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NASA NTRS1984

Radical and ion molecule mechanisms in the polymerization of hydrocarbons and chlorosilanes in RF plasmas at low pressures ( 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 NTRS1984

Evaluation of LANDSAT-D Thematic Mapper performance as applied to hydrocarbon exploration

Work with digital data of Oklahoma, Colorado, Wyoming, Utah and California demonstrate that the increased spectral refinement and spatial resolution of TM over MSS data greatly increase the value of the data to petroleum exploration in roles ranging from logistic planning to direct detection of phenomena related to microseepage of hydrocarbons. The value of the spatial content versus the spectral content of the data increases as soil and vegetation cover increase. The structural detail visible in the imagery can contribute to exploration at the prospect level. Examination of the variance/covariance matrix suggests that a combination of bands 1, 4, and 5 displays the most information for most areas.

Dykstra, J. D.↗

NASA NTRS1983

A modeling study of SO(x)-NO(x)-hydrocarbon plumes and their transport to the background troposphere

The behavior of a complex urban plume and its transport to the background troposphere are analyzed in terms of a model including sulfur oxide, nitrogen oxide and hydrocarbon (HC) photochemistry. A reaction mechanism consisting of 73 NO(x), SO(x) and HC reactions is employed in a model taking account of plume dilution, entrainment, deposition and the development of a diurnal mixing layer from a ground-based nocturnal inversion. When simulation results are compared with field measurements of the urban plumes leaving St. Louis and Milwaukee, and a power plant within the Milwaukee plume, the predicted concentration profiles of NO(x), SO2 and O3 are found to be in close agreement with the measurement, although agreement with the rate of transformation of SO2 to SO4(2-) is less good. Simulations made for a hypothetical urban location under a range of background concentrations and initial HC concentrations show particulate sulfate concentrations to depend strongly on the HC/NO(x) ratio, indicating that the homogeneous gas-phase transformation may occur at night.

Balko, J. A.↗

NASA NTRS1984

Deposit formation and heat transfer in hydrocarbon rocket fuels

An experimental research program was undertaken to investigate the thermal stability and heat transfer characteristics of several hydrocarbon fuels under conditions that simulate high-pressure, rocket engine cooling systems. The rates of carbon deposition in heated copper and nickel-plated copper tubes were determined for RP-1, propane, and natural gas using a continuous flow test apparatus which permitted independent variation and evaluation of the effect on deposit formation of wall temperature, fuel pressure, and fuel velocity. In addition, the effects of fuel additives and contaminants, cryogenic fuel temperatures, and extended duration testing with intermittent operation were examined. Corrosion of the copper tube surface was detected for all fuels tested; however, plating the insides of the tubes with nickel reduced deposit formation and eliminated corrosion in most cases. The lowest rates of carbon deposition were obtained for natural gas, and the highest rates were obtained for propane. Forced-convection heat transfer film coefficients were satisfactorily correlated using a Nusselt-Reynolds-Prandtl number equation for all the fuels tested.

Giovanetti, A. J.↗

NASA NTRS1983

Distribution, abundance and carbon isotopic composition of gaseous hydrocarbons in Big Soda Lake, Nevada - An alkaline, meromictic lake

The study of the distribution and isotopic composition of low molecular weight hydrocarbon gases at the Big Soda Lake, Nevada, has shown that while neither ethylene nor propylene were found in the lake, ethane, propane, isobutane and n-butane concentrations all increased with water column depth. It is concluded that methane has a biogenic origin in both the sediments and the anoxic water column, and that C2-C4 alkanes have biogenic origins in the monimolimnion water and shallow sediments. The changes observed in delta C-13/CH4/ and CH4/(C2H6 + C3H8) with depth in the water column and sedimeents are probably due to bacterial processes, which may include anaerobic methane oxidation and different rates of methanogenesis, and C2-to-C4 alkane production by microorganisms.

Oremland, R. S.↗

NASA NTRS1983

Computations and estimates of rate coefficients for hydrocarbon reactions of interest to the atmospheres of outer solar system

The rate coefficients, including Arrhenius parameters, have been computed for a number of chemical reactions involving hydrocarbon species for which experimental data are not available and which are important in planetary atmospheric models. The techniques used to calculate the kinetic parameters include the Troe and semiempirical bond energy-bond order (BEBO) or bond strength-bond length (BSBL) methods.

Laufer, A. H.↗

NASA NTRS1983

Remote sensing of oceanographic parameters pertinent to hydrocarbon resource development

Information obtained from remotely sensed imagery which is potentially useful to hydrocarbon resource development is discussed in this paper. Oceanic phenomena presented include surface gravity waves, detection of bathymetric features, and deep ocean internal waves. Techniques used to extract data are presented along with pertinent examples.

Kasischke, E. S.↗

NASA NTRS1984

Systematic data interpretation of remote sensing in the reception of hydrocarbons, volume 1

The utilization of MSS-LANDSAT and RADAR imagery in the definition of morphostructural anomalies, which are indicative of hydrocarbon entrapment sites in the limit of the Middle and Lower Amazons basins was systemized. The identification and classification of the morphostructural anomalies were accomplished by means of the drainage network interpretation, based on the criteria previously proposed. Thirty anomalies were recognized, being subdivided into twenty domes, two fault controlled domes, six structural depressions, one fault controlled structural depression and one structure developed on a tilted fault block. Many anomalies are not randomly located. Rather, they seem to be aligned according to directions ENE and NNW, suggesting the presence of morphstructural trends in this part of the Amazons Basin. Significant orientations of lineaments were determined through statistical analysis, which defined many regional trends. The directions coincide with morphostructural trends orientations and with the directions of important structures in the Precambrian basement.

Demiranda, F. P.↗

NASA NTRS1985

Evaluation of Thematic Mapper Performance as Applied to Hydrocarbon Exploration

The role data from the first three LANDSAT satellites have in geologic exploration and their current level of acceptance is reviewed and the advantages of LANDSAT 4 TM data over MSS data are discussed. Specially enhanced Thematic Mapper imager can make a very significant contribution to the oil and gas and mineral exploration industries. The TM's increased spatial resolution enables the production of larger scale imagery, which greatly increases the amount of geomorphic and structural information interpretable. TM's greater spectral resolution, combined with the smaller, more homogeneous pixels, should enable a far greater confidence in mapping lithologies and detecting geobotanical anomalies from space. The results from its applications to hydrocarbon and mineral exploration promise to bring the majority of the geologic exploration community into that final stage of acceptance and routine application of the satellite data.

Everett, J. R.↗

NASA NTRS1985

Polycyclic aromatic hydrocarbons and the unidentified infrared emission bands - Auto exhaust along the Milky Way

The unidentified infrared emission features (UIR bands) are attributed to a collection of partially hydrogenated, positively charged polycyclic aromatic hydrocarbons (PAHs). This assignment is based on a spectroscopic analysis of the UIR bands. Comparison of the observed interstellar 6.2 and 7.7-micron bands with the laboratory measured Raman spectrum of a collection of carbon-based particulates (auto exhaust) shows a very good agreement, supporting this identification. The infrared emission is due to relaxation from highly vibrationally and electronically excited states. The excitation is probably caused by UV photon absorption. The infrared fluorescence of one particular, highly vibrationally excited PAH (chrysene) is modeled. In this analysis the species is treated as a molecule rather than bulk material and the non-thermodynamic equilibrium nature of the emission is fully taken into account. From a comparison of the observed ratio of the 3.3 to 11.3-micron UIR bands with the model calculations, the average number of carbon atoms per molecule is estimated to be about 20. The abundance of interstellar PAHs is calculated to be about 2 x 10 to the -7th with respect to hydrogen.

Allamandola, L. J.↗

NASA NTRS1985

Polycyclic aromatic hydrocarbons and the diffuse interstellar bands

This paper discusses some of the thermodynamic and spectroscopic properties of polycyclic aromatic hydrocarbons which make them attractive candidates as carriers of the Diffuse Interstellar Bands (DIBs). It is pointed out that, in the diffuse medium, many of these species will be partially hydrogenated and positively charged, and will absorb in the visible. The observed lineshapes and widths of the DIBs can be explained by rovibronic band contours and linebroadening due to internal conversion. Since little information is available concerning the spectroscopic properties of such species in the gas phase, a considerable amount of laboratory and theoretical work is needed.

Van Der Zwet, G. P.↗

NASA NTRS1985

Ionized polycyclic aromatic hydrocarbons and the diffuse interstellar bands

A good case has recently been made that the unidentified infrared emission features arise from positively charged, partially hydrogenated polycyclic aromatic hydrocarbons (PAHs). In this letter it is suggested that these exceedingly stable ions are also the carriers of the diffuse interstellar bands. Although a large variety of PAH isomers is possible, the more condensed forms are substantially more stable than the less condensed forms and are expected to be dominant in the harsh interstellar environment. While neutral PAHs do not absorb in the visible, their ionized counterparts do. Because of their low ionization potential, a substantial fraction of the interstellar PAHs will be ionized. Visible spectra of the most stable PAH cations isolated in glasses are compared directly to the interstellar band spectra. Although the laboratory spectra are on an extremely compressed scale and solid state shifts are present, the comparison is favorable. Since little information is available concerning the spectroscopic properties of these species in the gas phase, a considerable amount of laboratory and theoretical work is called for to test this hypothesis.

Crawford, M. K.↗

NASA NTRS1985

A simplified hydrocarbon reaction mechanism for combustion applications

A simplified chemical kinetic reaction mechanism for the combustion of a hydrocarbon fuel is presented and discussed. The observed kinetic behavior of propane combustion as determined in shock tube studies and the calculated kinetic behavior of propane/air mixtures as derived from a detailed propane combustion mechanism were used as a data base for constructing and refining the mechanism. The mechanism contains 13 chemical species and 26 chemical reactions. Numerical studies revealed that the simplified mechanism can reproduce the observed kinetic behavior of propane/air mixtures, including laminar flame speeds, over a wide range of temperatures and pressures. It is anticipated that the mechanism can be used in various combustion applications and provide a more realistic description of the combustion process than can be achieved using global reaction mechanisms.

Jachimowski, C. J.↗

NASA NTRS1986

Spontaneous ignition delay characteristics of hydrocarbon fuel-air mixtures

The influence of pressure on the autoignition characteristics of homogeneous mixtures of hydrocarbon fuels in air is examined. Autoignition delay times are measured for propane, ethylene, methane, and acetylene in a continuous flow apparatus featuring a multi-point fuel injector. Results are presented for mixture temperatures from 670K to 1020K, pressures from 1 to 10 atmospheres, equivalence ratios from 0.2 to 0.7, and velocities from 5 to 30 m/s. Delay time is related to pressure, temperature, and fuel concentration by global reaction theory. The results show variations in global activation energy from 25 to 38 kcal/kg-mol, pressure exponents from 0.66 to 1.21, and fuel concentration exponents from 0.19 to 0.75 for the fuels studied. These results are generally in good agreement with previous studies carried out under similar conditions.

Lefebvre, A. H.↗

NASA NTRS1986

Ionized polycyclic aromatic hydrocarbons in space

The mid-infrared spectrum of a continuously increasing number of stellar objects, planetary and reflection nebulae, H-II regions and extragalactic sources show a distinctive set of broad emission features at 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 micron known collectively as the unidentified infrared emission bands. A model is summarized in which the bands arise from positively charged polycyclic hydrocarbons (PAH's) on the basis of their low ionization potential and the excellent agreement between the emission bands and laboratory spectra of auto exhaust which contains these types of molecules. The proposed presence of PAHs in such a variety of objects points to their presence in the interstellar medium. Out of a previously published collection of solid state PAH radical cation spectra five were selected on the basis of the unique thermodynamic stability of their carrier and compared directly to the wavelengths of the DIB's. Although the match seems quite favorable, strongly suggesting that PAH radicals are the long sought after carrier of the diffuse interstellar absorption bands, much laboratory work must be done to test this hypothesis.

Barker, J.↗

NASA NTRS1986

Are aromatic hydrocarbons the carriers of the diffuse interstellar bands in the visible?

Large Polycyclic Aromatic Hydrocarbons (PAH) are the likely origin of the Unidentified Infrared Emission Feature. The molecules or their ions are also attractive candidates for the carriers of the Diffuse Interstellar Bands (DIBs) in the visible range. The PAHs have optically active transitions in the visible spectrum; have the ability to survive the ultraviolet photons in the Diffuse Interstellar Medium; and are the most abundant among the detected molecular species after H2 and CO. In particular, PAHs are better candidates than the long carbon chains that were proposed previously.

Leger, A.↗

NASA NTRS1986

Fire control method and analytical model for large liquid hydrocarbon pool fires

The dominate parameter governing the behavior of a liquid hydrocarbon (JP-5) pool fire is wind speed. The most effective method of controlling wind speed in the vicinity of a large circular (10 m dia.) pool fire is a set of concentric screens located outside the perimeter. Because detailed behavior of the pool fire structure within one pool fire diameter is unknown, an analytical model supported by careful experiments is under development. As a first step toward this development, a regional pool fire model was constructed for the no-wind condition consisting of three zones -- liquid fuel, combustion, and plume -- where the predicted variables are mass burning rate and characteristic temperatures of the combustion and plume zones. This zone pool fire model can be modified to incorporate plume bending by wind, radiation absorption by soot particles, and a different ambient air flow entrainment rate. Results from the zone model are given for a pool diameter of 1.3 m and are found to reproduce values in the literature.

Fenton, D. L.↗

NASA NTRS1986

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

An experimental program has been planned at the NASA Lewis Research Center to build confidence in the feasibility of liquid oxygen cooling for hydrocarbon fueled rocket engines. Although liquid oxygen cooling has previously been incorporated in test hardware, more runtime is necessary to gain confidence in this concept. In the previous tests, 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 catastrophic 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 in this report. Four thrust chambers, three with cracks and one without, should be tested. The axial location of the cracks should be varied parametrically. Each chamber should be instrumented to determine the effects of the cracks, as well as the overall performance and durability of the chambers.

Armstrong, E. S.↗