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At least 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Pressure and velocity in a developing coaxial jet

Determinations of static pressure, mean velocity and turbulence intensity in the developing region of coaxial jets are presented. Detailed profiles were obtained at twelve axial locations (extending from the nozzle exit for a distance of 5 diameters) downstream from a single element of the Bell Aerospace H2/O2 19-element coaxial injector. Measurements of mass-flux per unit area (using a constant temperature anemometer), total pressure and local temperature were used in the determination of local static pressure and velocity. These data show a low pressure region exists near the nozzle exit. Although this pressure reduction is small (0.34 psi), it substantially altered the flow development. Comparison of results shows that velocity near the nozzle exit decreases initially (no central velocity core) as a result of both pressure gradients and viscous mixing. These data are compared with analytical predictions made using available computer codes. Results show the need to consider pressure effects in any proposed mathematical model.

Moon, L. F.↗
NASA NTRS1976

An approach to the prediction of airplane interior noise

At present there is no well-proven method of calculating airplane interior noise associated with jet and boundary layer sources. In this presentation, statistical energy analysis is used to calculate fuselage skin vibration and interior noise levels, with the sidewall represented as a double-wall system. The results show that, in the case of an unpressurized fuselage, the acoustic transmission is dominated by the non-resonant response of the structure. Extension of the results to include pressurization effects and turbulent boundary layer excitation is discussed, particular emphasis being placed on aerodynamic coincidence.

Wilby, J. F.↗
NASA NTRS1977

Instrument to average 100 data sets

An instrumentation system is currently under development which will measure many of the important parameters associated with the operation of an internal combustion engine. Some of these parameters include mass-fraction burn rate, ignition energy, and the indicated mean effective pressure. One of the characteristics of an internal combustion engine is the cycle-to-cycle variation of these parameters. A curve-averaging instrument has been produced which will generate the average curve, over 100 cycles, of any engine parameter. the average curve is described by 2048 discrete points which are displayed on an oscilloscope screen to facilitate recording and is available in real time. Input can be any parameter which is expressed as a + or - 10-volt signal. Operation of the curve-averaging instrument is defined between 100 and 6000 rpm. Provisions have also been made for averaging as many as four parameters simultaneously, with a subsequent decrease in resolution. This provides the means to correlate and perhaps interrelate the phenomena occurring in an internal combustion engine. This instrument has been used successfully on a 1975 Chevrolet V8 engine, and on a Continental 6-cylinder aircraft engine. While this instrument was designed for use on an internal combustion engine, with some modification it can be used to average any cyclically varying waveform.

Tuma, G. B.↗
NASA NTRS1977

Infrared laboratory studies of synthetic planetary atmospheres

Topics covered include: the broadening of individual lines in the CO fundamental by various gases; total band absorptance as a function of absorber thickness and total effect pressure at various temperatures for bands of CO and N2O; nitric acid vapor content in the region of the ozone layer; optical properties of solid NH3; HSO4 concentration in Venus clouds; Burch's law of multiplicative transmittance for mixing absorbing gases when their lines are broadened by helium and hydrogen; ling strength and self-broadening parameters in the v3 fundamental of CO2 and N2O; optical constants of liquid ammonia, liquid methane, saturated hydrocarbons, ammonium hydride and ammonium salts.

Williams, D.↗
NASA NTRS1978

One-dimensional outgassing problem

A predominantly numerical study, using the direct-simulation Monte Carlo method, of the flow from outgassing surfaces with plane, cylindrical, or spherical geometry is presented. The numerical results for the plane flow case are compared with existing theoretical and experimental results and also with a new formulation of the jump conditions across the Knudsen layer between the surface and the continuum outflow. This outflow is sonic for the free expansion case but subsonic in the presence of back-pressure effects. The self-scattered return flux is 19% of the outgassed flux in the sonic outflow case and increases at lower Mach numbers. Thermal accomodation and reflection of this return flux produces an outgassing cooling effect. The cylindrical and spherical geometries introduce an additional Knudsen number defined by the ratio of the mean free path in the effusing gas to the radius. The plane flow results apply when this Knudsen number is less than 0.001 and, when it is of order unity or above, the return flux is inversely proportional to it.

Tran Cong, T.↗
NASA NTRS1979

Hydrogen-fueled diesel engine without timed ignition

Experiments were carried out to investigate the feasibility of converting a diesel engine to hydrogen-fueled operation without providing a timed ignition system. Use was made of a glow plug and a multiple-strike spark plug. The glow plug was found to provide reliable ignition and smooth engine operation. It caused the hydrogen to ignite almost immediately upon the start of injection. Indicated mean effective pressures were on the order of 1.3 MPa for equivalence ratios between 0.1 and 0.4 at a compression ratio of 18. This is significantly higher than the corresponding result obtained with diesel oil (about 0.6 MPa for equivalence ratios between 0.3 and 0.9). Indicated thermal efficiencies were on the order of 0.4 for hydrogen and 0.20-0.25 for diesel oil. Operation with the multiple-strike spark system yielded similar values for IMEP and efficiency, but gave rise to large cycle-to-cycle variations in the delay between the beginning of injection and ignition. Large ignition delays were associated with large amplitude pressure waves in the combustion chamber. The measured NO(x) concentrations in the exhaust gas were of the order of 50-100 ppm. This is significantly higher than the corresponding results obtained with premixed hydrogen and air at low equivalence ratios. Compression ignition could not be achieved even at a compression ratio of 29.

Homan, H. S.↗
NASA NTRS1980

A test program for solar collectors

Rigorous environmental and performance tests qualify solar collector for use in residential solar-energy systems. Testing over 7 month period examined pressurized effects, wind and snow loading, hail damage, solar and thermal degradation, effects of pollutants, efficiency, and outgassing. Test procedures and results are summarized in tables, graphs, and text.

Source record↗
NASA NTRS1980

Advanced rotary engine studies

A review of rotary engine developments relevant to a stratified charge rotary aircraft engine is presented. Advantages in module size and weight, fuel efficiency, reliability, and multi-fuel capability are discussed along with developments in turbocharging, increased mean effective pressure, improved apex seal/trochoid wear surfacing materials, and high strength and temperature aluminum casting alloys. A carbureted prototype aircraft engine is also described.

Jones, C.↗
NASA NTRS1980

Performance, emissions, and physical characteristics of a rotating combustion aircraft engine, supplement A

Testing was conducted using the basic RC2-75 engine, to which several modifications were incorporated which were designed to reduce the hydrocarbon emissions and reduce the specific fuel consumption. The modifications included close-in surface gap spark plugs, increased compression ratio rotors, and provisions for utilizing either side or peripheral intake ports, or a combination of the two if required. The proposed EPA emissions requirements were met using the normal peripheral porting. The specific fuel economy demonstrated for the modified RC2-75 was 283 g/kW-hr at 75% power and 101 brake mean effective pressure (BMEP) and 272.5 g/kW-hr at 75% power and 111 BMEP. The latter would result from rating the engine for takeoff at 285 hp and 5500 rpm, instead of 6000 rpm.

Lamping, R. K.↗
NASA NTRS1979

On seasonal phenomena in Saturn's atmosphere - New observations of Saturn's 3nu3 methane band

Saturn's 3nu3 CH4 band has been reobserved during April-June 1976, using the same telescope and spectrographic set-up used to study this band during the 1970 apparition. Direct comparison of the ratio spectra Saturn/moon reveals greater absorption in the manifold cores during 1976, but the increase is not as pronounced as that for the stronger CH4 bands. The rotational temperature and effective pressure of this band did not change significantly. These results are interpreted in terms of a possibly seasonal settling of the upper boundary of Saturn's atmospheric haze layer.

Trafton, L.↗
NASA NTRS1980

Future prospects for gamma-ray

Astrophysical phenomena discussed are: the very energetic and nuclear processes associated with compact objects; astrophysical nucleo-synthesis; solar particle acceleration; the chemical composition of the planets and other bodies of the solar system; the structure of our galaxy; the origin and dynamic pressure effects of the cosmic rays; the high energy particles and energetic processes in other galaxies, especially active ones; and the degree of matter antimater symmetry of the universe. The gamma ray results of GAMMA-I, the gamma ray observatory, the gamma ray burst network, solar polar, and very high energy gamma ray telescopes on the ground provide justification for more sophisticated telescopes.

Fichtel, C.↗
NASA NTRS1981

Experimental analysis of IMEP in a rotary combustion engine

A real time indicated mean effective pressure measurement system is described which is used to judge proposed improvements in cycle efficiency of a rotary combustion engine. This is the first self-contained instrument that is capable of making real time measurements of IMEP in a rotary engine. Previous methods used require data recording and later processing using a digital computer. The unique features of this instrumentation include its ability to measure IMEP on a cycle by cycle, real time basis and the elimination of the need to differentiate volume function in real time. Measurements at two engine speeds (2000 and 3000 rpm) and a full range of loads are presented, although the instrument was designed to operate to speeds of 9000 rpm.

Schock, H. J.↗
NASA NTRS1981

Investigations of coherent anti-Stokes Raman spectroscopy /CARS/ for practical combustion diagnostics

Coherent anti-Stokes Raman spectroscopy (CARS) is a coherent wave-mixing process in which the signal emerges as a laser-like beam in a precise direction. The spectroscopic technique is appropriate to spatially and temporally resolved measurements of temperature and major species concentrations in combustion. It has been generated from all of the dominant constituents in air-fed, hydrogen, and hydrocarbon fueled combustion, and found applicable to practical combustion systems. High pressure effects on CARS spectra have also been examined.

Eckbreth, A. C.↗
NASA NTRS1981

Future prospects for gamma-ray astronomy

As gamma-ray astronomy moves from the discovery to the exploratory phase, the promise of gamma-ray astrophysics noted by theorists in the late 1940s and 1950s is beginning to be realized. In the future, satellites should carry instruments that will have over an order of magnitude greater sensitivity than those flown thus far, and, for at least some portions of the gamma-ray energy range, these detectors will also have substantially improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance our knowledge of several astrophysical phenomena including the very energetic and nuclear processes associated with compact objects, astrophysical nucleosynthesis, solar particle acceleration, the chemical composition of the planets and other bodies of the solar system, the structure of our galaxy, the origin and dynamic pressure effects of the cosmic rays, high energy particles and energetic processes in other galaxies especially active ones, and the degree of matter-antimatter symmetry of the universe. The gamma-ray results of the forthcoming programs such as Gamma-I, the Gamma Ray Observatory, the gamma-ray burst network, Solar Polar, and very high energy gamma-ray telescopes on the ground will almost certainly provide justification for more sophisticated telescopes. These advanced instruments might be placed on the Space Platform currently under study by N.A.S.A.

Fichtel, C.↗
NASA NTRS1981

Experimental analysis of IMEP in a rotary combustion engine

This experimental work demonstrates the use of a NASA designed, real time Indicated Mean Effective Pressure (IMEP) measurement system which will be used to judge proposed improvements in cycle efficiency of a rotary combustion engine. This is the first self-contained instrument that is capable of making real time measurements of IMEP in a rotary engine. Previous methods used require data recording and later processing using a digital computer. The unique features of this instrumentation include its ability to measure IMEP on a cycle by cycle, real time basis and the elimination of the need to differentiate the volume function in real time. Measurements at two engine speeds (2000 and 3000 RPM) and a full range of loads are presented, although the instrument was designed to operate to speeds of 9000 RPM.

Schock, H. J.↗
NASA NTRS1982

Discharge of 1400 AH lithium thionyl chloride cells into voltage reversal

The development of a high energy density battery is discussed. Tests were conducted on a 1400 AH cell and they include: drop tests, crush tests, vibration and shock tests, hydrostatic pressure effects, charge current tests, and discharge tests. None of these tests led to a venting or explosion of the cell. Criteria are presented for extending RV safety of a 1400 AH cell.

Zolla, A. E.↗
NASA NTRS1984

Stabilizing Fiber-Optic Transmission Lines

Voltage-controlled optical phase shifter is key. Optical phase shifter stabilizes propagation delay of fiber-optic transmission line by compensating for temperature and pressure effects. Applicable to phased array antenna systems and very-long-baseline interferometer distribution systems.

Lutes, G. F.↗
NASA NTRS1982

The future of high energy gamma ray astronomy and its potential astrophysical implications

Future satellites should carry instruments having over an order of magnitude greater sensitivity than those flown thus far as well as improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance knowledge of: the very energetic and nuclear processes associated with compact objects; the structure of our galaxy; the origin and dynamic pressure effects of the cosmic rays; the high energy particles and energetic processes in other galaxies; and the degree of matter-antimatter symmetry of the universe. The relevant aspects of extragalactic gamma ray phenomena are emphasized along with the instruments planned. The high energy gamma ray results of forthcoming programs such as GAMMA-1 and the Gamma Ray Observatory should justify even more sophisticated telescopes. These advanced instruments might be placed on the space station currently being considered by NASA.

Fichtel, C. E.↗