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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Fuel injector: Air swirl characterization aerothermal modeling, phase 2, volume 1

A well integrated experimental/analytical investigation was conducted to provide benchmark quality relevant to a prefilming type airblast fuel nozzle and its interaction with the combustor dome air swirler. The experimental investigation included a systematic study of both single-phase flows that involved single and twin co-axial jets with and without swirl. A two-component Phase Doppler Particle Analyzer (PDPA) was used to document the interaction of single and co-axial air jets with glass beads that simulate nonevaporating spray and simultaneously avoid the complexities associated with fuel atomization processes and attendant issues about the specification of relevant boundary conditions. The interaction of jets with methanol spray produced by practical airblast nozzle was also documented in the spatial domain of practical interest. Model assessment activities included the use of three turbulence models (k-epsilon, algebraic second moment (ASM), and differential second moment (DSM)) for the carrier phase, deterministic or stochastic Lagrangian treatment of the dispersed phase, and advanced numerical schemes. Although qualitatively good comparison with data was obtained for most of the cases investigated, the model deficiencies in regard to modeled dissipation rate transport equation, single length scale, pressure-strain correlation, and other critical closure issues need to be resolved before one can achieve the degree of accuracy required to analytically design combustion systems.

Nikjooy, M.↗
NASA NTRS1993

Fuel Injector: Air swirl characterization aerothermal modeling, phase 2, volume 2

A well integrated experimental/analytical investigation was conducted to provide benchmark quality data relevant to prefilming type airblast fuel nozzle and its interaction with combustor dome air swirler. The experimental investigation included a systematic study of both single-phase flows that involved single and twin co-axial jets with and without swirl. A two-component Phase Doppler Particle Analyzer (PDPA) equipment was used to document the interaction of single and co-axial air jets with glass beads that simulate nonevaporating spray and simultaneously avoid the complexities associated with fuel atomization processes and attendant issues about the specification of relevant boundary conditions. The interaction of jets with methanol spray produced by practical airblast nozzle was also documented in the spatial domain of practical interest. Model assessment activities included the use of three turbulence models (k-epsilon, algebraic second moment (ASM) and differential second moment (DSM)) for the carrier phase, deterministic or stochastic Lagrangian treatment of the dispersed phase, and advanced numerical schemes. Although qualitatively good comparison with data was obtained for most of the cases investigated, the model deficiencies in regard to modeled dissipation rate transport equation, single length scale, pressure-strain correlation, and other critical closure issues need to be resolved before one can achieve the degree of accuracy required to analytically design combustion systems.

Nikjooy, M.↗
DOE OSTI2022

Atomic Force Microscope Active Optical Probe for Single-Molecule Imaging and Time-Resolved Optical Spectroscopy (DOE SBIR Phase II/IIA Final Report)

Actoprobe LLC reports on the results of its DOE SBIR Phase II/IIA project on the development of Atomic Force Microscope Active Optical Probe for Single-Molecule Imaging and Time-Resolved Optical Spectroscopy. While chemistry science and technology greatly benefit from Atomic Force Microscopy in surface characterization, time-resolved chemical imaging on the single-molecule level lags far behind. Current scanning probe microscopy only obtains information about mechanical but not optical/chemical properties. To address this problem, the Actoprobe LLC research team has proposed a novel class of Atomic Force Microscopy probes, Ultra-Fast Pulsed Active Atomic Force Microscopy Optical Probes (UFP AAOPs), that will allow ultrafast time-resolved optical and chemical imaging at the nanoscale. As envisioned, these unique optical probes will perform the functions of conventional Atomic Force Microscopy probes and, in addition, will simultaneously provide chemical information about molecular scale interactions. This innovation is accomplished by integrating an ultrafast pulsed Quantum Dot laser source into an Atomic Force Microscopy probe. This report describes our progress with the fabrication of an ultrafast micrometer-size semiconductor laser, based on “artificial atoms” - Quantum Dots, integrated with an Atomic Force Microscopy probe. In this Phase II/IIA project, we have demonstrated the feasibility of the UFP AAOP concept by fabricating a first prototype of the UFP AAOP. The excellent performance of the probe has been proven in terms of AFM and optical spatial resolution through rigorous tests. The UFP AAOP provides pulses with less than 4 ps duration and higher than 11 GHz repetition rate, and spatial resolution better than 300 nm at 1240 nm wavelength. Technically, it is possible to reduce the pulse width to less than 1 ps and to improve lateral resolution to ~ 0.5 nm, which implies the potential capability for the probe to characterize chemical compounds with single-molecule resolution. The UFP AAOP fabrication procedure has been developed for wafer-scale production of multiple devices, with the yield of the process estimated to be lower than 1% with the limited fabrication capabilities and equipment available for use in the research project. However, using high-volume production tools and special GaAs processing equipment, the yield can be significantly improved, theoretically to ~ 50%. Finally, economic feasibility and scale-up manufacturing potential were analyzed for UFP AAOP and found to be very promising. In summary, the Actoprobe team has successfully demonstrated the feasibility of the UFP AAOP concept.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Symmetry assessment of an air-blast atomizer spray

This study represents an evaluation of the extent to which conventional and recently introduced modern diagnostics can assess the symmetry of sprays formed by three atomizers of identical design. The conventional diagnostics include sheet-lit photography, patternation, and laser diffraction. The modern diagnostic is laser interferometry (phase Doppler). Symmetry is assessed in ambient conditions for four atomizer orientations, and comparisons are made between the diagnostic techniques. The results demonstrate that conventional and modern diagnostics are consistent in the assessment of symmetry, patternation and phase Doppler are most effective in establishing symmetry of mass flux, and phase Doppler, although more tedious to employ, provides the additional information necessary to establish the sources of detected asymmetries in terms of nonuniformities in droplet velocities, size distributions, volume flux, and concentration.

Mcdonnell, V. G.↗
NASA NTRS1995

Second International Workshop on Harmonic Oscillators

The Second International Workshop on Harmonic Oscillators was held at the Hotel Hacienda Cocoyoc from March 23 to 25, 1994. The Workshop gathered 67 participants; there were 10 invited lecturers, 30 plenary oral presentations, 15 posters, and plenty of discussion divided into the five sessions of this volume. The Organizing Committee was asked by the chairman of several Mexican funding agencies what exactly was meant by harmonic oscillators, and for what purpose the new research could be useful. Harmonic oscillators - as we explained - is a code name for a family of mathematical models based on the theory of Lie algebras and groups, with applications in a growing range of physical theories and technologies: molecular, atomic, nuclear and particle physics; quantum optics and communication theory.

Han, Daesoo↗
NASA NTRS2003

Coarsening Experiment Prepared for Flight

The Coarsening in Solid-Liquid Mixtures-2 (CSLM-2) experiment is a materials science spaceflight experiment whose purpose is to investigate the kinetics of competitive particle growth within a liquid matrix. During coarsening, small particles shrink by losing atoms to larger particles, causing the larger particles to grow. In this experiment, solid particles of tin will grow (coarsen) within a liquid lead-tin eutectic matrix. The following figures show the coarsening of tin particles in a lead-tin (Pb-Sn) eutectic as a function of time. By conducting this experiment in a microgravity environment, we can study a greater range of solid volume fractions, and the effects of sedimentation present in terrestrial experiments will be negligible. The CSLM-2 experiment flew November 2002 on space shuttle flight STS-113 for operation on the International Space Station, but it could not be run because of problems with the Microgravity Science Glovebox in the U.S. Laboratory module. Additional samples will be sent to ISS on subsequent shuttle flights.

Hickman, J. Mark↗
DOE OSTI2022

Novel Class of Rhenium Borides Based on Hexagonal Boron Networks Interconnected by Short B 2 Dumbbells

Transition metal borides are known due to their attractive mechanical, electronic, refractive, and other properties. A new class of rhenium borides was identified by synchrotron single-crystal X-ray diffraction experiments in laser-heated diamond anvil cells between 26 and 75 GPa. Recoverable to ambient conditions, compounds rhenium triboride (ReB 3 ) and rhenium tetraboride (ReB 4 ) consist of close-packed single layers of rhenium atoms alternating with boron networks built from puckered hexagonal layers, which link short bonded (~ 1.7 angstrom) axially oriented B 2 dumbbells. The short and incompressible Re-B and B-B bonds oriented along the hexagonal c-axis contribute to low axial compressibility comparable with the linear compressibility of diamond. Sub-millimeter samples of ReB 3 and ReB 4 were synthesized in a large-volume press at pressures as low as 33 GPa and used for material characterization. Crystals of both compounds are metallic and hard (Vickers hardness, H V = 34(3) GPa). Geometrical, crystal-chemical, and theoretical analysis considerations suggest that potential ReB x compounds with x > 4 can be based on the same principle of structural organization as in ReB 3 and ReB 4 and possess similar mechanical and electronic properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Nuclear quantum effects in molecular liquids across chemical space

Abstract Nuclear quantum effects (NQEs) influence many physical and chemical phenomena, particularly those involving light atoms or occurring at low temperatures. However, their impact has been carefully quantified in few systems-like water-and is rarely considered more broadly. Here we use path-integral molecular dynamics to systematically investigate NQEs on thermophysical properties of 92 organic liquids at ambient conditions. Depending on chemical constitution, we find substantial impact across thermal expansivity, compressibility, dielectric constant, enthalpy of vaporization, and notably molar volume, which shows consistent, positive quantum-classical differences up to 5%; similar, less pronounced trends manifest as isotope effects from deuteration. Using data-driven analysis, we identify three features-molar mass, classical hydrogen density, and classical thermal expansivity-that accurately predict NQEs and facilitate understanding of how characteristics like branching and heteroatom content influence behavior. This work highlights the broad relevance of NQEs in molecular liquids, while also providing a conceptual and practical framework to anticipate their impact.

Science & Technology - Other Topics↗
DOE OSTI2020

Understanding Pore Formation in ALD Alumina Overcoats

AlO X thin films deposited by atomic layer deposition (ALD) have previously been used to increase both stability and selectivity of supported palladium catalysts and are known to develop nanoscale porosity upon heating. Furthermore, understanding the factors that affect ALD thin film porosity would enable future design of layered catalytic structures with tunable nanoscale features on industrially relevant high surface area materials. In this study, porous and nonporous aluminum oxide supports with and without palladium nanoparticles were overcoated with thin films of 2 - 7 nm AlO X by ALD deposited at temperatures of 100 °C, 200 °C and 300 °C. Hydroxyl loss and changes in surface chemistry were observed upon heating the films, and changes in surface area and pore volume of the annealed films were correlated to AlO x deposition temperature and presence of Pd. Crystallization of the overcoat to γ-Al 2 O 3 is shown to occur separately from hydroxyl loss and pore formation. A mechanistic understanding of pore formation in AlO X ALD films is obtained by reference to studies of the structural transformations accompanying the formation of transition aluminas from hydroxide precursors. Additionally, a direct and tunable correlation is established between pore development and the overall hydroxyl content of AlO X ALD coatings.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Disconnection-Mediated Transition in Segregation Structures at Twin Boundaries

Twin boundaries play an important role in the thermodynamics, stability, and mechanical properties of nanocrystalline metals. Understanding their structure and chemistry at the atomic scale is key to guide strategies for fabricating nanocrystalline materials with improved properties. In this work, we report an unusual segregation phenomenon at gold-doped platinum twin boundaries, which is arbitrated by the presence of disconnections, a type of interfacial line defect. By using atomistic simulations, we show that disconnections containing a stacking fault can induce an unexpected transition in the interfacial-segregation structure at the atomic scale, from a bilayer, alternating-segregation structure to a trilayer, segregation-only structure. This behavior is found for faulted disconnections of varying step heights and dislocation characters. Supported by a structural analysis and the classical Langmuir–McLean segregation model, we reveal that this phenomenon is driven by a structurally induced drop of the local pressure across the faulted disconnection accompanied by an increase in the segregation volume.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Energetics of polymeric carbon monoxide

The transformation of carbon monoxide (CO) from a molecular liquid to a polymeric solid under isothermal compression at room temperature is investigated using first principles theory. We report structural and thermodynamic properties from ambient density up to 2.45 g/cc obtained using density functional theory molecular dynamics simulations, including hybrid exchange corrections. The theoretical results are compared with newly obtained polymeric CO samples, synthesized in a large volume press. The explosive performance of polymeric CO is predicted and discussed. Under most favorable assumptions, it is found to be comparable to trinitrotoluene.

25 ENERGY STORAGE↗
NASA NTRS2001

Using Model-Based Reasoning for Autonomous Instrument Operation - Lessons Learned From IMAGE/LENA

Model-based reasoning has been applied as an autonomous control strategy on the Low Energy Neutral Atom (LENA) instrument currently flying on board the Imager for Magnetosphere-to-Aurora Global Exploration (IMAGE) spacecraft. Explicit models of instrument subsystem responses have been constructed and are used to dynamically adapt the instrument to the spacecraft's environment. These functions are cast as part of a Virtual Principal Investigator (VPI) that autonomously monitors and controls the instrument. In the VPI's current implementation, LENA's command uplink volume has been decreased significantly from its previous volume; typically, no uplinks are required for operations. This work demonstrates that a model-based approach can be used to enhance science instrument effectiveness. The components of LENA are common in space science instrumentation, and lessons learned by modeling this system may be applied to other instruments. Future work involves the extension of these methods to cover more aspects of LENA operation and the generalization to other space science instrumentation.

Johnson, Michael A.↗
DOE OSTI2021

Evaluation of electrochemical performance and redox activity of Fe in Ti doped layered P2-Na0.67Mn0.5Fe0.5O2 cathode for sodium ion batteries

Here, we report a wet synthesis-based titanium doping strategy to improve the structural stability and electrochemical performances, such as cycling stability and rate capability, of P2-type Na 0.67 Fe 0.5 Mn 0.5 O 2 layered oxide cathodes. Through Ti 4+ doping aimed at replacing some of the Mn and Fe atoms in the crystal structure, effective mitigation of the Jahn Teller distortion caused by active Mn 3+ before charging and Fe 4+ after charging was achieved. X-ray diffraction (XRD), Raman spectroscopy, Electrochemical Impedance Spectroscopy (EIS) and Mössbauer spectroscopy were used to investigate the effects of the Ti 4+ dopant before and after cycling. It was observed that Ti 4+ doping increased the Na layer thickness, minimized the lattice volume strain, showed better structural stability, minimally decreased Fe migration to the Na layer, and lowered charge transfer resistance in these P2-type cathodes. Overall, our reported synthesis methodology and electrochemical characterizations highlight the feasibility of Ti doping in sodium layered oxide P2-type cathodes.

25 ENERGY STORAGE↗
DOE OSTI2021

Demonstration of Energy-Resolved γ-Ray Detection at Room Temperature by the CsPbCl 3 Perovskite Semiconductor

The detection of gamma-rays at room temperature with high-energy resolution using semiconductors is one of the most challenging applications. The presence of even the smallest amount of defects is sufficient to kill the signal generated from gamma-rays which makes the availability of semiconductors detectors a rarity. Lead halide perovskite semiconductors exhibit unusually high defect tolerance leading to outstanding and unique optoelectronic properties and are poised to strongly impact applications in photoelectric conversion/detection. Here we demonstrate for the first time that large size single crystals of the all-inorganic perovskite CsPbCl 3 semiconductor can function as a high-performance detector for gamma-ray nuclear radiation at room temperature. CsPbCl 3 is a wide-gap semiconductor with a bandgap of 3.03 eV and possesses a high effective atomic number of 69.8. We identified the two distinct phase transitions in CsPbCl 3 , from cubic (Pm-3m) to tetragonal (P4/mbm) at 325 K and finally to orthorhombic (Pbnm) at 316 K. Despite crystal twinning induced by phase transitions, CsPbCl 3 crystals in detector grade can be obtained with high electrical resistivity of similar to 1.7 X 10 9 Ω∙cm. The crystals were grown from the melt with volume over several cubic centimeters and have a low thermal conductivity of 0.6 W m -1 K -1 . The mobilities for electron and hole carriers were determined to similar to 30 cm 2 /(V s). Using photoemission yield spectroscopy in air (PYSA), we determined the valence band maximum at 5.66 +/- 0.05 eV. Under gamma-ray exposure, our Schottky-type planar CsPbCl 3 detector achieved an excellent energy resolution (similar to 16% at 122 keV) accompanied by a high figure-of-merit hole mobility-lifetime product (3.2 x 10 -4 cm 2 /V) and a long hole lifetime (16 mu s). The results demonstrate considerable defect tolerance of CsPbCl 3 and suggest its strong potential for gamma-radiation and X-ray detection at room temperature and above.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1991

Liquid atomization by coaxial rocket injectors

The atomization characteristics of a scaled-down version of a coaxial rocket injector was investigated using a phase Doppler particle analyzer (PDPA). The injector was operated in the conventional mode with liquid being injected through its inner orifice and gas being injected through its outer annulus. The shearing action occurring at the liquid-gas interface causes the liquid jet to atomize. In this study, two different liquid-air systems, namely a water-air system and a liquid nitrogen-gaseous nitrogen system, were chosen for detailed investigation. This paper discusses the performance characteristics of the coaxial injector under different flow and geometric conditions. Specifically, the effects of injection gas pressure and the injector cavity size on variables such as the mean particle diameter, Sauter mean diameter, number density, volume flux, and velocity have been presented.

Sankar, S. V.↗
NASA NTRS2003

Soot Surface Oxidation in Laminar Hydrocarbon/Air Diffusion Flames at Atmospheric Pressure

Soot surface oxidation was studied experimentally in laminar hydrocarbon/air diffusion flames at atmospheric pressure. Measurements were carried out along the axes of round fuel jets burning in coflowing dry air considering acetylene-nitrogen, ethylene, propyiene-nitrogen, propane and acetylene-benzene-nitrogen in the fuel stream. Measurements were limited to the initial stages of soot oxidation (carbon consumption less than 70%) where soot oxidation occurs at the surface of primary soot particles. The following properties were measured as a function of distance above the burner exit: soot concentrations by deconvoluted laser extinction, soot temperatures by deconvoluted multiline emission, soot structure by thermophoretic sampling and analysis using Transmission Electron Microscopy (TEM), concentrations of major stable gas species (N2, H2O, H2, O2, CO, CO2, CH4, C2H2, C2H6, C3H6, C3H8, and C6H6) by sampling and gas chromatography, concentrations of some radical species (H, OH, O) by deconvoluted Li/LiOH atomic absorption and flow velocities by laser velocimetry. For present test conditions, it was found that soot surface oxidation rates were not affected by fuel type, that direct rates of soot surface oxidation by O2 estimated from Nagle and Strickland-Constable (1962) were small compared to observed soot surface oxidation rates because soot surface oxidation was completed near the flame sheet where O2 concentrations were less than 3% by volume, and that soot surface oxidation rates were described by the OH soot surface oxidation mechanism with a collision efficiency of 0.14 and an uncertainty (95% confidence) of +/- 0.04 when allowing for direct soot surface oxidation by O2, which is in reasonably good agreement with earlier observations of soot surface oxidation rates in both premixed and diffusion flames at atmospheric pressure.

Xu, F.↗
NASA NTRS2012

Designing Spacecraft and Mission Operations Plans to Meet Flight Crew Radiation Dose Requirements: Why is this an "Epic Challenge" for Long-Term Manned Interplanetary Flight

Outline of presentation: (1) Radiation Shielding Concepts and Performance - Galactic Cosmic Rays (GCRs) (1a) Some general considerations (1b) Galactic Cosmic Rays (2)GCR Shielding I: What material should I use and how much do I need? (2a) GCR shielding materials design and verification (2b) Spacecraft materials point dose cosmic ray shielding performance - hydrogen content and atomic number (2c) Accelerator point dose materials testing (2d) Material ranking and selection guidelines (2e) Development directions and return on investment (point dose metric) (2f) Secondary particle showers in the human body (2f-1) limited return of investment for low-Z, high-hydrogen content materials (3) GCR shielding II: How much will it cost? (3a) Spacecraft design and verification for mission radiation dose to the crew (3b) Habitat volume, shielding areal density, total weight, and launch cost for two habitat volumes (3c) It's All about the Money - Historical NASA budgets and budget limits (4) So, what can I do about all this? (4a) Program Design Architecture Trade Space (4b) The Vehicle Design Trade Space (4c) Some Near Term Recommendations

Koontz, Steven↗
DOE OSTI2021

An Atom Probe Tomography Study of the Through Wall Attenuation Effect on Cu-rich Precipitate Formation in a Reactor Pressure Vessel Steel

In this study, high-Cu weld material harvested from an ex service reactor pressure vessel (RPV) steel from Unit 1 of the decommissioned Zion Nuclear Generating Station has been characterized using atom probe tomography. Samples taken from 4 different positions through the thicknesses of the pressure vessel wall from the water-side to the air-side were characterized, along with an unirradiated baseline material. In the baseline material, no precipitates were found and the Cu was observed to be fully in solid solution; however, scanning transmission electron microscopy combined with energy dispersive spectroscopy (STEM-EDS) revealed the presence of ϵ -Cu that form during processing of the material and results in the concomitant decrease of matrix Cu. Following irradiation, a high number density of nano-scale Cu-rich precipitates (CRPs) were observed, uniformly distributed throughout the matrix. The Cu content within the CRPs was found to be ~30-35 at.% regardless of location in the wall. No statistically significant variation in the compositions, mean radius, number density, or volume fraction as a function of location within the wall was observed. The measured matrix Cu level excluding CRPs contribution was found to be ~90 appm higher than the solubility limit suggesting that further nucleation and growth of the CRPs under continued operations would have occurred. These results clearly demonstrate that the neutron energy attenuation has no significant effect on the precipitation kinetics of CRPs regardless of location in the wall in high-Cu RPV steels under irradiation.

36 MATERIALS SCIENCE↗