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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Design and test of porous-tungsten mercury vaporizers.

Future use of large size Kaufman thrusters and thruster arrays will impose new design requirements for porous plug type vaporizers. Larger flow rate coupled with smaller pores to prevent liquid intrusion will be desired. This paper presents the results of testing samples of porous tungsten for flow rate, liquid intrusion pressure level, and mechanical strength. Nitrogen gas was used in addition to mercury flow for approximate calibration. Liquid intrusion pressure levels will require that flight thruster systems with long feed lines have some way (a valve) to restrict dynamic line pressures during launch.

Kerslake, W. R.↗
NASA NTRS1974

Evaluation of analytical procedures for prediction of turbulent boundary layers on a porous wall

An analytical study has been made to determine how well current boundary layer prediction techniques work when there is mass transfer normal to the wall. The data that were considered in this investigation were for two-dimensional, incompressible, turbulent boundary layers with suction and blowing. Some of the bleed data were taken in an adverse pressure gradient. An integral prediction method was used three different porous wall skin friction relations, in addition to a solid-surface relation for the suction cases. A numerical prediction method was also used. Comparisons were made between theoretical and experimental skin friction coefficients, displacement and momentum thicknesses, and velocity profiles. The integral method with one of the porous wall skin friction laws gave very good agreement with data for most of the cases considered. The use of the solid-surface skin friction law caused the integral to overpredict the effectiveness of the bleed. The numerical techniques also worked well for most of the cases.

Towne, C. E.↗
NASA NTRS1975

Skin friction reduction in supersonic flow by injection through slots, porous sections and combinations of the two

An experimental study of skin friction reduction in a Mach 3.0 air steam with gaseous injection through a tangential slot, a porous wall section, and combinations of the two was conducted. The primary data obtained were wall shear values measured directly with a floating element balance and also inferred from Preston Tube measurements. Detailed profiles at several axial stations, wall pressure distributions and schlieren photographs are presented. The data indicate that a slot provides the greatest skin friction reduction in comparison with a reference flat plate experiment. The porous wall section arrangement suffers from an apparent roughness-induced rise in skin friction at low injection rates compared to the flat plate. The combination schemes demonstrated a potential for gain.

Schetz, J. A.↗
NASA NTRS1975

Study of a porous surface microphone sensor in an aerofoil

The porous microphone in an airfoil is described as a directional sensor which rejects flow noise. The airfoil allows the sensor to be rotated in the airflow over a wide range of yaw angles, 0 to 90 degrees, avoiding flow separation over the surface of the sensor and its associated additional flow noise. The microphone is discussed in terms of its acoustic properties, vibration sensitivity, effect of Mach number on the directivity function, and flow noise. Additional information on the acoustic calibration of the microphone, the acceleration sensitivity of the airfoil, stationary source and receiver in a moving gas, acoustic tests in airflow, and flow noise tests of the airfoil porous surface sensor is included.

Noiseux, D. U.↗
NASA NTRS1975

Development, fabrication and calibration of a porous surface microphone in an aerofoil

The development of a porous surface microphone in an airfoil intended to measure acoustic signals in a turbulent airflow and to minimize the flow noise is described. The sensor because of its airfoil operates over a wide range of yaw angles and flow velocities without excessive flow noise. The acoustic properties of the porous materials used in the airfoil sensor and their effects on the frequency response of the sensor were analyzed and tested. An accurate airfoil was selected, having a smaller thickness-to-chord ratio and an airfoil sensor was designed. The sensor was calibrated acoustically and its flow noise evaluated in the quiet BBN wind tunnel at flow velocities up to 70 m/sec. Results are presented.

Noiseux, D. U.↗
NASA NTRS1974

Heat transfer characteristics of porous media

An investigation was conducted regarding the relative effects of conduction and convection in a saturated porous medium. A method reported by Singh et al. (1973) is used to determine the effective thermal conductivity of the saturated porous material. Heat transfer measurements are conducted under conditions of forced convection of the saturated liquid parallel and countercurrent to the flow of heat. The results are compared with the data obtained with the aid of an analytical model.

Singh, B. S.↗
NASA NTRS1974

Properties of ribulose diphosphate carboxylase immobilized on porous glass

Ribulose-1,5-diphosphate carboxylase from spinach has been bound to arylamine porous glass with a diazo linkage and to alklamine porous glass with glutaraldehyde. Stability at elevated temperatures and responses to changes of pH and ribulose-1,5-diphosphate, Mg(2+), and dithiothreitol concentrations were not significantly different from the soluble enzyme, though stability at 4 C was somewhat improved.

Shapira, J.↗
NASA NTRS1976

Composite propellant combustion modeling with a porous plate burner

A burner is designed to model on a large scale (millimeters) the complex vapor phase processes that take place on awkwardly small scales (about a hundred microns) in the combustion of practical AP/ composite propellants at conventional pressures. Binder vapor evolution is modeled with gaseous fuel (ethane in the experiments reported) flow through a porous plate and oxidizer vapor with the flow of a gaseous oxidizer (air and enriched air in the experiments reported) through discrete holes in the porous plate. Measured flame standoff distance and surface temperature variations are consistent with theoretical predictions at atmospheric pressure. Data obtained at several atmospheres are discussed in the light of the current theories of propellant burning that place varying emphasis on the roles of chemical kinetics and fluid dynamic diffusion/mixing in the vapor phase of a burning composite propellant. The potential and proposed future applications of the burner are indicated.

Kumar, R. N.↗
NASA NTRS1976

Advanced porous transonic wind-tunnel nozzles

Advances in the design and control of the porous bleed flow distribution along the nozzle walls solves the problem of nonuniform flow at off-design conditions. This is accomplished in a two dimensional nozzle with porous parallel sidewalls backed with a single plenum chamber and employing a sliding compartment wall or backed with multiple plenum chambers within which the pressure can be controlled.

Sorensen, N. E.↗
NASA NTRS1977

Effects of grazing flow on the steady-state flow resistance and acoustic impedance of thin porous-faced liners

The results of an investigation of the effects of grazing flow on the steady-state flow resistance and acoustic impedance of seven Feltmetal and three Rigimesh thin porous-faced liners are presented. The acoustic impedance was measured using the two-microphone method. The principal findings of the study are (1) the effects of grazing flow were measured and found to be negligible, (2) negligible differences were measured between steady-state and acoustic resistance, (3) a semi-empirical model was derived that correlated both the steady-state resistance data and the acoustic impedance data of the seven Feltmetal liners. These findings suggest that nongrazing flow steady-state flow resistance tests could provide considerable insight into the acoustic behavior of porous liners in a grazing flow environment.

Hersh, A. D.↗
NASA NTRS1979

Flow friction of the turbulent coolant flow in cryogenic porous cables

Considered are cryogenic power transmission cables with porous cores. Calculations of the turbulent coolant flow with injection or suction through the porous wall are presented within the framework of a two-layer model. Universal velocity profiles were obtained for the viscous sublayer and flow core. Integrating the velocity profile, the law of flow friction in the pipe with injection has been derived for the case when there is a tangential injection velocity component. The effect of tangential velocity on the relative law of flow friction is analyzed. The applicability of the Prandtl model to the problem under study is discussed. It is shown that the error due to the acceptance of the model increases with the injection parameter and at lower Reynolds numbers; under these circumstances, the influence of convective terms in the turbulent energy equation on the mechanism of turbulent transport should be taken into account.

Hendricks, R. C.↗
NASA NTRS1979

An experimental study on porous plug jet noise suppressor

This paper contains a description of the configuration and operating characteristics of a porous center body plug nozzle jet noise suppressor that provides shock free flow over a wide range of nozzle pressure ratios. The elimination of the 'shock associated noise' and 'screeching' is accomplished by equalization of pressure along the jet axis. Because of the geometrical features of the porous plug nozzle, shear noise reductions are also observed at all subsonic and supersonic flow conditions tested. Additional benefits are the localization of the noise sources in the flow and the reduction of the spatial scale of the structure of the jet flow, which enhance the performance of an acoustic shield or baffle.

Maestrello, L.↗
NASA NTRS1979

Vapour phase details in the oscillatory combustion of propellants A porous plate analogue

A perforated porous plate burner is designed to scale up the vapor phase details in composite propellant combustion. A fuel vapor is passed through the pores and an oxidizer vapor is passed through the discrete perforations drilled in the plate. Discussion of the scale modeling of the vapor phase details in oscillatory combustion of composite propellants leads to the following conclusions: (1) the concept of a perforated porous plate analog for the composite propellant vapor phase combustion appears to be valid during oscillatory combustion as well; (2) the flame standoff distance can be conveniently determined with motion picture photography; (3) the flame standoff distance varies with the flow velocity during oscillatory combustion much the same way as during time-independent combustion; and (4) the overall structure of the combustion zone (flame) does not appear to vary too much from its time-independent structure during oscillatory combustion

Ramohalli, K.↗
NASA NTRS1979

Formation of porous surface layers in reaction bonded silicon nitride during processing

Microstructural examination of reaction bonded silicon nitride (RBSN) has shown that there is often a region adjacent to the as-nitrided surfaces that is even more porous than the interior of this already quite porous material. Because this layer of large porosity is considered detrimental to both the strength and oxidation resistance of RBSN, a study was undertaken to determine if its formation could be prevented during processing. All test bars studied were made from a single batch of Si powder which was milled for 4 hours in heptane in a vibratory mill using high density alumina cylinders as the grinding media. After air drying the powder, bars were compacted in a single acting die and hydropressed.

Shaw, N. J.↗
NASA NTRS1981

Porous tooling process for manufacture of graphite/polyimide composites

A porous tooling system was selected for the processing of Graphite/PMR-15 Polyimide laminates in thickness up to 3.2 mm. (0.125 inch). This tool system must have a reasonable strength, permeability dimensional stability, and thermal conductivity to accomplish curing at 600 F and 200 psi and 200 psi autoclave temperature and pressure. A permeability measuring apparatus was constructed and permeability vs. casting water level determined to produce tools at three different permeability levels. On these tools, laminates of 5, 11, and 22 plies (.027, .060, and 0.121 inch) were produced and evaluated by ultrasonic, mechanical, and thermal tests to determine the effect of the tool permeability on the cured laminates. All tools produced acceptable laminates at 5 and 11 plies but only the highest permeability produced acceptable clear ultrasonic C-Scans. Recommendations are made for future investigations of design geometry, and strengthening techniques for porous ceramic tooling.

Smiser, L. W.↗
NASA NTRS1981

Thermal and flow analysis of a convection air-cooled ceramic coated porous metal concept for turbine vanes

The heat transfer and pressure drop through turbine vanes made of a sintered, porous metal coated with a thin layer of ceramic and convection cooled by spanwise flow of cooling air were analyzed. The analysis was made to determine the feasibility of using this concept for cooling very small turbines, primarily for short duration applications such as in missile engines. The analysis was made for gas conditions of approximately 10 and 40 atm and 1644 K and with turbine vanes made of felt type porous metals with relative densities from 0.2 to 0.6 and ceramic coating thicknesses of 0.076 to 0.254 mm.

Stepka, F. S.↗