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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Matryoshka phonon twinning in α-GaN

Understanding lattice dynamics is crucial for effective thermal management in electronic devices because phonons dominate thermal transport in most semiconductors. α -GaN has become a focus of interest as one of the most important third-generation power semiconductors, however, the knowledge on its phonon dynamics remains limited. Here we show a Matryoshka phonon dispersion of α -GaN with the complementary inelastic X-ray and neutron scattering techniques and the first-principles calculations. Such Matryoshka twinning throughout the basal plane of the reciprocal space is demonstrated to amplify the anharmonicity of the related phonons through creating abundant three-phonon scattering channels and cutting the lifetime of affected modes by more than 50%. Such phonon topology contributes to reducing the in-plane thermal transport, thus the anisotropic thermal conductivity of α -GaN. The results not only have implications for engineering the thermal performance of α -GaN, but also offer valuable insights on the role of anomalous phonon topology in thermal transport of other technically semiconductors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS2001

Fundamental Boiling and RP-1 Freezing Experiments

This paper describes results from experiments performed to help understand certain aspects of the MC-1 engine prestart thermal conditioning procedure. The procedure was constrained by the fact that the engine must chill long enough to get quality LOX at the LOX pump inlet but must be short enough to prevent freezing of RP-1 in the fuel pump. A chill test of an MC-1 LOX impeller was performed in LN2 to obtain data on film boiling, transition boiling and impeller temperature histories. The transition boiling data was important to the chill time so a subsequent experiment was performed chilling simple steel plates in LOX to obtain similar data for LOX. To address the fuel freezing concern, two experiments were performed. First, fuel was frozen in a tray and its physical characteristics were observed and temperatures of the fuel were measured. The result was physical characteristics as a function of temperature. Second was an attempt to measure the frozen thickness of RP-1 on a cold wall submerged in warm RP-1 and to develop a method for calculating that thickness for other conditions.

Goode, Brian↗
NASA NTRSDate not supplied

Hot Hydrogen Testing of Uranium Nitride Cermet for Nuclear Thermal Propulsion

This study investigated the thermochemical stability and performance characteristics of uranium mononitride tungsten molybdenum cermet (UN-Mo30W) as a potential fuel material for Nuclear Thermal Propulsion (NTP) engines. Twelve monolithic cylinders were subjected to conditions simulating an active NTP engine. The tests demonstrated thermal variability within the test article and highlighted the dissociation of UN into U and N2 at elevated temperatures, affecting the microstructure and causing bonding between cermet wafers and cooling tubes. Findings indicate that while UN-Mo30W cermet exhibits some desirable properties for NTP applications, its suitability is limited by high-temperature thermochemical instability.

nuclear fuels↗
NASA NTRS1981

Buffer thermal energy storage for an air Brayton solar engine

The application of latent-heat buffer thermal energy storage to a point-focusing solar receiver equipped with an air Brayton engine was studied. To demonstrate the effect of buffer thermal energy storage on engine operation, a computer program was written which models the recuperator, receiver, and thermal storage device as finite-element thermal masses. Actual operating or predicted performance data are used for all components, including the rotating equipment. Based on insolation input and a specified control scheme, the program predicts the Brayton engine operation, including flows, temperatures, and pressures for the various components, along with the engine output power. An economic parametric study indicates that the economic viability of buffer thermal energy storage is largely a function of the achievable engine life.

Strumpf, H. J.↗
NASA NTRS2003

Spacecraft Design Thermal Control Subsystem

This slide presentation reviews the functions of the thermal control subsystem engineers in the design of spacecraft. The goal of the thermal control subsystem that will be used in a spacecraft is to maintain the temperature of all spacecraft components, subsystems, and all the flight systems within specified limits for all flight modes from launch to the end of the mission. For most thermal control subsystems the mass, power and control and sensing systems must be kept below 10% of the total flight system resources. This means that the thermal control engineer is involved in all other flight systems designs. The two concepts of thermal control, passive and active are reviewed and the use of thermal modeling tools are explained. The testing of the thermal control is also reviewed.

thermal control↗
NASA NTRS2002

Analysis of the Magneto-Hydrodynamic (MHD) Energy Bypass Engine for High-Speed Air-Breathing Propulsion

The performance of the MHD energy bypass air-breathing engine for high-speed propulsion is analyzed in this investigation. This engine is a specific type of the general class of inverse cycle engines. In this paper, the general relationship between engine performance (specific impulse and specific thrust) and the overall total pressure ratio through an engine (from inlet plane to exit plane) is first developed and illustrated. Engines with large total pressure decreases, regardless of cause or source, are seen to have exponentially decreasing performance. The ideal inverse cycle engine (of which the MHD engine is a sub-set) is then demonstrated to have a significant total pressure decrease across the engine; this total pressure decrease is cycle-driven, degrades rapidly with energy bypass ratio, and is independent of any irreversibility. The ideal MHD engine (inverse cycle engine with no irreversibility other than that inherent in the MHD work interaction processes) is next examined and is seen to have an additional large total pressure decrease due to MHD-generated irreversibility in the decelerator and the accelerator. This irreversibility mainly occurs in the deceleration process. Both inherent total pressure losses (inverse cycle and MHD irreversibility) result in a significant narrowing of the performance capability of the MHD bypass engine. The fundamental characteristics of MHD flow acceleration and flow deceleration from the standpoint of irreversibility and second-law constraints are next examined in order to clarify issues regarding flow losses and parameter selection in the MM modules. Severe constraints are seen to exist in the decelerator in terms of allowable deceleration Mach numbers and volumetric (length) required for meaningful energy bypass (work interaction). Considerable difficulties are also encountered and discussed due to thermal/work choking phenomena associated with the deceleration process. Lastly, full engine simulations utilizing inlet shock systems, finite-rate chemistry, wall cooling with thermally balanced engine (fuel heat sink), fuel injection and mixing, friction, etc. are shown and discussed for both the MHD engine and the conventional scramjet. The MHD bypass engine has significantly lower performance in all categories across the Mach number range (8 to 12.2). The lower performance is attributed to the combined effects of 1) additional irreversibility and cooling requirements associated with the MHD components and 2) the total pressure decrease associated with the inverse cycle itself.

Riggins, David W.↗
NASA NTRSDate not supplied

Modeling Validation and Its Design Relevance for NTP Fuel Elements

The development of Nuclear Thermal Propulsion engines depends heavily on modeling and simulation of a number of disciplines—neutronic / fluid / thermal / structural are only a start. Further, rockets involve extreme conditions, particularly high material temperatures in the nuclear fuel. This paper considers validation of the underling physical models and codes and how their accuracy influences several design challenges. Several issues are identified, where models, material data, could enable design solutions. In particular, thermal and CTE mismatch stresses are a concern, and stress predictions would benefit from improved mechanical property data at high temperatures. Nuclear inter-element heating causes propellant flow maldistribution and performance risks, but a simple model provides insights. High temperature chemical diffusion should be modeled to understand fuel element mass loss.

Nuclear Propulsion↗
NASA NTRSDate not supplied

Modeling Validation and Its Design Relevance for NTP Fuel Elements

The development of Nuclear Thermal Propulsion engines depends heavily on modeling and simulation of a number of disciplines—neutronic / fluid / thermal / structural are only a start. Further, rockets involve extreme conditions, particularly high material temperatures in the nuclear fuel. This paper considers validation of the underling physical models and codes and how their accuracy influences several design challenges. Several issues are identified, where models, material data, could enable design solutions. In particular, thermal and CTE mismatch stresses are a concern, and stress predictions would benefit from improved mechanical property data at high temperatures. Nuclear inter-element heating causes propellant flow maldistribution and performance risks, but a simple model provides insights. High temperature chemical diffusion should be modeled to understand fuel element mass loss.

Nuclear Propulsion↗
NASA NTRS1979

A thermal control approach for a solar electric propulsion thrust subsystem

A thrust subsystem thermal control design is defined for a Solar Electric Propulsion System (SEPS) proposed for the comet Halley Flyby/comet Tempel 2 rendezvous mission. A 114 node analytic model, developed and coded on the systems improved numerical differencing analyzer program, was employed. A description of the resulting thrust subsystem thermal design is presented as well as a description of the analytic model and comparisons of the predicted temperature profiles for various SEPS thermal configurations that were generated using this model. It was concluded that: (1) a BIMOD engine system thermal design can be autonomous; (2) an independent thrust subsystem thermal design is feasible; (3) the interface module electronics temperatures can be controlled by a passive radiator and supplementary heaters; (4) maintaining heat pipes above the freezing point would require an additional 322 watts of supplementary heating power for the situation where no thrusters are operating; (5) insulation is required around the power processors, and between the interface module and the avionics module, as well as in those areas which may be subjected to solar heating; and (6) insulation behind the heat pipe radiators is not necessary.

Maloy, J. E.↗
DOE OSTI2025

Integrated Molten Salt Reactor Modeling Capabilities in NEAMS Thermal Hydraulics Tools

The DOE neams program supports a full range of computational thermal fluids analysis capabilities and code developments for a broad range of advanced reactor concepts. The research and development approach under the thermal fluids technical area synergistically combines three length and time scales in a hierarchical multi-scale approach. To enable multi-scale thermal fluids capability using these codes, a key joint effort has been underway to develop an integrated system- and engineering-scale thermal fluids analysis capability, through integration of SAM and Pronghorn codes, both based on the MOOSE framework. This report summarizes recent advances in developing an integrated system- and engineering-scale modeling capability for the msr concept, which has gained significant interest in recent years. A consistent framework was established by coupling Pronghorn and SAM through the Saline interface, with thermophysical properties provided by the Molten Salt Thermal Property Database (MSTDB-TP). Further improvements were made to the coupling schemes and domain-overlapping strategies, enhancing the stability and robustness of multi-code simulations. Verification and validation efforts demonstrate the accuracy of this integration across a range of benchmark problems, including one-dimensional heated pipe flows, three-dimensional natural convection loops with evolving isotopic compositions, and \gls{msre} demonstration cases. Within Pronghorn, new capabilities were introduced to model corrosion and noble-metal plating phenomena, supported by an extended thermal-hydraulics framework and refined turbulence treatments. To capture two-phase flow behavior, a multiphase Euler–Euler model was implemented in Pronghorn, including advanced closure relations, high-resolution advection techniques, and capillary force reconstruction. Preliminary verification cases confirm the fidelity of the approach, while planned validation efforts target canonical multiphase benchmarks and application to msr components such as the msre pump bowl. Finally, updates to SAM’s msr mass transfer modeling were extended to consider noble gas migration into porous structures like graphite. The point kinetics model was updated to include reactivity feedback contributions from any defined species, such as xenon. The gas transport model was expanded for applicability to gas mixtures, bubble efflux phenomena, and species transport between liquid and gas phases. A selection of multi-scale Sherwood number correlations from MOSCATO/NekRS and multi-phase correlations from literature have been added for improved accuracy in calculating mass transfer coefficients. A companion effort on developing system-level redox corrosion has also been incorporated into SAM. Collectively, these enhancements strengthen the predictive capability of SAM and Pronghorn for simulating MSR thermal-hydraulics, corrosion, multiphase behavior, and fission-product transport, providing a more complete toolset for design, safety analysis, and licensing support of next-generation \gls{msr}s.

42 - ENGINEERING↗
NASA NTRS2016

Thermal Expansion Behavior of Hot-Pressed Engineered Matrices

Advanced engineered matrix composites (EMCs) require that the coefficient of thermal expansion (CTE) of the engineered matrix (EM) matches those of the fiber reinforcements as closely as possible in order to reduce thermal compatibility strains during heating and cooling of the composites. The present paper proposes a general concept for designing suitable matrices for long fiber reinforced composites using a rule of mixtures (ROM) approach to minimize the global differences in the thermal expansion mismatches between the fibers and the engineered matrix. Proof-of-concept studies were conducted to demonstrate the validity of the concept.

engineered matrix↗
NASA NTRS1990

High-temperature thermal storage systems for advanced solar receivers materials selections

Advanced space power systems that use solar energy and Brayton or Stirling heat engines require thermal energy storage (TES) systems to operate continuously through periods of shade. The receiver storage units, key elements in both Brayton and Stirling systems, are designed to use the latent heat of fusion of phase-change materials (PCMs). The power systems under current consideration for near-future National Aeronautics and Space Administration space missions require working fluid temperatures in the 1100 to 1400 K range. The PCMs under current investigation that gave liquid temperatures within this range are the fluoride family of salts. However, these salts have low thermal conductivity, which causes large temperature gradients in the storage systems. Improvements can be obtained, however, with the use of thermal conductivity enhancements or metallic PCMs. In fact, if suitable containment materials can be found, the use of metallic PCMs would virtually eliminate the orbit associated temperature variations in TES systems. The high thermal conductivity and generally low volume change on melting of germanium and alloys based on silicon make them attractive for storage of thermal energy in space power systems. An approach to solving the containment problem, involving both chemical and physical compatibility, preparation of NiSi/NiSi2, and initial results for containment of germanium and NiSi/NiSi2, are presented.

Wilson, D. F.↗
NASA NTRS1984

Overview of Advanced Stirling and Gas Turbine Engine Development Programs and Implications for Solar Thermal Electrical Applications

The DOE automotive advanced engine development projects managed by the NASA Lewis Research Center were described. These included one Stirling cycle engine development and two air Brayton cycle development. Other engine research activities included: (1) an air Brayton engine development sponsored by the Gas Research Institute, and (2) plans for development of a Stirling cycle engine for space use. Current and potential use of these various engines with solar parabolic dishes were discussed.

Alger, D.↗
NASA NTRS2001

Thermal Analysis of the MC1 Engine Turbopump

The MC1 Engine turbopump supplied the propellants to the main injector. The turbopump consisted of four parts; lox pump, interpropellant seal package (IPS), RP pump and turbine. The thermal analysis was divided into two 2D finite element models; Housing or stationary parts and rotor or rotating parts. Both models were analyzed at the same boundary conditions using SINDA. The housing model consisted of, lox pump housing, ips housing, RP housing, turbine inlet housing, turbine housing, exit guide vane, heat shield and both bearing outer races. The rotor model consisted of the lox impeller; lox end bearing and id race, RP impeller, and RP bearing and id race, shaft and turbine disk. The objectives of the analysis were to: (1) verified the original design and recommend modifications to it, (2) submitted a thermal environment to support the structural analysis, (3) support the component and engine test program. and (4) to support the X34 vehicle program.

Roman, Jose↗
NASA NTRS2002

Thermal Analysis of the MCI Engine Turbopump

The MCI Engine turbopump supplied the propellants to the main injector. The turbopump consisted of four parts; lox pump, interpropellant seal package (IPS), RP pump and turbine. The thermal analysis was divided into two 2D finite element models; Housing or stationary parts and rotor or rotating parts. Both models were analyzed at the same boundary conditions using SINDA. The housing model consisted of; lox pump housing, ips housing, RP housing, turbine inlet housing, turbine housing, exit guide vane, heat shield and both bearing outer races. The rotor model consisted of the lox impeller; lox end bearing and id race, RP impeller, and RP bearing and id race, shaft and turbine disk. The objectives of the analysis were to (1) verified the original design and recommend modifications to it, (2) submitted a thermal environment to support the structural analysis, (3) support the component and engine test program and (4) to support the X34 vehicle program.

Roman, Jose↗
DOE OSTI2022

Heavy Duty Natural Gas Single Cylinder Research Engine Installation, Commissioning, and Baseline Testing

Natural Gas (NG) Internal Combustion Engines (ICE) are a promising alternative to diesel engines for on-road heavy-duty applications to reduce greenhouse gas and harmful pollutant emissions. NG engines have not been widely adopted due to the lower thermal efficiency compared with diesel engine counterparts. To develop the base knowledge required to reach the desired efficiency, a Single Cylinder Engine (SCE) is the most effective platform to acquire reliable and repeatable data. A SCE test cell was developed using a Cummins 15-liter six-cylinder heavy-duty engine block modified to fire one cylinder (2.5-liter displacement). A Woodward Large Engine Control Module (LECM) is integrated to permit implementation of real-time advanced combustion control. Intake and exhaust characteristics, fuel composition, and exhaust gas recirculated substitution rate (EGR) are fully adjustable. A high-speed data acquisition system acquires in-cylinder, intake, and exhaust pressure for combustion analysis. The baseline testing shows reliable and consistent results for engine thermal efficiency, indicated mean effective pressure (IMEP), and coefficient of variance of the IMEP over a wide range of operating conditions while achieving effective control of all engine control and operation variables. This test cell will be used to conduct a research program to develop new and innovative control algorithms and CFD optimized combustion chamber designs, allowing ultra-high efficiency and low emissions for NG ICE heavy-duty on-road applications.

03 NATURAL GAS↗
NASA NTRS1993

Advanced transportation system studies. Alternate propulsion subsystem concepts: Propulsion database

The Advanced Transportation System Studies alternate propulsion subsystem concepts propulsion database interim report is presented. The objective of the database development task is to produce a propulsion database which is easy to use and modify while also being comprehensive in the level of detail available. The database is to be available on the Macintosh computer system. The task is to extend across all three years of the contract. Consequently, a significant fraction of the effort in this first year of the task was devoted to the development of the database structure to ensure a robust base for the following years' efforts. Nonetheless, significant point design propulsion system descriptions and parametric models were also produced. Each of the two propulsion databases, parametric propulsion database and propulsion system database, are described. The descriptions include a user's guide to each code, write-ups for models used, and sample output. The parametric database has models for LOX/H2 and LOX/RP liquid engines, solid rocket boosters using three different propellants, a hybrid rocket booster, and a NERVA derived nuclear thermal rocket engine.

Levack, Daniel↗