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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Mean flow characteristics for the oblique impingement of an axisymmetric jet

The oblique impingement of an axisymmetric jet has been investigated. A summary of the data and the analytical interpretations of the dominant mechanisms which influence the flow are reported. The major characteristics of the shallow angle oblique jet impingement flow field are: (1) minimal dynamic spreading as revealed by the surface pressure field, (2) pronounced kinematic spreading as revealed by the jet flow velocity field, (3) a pronounced upstream shift of the stagnation point from the maximum pressure point, (4) the production of streamwise vorticity by the impingement process.

Foss, J. F.↗
NASA NTRS2006

3-D GRMHD Simulations of Disk-Jet Coupling and Emission

We have performed a fully 3-D GRMHD simulation of jet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The simulation results show that a bipolar jet is initially created. At later times, the accretion disk becomes thick and the jet fades resulting in a wind that is ejected from the surface of the thickened (torus-like) disk. This evolution of disk-jet coupling suggests that the jet fades with a thickened accretion disk. Recently we have developed two new codes: 3 -D GRMHD: RelAtivIStic magnetoHydrodynamica1 sImulatioN (RAISHIN) code constructed by modern high-resolution shock-capturing (HRSC) techniques and 3-D GRPIC code. We have calculated free-free and synchrotron emission from the disks and jet/outflows obtained from our GRMHD simulations using a fully covariant radiative transfer formulation.

Nishikawa, K.-I.↗
NASA NTRS1972

Wind-tunnel investigation at low speeds of a model of the Kestrel (XV-6A) vectored-trust V/STOL airplane

Longitudinal and lateral stability data were obtained with the model out of and in ground effect over a moving ground plane for a range of model angles of attack and sideslip at various thrust coefficients. These data were taken primarily at thrust coefficients which simulate transition speeds on the airplane between hover and 200 knots. Some data, however, represent the effect of thrust deflection at speeds up to 350 knots. Also presented are the effects of control-surface deflections and interference between the jets and free stream.

Margason, R. J.↗
NASA NTRS1973

Effect of gage size on the measurement of local heat flux

General formulas are derived for determining gage averaging errors of strip-type heat flux meters used in the measurement of one-dimensional heat flux distributions. In addition, a correction procedure is presented which allows a better estimate for the true value of the local heat flux. As an example of the technique, the formulas are applied to the cases of heat transfer to air slot jets impinging on flat and concave surfaces. It is shown that for many practical problems, the use of very small heat flux gages is often unnecessary.

Baumeister, K. J.↗
NASA NTRS1973

Aerodynamic characteristics of a large-scale model with a swept wing and a jet flap having an expandable duct

The data from an investigation of the aerodynamic characteristics of the expandable duct-jet flap concept are presented. The investigation was made using a large-scale model in the Ames 40- by 80-foot Wind Tunnel. The expandable duct-jet flap concept uses a lower surface, split flap and an upper surface, Fowler flap to form an internal, variable area cavity for the blowing air. Small amounts of blowing are used on the knee of the upper surface flap and the knee of a short-chord, trailing edge control flap. The bulk of the blowing is at the trailing edge. The flap could extend the full span of the model wing or over the inboard part only, with blown ailerons outboard. Primary configurations tested were two flap angles, typical of takeoff and landing; symmetric control flap deflections, primarily for improved landing performance; and asymmetric aileron and control flap deflections, for lateral control.

Aiken, T. N.↗
NASA NTRS1974

A review of air transport noise

Flight vehicles are characterized according to their manner of operation and type of propulsion system, and their associated sources of noise are identified. Available noise reduction technology as it relates to engine cycle design and to power plant component design is summarized. Such components as exhaust jets, fans, propellers, rotors, airflow-surface interactions, and reciprocating engine exhausts are discussed, along with their noise reduction potentials. Significant aircraft noise reductions are noted to have been accomplished by the application of available technology in support of noise certification rules. Improved analytical prediction methods, and well controlled validation experiments supported by advanced design aeroacoustic facilities, are required as a basis for an effective integrated systems approach to aircraft noise control.

Hubbard, H. H.↗
NASA NTRS1976

A theoretical investigation of over-wing-blowing aerodynamics

A theoretical method is established for determining the aerodynamic characteristics of over-wing-blowing configurations. The method accounts for both jet entrainment and jet interaction effects because of the differences in freestream and jet dynamic pressures and Mach numbers. The predicted lift increments agree well with available data. It is shown that the lift is underpredicted with entrainment effect alone when the jet is close to the wing surface.

Lan, C. E.↗
NASA NTRS1976

Oil-air mist lubrication for helicopter gearing

The applicability of a once-through oil mist system to the lubrication of helicopter spur gears was investigated and compared to conventional jet spray lubrication. In the mist lubrication mode, cooling air was supplied at 366K (200 F) to the out of mesh location of the gear sets. The mist air was also supplied at 366K (200 F) to the radial position mist nozzle at a constant rate of 0.0632 mol/s (3 SCFM) per nozzle. The lubricant contained in the mist air varied between 32 - 44 cc/hour. In the recirculating jet spray mode, the flow rate was varied between 1893 - 2650 cc/hour. Visual inspection revealed the jet spray mode produced a superior surface finish on the gear teeth but a thermal energy survey showed a 15 - 20% increase in heat generated. The gear tooth condition in the mist lubrication mode system could be improved if the cooling air and lubricant/air flow ratio were increased. The test gearbox and the procedure used are described.

Mcgrogan, F.↗
NASA NTRS1979

In situ oxygen conditioning of /001/ MgO thin film substrates for film growth studies by electron microscopy

It was found that the in situ treatment of 001-plane single-crystal films of MgO (prepared by epitaxial growth from the vapor phase) at high temperatures with a jet of oxygen will produce a surface that is almost equivalent, for epitaxial studies, to surfaces with the same orientation prepared by vacuum cleavage of bulk single crystals. The effectiveness of the process is demonstrated by its impact on the epitaxy of silver.

Moorhead, R. D.↗
NASA NTRS1979

An investigation of corner separation within a thrust augmenter having Coanda jets

The development of separation in corners of thrust augmentor wings having Coanda jets was investigated using hot film surface sensors and pressure transducers. Separation on the test augmentor began at a corner very close to the augmentor exit and then rapidly proceeded upstream. Measurements of the pressure fields in the corner region indicated that a modified form of the Stratford criterion could be used to predict the onset of separation. Testing was conducted over a range of nozzle pressure ratios, aspect ratios, diffuser angles, and designs of the boundary layer and Coanda nozzles.

Seiler, M. R.↗
NASA NTRS1980

Experimental Study of the Stability of Aircraft Fuels at Elevated Temperatures

An experimental study of fuel stability was conducted in an apparatus which simulated an aircraft gas turbine fuel system. Two fuels were tested: Jet A and Number 2 Home Heating oil. Jet A is an aircraft gas turbine fuel currently in wide use. No. 2HH was selected to represent the properties of future turbine fuels, particularly experimental Reference Broad Specification, which, under NASA sponsorship, was considered as a possible next-generation fuel. Tests were conducted with varying fuel flow rates, delivery pressures and fuel pretreatments (including preheating and deoxygenation). Simulator wall temperatures were varied between 422K and 672K at fuel flows of 0.022 to 0.22 Kg/sec. Coking rate was determined at four equally-spaced locations along the length of the simulator. Fuel samples were collected for infrared analysis. The dependence of coking rate in Jet A may be correlated with surface temperature via an activation energy of 9 to 10 kcal/mole, although the results indicate that both bulk fluid and surface temperature affect the rate of decomposition. As a consequence, flow rate, which controls bulk temperature, must also be considered. Taken together, these results suggest that the decomposition reactions are initiated on the surface and continue in the bulk fluid. The coking rate data for No. 2 HH oil are very highly temperature dependent above approximately 533K. This suggests that bulk phase reactions can become controlling in the formation of coke.

Vranos, A.↗
NASA NTRS1986

Powder Extinguishants for Jet-Fuel Fires

Mixtures of alkali metal dawsonite and metal halide show superior performance. In tests of new dry powder fire extinguishants, mixtures of potassium dawsonite with either stannous iodide or potassium iodide found effective for extinguishing jet-fuel fires on hot metal surfaces (up to 900 degrees C). Mixtures performed more effectively than either compound alone.

Altman, R. L.↗
NASA NTRS1987

Corrosion of SiC by Molten Salt

Advanced ceramic materials considered for wide range of applications as in gas turbine engines and heat exchangers. In such applications, materials may be in corrosive environments that include molten salts. Very corrosive to alloys. In order to determine extent of problem for ceramic materials, corrosion of SiC by molten salts studied in both jet fuel burners and laboratory furnaces. Surface of silicon carbide corroded by exposure to flame seeded with 4 parts per million of sodium. Strength of silicon carbide decreased by corrosion in flame and tube-furnace tests.

Jacobson, Nathan S.↗
NASA NTRS1986

Two blowing concepts for roll and lateral control of aircraft

Two schemes to modulate aerodynamic forces for roll and lateral control of aircraft have been investigated. The first scheme, called the lateral blowing concept, consists of thin jets of air exiting spanwise, or at small angle with the spanwise direction, from slots at the tips of straight wings. For this scheme, in addition to experimental measurements, a theory was developed showing the analytical relationship between aerodynamic forces and jet and wing parameters. Experimental results confirmed the theoretically derived scaling laws. The second scheme, which was studied experimentally, is called the jet spoiler concept and consists of thin jets exiting normally to the wing surface from slots aligned with the spanwise direction.

Tavella, D. A.↗
NASA NTRS1987

Fluctuating pressure loads under high speed boundary layers

Aeroacoustic fatigue is anticipated to control the design of significant portions of the structures of high-speed vehicles. This is due to contemplated long-duration flights at high dynamic pressures and Mach numbers with related high skin temperatures. Fluctuating pressure loads are comparatively small beneath attached turbulent boundary layers, but become important in regions of flow separation such as compression and expansion corners on elevons and rudders. The most intense loads are due to shock/boundary-layer interaction. These flows may occur in the engine-exhaust wall jet and in flows over control surfaces. A brief review is given of available research in these areas with a description of work under way at Langley Research Center.

Zorumski, William E.↗
NASA NTRS1990

Shock interference heating in scramjet engines

Experimental and analytical research sponsored by the NASA Langley Research center and the NASP Structures Technology Maturation Program to define critical aerothermal loads for the NASP engine is summarized. Presented is a review of (1) shock-shock interaction on the engine cowl leading edge that results in a supersonic jet impinging on the leading edge surface and causes the heat transfer rate to be amplified by a factor of 30 or more over the undisturbed (no shock interaction) flow stagnation point heat transfer rate, (2) the effectiveness of supersonic film cooling with and without the effects of an impinging oblique shock wave, and (3) oblique shock impingement in an axial compression corner.

Wieting, Allan R.↗
NASA NTRS1992

The thermal structure, dust loading, and meridional transport in the Martian atmosphere during late southern summer

We have derived a comprehensive picture of the thermal structure and dust loading of the Martian atmosphere in a relatively clear period during late southern summer. Using a new technique for the simultaneous retrieval of atmospheric temperatures and airborne dust abundances, we examined a subset of the Mariner 9 infrared interferometer spectrometer (IRIS) thermal emission spectra spanning L sub s = 343 degrees to 348 degrees. Global maps of temperature and dust optical depth as functions of latitude (plus or minus 90 degrees), altitude (approx. 0-60 km), and Mars local time of day were constructed from the profiles from individual spectra. One of the principal conclusions from this work is that both dayside and nightside atmospheric temperatures at altitudes above about 40 km are warmer over the winter (north) polar regions than over the equator or the summer (south) polar regions. These anomalous temperatures are consistent with ground-based observations of polar warming at higher altitudes (50-85 km), and they indicate that the atmosphere is not in radiative equilibrium. Zonal-mean zonal winds are derived from the observed meridional gradients of the zonally averaged temperatures assuming geostrophy and zero surface zonal wind. The intense eastward jets (with velocities exceeding 120 m/s) correspond to regions of strong horizontal temperature gradients. Similar calculations have been reported previously, but they were not global in coverage. Both the zonal-mean meridional circulation and large-scale waves contribute to the north-south atmospheric transport.

Santee, M.↗