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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 1,423 records · Page 79

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NASA NTRS1981

Analysis of JP-4 fire test data and development of a simple fire model

A series of field experiments involving JP-4 fires of 7.6m dia and 15.2m dia was conducted under the sponsorship of NASA. The temperature inside the fire, the specie composition and vertical axial velocity were measured at several height locations and radial positions. The peak temperature recorded is 1400-1500 K; the velocities at 6m height are 11-12 m/s. The oxygen-to-nitrogen mass ratio along the vertical axis was found to be nearly a constant at 0.05. Significant necking of the fire was observed. A simple theoretical model was developed that predicts the experimental data on the velocity and vertical temperature distribution well. The model is based on the partial combustion of entrained air and assumed top-hat distributions for various property and flow parameters inside the fire. Quantitative agreement is obtained by using a value of 0.15 for the entrainment coefficient and 0.45 for the mixing efficiency factor. The model also predicts the fire necking.

Raj, P. K.↗

NASA NTRS1981

Ground test of a large scale 'D' vented thrust deflecting nozzle

Future V/STOL aircraft will require efficient techniques for changing the thrust vector from the vertical direction for VTOL operation to the horizontal direction for conventional flight. Most V/STOL concepts utilize thrust vectoring nozzles to provide this variation in the thrust vector direction. An experimental test program was initiated to demonstrate the capabilities of a large scale 'D' vented thrust deflecting system coupled with a high bypass ratio turbofan engine. Data were obtained for a 'D' vented nozzle mounted behind a YTF-34-F5 turbofan engine. Preliminary data are presented for a variety of test conditions. Attention is given to aspects of 'D' vented nozzle design, the test apparatus, engine-nozzle compatibility, exit area variation, longitudinal vectoring performance, nozzle temperature distribution, and large scale - small scale comparisons.

Rosenberg, E. W.↗

NASA NTRS1982

Extended adiabatic blast waves and a model of the soft X-ray background

The suggestion has been made that much of the soft X-ray background observed in X-ray astronomy might arise from being inside a very large supernova blast wave propagating in the hot, low-density component of the interstellar (ISM) medium. An investigation is conducted to study this possibility. An analytic approximation is presented for the nonsimilar time evolution of the dynamic structure of an adiabatic blast wave generated by a point explosion in a homogeneous ambient medium. A scheme is provided for evaluating the electron-temperature distribution for the evolving structure, and a procedure is presented for following the state of a given fluid element through the evolving dynamical and thermal structures. The results of the investigation show that, if the solar system were located within a blast wave, the Wisconsin soft X-ray rocket payload would measure the B and C band count rates that it does measure, provided conditions correspond to the values calculated in the investigation.

Cox, D. P.↗

NASA NTRS1982

Integrated finite element thermal-structural analysis with radiation heat transfer

An integrated approach for efficiently coupling thermal and stress analyses of structures with radiation heat transfer is presented. A new integrated one dimensional element based on a nodeless variable formulation is introduced. Lumped and consistent formulations of the nonlinear radiation heat transfer matrix are presented. The accuracy of the integrated approach is assessed by comparisons with analytical solutions and conventional finite element thermal-structural analyses. Results show that the nodeless variable thermal element yields accuracy equivalent to a higher order element but permits a common discretization with a lower order congruent structural element. The integrated element thus provides improved accuracy and efficiency of thermal stress analysis for structures with complex temperature distributions.

Thornton, E. A.↗

NASA NTRS1982

Neutron star evolutionary sequences

Detailed numerical calculations which are solutions of the full set of general relativistic equations describing the evolution of a spherical star are presented, for the case of the evolution of neutron stars that are cooling over the central temperatures range of 10 to the 10th to 10 to the 7th K. The effects of nucleon superfluidity in the inner crust and core are included, and models are constructed with and without a pion condensate at high densities. It is found that the localized neutrino cooling which dominates the early evolution of neutron stars is so rapid that heat transport within the star cannot keep pace, and temperature distribution is not isothermal. The residual contraction of the neutron star during the early cooling phase contributes little to the heat budget of the star, and most of the gravitational energy released raises the Fermi energy of the degenerate nucleons. It is concluded that since calculations with and without pion condensate are consistent with the upper limits of current observations, these are not sufficient in distinguishing between the various models of neutron star cooling.

Richardson, M. B.↗

NASA NTRS1980

View angle effects in the radiometric measurement of plant canopy temperatures

The thermal infrared sensor response from a wheat canopy was extremely non-Lambertian because of spatial variations in energy flow processes; the effective radiant temperature of the sensor varied as much as 13 C with changing view angle. This variation of sensor response was accurately quantified (root-mean-square of deviations between theoretical and measured responses reduced to 1.1 C) as a function of vegetation canopy geometry, vertical temperature distribution of canopy components, and sensor view angle. The results have important implications for optimizing sensor view angles for remote sensing missions.

Kimes, D. S.↗

NASA NTRS1982

Aerodynamic interactions with turbulent jet exhaust plumes

The importance of aerodynamic interactions associated with external flow-field effects on turbulent jet exhaust plume structure is discussed. A viscous/inviscid prediction technique is presented which combines the overlaid mixing and inviscid plume components of the JANNAF Standardized Plume Flow-Field (SPF) model with inviscid external flow and boundary-layer analyses for treating nozzle afterbodies at subsonic/transonic speeds. Validation of the technique via comparisons between predictions and experiment for cold-air jet plumes is presented. Predicted spatial temperature distributions for hot, nonafterburning plumes are presented and compared to results obtained from more simplified prediction techniques in order to assess the importance of the aerodynamic interactions associated with external boundary layers and pressure gradients. It is demonstrated that these interactions play a significant role in determining the near-field turbulent mixing and inviscid plume shock structure. The implication of these results to plume radiation predictions is discussed.

Wilmoth, R. G.↗

NASA NTRS1981

Stratospheric ozone and temperature perturbations - An examination of synergistic effects

Experiments have been carried out to investigate the time-dependent effects of combined releases of CO2 and chlorofluoromethanes (CFM) on stratospheric ozone and temperature. The analysis also examines the effects of steady-state variations in CFM, CO2, and solar UV flux levels on surface temperature and latitudinal temperature distribution. Results indicate that ozone depletion, due to combined effects of CO2 and CFM increases, may show a local maximum of about 6% at about the time CO2 doubles (approximately 60 yr from now). After that, the downward trend in ozone due to Cl(x) catalytic destruction is reestablished and continues, reaching approximately 15% depletion. At steady state, compensation due to CO2 increases is approximately 1% for two to four times the ambient CO2 levels.

Callis, L. B.↗

NASA NTRS1982

Non-radial flow near the cometary surface

It is shown that, as a consequence of the non-uniform temperature distribution of the cometary nucleus, large lateral pressure gradients are set up, which in turn drive strong lateral flows. However, at small heliocentric distances the onset of turbulence within a thin boundary layer destroys these steady lateral flows and the eventual outflow of gas from within the outer boundary of this layer is expected to be more or less radial. On the other hand, at large heliocentric distances, turbulence is unlikely to set in, and the lateral flows that are set up, may persist. Consequently, it is expected that the gas flow out of the cometary nucleus at these large distances to be highly non-radial.

Marconi, M. L.↗

NASA NTRS1981

Submarine fresh water outflow detection with a dual-frequency microwave and an infrared radiometer system

Since infrared measurements are only very slightly affected by whitecap and banking angle influences, the combined multifrequency radiometric signatures of the L-band, the S-band, and an infrared radiometer are used in identifying freshwater outflows (submerged and superficial). To separate the river and lagoon outflows from the submarine outflows, geographical maps with a scale of 1:100,000 are used. In all, 44 submarine freshwater springs are identified. This is seen as indicating that the submarine freshwater outflow locations are more numerous around the island than had earlier been estimated. Most of the submarine springs are located at the northwest and southeast portion of the Puerto Rican coastline; the success in detecting the submarine springs during both missions at the northwest portion of the island is 39%. Salinity and temperature distribution plots along the flight path in longitude and latitude coordinates reveal that runoff direction can be determined.

Blume, H.-J. C.↗

NASA NTRS1982

Heat generation in aircraft tires under free rolling conditions

A method was developed for calculating the internal temperature distribution in an aircraft tire while free rolling under load. The method uses an approximate stress analysis of each point in the tire as it rolls through the contact patch, and from this stress change the mechanical work done on each volume element may be obtained and converted into a heat release rate through a knowledge of material characteristics. The tire cross-section is then considered as a body with internal heat generation, and the diffusion equation is solved numerically with appropriate boundary conditions of the wheel and runway surface. Comparison with data obtained with buried thermocouples in tires shows good agreement.

Clark, S. K.↗

NASA NTRS1982

Dilution Jet Mixing Program, phase 1

The effect of jet to mainstream density ratio, flow area convergence as encounted in transition sections, and nonuniform mainstream profile upstream of dilution orifices on the mixing of a row of jets with a confined cross flow was quantified. It is found that: (1) jet spreading rate in transverse direction is increased with increasing J, H/D and with decreasing S/D; (2) the density ratio has only a second order effect on the jet mixing characteristics for a constant momentum ratio; (3) the temperature distributions in the jet mixing region are strongly influenced by the undisturbed mainstream profile; (4) flow area convergence enhances mixing in radial and transverse directions. An asymmetric convergent duct with flat wall injection has the same jet mixing characteristics as a symmetric convergent duct. An asymmetric convergent duct with slant wall injection has a faster jet spreading rate in the transverse direction.

Srinivasan, R.↗

NASA NTRS1982

Modification and evaluation of a Barnes-type objective analysis scheme for surface meteorological data

The Purdue Regional Objective Analysis of the Mesoscale (PROAM) is a Barness-type scheme for the analysis of surface meteorological data. Modifications are introduced to the original version in order to increase its flexibility and to permit greater ease of usage. The code was rewritten for an interactive computer environment. Furthermore, a multiple iteration technique suggested by Barnes was implemented for greater accuracy. PROAM was subjected to a series of experiments in order to evaluate its performance under a variety of analysis conditions. The tests include use of a known analytic temperature distribution in order to quantify error bounds for the scheme. Similar experiments were conducted using actual atmospheric data. Results indicate that the multiple iteration technique increases the accuracy of the analysis. Furthermore, the tests verify appropriate values for the analysis parameters in resolving meso-beta scale phenomena.

Smith, D. R.↗

NASA NTRS1983

Heat generation in aircraft tires

Clark, S. K.↗

NASA NTRS1983

Results from recent NASA tire thermal studies

The testing technique and some results from an experimental study to determine tire temperature profiles to aid in defining the strength and fatigue limitations of the tire carcass structure are described. This effort is part of a program to explore analytically and through experiment the temperature distribution in an aircraft tire during free roll and braked and yawed rolling conditions.

Mccarty, J. L.↗

NASA NTRS1983

The Application of the Implicit Alternating-direction Numerical Technique to Thermal Analysis Involving Conduction and Convection

A computerized model was developed for analyzing the temperature distribution of a two dimensional body which is located at or near the soil surface and is partially exposed to solar radiation. The body may have one or more interior cavities containing air or another fluid. The methodology which evolved is also applicable to a general class of thermal analyses involving a body surrounded by a semi-infinite medium exposed to surface radiation energy. The theoretical analysis, numerical procedure, and a sample case are discussed.

Hughes, R. D.↗

NASA NTRS1983

Dilution Jet Experiments in Compact Combustor Configurations

The effects of cooling jets on the velocity and temperature fields in a compact reverse flow combustion are discussed. The work is motivated by the need to limit the temperature of past-combustion gases in jet engines to values within the endurance capabilities of turbine blades. The application requires not only that the temperature be kept sufficiently low but also that a suitably tailored temperature profile be provided at the combustor exit, with higher temperatures generally permissible at the blade tip than at the blade root because of higher centrifugal loads at the root. A single jet. As spacing is reduced, jet penetration is also reduced, and the cooling jets tend to remain close to the wall from which they are injected. Results suggest that cooling and temperature distribution tailoring can be accomplished without injecting cooling jets upstream of the turn, and thus it appears that combustors can be made smaller than current designs.

Greber, I.↗

NASA NTRS1983

Large-area sheet task advanced dendritic web growth development

Modeling in the development of low stress configurations for wide web growth is presented. Parametric sensitivity to identify design features which can be used for dynamic trimming of the furnace element was studied. Temperature measurements of experimental growth behavior led to modification in the growth system to improve lateral temperature distributions.

Duncan, C. S.↗