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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Electron loss coefficients for the D-region of the ionosphere from rocket measurements during the eclipses of March 1970 and November 1966.

Observation that recombination-like electron loss coefficients measured during the March 1970 eclipse coincide with those from the November 1966 eclipse and range from 2 x 10 to the minus 7th power cu cm/sec at Z sub zero + 6 km to 0.00005 cu cm/sec at Z sub zero -2 km, where Z sub zero is the altitude of the steep gradient of electron concentration. During totality, Z sub zero was 82.5 km in 1970, and 86.8 km in 1966. For full-sun conditions, Z sub zero was 84 km on both eclipse days. Attachment-like electron loss coefficients from both eclipses are in good agreement below Z sub zero, and have a nearly constant value of about 0.008 per sec. Below Z sub zero, attachment-like loss rates agree with production rates - i.e., electron concentration is proportional to electron production.

Mechtly, E. A.↗
DOE OSTI2023

Performance Evaluation and Costs of a Combined Ground Source Heat Pump and Solar Photovoltaic Storage System in an Extreme Cold Climate

This report outlines the effectiveness and economics of a ground source heat pump system installed together with solar photovoltaic panels and a battery storage system in a local community building situated in a cold climate. The community building is a tribal building located in Ruby, Alaska. Power from solar photovoltaic panels is supplemented by electricity purchased from the local community microgrid. A ground source heat pump was commissioned three years after the building was occupied, and supplements the heat generated by a boiler for both heat and domestic hot water. Data collected over the 2021-2022 heating season shows that the heat pump is providing heat to the building about 19% of the time with an average coefficient of performance of 2.68, ranging from below 2.5 in winter to above 3.0 in summer. The solar photovoltaic panels provided 4,700 kWh of power used within the building and an additional 2,900 kWh exported to the microgrid. The solar-produced power used within the building nearly offsets the estimated annual electrical draw of the heat pump of 5,700 kWh. Due to the very high costs for shipping and installation to remote locations, projects such as this, while not economically feasible if self-funded, can save the community an estimated $76,051 over a period of 20-years. Fuel prices increasing by more than 25%, or subsidized electricity prices decreasing by more than 25%, make the ground source heat pump a more viable option economically. Unsubsidized electricity prices increasing by 25% or more make a solar photovoltaic system with battery storage nearly economically viable after a 20-year period for commercial or school buildings that are not eligible for Alaska's Power Cost Equalization program.

14 SOLAR ENERGY↗
DOE OSTI2024

Reaction Pathways and Energy Consumption in NH 3 Decomposition for H 2 Production by Low Temperature, Atmospheric Pressure Plasma

Pathways for NH 3 decomposition to N 2 and N 2 H 4 by atmospheric pressure nonthermal plasma are analyzed using a combination of molecular beam mass spectrometry measurements and zero-dimensional kinetic modeling. Experimental measurements show that NH 3 conversion and selectivity towards N 2 formation scale monotonically with the specific energy input into the plasma with ~ 100% selectivity to N 2 formation achieved at specific energy inputs above 0.12 J cm −3 (3.1 eV (molecule NH 3 ) −1 ). The kinetic model recovers these trends, although it underpredicts N 2 selectivity at low specific energy input. These discrepancies can be explained by the underestimation of reaction rate coefficients for reactions that consume N 2 H x species in collisions with H radicals and/or radial nonuniformities in power deposition, gas temperature, and species concentrations that are not represented by the plug flow approximation used in the model. The kinetic model shows that N 2 formation proceeds through N 2 H x decomposition pathways rather than NH x decomposition pathways in low temperature, atmospheric pressure plasma. Higher selectivity toward N 2 production can be achieved by operating at higher NH 3 conversion and with a higher gas temperature. Furthermore, the high energy cost of NH 3 decomposition by atmospheric pressure nonthermal plasma found in this work (25–50 eV (molecule NH 3 converted) −1 ; 17–33 eV (molecule H 2 formed) −1 ) is a result of the energy requirement for electron-impact dissociation of NH 3 and the significant re-formation of NH 3 by three-body recombination reactions between NH 2 and H.

Nonthermal plasma↗
NASA NTRS1975

Simulation of the velocity diffusion of charged particles in turbulent magnetic fields

Numerical simulation experiments have been performed in order to study the velocity diffusion of charged particles in a static turbulent magnetic field. By following orbits of particles moving in a large ensemble of random magnetic field realizations with suitably-chosen statistical properties, a pitch-angle diffusion coefficient is derived. Results are presented for a variety of particle rigidities and r.m.s. random field strengths and a power spectrum typical of conditions found in interplanetary space.

Kaiser, T. B.↗
NASA NTRS1979

Wear of aluminum and hypoeutectic aluminum-silicon alloys in boundary-lubricated pin-on disk sliding

The friction and wear of pure aluminum and a number of hypoeutectic aluminum-silicon alloys (with 3 to 12 wt %Si) were studied with a pin-on-disk apparatus. The contacts were lubricated with mineral oil and sliding was in the boundary-lubrication regime at 2.6 cm/sec. Surfaces were analyzed with photomicrographs, scanning electron microscopy, X-ray dispersive analysis, and diamond pyramid hardness measurements. There were two wear regimes for the alloys - high and low - whereas pure aluminum exhibited a high wear rate throughout the test period. Wear rate decreased and the transition stress from high to low wear increased with increasing hardness. There was no correlation between friction coefficient and hardness. A least squares curve fit indicated a wear-rate dependence greater than the inverse first power of hardness. The lower wear rates of the alloys may be due to the composites of silicon platelets in aluminum resulting in increased hardness and thus impairing the shear of the aluminum.

Ferrante, J.↗
NASA NTRS1993

FNAS/summer faculty fellowship research continuation program. Task 6: Integrated model development for liquid fueled rocket propulsion systems. Task 9: Aspects of model-based rocket engine condition monitoring and control

The objective of Phase I of this research effort was to develop an advanced mathematical-empirical model of SSME steady-state performance. Task 6 of Phase I is to develop component specific modification strategy for baseline case influence coefficient matrices. This report describes the background of SSME performance characteristics and provides a description of the control variable basis of three different gains models. The procedure used to establish influence coefficients for each of these three models is also described. Gains model analysis results are compared to Rocketdyne's power balance model (PBM).

Santi, L. Michael↗
NASA NTRS1959

Modified Matrix Method for Calculating Steady-State Span Loading on Flexible Wings in Subsonic Flight

A method is presented for shortening the computations required to determine the steady-state span loading on flexible wings in subsonic flight. The method makes use of tables of downwash factors to find the necessary aerodynamic-influence coefficients for the application of lifting-line theory. Explicit matrix equations of equilibrium are converted into a matrix power series with a finite number of terms by utilizing certain characteristic properties of matrices. The number of terms in the series is determined by a trial-and-error process dependent upon the required accuracy of the solution. Spanwise distributions of angle of attack, airload, shear, bending moment, and pitching moment are readily obtained as functions of qm(sub R) where q denotes the dynamic pressure and mR denotes the lift-curve slope of a rigid wing. This method is intended primarily to make it practical to solve steady-state aeroelastic problems on the ordinary manually operated desk calculators, but the method is also readily adaptable to automatic computing equipment.

Gainer, Patrick A.↗
NASA NTRS1996

Parameterizing the Raindrop Size Distribution

This paper addresses the problem of finding a parametric form for the raindrop size distribution (DSD) that(1) is an appropriate model for tropical rainfall, and (2) involves statistically independent parameters. Such a parameterization is derived in this paper. One of the resulting three "canonical" parameters turns out to vary relatively little, thus making the parameterization particularly useful for remote sensing applications. In fact, a new set of r drop-size-distribution-based Z-R and k-R relations is obtained. Only slightly more complex than power laws, they are very good approximations to the exact radar relations one would obtain using Mie scattering. The coefficients of the new relations are directly related to the shape parameters of the particular DSD that one starts with. Perhaps most important, since the coefficients are independent of the rain rate itself, the relations are ideally suited for rain retrieval algorithms.

Haddad, Ziad S.↗
NASA NTRS1999

Acoustic Reflection and Transmission of 2-Dimensional Rotors and Stators, Including Mode and Frequency Scattering Effects

A reduced order modeling scheme has been developed for the unsteady acoustic and vortical coupling between blade rows of a turbomachine. The essential behavior of the system is governed by modal scattering coefficients (i.e., reflection and transmission coefficients) of the rotor, stator, inlet and nozzle, which are calculated as if they were connected to non-reflecting ducts. The objective of this report is to identify fundamental behavior of these scattering coefficients for a better understanding of the role of blade row reflection and transmission in noise generation. A 2D flat plate unsteady cascade model is used for the analysis with the expectation that the general behavior presented herein will carry over to models that include more realistic flow and geometry. It is shown that stators scatter input waves into many modes at the same frequency whereas rotors scatter on frequency, or harmonic order. Important cases are shown here the rotor reflection coefficient is greater than unity; a mode at blade passing frequency (BPF) traveling from the stator with unit sound power is reflected by the rotor with more than unit power at 2xBPF and 3xBPE Analysis is presented to explain this unexpected phenomenon. Scattering curves are presented in a format chosen for design use and for physical interpretation. To aid in interpretation of the curves, formulas are derived for special condition where waveforms are parallel to perpendicular to the rotor.

Hanson, Donald B.↗
NASA NTRS1947

The Effect of High Solidity on Propeller Characteristics at High Forward Speeds from Wind-Tunnel Tests of the NACA 4-(3)(06.3)-06 and NACA 4-(3)(06.4)-09 Two-Blade Propellers

Tests of two-blade propellers having the NACA 4-(3)(06.3)-06 and NACA 4-(3)(06.4)-09 blade designs (blade activity factors of 179 and 263, respectively) have been made in the Langley 8-foot high-speed tunnel through a range of blade angle from 20 degrees to 70 degrees for free-stream Mach numbers from 0.165 to 0.725 to determine the effects of high solidity and compressibility on propeller characteristics. The tests are part of a general investigation of propellers at high forward speeds. Results previously reported for similar tests of two-blade propellers having the NACA 4-308-03 and NACA 4-308-045 blade designs (blade activity factors of 87 and 133, respectively) are included for comparison. The results showed that the 0.06- and 0.09-solidity blades, although producing efficiencies of the order of 90 percent, were less efficient than blades of conventional solidity. The variation in average blade lift coefficient with solidity at a constant blade angle and advance-diameter ratio through the speed range of these tests was found to be analogous to the variation of wing lift coefficient with aspect ratio, indicating that high-solidity blades may be desirable at very high speeds. Because of power limitations of the test equipment, conclusive evidence of the possible favorable effects of increased blade solidity at high speeds was not obtained. Further tests are desirable.

Delano, James B.↗
NASA NTRS2005

Quantitative Electron Probe Microanalysis: State of the Art

Quantitative electron-probe microanalysis (EPMA) has improved due to better instrument design and X-ray correction methods. Design improvement of the electron column and X-ray spectrometer has resulted in measurement precision that exceeds analytical accuracy. Wavelength-dispersive spectrometer (WDS) have layered-dispersive diffraction crystals with improved light-element sensitivity. Newer energy-dispersive spectrometers (EDS) have Si-drift detector elements, thin window designs, and digital processing electronics with X-ray throughput approaching that of WDS Systems. Using these systems, digital X-ray mapping coupled with spectrum imaging is a powerful compositional mapping tool. Improvements in analytical accuracy are due to better X-ray correction algorithms, mass absorption coefficient data sets,and analysis method for complex geometries. ZAF algorithms have ban superceded by Phi(pz) algorithms that better model the depth distribution of primary X-ray production. Complex thin film and particle geometries are treated using Phi(pz) algorithms, end results agree well with Monte Carlo simulations. For geological materials, X-ray absorption dominates the corretions end depends on the accuracy of mass absorption coefficient (MAC) data sets. However, few MACs have been experimentally measured, and the use of fitted coefficients continues due to general success of the analytical technique. A polynomial formulation of the Bence-Albec alpha-factor technique, calibrated using Phi(pz) algorithms, is used to critically evaluate accuracy issues and can be also be used for high 2% relative and is limited by measurement precision for ideal cases, but for many elements the analytical accuracy is unproven. The EPMA technique has improved to the point where it is frequently used instead of the petrogaphic microscope for reconnaissance work. Examples of stagnant research areas are: WDS detector design characterization of calibration standards, and the need for more complete treatment of the continuum X-ray fluorescence correction.

Carpernter, P. K.↗
DOE OSTI2025

Fuel cells for single-aisle regional aircraft: System configuration, performance and cost

A hydrogen fuel cell propelled electric aircraft can compete with incumbent turbofan technologies for single-aisle regional aircraft by coupling design of stack, air handling, thermal management, propulsion, and airframe to optimize performance. The stack operates at 95°C to facilitate heat rejection during take-off and below 75°C during cruise to extend lifetime and is oversized to satisfy power requirements at end of life. A multi-stage turbocompressor with a compression ratio >10 is selected to reach high stack power density at 11,300-m cruise altitude. The propulsion system is configured to accommodate air handling within the core duct, an inclined heat exchanger in the outer duct to limit the nacelle size, and variable area nozzles to independently control mass flows through the core and bypass ducts. The airframe is modified for maximum lift coefficient and longer balanced field length for dramatically reduced thrust during take-off, and the fuselage is stretched by 20% to store liquid hydrogen (LH 2 ). Modularization of power systems promotes safety in one engine inoperative scenarios and allows reaching specific power metrics for stack, balance-of-plant and fuel cell system (FCS), necessary for acceptable take-off weight. In conclusion, cost parity requires increase in FCS lifetime, LH 2 cost reduction, and improved FCS specific power.

Catalyst durability↗
NASA NTRS1985

Icing flight research: Aerodynamic effects of ice and ice shape documentation with stereo photography

Aircraft icing flight research was performed in natural icing conditions. A data base consisting of icing cloud measurements, ice shapes, and aerodynamic measurements is being developed. During research icing encounters the icing cloud was continuously measured. After the encounter, the ice accretion shapes on the wing were documented with a stereo camera system. The increase in wing section drag was measured with a wake survey probe. The overall aircraft performance loss in terms of lift and drag coefficient changes was obtained by steady level speed/power measurements. Selective deicing of the airframe components was performed to determine their contributions to the total drag increase. Engine out capability in terms of power available was analyzed for the iced aircraft. It was shown that the stereo photography system can be used to document ice shapes in flight and that the wake survey probe can measure increases in wing section drag caused by ice. On one flight, the wing section drag coefficient (c sub d) increased approximately 120 percent over the uniced baseline at an aircraft angle of attack of 6 deg. On another flight, the aircraft darg coefficient (c sub d) increased by 75 percent over the uniced baseline at an aircraft lift coefficient (C sub d) of 0.5.

Mikkelsen, K. L.↗
NASA NTRS1985

Icing flight research - Aerodynamic effects of ice and ice shape documentation with stereo photography

Aircraft icing flight research was performed in natural icing conditions. A data base consisting of icing cloud measurements, ice shapes, and aerodynamic measurements is being developed. During research icing encounters the icing cloud was continuously measured. After the encounter, the ice accretion shapes on the wing were documented with a stereo camera system. The increase in wing section drag was measured with a wake survey probe. The overall aircraft performance loss in terms of lift and drag coefficient changes were obtained by steady level speed/power measurements. Selective deicing of the airframe components was performed to determine their contributions to the total drag increase. Engine out capability in terms of power available was analyzed for the iced aircraft. It was shown that the stereo photography system can be used to document ice shapes in flight and that the wake survey probe can measure increases in wing section drag caused by ice. On one flight, the wing section drag coefficient (c sub d) increased approximately 120 percent over the uniced baseline at an aircraft angle of attack of 6 deg. On another flight, the aircraft drag coefficient (c sub d) increased by 75 percent over the uniced baseline at an aircraft lift coefficient (c sub d) of 0.5.

Mikkelsen, K. L.↗
DOE OSTI2020

Design, Analysis, Comparison, and Experimental Validation of Insulated Metal Substrates for High-Power Wide-Bandgap Power Modules

Direct bonded copper (DBC) substrates used in power modules have limited heat spreading and manufacturing capability due to ceramic properties and manufacturing technology. The ceramic and copper bonding is also subject to high mechanical stress due to coefficient of thermal expansion mismatch between the copper and the ceramic. For wide-bandgap (WBG) devices, it is of interest exploring new substrate technologies that can overcome some of the challenges of direct bonded copper substrates. In this technical paper, the design, analysis, and comparison of insulated metal substrates (IMSs) for high-power wide-bandgap semiconductor-based power modules are discussed. This paper starts with technical description and discussion of state-of-the-art DBC substrates with different ceramic insulators such as aluminum nitride (AlN), Al 2 O 3 , and Si 3 N 4 . Next, an introduction of IMSs and their material properties, and a design approach for SiC (silicon carbide) metal-oxide-semiconductor field-effect transistor (MOSFET)-based power modules for high-power applications is provided. The influence of dielectric thickness on the power handling capability of the substrate are also discussed. The designed IMS and DBC substrates were characterized in terms of steady-state and transient thermal performance using finite element simulation. Finally, the performance of the IMS and DBC are validated in an experimental setup under different loading and cooling temperature conditions. We report the simulation and experimental results showed that the IMS can provide high steady-state thermal performance for high-power modules based on SiC MOSFETs. Furthermore, the IMS provided enhanced transient thermal performance, which provided a reduced junction temperature when the module is operated at low fundamental output frequencies in traction drive systems.

42 ENGINEERING↗
DOE OSTI2020

Analysis of Planar-Cavity Receiver Reactor for Solar Thermochemical Dry-Reforming

Concentrating solar thermal (CST) systems can be leveraged to provide not only heat for power generation, but also for energy storage and thermochemical fuel production. Such solar thermochemical processes have been studied conceptually, from solar thermochemical hydrogen production (STCH) and thermochemical energy storage (TCES), to gasification, reforming, and fuel upgrading by various means. The solar receiver and reactor are critical components in the conversion of solar energy into chemical energy in the form of 'solar fuels'. For effective conversion of solar energy within a coupled solar receiver-reactor, extremely high temperatures are required, thereby demanding a high solar concentration ratio (CR) for efficient operation. This creates a design challenge for the receiver-reactor, as many thermochemical processes involve gas or gas-solid systems that are limited by low heat transfer coefficients. A unique receiver design is proposed that has the potential to incorporate various high-temperature thermochemical processes such as TCES-assisted power generation, methane reforming, or STCH processes. Modeling this receiver and its potential applications requires a full three-dimensional model that accurately captures the interconnected effects of receiver geometry, spatial solar irradiance, complex radiation, reaction kinetics, fluid dynamics, and heat transfer. In this paper we analyze a CST system integrated with this unique planar-cavity receiver-reactor design using the developed model. The model presented in this paper showed where improved thermal management was needed to achieve suitable receiver performance when a dry-methane reforming process is implemented.

14 SOLAR ENERGY↗
DOE OSTI2021

Ultralow Thermal Conductivity, Multiband Electronic Structure and High Thermoelectric Figure of Merit in TlCuSe

The entanglement of lattice thermal conductivity, electrical conductivity, and Seebeck coefficient complicates the process of optimizing thermoelectric performance in most thermoelectric materials. Semiconductors with ultralow lattice thermal conductivities and high power factors at the same time are scarce but fundamentally interesting and practically important for energy conversion. In this work, an intrinsic p-type semiconductor TlCuSe that has an intrinsically ultralow thermal conductivity (0.25 W m -1 K -1 ), a high power factor (11.6 μ W cm -1 K -2 ), and a high figure of merit, ZT (1.9) at 643 K is described. The weak chemical bonds, originating from the filled antibonding orbitals p-d* within the edge-sharing CuSe 4 tetrahedra and long Tl-Se bonds in the PbClF-type structure, in conjunction with the large atomic mass of Tl lead to an ultralow sound velocity. Strong anharmonicity, coming from Tl + lone-pair electrons, boosts phonon-phonon scattering rates and further suppresses lattice thermal conductivity. The multiband character of the valence band structure contributing to power factor enhancement benefits from the lone-pair electrons of Tl + as well, which modify the orbital character of the valence bands, and pushes the valence band maximum off the Gamma-point, increasing the band degeneracy. The results provide new insight on the rational design of thermoelectric materials.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Flow reversal benchmark of a one-sided heated narrow rectangular channel with CATHARE and RELAP5

Flow reversal in narrow coolant channels can be a crucial phenomenon for the safety of research reactors with a downward nominal flow direction. During a loss of forced flow accident, the downward flow stagnates briefly before transitioning into an upward natural circulation flow. The fuel may be damaged if dryout occurs and threshold fuel and/or cladding temperatures are exceeded. A comprehensive study is provided for flow reversal in narrow rectangular channels by examining experimental data and conducting software model analyses. The literature on flow reversal was reviewed, and selected experimental datasets were used to benchmark against CATHARE and RELAP5 models and also compare the code calculations with each other. The experimental data comes from flow reversal tests conducted with a narrow rectangular channel with one-sided heating. The results were compared with experimental data for successful flow reversal tests and predicted dryout power for dryout conditions. Also, the study examined the effects of the pump coastdown period, inlet liquid temperature, system pressure, and localized pressure drops. The experimental results showed that shorter coastdown periods, reduced pressure drops, and lower coolant inlet temperatures increased the dryout power. However, the system pressure did not noticeably affect the results. The simulation results showed that both CATHARE and RELAP5 agreed with experimental data, capturing the trends of the experimental results. Slight differences between each code calculation, as well as the predicted and measured dryout powers, were attributed to experimental uncertainties and the modeling of physical phenomena such as wall nucleation, interfacial heat transfer, drag coefficients, and critical heat flux. Overall, this study provides an understanding of flow reversal and the prediction capabilities of thermal-hydraulics software models. In conclusion, a future study of the flow reversal benchmark of a narrow rectangular channel with two-sided heating may provide additional valuable insights.

CATHARE↗