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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Electrical and magnetic properties of spherical SmFeO{sub 3} synthesized by aspartic acid assisted combustion method

Highlights: • SmFeO{sub 3} is synthesized by simple combustion method using aspartic acid as the fuel. • The particles are spherical in shape with the size ranges between 150 and 300 nm. • Cole–Cole plot infers the bulk conduction mechanism. • Room temperature VSM analysis reveal the weak ferromagnetic behaviour of SmFeO{sub 3}. • Mössbauer analysis elucidates the +3 oxidation state of Fe atoms. - Abstract: Samarium orthoferrite (SmFeO{sub 3}) is synthesized by a simple combustion method using aspartic acid as fuel. Phase purity and functional groups are analyzed via X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) analysis, which confirms the single phase formation of orthorhombic SmFeO{sub 3}. Approximately spherical particles with size range 150–300 nm is revealed by scanning electron microscope (SEM). The conductivity of the material is identified by the single semicircle obtained in the solid state impedance spectra at elevated temperatures. The calculated electrical conductivity increases with increasing temperature, inferring the semiconducting nature of SmFeO{sub 3}. A magnetic study at room temperature revealed weak ferromagnetic behaviour in SmFeO{sub 3} due to Dzyaloshinsky–Moriya antisymmetric exchange interaction mechanism. Mössbauer analysis confirmed the +3 oxidation state of iron and magnetic ordering of the sample at room temperature.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Characteristics and combustion of future hydrocarbon fuels

As the world supply of petroleum crude oil is being depleted, the supply of high-quality crude oil is also dwindling. This dwindling supply is beginning to manifest itself in the form of crude oils containing higher percentages of aromatic compounds, sulphur, nitrogen, and trace constituents. The result of this trend is described and the change in important crude oil characteristics, as related to aircraft fuels, is discussed. As available petroleum is further depleted, the use of synthetic crude oils (those derived from coal and oil shale) may be required. The principal properties of these syncrudes and the fuels that can be derived from them are described. In addition to the changes in the supply of crude oil, increasing competition for middle-distillate fuels may require that specifications be broadened in future fuels. The impact that the resultant potential changes in fuel properties may have on combustion and thermal stability characteristics is illustrated and discussed in terms of ignition, soot formation, carbon deposition flame radiation, and emissions.

Rudey, R. A.↗
NASA NTRS2003

High-Pressure Transport Properties Of Fluids: Theory And Data From Levitated Drops At Combustion-Relevant Temperatures

Although the high pressure multicomponent fluid conservation equations have already been derived and approximately validated for binary mixtures by this PI, the validation of the multicomponent theory is hampered by the lack of existing mixing rules for property calculations. Classical gas dynamics theory can provide property mixing-rules at low pressures exclusively. While thermal conductivity and viscosity high-pressure mixing rules have been documented in the literature, there is no such equivalent for the diffusion coefficients and the thermal diffusion factors. The primary goal of this investigation is to extend the low pressure mixing rule theory to high pressures and validate the new theory with experimental data from levitated single drops. The two properties that will be addressed are the diffusion coefficients and the thermal diffusion factors. To validate/determine the property calculations, ground-based experiments from levitated drops are being conducted.

Bellan, Josette↗
NASA NTRS1991

Three-Dimensional Analysis and Modeling of a Wankel Engine

A new computer code, AGNI-3D, has been developed for the modeling of combustion, spray, and flow properties in a stratified-charge rotary engine (SCRE). The mathematical and numerical details of the new code are described by the first author in a separate NASA publication. The solution procedure is based on an Eulerian-Lagrangian approach where the unsteady, three-dimensional Navier-Stokes equations for a perfect gas-mixture with variable properties are solved in generalized, Eulerian coordinates on a moving grid by making use of an implicit finite-volume, Steger-Warming flux vector splitting scheme. The liquid-phase equations are solved in Lagrangian coordinates. The engine configuration studied was similar to existing rotary engine flow-visualization and hot-firing test rigs. The results of limited test cases indicate a good degree of qualitative agreement between the predicted and measured pressures. It is conjectured that the impulsive nature of the torque generated by the observed pressure nonuniformity may be one of the mechanisms responsible for the excessive wear of the timing gears observed during the early stages of the rotary combustion engine (RCE) development. It was identified that the turbulence intensities near top-dead-center were dominated by the compression process and only slightly influenced by the intake and exhaust processes. Slow mixing resulting from small turbulence intensities within the rotor pocket and also from a lack of formation of any significant recirculation regions within the rotor pocket were identified as the major factors leading to incomplete combustion. Detailed flowfield results during exhaust and intake, fuel injection, fuel vaporization, combustion, mixing and expansion processes are also presented. The numerical procedure is very efficient as it takes 7 to 10 CPU hours on a CRAY Y-MP for one entire engine cycle when the computations are performed over a 31 x16 x 20 grid.

Raju, M. S.↗
DOE OSTI2018

Effect of Nd Substitution on Properties of Multiferroic Bismuth Ferrite Synthesized by Sol-Gel Auto-combustion Method

In this work, pure and Nd-doped bismuth ferrite nanocrystals with the general formula of Bi{sub 1−x}Nd{sub x}FeO{sub 3} (x = 0, 0.05, 0.1, 0.15, 0.2) were synthesized via the sol-gel auto-combustion method at two different calcination temperatures (550 and 650{sup ∘}C). Phase analysis and investigating structural, thermal, and magnetic properties and measuring the size of nanoparticles have been done by using X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG/DTA), and vibrating sample magnetometry (VSM). For undoped BiFeO{sub 3} (BFO), increasing calcination temperature will increase the average size of nanocrystals. On the other hand, the average size of nanoparticles is decreased by increasing the concentration of neodymium in the structure of BFO. By entering neodymium to the structure of bismuth ferrite at the calcination temperature of 550{sup ∘}C, the ferromagnetic properties decline. However, at 650{sup ∘}C, ferromagnetic properties are improved which is due to a fall in the number of Fe{sup 2+} ions. In this case, by decreasing the Fe{sup 2+} ions, remanent and saturation magnetization increase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Investigation into the crystal structure–dielectric property correlation in barium titanate nanocrystals of different sizes

For high capacitance multilayer ceramic capacitors, high dielectric constant and lead-free ceramic nanoparticles are highly desired. However, as the particle size decreases to a few tens of nanometers, their dielectric constant significantly decreases, and the underlying mechanism has yet to be fully elucidated. Herein, we report a systematic investigation into the crystal structure–dielectric property relationship of combustion-made BaTiO 3 (BTO) nanocrystals. When the nanocrystal size was 100 nm and below, a metastable paraelectric cubic phase was found in the as-received BTO (denoted as arBTO) nanocrystals based on an X-ray diffraction (XRD) study. A stable ferroelectric tetragonal phase was present when the nanocrystal size was above 200 nm. Notably, the cubic arBTO (particle size ≤100 nm) exhibited tetragonal fluctuations as revealed by Raman spectroscopy, whereas the tetragonal arBTO (particle size ≥200 nm) contained ~10% cubic fraction according to the Rietveld fitting of the XRD profiles. Thermal annealing of the multi-grain tetragonal arBTO at 950 °C yielded single crystals of annealed BTO (denoted as anBTO), whose dielectric constants were higher than those of arBTO. However, the single crystalline anBTO prevented the formation of 90° domains; therefore, they exhibited a low dielectric constant of ~300. Although X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy could not identify the exact structural defects, our study revealed that surface and bulk defects formed during synthesis affect the final crystal structures and thus the dielectric properties of BTO nanocrystals with different sizes. Finally, the understanding obtained from this study will help us design high dielectric constant perovskite nanocrystals for next-generation multilayer ceramic capacitor applications.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Predicting the Cetane Number, Sooting Tendency, and Energy Density of Terpene Fuel Additives

Abstract Discovering renewable fuels and fuel additives is paramount in reducing carbon emissions from internal combustion engines. Terpenes, a group of compounds that can be synthesized from plant matter and microorganisms, have gained significant interest in recent years as promising candidates for fuels/additives. Terpenes are a diverse class of compounds that contain rings and methyl branches, resulting in high energy densities and optimal cold weather behavior. Their variation in bond order, carbon chains, and functional groups lead to varying degrees of soot formation and performance in existing engines. The present work leverages predictive models, namely artificial neural networks, to predict the cetane number (CN), sooting tendency (quantified with yield sooting index, YSI), and energy density (quantified with lower heating value, LHV) of terpenes and hydrogenated terpenes whose sooting propensities were previously determined through experimental means. Predicted sooting propensities of these terpenes are compared with experimental values, and predicted cetane numbers and energy densities are used to comment on the compounds’ ability to act as fuels/additives. Expected prediction errors for CN, YSI, and LHV, defined by blind test set median absolute error, are within 5.56 cetane units, 3.63 yield sooting index units, and 0.77 MJ/kg respectively. Additionally, the present work investigates a variety of correlation/dependence metrics for property-property relationships, furthering our understanding of how combustion-relevant properties are related.

09 BIOMASS FUELS↗
DOE OSTI2019

Magnetic Properties of MFeCrO{sub 4} (M = Co/Ni) Prepared by Solution Combustion Method

Single phase MFeCrO{sub 4} (M = Co/Ni) nanosized samples are prepared by solution combustion method using glycine as fuel. Lattice parameter obtained after Rietveld refinement of the powder x-ray diffraction pattern of CoCrFeO{sub 4} and NiCrFeO{sub 4} samples are 8.374 and 8.325 Å and corresponding crystallite sizes are 40 and 27 nm, respectively. FTIR spectra of both samples show tetrahedral and octahedral metal oxygen bond stretching peaks at 596 and 488 cm{sup −1}, indicating spinel phase formation. DC magnetisation study indicates that both samples are ferrimagnetic at room temperature, with CoCrFeO{sub 4} having a higher value of saturation magnetisation. Mössbauer spectra indicate the presence of magnetic relaxation in the samples. Also, the strength of interaction with nearest neighbour Fe{sup 3+} cations is higher in NiCrFeO{sub 4}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Determining the Parameters of the Working Gases Used in the Process of Hypersonic Metallization of Steel Coatings

Theoretical and practical investigations of the effect of combustible gas parameters on the thermodynamic characteristics of a two-phase jet have been carried out. The influence of the thermal parameters of combustion of alkanes on the quantity of air supplied to cool the metallizer combustion chamber has been studied. The influence of the combustible mixture composition on the properties of steel coatings formed has been estimated.

36 MATERIALS SCIENCE↗
NASA NTRS1980

Aircraft Research and Technology for Future Fuels

The potential characteristics of future aviation turbine fuels and the property effects of these fuels on propulsion system components are examined. The topics that are discussed include jet fuel supply and demand trends, the effects of refining variables on fuel properties, shekle oil processing, the characteristics of broadened property fuels, the effects of fuel property variations on combustor and fuel system performance, and combuster and fuel system technology for broadened property fuels.

Source record↗
NASA NTRS2000

Flammability: A Review and Analysis

With its founding in 1975, Committee G-4 of the American Society for Testing and Materials (ASTM) embarked on the process of defining the flammability of metallic materials in oxygen-enriched atmospheres. In this process, they are joined by the National Aeronautics and Space Administration (NASA), the National Fire Protection Association (NFPA), and the Compressed Gas Association (CGA). Although none of these organizations has explicitly defined flammability, the following definitions and statements provide a composite understanding of the concept: 1. "This Standard Guide (ASTM G94-92) is concerned primarily with the properties of a material associated with its relative susceptibility to ignition and propagation of combustion." 2. "A material is considered flammable at the maximum use pressure if at least one sample burns more than 6 in. (15.2 cm). At least, five samples must be tested." NASA 3. "Flammable: Capable, when ignited of maintaining combustion under the specified environmental conditions." NFPA 53. 4. "Combustion: A complex sequence of chemical reactions between a fuel and an oxidant accompanied by the evolution of heat, and usually, the emission of light." NFPA 53. and 5. "A safe oxygen-piping transmission or distribution system is one that is designed and installed in accordance with all applicable codes and regulations for the service conditions and locations involved and further meets the special requirements for oxygen services." CGA-G4 Flammability thus equates, after ignition, to propagation of combustion, synonymous with steady state burning, under specified environmental conditions. Properties for which quantitative values are given in ASTM G94-92 and which are used to describe metals flammability consistent with the concept of steady state burning are either system independent properties, such as, enthalpies of reaction, burn ratios, flame temperatures, thermal conductivity, and heat release; or system dependent properties, such as, oxygen index, promoted combustion, threshold pressure and burn rates. Each property is reviewed and analyzed as to whether it provides an absolute or relative measure for flammability. It is shown that burn ratio, as applied to the actual steady state combustion condition, approaches the desired absolute measure of flammability.

Wilson, D. Bruce↗
DOE OSTI2018

Synthesis and magnetic properties of nanocrystalline Gd3Fe5O12 and GdFeO3 powders prepared by sol–gel auto-combustion method

Highlights: • Glycine-based gel was successfully applied in the preparation of Gd ferrites. • High-purity nanocrystalline Gd{sub 3}Fe{sub 5}O{sub 12} and GdFeO{sub 3} powders were synthesized. • Magnetic properties of nanocrystalline GdFeO{sub 3} and Gd{sub 3}Fe{sub 5}O{sub 12} were investigated. • Transition mechanism of magnetic phase was discussed in detail. - Abstract: Nanocrystalline GdFeO{sub 3} and Gd{sub 3}Fe{sub 5}O{sub 12} powders were prepared successfully by sol–gel auto-combustion method using a glycine-based gel. The as-prepared GdFeO{sub 3} and Gd{sub 3}Fe{sub 5}O{sub 12} powders presented spherical shape, and composed of continuous porous network structure due to the releasing of a large amount of gases during auto-combustion process. This special microstructure was significant for reducing the magnetic interactions between nanocrystalline powders. The Gd{sub 3}Fe{sub 5}O{sub 12} samples presented ferrimagnetic feature at low temperatures. At 10 K, the saturate magnetization is about 87.9 emu/g. As temperature increased to 300 K, the magnetization decreased rapidly since the thermal fluctuations changed the main magnetic spin ordering. The GdFeO{sub 3} samples presented antiferromagnetic feature at 5 K, and the magnetization reaches 109 emu/g at 50,000 Oe field. As temperature increased to 300 K, the antiferromagnetism decreased rapidly, and the magnetization curve presents linear tendency due to the dominant paramagnetism contribution of Gd{sup 3+} ions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

ASSESSING FUEL PROPERTY EFFECTS ON CAVITATION AND EROSION PROPENSITY USING A COMPUTATIONAL FUEL SCREENING TOOL

To advance compression ignition combustion strategies, researchers have evaluated fuel property effects and their impact on achieving higher efficiencies and lower emissions levels relative to current capabilities. Within the Department of Energy's Co-Optima initiative, there has been a recent focus on understanding the influence of fuel properties on fuel injection performance. To help identify candidate fuels that can meet desired injector performance metrics, a computational fuel screening tool is under development that can link fuel properties with the tendency of a given fuel to cavitate and lead to cavitation-induced erosion. In the initial development of this tool, five liquid fuel properties were selected to represent candidate fuels, namely density, viscosity, vapor pressure, surface tension, and heat of vaporization. A design of experiments methodology was employed to generate a set of pseudo fuel cases, which can represent the main effects and interactions among the fuel properties and be related to cavitation erosion predictions. Large eddy simulations were performed using a mixture modeling approach to predict the cavitation and erosion propensity of these pseudo-fuels in terms of the mean fuel vapor mole fraction and stored impact energy from repeated cloud collapse events. The low order regression models generated from this study revealed the importance of liquid fuel density on cavitation formation, whereas liquid viscosity was found to have a strong negative correlation with erosion severity. The surrogate models were then used in the fuel screening tool to rank the cavitation and erosion tendency of four candidate single-component fuels: methyl decanoate, isooctane, ethanol and n-dodecane. While the fuel screening tool was not able to quantitatively predict the cavitation and erosion response metrics, the tool was able to accurately rank the relative cavitation and erosion propensity of the four fuels. Overall, ethanol and iso-octane were observed to produce the highest levels of cavitation and erosion, respectively.

cavitation-induced erosion↗
DOE OSTI2015

100 MeV swift Si{sup 7+} ion induced thermoluminescence studies of nanocrystalline erbium doped ZrO{sub 2}

Pure and erbium (1mol%) doped nanocrystalline ZrO{sub 2} is synthesized by combustion technique. Thermoluminescence (TL) properties ZrO{sub 2}pellets annealed at 873 K and irradiated by 100 MeV swift Si{sup 7+} ion for various fluence are recorded. The evolution crystalline structure and crystallite size are done using by XRD data. Two TL glow curves, a well resolved one peak at ∼420 K and an unresolved with peak at ∼598 K are observed. TL intensity increases up to 3×10{sup 12} ions cm{sup −2} beyond which the TL intensity decreases. The glow peak shape method is used to calculate the TL trap parameter and discussed in this paper.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1973

Swirling jet turbulent mixing and combustion computations

Computations are presented describing the mixing and combustion of swirling jets in a coaxial stream. It is demonstrated that the boundary layer equations represent the flow reasonably well until reversed flow is imminent. For the range of parameters investigated indications are that the edge velocity has little effect on the behavior of the flow. Furthermore, confining the flow with a constant pressure wall, or impressing a favorable pressure gradient on the coaxial flow, acts to reduce the severity of the centerline adverse pressure gradient created by the swirl decay. A simple scalar eddy viscosity model, including a potential core formulation, is shown to described the behavior of weak swirling flow in the far region but is only in fair agreement with observations in the near region. The effects of swirl on a burning hydrocarbon jet exhausting into a cold coaxial stream are shown to be intensified by the reduction of the density due to combustion. The enhanced mixing properties of high swirl flow produce rapid diffusion of the burning gases into the cold edge flow causing early cessation of the NO producing reactions. Computations show that doubling the initial jet swirl could reduce the NO production by 25 percent.

Rubel, A.↗
NASA NTRS1976

New potentials for conventional aircraft when powered by hydrogen-enriched gasoline

Hydrogen enrichment for aircraft piston engines is under study in a new NASA program. The objective of the program is to determine the feasibility of inflight injection of hydrogen in general aviation aircraft engines to reduce fuel consumption and to lower emission levels. A catalytic hydrogen generator will be incorporated as part of the air induction system of a Lycoming turbocharged engine and will generate hydrogen by breaking down small amounts of the aviation gasoline used in the normal propulsion system. This hydrogen will then be mixed with gasoline and compressed air from the turbocharger before entering the engine combustion chamber. The special properties of the hydrogen-enriched gasoline allow the engine to operate at ultralean fuel/air ratios, resulting in higher efficiencies and hence less fuel consumption. This paper summarizes the results of a systems analysis study. Calculations assuming a Beech Duke aircraft indicate that fuel savings on the order of 20% are possible. An estimate of the potential for the utilization of hydrogen enrichment to control exhaust emissions indicates that it may be possible to meet the 1979 Federal emission standards.

Menard, W. A.↗
NASA NTRS1975

Uniformity of Ludwieg tube flows

Pressure and speed of sound measurements are used to obtain averaged gas properties in a Ludwieg combustion tube in which the gas is burned just prior to use. Absorption of a laser beam in the exit flow is used to check the predicted temperature uniformity. The burning process and the heat transfer to the cold walls are modeled. Interferograms of Ludwieg tube boundary layers are utilized to develop a new semiempirical boundary layer expression referred to as the integral density thickness, which is then applied to a recently developed linearized analysis of the effects of this layer. Pressure-time histories are determined for a wide range of tube flow Mach number and aspect ratio. Viscous and nonviscous effects are considered. It is shown that although the influence of the integral density thickness on the flow can be large, a modified linear theory can be used to estimate the effects for arbitrary tube flow Mach number and values of the aspect ratio that include cases where the boundary layers have merged.

Russell, D. A.↗