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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 1,351 records · Page 75
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Heat-Transfer Characteristics of Partially Film Cooled Plug Nozzle on a J-85 Afterburning Turbojet Engine

Plug nozzle film cooling data were obtained downstream of a slot located at 42 percent of the total plug length on a J-85 engine. Film cooling reduced the aft end wall temperature as much as 150 K, reduced total pressure loss in the upstream convection cooling passages by 50 percent, and reduced estimated compressor bleed flow requirement by 14 percent compared to an all convectively cooled nozzle. Shock waves along the plug surface strongly influenced temperature distributions on both convection and film cooled portions. The effect was most severe at nozzle pressure ratios below 10 where adverse pressure gradients were most severe.

Nosek, S. M.↗
NASA NTRS1976

Resizing procedure for optimum design of structures under combined mechanical and thermal loading

An algorithm is reported for resizing structures subjected to combined thermal and mechanical loading. The algorithm is applicable to uniaxial stress elements (rods) and membrane biaxial stress members. Thermal Fully Stressed Design (TFSD) is based on the basic difference between mechanical and thermal stresses in their response to resizing. The TFSD technique is found to converge in fewer iterations than ordinary fully stressed design for problems where thermal stresses are comparable to the mechanical stresses. The improved convergence is demonstrated by example with a study of a simplified wing structure, built-up with rods and membranes and subjected to a combination of mechanical loads and a three dimensional temperature distribution.

Adelman, H. M.↗
NASA NTRS1975

Dynamics of plankton populations in upwelling areas

The author has identified the following significant results. Spectral properties of the upwelled waters off the NW coast of Africa were studied with observations derived from aircraft and Skylab. Results indicate that the two-channel, ratio approach is ineffective in determining surface chlorophyll concentrations. Ocean color boundaries and temperature gradients were found to be directly correlated with each other and also with fishing effort in the upwelling region. Photographic and scanner data derived from Skylab were effective in locating ocean boundaries and mapping temperature distributions.

Szekielda, K. H.↗
NASA NTRS1976

Three dimensional thrust chamber life prediction

A study was performed to analytically determine the cyclic thermomechanical behavior and fatigue life of three configurations of a Plug Nozzle Thrust Chamber. This thrust chamber is a test model which represents the current trend in nozzle design calling for high performance coupled with weight and volume limitations as well as extended life for reusability. The study involved the use of different materials and material combinations to evaluate their application to the problem of low-cycle fatigue in the thrust chamber. The thermal and structural analyses were carried out on a three-dimensional basis. Results are presented which show plots of continuous temperature histories and temperature distributions at selected times during the operating cycle of the thrust chamber. Computed structural data show critical regions for low-cycle fatigue and the histories of strain within the regions for each operation cycle.

Armstrong, W. H.↗
NASA NTRS1976

Study of mesoscale phenomena, winter monsoon clouds and snow area based on LANDSAT data

The author has identified the following significant results. Most longitudinal clouds which appear as continuous linear clouds are composed of small transversal clouds. There are mountain waves of different wavelength in a comparatively narrow area indicating complicated orographical effects on wind and temperature distribution or on both dynamical and static stability condition. There is a particular shape of cirrus cloud suggestive of turbulence in the vicinity of CAT in the upper troposphere near jet stream level and its cold air side. Thin cirrus of overcast condition can be distinguished by MSS; however, extremely thin cirrus of partly cloudy condition cannot be detected even in LANDSAT data. This presents a serious problem in the interpretation of satellite thermal infrared radiation data since they affect the value.

Tsuchiya, K.↗
NASA NTRS1976

High performance flat plate solar collector

The potential use of porous construction is presented to achieve efficient heat removal from a power producing solid and is applied to solar air heaters. Analytical solutions are given for the temperature distribution within a gas-cooled porous flat plate having its surface exposed to the sun's energy. The extracted thermal energy is calculated for two different types of plate transparency. Results show the great improvement in performance obtained with porous flat plate collectors as compared with analogous nonporous types.

Lansing, F. L.↗
NASA NTRS1976

Solar cell grid patterns

A grid pattern is described for a solar cell of the type which includes a semiconductive layer doped to a first polarity and a top counter-doped layer. The grid pattern comprises a plurality of concentric conductive grids of selected geometric shapes which are centered about the center of the exposed active surface of the counter-doped layer. Connected to the grids is one or more conductors which extend to the cell's periphery. For the pattern area, the grids and conductors are arranged in the pattern to minimize the maximum distance which any injected majority carriers have to travel to reach any of the grids or conductors. The pattern has a multiaxes symmetry with respect to the cell center to minimize the maximum temperature differentials between points on the cell surface and to provide a more uniform temperature distribution across the cell face.

Yasui, R. K.↗
NASA NTRS1975

Open-loop response of a burning liquid monopropellant

A direct comparison was obtained between the theoretical and experimental response of a burning liquid monopropellant surface to imposed pressure oscillations. The comparison extended beyond the quasi-steady frequency regime into the range where the combustion process interacts with the thermal wave in the liquid phase. The theory considered both gas and liquid-phase transient effects, involving a numerically integrated, first-order perturbation analysis. The experiment employed hydrazine as the test fuel, burning as a strand. With kinetic parameters fixed by steady burning rate measurements, the model gave good predictions of liquid-phase temperature distributions during steady combustion as well as the amplitude and phase of the oscillatory component of the burning rate in the presence of imposed pressure oscillations. The combustion response tends to peak in two frequency ranges; one corresponding to interaction with liquid-phase transient effects, which could be verified both theoretically and experimentally; the second corresponding to gas-phase transient effects, which could only be examined theoretically. Both ranges provide conditions where the amplifying power is sufficient to drive combustion instability.

Allison, C. B.↗
NASA NTRS1975

Thermomechanical coupling in fatigue fracture of viscoelastic materials

Subcritical crack growth in a linear viscoelastic material subjected to cyclic loading is investigated starting with the thermodynamic power balance. Physically, it is supposed that the subcritical slow crack growth is due to local weakening of the material in the neighborhood of the crack tip. Under fatigue loading it is assumed that all energy dissipation goes into heat and that this heat build-up is the dominant irreversible process governing crack growth. The cycle averaged temperature distribution around the crack tip is obtained from local application of the first law of thermodynamics (i.e., conservation of energy). The analysis leads to the solution of a nonlinear integro-differential equation for crack length as a function of time which is coupled with the local energy equation. A regular perturbation technique is used to obtain an analytical solution which compares very well with experimental results.

Hufferd, W. L.↗
NASA NTRS1976

Laminar free convection from a vertical cone with uniform surface heat flux

The laminar free convection flow from a right circular cone with prescribed uniform wall flux condition is studied. The governing boundary-layer equations are analyzed by the technique of similarity transformation. Numerical solutions to the transformed equations are given for Prandtl numbers 0.72, 1, 2, 4, 6, 8, 10, and 100. Expressions for both wall temperature distribution and wall skin friction distribution at Prandtl number tending to infinity are also presented.

Lin, F. N.↗
NASA NTRS1975

Induced anisotropy of thermal conductivity of polymer solids under large strains

A simple analytical form of induced anisotropy of heat conductivity of initially isotropic polymer solids results from employing the simplified theory of the three-chain model of the non-Gaussian network. The analytical form appears to be valid up to a stretch ratio of 2.65, which is the limit of existing experimental data. The effect of induced anisotropy on the temperature distribution, due to the large deformations, is illustrated for a highly expanded spherical shell and a cylindrical tube under a steady-state heat flow using the derived analytical form of the strain-dependent heat conductivity.

Peng, S. T. J.↗
NASA NTRS1976

Ground test of the D shaped vented thrust vectoring nozzle

Static ground tests of a large scale lift/cruise thrust vectoring nozzle were conducted to establish: (1) vectoring performance 'in' and 'out' of ground effect; (2) thrust spoilage capability; (3) compatibility of the nozzle with a turbotip fan; and (4) the nozzle structural temperature distribution. Vectoring performance of a short coupled, vented nozzle design on a large scale, (60%) basis was compared with small scale (4.5%) test nozzle results. The test nozzle was a "boilerplate" model of the MCAIR "D" vented nozzle configured for operation with the LF336/J85 turbotip lift fan system. Calibration of the LF336/J85 test fan with a simple convergent nozzle was performed with four different nozzle exit areas to establish reference thrust, nozzle pressure ratio, and nozzle corrected flow characteristics for comparison with the thrust vectoring nozzle data. Thrust vectoring tests with the 'D' vented nozzle were conducted over the range of vector angles between 0 and 117 deg for several different nozzle exit areas.

Esker, D. W.↗
NASA NTRS1976

Design features and operational characteristics of the Langley 0.3-meter transonic cryogenic tunnel

Experience with the Langley 0.3 meter transonic cryogenic tunnel, which is fan driven, indicated that such a tunnel presents no unusual design difficulties and is simple to operate. Purging, cooldown, and warmup times were acceptable and were predicted with good accuracy. Cooling with liquid nitrogen was practical over a wide range of operating conditions at power levels required for transonic testing, and good temperature distributions were obtained by using a simple liquid nitrogen injection system. To take full advantage of the unique Reynolds number capabilities of the 0.3 meter transonic tunnel, it was designed to accommodate test sections other than the original, octagonal, three dimensional test section. A 20- by 60-cm two dimensional test section was recently installed and is being calibrated. A two dimensional test section with self-streamlining walls and a test section incorporating a magnetic suspension and balance system are being considered.

Kilgore, R. A.↗
NASA NTRS1976

TAP 1: A Finite Element Program for Steady-State Thermal Analysis of Convectively Cooled Structures

The program has a finite element library of six elements: two conduction/convection elements to model heat transfer in a solid, two convection elements to model heat transfer in a fluid, and two integrated conduction/convection elements to represent combined heat transfer in tubular and plate/fin fluid passages. Nonlinear thermal analysis due to temperature dependent thermal parameters is performed using the Newton-Raphson iteration method. Program output includes nodal temperatures and element heat fluxes. Pressure drops in fluid passages may be computed as an option. A companion plotting program for displaying the finite element model and predicted temperature distributions is presented. User instructions and sample problems are presented in appendixes.

Thornton, E. A.↗
NASA NTRS1976

Thermal design and analysis of a hydrogen-burning wind tunnel model of an airframe-integrated scramjet

An aerodynamic model of a hydrogen burning, airframe integrated scramjet engine has been designed, fabricated, and instrumented. This model is to be tested in an electric arc heated wind tunnel at an altitude of 35.39 km (116,094 ft.) but with an inlet Mach number of 6 simulating precompression on an aircraft undersurface. The scramjet model is constructed from oxygen free, high conductivity copper and is a heat sink design except for water cooling in some critical locations. The model is instrumented for pressure, surface temperature, heat transfer rate, and thrust measurements. Calculated flow properties, heat transfer rates, and surface temperature distributions along the various engine components are included for the conditions stated above. For some components, estimates of thermal strain are presented which indicate significant reductions in plastic strain by selective cooling of the model. These results show that the 100 thermal cycle life of the engine was met with minimum distortion while staying within the 2669 N (600 lbf) engine weight limitation and while cooling the engine only in critical locations.

Guy, R. W.↗
NASA NTRS1976

Oscillations and stability of numerical solutions of the heat conduction equation

The mathematical model and results of numerical solutions are given for the one dimensional problem when the linear equations are written in a rectangular coordinate system. All the computations are easily realizable for two and three dimensional problems when the equations are written in any coordinate system. Explicit and implicit schemes are shown in tabular form for stability and oscillations criteria; the initial temperature distribution is considered uniform.

Kozdoba, L. A.↗
NASA NTRS1977

Performance tests with a 4.75 inch bore tapered-roller bearings at high speeds

The tapered-roller bearings were tested at speeds to 15,000 rpm which results in a cone-rib tangential velocity of 130 m/sec. (25,500 ft/min). Lubrication was applied either by jets or directly to the cone-rib, augmented with jets. Additional test parameters included thrust loads to 53,400 N (12,000 lbs), radial loads to 26,700 N (6,000 lbs), lubricant flow rates from 1.9 x 0.000 to 15.1 x 0.001 cubic meter/min. (0.5 to 4.0 gpm), and lubricant inlet temperatures of 350 K and 364 K (170 F and 195 F). Temperature distribution, separator speed, and drive-motor power demand were determined as functions of these test parameters.

Signer, H. R.↗
NASA NTRS1976

Umbral boundaries, convection, and the depth of sunspots

The boundary between the umbra and penumbra of a sunspot is consistently observed to be very sharp, on the order of 500 km. Approximating the sunspot as a static region in a homogeneous medium with a radiative surface, temperature distributions resulting from a variety of convective motions exterior to the sunspot are calculated. The calculations suggest that, for the exterior convection to produce the observed boundary, the maximum depth of the region of inhibited convection below a sunspot umbra is on the order of 1,000 km.

Isenberg, P. A.↗