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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 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Some optical and kinetic properties of the nearby interstellar gas

A model for resonant scattering of sunlight by the nearby interstellar gas is developed which takes into account the modification of a Maxwell-Boltzmann velocity distribution by a central force. While the formalism applies to both hydrogen and helium, the latter is emphasized. Theoretical line profiles and integrated emission rates for helium are compared with those of approximate models and with existing observations. As a result of this analysis, an upward revision of the bulk flow velocity of interstellar helium relative to the solar system, previously deduced from He 584-A observations, is required. Velocities of 15-20 km/s, temperatures of the order of 5000-10,000 K, and densities of the order of 0.008-0.02 per cu cm are sufficient to explain the (helium) observations. However, higher-precision measurements are required in order to place more stringent limits on the gas parameters. Calculations of the flux of interstellar helium atoms impinging on earth's upper atmosphere show that the resulting impact ionization is small compared with terrestrial processes.

Meier, R. R.↗
NASA NTRS1977

Computation of the temperature distribution in cooled radial inflow turbine guide vanes

A two-dimensional finite-difference numerical technique is presented to determine the temperature distribution of an internally-cooled blade of radial turbine guide vanes. A simple convection cooling is assumed inside the guide vane. Such an arrangement results in relatively small cooling effectiveness at the leading edge and at the trailing edge. Heat transfer augmentation in these critical areas may be achieved by using impingement jets and film cooling. A computer program is written in Fortran IV for IBM 370/165 computer.

Tabakoff, W.↗
NASA NTRS1977

Comparison of flare bremsstrahlung resulting from energetic thermal and nonthermal electrons

The paper investigates the behavior of the X-ray bremsstrahlung spectra resulting from two distinct types of electron distribution functions impinging on a target atmosphere during flare activity. A power-law distribution function is compared with two double-peaked Maxwellians. The results of these calculations show that it would be difficult to rule out multithermal interpretations for the emitted high-energy X-rays.

Davis, J.↗
NASA NTRS1977

Fluctuating loads on the flap surfaces of an externally-blown-flap configuration

An experimental program to obtain the fluctuating loads on the surfaces of a triple-slotted externally-blown-flap powered-lift STOL configuration was conducted. A large model of a wing/flap system and a TF-34 medium bypass ratio engine was investigated. Measurements of the fluctuating pressure, static pressure, and surface temperature resulting from the jet impingement were obtained at several locations on the surfaces of the second and third flaps. Fluctuating pressure data include overall level, power-spectral density (PSD), cross-correlation coefficient, coherency, and phase angle of the cross power-spectral density. These data indicate that more than one mechanism contributes to the fluctuating pressure levels on the flaps. In the immediate area above the intersection of the engine centerline and the flap, low frequency pressures dominate the overall fluctuating pressure levels. In other areas, such as below this intersection and outboard on the flaps, the PSD curve reaches a peak value at a Strouhal number ranging from 0.22 to 0.45.

Schoenster, J. A.↗
NASA NTRS1977

Surface fluctuating pressure measurements on a 1/4-scale YC-14 boilerplate model

A research program is conducted for the study of the fluctuating loads imposed on both upper-surface blown-flap and externally blown-flap powered-lift STOL aircraft configurations by the impingement of the jet engine exhaust flow. Attention is given to the measurement of the unsteady pressures at 30 positions in the vicinity of the jet exhaust on the surface of a NASA 1/4-scale YC-14 boilerplate wing and fuselage section.

Pappa, R. S.↗
NASA NTRS1977

Flare heating by energetic nonthermal electrons

A model has been developed which includes, in a self-consistent fashion, the energy degradation and attendant bremsstrahlung emission of a high-energy electron beam, heating of a flare plasma by the beam, and subsequent cooling by thermal conduction and radiation. To assist in the interpretation of experimental diagnostics, the model also characterizes the radiative behavior of iron ions present in the flare plasma. Electron deposition is described by the Fokker-Planck equation for an initial power-law particle distribution. Results are presented for the bremsstrahlung radiation emitted by the incident beam as it impinges on the disturbed atmosphere. A comparison is made between direct beam heating and thermal-conduction heating of the flare plasma. The radiation emitted by several selected spectral lines of Fe ions is determined as a function of time during and after deposition

Davis, J.↗
NASA NTRS1977

Measurements in the turbulent boundary layer with slot injection of helium

Hot-wire anemometry and digital techniques are used to develop time series for the streamwise and transverse velocity components and for the mass fraction of helium in the low-speed turbulent boundary layer of air involving the slot injection of helium. Profiles are developed at several streamwise stations. In the present contribution the data are presented principally in terms of conventional, unconditioned averages. It is found that the mean velocity and concentration profiles develop in the downstream direction in the expected fashion but that the intensities of the velocity, concentration, and density fluctuations increase sharply downstream of the slot and peak in the region where the mixing region from the splitter plate impinges on the wall. Close to the wall where the helium concentration is relatively high counterfluxes of helium are found.

Larue, J. C.↗
NASA NTRS1977

Upper surface blowing aerodynamic and acoustic characteristics

Aerodynamic performance at cruise, and noise effects due to variations in nacelle and wing geometry and mode of operation are studied using small aircraft models that simulate upper surface blowing (USB). At cruise speeds ranging from Mach .50 to Mach .82, the key determinants of drag/thrust penalties are found to be nozzle aspect ratio, boattailing angle, and chordwise position; number of nacelles; and streamlined versus symmetric configuration. Recommendations are made for obtaining favorable cruise configurations. The acoustic studies, which concentrate on the noise created by the jet exhaust flow and its interaction with wing and flap surfaces, isolate several important sources of USB noise, including nozzle shape, exit velocity, and impingement angle; flow pathlength; and flap angle and radius of curvature. Suggestions for lessening noise due to trailing edge flow velocity, flow pathlength, and flow spreading are given, though compromises between some design options may be necessary.

Ryle, D. M., Jr.↗
NASA NTRS1977

Graphite grain surface reactions in interstellar and protostellar environments

Surface reactions on warm (at least 60 K) graphite grains between lattice C atoms and impinging H and O atoms within or in the vicinity of H II regions can provide a prolific source of H2CO and other interstellar molecules. It is proposed that similar reactions in the primitive solar nebula led to the formation of the organic molecules found in carbonaceous chondrites. From this and related evidence, it is argued that most of the solid material in the solar system may have originated as interstellar grains.

Barlow, M. J.↗
NASA NTRS1977

Acoustic loads on upper-surface-blown powered-lift systems

Powered-lift concepts are utilized in aircraft currently under development for STOL application. One of the concepts, upper surface blowing, places the jet exit just above the upper surface of the wing to produce powered lift from the jet exhaust blowing over the deflected flap. New data are presented to show the effects of airspeed, angle of attack, and angle of jet impingement. Scaling relationships are investigated concerning their applicability for extrapolating data to a different model size. The effects of a number of test parameters are examined and full-scale spectra are predicted from model data. It is concluded that scale models are an effective means for obtaining fluctuating pressure spectra for use in aircraft design. The prediction of full-scale loads from model data will require geometrically accurate models and closely spaced measurement locations.

Willis, C. M.↗
NASA NTRS1977

Noise characteristics of upper surface blown configurations. Experimental program and results

An experimental data base was developed from the model upper surface blowing (USB) propulsive lift system hardware. While the emphasis was on far field noise data, a considerable amount of relevant flow field data were also obtained. The data were derived from experiments in four different facilities resulting in: (1) small scale static flow field data; (2) small scale static noise data; (3) small scale simulated forward speed noise and load data; and (4) limited larger-scale static noise flow field and load data. All of the small scale tests used the same USB flap parts. Operational and geometrical variables covered in the test program included jet velocity, nozzle shape, nozzle area, nozzle impingement angle, nozzle vertical and horizontal location, flap length, flap deflection angle, and flap radius of curvature.

Brown, W. H.↗
NASA NTRS1977

An investigation of temperature distribution in cooled guide vanes

A numerical study to determine the temperature distribution in the guide vane blades of a radial inflow turbine is presented. A computer program was developed which permits the temperature distribution to be calculated when the blade is cooled internally using a combination of impingement and film cooling techniques. The study is based on the use of the finite difference method in a two dimensional heat conduction problem. The results are then compared to determine the best cooling configuration for a certain coolant to primary mass flow ratio.

Kotwal, R.↗
NASA NTRS1977

The multiple applications of electrons in space

An electron source such as a simple cathode is a cheap and light device which can serve several technological and scientific purposes in space: (1) electrostatic charging of a spacecraft can be limited by releasing electrons accumulated on the conductive elements of their surface; (2) the erosion of conductive coatings and the ability of conductive paints to withstand the space environment can be evaluated by monitoring the flow of charged particles impinging on their surface; (3) measuring the current collected by the spacecraft surface as a function of its potential with respect to an emitter is a very sensitive diagnostic technique which can yield a number of plasma parameters, such as density and temperature; (4) it is possible to convert the thermal motion of space plasmas into electrical energy by collecting energetic electrons and returning them to the medium as cold particles; (5) a wave in a plasma is characterized by a conduction current density which gives rise to fluctuations of the current flowing to the surface.

Grard, R. J. L.↗
NASA NTRS1976

Wind-tunnel investigation of aerodynamic performance, steady amd vibratory loads, surface temperatures, and acoustic characteristics of a large-scale twin-engine upper-surface blown jet-flap configuration

Static and wind-on tests were conducted to determine the aerodynamic characteristics of and the effects of jet impingement on the wing of a large scale upper surface blown configuration powered with an actual turbine engine. The wing and flaps were instrumented with experimental dual-sensing transducer units consisting of a fluctuating pressure gage, a vibratory accelerometer, and a surface mounted alumel thermocouple. Noise directivity and spectral content measurements were obtained for various flap configurations and various engine thrust settings to provide baseline noise data for other upper surface blown configurations.

Source record↗
NASA NTRS1978

Predicted inlet gas temperatures for tungsten fiber reinforced superalloy turbine blades

Tungsten fiber reinforced superalloy composite (TFRS) impingement cooled turbine blade inlet gas temperatures were calculated taking into account material spanwise strength, thermal conductivity, material oxidation resistance, fiber-matrix interaction, and coolant flow. Measured values of TFRS thermal conductivities are presented. Calculations indicate that blades made of 30 volume percent fiber content TFRS having a 12,000 N-m/kg stress-to-density ratio while operating at 40 atmospheres and a 0.06 coolant flow ratio could permit a turbine blade inlet gas temperature of over 1900K. This is more than 150K greater than similar superalloy blades.

Winsa, E. A.↗
NASA NTRS1978

Preliminary design of an Orbiter/IUS separation sequence

An orbiter/IUS separation sequence to satisfy the assumed requirements of Shuttle Flight 8 was defined for the purpose of gaining an insight into the flight design software requirements. The key to economical and effective flight design for orbiter/IUS proximity operations is considered to be the capability for rapid and accurate generation of graphical displays that will facilitate not only decision making on the part of the designer, but also lucid documentation of rationale and the resulting design features. The data indicate that (1) an OMS burn is required to attain the necessary velocity without subjecting the IUS and its payload to undue plume impingement, and (2) a departure trajectory that places the orbiter above and behind the IUS at SRM ignition time is preferred over the alternative which would place it below and ahead.

Wilson, S. W.↗
NASA NTRS1978

Combustor concepts for aircraft gas turbine low-power emissions reduction

Several combustor concepts were designed and tested to demonstrate significant reductions in aircraft engine idle pollutant emissions. Each concept used a different approach for pollutant reductions: the hot wall combustor employs a thermal barrier coating and impingement cooled liners; the recuperative cooling combustor preheats the air before entering the combustion chamber; and the catalytic converter combustor is composed of a conventional primary zone followed by a catalytic bed for pollutant cleanup. The designs are discussed in detail and test results are presented for a range of aircraft engine idle conditions. The results indicate that ultralow levels of unburned hydrocarbons and carbon monoxide emissions can be achieved.

Mularz, E. J.↗
NASA NTRS1978

Dust adhesion on Viking lander camera window

Studies of dust impingement on a duplicate Viking Lander camera window indicated the possibility of window obscuration after several days of exposure even at low dust concentration levels. As a result the following corrective measures were recommended: (1) The clearance between the housing surface and the camera post should be eliminated by using an appropriately designed plastic skirt: (2) The three horizontal ledges below the window inside the cavity act as bases for pile-up of dust that slides down the window surface; they should be replaced by a single inclined plane down which the dust will slide and fall out on the ground: (3) Adhered dust on the window surface can be removed by high pressure CO2 jets directed down against the window; the amount of CO2 gas needed for the entire mission can be carried in a 3 1/2-inch diameter sphere equipped with a remotely programable valve. These measures were incorporated in the design of the lander camera system. The continued high quality of photographs transmitted from the Viking spacecraft several months after landing attests to their effectiveness.

Singh, J. J.↗