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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Remote detection of geobotanical anomalies associated with hydrocarbon microseepage

As part of the continuing study of the Lost River, West Virginia NASA/Geosat Test Case Site, an extensive soil gas survey of the site was conducted during the summer of 1983. This soil gas survey has identified an order of magnitude methane, ethane, propane, and butane anomaly that is precisely coincident with the linear maple anomaly reported previously. This and other maple anomalies were previously suggested to be indicative of anaerobic soil conditions associated with hydrocarbon microseepage. In vitro studies support the view that anomalous distributions of native tree species tolerant of anaerobic soil conditions may be useful indicators of methane microseepage in heavily vegetated areas of the United States characterized by deciduous forest cover. Remote sensing systems which allow discrimination and mapping of native tree species and/or species associations will provide the exploration community with a means of identifying vegetation distributional anomalies indicative of microseepage.

Rock, B. N.↗
NASA NTRS1984

Radical molecule and ion-molecule mechanisms in the polymerization of hydrocarbons and chlorosilanes in R.F. plasmas at low pressures (below 1.0 Torr)

The ion-molecule and the radical-molecule mechanisms are responsible for the dissociation of hydrocarbons, and chlorosilane monomers and the formation of polymerized species, respectively, in the plasma state of a RF discharge. In the plasma, of a mixture of monomer with Ar, the rate determining step for both dissociation and polymerization is governed by an ion-molecular type interaction. Additions of H2 or NH3 to the monomer Ar(+) mixture transforms the rate determining step from an ion-molecular interaction to a radical-molecule type interaction for both monomer dissociation and polymerization processes.

Avni, R.↗
NASA NTRS1985

The hydrocarbon ring C3H2 is ubiquitous in the Galaxy

The discovery of a strong microwave (1.6 cm-wavelength) spectral line, the carrier of which is common and widespread throughout the Galaxy is reported. A survey of a large number of sources shows that the line appears in emission in cold dust clouds, in absorption in the direction of the Galactic center, and exhibits complex profiles toward H II regions. Toward Cas A and distant H II regions, intervening 'spiral arm' clouds produce absorption. For almost all cases, the absorption features show a striking 1:1 radial velocity correspondence with those seen, e.g., in H2CO spectra of the same objects. The data indicate that the line arises between low-lying energy states of a rather polar molecule. Recent work by Thaddeus, Vrtilek, and Gottlieb (1985) incorporating the present data, shows that the line in question is the 1(10)-1(01) transition of the small hydrocarbon ring C3H2.

Matthews, H. E.↗
NASA NTRS1985

A new emission feature in IRAS spectra and the polycyclic aromatic hydrocarbon spectrum

IRAS spectra of those sources which show strong 7.7 and 11.3 micron emission features also show a plateau of emission extending from 11.3 to about 13.0 microns. Like the 11.3 micron feature, this new feature is attributed to the CH out-of-plane bending mode in polycyclic aromatic hydrocarbons (PAHs). Its discovery reinforces the identification of the 'unidentified infrared emission features' as emission from PAHs. The wavelength of this new feature suggests that interstellar PAHs are not as partially hydrogenated as hitherto thought. It also constrains their molecular structure.

Cohen, M.↗
NASA NTRS1986

The high-temperature oxidation of aromatic hydrocarbons

Chemical mechanisms of the atmospheric pressure, high-temperature (875-1500 K) gas-phase oxidation of benzene, toluene, ethylbenzene, and propylbenzene are described and discussed. Oxidation trends evident from turbulent flow reactor experiments serve as the basis for the mechanisms of the oxidation of benzene and alkylated aromatics. The potential effects of very high temperatures and pressures on the chemistry of oxidation of aromatics are described. The oxidation of benzene and phenyl radical has been found to proceed in a stepwise C6-C5-C4 sequence. Species profiles obtained from flow-reactor experiments suggest that the oxidation of benzene and phenyl radical follows the generalized route via phenoxy, cyclopentadienyl and butadienyl radical. The oxidation of the C4 species branches into multiple pathways that yield copious amounts of ethylene and acetylene. Certain major trends are evident: the alkylated aromatics on initial attack either form styrene, benzyl radical or benzene. The styrene reacts further to produce a benzyl radical or benzene. The oxidation of an alkylated aromatic hydrocarbon appears eventually to reduce to the oxidation of either phenyl radical or benzene.

Brezinsky, K.↗
NASA NTRS1987

Determining Heats of Combustion of Gaseous Hydrocarbons

Enrichment-oxygen flow rate-ratio related to heat of combustion. Technique developed for determining heats of combustion of natural-gas samples. Based on measuring ratio m/n, where m is (volmetric) flow rate of oxygen required to enrich carrier air in which test gas flowing at rate n is burned, such that mole fraction of oxygen in combustion-product gases equals that in carrier air. The m/n ratio directly related to heats of combustion of saturated hydrocarbons present in natural gas.

Singh, Jag J.↗
NASA NTRS1986

Identification of polycyclic aromatic hydrocarbons

The nature of the Very Small Grains evidenced by K. Sellgren (1985) is discussed. Thsir stability suggests that they are graphitic material and specifically Polycyclic Aromatic Hydrocarbons (PAHs). The expected infrared emission of a typical PAH, coronene, gives an impressive spectroscopic agreement with the five observed Unidentified IR Emission Features, leading to an unambiguous identification. Those PAHs are the most abundant organic molecules detected to date (f is approximately .00001).

Leger, A.↗
NASA NTRS1986

An updated hydrocarbon photochemical model for the Jovian atmosphere from the troposphere through the homopause: A prelude to Galileo

A photochemical model for the atmosphere of Jupiter, including 1-D vertical eddy diffusive transport, was developed. It extends from the upper troposphere through the homopause. The hydrocarbon chemistry involves species containing up to four carbon atoms (and polyynes through C8H2). The calculations show that a large fraction of photochemical carbon may be contained in molecules with more than two carbon atoms. At the tropopause, C2H6 is the major photochemical species and C2H2, C3H8, and C4H10 are of comparable abundance and down from C2H6 by a factor of ten. These species may be detectable with the mass spectrometer of the Galileo Probe. The vertical distributions of the photochemical species are sensitive to the magnitude of eddy diffusive mixing in the troposphere and stratosphere and the details of the interface region.

Allen, M.↗
NASA NTRS1986

Test program to provide confidence in liquid oxygen cooling of hydrocarbon fueled rocket thrust chambers

In previous tests of liquid oxygen cooling of hydrocarbon fueled rocket engines, small oxygen leaks developed at the throat of the thrust chamber and film cooled the hot gas side of the chamber wall without resulting in catastrophic failure. However, more testing is necessary to demonstrate that a catastropic failure would not occur if cracks developed further upstream between the injector and the throat, where the boundary layer has not been established. Since under normal conditions cracks are expected to form in the throat region of the thrust chamber, cracks must be initiated artificially in order to control their location. Several methods of crack initiation are discussed here.

Armstrong, Elizabeth S.↗
NASA NTRS1986

Polycyclic aromatic hydrocarbons and the diffuse interstellar bands

The profiles, widths and positions of the Diffuse Interstellar Bands (DIB's) are discussed. It is shown that the carriers of the DIB's are molecular rather than impurities in grains. Polycyclic Aromatic Hydrocarbons (PAH's) are attractive candidates for the DIB's, in view of their likely abundance, their extreme stability, and the fact that these molecules, and their corresponding radicals, show visible transitions.

Van Der Zwet, G. P.↗
NASA NTRS1986

Rapid computation of chemical equilibrium composition - An application to hydrocarbon combustion

A scheme for rapidly computing the chemical equilibrium composition of hydrocarbon combustion products is derived. A set of ten governing equations is reduced to a single equation that is solved by the Newton iteration method. Computation speeds are approximately 80 times faster than the often used free-energy minimization method. The general approach also has application to many other chemical systems.

Erickson, W. D.↗
NASA NTRS1986

Ion-molecule reactions of hydrocarbon ions in C2H2 and HCN

Rate coefficients and product distributions have been determined for reaction of the ions C(x)H(y)+ (x ranging from 1 to 4, and y ranging from 0 to 4) with C2H2 and HCN. The measurements were obtained using the ion cyclotron resonance technique at 298 K. In several reactions an association product was observed at pressures as low as 0.000001 torr, and in these cases stabilization of the intermediate was assumed to be by photon emission. Most of the reaction studied yield ions having a larger carbon skeleton than the reactant ion. These reactions provide routes for building large organic and organonitrogen molecules in combustion zones of unsaturated hydrocarbon flames and in astrochemical environments.

Anicich, V. G.↗
NASA NTRS1986

Nonmethane hydrocarbons in the troposphere - Impact on the odd hydrogen and odd nitrogen chemistry

A one-dimensional model is utilized to study the role of nonmethane hydrocarbons (NMHCs) in tropospheric chemistry. The effects of NMHCs on tropospheric peroxyacetyl nitrate (PAN) formation are analyzed; the global distribution and seasonal variability of PAN in the troposphere of the Northern and Southern Hemispheres are examined. The NMHC-PAN measurements obtained by model simulations are compared to the photochemical theory. The seasonal cycles in NMHC abundances are predicted, and their effects on other tropospheric species are investigated.

Kasting, James F.↗
NASA NTRS1987

Anharmonicity and the interstellar polycyclic aromatic hydrocarbon infrared emission spectrum

The hypothesis that interstellar infrared emission originates from vibrationally excited polycyclic aromatic hydrocarbons (PAHs) requires that emission can arise from all vibrational levels that are energetically accessible. Due to anharmonicity, the emission from the upper vibrational levels is shifted to longer wavelengths from that of the v = 1-0 transition. It is shown that structure in the 3-micron region is readily and quantitatively explained by emission from upper vibrational levels of excited PAHs that contain a maximum of 20-30 carbon atoms. The asymmetrical broadening of the 11.3-micron emission band may also be due to anharmonicity.

Barker, John R.↗
NASA NTRS1987

Interstellar polycyclic aromatic hydrocarbons and carbon in interplanetary dust particles and meteorites

Raman spectra of interplanetary dust particles (IDPs) and meteorites containing material similar to polycyclic aromatic hydrocarbons (PAHs) show features that are similar in position and relative strength to interstellar IR emission features attributable to vibrational transitions in free molecular-sized PAHs. In addition, these spectra sometimes show red photoluminescence that has elsewhere been attributed to PAHs, and a part of the carbonaceous phase in IDPs and meteorites contain a degree of deuterium enrichment anticipated in small, free PAHs that are exposed to ISM UV radiation. These observations suggest that some of the IDPs' carbonaceous material may have been produced in circumstellar dust shells, and only slightly modified in interstellar space.

Allamandola, L. J.↗
NASA NTRS1987

Carbon deposition model for oxygen-hydrocarbon combustion, volume 1

Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at pressures of 1000 to 1500 psia. No carbon deposition on the chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational consequences of carbon deposition on preburner/gas generator performance. The report is in two volumes, of which this is Volume 1 covering the main body of the report plus Appendixes A through D.

Hernandez, R.↗
NASA NTRS1987

Carbon Deposition Model for Oxygen-Hydrocarbon Combustion, Volume 2

Presented are details of the design, fabrication, and testing of subscale hardware used in the evaluation of carbon deposition characteristics of liquid oxygen and three hydrocarbon fuels for both main chamber and preburner/gas generator operating conditions. In main chamber conditions, the deposition of carbon on the combustion chamber wall was investigated at mixture ratios of 2.0 to 4.0 and at chamber pressures of 1000 to 1500 psia. No carbon deposition on chamber walls was detected at these main chamber mixture ratios. In preburner/gas generator operating conditions, the deposition of carbon on the turbine simulator tubes was evaluated at mixture ratios of 0.20 to 0.60 and at chamber pressures of 720 to 1650 psia. The results of the tests showed carbon deposition rate to be a strong function of mixture ratio and a weak function of chamber pressure. Further analyses evaluated the operational concequences of carbon deposition on preburner/gas generator performance. This is Volume 2 of the report, which contains data plots of all the test programs.

Hernandez, R.↗