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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Stainless Steel NaK-Cooled Circuit (SNaKC) Fabrication and Assembly

An actively pumped Stainless Steel NaK Circuit (SNaKC) has been designed and fabricated by the Early Flight Fission Test Facility (EFF-TF) team at NASA's Marshall Space Flight Center. This circuit uses the eutectic mixture of sodium and potassium (NaK) as the working fluid building upon the experience and accomplishments of the SNAP reactor program from the late 1960's The SNaKC enables valuable experience and liquid metal test capability to be gained toward the goal of designing and building an affordable surface power reactor. The basic circuit components include a simulated reactor core a NaK to gas heat exchanger, an electromagnetic (EM) liquid metal pump, a liquid metal flow meter, an expansion reservoir and a drain/fill reservoir To maintain an oxygen free environment in the presence of NaK, an argon system is utilized. A helium and nitrogen system are utilized for core, pump, and heat exchanger operation. An additional rest section is available to enable special component testing m an elevated temperature actively pumped liquid metal environment. This paper summarizes the physical build of the SNaKC the gas and pressurization systems, vacuum systems, as well as instrumentation and control methods.

Godfroy, Thomas J.↗
DOE OSTI2019

Ring opening of cycloalkanes at high temperatures

Cycloalkanes are an important fraction of molecules in real fuels and their pyrolysis products can be crucial during the combustion process. However, there have been few studies on the dissociation of these molecules apart from cyclohexane. We present here a laser schlieren densitometry study on cycloheptane pyrolysis as part of a study of the effect of ring size on dissociation of cycloalkanes. The experiments were performed in a diaphragmless shock tube with a 2% cycloheptane/98% krypton mixture and reaction conditions of 1400 – 2200 K and 30 – 110 Torr. Complementary investigations of the dissociation of the conjugate 1-alkene, 1-heptene (the initial pyrolysis product), have also been conducted to aid development of a chemical kinetic mechanism. A common aspect to dissociation of cycloalkanes is that at high temperatures they are efficiently converted to an allyl radical and an n-alkyl radical and the reactions of these radicals dominate the secondary chemistry. The newly developed model, which incorporates results from recent shock tube/laser schlieren studies of the n-butyl radical, is presented herein along with experimental results from cycloheptane and 1-heptene results. Good agreement between simulations and the experimental profiles were obtained allowing kinetic data to be extracted.

Chemical kinetics↗
DOE OSTI2019

MINERALOGICAL AND TEXTURAL CONTROLS ON SHEAR STRENGTH, SLIP STABILITY AND PERMEABILITY OF FAULTS

Induced seismicity resulting from fluid injection into the subsurface related to water and CO2 disposal, hydraulic fracturing and the stimulation of geothermal reservoirs present an important societal concern. These human activities involve the injection of large volumes of pressurized fluid into the subsurface, potentially at high rates, raising local pore pressures and disturbing the pristine local stress regime by lowering effective normal stress on pre-existing faults and fractures. The reduction of effective normal stress may trigger fault/fracture reactivation and in some cases result in hazardous seismic ruptures. Effective management and engineering of anthropogenic seismic events requires substantial understanding in the mechanisms, especially for the controlling factors on coupled rheological and transport response, including fault shear strength, slip stability, and permeability evolution during such events. In this study, we explore the coupled rheological and transport response of faults and fractures during reactivation as controlled by two fundamental controlling properties, viz., mineralogy and textural features. We approach this problem through shear experiments on analog faults and fractures via laboratory and numerical experiments. Specifically, we investigate: (1) the influence of frictionally weak minerals (talc) in mixtures of mineral analogs featuring contrasting frictional properties, (2) the influence of iron oxide grain coatings on quartz aggregates, and (3) the influence of fracture roughness in mated fractures on the ensemble shear strength, slip stability, and permeability evolution during reactivation events. We address the following questions in this study: (1) how much and what distribution of frictionally weak minerals is required to induce significant weakening in faults consisting of a matrix of frictionally strong minerals, (2) how does a pre-imposed weak mineral layer influence the rheological and transport behavior of faults, (3) what is the influence of a trace amount of grain coating materials introduce on the coupled behavior of faults, and finally (4) how do asperity height and wave length control the ensemble behavior of faults. These questions are explicitly answered in the following.

58 GEOSCIENCES↗
DOE OSTI2020

The rate of development of atomic mixing and temperature equilibration in inertial confinement fusion implosions

The MARBLE project is a novel inertial confinement fusion platform for studying the development of atomic mixing and temperature equilibration in inertial confinement fusion implosions and their impact on thermonuclear burn. Experiments involve the laser-driven implosion of capsules filled with deuterated engineered foams whose pores are filled with a gaseous mixture of hydrogen and tritium. By varying the size of the foam pores, we can study the timescale of the development of atomic mix relative to the development of thermal equilibrium between species. In contrast, previous separated reactant experiments have only provided information on the total amount of mix mass. Additionally, we report on the series of MARBLE experiments [first reported in Haines et al., Nat. Commun. 11, 544 (2020)] performed on the University of Rochester's OMEGA laser facility and detailed and highly resolved three-dimensional radiation-hydrodynamic simulations of the implosions. In both the experimental and simulation results, we observe that the reactants do not achieve thermal equilibrium during the course of the implosion except in atomically mixed regions—i.e., that atomic mixing develops faster than thermal equilibration between species. The results suggest that ion temperature variations in the mixture are at least as important as reactant concentration variations for determining the fusion reaction rates.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Radiation and Thermal Stability of Solid Radwaste After Immobilization in Polymer Matrix - 13504

The paper will illustrate results of the various experiments on radiation and thermal stability of polymer matrixes after solutions solidification including aqueous and organic solutions and mixed waste. It was shown that- after irradiation the specimen and after solidification the mixture with oil and TBP hydrogen has been observed (less 1%) and some others gases have been detected. Results of the performed experiments and the radiation stability data of the polymer compositions allow the conclusion that the technological process of immobilizing the above mentioned aqueous solutions and solutions with organic products into polymers at room temperature is the explosion- and flameproof as well as the storage thereof. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Thermodiffusion in concentrated ferrofluids: A review and current experimental and numerical results on non-magnetic thermodiffusion

Ferrofluids are colloidal suspensions consisting of magnetic nanoparticles dispersed in a carrier liquid. Their thermodiffusive behaviour is rather strong compared to molecular binary mixtures, leading to a Soret coefficient (S{sub T}) of 0.16 K{sup −1}. Former experiments with dilute magnetic fluids have been done with thermogravitational columns or horizontal thermodiffusion cells by different research groups. Considering the horizontal thermodiffusion cell, a former analytical approach has been used to solve the phenomenological diffusion equation in one dimension assuming a constant concentration gradient over the cell's height. The current experimental work is based on the horizontal separation cell and emphasises the comparison of the concentration development in different concentrated magnetic fluids and at different temperature gradients. The ferrofluid investigated is the kerosene-based EMG905 (Ferrotec) to be compared with the APG513A (Ferrotec), both containing magnetite nanoparticles. The experiments prove that the separation process linearly depends on the temperature gradient and that a constant concentration gradient develops in the setup due to the separation. Analytical one dimensional and numerical three dimensional approaches to solve the diffusion equation are derived to be compared with the solution used so far for dilute fluids to see if formerly made assumptions also hold for higher concentrated fluids. Both, the analytical and numerical solutions, either in a phenomenological or a thermodynamic description, are able to reproduce the separation signal gained from the experiments. The Soret coefficient can then be determined to 0.184 K{sup −1} in the analytical case and 0.29 K{sup −1} in the numerical case. Former theoretical approaches for dilute magnetic fluids underestimate the strength of the separation in the case of a concentrated ferrofluid.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2011

New Insights into Prebiotic Chemistry from Old Archived Miller Extracts

Following the discovery of an archived set of samples from Stanley Miller's early experiments, analyses were undertaken to better understand the diversity of compounds produced from electric discharges acting on reducing gas mixtures. The paper chromatography methods that Miller used in the 1950s were only capable of detecting a few amino acids and were unable to provide substantial quantitative data relative to today's techniques. Current analytical techniques are much more sensitive and selective, and are capable of precisely quantifying a much larger range of amino acids and their enantiomeric abundances. In one study, preserved dried samples produced by Miller using a lesser-known volcanic apparatus which differed from Miller's classic apparatus in that it utilized an aspirator that injected steam into the electric discharge chamber, simulating a volcanic eruption. The volcanic apparatus produced a wider variety of amino acids than the classic configuration. Prebiotic compounds synthesized in these environments may have locally accumulated where they could have undergone further processing. An additional preserved set of samples from an experiment conducted in 1958 were also found in Miller's archived collection. These samples which had been generated using a mixture of CH4, NH3, H2S and CO2 were collected, catalogued, and stored by Miller, but for unknown reasons were never studied. In our analyses a total of 23 amino acids and 4 amines, including 7 organosulfur compounds, were detected in these samples. The major amino acids with chiral centers are racemic within the accuracy of the measurements, indicating that they are not contaminants introduced during sample storage. This experiment marks the first synthesis of sulfur amino acids from spark discharge experiments designed to imitate primordial environments. The relative yield of some amino acids, in particular the isomers of amino butyric acid, are the highest ever found in a spark discharge experiment. The simulated primordial conditions used by Miller in these experiments may serve as a model for early volcanic plume chemistry and provide insight to the possible roles such plumes may have played in abiotic organic synthesis. Additionally, the overall abundances of the synthesized amino acids in the presence of H2S are very similar to the abundances found in some carbonaceous meteorites, suggesting that H2S may have played an important role in prebiotic reactions in early solar system environments. Although experiments using a variety of gases as components of the primordial Earth's atmospheric composition and a spark discharge apparatus configured according to Miller's original or volcanic design can be readily carried out, the unique opportunity to investigate samples prepared by the pioneer in abiotic synthesis using state of the art analytical methods is of considerable historic interest.

Parker, Eric T.↗
DOE OSTI2016

Large Eddy Simulation of Autoignition Transients in a Model Diesel Injector Configuration

Developing an improved understanding of transient mixing and combustion processes inherent in diesel injection is an important element in the design of advanced engines. This paper provides a detailed analysis of these processes using an idealized benchmark configuration designed to facilitate precise comparisons between different models and numerical methods. The computational domain is similar to the Engine Combustion Network (www.sandia.gov/ECN) Spray-A injector with n-dodecane as the fuel. Quantified idealizations are made in the treatment of boundary conditions to eliminate ambiguities and unknowns associated with the actual injector(s) used in the experiment. These ambiguities hinder comparisons aimed at understanding the accuracy of different models and the coupled effects of potential numerical errors. Prior to understanding the impact of injector imperfections on their performance, it is first necessary to understand how models perform in a well-controlled environment with well-defined boundary conditions. Here, we focus on the latter while accurately matching the operating conditions used in the experiments. Relevant high-pressure phenomena are treated with real-fluid thermodynamics and transport for multicomponent mixtures. A highly resolved calculation is performed to study both scalar-mixing and initiation of combustion. Results are assembled into a database that can facilitate one-to-one comparisons between codes. The combined set of results is analyzed to provide physical insights related to localized broadband transient mixing and combustion processes that are typically not available from experiments.

Hakim, Layal↗
DOE OSTI2024

Summary of Gas Generation Behavior Observed in 3013 Surveillance and Monitoring Program Shelf-Life Experiments

Gas generation experiments have been conducted in small- and full-scale test containers at Los Alamos National Laboratory on samples of plutonium oxide material collected from plutonium processes across the DOE complex and tested at the bounding conditions for the Department of Energy 3013 Standard. The gas composition and pressures in the sealed experimental containers were measured over periods of months to years. These experiments have provided results for the formation and consumption of hydrogen and other gases. The conditions supporting the formation of flammable gas mixtures of hydrogen and oxygen in flammable gas mixtures were also determined. Different behaviors were observed between the materials tested based on their compositions, the stabilization performed on the material, and the post stabilization handling of the material. Many of the experiments are still ongoing. This report summarizes the results obtained for the gas generation behavior for high-purity plutonium oxides and salt-bearing impure plutonium oxides in sealed containers.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2013

Membrane formation by preferential solvation of ions in mixture of water, 3-methylpyridine, and sodium tetraphenylborate

The structure and dynamics of a ternary system composed of deuterium oxide (D{sub 2}O), 3-methylpyridine (3MP), and sodium tetraphenylborate (NaBPh{sub 4}) are investigated by means of small-angle neutron scattering (SANS) and neutron spin echo (NSE) techniques. In the SANS experiments, a structural phase transition is confirmed between a disordered-phase and an ordered-lamellar-phase upon variation of the composition and/or temperature of the mixture. The characteristic lengths of the structures is on the sub-micrometer scale. A dispersion relation of the structure is measured through NSE experiments, which shows that the relaxation rate follows a cubic relation with momentum transfer. This implies that the dynamics of the system are determined predominantly by membrane fluctuations. The present results indicate that 3MP-rich domains are microscopically separated from bulk water in the presence of NaBPh{sub 4}, and that the layers behave as membranes. These results are interpreted that preferential solvation of salt in each solvent induces a microphase separation between the solvents, and the periodic structure of 3MP-rich domains is stabilized by the long-range electrostatic interaction arising from Na{sup +} ions in D{sub 2}O-rich domains.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2011

Effect of Water on the Thermo-Mechanical Behavior of Carbon Cloth Phenolic

The results of thermo-mechanical experiments, which were conducted previously by one of the authors, are reviewed. The strain in the direction normal to the fabric plane was measured as a function of temperature for a variety of initial moisture contents and heating rates. In this paper, the general features of the thermo-mechanical response are discussed and the effect of heating rate and initial moisture content are highlighted. The mechanical interaction between the phenolic polymer and water trapped within its free volumes as the polymer is heated to high temperatures is discussed. An equation for the internal stresses which are generated within the polymer due to trapped water is obtained from the total stress expression for a binary mixture of polymer and water. Numerical solutions for moisture diffusion in the thermo-mechanical experiments were performed and the results of these solutions are presented. The results of the moisture diffusion solutions help to explain the effects of heating rate and moisture content on the strain behavior normal to the fabric plane.

Sullivan, Roy M.↗
DOE OSTI2015

Ethane-xenon mixtures under shock conditions

Mixtures of light elements with heavy elements are important in inertial confinement fusion. We explore the physics of molecular scale mixing through a validation study of equation of state (EOS) properties. Density functional theory molecular dynamics (DFT-MD) at elevated temperature and pressure is used to obtain the thermodynamic state properties of pure xenon, ethane, and various compressed mixture compositions along their principal Hugoniots. In order to validate these simulations, we have performed shock compression experiments using the Sandia Z-Machine. A bond tracking analysis correlates the sharp rise in the Hugoniot curve with the completion of dissociation in ethane. Furthermore, the DFT-based simulation results compare well with the experimental data along the principal Hugoniots and are used to provide insight into the dissociation and temperature along the Hugoniots as a function of mixture composition. Interestingly, we find that the compression ratio for complete dissociation is similar for several compositions suggesting a limiting compression for C-C bonded systems.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Surface soil temperature and water content from warming experiment located at the Rocky Mountain Biological Laboratory, Colorado, 2015 to 2019

This data package consists of soil temperature and soil water content sensor data from the warming experiment near the Rocky Mountain Biological Laboratory. Data range is from summer 2015 to summer 2019, when the warming manipulation was terminated. The location of the warming experiment is in the upper montane life zone and consists of meadow vegetation with a mixture of sagebrush (Artemisia tridentata), forb species (Erigeron speciosus, Helianthella quinquenervis, Lathyrus lanszwertii), and graminoid species (Festuca thurberi, Carex spps). Early studies showed that the heating treatment led to earlier snowmelt as well as warmer and drier surface soils, and changes in the functional composition of aboveground biomass favoring sagebrush over forb species (Harte and Shaw, 1995). These changes were mainly observed in the upper, naturally drier zone for the experimental plots. More recent observations of aboveground biomass, soil carbon, and microbial composition require concurrent information about the abiotic environment for interpretation and extrapolation to process-based models. This data package provides the plot- and zone-level abiotic context for the final years of the experiment and consists of csv files with hourly soil temperature (WM_ST.csv) and soil water content (WM_SWC.csv).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1982

A blackbody radiation-pumped CO2 laser experiment

Thermal radiation from a high temperature oven was used as an optical pump to achieve lasing from CO2 mixtures. Laser output as a function of blackbody temperature and gas conditions is described. This achievement represents the first blackbody cavity pumped laser and has potential for solar pumping.

Christiansen, W. H.↗
NASA NTRS1983

Blackbody-pumped CO2 laser experiment

Thermal radiation from a high temperature oven was used as an optical pump to achieve lasing from CO2 mixtures. Laser output as a function of blackbody temperature and gas conditions is described. This achievement represents the first blackbody cavity pumped laser and has potential for solar pumping. Previously announced in STAR as N83-10420

Christiansen, W. H.↗
NASA NTRS1947

The Effect of Turbulence on the Flame Velocity in Gas Mixtures

The present report deals with the effect of turbulence on the propagation of the flame. Being based upon experiments with laminar as well as turbulent Bunsen flames, both the physico-chemical and the hydro-dynamical aspects of the problem are analyzed. A number of new deductions, interesting from the point of view of engine combustion and other very rapidly changing flame reactions, are made.

Gerhard Damkoehler↗
DOE OSTI2019

Hyperspectral imaging of minerals in the longwave infrared: the use of laboratory directional-hemispherical reference measurements for field exploration data

Hyperspectral Imaging (HSI) continues to grow as a method for remote detection of vegetation, materials, minerals, and pure chemicals. We have used a longwave infrared (7.7 - 11.8 µm) imaging spectrometer in a static outdoor experiment to collect HSI data from 24 minerals and background materials to determine the efficacy with which HSI can remotely detect and distinguish both pure minerals and mineral mixtures at three solar angles (25°, 35°, and 45° relative to ground) as well as varying backgrounds and other sample effects. Measurements were obtained separately for the minerals and materials mounted directly both on a bare plywood board and a plywood board coated with aluminum foil: 19 powders (3 mixtures and 16 pure mineral powders) held in polyethylene bottle lids as well as 5 samples in rock form were taped directly to the boards. The primary goal of the experiment was to demonstrate that a longwave infrared (LWIR) library of solids and minerals collected as directional-hemispherical reflectance spectra in the laboratory can be used directly for HSI field identification. Prior to the experiment, all 24 mineral/inorganic samples were measured in the laboratory using a Fourier transform infrared spectrometer (FTIR) equipped with a gold-coated IR integrating sphere; the spectra were assimilated as part of a larger reference library of 21 pure minerals, 3 mixtures, and the polyethylene lid. Principal components analysis (PCA) with mean-centering was used in an exploratory analysis of the HSI images and showed that for the aluminum coated board, the first principal component captured the difference between signal that resembled a blackbody and the highly reflective aluminum background. In contrast, principal components PC 2, 3, and 4 were able to discriminate the materials including phosphates, sulfates, silicates, carbonates, and the mixtures. Results from generalized least squares target detection clearly showed that laboratory reference spectra of minerals could be utilized as targets with high fidelity for field detection, both for pure and mixed samples.

47 OTHER INSTRUMENTATION↗