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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Lean combustion limits of a confined premixed-prevaporized propane jet

An experimental study was carried out to determine the effects of jet velocity and confinement on lean premixed-prevaporized propane/air blowout limits. The combustor consisted of a single hole flameholder within a quartz liner. Five flameholder plates and two quartz liners were used. Lean stability limits were mapped for confined propane jet in cylindrical combustor. Three zones of flame stability were observed depending on the liner and jet Reynolds number and the combustor geometry. At low Reynolds number the combustor was jet stabilized. As the Reynolds number was increased the combustor became either recirculation zone stabilized, or for small recirculation zone step sizes, the combustor was wall stabilized. The factors affecting stability seem to be the Reynolds numbers of the liner and inlet jet along with the flameholder step size. Stability was achieved at both laminar and turbulent conditions.

Huck, K. L.↗
NASA NTRS1982

Exhaust gas measurements in a propane fueled swirl stabilized combustor

Exhaust gas temperature, velocity, and composition are measured and combustor efficiencies are calculated in a lean premixed swirl stabilized laboratory combustor. The radial profiles of the data between the co- and the counter swirl cases show significant differences. Co-swirl cases show evidence of poor turbulent mixing across the combustor in comparison to the counter-swirl cases. NO sub x levels are low in the combustor but substantial amounts of CO are present. Combustion efficiencies are low and surprisingly constant with varying outer swirl in contradiction to previous results under a slightly different inner swirl condition. This difference in the efficiency trends is expected to be a result of the high sensitivity of the combustor to changes in the inner swirl. Combustor operation is found to be the same for propane and methane fuels. A mechanism is proposed to explain the combustor operation and a few important characteristics determining combustor efficiency are identified.

Aanad, M. S.↗
NASA NTRS1983

Effects of percentage of blockage and flameholder downstream counterbores on lean combustion limits of premixed, prevaporized propane-air mixture

Lean combustion limits were determined for a premixed prevaporized propane air mixture with flat plate flame stabilizers. Experiments were conducted in a constant area flame tube combustor utilizing flameholders of varying percentages of blockage and downstream counterbores. Combustor inlet air velocity at ambient conditions was varied from 4 to 9 meters per second. Flameholders with a center hole and four half holes surrounding it were tested with 63, 73, and 85 percent blockage and counterbore diameters of 112 and 125 percent of the thru hole diameter, in addition to the no counterbore configuration. Improved stability was obtained by using counterbore flameholders and higher percentages of blockage. Increases in mixture velocity caused the equivalence ratio at blowout to increase in all cases.

Fernandez, M. A. B.↗
NASA NTRS1984

Chemical kinetic reaction mechanism for the combustion of propane

A detailed chemical kinetic reaction mechanism for the combustion of propane is presented and discussed. The mechanism consists of 27 chemical species and 83 elementary chemical reactions. Ignition and combustion data as determined in shock tube studies were used to evaluate the mechanism. Numerical simulation of the shock tube experiments showed that the kinetic behavior predicted by the mechanism for stoichiometric mixtures is in good agrement with the experimental results over the entire temperature range examined (1150-2600K). Sensitivity and theoretical studies carried out using the mechanism revealed that hydrocarbon reactions which are involved in the formation of the HO2 radical and the H2O2 molecule are very important in the mechanism and that the observed nonlinear behavior of ignition delay time with decreasing temperature can be interpreted in terms of the increased importance of the HO2 and H2O2 reactions at the lower temperatures.

Jachimowski, C. J.↗
NASA NTRS1984

Supercritical convection, critical heat flux, and coking characteristics of propane

The heat transfer characteristics of propane at subcritical and supercritical pressure were experimentally evaluated using electrically heated Monel K-500 tubes. A design correlation for supercritical heat transfer coefficient was established using the approach previously applied to supercritical oxygen. Flow oscillations were observed and the onset of these oscillations at supercritical pressures was correlated with wall-to-bulk temperature ratio and velocity. The critical heat flux measured at subcritical pressure was correlated with the product of velocity and subcooling. Long duration tests at fixed heat flux conditions were conducted to evaluate coking on the coolant side tube wall and coking rates comparable to RP-1 were observed.

Rousar, D. C.↗
NASA NTRS1990

Laboratory studies, analysis, and interpretation of the spectra of hydrocarbons present in planetary atmospheres including cyanoacetylene, acetylene, propane, and ethane

Combining broadband Fourier transform spectrometers (FTS) from the McMath facility at NSO and from NRC in Ottawa and narrow band TDL data from the laboratories with computational physics techniques has produced a broad range of results for the study of planetary atmospheres. Motivation for the effort flows from the Voyager/IRIS observations and the needs of Voyager analysis for laboratory results. In addition, anticipation of the Cassini mission adds incentive to pursue studies of observed and potentially observable constituents of planetary atmospheres. Current studies include cyanoacetylene, acetylene, propane, and ethane. Particular attention is devoted to cyanoacetylen (H3CN) which is observed in the atmosphere of Titan. The results of a high resolution infrared laboratory study of the line positions of the 663, 449, and 22.5/cm fundamental bands are presented. Line position, reproducible to better than 5 MHz for the first two bands, are available for infrared astrophysical searches. Intensity and broadening studies are in progress. Acetylene is a nearly ubiquitous atmospheric constituent of the outer planets and Titan due to the nature of methane photochemistry. Results of ambient temperature absolute intensity measurements are presented for the fundamental and two two-quantum hotband in the 730/cm region. Low temperature hotband intensity and linewidth measurements are planned.

Blass, William E.↗
NASA NTRS1990

Propane spectral resolution enhancement by the maximum entropy method

The Burg algorithm for maximum entropy power spectral density estimation is applied to a time series of data obtained from a Michelson interferometer and compared with a standard FFT estimate for resolution capability. The propane transmittance spectrum was estimated by use of the FFT with a 2 to the 18th data sample interferogram, giving a maximum unapodized resolution of 0.06/cm. This estimate was then interpolated by zero filling an additional 2 to the 18th points, and the final resolution was taken to be 0.06/cm. Comparison of the maximum entropy method (MEM) estimate with the FFT was made over a 45/cm region of the spectrum for several increasing record lengths of interferogram data beginning at 2 to the 10th. It is found that over this region the MEM estimate with 2 to the 16th data samples is in close agreement with the FFT estimate using 2 to the 18th samples.

Bonavito, N. L.↗
NASA NTRS1991

Numerical simulation of Jet-A combustion approximated by improved propane chemical kinetics

Through the effort devoted to the chemical kinetics for propane air combustion, three mechanisms are developed. The full mechanism consists of 131 reactions. This mechanism is used as a guide for the evaluation of other mechanisms, but because of the long expected cpu time, it is not to be incorporated into the computer code KIVA-II for actual simulation. Through the sensitivity analysis, a reduced mechanism of 45 reactions is produced. But the calculated results from the 45 reaction mechanism are always low in temperature. Some efforts are devoted to correct this situation and details are included in this report. A simplified mechanism of reactions is successfully improved and computed results are compared with experimental data. Contour plots of physical parameters and species concentrations and results for emission indices of CO and NOx are presented.

Ying, Shuh-Jing↗
NASA NTRS1991

A two-dimensional study of ethane and propane oxidation in the troposphere

The chemistry of ethane and propane is studied using a global two-dimensional 'zonally averaged' height- and latitude-dependent tropospheric model. The purpose of the study is to derive theoretical estimates of the seasonal and latitudinal distributions of a variety of intermediate organic compounds formed by the photochemical oxidation of C2H6 and C3H8. It is shown that C2H6 and C3H8 emitted at rates of 16 Tg C2H6/a and 23 Tg C3H8/a do not affect the overall photochemistry of the troposphere significantly. Major global effects on O3 and OH concentrations are suggested to be coming from the formation of peroxyacetyl nitrate by the interactions of NOx with other hydrocarbons with strong and spatially correlated anthropogenic or natural sources at the earth's surface. It is pointed out that attention should be given to organic nitrates produced by the oxidation of NMHC other than C2H6 and C3H8.

Kanakidou, M.↗
NASA NTRS1993

The promising chemical kinetics for the simulation of propane-air combustion with KIVA-II code

The development of chemical kinetics for the simulation of propane-air combustion with the use of computer code KIVA-II since 1989 is summarized here. In order to let readers understand the general feature well, a brief description of the KIVA-II code, specially related with the chemical reactions is also given. Then the results of recent work with 20 reaction mechanism is presented. It is also compared with the 5 reaction mechanism. It may be expected that the numerical stability of the 20 reaction mechanism is better as compared to that of 5 reaction mechanism, but the CPU time of the CRAY computer is much longer. Details are presented in the paper.

Ying, S. J.↗
NASA NTRS1954

Flame quenching by a variable-width rectangular-slot burner as a function of pressure for various propane-oxygen-nitrogen mixtures

Flame quenching by a variable-width rectangular-slot burner as a function of pressure for various propane-oxygen-nitrogen mixtures was investigated. It was found that for cold gas temperatures of 27 degrees C, pressures of 0.1 ro 1.0 atmosphere, and volumetric oxygen reactions of the oxidant of 0.17, 0.21, 0.30, 0.50, and 0.70, the relation between pressure p and quenching distance d is approximately given by d (unity) p (superscript -r) with r = 1, for equivalence ratios approximately equal to one. The quenching equation of Simon and Belles was tested. For equivalence ratios less than or equal to unity, this equation may by used, together with one empirical constant, to predict the observed quenching distance within 4.2 percent. The equation in it's present form does not appear to be suitable for values of the equivalence ratio greater than unity. A quantitative theoretical investigation has also been made of the error implicit in the assumption that flame quenching by plane parallel plates of infinite extent is equivalent to that of a rectangular burner. A curve is presented which relates the magnitude of this error to the length-to-width ratio of the rectangular burner.

COMBUSTION RESEARCH↗
NASA NTRS1949

Spark ignition of flowing gases I : energies to ignite propane-air mixtures in pressure range of 2 to 4 inches mercury absolute

Ignition studies of flowing gases were made to obtain information applicable to ignition problems in gas-turbine and ram-jet aircraft propulsion systems operating at altitude conditions.Spark energies required for ignition of a flowing propane-air mixture were determined for pressure of 2 to 4 inches mercury absolute, gas velocities of 5.0 to 54.2 feet per second, fuel-air ratios of 0.0607 to 0.1245, and spark durations of 1.5 to 24,400 microseconds. The results showed that at a pressure of 3 inches mercury absolute the minimum energy required for ignition occurred at fuel-air ratios of 0.08 to 0.095. The energy required for ignition increased almost linearly with increasing gas velocity. Shortening the spark duration from approximately 25,000 to 125 microseconds decreased the amount of energy required for ignition. A spark produced by the discharge of a condenser directly into the spark gap and having a duration of 1.5 microseconds required ignition energies larger than most of the long-duration sparks.

Swett, Clyde C , Jr↗
NASA NTRS2003

Cool Flames in Propane-Oxygen Premixtures at Low and Intermediate Temperatures at Reduced-Gravity

The Cool Flame Experiment aims to address the role of diffusive transport on the structure and the stability of gas-phase, non-isothermal, hydrocarbon oxidation reactions, cool flames and auto-ignition fronts in an unstirred, static reactor. These reactions cannot be studied on Earth where natural convection due to self-heating during the course of slow reaction dominates diffusive transport and produces spatio-temporal variations in the thermal and thus species concentration profiles. On Earth, reactions with associated Rayleigh numbers (Ra) less than the critical Ra for onset of convection (Ra(sub cr) approx. 600) cannot be achieved in laboratory-scale vessels for conditions representative of nearly all low-temperature reactions. In fact, the Ra at 1g ranges from 10(exp 4) - 10(exp 5) (or larger), while at reduced-gravity, these values can be reduced two to six orders of magnitude (below Ra(sub cr)), depending on the reduced-gravity test facility. Currently, laboratory (1g) and NASA s KC-135 reduced-gravity (g) aircraft studies are being conducted in parallel with the development of a detailed chemical kinetic model that includes thermal and species diffusion. Select experiments have also been conducted at partial gravity (Martian, 0.3gearth) aboard the KC-135 aircraft. This paper discusses these preliminary results for propane-oxygen premixtures in the low to intermediate temperature range (310- 350 C) at reduced-gravity.

Pearlman, Howard↗
NASA NTRS1988

Optical measurements of soot and temperature profiles in premixed propane-oxygen flames

Two laser diagnostic techniques were used to measure soot volume fractions, number densities and soot particle radii in premixed propane/oxygen flat flames. The two techniques used were two wavelength extinction, using 514.5 nm to 632.8 nm and 457.9 nm to 632.8 nm wavelength combinations, and extinction/scattering using 514.5 nm light. The flames wre fuel-rich (equivalence ratios from 2.1 to 2.8) and had cold gas velocities varying from 3.4 to 5.5 cm/s. Measurements were made at various heights above the sintered-bronze, water-cooled flat flame burner with the equivalence ratio and cold gas velocity fixed. Also, measurements were made at a fixed height above the burner and fixed cold gas velocity while varying the equivalence ratio. Both laser techniques are based on the same underlying assumptions of particle size distribution and soot optical properties. Full Mie theory was used to determine the extinction coefficients K sub ext, and the scattering efficiencies, Q sub vv. Temperature measurements in the flames were made using infrared radiometry. Good agreement between the two techniques in terms of soot particle radii, number density and volume fraction was found for intensity ratios (I/I sub o) between 0.1 and 0.8. For intensity ratios higher or lower than this range, the differences in extinction coefficients at the wavelengths chosen for the two-wavelength method are too small to give accurate results for comparing particle radii and number densities. However, when comparing only soot volume fractions, the agreement between the two techniques continued to be good for intensity ratios up to 0.95.

Lyons, Valerie J.↗
NASA NTRS1988

Optical measurements of soot and temperature profiles in premixed propane-oxygen flames

Two laser diagnostic techniques were used to measure soot volume fractions, number densities and soot particle radii in premixed propane/oxygen flat flames. The two techniques used were two wavelength extinction, using 514.5 nm to 632.8 nm and 457.9 nm to 632.8 nm wavelength combinations, and extinction/scattering using 514.5 nm light. The flames were fuel-rich (equivalence ratios from 2.1 to 2.8) and had cold gas velocities varying from 3.4 to 5.5 cm/s. Measurements were made at various heights above the sintered-bronze, water-cooled flat flame burner with the equivalence ratio and cold gas velocity fixed. Also, measurements were made at a fixed height above the burner and fixed cold gas velocity while varying the equivalence ratio. Both laser techniques are based on the same underlying assumptions of particle size distribution and soot optical properties. Full Mie theory was used to determine the extinction coefficients K sub ext, and the scattering efficiencies, Q sub vv. Temperature measurements in the flames were made using infrared radiometry. Good agreement between the two techniques in terms of soot particle radii, number density and volume fraction was found for intensity ratios (I/I sub o) between 0.1 and 0.8. For intensity ratios higher or lower than this range, the differences in extinction coefficients at the wavelengths chosen for the two-wavelength method are too small to give accurate results for comparing particle radii and number densities. However, when comparing only soot volume fractions, the agreement between the two techniques continued to be good for intensity ratios up to 0.95.

Lyons, V. J.↗