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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Supersonic flow of chemically reacting gas-particle mixtures. Volume 1: A theoretical analysis and development of the numerical solution

A numerical solution for chemically reacting supersonic gas-particle flows in rocket nozzles and exhaust plumes was described. The gas-particle flow solution is fully coupled in that the effects of particle drag and heat transfer between the gas and particle phases are treated. Gas and particles exchange momentum via the drag exerted on the gas by the particles. Energy is exchanged between the phases via heat transfer (convection and/or radiation). Thermochemistry calculations (chemical equilibrium, frozen or chemical kinetics) were shown to be uncoupled from the flow solution and, as such, can be solved separately. The solution to the set of governing equations is obtained by utilizing the method of characteristics. The equations cast in characteristic form are shown to be formally the same for ideal, frozen, chemical equilibrium and chemical non-equilibrium reacting gas mixtures. The particle distribution is represented in the numerical solution by a finite distribution of particle sizes.

Penny, M. M.↗
NASA NTRS1976

The development of an electrochemical technique for in situ calibrating of combustible gas detectors

A program to determine the feasibility of performing in situ calibration of combustible gas detectors was successfully completed. Several possible techniques for performing the in situ calibration were proposed. The approach that showed the most promise involved the use of a miniature water vapor electrolysis cell for the generation of hydrogen within the flame arrestor of a combustible gas detector to be used for the purpose of calibrating the combustible gas detectors. A preliminary breadboard of the in situ calibration hardware was designed, fabricated and assembled. The breadboard equipment consisted of a commercially available combustible gas detector, modified to incorporate a water vapor electrolysis cell, and the instrumentation required for controlling the water vapor electrolysis and controlling and calibrating the combustible gas detector. The results showed that operation of the water vapor electrolysis at a given current density for a specific time period resulted in the attainment of a hydrogen concentration plateau within the flame arrestor of the combustible gas detector.

Shumar, J. W.↗
NASA NTRS1976

Waveguide CO2 laser gain - Dependence on gas kinetic and discharge properties

A simple rate-equation approach is used to examine the gas-kinetic and discharge properties of waveguide CO2 lasers. The dependence of the population inversion and laser small-signal gain on gas pressure, gas mixture, pumping rate (discharge current), tube bore diameter, and wall temperature is calculated along with the dependence of laser tunability on the gas-kinetic properties and cavity losses. It is found that for low-loss cavities, the laser tunability may substantially exceed the molecular full width at half-maximum. Furthermore, the more helium-rich gas mixtures give greater tunability when cavity losses are small, and less tunability when cavity losses are large. By contrast with conventional lasers, the waveguide-laser transition is homogeneously broadened. Thus, the dependence of gain on gas pressure and other kinetic properties differs substantially from that predicted by scaling results from conventional low-pressure lasers.

Cohen, S. C.↗
NASA NTRS1976

Thermal effects during loading of vehicle-borne pressurizing gas tanks from reservoir tanks

Two theoretical methods of analyzing the process of filling vehicle-borne, high pressure gas tanks from gas reservoirs are presented. The first method assumes that a given weight of gas at ambient temperature and a specified pressure is required in the vehicle tank and selects a tank volume to exactly accommodate these conditions. The second method assumes the vehicle tank has a given volume and then predicts the temperature overshoot that results from loading a fixed weight of gas to a predetermined pressure and, thereafter, the final gas pressure after the vehicle tank and its contents have returned to ambient temperature. In addition, a means is presented for predicting to what pressure the vehicle tank must be loaded such that, after returning to ambient temperature, it will contain at least the desired weight of gas at the desired pressure.

Wing, L. D.↗
NASA NTRS1977

Trace Gas Analyzer (TGA) program

The design, fabrication, and test of a breadboard trace gas analyzer (TGA) is documented. The TGA is a gas chromatograph/mass spectrometer system. The gas chromatograph subsystem employs a recirculating hydrogen carrier gas. The recirculation feature minimizes the requirement for transport and storage of large volumes of carrier gas during a mission. The silver-palladium hydrogen separator which permits the removal of the carrier gas and its reuse also decreases vacuum requirements for the mass spectrometer since the mass spectrometer vacuum system need handle only the very low sample pressure, not sample plus carrier. System performance was evaluated with a representative group of compounds.

Source record↗
NASA NTRS1978

Coronal gas in the Galaxy. II - A statistical analysis of O VI absorptions

This paper deals with general inferences about the low-density phase of interstellar gas having temperatures well above 200,000 K (the 'coronal gas') which can be drawn from O VI absorption data for 72 stars. Attention is given to the behavior of radial velocities, possible evidence for circumstellar O VI, the space distribution of the O VI gas, crowding of normal interstellar gas, and temperature distributions for the coronal gas. A model is adopted in which the coronal gas is contained within randomly distributed and nonoverlapping parcels, each with a size, pressure, and internal temperature distribution that do not vary markedly from one unit to the next. It is shown that the one-dimensional velocity dispersion for O VI regions (26 km/s) is substantially higher than the value for ordinary interstellar clouds (6.4 km/s).

Jenkins, E. B.↗
NASA NTRS1980

Self-gravitating gas flow in barred spiral galaxies

A series of two-dimensional numerical experiments is performed in order to test the response of an isothermal, self-gravitating gas disk to a uniformly rotating, barlike gravitational potential. The barlike potential is an equilibrium stellar model from the n-body calculations of Miller and Smith (1979). In the bar-dominated, central regions of the disk, a gas bar whose phase depends primarily on the location of principal resonances in the disk is formed. This response can be understood in terms of orbit-crowding effects. In the gas-dominated outer regions of the disk, two-armed trailing spiral waves are formed. The local pitch angle of these waves increases with increasing fractional gas mass. These self-gravitating gas waves are not self-sustaining. They are driven from the ends of equilibrium stellar bars, and their phase does not depend on the location of resonances in the disk. The relevance of these self-gravitating waves to observations and models of barred spiral galaxies is discussed. It is concluded that these waves and their associated ringlike structures may be consistent with the morphological distribution of gas features in barred spiral galaxies.

Huntley, J. M.↗
NASA NTRS1982

Gas in the galactic halo

The evidence that gas exists in the halo of the Galaxy is examined. The likely properties of halo gas intervening between QSOs and the Galaxy are extracted from observations of the galactic halo. The available data discussed include 21-cm observations, optical absorption lines, ultraviolet lines, and X-ray observations. The possible existence of a cosmic ray halo is assessed, and the relationship of galactic size to the extent of the halo is examined. The main physical constraints on the gas in the halo are detailed, including the radiation field, particle density, temperature, mass in the halo gas, and abundances. Models for the gas in the halo are summarized. It appears that the distribution of gas in the galactic halo is an expanded disk not more than 10 kpc thick. At low column densities, the Galaxy could extend out to several times the Holmberg radius. The disk may be photoionized on the outside by the QSO background radiation.

York, D. G.↗
NASA NTRS1983

Absorption by halo gas in the direction of M13

A high velocity cloud in the direction 1 = 59 degrees, b = 41 degrees is detected in absorption at approximately -80 km/s in high dispersion IUE spectra of the blue star Barnard 29 in the globular cluster M13. The cloud is also seen in the H I 21 cm emission data of Kerr and Knapp (1972). Its radial velocity agrees with Giovanelli's data (1980, 1981) for high velocity clouds seen in this general direction of the sky. The cloud's motion is incompatible with the suggestions that neutral halo gas corotates with disk gas. The motion could be explained if neutral halo gas rotates more slowly than disk gas with increasing distance from the galactic plane. Because of our very limited understanding of the actual motions of halo gas, the scale height of this gas is best derived from plots of N sin b versus z for galactic and extragalactic stars.

De Boer, K. S.↗
NASA NTRS1983

Assessment of institutional barriers to the use of natural gas fuel in automotive vehicle fleets

Institutional barriers to the use of natural gas as a fuel for motor vehicle fleets were identified. Recommendations for barrier removal were developed. Eight types of institutional barriers were assessed: (1) lack of a national standard for the safe design and certification of natural gas vehicles and refueling stations; (2) excessively conservative or misapplied state and local regulations, including bridge and tunnel restrictions, restrictions on types of vehicles that may be fueled by natural gas, zoning regulations that prohibit operation of refueling stations, parking restrictions, application of LPG standards to LNG vehicles, and unintentionally unsafe vehicle or refueling station requirements; (3) need for clarification of EPA's tampering enforcement policy; (4) the U.S. hydrocarbon standard; (5) uncertainty concerning state utility commission jurisdiction; (6) sale for resale prohibitions imposed by natural gas utility companies or state utility commissions; (7) uncertainty of the effects of conversions to natural gas on vehicle manufactures warranties; and (8) need for a natural gas to gasoline equivalent units conversion factor for use in calculation of state road use taxes.

Jablonski, J.↗
NASA NTRS1983

Far-IR spectroscopy of the galactic center: Neutral and ionized gas in the central 10 pc of the galaxy

The 3P1 - 3P2 fine structure line emission from neutral atomic oxygen at 63 microns in the vicinity of the galactic center was mapped. The emission is extended over more than 4' (12 pc) along the galactic plane, centered on the position of Sgr A West. The line center velocities show that the O I gas is rotating around the galactic center with an axis close to that of the general galactic rotation, but there appear also to be noncircular motions. The rotational velocity at R is approximately 1 pc corresponds to a mass within the central pc of about 3 x 10(6) solar mass. Between 1 and 6 pc from the center the mass is approximately proportional to radius. The (O I) line probability arises in a predominantly neutral, atomic region immediately outside of the ionized central parsec of out galaxy. Hydrogen densities in the (O I) emitting region are 10(3) to 10(6) cm(-3) and gas temperatures are or = 100 K. The total integrated luminosity radiated in the line is about 10(5) solar luminosity, and is a substantial contribution to the cooling of the gas. Photoelectric heating or heating by ultraviolet excitation of H2 at high densities (10(5) cm(-3)) are promising mechanisms for heating of the gas, but heating due to dissipation of noncircular motions of the gas may be an alternative possibility. The 3P1 - 3P0 fine structure line of (O III) at 88 microns toward Sgr A West was also detected. The (O III) emission comes from high density ionized gas (n 10(4) cm(-3)), and there is no evidence for a medium density region (n 10(3) cm(-3)), such as the ionized halo in Sgr A West deduced from radio observations. This radio halo may be nonthermal, or may consist of many compact, dense clumps of filaments on the inner edges of neutral condensations at R or = 2 pc.

Hollenbach, D. J.↗
NASA NTRS1983

Evaluation of Gas-Cooled Pressurized Phosphoric Acid Fuel Cells for Electric Utility Power Generation

Gas cooling is a more reliable, less expensive and a more simple alternative to conventional liquid cooling for heat removal from the phosphoric acid fuel cell (PAFC). The feasibility of gas-cooling was already demonstrated in atmospheric pressure stacks. Theoretical and experimental investigations of gas-cooling for pressurized PAFC are presented. Two approaches to gas cooling, Distributed Gas-Cooling (DIGAS) and Separated Gas-Cooling (SGC) were considered, and a theoretical comparison on the basis of cell performance indicated SGC to be superior to DIGAS. The feasibility of SGC was experimentally demonstrated by operating a 45-cell stack for 700 hours at pressure, and determining thermal response and the effect of other related parameters.

Faroque, M.↗
NASA NTRS1983

Evaluation of gas cooling for pressurized phosphoric acid fuel cell stacks

Gas cooling is a more reliable, less expensive and a more simple alternative to conventional liquid cooling for heat removal from the phosphoric acid fuel cell (PAFC). The feasibility of gas cooling has already been demonstrated in atmospheric pressure stacks. This paper presents theoretical and experimental investigation of gas cooling for pressurized PAFC. Two approaches to gas cooling, Distributed Gas Cooling (DIGAS) and Separated Gas Cooling (SGC) were considered, and a theoretical comparison on the basis of cell performance indicated SGC to be superior to DIGAS. The feasibility of SGC was experimentally demonstrated by operating a 45-cell stack for 700 hours at pressure, and determining thermal response and the effect of other related parameters.

Farooque, M.↗
NASA NTRS1985

Thermal phases of interstellar and quasar gas

Interstellar gas may be in a variety of thermal phases, depending on how it is heated and ionized; here a unified picture of the equation of state of interstellar and quasar gas is presented for a variety of such mechanisms over a broad range of temperatures, densities, and column densities of absorbing matter. It is found that for select ranges of gas pressure, photoionizing flux, and heating, three thermally stable phases are allowed: coronal gas (T above 100,000 K); warm gas (T about 10,000 K); and cold gas (T less than 100 K). With attenuation of ultraviolet and X-ray radiation, the cold phase may undergo a transition to molecules. In quasar broad-line clouds, this transition occurs at column density N(H) = about 10 to the 23rd/sq cm and could result in warm molecular cores and observable emission from H2 and OH. The underlying atomic physics behind each of these phase transitions and their relevance to interstellar matter and quasars are discussed.

Lepp, S.↗
NASA NTRS1987

Gas filter correlation radiometry: Report of panel

To measure the concentration of a gas in the troposphere, the gas filter radiometer correlates the pattern of the spectral lines of a sample of gas contained within the instrument with the pattern of the spectral lines in the upwelling radiation. A schematic diagram of a generalized gas filter radiometer is shown. Three instruments (the Gas Filter Radiometer, GFR; the Halogen Occultation Experiment, HALOE; and the Gas Filter Correlation Spectrometer, GASCOFIL) that have application to remotely measuring tropospheric constituents are described. A set of preliminary calculations to determine the feasibility of performing a multiple-layer, tropospheric carbon monoxide measurement experiment was performed. It can be seen that a three-layer measurement in the troposphere is possible.

Reichle, Henry G., Jr.↗
NASA NTRS1987

Molecular gas in the starburt nucleus of M82

The 7" resolution CO observations of the central 1 kpc of M82 have resolved 2 components of molecular gas: (1) a high concentration in the central 700 pc x 200 pc, and (2) extended features that may be gas expelled from the central concentration. The central concentration of molecular gas falls in the same confines as the other tracers of recent star formation, and may be identified directly with the star burst region. The molecular gas in the star burst nucleus of M82 appears to be highly disturbed and has high kinetic temperature, likely consequences of the high density of young star clusters. Stellar winds and subsequent supernovae from the star clusters can effectively sweep up the interstellar medium. The spatial distribution and kinematics of the nuclear concentration of the molecular gas, as well as the 2 micron light distribution, suggest the presence of a stellar bar in M82. Comparisons of the M82 star burst nucleus to a sample of IR luminous galaxies suggest that star burst regions in general may have a higher gas temperature and much higher L sub IR/M sub H2 that the galactic disk, and that the L sub IR of the star burst regions may be essentially proportional to their area.

Lo, K. Y.↗
NASA NTRS1987

Gas chromatographic instrumentation for the analysis of aerosols and gases in Titan's atmosphere

Instrumentation presently being developed by NASA for the collection and analysis of organic gases and aerosols in Titan's atmosphere is described together with the results of the preliminary experiments. For the aerosols, stepwise pyrolysis was shown to be a suitable method for preparing complex organic material for gas chromatography (GC), and a pyrolysis-gas chromatograph was developed and successfully used to analyze a simulated Titan aerosol. Atmospheric gases will be collected by a low-pressure gas sampling system using large-volume sample loops and analyzed by GC. The results of preliminary studies using a 20 cu cm sampling system and a very sensitive metastable ionization detector showed that hydrocarbon components at the 10 ppb level can be detected. Studies are in progress on shortening the overall analysis time by improving the pyrolysis system, the gas sampling system, and the associated gas chromatograph. Further development of the gas sampling system is planned to ensure rapid collection of samples adequate for analysis by GC over the entire range of pressures to be encountered during the probe's descent.

Scattergood, T. W.↗
NASA NTRS1988

Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions

The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

Wilson, J. W.↗