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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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Instrumentation for airbreathing propulsion; Proceedings of the Symposium, U.S. Naval Postgraduate School, Monterey, Calif., September 19-21, 1972

New developments and refinements in measuring techniques used for both ground testing and in-flight control, diagnosis, and monitoring of airbreathing combustors are analyzed in a number of papers. Some of the techniques studied include the application of laser velocimeters for flow measurements; on-the-shaft data systems for rotating engine components; total pressure averaging in pulsating flows; fiber optic and laser digital pressure transducers; holography of nozzles, jets, and spraying systems; application of the Raman effect fo flowfield diagnostics; holography of JP-4 droplets and combusting boron particles; the use of a laser-powered optical proximity probe in advanced turbofan engine development; pyrometry for measurement of surface temperature distribution on a rotating turbine blade; an ultrasonic turbine inlet gas temperature sensor; automatic detection and suppression of inlet buzz; and electrostatic probes for sensing incipient engine failure. Individual items are announced in this issue.

Fuhs, A. E.↗
NASA NTRS1951

Analysis of Meteorological Data Obtained During Flight in a Supercooled Stratiform Cloud of High Liquid-Water Content

Flight icing-rate data obtained in a dense and. abnormally deep supercooled stratiform cloud system indicated the existence of liquid-water contents generally exceeding values in amount and extent previously reported over the midwestern sections of the United States. Additional information obtained during descent through a part of the cloud system indicated liquid-water contents that significantly exceeded theoretical values, especially near the middle of the cloud layer.. The growth of cloud droplets to sizes that resulted in sedimentation from the upper portions of the cloud is considered to be a possible cause of the high water contents near the center of the cloud layer. Flight measurements of the vertical temperature distribution in the cloud layer indicated a rate of change of temperature with altitude exceeding that of the moist adiabatic lapse rate. This excessive rate of change is considered to have contributed to the severity of the condition.

Perkins, Porter J.↗
NASA NTRS1985

SSME fuel preburner phase 1/phase 2+ comparison

An analytical comparison of the predicted combustion flowfields for the Phase 1 and Phase 2+ fuel preburner configurations using an advanced CFD combustion code is currently underway at Rocketdyne. The Phase 2+ injector has a modified element design. The redesigned element provides for improved atomization through a shift in the injector element/face bleed flow split while maintaining an acceptable pressure drop. Cold-flow tests of the new design have been encouraging. As a complement to those tests, the Advanced Rocket Injector Combustor Code (ARICC) was selected to conduct a detailed combustion flowfield simulation. ARICC models two-dimensional (or axisymmetric), transient, turbulent, two-phase mixing and combustion flowfields. It is derived from a member of the Los Alamos ICEd-ALE family of codes. Unique features of ARICC include explicit representation of the coaxial LOX jet and hydrogen gas flows, distributed atomization processes, droplet breakup, and supercritical vaporation processes. Predictions of temperature and OH concentration profiles for the Phase 1 and Phase 2+ injector flowfields indicate a trend toward more uniform temperature distributions and shorter flame lengths with the Phase 2+ design.

Jensen, R. J.↗
NASA NTRS1990

Vibrations of rectangular plates with moderately large initial deflections at elevated temperatures using finite element method

A finite-element formulation is developed for the free vibration of rectangular plates which are under the influence of moderately large stress-free initial deflections and large thermal deflections. The von Karman nonlinear strain-displacement relations are used to account for the thermal deflections. The plates are thin, isotropic, and Hookean in nature. The temperature imposed on the plate is assumed to be constant through the thickness of the plate. Uniform and sinusoidal temperature distributions are studied. The material properties of the plates are temperature-dependent due to the relatively high temperatures imposed on the plates.

Gray, C. C.↗
NASA NTRS1990

The three-dimensional distribution of atmospheric heating during the GWE

The large-scale three-dimensional time-averaged distribution of heating and its temporal evolution as determined from the European Center for Medium-range Weather Forecasts (ECMWF) Global Weather Experiment (GWE) Level IIIb data set are examined. Global distributions of vertically averaged heating for January, April, July, and October 1979 are presented to illustrate the seasonal evolution of the planetary pattern. Horizontal distributions of heating and vertical profiles from various climatological regimes of the planetary circulation are given and provide insight into the four-dimensional structure of the thermal forcing of the atmosphere. Major features of the global distributions include heating in regions of deep moist convection over places such as South America. Seasonal meridional and zonal heating migration are discussed and it is noted that zonal migration is linked with planetary scale distribution of continents and oceans and the land-sea surface temperature distribution. Various degrees of heating in the troposphere and their consequences are investigated.

Schaack, Todd K.↗
NASA NTRS1993

Temperature Gradients on the Cell Wall in the Critical Viscosity Experiment

Because of the diverging susceptibility delta rho/delta Tau near the liquid-vapor critical point, temperature gradients must be kept small to maintain adequate sample homogeneity. In our Science Requirements Document we paid particular attention to radial density gradients caused by equilibration of the xenon sample. Axial density gradients were addressed through the requirement that the cell's copper wall have a gradient less than 22 microK/m. This report re-examines the cell wall's temperature distribution in more detail by estimating all known significant contributions to temperature differences on the cell's wall.

Berg, Robert F.↗
DOE OSTI2023

EXPERIMENTAL ANALYSIS OF SINGLE EVAPORATION TUBE UTILIZING SINTERED COPPER PARTICLE WICKING STRUCTURES

Wicking structures have been widely used within passive heat transfer devices with high heat fluxes, such as heat pipes, to enhance their thermal performance. While wicking structures promote capillary pumping of the working fluid as well as thin film evaporation, they can result in capillary evaporation and further enhances the evaporation heat transfer. In this study, a 0.5 mm thick layer of 105 microns sintered copper particles was added to the inner wall of a copper tube, aiming to enhance the heat transfer characteristics by taking advantage of capillary evaporation. Acetone was chosen as the working fluid, and the performance of an evaporation tube was tested for power inputs of 10, 30, 50, and 70 W. For each power input, trials were run at inclination angles varying from -90° and 90° to investigate the capillary effects. The temperature measurements showed that the temperature distribution along the evaporation tube is always downward sloping, meaning the temperature at the fluid inlet is larger than the outlet. Interestingly, the surface temperature at some locations is less than the outlet temperature, indicating the effect of capillary evaporation. In addition, a theoretical investigation was performed to investigate the effects of the particle size on the thermal performance of the evaporation tube and found that particle sizes affect capillary evaporation.

Wang, Pengtao↗
NASA NTRS1991

Thermographic monitoring of materials under simulated reentry conditions

Thermography can be used to measure surface temperature gradients graphically, and can be used under conditions where the direct measurement of temperature at all desired points, using thermocouples or resistance temperature detectors (RTDs), is either difficult or impossible. The use of thermographic monitoring during a series of arc-jet tests is described. Described in this work are the issues that influence interpretation of the thermographic measurements under these conditions, including the calculation of effective emittance and window transmittance from the spectral properties of the materials in order to calculate the temperature distribution of a surface directly from the measured radiance. Comparison of the surface temperatures measured using thermocouples and the temperatures derived from thermographic measurements show good agreement. The data gathered will be used to evaluate important test parameters such as the heating distribution across the surface of a heat shield test model and at steps on the model surface.

White, Susan M.↗
NASA NTRS1993

Numerical model for the Programmable Multirole Furnace (PMZF)

The present account of the Programmable Multizone Furnace numerical model uses various examples to illustrate the ways in which the model serves as an optimization, test, prediction, and visualization tool; a numerical PID-control algorithm obtains the desired sample temperature distributions and allows the model to solve an inverse heat transfer problem where the desired sample temperature profile is the input and the required heater power distribution is the output of numerical simulations. Parametric studies show how the total power consumption of the furnace is affected by such design variables as the conductivity.

Kassemi, M.↗
NASA NTRS1981

The distribution of maximum temperatures of coronal active region loops

Starting with the integrated emission measure distributions of solar active regions, the distribution of the maximum temperature parameter which characterizes individual plasma loops is determined. The observed emission measure distributions were determined by combining EUV and X-ray data from two separate experiments on ATM/Skylab. The present work sets some limits on such an approach. It is found that the distribution of maximum temperature has approximately the same shape as the integrated emission measure distributions, a result which is expected since most of the loop emission measure is near their maximum temperatures.

Teske, R. G.↗
NASA NTRS1979

Thermal structure and relaxation rates of the perturbed atmosphere - A study with a photochemical radiative convective model

A radiative-photochemical model is developed to evaluate the temperature distribution in the earth's atmosphere between the ground and 70 km. The model takes into account the interaction between photochemistry and temperature. Results are reported for a number of experiments performed with this model to assess the climatic effects of varying the ozone distribution and the ozone overburden. An evaluation of the relaxation rates of both ozone and temperature is also reported. In particular, the importance of the ozone distribution with respect to the greenhouse effect is further investigated.

Alimandi, G.↗
DOE OSTI2022

Three-dimensional electron temperature measurement of inertial confinement fusion hotspots using x-ray emission tomography

Here we present a novel approach to reconstruct three-dimensional (3D) electron temperature distributions of inertially confined fusion plasma hotspots at the National Ignition Facility. Using very limited number of two-dimensional (2D) x-ray imaging lines of sight, we perform 3D reconstructions of x-ray emission distributions from different x-ray energy channels ranging from 20 to 30 keV. 2D time-integrated x-ray images are processed using the algebraic reconstruction technique to reconstruct a 3D hotspot x-ray emission distribution that is self-consistent with the input images. 3D electron temperatures are computed using the energy channel ratios. We demonstrate the high accuracy and applicability of this method with different complex hotspot geometries in both synthetic and experimental results.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1971

Development of a High Temperature Heater using an Yttria Stabilized Zirconia Cored Brick Matrix

The Ames pilot heater is a ceramic regenerative heater that provides high temperature air for aerodynamic and combustion experiments. The development of this heater to provide a heat storage bed with temperature capability of about 4600 R is described. A bed was designed and installed having cored brick elements of yttria-stabilized zirconia. The bed dimensions were 14 inches in diameter by 10 feet high. The thermal stress limitations of the bed were studied and maximum air flow rates based upon these limits were established. A combustion reheat system was designed and installed to provide the necessary control over the bed temperature distribution. The revised heater system was successfully operated at a maximum bed temperature of 4600 R. The successful operation demonstrated that yttria-stabilized zirconia cored brick can satisfy the high temperature-long duration requirement for storage heater applications.

Smith, K. W.↗
NASA NTRS1972

Anode heat transfer for a flowing argon plasma at elevated electron temperature.

Theoretical investigation of heat transfer from a preionized gaseous plasma flowing over an anode surface at an elevated electron temperature in the presence of an electric field normal to the surface. A laminar boundary layer is considered in which only the velocity profile is locally similar and fluid properties are assumed to change uniformly in the gas flow direction. Results obtained by an approximation method show that for moderate current densities, the velocity and temperature distributions are insensitive to current. In addition, the effect of elevated electron temperature is negligible on convective heat transfer, but is significant for the overall heat transfer due to the enthalpy transport by current. Total heat flux to the anode is obtained by evaluating the Nusselt number and adding terms due to the potential drop in the sheath and the surface work function.

Bose, T. K.↗
NASA NTRS1976

Chemical vapor deposition growth

A chemical vapor deposition (CVD) reactor system with a vertical deposition chamber was used for the growth of Si films on glass, glass-ceramic, and polycrystalline ceramic substrates. Silicon vapor was produced by pyrolysis of SiH4 in a H2 or He carrier gas. Preliminary deposition experiments with two of the available glasses were not encouraging. Moderately encouraging results, however, were obtained with fired polycrystalline alumina substrates, which were used for Si deposition at temperatures above 1,000 C. The surfaces of both the substrates and the films were characterized by X-ray diffraction, reflection electron diffraction, scanning electron microscopy optical microscopy, and surface profilometric techniques. Several experiments were conducted to establish baseline performance data for the reactor system, including temperature distributions on the sample pedestal, effects of carrier gas flow rate on temperature and film thickness, and Si film growth rate as a function of temperature.

Ruth, R. P.↗
NASA NTRS1976

A two-dimensional finite difference solution for the transient thermal behavior of tubular solar collector

A numerical procedure was established using the finite-difference technique in the determination of the time-varying temperature distribution of a tubular solar collector under changing solar radiancy and ambient temperature. Three types of spatial discretization processes were considered and compared for their accuracy of computations and for selection of the shortest computer time and cost. The stability criteria of this technique was analyzed in detail to give the critical time increment to ensure stable computations. The results of the numerical analysis were in good agreement with the analytical solution previously reported. The numerical method proved to be a powerful tool in the investigation of the collector sensitivity to two different flow patterns and several flow control mechanisms.

Lansing, F. L.↗
NASA NTRS1977

Studies of heat-source driven natural convection: A numerical investigation

Thermal convection driven by uniform volumetric energy sources was studied in a horizontal fluid layer bounded from above by a rigid, isothermal surface and from below by a rigid, zero heat-flux surface. The side walls of the fluid domain were assumed to be rigid and perfectly insulating. The computations were formally restricted to two-dimensional laminar convection but were carried out for a range of Rayleigh numbers which spans the regimes of laminar and turbulent flow. The results of the computations consists of streamline and isotherm patterns, horizontally averaged temperature distributions, and horizontally averaged Nusselt numbers at the upper surface. Flow and temperature fields do not exhibit a steady state, but horizontally averaged Nusselt numbers reach limiting, quasi-steady values for all Rayleigh numbers considered. Correlations of the Nusselt number in terms of the Rayleigh and Prandtl numbers were determined.

Emara, A. A.↗