of the assumed governing equations for the flow and reaction in the channels, the numerical integration method used, and the modeling of external components such as recirculation ducts. A number of cycle simulations are then presented which illustrate both turbulent-deflagration and detonation modes of combustion. Estimates of performance and rotor wall temperatures for the various cycles are made, and the advantages and disadvantages of each are discussed.

Chaotic dynamics in premixed hydrogen/air channel flow combustion

NASA Astrophysics Data System (ADS)

Pizza, Gianmarco; Frouzakis, Christos E.; Mantzaras, John

2012-04-01

The complex oscillatory behaviour observed in fuel-lean premixed hydrogen/air atmospheric pressure flames in an open planar channel with prescribed wall temperature is investigated by means of direct numerical simulations, employing detailed chemistry descriptions and species transport, and nonlinear dynamics analysis. As the inflow velocity is varied, the sequence of transitions includes harmonic single frequency oscillations, intermittency, mixed mode oscillations, and finally a period-doubling cascade leading to chaotic dynamics. The observed modes are described and characterised by means of phase-space portraits and next amplitude maps. It is shown that the interplay of chemistry, transport, and wall-bounded developing flow leads to considerably richer dynamics compared to fuel-lean hydrogen/air continuously stirred tank reactor studies.

Mid-infrared laser absorption tomography for quantitative 2D thermochemistry measurements in premixed jet flames

NASA Astrophysics Data System (ADS)

Wei, Chuyu; Pineda, Daniel I.; Paxton, Laurel; Egolfopoulos, Fokion N.; Spearrin, R. Mitchell

2018-06-01

A tomographic laser absorption spectroscopy technique, utilizing mid-infrared light sources, is presented as a quantitative method to spatially resolve species and temperature profiles in small-diameter reacting flows relevant to combustion systems. Here, tunable quantum and interband cascade lasers are used to spectrally resolve select rovibrational transitions near 4.98 and 4.19 μm to measure CO and {CO2}, respectively, as well as their vibrational temperatures, in piloted premixed jet flames. Signal processing methods are detailed for the reconstruction of axial and radial profiles of thermochemical structure in a canonical ethylene-air jet flame. The method is further demonstrated to quantitatively distinguish between different turbulent flow conditions.

Scale-Invariant Forms of Conservation Equations in Reactive Fields and a Modified Hydro-Thermo-Diffusive Theory of Laminar Flames

NASA Technical Reports Server (NTRS)

Sohrab, Siavash H.; Piltch, Nancy (Technical Monitor)

2000-01-01

A scale-invariant model of statistical mechanics is applied to present invariant forms of mass, energy, linear, and angular momentum conservation equations in reactive fields. The resulting conservation equations at molecular-dynamic scale are solved by the method of large activation energy asymptotics to describe the hydro-thermo-diffusive structure of laminar premixed flames. The predicted temperature and velocity profiles are in agreement with the observations. Also, with realistic physico-chemical properties and chemical-kinetic parameters for a single-step overall combustion of stoichiometric methane-air premixed flame, the laminar flame propagation velocity of 42.1 cm/s is calculated in agreement with the experimental value.

Polymerization shrinkage stresses in different restorative techniques for non-carious cervical lesions.

PubMed

de Oliveira Correia, Ayla Macyelle; Tribst, João Paulo Mendes; de Souza Matos, Felipe; Platt, Jeffrey A; Caneppele, Taciana Marco Ferraz; Borges, Alexandre Luiz Souto

2018-06-20

This study evaluated the effect of different restorative techniques for non-carious cervical lesions (NCCL) on polymerization shrinkage stress of resins using three-dimensional (3D) finite element analysis (FEA). 3D-models of a maxillary premolar with a NCCL restored with different filling techniques (bulk filling and incremental) were generated to be compared by nonlinear FEA. The bulk filling technique was used for groups B (NCCL restored with Filtek™ Bulk Fill) and C (Filtek™ Z350 XT). The incremental technique was subdivided according to mode of application: P (2 parallel increments of the Filtek™ Z350 XT), OI (2 oblique increments of the Filtek™ Z350 XT, with incisal first), OIV (2 oblique increments of the Filtek™ Z350 XT, with incisal first and increments with the same volume), OG (2 oblique increments of the Filtek™ Z350 XT, with gingival first) and OGV (2 oblique increments of the Filtek™ Z350 XT, with gingival first and increments with the same volume), resulting in 7 models. All materials were considered isotropic, elastic and linear. The results were expressed in maximum principal stress (MPS). The tension stress distribution was influenced by the restorative technique. The lowest stress concentration occurred in group B followed by OG, OGV, OI, OIV, P and C; the incisal interface was more affected than the gingival. The restoration of NCCLs with bulk fill composite resulted in lower shrinkage stress in the gingival and incisal areas, followed by incremental techniques with the initial increment placed on the gingival wall. The non-carious cervical lesions (NCCLs) restored with bulk fill composite have a more favorable biomechanical behavior. Copyright © 2018. Published by Elsevier Ltd.

Flooding tolerance in interspecific introgression lines containing chromosome segments from teosinte (Zea nicaraguensis) in maize (Zea mays subsp. mays).

PubMed

Mano, Y; Omori, F

2013-10-01

Nicaraguan teosinte (Zea nicaraguensis), a species found in frequently flooded areas, provides useful germplasm for breeding flooding-tolerant maize (Z. mays subsp. mays). The objective of this study was to select flooding-tolerant lines using a library of introgression lines (ILs), each containing a chromosome segment from Z. nicaraguensis in the maize inbred line Mi29. To produce the ILs, a single F1 plant derived from a cross between maize Mi29 and Z. nicaraguensis was backcrossed to Mi29 three times, self-pollinated four times and genotyped using simple sequence repeat markers. Flooding tolerance was evaluated at the seedling stage under reducing soil conditions. By backcrossing and selfing, a series of 45 ILs were developed covering nearly the entire maize genome. Five flooding-tolerant lines were identified from among the ILs by evaluating leaf injury. Among these, line IL#18, containing a Z. nicaraguensis chromosome segment on the long arm of chromosome 4, showed the greatest tolerance to flooding, suggesting the presence of a major quantitative trait locus (QTL) in that region. The presence of the QTL was verified by examining flooding tolerance in a population segregating for the candidate region of chromosome 4. There was no significant relationship between the capacity to form constitutive aerenchyma and flooding tolerance in the ILs, indicating the presence of other factors related to flooding tolerance under reducing soil conditions. A flooding-tolerant genotype, IL#18, was identified; this genotype should be useful for maize breeding. In addition, because the chromosome segments of Z. nicaraguensis in the ILs cover nearly the entire genome and Z. nicaraguensis possesses several unique traits related to flooding tolerance, the ILs should be valuable material for additional QTL detection and the development of flooding-tolerant maize lines.

Investigation of mixed-host organic light emitting diodes

NASA Astrophysics Data System (ADS)

Yeh Yee, Kee

One of the limiting factors to the OLED stability or lifetime is the charge buildup at the bilayer heterojunction (HJ) between the hole transport layer (HTL) and electron transport layer (ETL). In recent years, this abrupt interface has been moderated by mixing HTL and ETL to form a single mixed-host, light emitting layer. For uniformly mixed-host (UM) OLED, the device lifetime and also the efficiency were improved due to the spatial broadening of the recombination zone. Similar device architectures, such as the step-wise graded mixed-host (SGM-OLED) and the continuously graded mixed-host (CGM-OLED) have also been implemented by a number of researchers. In this work, a premix of hole transport material (HTM) and electron transport material (ETM), namely TPD and Alq, is prepared for one-step thermal evaporation of the mixed-host light emitting layer (EML). Depending on the evaporation rate, the CGM-OLEDs with different concentration profiles of HTM and ETM in the EML are obtained, which are inversely proportional to each other.

Defective secretion of mucilage is the cellular basis for agravitropism in primary roots of Zea mays cv. Ageotropic

NASA Technical Reports Server (NTRS)

Miller, I.; Moore, R.

1990-01-01

Root caps of primary, secondary, and seminal roots of Z. mays cv. Kys secrete large amounts of mucilage and are in close contact with the root all along the root apex. These roots are strongly graviresponsive. Secondary and seminal roots of Z. mays cv. Ageotropic are also strongly graviresponsive. Similarly, their caps secrete mucilage and closely appress the root all along the root apex. However, primary roots of Z. mays cv. Ageotropic are non-responsive to gravity. Their caps secrete negligible amounts of mucilage and contact the root only at the extreme apex of the root along the calyptrogen. These roots become graviresponsive when their tips are coated with mucilage or mucilage-like materials. Peripheral cells of root caps of roots of Z. mays cv. Kys contain many dictyosomes associated with vesicles that migrate to and fuse with the plasmalemma. Root-cap cells of secondary and seminal (i.e. graviresponsive) roots of Z. mays cv. Ageotropic are similar to those of primary roots of Z. mays cv. Kys. However, root-cap cells of primary (i.e. non-graviresponsive) roots of Z. mays cv. Ageotropic have distended dictyosomal cisternae filled with an electron-dense, granular material. Large vesicles full of this material populate the cells and apparently do not fuse with the plasmalemma. Taken together, these results suggest that non-graviresponsiveness of primary roots of Z. mays cv. Ageotropic results from the lack of apoplastic continuity between the root and the periphery of the root cap. This is a result of negligible secretion of mucilage by cells along the edge of the root cap which, in turn, appears to be due to the malfunctioning of dictyosomes in these cells.

Recombinant spider silk genetically functionalized with affinity domains.

PubMed

Jansson, Ronnie; Thatikonda, Naresh; Lindberg, Diana; Rising, Anna; Johansson, Jan; Nygren, Per-Åke; Hedhammar, My

2014-05-12

Functionalization of biocompatible materials for presentation of active protein domains is an area of growing interest. Herein, we describe a strategy for functionalization of recombinant spider silk via gene fusion to affinity domains of broad biotechnological use. Four affinity domains of different origin and structure; the IgG-binding domains Z and C2, the albumin-binding domain ABD, and the biotin-binding domain M4, were all successfully produced as soluble silk fusion proteins under nondenaturing purification conditions. Silk films and fibers produced from the fusion proteins were demonstrated to be chemically and thermally stable. Still, the bioactive domains are concluded to be folded and accessible, since their respective targets could be selectively captured from complex samples, including rabbit serum and human plasma. Interestingly, materials produced from mixtures of two different silk fusion proteins displayed combined binding properties, suggesting that tailor-made materials with desired stoichiometry and surface distributions of several binding domains can be produced. Further, use of the IgG binding ability as a general mean for presentation of desired biomolecules could be demonstrated for a human vascular endothelial growth factor (hVEGF) model system, via a first capture of anti-VEGF IgG to silk containing the Z-domain, followed by incubation with hVEGF. Taken together, this study demonstrates the potential of recombinant silk, genetically functionalized with affinity domains, for construction of biomaterials capable of presentation of almost any desired biomolecule.

Anomalous behavior in the third harmonic generation z response through dispersion induced shape changes and matching χ(3)

NASA Astrophysics Data System (ADS)

Pillai, Rajesh S.; Brakenhoff, G. J.; Müller, M.

2006-09-01

The third harmonic generation (THG) axial response in the vicinity of an interface formed by two isotropic materials of normal dispersion is typically single peaked, with the maximum intensity at the interface position. Here it is shown experimentally that this THG z response may show anomalous behavior—being double peaked with a dip coinciding with the interface position—when the THG contributions from both materials are of similar magnitude. The observed anomalous behavior is explained, using paraxial Gaussian theory, by considering dispersion induced shape changes in the THG z response.

Composite scintillator screen

DOEpatents

Zeman, Herbert D.

1994-01-01

A scintillator screen for an X-ray system includes a substrate of low-Z material and bodies of a high-Z material embedded within the substrate. By preselecting the size of the bodies embedded within the substrate, the spacial separation of the bodies and the thickness of the screen, the sensitivity of the screen to X-rays within a predetermined energy range can be predicted.

Correlation between the thermal performance and the microstructure of the material used in medium and high voltage transformer terminals

NASA Astrophysics Data System (ADS)

Salas, Y. J.; Vera-Monroy, S. P.; Mejia-Camacho, A.; Rivera, W.

2017-12-01

In Colombia, energy companies neglect the distribution that represents the main and most valuable process, presenting shortcomings in prevention and forecasting programs, using contractors who perform corrective maintenance of the components without guaranteeing the quality and performance of the materials. Within the process, the terminals determine the effective connection between the voltage line and the transformer, which have faults that are evidenced by the thermal deterioration of the material. In this work, a diagnosis of the thermal performance of these components was carried out and it was correlated with the microstructure, observing variations of the working temperature, with a thermography camera, for three types of terminals, which were classified by X-ray fluorescence in brass Z20, Z40 and Z60, and for two types of connection, copper and aluminium. The microstructure results showed that copper is the conductor that degrades the terminals faster, evidencing cracking of the material; on the other hand, the Z40 brass was the most stable with the lowest temperature variation regardless of the conductor diameter; however, in all cases the behaviour of higher temperature to lower calibre is satisfied.

Selective perturbation of in vivo linear energy transfer using high- Z vaginal applicators for Cf-252 brachytherapy

NASA Astrophysics Data System (ADS)

Rivard, M. J.; Evans, K. E.; Leal, L. C.; Kirk, B. L.

2004-01-01

Californium-252 ( 252Cf) brachytherapy sources emit both neutrons and photons, and have the potential to vastly improve the current standard-of-practice for brachytherapy. While hydrogenous materials readily attenuate the 252Cf fission energy neutrons, high- Z materials are utilized to attenuate the 252Cf gamma-rays. These differences in shielding materials may be exploited when treating with a vaginal applicator to possibly improve patient survival through perturbation of the in vivo linear energy transfer radiation.

Microwave Photonics

DTIC Science & Technology

2005-11-01

along X & Z The active area of the detector used is about 3 mm in diameter. Figure 54 shows two measured light power coupling curves plotted against...the scanned detector positions along the X & Z axes. At the top of the power curves , there are flat areas. It indicates that the detector collects...is about 400 m long for curve scanning along X direction and is about 500 m long for curve scanning along Z direction. This difference might be

EXPERIMENTAL AND MODELING STUDY OF PREMIXED LAMINAR FLAMES OF ETHANOL AND METHANE

PubMed Central

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

2013-01-01

To better understand the chemistry of the combustion of ethanol, the structure of five low pressure laminar premixed flames has been investigated: a pure methane flame (φ=1), three pure ethanol flames (φ=0.7, 1.0, and 1.3), and an ethanol/methane mixture flames (φ=1). The flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 64.3 cm/s at 333 K. The results consist of mole fraction profiles of 20 species measured as a function of the height above the burner by probe sampling followed by online gas chromatography analyses. A mechanism for the oxidation of ethanol was proposed. The reactions of ethanol and acetaldehyde were updated and include recent theoretical calculations while that of ethenol, dimethyl ether, acetone, and propanal were added in the mechanism. This mechanism was also tested against experimental results available in the literature for laminar burning velocities and laminar premixed flame where ethenol was detected. The main reaction pathways of consumption of ethanol are analyzed. The effect of the branching ratios of reaction C2H5OH+OH→Products+H2O is also discussed. PMID:23712124

Sub-grid scale combustion models for large eddy simulation of unsteady premixed flame propagation around obstacles.

PubMed

Di Sarli, Valeria; Di Benedetto, Almerinda; Russo, Gennaro

2010-08-15

In this work, an assessment of different sub-grid scale (sgs) combustion models proposed for large eddy simulation (LES) of steady turbulent premixed combustion (Colin et al., Phys. Fluids 12 (2000) 1843-1863; Flohr and Pitsch, Proc. CTR Summer Program, 2000, pp. 61-82; Kim and Menon, Combust. Sci. Technol. 160 (2000) 119-150; Charlette et al., Combust. Flame 131 (2002) 159-180; Pitsch and Duchamp de Lageneste, Proc. Combust. Inst. 29 (2002) 2001-2008) was performed to identify the model that best predicts unsteady flame propagation in gas explosions. Numerical results were compared to the experimental data by Patel et al. (Proc. Combust. Inst. 29 (2002) 1849-1854) for premixed deflagrating flame in a vented chamber in the presence of three sequential obstacles. It is found that all sgs combustion models are able to reproduce qualitatively the experiment in terms of step of flame acceleration and deceleration around each obstacle, and shape of the propagating flame. Without adjusting any constants and parameters, the sgs model by Charlette et al. also provides satisfactory quantitative predictions for flame speed and pressure peak. Conversely, the sgs combustion models other than Charlette et al. give correct predictions only after an ad hoc tuning of constants and parameters. Copyright 2010 Elsevier B.V. All rights reserved.

Effects of Karlovitz number on turbulent kinetic energy transport in turbulent lean premixed methane/air flames

NASA Astrophysics Data System (ADS)

Wang, Zhiyan; Abraham, John

2017-08-01

Direct numerical simulations of lean methane/air flames are carried out to study the effects of premixed combustion on turbulence. The equivalence ratio of the flame is 0.5 and non-dimensional turbulence intensities (urms/SL) are between 2 and 25. The mixture pressure is 20 bars and temperature is 810 K to simulate approximate conditions in lean-burn natural gas engines. The Karlovitz number (Ka) varies from 1.1 to 49.4, and the Damköhler number (Da) varies from 0.26 to 3.2 corresponding to turbulent premixed combustion in the thin reaction zone (TRZ) regime. It is found that turbulence kinetic energy (TKE) and its dissipation rate decrease monotonically across the flame brush while the integral length scale increases monotonically for flames in the TRZ regime. The transport equation of TKE is then examined, and the scaling of the terms in the equation is discussed. It is found that the sink term which represents molecular diffusion and viscous dissipation is the dominant term in the TKE balance and it scales with the square of Ka. The relative importance of the other terms with respect to the dissipation term is studied. With increasing Ka, the other terms in the TKE balance become less important compared to the dissipation term.

Simultaneous measurement of 2-dimensional H2O concentration and temperature distribution in premixed methane/air flame using TDLAS-based tomography technology

NASA Astrophysics Data System (ADS)

Wang, Fei; Wu, Qi; Huang, Qunxing; Zhang, Haidan; Yan, Jianhua; Cen, Kefa

2015-07-01

An innovative tomographic method using tunable diode laser absorption spectroscopy (TDLAS) and algebraic reconstruction technique (ART) is presented in this paper for detecting two-dimensional distribution of H2O concentration and temperature in a premixed flame. The collimated laser beam emitted from a low cost diode laser module was delicately split into 24 sub-beams passing through the flame from different angles and the acquired laser absorption signals were used to retrieve flame temperature and H2O concentration simultaneously. The efficiency of the proposed reconstruction system and the effect of measurement noise were numerically evaluated. The temperature and H2O concentration in flat methane/air premixed flames under three different equivalence ratios were experimentally measured and reconstruction results were compared with model calculations. Numerical assessments indicate that the TDLAS tomographic system is capable for temperature and H2O concentration profiles detecting even the noise strength reaches 3% of absorption signal. Experimental results under different combustion conditions are well demonstrated along the vertical direction and the distribution profiles are in good agreement with model calculation. The proposed method exhibits great potential for 2-D or 3-D combustion diagnostics including non-uniform flames.

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

Lu, Tianfeng

The goal of the proposed research is to create computational flame diagnostics (CFLD) that are rigorous numerical algorithms for systematic detection of critical flame features, such as ignition, extinction, and premixed and non-premixed flamelets, and to understand the underlying physicochemical processes controlling limit flame phenomena, flame stabilization, turbulence-chemistry interactions and pollutant emissions etc. The goal has been accomplished through an integrated effort on mechanism reduction, direct numerical simulations (DNS) of flames at engine conditions and a variety of turbulent flames with transport fuels, computational diagnostics, turbulence modeling, and DNS data mining and data reduction. The computational diagnostics are primarily basedmore » on the chemical explosive mode analysis (CEMA) and a recently developed bifurcation analysis using datasets from first-principle simulations of 0-D reactors, 1-D laminar flames, and 2-D and 3-D DNS (collaboration with J.H. Chen and S. Som at Argonne, and C.S. Yoo at UNIST). Non-stiff reduced mechanisms for transportation fuels amenable for 3-D DNS are developed through graph-based methods and timescale analysis. The flame structures, stabilization mechanisms, local ignition and extinction etc., and the rate controlling chemical processes are unambiguously identified through CFLD. CEMA is further employed to segment complex turbulent flames based on the critical flame features, such as premixed reaction fronts, and to enable zone-adaptive turbulent combustion modeling.« less

A study on the coagulation of polycyclic aromatic hydrocarbon clusters to determine their collision efficiency

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

Raj, Abhijeet; Sander, Markus; Janardhanan, Vinod

2010-03-15

This paper presents a theoretical study on the physical interaction between polycyclic aromatic hydrocarbons (PAHs) and their clusters of different sizes in laminar premixed flames. Two models are employed for this study: a detailed PAH growth model, referred to as the kinetic Monte Carlo - aromatic site (KMC-ARS) model [Raj et al., Combust. Flame 156 (2009) 896-913]; and a multivariate PAH population balance model, referred to as the PAH - primary particle (PAH-PP) model. Both the models are solved by kinetic Monte Carlo methods. PAH mass spectra are generated using the PAH-PP model, and compared to the experimentally observed spectramore » for a laminar premixed ethylene flame. The position of the maxima of PAH dimers in the spectra and their concentrations are found to depend strongly on the collision efficiency of PAH coagulation. The variation in the collision efficiency with various flame and PAH parameters is studied to determine the factors on which it may depend. A correlation for the collision efficiency is proposed by comparing the computed and the observed spectra for an ethylene flame. With this correlation, a good agreement between the computed and the observed spectra for a number of laminar premixed ethylene flames is found. (author)« less

Preparation of uniform-sized PELA microspheres with high encapsulation efficiency of antigen by premix membrane emulsification.

PubMed

Wei, Qiang; Wei, Wei; Tian, Rui; Wang, Lian-Yan; Su, Zhi-Guo; Ma, Guang-Hui

2008-07-15

Relatively uniform-sized poly(lactide-co-ethylene glycol) (PELA) microspheres with high encapsulation efficiency were prepared rapidly by a novel method combining emulsion-solvent extraction and premix membrane emulsification. Briefly, preparation of coarse double emulsions was followed by additional premix membrane emulsification, and antigen-loaded microspheres were obtained by further solidification. Under the optimum condition, the particle size was about 1 mum and the coefficient of variation (CV) value was 18.9%. Confocal laser scanning microscope and flow cytometer analysis showed that the inner droplets were small and evenly dispersed and the antigen was loaded uniformly in each microsphere when sonication technique was occupied to prepare primary emulsion. Distribution pattern of PEG segment played important role on the properties of microspheres. Compared with triblock copolymer PLA-PEG-PLA, the diblock copolymer PLA-mPEG yielded a more stable interfacial layer at the interface of oil and water phase, and thus was more suitable to stabilize primary emulsion and protect coalescence of inner droplets and external water phase, resulting in high encapsulation efficiency (90.4%). On the other hand, solidification rate determined the time for coalescence during microspheres fabrication, and thus affected encapsulation efficiency. Taken together, improving the polymer properties and solidification rate are considered as two effective strategies to yield high encapsulation.

Computations of steady-state and transient premixed turbulent flames using pdf methods

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

Hulek, T.; Lindstedt, R.P.

1996-03-01

Premixed propagating turbulent flames are modeled using a one-point, single time, joint velocity-composition probability density function (pdf) closure. The pdf evolution equation is solved using a Monte Carlo method. The unclosed terms in the pdf equation are modeled using a modified version of the binomial Langevin model for scalar mixing of Valino and Dopazo, and the Haworth and Pope (HP) and Lagrangian Speziale-Sarkar-Gatski (LSSG) models for the viscous dissipation of velocity and the fluctuating pressure gradient. The source terms for the presumed one-step chemical reaction are extracted from the rate of fuel consumption in laminar premixed hydrocarbon flames, computed usingmore » a detailed chemical kinetic mechanism. Steady-state and transient solutions are obtained for planar turbulent methane-air and propane-air flames. The transient solution method features a coupling with a Finite Volume (FV) code to obtain the mean pressure field. The results are compared with the burning velocity measurements of Abdel-Gayed et al. and with velocity measurements obtained in freely propagating propane-air flames by Videto and Santavicca. The effects of different upstream turbulence fields, chemical source terms (different fuels and strained/unstrained laminar flames) and the influence of the velocity statistics models (HP and LSSG) are assessed.« less

[Impact to Z-score Mapping of Hyperacute Stroke Images by Computed Tomography in Adaptive Statistical Iterative Reconstruction].

PubMed

Watanabe, Shota; Sakaguchi, Kenta; Hosono, Makoto; Ishii, Kazunari; Murakami, Takamichi; Ichikawa, Katsuhiro

The purpose of this study was to evaluate the effect of a hybrid-type iterative reconstruction method on Z-score mapping of hyperacute stroke in unenhanced computed tomography (CT) images. We used a hybrid-type iterative reconstruction [adaptive statistical iterative reconstruction (ASiR)] implemented in a CT system (Optima CT660 Pro advance, GE Healthcare). With 15 normal brain cases, we reconstructed CT images with a filtered back projection (FBP) and ASiR with a blending factor of 100% (ASiR100%). Two standardized normal brain data were created from normal databases of FBP images (FBP-NDB) and ASiR100% images (ASiR-NDB), and standard deviation (SD) values in basal ganglia were measured. The Z-score mapping was performed for 12 hyperacute stroke cases by using FBP-NDB and ASiR-NDB, and compared Z-score value on hyperacute stroke area and normal area between FBP-NDB and ASiR-NDB. By using ASiR-NDB, the SD value of standardized brain was decreased by 16%. The Z-score value of ASiR-NDB on hyperacute stroke area was significantly higher than FBP-NDB (p<0.05). Therefore, the use of images reconstructed with ASiR100% for Z-score mapping had potential to improve the accuracy of Z-score mapping.

Evaluation of Space Plasma Data: Effects upon Spacecraft Materials and Predictions of Hazardous Conditions; Polar ARCS

DTIC Science & Technology

1990-02-28

or a significant amount of solar -produced ionization is convecting into the region from sunlit areas. The weak nature of the precipitation events and...8 spacecraft was located in the downstream solar wind (SM coordinates: -2 6 RE x, 2 7 RE y, -1.2 RE z). The vector components and total field stength...of the IMF for the 2 hours before and 1 hour after launch are shown in Figure 6. Assuming an average solar wind speed of 400 km/sec, IMF conditions

Proposed pushered single shell capsule design for the investigation of mid/high Z mix on the NIF

NASA Astrophysics Data System (ADS)

Sacks, Ryan; Tipton, Robert; Graziani, Frank

2016-05-01

The CD Mix campaign has given a detailed explination of the mix mechanics in the current ignition capsule designs by investigating the relationship between material mixing, shell-fuel interfaces, and the change in thermonuclear yield given a deuterated layer in the capsule. Alternative ignition scenarios include the use of double shell designs that incorporate high-Z material in the capsule. Simulations are conducted on a proposed capsule platform using the ARES code on a scaled capsule design using a partially reduced glass capsule design. This allows for the inclusion of deuterium on the inner surface of the pusher layer similar to the CD mix experiments. The presence of silicon dioxide allows for the investigation of the influence of higher Z material on the mixing characteristics.

Effects of CO addition on the characteristics of laminar premixed CH{sub 4}/air opposed-jet flames

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

Wu, C.-Y.; Chao, Y.-C.; Chen, C.-P.

2009-02-15

The effects of CO addition on the characteristics of premixed CH{sub 4}/air opposed-jet flames are investigated experimentally and numerically. Experimental measurements and numerical simulations of the flame front position, temperature, and velocity are performed in stoichiometric CH{sub 4}/CO/air opposed-jet flames with various CO contents in the fuel. Thermocouple is used for the determination of flame temperature, velocity measurement is made using particle image velocimetry (PIV), and the flame front position is measured by direct photograph as well as with laser-induced predissociative fluorescence (LIPF) of OH imaging techniques. The laminar burning velocity is calculated using the PREMIX code of Chemkin collectionmore » 3.5. The flame structures of the premixed stoichiometric CH{sub 4}/CO/air opposed-jet flames are simulated using the OPPDIF package with GRI-Mech 3.0 chemical kinetic mechanisms and detailed transport properties. The measured flame front position, temperature, and velocity of the stoichiometric CH{sub 4}/CO/air flames are closely predicted by the numerical calculations. Detailed analysis of the calculated chemical kinetic structures reveals that as the CO content in the fuel is increased from 0% to 80%, CO oxidation (R99) increases significantly and contributes to a significant level of heat-release rate. It is also shown that the laminar burning velocity reaches a maximum value (57.5 cm/s) at the condition of 80% of CO in the fuel. Based on the results of sensitivity analysis, the chemistry of CO consumption shifts to the dry oxidation kinetics when CO content is further increased over 80%. Comparison between the results of computed laminar burning velocity, flame temperature, CO consumption rate, and sensitivity analysis reveals that the effect of CO addition on the laminar burning velocity of the stoichiometric CH{sub 4}/CO/air flames is due mostly to the transition of the dominant chemical kinetic steps. (author)« less

DNS assessment of relation between mean reaction and scalar dissipation rates in the flamelet regime of premixed turbulent combustion

NASA Astrophysics Data System (ADS)

Nikolaevich Lipatnikov, Andrei; Nishiki, Shinnosuke; Hasegawa, Tatsuya

2015-05-01

The linear relation between the mean rate of product creation and the mean scalar dissipation rate, derived in the seminal paper by K.N.C. Bray ['The interaction between turbulence and combustion', Proceedings of the Combustion Institute, Vol. 17 (1979), pp. 223-233], is the cornerstone for models of premixed turbulent combustion that deal with the dissipation rate in order to close the reaction rate. In the present work, this linear relation is straightforwardly validated by analysing data computed earlier in the 3D Direct Numerical Simulation (DNS) of three statistically stationary, 1D, planar turbulent flames associated with the flamelet regime of premixed combustion. Although the linear relation does not hold at the leading and trailing edges of the mean flame brush, such a result is expected within the framework of Bray's theory. However, the present DNS yields substantially larger (smaller) values of an input parameter cm (or K2 = 1/(2cm - 1)), involved by the studied linear relation, when compared to the commonly used value of cm = 0.7 (or K2 = 2.5). To gain further insight into the issue and into the eventual dependence of cm on mixture composition, the DNS data are combined with the results of numerical simulations of stationary, 1D, planar laminar methane-air flames with complex chemistry, with the results being reported in terms of differently defined combustion progress variables c, i.e. the normalised temperature, density, or mole fraction of CH4, O2, CO2 or H2O. Such a study indicates the dependence of cm both on the definition of c and on the equivalence ratio. Nevertheless, K2 and cm can be estimated by processing the results of simulations of counterpart laminar premixed flames. Similar conclusions were also drawn by skipping the DNS data, but invoking a presumed beta probability density function in order to evaluate cm for the differently defined c's and various equivalence ratios.

Three-dimensional direct numerical simulation study of conditioned moments associated with front propagation in turbulent flows

NASA Astrophysics Data System (ADS)

Yu, R.; Lipatnikov, A. N.; Bai, X. S.

2014-08-01

In order to gain further insight into (i) the use of conditioned quantities for characterizing turbulence within a premixed flame brush and (ii) the influence of front propagation on turbulent scalar transport, a 3D Direct Numerical Simulation (DNS) study of an infinitely thin front that self-propagates in statistically stationary, homogeneous, isotropic, forced turbulence was performed by numerically integrating Navier-Stokes and level set equations. While this study was motivated by issues relevant to premixed combustion, the density was assumed to be constant in order (i) to avoid the influence of the front on the flow and, therefore, to know the true turbulence characteristics as reference quantities for assessment of conditioned moments and (ii) to separate the influence of front propagation on turbulent transport from the influence of pressure gradient induced by heat release. Numerical simulations were performed for two turbulence Reynolds numbers (50 and 100) and four ratios (1, 2, 5, and 10) of the rms turbulent velocity to the front speed. Obtained results show that, first, the mean front thickness is decreased when a ratio of the rms turbulent velocity to the front speed is decreased. Second, although the gradient diffusion closure yields the right direction of turbulent scalar flux obtained in the DNS, the diffusion coefficient Dt determined using the DNS data depends on the mean progress variable. Moreover, Dt is decreased when the front speed is increased, thus, indicating that the front propagation affects turbulent scalar transport even in a constant-density case. Third, conditioned moments of the velocity field differ from counterpart mean moments, thus, disputing the use of conditioned velocity moments for characterizing turbulence when modeling premixed turbulent combustion. Fourth, computed conditioned enstrophies are close to the mean enstrophy in all studied cases, thus, suggesting the use of conditioned enstrophy for characterizing turbulence within a premixed flame brush.

Field Effects of Buoyancy on Lean Premixed Turbulent Flames

NASA Technical Reports Server (NTRS)

Cheng, R. K.; Johnson, M. R.; Greenberg, P. S.; Wernet, M. P.

2003-01-01

The study of field effects of buoyancy on premixed turbulent flames is directed towards the advancement of turbulent combustion theory and the development of cleaner combustion technologies. Turbulent combustion is considered the most important unsolved problem in combustion science and laboratory studies of turbulence flame processes are vital to theoretical development. Although buoyancy is dominant in laboratory flames, most combustion models are not yet capable to consider buoyancy effects. This inconsistency has impeded the validation of theories and numerical simulations with experiments. Conversely, the understanding of buoyancy effects is far too limited to help develop buoyant flame models. Our research is also relevant to combustion technology because lean premixed combustion is a proven method to reduce the formation of oxides of nitrogen (NOx). In industrial lean premixed combustion systems, their operating conditions make them susceptible to buoyancy thus affecting heat distribution, emissions, stability, flashback and blowoff. But little knowledge is available to guide combustion engineers as to how to avoid or overcome these problems. Our hypothesis is that through its influence on the mean pressure field, buoyancy has direct and indirect effects on local flame/turbulence interactions. Although buoyancy acts on the hot products in the farfield the effect is also felt in the nearfield region upstream of the flame. These changes also influence the generation and dissipation of turbulent kinetic energy inside the flame brush and throughout the flowfield. Moreover, the plume of an open flame is unstable and the periodic fluctuations make additional contributions to flame front dynamics in the farfield. Therefore, processes such as flame wrinkling, flow acceleration due to heat release and flame- generated vorticity are all affected. Other global flame properties (e.g. flame stabilization limits and flame speed) may all be coupled to buoyancy. This problem poses major challenges to combustion modeling due to its need for a computation domain extending into the farfield and full specifications of upstream, wall and downstream boundary conditions.

DRIVE CYCLE EFFICIENCY AND EMISSIONS ESTIMATES FOR REACTIVITY CONTROLLED COMPRESSION IGNITION IN A MULTI-CYLINDER LIGHT-DUTY DIESEL ENGINE

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

Curran, Scott; Briggs, Thomas E; Cho, Kukwon

2011-01-01

In-cylinder blending of gasoline and diesel to achieve Reactivity Controlled Compression Ignition (RCCI) has been shown to reduce NOx and PM emissions while maintaining or improving brake thermal efficiency as compared to conventional diesel combustion (CDC). The RCCI concept has an advantage over many advanced combustion strategies in that by varying both the percent of premixed gasoline and EGR rate, stable combustion can be extended over more of the light-duty drive cycle load range. Changing the percent premixed gasoline changes the fuel reactivity stratification in the cylinder providing further control of combustion phasing and pressure rise rate than the usemore » of EGR alone. This paper examines the combustion and emissions performance of light-duty diesel engine using direct injected diesel fuel and port injected gasoline to carry out RCCI for steady-state engine conditions which are consistent with a light-duty drive cycle. A GM 1.9L four-cylinder engine with the stock compression ratio of 17.5:1, common rail diesel injection system, high-pressure EGR system and variable geometry turbocharger was modified to allow for port fuel injection with gasoline. Engine-out emissions, engine performance and combustion behavior for RCCI operation is compared against both CDC and a premixed charge compression ignition (PCCI) strategy which relies on high levels of EGR dilution. The effect of percent of premixed gasoline, EGR rate, boost level, intake mixture temperature, combustion phasing and pressure rise rate is investigated for RCCI combustion for the light-duty modal points. Engine-out emissions of NOx and PM were found to be considerably lower for RCCI operation as compared to CDC and PCCI, while HC and CO emissions were higher. Brake thermal efficiency was similar or higher for many of the modal conditions for RCCI operation. The emissions results are used to estimate hot-start FTP-75 emissions levels with RCCI and are compared against CDC and PCCI modes.« less

Stability and retention of micronutrients in fortified rice prepared using different cooking methods.

PubMed

Wieringa, Frank T; Laillou, Arnaud; Guyondet, Christophe; Jallier, Vincent; Moench-Pfanner, Regina; Berger, Jacques

2014-09-01

Fortified rice holds great potential for bringing essential micronutrients to a large part of the world population. However, it is unknown whether differences in cooking methods or in production of rice premix affect the final amount of micronutrient consumed. This paper presents a study that quantified the losses of five different micronutrients (vitamin A, iron, zinc, folic acid, and vitamin B12) in fortified rice that was produced using three different techniques (hot extrusion, cold extrusion, and coating) during cooking and five different cooking methods (absorption method with or without soaking, washing before cooking, cooking in excess water, and frying rice before cooking). Fortified rice premix from six different producers (two for each technique) was mixed with normal rice in a 1:100 ratio. Each sample was prepared in triplicate, using the five different cooking methods, and retention of iron, zinc, vitamin A, vitamin B12, and folic acid was determined. It was found that the overall retention of iron, zinc, vitamin B12, and folic acid was between 75% and 100% and was unaffected by cooking method, while the retention of vitamin A was significantly affected by cooking method, with retention ranging from 0% (excess water) to 80% (soaking), depending on the cooking method and producer of the rice premix. No systematic differences between the different production methods were observed. We conclude that different cooking methods of rice as used in different regions of the world do not lead to a major loss of most micronutrients, with the exception of vitamin A. The factors involved in protecting vitamin A against losses during cooking need to be identified. All production techniques of rice premix yielded similar results, showing that coating is not inferior to extrusion techniques. Standard overages (50%) for vitamin B12 and folic acid are too high. © 2014 New York Academy of Sciences.

Large-eddy simulation of a bluff-body stabilised turbulent premixed flame using the transported flame surface density approach

NASA Astrophysics Data System (ADS)

Lee, Chin Yik; Cant, Stewart

2017-07-01

A premixed propane-air flame stabilised on a triangular bluff body in a model jet-engine afterburner configuration is investigated using large-eddy simulation (LES). The reaction rate source term for turbulent premixed combustion is closed using the transported flame surface density (TFSD) model. In this approach, there is no need to assume local equilibrium between the generation and destruction of subgrid FSD, as commonly done in simple algebraic closure models. Instead, the key processes that create and destroy FSD are accounted for explicitly. This allows the model to capture large-scale unsteady flame propagation in the presence of combustion instabilities, or in situations where the flame encounters progressive wrinkling with time. In this study, comprehensive validation of the numerical method is carried out. For the non-reacting flow, good agreement for both the time-averaged and root-mean-square velocity fields are obtained, and the Karman type vortex shedding behaviour seen in the experiment is well represented. For the reacting flow, two mesh configurations are used to investigate the sensitivity of the LES results to the numerical resolution. Profiles for the velocity and temperature fields exhibit good agreement with the experimental data for both the coarse and dense mesh. This demonstrates the capability of LES coupled with the TFSD approach in representing the highly unsteady premixed combustion observed in this configuration. The instantaneous flow pattern and turbulent flame behaviour are discussed, and the differences between the non-reacting and reacting flow are described through visualisation of vortical structures and their interaction with the flame. Lastly, the generation and destruction of FSD are evaluated by examining the individual terms in the FSD transport equation. Localised regions where straining, curvature and propagation are each dominant are observed, highlighting the importance of non-equilibrium effects of FSD generation and destruction in the model afterburner.

The evolution equation for the flame surface density in turbulent premixed combustion

NASA Technical Reports Server (NTRS)

Trouve, Arnaud

1993-01-01

The mean reaction rate in flamelet models for turbulent premixed combustion depends on two basic quantities: a mean chemical rate, called the flamelet speed, and the flame surface density. Our previous work had been primarily focused on the problem of the structure and topology of turbulent premixed flames, and it was then determined that the flamelet speed, when space-averaged, is only weakly sensitive to the turbulent flow field. Consequently, the flame surface density is the key quantity that conveys most of the effects of the turbulence on the rate of energy release. In flamelet models, this quantity is obtained via a modeled transport equation called the Sigma-equation. Past theoretical work has produced a rigorous approach that leads to an exact but unclosed formulation for the turbulent Sigma-equation. In the exact Sigma-equation, it appears that the dynamical properties of the flame surface density are determined by a single parameter, namely the turbulent flame stretch. Unfortunately, the turbulent flame stretch as well as the flame surface density is not available from experiments, and, in the absence of experimental data, little is known on the validity of the closure assumptions used in current flamelet models. Direct Numerical Simulation (DNS) is the alternative approach to get basic information on these fundamental quantities. In the present work, three-dimensional DNS of premixed flames in isotropic turbulent flow is used to estimate the different terms appearing in the Sigma-equation. A new methodology is proposed to provide the source and sink terms for the flame surface density, resolved both temporally and spatially throughout the turbulent flame brush. Using this methodology, our objective is to extract the turbulent flame stretch from the DNS data base and then perform extensive comparisons with flamelet models. Thanks to the detailed information produced by the DNS-based analysis, it is expected that this type of comparison will not only underscore the shortcomings of current models, but also suggest ways to improve them.

Z2Pack: Numerical implementation of hybrid Wannier centers for identifying topological materials

NASA Astrophysics Data System (ADS)

Gresch, Dominik; Autès, Gabriel; Yazyev, Oleg V.; Troyer, Matthias; Vanderbilt, David; Bernevig, B. Andrei; Soluyanov, Alexey A.

2017-02-01

The intense theoretical and experimental interest in topological insulators and semimetals has established band structure topology as a fundamental material property. Consequently, identifying band topologies has become an important, but often challenging, problem, with no exhaustive solution at the present time. In this work we compile a series of techniques, some previously known, that allow for a solution to this problem for a large set of the possible band topologies. The method is based on tracking hybrid Wannier charge centers computed for relevant Bloch states, and it works at all levels of materials modeling: continuous k .p models, tight-binding models, and ab initio calculations. We apply the method to compute and identify Chern, Z2, and crystalline topological insulators, as well as topological semimetal phases, using real material examples. Moreover, we provide a numerical implementation of this technique (the Z2Pack software package) that is ideally suited for high-throughput screening of materials databases for compounds with nontrivial topologies. We expect that our work will allow researchers to (a) identify topological materials optimal for experimental probes, (b) classify existing compounds, and (c) reveal materials that host novel, not yet described, topological states.

Shields-1, A SmallSat Radiation Shielding Technology Demonstration

NASA Technical Reports Server (NTRS)

Thomsen, D. Laurence, III; Kim, Wousik; Cutler, James W.

2015-01-01

The NASA Langley Research Center Shields CubeSat initiative is to develop a configurable platform that would allow lower cost access to Space for materials durability experiments, and to foster a pathway for both emerging and commercial-off-the-shelf (COTS) radiation shielding technologies to gain spaceflight heritage in a relevant environment. The Shields-1 will be Langleys' first CubeSat platform to carry out this mission. Radiation shielding tests on Shields-1 are planned for the expected severe radiation environment in a geotransfer orbit (GTO), where advertised commercial rideshare opportunities and CubeSat missions exist, such as Exploration Mission 1 (EM-1). To meet this objective, atomic number (Z) graded radiation shields (Zshields) have been developed. The Z-shield properties have been estimated, using the Space Environment Information System (SPENVIS) radiation shielding computational modeling, to have 30% increased shielding effectiveness of electrons, at half the thickness of a corresponding single layer of aluminum. The Shields-1 research payload will be made with the Z-graded radiation shields of varying thicknesses to create dose-depth curves to be compared with baseline materials. Additionally, Shields-1 demonstrates an engineered Z-grade radiation shielding vault protecting the systems' electronic boards. The radiation shielding materials' performances will be characterized using total ionizing dose sensors. Completion of these experiments is expected to raise the technology readiness levels (TRLs) of the tested atomic number (Z) graded materials. The most significant contribution of the Z-shields for the SmallSat community will be that it enables cost effective shielding for small satellite systems, with significant volume constraints, while increasing the operational lifetime of ionizing radiation sensitive components. These results are anticipated to increase the development of CubeSat hardware design for increased mission lifetimes, and enable out of low earth orbit (LEO) missions by using these tested material concepts as shielding for sensitive components and new spaceflight hardware

Computer simulations and models for the performance characteristics of spectrally equivalent X-ray beams in medical diagnostic radiology

PubMed Central

Okunade, Akintunde A.

2007-01-01

In order to achieve uniformity in radiological imaging, it is recommended that the concept of equivalence in shape (quality) and size (quantity) of clinical Xray beams should be used for carrying out the comparative evaluation of image and patient dose. When used under the same irradiation geometry, X-ray beams that are strictly or relatively equivalent in terms of shape and size will produce identical or relatively identical image quality and patient dose. Simple mathematical models and software program EQSPECT.FOR were developed for the comparative evaluation of the performance characteristics in terms of contrast (C), contrast to noise ratio (CNR) and figure-of-merit (FOM = CNR2/DOSE) for spectrally equivalent beams transmitted through filter materials referred to as conventional and k-edged. At the same value of operating potential (kVp), results show that spectrally equivalent beam transmitted through conventional filter with higher atomic number (Z-value) in comparison with that transmitted through conventional filter with lower Z-value resulted in the same value of C and FOM. However, in comparison with the spectrally equivalent beam transmitted through filter of lower Z-value, the beam through filter of higher Z-value produced higher value of CNR and DOSE at equal tube loading (mAs) and kVp. Under the condition of equivalence of spectrum, at scaled (or reduced) tube loading and same kVp, filter materials of higher Z-value can produce the same values of C, CNR, DOSE and FOM as filter materials of lower Z-value. Unlike the case of comparison of spectrally equivalent beam transmitted through one conventional filter and that through another conventional filter, it is not possible to derive simple mathematical formulations for the relative performance of spectrally equivalent beam transmitted through a given conventional filter material and that through kedge filter material. PMID:21224928

Double Z-scheme ZnO/ZnS/g-C3N4 ternary structure for efficient photocatalytic H2 production

NASA Astrophysics Data System (ADS)

Dong, Zhifang; Wu, Yan; Thirugnanam, Natarajan; Li, Gonglin

2018-02-01

In the present work, a novel ZnO/ZnS/g-C3N4 ternary nanocomposite with double Z-scheme heterojunction has been designed via a two-step facile chemical conversion route. The spherical ZnS nanoparticles were uniformly loaded onto ZnO nanoflowers surface. And then the ZnO/ZnS nanocomposite was further hybridized with g-C3N4 nanosheets. Ternary ZnO/ZnS/g-C3N4 nanocomposite displays the largest specific surface area (about 76.2 m2/g), which provides plentiful activated sites for photocatalytic reaction. Furthermore, the ternary material exhibits the highest methylene blue photodegradation rate of about 0.0218 min-1 and the optimum photocatalytic H2 production (1205 μmol/g) over water splitting at 4 h under solar light irradiation. Moreover, it showed the highest photocurrent effect and the minimum charge-transfer resistance. These results implied that the higher photoactivity of ZnO/ZnS/g-C3N4 nanocomposite could be attributed to the multi-steps charge transfer and effective electron-hole separation in the double Z-scheme system.

Hot Isostatic Pressing of Engineered Forms of I-AgZ

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

Jubin, Robert Thomas; Watkins, Thomas R.; Bruffey, Stephanie H.

Hot isostatic pressing (HIP) is being considered for direct conversion of 129I-bearing materials to a radiological waste form. The removal of volatile radioactive 129I from the off-gas of a nuclear fuel reprocessing facility will be necessary to comply with regulatory requirements regarding reprocessing facilities sited within the United States, and any iodine-containing media or solid sorbents generated by offgas abatement will require disposal. Zeolite minerals such as silver-exchanged mordenite (AgZ) have been studied as potential iodine sorbents and will contain 129I as chemisorbed AgI. Oak Ridge National Laboratory (ORNL) has conducted several recent studies on the HIP of both iodine-loadedmore » AgZ (I-AgZ) and other iodine-bearing zeolite minerals. The goal of these research efforts is to achieve a stable, highly leach resistant material that is reduced in volume as compared to bulk iodine-loaded I-AgZ. Through the use of HIP, it may be possible to achieve this with the addition of little or no additional materials (waste formers). Other goals for the process include that the waste form will be tolerant to high temperatures and pressures, not chemically hazardous, and that the process will result in minimal secondary waste generation. This document describes the preparation of 27 samples that are distinct from previous efforts in that they are prepared exclusively with an engineered form of AgZ that is manufactured using a binder. Iodine was incorporated solely by chemisorption. This base material is expected to be more representative of an operational system than were samples prepared previously with pure minerals.« less

Response mechanisms of attached premixed flames subjected to harmonic forcing

NASA Astrophysics Data System (ADS)

Shreekrishna

The persistent thrust for a cleaner, greener environment has prompted air pollution regulations to be enforced with increased stringency by environmental protection bodies all over the world. This has prompted gas turbine manufacturers to move from nonpremixed combustion to lean, premixed combustion. These lean premixed combustors operate quite fuel-lean compared to the stochiometric, in order to minimize CO and NOx productions, and are very susceptible to oscillations in any of the upstream flow variables. These oscillations cause the heat release rate of the flame to oscillate, which can engage one or more acoustic modes of the combustor or gas turbine components, and under certain conditions, lead to limit cycle oscillations. This phenomenon, called thermoacoustic instabilities, is characterized by very high pressure oscillations and increased heat fluxes at system walls, and can cause significant problems in the routine operability of these combustors, not to mention the occasional hardware damages that could occur, all of which cumulatively cost several millions of dollars. In a bid towards understanding this flow-flame interaction, this research works studies the heat release response of premixed flames to oscillations in reactant equivalence ratio, reactant velocity and pressure, under conditions where the flame preheat zone is convectively compact to these disturbances, using the G-equation. The heat release response is quantified by means of the flame transfer function and together with combustor acoustics, forms a critical component of the analytical models that can predict combustor dynamics. To this end, low excitation amplitude (linear) and high excitation amplitude (nonlinear) responses of the flame are studied in this work. The linear heat release response of lean, premixed flames are seen to be dominated by responses to velocity and equivalence ratio fluctuations at low frequencies, and to pressure fluctuations at high frequencies which are in the vicinity of typical screech frequencies in gas turbine combustors. The nonlinear response problem is exclusively studied in the case of equivalence ratio coupling. Various nonlinearity mechanisms are identified, amongst which the crossover mechanisms, viz., stoichiometric and flammability crossovers, are seen to be responsible in causing saturation in the overall heat release magnitude of the flame. The response physics remain the same across various preheat temperatures and reactant pressures. Finally, comparisons between the chemiluminescence transfer function obtained experimentally and the heat release transfer functions obtained from the reduced order model (ROM) are performed for lean, CH4/Air swirl-stabilized, axisymmetric V-flames. While the comparison between the phases of the experimental and theoretical transfer functions are encouraging, their magnitudes show disagreement at lower Strouhal number gains show disagreement.

Effects of elliptical burner geometry on partially premixed gas jet flames in quiescent surroundings

NASA Astrophysics Data System (ADS)

Baird, Benjamin

This study is the investigation of the effect of elliptical nozzle burner geometry and partial premixing, both 'passive control' methods, on a hydrogen/hydrocarbon flame. Both laminar and turbulent flames for circular, 3:1, and 4:1 aspect ratio (AR) elliptical burners are considered. The amount of air mixed with the fuel is varied from fuel-lean premixed flames to fuel-rich partially premixed flames. The work includes measurements of flame stability, global pollutant emissions, flame radiation, and flame structure for the differing burner types and fuel conditions. Special emphasis is placed on the near-burner region. Experimentally, both conventional (IR absorption, chemiluminecent, and polarographic emission analysis,) and advanced (laser induced fluorescence, planar laser induced fluorescence, Laser Doppler Velocimetry (LDV), Rayleigh scattering) diagnostic techniques are used. Numerically, simulations of 3-dimensional laminar and turbulent reacting flow are conducted. These simulations are run with reduced chemical kinetics and with a Reynolds Stress Model (RSM) for the turbulence modeling. It was found that the laminar flames were similar in appearance and overall flame length for the 3:1 AR elliptical and the circular burner. The laminar 4:1 AR elliptical burner flame split into two sub-flames along the burner major axis. This splitting had the effect of greatly shortening the 4:1 AR elliptical burner flame to have an overall flame length about half of that of the circular and 3:1 AR elliptical burner flames. The length of all three burners flames increased with increasing burner exit equivalence ratio. The blowout velocity for the three burners increased with increase in hydrogen mass fraction of the hydrogen/propane fuel mixture. For the rich premixed flames, the circular burner was the most stable, the 3:1 AR elliptical burner, was the least stable, and the 4:1 AR elliptical burner was intermediate to the two other burners. This order of stability was due to two reasons. The elliptical burners have enhanced turbulence generation that lowers their stability when compared to the circular burner. The 4:1 AR elliptical burner had greater stability due to a greater velocity decay rate and wider OH reaction zones particularly in the region between the two jets. The 3:1 AR elliptical and circular burners produced similar carbon monoxide and nitric oxide emission indexes over the range of equivalence ratios of 0.55 to 4.0, for laminar flames. (Abstract shortened by UMI.)

Optimal parameters for laser tissue soldering: II. Premixed versus separate dye-solder techniques.

PubMed

McNally, K M; Sorg, B S; Chan, E K; Welch, A J; Dawes, J M; Owen, E R

2000-01-01

Laser tissue soldering by using an indocyanine green (ICG)-doped protein solder applied topically to the tissue surface and denatured with a diode laser was investigated in Part I of this study. The depth of light absorption was predominantly determined by the concentration of the ICG dye added to the solder. This study builds on that work with an in vitro investigation of the effects of limiting the zone of heat generation to the solder-tissue interface to determine whether more stable solder-tissue fusion can be achieved. An alternative laser tissue soldering technique was investigated, which increased light absorption at the vital solder-tissue interface. A thin layer of ICG dye was smeared over the surface to be treated, the protein solder was then placed directly on top of the dye, and the solder was denatured with an 808-nm diode laser. Because laser light at approximately 800 nm is absorbed primarily by the ICG dye, this thin layer of ICG solution restricted the heat source to the space between the solder and the tissue surfaces. A tensile strength analysis was conducted to compare the separate dye-solder technique with conventional techniques of laser tissue soldering for which a premixed dye-solder is applied directly to the tissue surface. The effect of hydration on bond stability of repairs formed by using both techniques was also investigated using tensile strength and scanning electron microscopy analysis. Equivalent results in terms of tensile strength were obtained for the premixed dye-solder technique using protein solders containing 0.25 mg/ml ICG (liquid solder, 220 +/- 35 N/cm(2); solid solder, 602 +/- 32 N/cm(2)) and for the separate dye-solder technique (liquid solder, 228 +/- 41 N/cm(2); solid solder, 578 +/- 29 N/cm(2)). The tensile strength of native bovine thoracic aorta was 596 +/- 31 N/cm(2). Repairs created by using the separate dye-solder technique were more stable during hydration than their premixed dye-solder counterparts. The conventional premixed dye-solder was simpler and approximately twice as fast to apply. The separate dye-solder technique, however, increased the shelf-life of the solder, because the dye was mixed at the time of the experiment, thus conserving its spectral absorbency properties. Two laser-assisted tissue soldering techniques have been evaluated for repairing aorta incisions in vitro. The advantages and disadvantages of each of these techniques are discussed. Copyright 2000 Wiley-Liss, Inc.

Ionization and chemiluminescence during the progressive aeration of methane flames

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

Weinberg, Felix; Carleton, Fred

Saturation currents and chemiluminescence, especially at the CH{sup *} and C{sub 2}{sup *} wavelengths, are measured for a range of small, laminar methane flames during progressive addition of air, with the principal objective of distinguishing between pure diffusion flames, premixed flames of compositions falling between the upper and lower flammability limits, and the broad range of aerated flames lying in between these regimes. Flame areas defined by the loci of maximum luminosity and by schlieren contours were recorded, so that saturation current densities, CH{sup *} and C{sub 2}{sup *} emission per unit flame area, as well as burning velocities couldmore » be deduced. For admixtures of less than 70 vol.%, air appears to act, surprisingly, as an inert diluent as regards saturation currents, so that saturation currents are essentially proportional to fuel flow alone. Much the same applies to chemiluminescence. However, schlieren contours, which were recorded both to provide a basis for burning velocity measurements and to explore density changes in the reactants, indicated the presence of a burner - stabilised propagating reaction zone ahead of the luminous flame surface starting at around 50 vol.% and possibly even at lower air admixtures. This evidence of a steep change in refractive index is indicative of a premixed reaction zone involving the added oxygen, which however generates no chemi-ionization and emits no light. Even photographing the flame by radiation emitted at the CH{sup *} and C{sub 2}{sup *} wavelengths shows no sign of its existence. Its burning velocity is about 10 cm/s, when stabilized by the surrounding diffusion flame. The most plausible rationale for these observations is the formation of syngas by the partial oxidation of methane. The subsequent burning of CO and H{sub 2} is known to occur without chemi-ionization or appreciable light emission. (author)« less

Effects of Inert Dust Clouds on the Extinction of Strained, Laminar Flames at Normal and Micro Gravity

NASA Technical Reports Server (NTRS)

Andac, M. Gurhan; Egolfopoulos, Fokion N.; Campbell, Charles S.; Lauvergne, Romain; Wu, Ming-Shin (Technical Monitor)

2000-01-01

A combined experimental and detailed numerical study was conducted on the interaction between chemically inert solid particles and strained, atmospheric methane/air and propane/air laminar flames, both premixed and non-premixed. Experimentally, the opposed jet configuration was used with the addition of a particle seeder capable of operating in conditions of varying gravity. The particle seeding system was calibrated under both normal and micro gravity and a noticeable gravitational effect was observed. Flame extinction experiments were conducted at normal gravity by seeding inert particles at various number densities and sizes into the reacting gas phase. Experimental data were taken for 20 and 37 (mu) nickel alloy and 25 and 60 (mu) aluminum oxide particles. The experiments were simulated by solving along the stagnation streamline the conservation equations of mass, momentum, energy, and species conservation for both phases, with detailed descriptions of chemical kinetics, molecular transport, and thermal radiation. The experimental data were compared with numerical simulations, and insight was provided into the effects on extinction of the fuel type, equivalence ratio, flame configuration, strain rate. particle type. particle size. particle mass, delivery rate. the orientation of particle injection with respect to the flame and gravity. It was found that for the same injected solid mass, larger particles can result in more effective flame cooling compared to smaller particles, despite the fact that equivalent masses of the larger particles have smaller total surface area to volume ratio. This counter-intuitive finding resulted from the fact that the heat exchange between the two phases is controlled by the synergistic effect of the total contact area and the temperature difference between the two phases. Results also demonstrate that meaningful scaling of interactions between the two phases may not be possible due to the complexity of the couplings between the dynamic and thermal parameters of the problem.

Remedial Investigation Report, Presidio Main Installation, Presidio of San Francisco. Volume 5: Figures 7-15

DTIC Science & Technology

1997-01-01

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Effects of Buoyancy on Laminar and Turbulent Premixed V-Flame

NASA Technical Reports Server (NTRS)

Cheng, Robert K.; Bedat, Benoit

1997-01-01

Turbulent combustion occurs naturally in almost all combustion systems and involves complex dynamic coupling of chemical and fluid mechanical processes. It is considered as one of the most challenging combustion research problems today. Though buoyancy has little effect on power generating systems operating under high pressures (e.g., IC engines and turbines), flames in atmospheric burners and the operation of small to medium furnaces and boilers are profoundly affected by buoyancy. Changes in burner orientation impacts on their blow-off, flash-back and extinction limits, and their range of operation, burning rate, heat transfer, and emissions. Theoretically, buoyancy is often neglected in turbulent combustion models. Yet the modeling results are routinely compared with experiments of open laboratory flames that are obviously affected by buoyancy. This inconsistency is an obstacle to reconciling experiments and theories. Consequently, a fundamental understanding of the coupling between turbulent flames and buoyancy is significant to both turbulent combustion science and applications. The overall effect of buoyancy relates to the dynamic interaction between the flame and its surrounding, i.e., the so-called elliptical problem. The overall flame shape, its flowfield, stability, and mean and local burning rates are dictated by both upstream and downstream boundary conditions. In steady propagating premixed flames, buoyancy affects the products region downstream of the flame zone. These effects are manifested upstream through the mean and fluctuating pressure fields to influence flame stretch and flame wrinkling. Intuitively, the effects buoyancy should diminish with increasing flow momentum. This is the justification for excluding buoyancy in turbulent combustion models that treats high Reynolds number flows. The objectives of our experimental research program is to elucidate flame-buoyancy coupling processes in laminar and turbulent premixed flames, and to characterize microgravity (micro g) premixed flames. The results are used to derive appropriate scaling parameters for guiding the development of theoretical models to include the effects of buoyancy. Knowledge gain from the analysis will also contribute to further understanding of the elliptical nature of premixed flames. Our current emphasis is to examine the momentum limit above which the effects of buoyancy would become insignificant. This is accomplished by comparing the flowfields and the mean properties of normal gravity flames (+g), and reversed gravity flames (-g, up-side-down flames) at different flow velocities and turbulence intensities. Microgravity (micro g) flames experiments provide the key reference data to reconcile the differences between flames in +g and -g. As flame configuration has significant impact on premixed flames characteristics we have studied axi-symmetric conical flames and plane-symmetric rod-stabilized v-flames. The two configurations produce distinct features that dictates how the flames couple with buoyancy. In a conical flame, the hot products plume completely envelopes the flame cone and shields the flame from direct interaction with the ambient air. The plume originates at the burner rim and generates a divergent flowfield. In comparison, the products region of v-flames forms between the twin flame sheets and it is convergent towards the center-plane. Interaction with ambient air is limited to the two end regions of the stabilized rod and beyond the flame sheets.

Full-Wave Based Validation of Stripline Field Applicator For Low Frequency Material Measurements

DTIC Science & Technology

2009-03-01

16 3.3.1 Principal Solution. . . . . . . . . . . . . . . . . 17 3.3.2 Reflected Solution. . . . . . . . . . . . . . . . . 22 3.4 Applying...potential) [ 17 ]. The vector potential BCs are found to be Ax(x, y = ±h, z) = 0 ∀ x, z (3.2) ∂Ay(x, y = ±h, z) ∂y = 0 ∀ x, z (3.3) Az(x, y = ±h, z...solution at y = ±h, an inverse Fourier transform must be performed on the principal contribution 17 ηre ηim x x η-plane −jp jp Figure 3.2

Nonlinear Optical Properties of Aluminum Doped Zinc Oxide

NASA Astrophysics Data System (ADS)

Otieno, Calford O.

Nonlinear optical (NLO) materials are crucial to future progress in industrial and technological applications that involve intense light-matter interaction. While ZnO-related materials are known to possess good NLO properties, existing results on ZnO and AZO (Al-doped ZnO) are mostly available at a single wavelength or limited ranges. Therefore, NLO dispersions (wavelength dependences) are not entirely studied, especially at longer wavelengths far below the bandgap. It is important to explore wavelength dependences since doping can induce a drastic change in the NLO responses at varied spectral ranges via doping-induced subgap-state contributions. We present results of our studies on nonlinear harmonic generation from our samples, which include 1) second harmonic generation and 2) third harmonic generation precisely characterized by Maker fringes as a function of both Al doping and wavelength. We exhaustively discuss the possible cause for the modified optical nonlinearities observed in our AZO thin films and give detailed comparisons of our observations with the previous studies. We also present the results of open- and close-aperture Z-scans to characterize the two-photon absorption coefficient (TPA) and the nonlinear refractive index (NLR), respectively, of the AZO films. There was no clearcut evidence of monotonic dependence of TPA and NLR on doping. This presumably indicates that the overall effect is nontrivial and should be understood in terms of combined effects of bandgap shift and crystallinity upon varying the doping level. Most intriguingly, we found that NLR values from the closed-aperture Z-scan are very large by orders of magnitude when compared with the bulk counterparts. Similar observation was made for TPA values from the open-aperture Z-scan. To countercheck very large NLO absorption, we conducted simple intensity scan by varying the incident photon number on each sample but fixing the beam area to eliminate any possible errors related to optical damage at the Z-scan focus. However, we confirmed that the TPA values are also very large and comparable to those obtained by the open-aperture Z-scan. We try to explain this very large nonlinearity by seriously considering the previously proposed models.

Principal curvatures and area ratio of propagating surfaces in isotropic turbulence

NASA Astrophysics Data System (ADS)

Zheng, Tianhang; You, Jiaping; Yang, Yue

2017-10-01

We study the statistics of principal curvatures and the surface area ratio of propagating surfaces with a constant or nonconstant propagating velocity in isotropic turbulence using direct numerical simulation. Propagating surface elements initially constitute a plane to model a planar premixed flame front. When the statistics of evolving propagating surfaces reach the stationary stage, the statistical profiles of principal curvatures scaled by the Kolmogorov length scale versus the constant displacement speed scaled by the Kolmogorov velocity scale collapse at different Reynolds numbers. The magnitude of averaged principal curvatures and the number of surviving surface elements without cusp formation decrease with increasing displacement speed. In addition, the effect of surface stretch on the nonconstant displacement speed inhibits the cusp formation on surface elements at negative Markstein numbers. In order to characterize the wrinkling process of the global propagating surface, we develop a model to demonstrate that the increase of the surface area ratio is primarily due to positive Lagrangian time integrations of the area-weighted averaged tangential strain-rate term and propagation-curvature term. The difference between the negative averaged mean curvature and the positive area-weighted averaged mean curvature characterizes the cellular geometry of the global propagating surface.

An Experimental Investigation of Premixed Combustion in Extreme Turbulence

NASA Astrophysics Data System (ADS)

Wabel, Timothy Michael

This work has explored various aspects of high Reynolds number combustion that have received much previous speculation. A new high-Reynolds number premixed Bunsen burner, called Hi-Pilot, was designed to produce turbulence intensities in the extreme range of turbulence. The burner was modified several times in order to prevent boundary layer separation in the nozzle, and a large co-flow was designed that was capable of maintaining reactions over the entire flame surface. Velocity and turbulence characteristics were measured using a combination of Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV). Flame structure was studied using a combination of formaldehyde (CH2O), hydroxyl (OH), and the CH radical. Planar Laser Induced Fluorescence (PLIF). The spatial Overlap of formaldehyde and OH PLIF qualitatively measures the reaction rate between formaldehyde molecules and OH radicals, and is a measure of the reaction layers of the flame. CH PLIF provides an alternative measure of the reaction zone, and was measured to compare with the Overlap PLIF results. Reaction layers are the full-width at half-maximum of the Overlap or CH PLIF signal, and extinction events were defined as regions where the PLIF signal drops below this threshold. Preheat structures were measured using formaldehyde PLIF, and are defined as beginning at 35% of the local maximum PLIF signal, and continue up to the leading edge of the reaction layer. Previous predictions of regime diagram boundaries were tested at the largest values of turbulent Reynolds number to date. The Overlap and CH PLIF diagnostics allowed extensive testing of the predicted broken reaction zones boundary of Peters. Measurements indicated that all run conditions are in the Broadened Preheat - Thin Reaction layers regime, but several conditions are expected to display a broken reaction zone structure. Therefore the work shows that Peters's predicted boundary is not correct, and therefore a Karlovitz number of 100 is not a valid criteria for broken reactions in the Bunsen geometry. Several measures of the turbulent burning velocity, including the global consumption speed and the extent of flamelet wrinkling, were measured at these conditions. Reaction layers for the burning velocity measurements were provided by the OH PLIF. The measurements showed that the global consumption speed continues to increase for all levels of turbulence intensity u'/SL. In contrast, the flame surface wrinkling rapidly increases the flame surface area for u'/SL < 10, but the flame surface area does not increase further at larger turbulence intensities. This indicates that the flame is not in the laminar flamelet regime, and the consumption rate per unit of flame surface area must be increased. The turbulent diffusivity is thought to be the mechanism enhancing the consumption rate, which is a scenario first hypothesized by Damkohler. The flame structure and burning velocity measurements motivated the measurements of the evolution of turbulence through regions of very thick preheat layers. This measurement utilized simultaneous PIV and formaldehyde PLIF in order to obtain conditioned statistics of the turbulence as a function of eta, the distance from the reaction layer. Together, the results tell a consistent story, and deepen our understanding of premixed combustion at large turbulent Reynolds number.

A magnetic topological semimetal Sr 1-yMn 1-zSb2 (y, z < 0.10)

DOE PAGES

Liu, J. Y.; Hu, J.; Zhang, Qiang; ...

2017-07-24

Weyl (WSMs) evolve from Dirac semimetals in the presence of broken time-reversal symmetry (TRS) or space-inversion symmetry. The WSM phases in TaAs-class materials and photonic crystals are due to the loss of space-inversion symmetry. For TRS-breaking WSMs, despite numerous theoretical and experimental efforts, few examples have been reported. Here in this paper, we report a new type of magnetic semimetal Sr 1-yMn 1-zSb 2 (y, z < 0.1) with nearly massless relativistic fermion behaviour (m* = 0.04 - 0.05m 0, where m 0 is the free-electron mass). This material exhibits a ferromagnetic order for 304 K < T < 565more » K, but a canted antiferromagnetic order with a ferromagnetic component for T < 304 K. The combination of relativistic fermion behaviour and ferromagnetism in Sr 1-yMn 1-zSb2 offers a rare opportunity to investigate the interplay between relativistic fermions and spontaneous TRS breaking.« less

A magnetic topological semimetal Sr 1-yMn 1-zSb2 (y, z < 0.10)

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

Liu, J. Y.; Hu, J.; Zhang, Qiang

Weyl (WSMs) evolve from Dirac semimetals in the presence of broken time-reversal symmetry (TRS) or space-inversion symmetry. The WSM phases in TaAs-class materials and photonic crystals are due to the loss of space-inversion symmetry. For TRS-breaking WSMs, despite numerous theoretical and experimental efforts, few examples have been reported. Here in this paper, we report a new type of magnetic semimetal Sr 1-yMn 1-zSb 2 (y, z < 0.1) with nearly massless relativistic fermion behaviour (m* = 0.04 - 0.05m 0, where m 0 is the free-electron mass). This material exhibits a ferromagnetic order for 304 K < T < 565more » K, but a canted antiferromagnetic order with a ferromagnetic component for T < 304 K. The combination of relativistic fermion behaviour and ferromagnetism in Sr 1-yMn 1-zSb2 offers a rare opportunity to investigate the interplay between relativistic fermions and spontaneous TRS breaking.« less

Continuous coal processing method

NASA Technical Reports Server (NTRS)

Ryason, P. R. (Inventor)

1980-01-01

A coal pump is provided in which solid coal is heated in the barrel of an extruder under pressure to a temperature at which the coal assumes plastic properties. The coal is continuously extruded, without static zones, using, for example, screw extrusion preferably without venting through a reduced diameter die to form a dispersed spray. As a result, the dispersed coal may be continuously injected into vessels or combustors at any pressure up to the maximum pressure developed in the extrusion device. The coal may be premixed with other materials such as desulfurization aids or reducible metal ores so that reactions occur, during or after conversion to its plastic state. Alternatively, the coal may be processed and caused to react after extrusion, through the die, with, for example, liquid oxidizers, whereby a coal reactor is provided.

In vitro gastrointestinal mimetic protocol for measuring bioavailable contaminants

DOEpatents

Holman, Hoi-Ying N.

2000-01-01

The present invention relates to measurements of contaminants in the soil and other organic or environmental materials, using a biologically relevant chemical analysis that will measure the amount of contaminants in a given sample that may be expected to be absorbed by a human being ingesting the contaminated soil. According to the present invention, environmental samples to be tested are added to a pre-prepared physiological composition of bile salts and lipids. They are thoroughly mixed and then the resulting mixture is separated e.g. by centrifugation. The supernatant is then analyzed for the presence of contaminants and these concentrations are compared to the level of contaminants in the untreated samples. It is important that the bile salts and lipids be thoroughly pre-mixed to form micelles.

Imaging and Radiography with Nuclear Resonance Fluorescence and Effective-Z (EZ-3D) Determination; SNM Detection Using Prompt Neutrons from Photon Induced Fission

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

Bertozzi, William; Hasty, Richard; Klimenko, Alexei

Four new technologies have been developed for use in non-intrusive inspection systems to detect nuclear materials, explosives and contraband. Nuclear Resonance Fluorescence (NRF) provides a three dimensional image of the isotopic content of a container. NRF determines the isotopic composition of a region and specifies the isotopic structure of the neighboring regions, thus providing the detailed isotopic composition of any threat. In transmission mode, NRF provides a two dimensional projection of the isotopic content of a container, much as standard X-ray radiography provides for density. The effective-Z method (EZ-3D) uses electromagnetic scattering processes to yield a three-dimensional map of themore » effective-Z and the density in a container. The EZ-3D method allows for a rapid discrimination based on effective Z and mass of materials such as those with high Z, as well as specifying regions of interest for other contraband. The energy spectrum of prompt neutrons from photon induced fission (PNPF) provides a unique identification of the presence of actinides and SNM. These four new technologies can be used independently or together to automatically determine the presence of hazardous materials or contraband. They can also be combined with other technologies to provide added specificity.« less

Propagation of a premixed flame in a divided-chamber combustor

NASA Technical Reports Server (NTRS)

Cattolica, R. J.; Barr, P. K.; Mansour, N. N.

1989-01-01

Experimental observations on the propagation of lean premixed ethylene-air flames in a divided-chamber combustion vessel have been compared with the results of numerical simulations based on a flame sheet-vortex dynamics model in axisymmetric coordinates. Flame speeds were found to increase from 10-24 cm/s as the equivalence ratio was varied from 0.5-0.65 in the experiments. Using the associated increase in gas velocity with equivalence ratio, the estimated Reynolds number in the experiment was changed from 1870 to 8090. Good agreement between experimental and theoretical results was obtained for the prechamber flame propagation rates and for the spatial and temporal development of the flame in the main combustion chamber at the lowest Reynolds number.

Identification of combustion intermediates in low-pressure premixed pyridine/oxygen/argon flames.

PubMed

Tian, Zhenyu; Li, Yuyang; Zhang, Taichang; Zhu, Aiguo; Qi, Fei

2008-12-25

Combustion intermediates of two low-pressure premixed pyridine/oxygen flames with respective equivalence ratios of 0.56 (C/O/N = 1:4.83:0.20) and 2.10 (C/O/N = 1:1.29:0.20) have been identified with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry techniques. About 80 intermediates in the rich flame and 60 intermediates in the lean flame, including nitrogenous, oxygenated, and hydrocarbon intermediates, have been identified by measurements of photoionization mass spectra and photoionization efficiency spectra. Some radicals and new nitrogenous intermediates are identified in the present work. The experimental results are useful for studying the conversion of volatile nitrogen compounds and understanding the formation mechanism of NO(x) in flames of nitrogenous fuels.

Premixed flames in closed cylindrical tubes

NASA Astrophysics Data System (ADS)

Metzener, Philippe; Matalon, Moshe

2001-09-01

We consider the propagation of a premixed flame, as a two-dimensional sheet separating unburned gas from burned products, in a closed cylindrical tube. A nonlinear evolution equation, that describes the motion of the flame front as a function of its mean position, is derived. The equation contains a destabilizing term that results from the gas motion induced by thermal expansion and has a memory term associated with vorticity generation. Numerical solutions of this equation indicate that, when diffusion is stabilizing, the flame evolves into a non-planar form whose shape, and its associated symmetry properties, are determined by the Markstein parameter, and by the initial data. In particular, we observe the development of convex axisymmetric or non-axisymmetric flames, tulip flames and cellular flames.

Premix fuels study applicable to duct burner conditions for a variable cycle engine

NASA Technical Reports Server (NTRS)

Venkataramani, K. S.

1978-01-01

Emission levels and performance of a premixing Jet-A/air duct burner were measured at reference conditions representative of take-off and cruise for a variable cycle engine. In a parametric variation sequence of tests, data were obtained at inlet temperatures of 400, 500 and 600K at equivalence ratios varying from 0.9 to the lean stability limit. Ignition was achieved at all the reference conditions although the CO levels were very high. Significant nonuniformity across the combustor was observed for the emissions at the take-off condition. At a reference Mach number of 0.117 and an inlet temperature of 600K, corresponding to a simulated cruise condition, the NOx emission level was approximately 1 gm/kg-fuel.

Catalytic combustion of residual fuels

NASA Technical Reports Server (NTRS)

Bulzan, D. L.; Tacina, R. R.

1981-01-01

A noble metal catalytic reactor was tested using two grades of petroleum derived residual fuels at specified inlet air temperatures, pressures, and reference velocities. Combustion efficiencies greater than 99.5 percent were obtained. Steady state operation of the catalytic reactor required inlet air temperatures of at least 800 K. At lower inlet air temperatures, upstream burning in the premixing zone occurred which was probably caused by fuel deposition and accumulation on the premixing zone walls. Increasing the inlet air temperature prevented this occurrence. Both residual fuels contained about 0.5 percent nitrogen by weight. NO sub x emissions ranged from 50 to 110 ppm by volume at 15 percent excess O2. Conversion of fuel-bound nitrogen to NO sub x ranged from 25 to 50 percent.

Flashback detection sensor for lean premix fuel nozzles

DOEpatents

Thornton, Jimmy Dean [Morgantown, WV; Richards, George Alan [Morgantown, WV; Straub, Douglas L [Morgantown, WV; Liese, Eric Arnold [Morgantown, WV; Trader, Jr., John Lee; Fasching, George Edward [Morgantown, WV

2002-08-06

A sensor for detecting the flame occurring during a flashback condition in the fuel nozzle of a lean premix combustion system is presented. The sensor comprises an electrically isolated flashback detection electrode and a guard electrode, both of which generate electrical fields extending to the walls of the combustion chamber and to the walls of the fuel nozzle. The sensor is positioned on the fuel nozzle center body at a location proximate the entrance to the combustion chamber of the gas turbine combustion system. The sensor provides 360.degree. detection of a flashback inside the fuel nozzle, by detecting the current conducted by the flame within a time frame that will prevent damage to the gas turbine combustion system caused by the flashback condition.

Combustion efficiency of a premixed continuous flow combustor

NASA Technical Reports Server (NTRS)

Anand, M. S.; Gouldin, F. C.

1985-01-01

Exhaust gas temperature, velocity, and composition measurements at various radial locations at the combustor exit are presented for a swirling-flow continuous combustor of a confined concentric jet configuration operating on premixed propane or methane and air. The main objective of the study is to determine the effect of fuel substitution and of changes in outer flow swirl conditions on the combustor performance. It is found that there is no difference in observed properties for propane and methane firing; the use of either of the fuels results in nearly the same exit temperature and velocity profiles and the same efficiency for a given operating condition. A mechanism for combustion is proposed which explains qualitatively the changes in efficiency and pollutant emissions observed with changing swirl.

Experimental evaluation of two premixing-prevaporizing fuel injection concepts for a gas turbine catalytic combustor

NASA Technical Reports Server (NTRS)

Tacina, R.

1976-01-01

A premixing-prevaporizing fuel system for a gas turbine catalytic combustor has been developed and evaluated. Spatial fuel distribution and degree of vaporization were measured at inlet temperatures up to 800 K and fuel-air ratios of 0.01 and 0.025. The test pressure was 0.5 MPa; velocity was 20 m/sec. Both a multiple-jet cross-stream injector and a splash-groove injector with a 30 deg air swirler exhibited a uniform fuel distribution and a high degree of vaporization with little total pressure drop. Fuel oxidation reactions were observed at the 800 K inlet air temperature, indicating that a different design concept is necessary for application with an automotive gas turbine.

Selecting a Z39.50 Client or Web Gateway.

ERIC Educational Resources Information Center

Turner, Fay

1998-01-01

Provides a brief description of the Z39.50 information retrieval standard and reviews evaluation criteria and questions that should be asked when selecting a Z39.50 client. Areas for consideration include whether to buy or build a Z39.50 client, the end-user's requirements, connecting to a remote server, searching, managing the search response,…

Radiation fields from neutron generators shielded with different materials

NASA Astrophysics Data System (ADS)

Chichester, D. L.; Blackburn, B. W.

2007-08-01

As a general guide for assessing radiological conditions around a DT neutron generator numerical modeling has been performed to assess neutron and photon dose profiles for a variety of shield materials ranging from 1 to 100 cm thick. In agreement with accepted radiation safety practices high-Z materials such as bismuth and lead have been found to be ineffective biological shield materials, owing in part to the existence of (n,2n) reaction channels available with 14.1 MeV DT neutrons, while low-Z materials serve as effective shields for these sources. Composite materials such as a mixture of polyethylene and bismuth, or regular concrete, are ideal shield materials for neutron generator radiation because of their ability to attenuate internally generated photon radiation resulting from neutron scattering and capture within the shields themselves.

Anode materials for lithium ion batteries

DOEpatents

Abouimrane, Ali; Amine, Khalil

2015-06-09

A composite material has general Formula (1-x)J-(x)Q wherein: J is a metal carbon alloy of formula Sn.sub.zSi.sub.z'Met.sub.wMet'.sub.w'C.sub.t; Q is a metal oxide of formula A.sub..gamma.M.sub..alpha.M'.sub..alpha.'O.sub..beta.; A is Li, Na, or K; M, M', Met, and Met' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; 0

Synthesis of 13(R)-Hydroxy-7Z,10Z,13R,14E,16Z,19Z Docosapentaenoic Acid (13R-HDPA) and Its Biosynthetic Conversion to the 13-Series Resolvins

PubMed Central

2016-01-01

Specialized pro-resolving lipid mediators are biosynthesized during the resolution phase of acute inflammation from n-3 polyunsaturated fatty acids. Recently, the isolation and identification of the four novel mediators denoted 13-series resolvins, namely, RvT1 (1), RvT2 (2), RvT3 (3) and RvT4 (4), were reported, which showed potent bioactions characteristic for specialized pro-resolving lipid mediators. Herein, based on results from LC/MS-MS metabololipidomics and the stereoselective synthesis of 13(R)-hydroxy-7Z,10Z,13R,14E,16Z,19Z docosapentaenoic acid (13R-HDPA, 5), we provide direct evidence that the four novel mediators 1–4 are all biosynthesized from the pivotal intermediate 5. The UV and LC/MS-MS results from synthetic 13R-HDPA (5) matched those from endogenously and biosynthetically produced material obtained from in vivo infectious exudates, endothelial cells, and human recombinant COX-2 enzyme. Stereochemically pure 5 was obtained with the use of a chiral pool starting material that installed the configuration at the C-13 atom as R. Two stereoselective Z-Wittig reactions and two Z-selective reductions of internal alkynes afforded the geometrically pure alkene moieties in 5. Incubation of 5 with isolated human neutrophils gave all four RvTs. The results presented herein provide new knowledge on the biosynthetic pathways and the enzymatic origin of RvTs 1–4. PMID:27704804

Utilisation of polyurethane composit with 50% composition of roystonea regia fiber as noise reduction panel on car hood

NASA Astrophysics Data System (ADS)

Ikhwansyah; Mulia; Gunawan, S.; Lubis, R. D. W.

2018-02-01

The objective is to get the characteristics of noise reduction, noise reduction level, variety of measurement spaces, and knowing the process in making acoustic material of natural fiber becomes noise reduction on a car hood. The process of making noise reduction material used casting method and pressed by using molded press. The composition of noise reduction material consist of 50% roystonea regia by 32 mesh and 50% combined by gypsum and polyurethane. The result shows that the average result of noise reduction at X1- side is 5,7% and X2- side is 3,9%, X1+ side is 0,9% and X2+ side is 6,2%, Z1- side is 8,9% and Z2- side is 10,1%, Z1+ side is 9,7% and Z2+ side is 10,01%. The main conclusion of the study shows that a noise reduction which made of roystonea regia with 32 mesh mixed by matrix of polyurethane and gypsum is appropriate for noise reduction on car hood.

First wall for polarized fusion reactors

DOEpatents

Greenside, H.S.; Budny, R.V.; Post, D.E. Jr.

1985-01-29

A first-wall or first-wall coating for use in a fusion reactor having polarized fuel may be formed of a low-Z non-metallic material having slow spin relaxation, i.e., a depolarization rate greater than 1 sec/sup -1/. Materials having these properties include hydrogenated and deuterated amorphous semiconductors. A method for preventing the rapid depolarization of a polarized plasma in a fusion device may comprise the step of providing a first-wall or first-wall coating formed of a low-Z, non-metallic material having a depolarization rate greater than 1 sec/sup -1/.

Optimizing soft X-ray NEXAFS spectroscopy in the laboratory

NASA Astrophysics Data System (ADS)

Mantouvalou, I.; Jonas, A.; Witte, K.; Jung, R.; Stiel, H.; Kanngießer, B.

2017-05-01

Near edge X-ray absorption fine structure (NEXAFS) spectroscopy in the soft X-ray range is feasible in the laboratory using laser-produced plasma sources. We present a study using seven different target materials for optimized data analysis. The emission spectra of the materials with atomic numbers ranging from Z = 6 to Z = 79 show distinct differences, rendering the adapted selection of a suitable target material for specialized experiments feasible. For NEXAFS spectroscopy a 112.5 nm thick polyimide film is investigated as a reference exemplifying the superiority of quasi-continuum like emission spectra.

Delamination toughness characterization of out-of-autoclave vacuum-bag-only polymer matrix composites enhanced by z-aligned carbon nanofibers

NASA Astrophysics Data System (ADS)

Brewer, John S.

Brewer, John S., M. S., University of South Alabama, May 2015. Delamination Toughness Characterization of Out-of-Autoclave Vacuum-Bag-Only Polymer Matrix Composites Enhanced by z-aligned Carbon Nanofibers. Chair of Committee: Kuang-Ting Hsiao, Ph.D. In the last few decades, the use of composite materials has revolutionized materials manufacturing. Now, carbon fiber materials are at the forefront of engineering and manufacturing technology. One of the chief failure modes of composite materials is delamination. For this reason, this study employed the Mode-I Interlaminar Fracture Toughness Test (ASTM D 5528-01) to characterize how the inclusion of z-aligned carbon nanofibers (CNF) in Carbon Fiber Reinforced Polymers (CFRP) affects delamination strength. CFRP with z-aligned CNF in concentrations of 0.3% and 0.6% by weight were compared to control CFRP samples and CFRP samples modified with 0.3 weight percent unaligned CNF. The largest improvement was seen in the 0.3 weight percent aligned composite with a mean interlaminar fracture toughness increase of over 35%, while the uncertainty was decreased. A standard deviation of 3.3% was observed which equates to an uncertainty value 30% better than the control samples. Data and microscopy are included and discussed.

Contour mode resonators with acoustic reflectors

DOEpatents

Olsson, Roy H [Albuquerque, NM; Fleming, James G [Albuquerque, NM; Tuck, Melanie R [Albuquerque, NM

2008-06-10

A microelectromechanical (MEM) resonator is disclosed which has a linear or ring-shaped acoustic resonator suspended above a substrate by an acoustic reflector. The acoustic resonator can be formed with a piezoelectric material (e.g. aluminum nitride, zinc oxide or PZT), or using an electrostatically-actuated material. The acoustic reflector (also termed an acoustic mirror) uses alternating sections of a relatively low acoustic impedance Z.sub.L material and a relatively high acoustic impedance Z.sub.H material to isolate the acoustic resonator from the substrate. The MEM resonator, which can be formed on a silicon substrate with conventional CMOS circuitry, has applications for forming oscillators, rf filters, and acoustic sensors.

Ongoing innovations in biomechanics and materials for the new millennium.

PubMed

Kusy, R P

2000-10-01

Material innovations are reviewed within the context of ongoing biomechanical developments that relate the critical contact angle of second-order angulation (theta c) to the overall resistance to sliding (RS). As a science in its embryonic stage of development, RS is partitioned into classical friction (FR), elastic binding (BI), and physical notching (NO). Both FR and BI are defined in terms of normal forces (N) and kinetic coefficients (mu k). The angulation at which NO occurs (theta z) is introduced as a second boundary condition to theta c. Given this scientific backdrop, material modifications are sought that reduce RS. Approaches include minimizing mu k or N within the context of FR and theta < theta c, as, for example, by surface modifications of arch wires and brackets or by engineering novel ligation materials. Stabilizing theta at theta approximately equal theta c should provide more efficient and effective sliding mechanics by developing innovative materials (eg, composites) in which stiffness (EI) varies without changing wire or bracket dimensions. Between the boundaries of theta c and theta z (ie, theta c < theta < theta z), BI may be reduced by decreasing EI or increasing interbracket distance (IBD), independent of whether a conventional or composite material is used.

Laboratory studies of lean combustion

NASA Technical Reports Server (NTRS)

Sawyer, R. F.; Schefer, R. W.; Ganji, A. R.; Daily, J. W.; Pitz, R. W.; Oppenheim, A. K.; Angeli, J. W.

1977-01-01

The fundamental processes controlling lean combustion were observed for better understanding, with particular emphasis on the formation and measurement of gas-phase pollutants, the stability of the combustion process (blowout limits), methods of improving stability, and the application of probe and optical diagnostics for flow field characterization, temperature mapping, and composition measurements. The following areas of investigation are described in detail: (1) axisymmetric, opposed-reacting-jet-stabilized combustor studies; (2) stabilization through heat recirculation; (3) two dimensional combustor studies; and (4) spectroscopic methods. A departure from conventional combustor design to a premixed/prevaporized, lean combustion configuration is attractive for the control of oxides of nitrogen and smoke emissions, the promotion of uniform turbine inlet temperatures, and, possibly, the reduction of carbon monoxide and hydrocarbons at idle.

Synthesis and electrochemical properties of layered Li[Ni 0.333Co 0.333Mn 0.293Al 0.04]O 2- zF z cathode materials prepared by the sol-gel method

NASA Astrophysics Data System (ADS)

Liao, Li; Wang, Xianyou; Luo, Xufang; Wang, Ximing; Gamboa, Sergio; Sebastian, P. J.

The cathode-active materials, layered Li[Ni 0.333Co 0.333Mn 0.293Al 0.04]O 2- zF z (0 ≤ z ≤ 0.1), were synthesized from a sol-gel precursor at 900 °C in air. The influence of Al-F co-substitution on the structural and electrochemical properties of the as-prepared samples was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical experiments. The results showed that Li[Ni 0.333Co 0.333Mn 0.293Al 0.04]O 2- zF z has a typical hexagonal structure with a single phase, the particle sizes of the samples tended to increase with increasing fluorine content. It has been found that Li[Ni 0.333Co 0.333Mn 0.293Al 0.04]O 1.95F 0.05 showed an improved cathodic behavior and discharge capacity retention compared to the undoped samples in the voltage range of 3.0-4.3 V. The electrodes prepared from Li[Ni 0.333Co 0.333Mn 0.293Al 0.04]O 1.95F 0.05 delivered an initial discharge capacity of 158 mAh -1 g and an initial coulombic efficiency is 91.3%, and the capacity retention at the 20th cycle was 94.9%. Though the F-doped samples had lower initial capacities, they showed better cycle performances compared with F-free samples. Therefore, this is a promising material for a lithium-ion battery.

Asphalt dust waste material as a paste volume in developing sustainable self compacting concrete (SCC)

NASA Astrophysics Data System (ADS)

Ismail, Isham; Shahidan, Shahiron; Bahari, Nur Amira Afiza Saiful

2017-12-01

Self-compacting concrete (SCC) mixtures are usually designed to have high workability during the fresh state through the influence of higher volumes of paste in concrete mixtures. Asphalt dust waste (ADW) is one of disposed materials obtained during the production of asphalt premix. These fine powder wastes contribute to environmental problems today. However, these waste materials can be utilized in the development of sustainable and economical SCC. This paper focuses on the preliminary evaluations of the fresh properties and compressive strength of developed SCC for 7 and 28 days only. 144 cube samples from 24 mixtures with varying water binder ratios (0.2, 0.3 and 0.4) and ADW volume (0% to 100%) were prepared. MD940 and MD950 showed a satisfactory performance for the slump flow, J-Ring, L-Box and V-Funnel tests at fresh state. The compressive strength after 28 days for MD940 and MD950 was 36.9 MPa and 28.0 MPa respectively. In conclusion, the use of ADW as paste volume should be limited and a higher water binder ratio will significantly reduce the compressive strength.

Modeling study of deposition locations in the 291-Z plenum

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

Mahoney, L.A.; Glissmeyer, J.A.

The TEMPEST (Trent and Eyler 1991) and PART5 computer codes were used to predict the probable locations of particle deposition in the suction-side plenum of the 291-Z building in the 200 Area of the Hanford Site, the exhaust fan building for the 234-5Z, 236-Z, and 232-Z buildings in the 200 Area of the Hanford Site. The Tempest code provided velocity fields for the airflow through the plenum. These velocity fields were then used with TEMPEST to provide modeling of near-floor particle concentrations without particle sticking (100% resuspension). The same velocity fields were also used with PART5 to provide modeling ofmore » particle deposition with sticking (0% resuspension). Some of the parameters whose importance was tested were particle size, point of injection and exhaust fan configuration.« less

Relative bioavailability of 13C5-folic acid in pectin-coated folate fortified rice in humans using stable isotope techniques.

PubMed

de Ambrosis, A; Vishnumohan, S; Paterson, J; Haber, P; Arcot, J

2017-01-01

The aim of the study was to measure the relative bioavailability of labeled pteroylglutamic acid (13C5-PteGlu) from a pectin-coated fortified rice in vivo to measure any effect of the edible coating on folic acid bioavailability. Healthy volunteers (N=26) aged 18-39 years received three test meals in three randomized short-term cross-over trials: Trial 1: aqueous 400 μg 13C5-PteGlu, Trial 2: 200 g cooked white rice+400 μg 13C5-PteGlu,Trial 3: 200 g fortified cooked white rice with pectin-coated premix containing 400 μg 13C5-PteGlu. Blood samples were drawn at 0,1,2,5 and 8 h postprandial. The concentration of 13C5-5 methyl-tetrahydrofolate appearing in plasma was quantified using high performance liquid chromatography-mass spectrometry (MS)/MS. For 24 h before baseline estimation and during the area under the curve (AUC) study, the subjects were placed on a low folate diet (∼100 μg/day). The relative bioavailability of the folic acid following Trial 3 was measured by comparing the 13C5-5 methyl-tetrahydrofuran (THF) AUC with Trials 1 and 2. The bioavailability of folic acid in a pectin-coated rice premix was 68.7% (range 47-105) and 86.5% (range 65-115) in uncoated fortified rice relative to aqueous folic acid. This study is the first demonstration of the bioavailability of folate in pectin-coated fortified rice in humans.

Quick and selective extraction of Z-ligustilide from Angelica sinensis using magnetic multiwalled carbon nanotubes.

PubMed

Zeng, Qiong; Jia, Yan-Wei; Xu, Pei-Li; Xiao, Meng-Wei; Liu, Yi-Ming; Peng, Shu-Lin; Liao, Xun

2015-12-01

A facile and highly efficient magnetic solid-phase extraction method has been developed for Z-ligustilide, the major therapeutic agent in Angelica sinensis. The solid-phase adsorbent material used was prepared by conjugating carbon nanotubes with magnetic Fe3 O4 nanoparticles via a hydrothermal reaction. The magnetic material showed a high affinity toward Z-ligustilide due to the π-π stacking interaction between the carbon nanotubes and Z-ligustilide, allowing a quick and selective exaction of Z-ligustilide from complex sample matrices. Factors influencing the magnetic solid-phase extraction such as the amount of the added adsorbent, adsorption and desorption time, and desorption solvent, were investigated. Due to its high extraction efficiency, this method was proved highly useful for sample cleanup/enrichment in quantitative high-performance liquid chromatography analysis. The proposed method had a linear calibration curve (R(2) = 0.9983) over the concentration between 4 ng/mL and 200 μg/mL Z-ligustilide. The accuracy of the method was determined by the recovery, which was from 92.07 to 104.02%, with the relative standard deviations >4.51%. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of Mn and Ti substitution on the reflection loss characteristic of Ba{sub 0.6}Sr{sub 0.4}Fe{sub 11-z}MnTi{sub z}O{sub 19} (z = 0, 1, 2 and 3)

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

Gunanto, Y. E., E-mail: yohanes.gunanto@uph.edu; Cahyadi, L., E-mail: lina.cahyadi@uph.edu; Adi, W. Ari, E-mail: dwisnuaa@batan.go.id

2016-04-19

The synthesis and characterization of composition Ba{sub 0.6}Sr{sub 0.4}Fe{sub 11-z}MnTi{sub z}O{sub 19} (z = 0; 1; 2 and 3) compound by solid state reaction using mechanical milling have been performed. The raw materials were BaCO{sub 3}, SrCO{sub 3}, Fe{sub 2}O{sub 3}, MnCO{sub 3}, and TiO{sub 2}. The mixed powder was compacted and sintered at 1000°C for 5 hours. X-ray diffraction studies indicate expansion of hexagonal unit cell and compression of atomic density with substitution of Mn{sup 2+} and Ti{sup 4+} ions. Effect of substitution upon magnetic properties revealed that total magnetization, remanence, and coercivity changed with substitution due to preferentialmore » site occupancy of substituted Mn{sup 2+} and Ti{sup 4+} ions. Since the coercivity and total magnetization may be controlled by substitution while maintaining resistive properties, this material is useful for microwave absorber.« less

Ion Heating of Plasma to Warm Dense Matter Conditions for the study of High-Z/Low-Z Mixing

NASA Astrophysics Data System (ADS)

Roycroft, R.; Dyer, G. M.; McCary, E.; Wagner, C.; Bernstein, A.; Ditmire, T.; Albright, B. J.; Fernandez, J. C.; Bang, W.; Bradley, P. A.; Gautier, D. C.; Hamilton, C. E.; Palaniyappan, S.; Santiago Cordoba, M. A.; Vold, E. L.; Yin, L.; Hegelich, B. M.

2016-10-01

The evolution of the interface between a light and heavy material isochorically heated to warm dense matter conditions is important to the understanding of electrostatic effects on the hydrodynamic models of fluid mixing. In recent experiments at the Trident laser facility, the target, containing a high Z and a low Z material, is heated to around 1eV by laser accelerated aluminum ions. In preparation for continued mixing experiments, we have recently heated aluminum to 20eV by laser accelerated protons on the Texas Petawatt Laser. We fielded a streaked optical pyrometer to measure surface temperature. The pyrometer images the rear surface of a heated target on a sub-nanosecond timescale with 400nm blackbody emissions. This poster presents the details of the experimental setup and pyrometer design, as well as results of ion and proton heating of aluminum targets, and ion heating of high-Z/low-Z integrated targets. Supported by NNSA cooperative agreement DE-NA0002008, the DoE through the LANL LDRD program, the DARPA PULSE program (12-63- PULSE-FP014), and the Air Force Office of Scientific Research (FA9550-14-1-0045).

Effects of Lewis number on the statistics of the invariants of the velocity gradient tensor and local flow topologies in turbulent premixed flames

NASA Astrophysics Data System (ADS)

Wacks, Daniel; Konstantinou, Ilias; Chakraborty, Nilanjan

2018-04-01

The behaviours of the three invariants of the velocity gradient tensor and the resultant local flow topologies in turbulent premixed flames have been analysed using three-dimensional direct numerical simulation data for different values of the characteristic Lewis number ranging from 0.34 to 1.2. The results have been analysed to reveal the statistical behaviours of the invariants and the flow topologies conditional upon the reaction progress variable. The behaviours of the invariants have been explained in terms of the relative strengths of the thermal and mass diffusions, embodied by the influence of the Lewis number on turbulent premixed combustion. Similarly, the behaviours of the flow topologies have been explained in terms not only of the Lewis number but also of the likelihood of the occurrence of individual flow topologies in the different flame regions. Furthermore, the sensitivity of the joint probability density function of the second and third invariants and the joint probability density functions of the mean and Gaussian curvatures to the variation in Lewis number have similarly been examined. Finally, the dependences of the scalar-turbulence interaction term on augmented heat release and of the vortex-stretching term on flame-induced turbulence have been explained in terms of the Lewis number, flow topology and reaction progress variable.

Effects of Lewis number on the statistics of the invariants of the velocity gradient tensor and local flow topologies in turbulent premixed flames

PubMed Central

Konstantinou, Ilias; Chakraborty, Nilanjan

2018-01-01

The behaviours of the three invariants of the velocity gradient tensor and the resultant local flow topologies in turbulent premixed flames have been analysed using three-dimensional direct numerical simulation data for different values of the characteristic Lewis number ranging from 0.34 to 1.2. The results have been analysed to reveal the statistical behaviours of the invariants and the flow topologies conditional upon the reaction progress variable. The behaviours of the invariants have been explained in terms of the relative strengths of the thermal and mass diffusions, embodied by the influence of the Lewis number on turbulent premixed combustion. Similarly, the behaviours of the flow topologies have been explained in terms not only of the Lewis number but also of the likelihood of the occurrence of individual flow topologies in the different flame regions. Furthermore, the sensitivity of the joint probability density function of the second and third invariants and the joint probability density functions of the mean and Gaussian curvatures to the variation in Lewis number have similarly been examined. Finally, the dependences of the scalar--turbulence interaction term on augmented heat release and of the vortex-stretching term on flame-induced turbulence have been explained in terms of the Lewis number, flow topology and reaction progress variable. PMID:29740257

Miller's best/enhanced practices for flour fortification at the flour mill.

PubMed

Johnson, Quentin W; Wesley, Annie S

2010-03-01

Cereal flour fortification has been identified as an effective mass fortification intervention as part of a national public health strategy to overcome micronutrient deficiencies and improve the health status of populations, especially women and children. The effectiveness of cereal flour fortification programs requires the use of micronutrient premixes that provide the desired health benefits. The Miller's Best/Enhanced Practices for Flour Fortification at the flour mill has been developed to provide specific guidance to millers and government officials to ensure that flour fortification practices are carried out in a way that results in the anticipated public health impact. The paper provides information specific to the use of micronutrient premixes, feeders, the fortification process, and quality control systems to ensure that both minimum and enhanced practices can be followed by the millers. Guidelines for basic and best/enhanced practices to be followed for each stage of the flour fortification process at the flour mill are presented. The paper is designed to be a companion to the Recommended Practices for the Production and Procurement of Premix used in Cereal Fortification Programs and supplementary to existing food quality manuals and systems, such as Good Manufacturing Practices, Food Quality Systems, and Hazard Analysis and Critical Control Points. Other stakeholders involved in flour fortification programs have the responsibility to follow best practices of their own to ensure optimum effectiveness.

Effects of gasoline reactivity and ethanol content on boosted premixed and partially stratified low-temperature gasoline combustion (LTGC)

DOE PAGES

Dec, John E.; Yang, Yi; Ji, Chunsheng; ...

2015-04-14

Low-temperature gasoline combustion (LTGC), based on the compression ignition of a premixed or partially premixed dilute charge, can provide thermal efficiencies (TE) and maximum loads comparable to those of turbo-charged diesel engines, and ultra-low NOx and particulate emissions. Intake boosting is key to achieving high loads with dilute combustion, and it also enhances the fuel's autoignition reactivity, reducing the required intake heating or hot residuals. These effects have the advantages of increasing TE and charge density, allowing greater timing retard with good stability, and making the fuel Φ- sensitive so that partial fuel stratification (PFS) can be applied for highermore » loads and further TE improvements. However, at high boost the autoignition reactivity enhancement can become excessive, and substantial amounts of EGR are required to prevent overly advanced combustion. Accordingly, an experimental investigation has been conducted to determine how the tradeoff between the effects of intake boost varies with fuel-type and its impact on load range and TE. Five fuels are investigated: a conventional AKI=87 petroleum-based gasoline (E0), and blends of 10 and 20% ethanol with this gasoline to reduce its reactivity enhancement with boost (E10 and E20). Furthermore, a second zero-ethanol gasoline with AKI=93 (matching that of E20) was also investigated (CF-E0), and some neat ethanol data are also reported.« less

Effect of the superposition of a dielectric barrier discharge onto a premixed gas burner flame

NASA Astrophysics Data System (ADS)

Zaima, Kazunori; Takada, Noriharu; Sasaki, Koichi

2011-10-01

We are investigating combustion control with the help of nonequilibrium plasma. In this work, we examined the effect of dielectric barrier discharge (DBD) on a premixed burner flame with CH4/O2/Ar gas mixture. The premixed burner flame was covered with a quartz tube. A copper electrode was attached on the outside of the quartz tube, and it was connected to a high-voltage power supply. DBD inside the quartz tube was obtained between the copper electrode and the grounded nozzle of the burner which was placed at the bottom of the quartz tube. We clearly observed that the flame length was shortened by superposing DBD onto the bottom part of the flame. The shortened flame length indicates the enhancement of the burning velocity. We measured the optical emission spectra from the bottom region of the flame. As a result, we observed clear line emissions from Ar, which were never observed from the flame without DBD. We evaluated the rotational temperatures of OH and CH radicals by spectral fitting. As a result, the rotational temperature of CH was not changed, and the rotational temperature of OH was decreased by the superposition of DBD. According to these results, it is considered that the enhancement of the burning velocity is not caused by gas heating. New reaction pathways are suggested.

Effect of energetic electrons on combustion of premixed burner flame

NASA Astrophysics Data System (ADS)

Sasaki, Koichi

2011-10-01

In many studies of plasma-assisted combustion, authors superpose discharges onto flames to control combustion reactions. This work is motivated by more fundamental point of view. The standpoint of this work is that flames themselves are already plasmas. We irradiated microwave power onto premixed burner flame with the intention of heating electrons in it. The microwave power was limited below the threshold for a discharge. We obtained the enhancement of burning velocity by the irradiation of the microwave power, which was understood by the shortening of the flame length. At the same time, we observed the increases in the optical emission intensities of OH and CH radicals. Despite the increases in the optical emission intensities, the optical emission spectra of OH and CH were not affected by the microwave irradiation, indicating that the enhancement of the burning velocity was not attributed to the increase in the gas temperature. On the other hand, we observed significant increase in the optical emission intensity of the second positive system of molecular nitrogen, which is a clear evidence for electron heating in the premixed burner flame. Therefore, it is considered that the enhancement of the burning velocity is obtained by nonequilibrium combustion chemistry which is driven by energetic electrons. By irradiating pulsed microwave power, we examined the time constants for the increases and decreases in the optical emission intensities of N2, OH, CH, and continuum radiation.

Annual Research Briefs

NASA Technical Reports Server (NTRS)

Spinks, Debra (Compiler)

1997-01-01

This report contains the 1997 annual progress reports of the research fellows and students supported by the Center for Turbulence Research (CTR). Titles include: Invariant modeling in large-eddy simulation of turbulence; Validation of large-eddy simulation in a plain asymmetric diffuser; Progress in large-eddy simulation of trailing-edge turbulence and aeronautics; Resolution requirements in large-eddy simulations of shear flows; A general theory of discrete filtering for LES in complex geometry; On the use of discrete filters for large eddy simulation; Wall models in large eddy simulation of separated flow; Perspectives for ensemble average LES; Anisotropic grid-based formulas for subgrid-scale models; Some modeling requirements for wall models in large eddy simulation; Numerical simulation of 3D turbulent boundary layers using the V2F model; Accurate modeling of impinging jet heat transfer; Application of turbulence models to high-lift airfoils; Advances in structure-based turbulence modeling; Incorporating realistic chemistry into direct numerical simulations of turbulent non-premixed combustion; Effects of small-scale structure on turbulent mixing; Turbulent premixed combustion in the laminar flamelet and the thin reaction zone regime; Large eddy simulation of combustion instabilities in turbulent premixed burners; On the generation of vorticity at a free-surface; Active control of turbulent channel flow; A generalized framework for robust control in fluid mechanics; Combined immersed-boundary/B-spline methods for simulations of flow in complex geometries; and DNS of shock boundary-layer interaction - preliminary results for compression ramp flow.

Interactions of PAMAM dendrimers with SDS at the solid-liquid interface.

PubMed

Arteta, Marianna Yanez; Eltes, Felix; Campbell, Richard A; Nylander, Tommy

2013-05-14

This work addresses structural and nonequilibrium effects of the interactions between well-defined cationic poly(amidoamine) PAMAM dendrimers of generations 4 and 8 and the anionic surfactant sodium dodecyl sulfate (SDS) at the hydrophilic silica-water interface. Neutron reflectometry and quartz crystal microbalance with dissipation monitoring were used to reveal the adsorption from premixed dendrimer/surfactant solutions as well as sequential addition of the surfactant to preadsorbed layers of dendrimers. PAMAM dendrimers of both generations adsorb to hydrophilic silica as a compact monolayer, and the adsorption is irreversible upon rinsing with salt solution. SDS adsorbs on the dendrimer layer and at low bulk concentrations causes the expansion of the dendrimer layers on the surface. When the bulk concentration of SDS is increased, the surfactant layer consists of aggregates or bilayer-like structures. The adsorption of surfactant is reversible upon rinsing, but slight changes of the structure of the preadsorbed PAMAM monolayer were observed. The adsorption from premixed solutions close to charge neutrality results in thick multilayers, but the surface excess is lower when the bulk complexes have a net negative charge. A critical examination of the pathway of adsorption for the interactions of SDS with preadsorbed PAMAM monolayers and premixed PAMAM/SDS solutions with hydrophilic silica revealed that nonequilibrium effects are important only in the latter case, and the application of a thermodynamic model to such experimental data would be inappropriate.

The effects of complex chemistry on triple flames

NASA Technical Reports Server (NTRS)

Echekki, T.; Chen, J. H.

1996-01-01

The structure, ignition, and stabilization mechanisms for a methanol (CH3OH)-air triple flame are studied using Direct Numerical Simulations (DNS). The methanol (CH3OH)-air triple flame is found to burn with an asymmetric shape due to the different chemical and transport processes characterizing the mixture. The excess fuel, methanol (CH3OH), on the rich premixed flame branch is replaced by more stable fuels CO and H2, which burn at the diffusion flame. On the lean premixed flame side, a higher concentration of O2 leaks through to the diffusion flame. The general structure of the triple point features the contribution of both differential diffusion of radicals and heat. A mixture fraction-temperature phase plane description of the triple flame structure is proposed to highlight some interesting features in partially premixed combustion. The effects of differential diffusion at the triple point add to the contribution of hydrodynamic effects in the stabilization of the triple flame. Differential diffusion effects are measured using two methods: a direct computation using diffusion velocities and an indirect computation based on the difference between the normalized mixture fractions of C and H. The mixture fraction approach does not clearly identify the effects of differential diffusion, in particular at the curved triple point, because of ambiguities in the contribution of carbon and hydrogen atoms' carrying species.

Electrical Characteristics, Electrode Sheath and Contamination Layer Behavior of a Meso-Scale Premixed Methane-Air Flame Under AC/DC Electric Fields

NASA Astrophysics Data System (ADS)

Chen, Qi; Yan, Limin; Zhang, Hao; Li, Guoxiu

2016-05-01

Electrical characteristics of a nozzle-attached meso-scale premixed methane-air flame under low-frequency AC (0-4300 V, 0-500 Hz) and DC (0-3300 V) electric fields were studied. I-V curves were measured under different experimental conditions to estimate the magnitude of the total current 100-102 μA, the electron density 1015-1016 m-3 and further the power dissipation ≤ 0.7 W in the reaction zone. At the same time, the meso-scale premixed flame conductivity 10-4-10-3 Ω-1·m-1 as a function of voltage and frequency was experimentally obtained and was believed to represent a useful order-of magnitude estimate. Moreover, the influence of the collision sheath relating to Debye length (31-98 μm) and the contamination layer of an active electrode on measurements was discussed, based on the combination of simulation and theoretical analysis. As a result, the electrode sheath dimension was evaluated to less than 0.5 mm, which indicated a complex effect of the collision sheath on the current measurements. The surface contamination effect of an active electrode was further analyzed using the SEM imaging method, which showed elements immigration during the contamination layer formation process. supported by National Natural Science Foundation of China (No. 51376021), and the Fundamental Research Fund for Major Universities (No. 2013JBM079)

Wide range scaling laws for radiation driven shock speed, wall albedo and ablation parameters for high-Z materials

NASA Astrophysics Data System (ADS)

Mishra, Gaurav; Ghosh, Karabi; Ray, Aditi; Gupta, N. K.

2018-06-01

Radiation hydrodynamic (RHD) simulations for four different potential high-Z hohlraum materials, namely Tungsten (W), Gold (Au), Lead (Pb), and Uranium (U) are performed in order to investigate their performance with respect to x-ray absorption, re-emission and ablation properties, when irradiated by constant temperature drives. A universal functional form is derived for estimating time dependent wall albedo for high-Z materials. Among the high-Z materials studied, it is observed that for a fixed simulation time the albedo is maximum for Au below 250 eV, whereas it is maximum for U above 250 eV. New scaling laws for shock speed vs drive temperature, applicable over a wide temperature range of 100 eV to 500 eV, are proposed based on the physics of x-ray driven stationary ablation. The resulting scaling relation for a reference material Aluminium (Al), shows good agreement with that of Kauffman's power law for temperatures ranging from 100 eV to 275 eV. New scaling relations are also obtained for temperature dependent mass ablation rate and ablation pressure, through RHD simulation. Finally, our study reveals that for temperatures above 250 eV, U serves as a better hohlraum material since it offers maximum re-emission for x-rays along with comparable mass ablation rate. Nevertheless, traditional choice, Au works well for temperatures below 250 eV. Besides inertial confinement fusion (ICF), the new scaling relations may find its application in view-factor codes, which generally ignore atomic physics calculations of opacities and emissivities, details of laser-plasma interaction and hydrodynamic motions.

The Effect of Material Removal on the Corrosion Resistance and Biocompatibility of Nitinol Laser-Cut and Wire-Form Products

NASA Astrophysics Data System (ADS)

Decker, Jennifer Fino; Trépanier, Christine; Vien, Lot; Pelton, Alan R.

2011-07-01

Laser cutting and wire forming are two of the most commonly used processes in the manufacture of Nitinol medical devices. This study explores how varying the amount of material removed during the final surface treatment steps affects the corrosion resistance of Z-type stents that have either been laser-cut from tube or shape set from wire. All parts were subjected to a typical heat treatment process necessary to achieve an Austenite finish (Af) temperature of 25 ± 5 °C, and were subsequently post-processed with an electrochemical passivation process. The total weight loss during post-processing was recorded and the process adjusted to create groups with less than 5%, less than 10%, and less than 25% amounts of weight loss. The parts were then crimped to 6 mm and allowed to expand back to their original diameter. The corrosion test results showed that on average both groups of Z-stents experienced an increase in the corrosion breakdown potential and a decrease in the standard deviation with increasing amounts of material removal. In addition, less material removal is required from the wire-form Z-stents as compared to the laser-cut Z-stents to achieve high corrosion resistance. Finally, 7 day nickel ion release tests performed on the wire-formed Z-stents showed a dramatic decrease from 0.0132 mg of nickel leached per day for the low weight loss group to approximately 0.001 mg/day for the medium and high weight loss groups.

An abstraction layer for efficient memory management of tabulated chemistry and flamelet solutions

NASA Astrophysics Data System (ADS)

Weise, Steffen; Messig, Danny; Meyer, Bernd; Hasse, Christian

2013-06-01

A large number of methods for simulating reactive flows exist, some of them, for example, directly use detailed chemical kinetics or use precomputed and tabulated flame solutions. Both approaches couple the research fields computational fluid dynamics and chemistry tightly together using either an online or offline approach to solve the chemistry domain. The offline approach usually involves a method of generating databases or so-called Lookup-Tables (LUTs). As these LUTs are extended to not only contain material properties but interactions between chemistry and turbulent flow, the number of parameters and thus dimensions increases. Given a reasonable discretisation, file sizes can increase drastically. The main goal of this work is to provide methods that handle large database files efficiently. A Memory Abstraction Layer (MAL) has been developed that handles requested LUT entries efficiently by splitting the database file into several smaller blocks. It keeps the total memory usage at a minimum using thin allocation methods and compression to minimise filesystem operations. The MAL has been evaluated using three different test cases. The first rather generic one is a sequential reading operation on an LUT to evaluate the runtime behaviour as well as the memory consumption of the MAL. The second test case is a simulation of a non-premixed turbulent flame, the so-called HM1 flame, which is a well-known test case in the turbulent combustion community. The third test case is a simulation of a non-premixed laminar flame as described by McEnally in 1996 and Bennett in 2000. Using the previously developed solver 'flameletFoam' in conjunction with the MAL, memory consumption and the performance penalty introduced were studied. The total memory used while running a parallel simulation was reduced significantly while the CPU time overhead associated with the MAL remained low.

High density laser-driven target

DOEpatents

Lindl, John D.

1981-01-01

A high density target for implosion by laser energy composed of a central quantity of fuel surrounded by a high-Z pusher shell with a low-Z ablator-pusher shell spaced therefrom forming a region filled with low-density material.

Thrust Chamber Material Technology Program

DTIC Science & Technology

1989-03-01

about 5 percent lower than those of NASA.Z. Alloy 1035 was essentially equivalent to NASA-Z. However, Alloy 1032, containing titanium, exhibited such...Characterization Methods .................................... 33 5 Evaluation Methods ......................................................... 37 III...115 5 Discussion ..................................................................... 120 V ALLOY CHARACTERIZATION

Face Centered Cubic SnSe as a Z2 Trivial Dirac Nodal Line Material

NASA Astrophysics Data System (ADS)

Tateishi, Ikuma; Matsuura, Hiroyasu

2018-07-01

The presence of a Dirac nodal line in a time-reversal and inversion symmetric system is dictated by the Z2 index when spin-orbit interaction is absent. In a first principles calculation, we show that a Dirac nodal line can emerge in Z2 trivial material by calculating the band structure of SnSe in a face centered cubic lattice as an example. We qualitatively show that it becomes a topological crystalline insulator when spin-orbit interaction is taken into account. We clarify the origin of the Dirac nodal line by obtaining irreducible representations corresponding to bands and explain the triviality of the Z2 index. We construct an effective model representing the Dirac nodal line using the k · p method, and discuss the Berry phase and a surface state expected from the Dirac nodal line.

Layered cathode materials for lithium ion rechargeable batteries

DOEpatents

Kang, Sun-Ho [Naperville, IL; Amine, Khalil [Downers Grove, IL

2007-04-17

A number of materials with the composition Li.sub.1+xNi.sub..alpha.Mn.sub..beta.Co.sub..gamma.M'.sub..delta.O.sub.2-- zF.sub.z (M'=Mg,Zn,Al,Ga,B,Zr,Ti) for use with rechargeable batteries, wherein x is between about 0 and 0.3, .alpha. is between about 0.2 and 0.6, .beta. is between about 0.2 and 0.6, .gamma. is between about 0 and 0.3, .delta. is between about 0 and 0.15, and z is between about 0 and 0.2. Adding the above metal and fluorine dopants affects capacity, impedance, and stability of the layered oxide structure during electrochemical cycling.