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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 361 records · Page 20
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

The effect of preheat on the structure of a swirl stabilized flame

The effect of preheat on the temperature and species distributions in propane flames stabilized on a NASA contraswirl can has been examined. Flames with compact stable structure, inner-swirler airflow of 0.0091 kg/s, outer-swirler-plus-bypass airflow of 0.0203 kg/s, and propane injected 1 mm upstream of the inner swirler hub have been selected for detailed study. Over the inlet-air-temperature range from 300 to 673 K the maximum temperature in the flame increased by 40 to 60 K per 100-K increase in inlet air temperature. The point of maximum temperature on the center line approached the exit plane as inlet air temperature was increased. Oxygen, CO, H2, and methane were found together in gas samples taken from the flame, including the regions of maximum flame temperature.

Thompson, D.↗
NASA NTRS1978

Flame characteristics of a NASA contra swirler module

Results are presented for an investigation of the structure of unconfined propane flames stabilized on a NASA contra-swirl can. General flame characterization, flame visualization by sodium chloride, temperature measurements, combustion products analysis, nitric oxide concentrations, and laser anemometer studies are considered. The results are discussed relative to sodium chloride visualization, temperature distributions, chemical composition of flames, nitric oxide distributions, and velocity distributions. It is shown that unconfined propane-air flames can be stabilized downstream of a NASA contra-swirl can under a wide range of airflow rates and fuel-air ratios. However, on increasing fuel input from the lowest at which flames can be stabilized, a compact recirculation zone-stabilized flame is formed. The effect of confinement on changes in flame shape and structure is determined.

Thompson, D.↗
NASA NTRS1979

Photographic combustion characterization of LOX/hydrocarbon type propellants

Single element injectors and two fuels were tested with the aim of photographically characterizing observed combustion phenomena. The three injectors tested were the O-F-O triplet, the transverse like on like (TLOL), and the rectangular unlike doublet (RUD). The fuels tested were RP-1 and propane. The hot firings were conducted in a specifically constructed chamber fitted with quartz windows for photographically viewing the impingement spray field. All LOX/HC testing demonstrated coking with the RP-1 fuel leaving far more soot than the propane fuel. No fuel freezing or popping was experienced under the test conditions evaluated. Carbon particle emission and combustion light brilliance increased with Pc for both fuels although RP-1 was far more energetic in this respect. The RSS phenomena appear to be present in the high Pc tests as evidenced by striations in the spray pattern and by separate fuel rich and oxidizer rich areas. The RUD element was also tested as a fuel rich gas generator element by switching the propellant circuits. Excessive sooting occurred at this low mixture ratio (0.55), precluding photographic data.

Judd, D. C.↗
NASA NTRS1979

An analytical study of nitrogen oxides and carbon monoxide emissions in hydrocarbon combustion with added nitrogen, preliminary results

The effect of combustor operating conditions on the conversion of fuel-bound nitrogen (FBN) to nitrogen oxides NO sub x was analytically determined. The effect of FBN and of operating conditions on carbon monoxide (CO) formation was also studied. For these computations, the combustor was assumed to be a two stage, adiabatic, perfectly-stirred reactor. Propane-air was used as the combustible mixture and fuel-bound nitrogen was simulated by adding nitrogen atoms to the mixture. The oxidation of propane and formation of NO sub x and CO were modeled by a fifty-seven reaction chemical mechanism. The results for NO sub x and CO formation are given as functions of primary and secondary stage equivalence ratios and residence times.

Bittker, D. A.↗
NASA NTRS1980

Chemical kinetic models for combustion of hydrocarbons and formation of nitric oxide

The formation of nitrogen oxides NOx during combustion of methane, propane, and a jet fuel, JP-4, was investigated in a jet stirred combustor. The results of the experiments were interpreted using reaction models in which the nitric oxide (NO) forming reactions were coupled to the appropriate hydrocarbon combustion reaction mechanisms. Comparison between the experimental data and the model predictions reveals that the CH + N2 reaction process has a significant effect on NO formation especially in stoichiometric and fuel rich mixtures. Reaction models were assembled that predicted nitric oxide levels that were in reasonable agreement with the jet stirred combustor data and with data obtained from a high pressure (5.9 atm (0.6 MPa)), prevaporized, premixed, flame tube type combustor. The results also suggested that the behavior of hydrocarbon mixtures, like JP-4, may not be significantly different from that of pure hydrocarbons. Application of the propane combustion and nitric oxide formation model to the analysis of NOx emission data reported for various aircraft gas turbines showed the contribution of the various nitric oxide forming processes to the total NOx formed.

Jachimowski, C. J.↗
NASA NTRS1981

Testing of aircraft passenger seat cushion materials. Full scale, test description and results, volume 1

Eight different seat cushion configurations were subjected to full-scale burn tests. Each cushion configuration was tested twice for a total of sixteen tests. Two different fire sources were used. They consisted of one liter of Jet A fuel for eight tests and a radiant energy source with propane flame for eight tests. Both fire sources were ignited by a propane flame. During each test, data were recorded for smoke density, cushion temperatures, radiant heat flux, animal response to combustion products, rate of weight loss of test specimens, cabin temperature, and for the type and content of gas within the cabin atmosphere. When compared to existing passenger aircraft seat cushions, the test specimens incorporating a fire barrier and those fabricated from advanced materials, using improved construction methods, exhibited significantly greater fire resistance.

Schutter, K. J.↗
NASA NTRS1982

Effects of heat loss, preferential diffusion, and flame stretch on flame-front instability and extinction of propane/air mixtures

Flame configurations, flame-front cellular instability, and extinction of propane/air mixtures in the stagnation-point flow are experimentally studied for their dependence on downstream heat loss, preferential diffusion, and flame stretch. Boundaries for lean- and rich-limit extinction, stabilization of corrugated flames, and local extinction caused by sharp curvatures are mapped for varying propane concentrations and freestream velocities. Flame location and temperature at extinction are determined as functions of stagnation surface temperature, extent of preheating, propane concentration, and freestream velocity. Results substantiate the theoretical predictions of the different extinction modes for lean and rich flames in the absence of downstream heat loss, and yield useful insight on the extinction characteristics when finite downstream heat loss does exist. It is further shown that flame-front instability occurs only for rich mixtures in accordance with preferential diffusion considerations, and that flame stretch has a stabilizing effect such that flame-front instability is completely inhibited before the onset of extinction.

Ishizuka, S.↗
NASA NTRS1983

Combustion performance and heat transfer characterization of LOX/hydrocarbon type propellants

An evaluation liquid oxygen (LOX) and various hydrocarbon fuels as low cost alternative propellants suitable for future space transportation system applications was done. The emphasis was directed toward low earth orbit maneuvering engine and reaction control engine systems. The feasibility of regeneratively cooling an orbit maneuvering thruster was analytically determined over a range of operating conditions from 100 to 1000 psia chamber pressure and 1000 to 10,000-1bF thrust, and specific design points were analyzed in detail for propane, methane, RP-1, ammonia, and ethanol; similar design point studies were performed for a film-cooled reaction control thruster. Heat transfer characteristics of propane were experimentally evaluated in heated tube tests. Forced convection heat transfer coefficients were determined. Seventy-seven hot firing tests were conducted with LOX/propane and LOX/ethanol, for a total duration of nearly 1400 seconds, using both heat sink and water-cooled calorimetric chambers. Combustion performance and stability and gas-side heat transfer characteristics were evaluated.

Michel, R. W.↗
NASA NTRS1984

Spontaneous ignition characteristics of gaseous hydrocarbon-air mixtures

Experiments are conducted to determine the spontaneous ignition delay times of gaseous propane, kerosine vapor, and n-heptane vapor in mixtures with air, and oxygen-enriched air, at atmospheric pressure. Over a range of equivalence ratios from 0.2 to 0.8 it is found that ignition delay times are sensibly independent of fuel concentration. However, the results indicate a strong dependence of delay times on oxygen concentration. The experimental data for kerosine and propane demonstrate very close agreement with the results obtained previously by Mullins and Lezberg respectively.

Freeman, G.↗
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 NTRS1985

Combustion efficiency of a premixed continuous flow combustor

Exhaust gas temperature, velocity, and composition measurements at various radial locations at the combustor exit are presented for a swirling-flow continuous combustor of a confined concentric jet configuration operating on premixed propane or methane and air. The main objective of the study is to determine the effect of fuel substitution and of changes in outer flow swirl conditions on the combustor performance. It is found that there is no difference in observed properties for propane and methane firing; the use of either of the fuels results in nearly the same exit temperature and velocity profiles and the same efficiency for a given operating condition. A mechanism for combustion is proposed which explains qualitatively the changes in efficiency and pollutant emissions observed with changing swirl.

Anand, M. S.↗
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 NTRS1987

Measurement of methane and other light hydrocarbons in the troposphere and lower stratosphere

The volume mixing ratios of methane, acetylene, ethane, and propane were measured in the troposphere and stratosphere on April 5, 1984, at 33 deg N, over New Mexico, using the technique of grab sampling by evacuated spheres on a balloon platform. Tropospheric volume mixing ratios were CH4, 1.59 ppm; C2H2, 358 ppt (parts per trillion); C2H6, 365 ppt; and C3H8, 1440 ppt. In the stratosphere, acetylene was 60 ppt. For ethane and propane the mixing ratios at 11.6 km were 441 ppt and 84 ppt, respectively.

Aikin, A. C.↗
NASA NTRS1990

Low dielectric fluorinated poly(phenylene ether ketone) film and coating

The present invention relates to film and coating materials prepared from novel fluorinated poly(phenylene ether ketones). A fluorinated poly(phenylene ether ketone) is prepared by reacting a bisphenol with 1,1,1,3,3,3 hexafluoro-2,2-bis 4-(4-halobenzoyl) phenyl propane (wherein halo is fluoro or chloro), which is a novel monomer formed as the reaction product of halobenzene (wherein halo is fluoro or chloro) and 1,1,1,3,3,3 hexafluoro-2,2-bis (p-chloro formyl phenyl) propane. Especially beneficial results of this invention are that films and coating materials prepared from the novel fluorinated poly(phenylene ether ketone) are essentially optically transparent/colorless and have a lower dielectric constant than otherwise comparable, commercially available poly(phenylene ether ketones). Moreover, unlike the otherwise comparable commercially available materials, the novel fluorinated poly(phenylene ether ketones) of the present invention can be solution cast or sprayed to produce the films and coatings. Furthermore, the long term thermal stability of the polymers of the present invention is superior to that of the commercially available materials.

Cassidy, Patrick E.↗
NASA NTRS1952

An active particle diffusion theory of flame quenching for laminar flames / Dorothy M. Simon and Frank E. Belles

An equation for quenching distance based on the destruction of chain carriers by the surface is derived. The equation expresses the quenching distance in terms of the diffusion coefficients and partial pressures of the chain carriers and gas phase molecules, the efficiency of the surface as a chain breaker, the total pressure of the mixture, and a constant which depends on the geometry of the quenching surface. Quenching distances measured by flashback for propane-air flames are shown to be consistent with the mechanism. The derived equation is used with the lean inflammability limit and a rate constant calculated from burning velocity data to estimate quenching distances for propane-air (hydrocarbon lean) flames satisfactorily.

Simon, Dorothy M↗
NASA NTRS1993

Design of a vehicle based system to prevent ozone loss

Reduced quantities of ozone in the atmosphere allow greater levels of ultraviolet light (UV) radiation to reach the earth's surface. This is known to cause skin cancer and mutations. Chlorine liberated from Chlorofluorocarbons (CFC's) and natural sources initiate the destruction of stratospheric ozone through a free radical chain reaction. The project goals are to understand the processes which contribute to stratospheric ozone loss, examine ways to prevent ozone loss, and design a vehicle-based system to carry out the prevention scheme. The 1992/1993 design objectives were to accomplish the first two goals and define the requirements for an implementation vehicle to be designed in detail starting next year. Many different ozone intervention schemes have been proposed though few have been researched and none have been tested. A scheme proposed by R.J. Cicerone, Scott Elliot and R.P.Turco late in 1991 was selected because of its research support and economic feasibility. This scheme uses hydrocarbon injected into the Antarctic ozone hole to form stable compounds with free chlorine, thus reducing ozone depletion. Because most polar ozone depletion takes place during a 3-4 week period each year, the hydrocarbon must be injected during this time window. A study of the hydrocarbon injection requirements determined that 100 aircraft traveling Mach 2.4 at a maximum altitude of 66,000 ft. would provide the most economic approach to preventing ozone loss. Each aircraft would require an 8,000 nm. range and be able to carry 35,000 lbs. of propane. The propane would be stored in a three-tank high pressure system. Missions would be based from airport regions located in South America and Australia. To best provide the requirements of mission analysis, an aircraft with L/D(sub cruise) = 10.5, SFC = 0.65 (the faculty advisor suggested that this number is too low) and a 250,000 lb TOGW was selected as a baseline. Modularity and multi-role functionality were selected to be key design features. Modularity provides ease of turnaround for the down-time critical mission. Multi-role functionality allows the aircraft to be used beyond its design mission, perhaps as an High Speed Civil Transport (HSCT) or for high altitude research.

Lynn, Sean R.↗
NASA NTRS1994

Effects of biomass burning on summertime nonmethane hydrocarbon concentrations in the Canadian wetlands

Approximately 900 whole air samples were collected and assayed for selected C2-C10 hydrocarbons and seven halocarbons during the 5-week Arctic Boundary Layer Expedition (ABLE) 3B conducted in eastern Canadian wetland areas. In more than half of the 46 vertical profiles flown, enhanced nonmethane hydrocarbon (NMHC) concentrations attributable to plumes from Canadian forest fires were observed. Urban plumes, also enhanced in many NMHCs, were separately identified by their high correlation with elevated levels of perchloroethene. Emission factors relative to ethane were determined for 21 hydrocarbons released from Canadian biomass burning. Using these data for ethane, ethyne, propane, n-butane, and carbon monoxide enhancements from the literature, global emissions of these four NMHCs were estimated. Because of its very short atmospheric lifetime and its below detection limit background mixing ratio, 1,3-butadiene is an excellent indicator of recent combustion. No statistically significant emissions of nitrous oxide, isoprene, or CFC 12 were observed in the biomass-burning plumes encountered during ABLE 3B. The presence of the short-lived biogenically emitted isoprene at altitudes as high as 3000 m implies that mixing within the planetary boundary layer (PBL) was rapid. Although background levels of the longer-lived NMHCs in this Canadian region increase during the fire season, isoprene still dominated local hydroxyl radical photochemistry within the PBL except in the immediate vicinity of active fires. The average biomass-burning emission ratios for hydrocarbons from an active fire sampled within minutes of combustion were, relative to ethane, ethene, 2.45; ethyne 0.57; propane, 0.25; propene, 0.73; propyne, 0.06; n-butane, 0.09; i-butane, 0.01; 1-butene, 0.14; cis-2-butene, 0.02; trans-2-butene, 0.03; i-butylene, 0.07; 1,3-butadiene, 0.12; n-pentane, 0.05; i-pentane, 0.03; 1-pentene, 0.06; n-hexane, 0.05; 1-hexene, 0.07; benzene, 0.37; toluene, 0.16.

Blake, D. R.↗
NASA NTRS1966

Fully Deuterated Aliphatic Hydrocarbons Obtained From Iron Carbide Treated with DCl and D2O

According to Oparin, Mendeleev thought that the origin of petroleum was the result of the hydrolysis of iron carbides by superheated steam under pressure from the deep interior of the Earth through geological formations where the metal carbides exist. As early as 1877, Mendeleev described the reaction leading to the synthesis of hydrocarbons according to the general equation 3Fe(sub m)C(sub n) + mH2O yields mFe3O4 + C(sub 3n)H(sub 8m). Other experimental studies on the production of hydrocarbons from cast iron have been reported. Because of the possibility that hydrocarbons may have been trapped within the carbon matrix of the cast iron, which usually has a high content of carbon, we have studied the reaction of pure iron carbide with deuterium chloride and deuterated water. This was done in order to distinguish any newly formed deuterated hydrocarbons from any possible impurities of trapped hydrocarbons. The experiments were carried out by simply allowing iron carbide to react with concentrated deuterium chloride in D2O. The volatile hydrocarbon fraction examined by gas chromatography-mass spectrometry (GC/MS), using a Finnigan 1020/OWA instrument. contained low molecular weight hydrocarbons in a range C3 to C7. Lower molecular weight hydrocarbons were not detected by GC/MS because the MS scanning mode was preset above mass 40 to exclude components of air. The identified hydrocarbons are similar to those obtained under prebiotic conditions using high frequency discharge. The hydrocarbons found in common were propane, butane, pentane, 3-methylpentane, hexane, and heptane. The percent yields decline with increasing carbon number (propane 11%, n-heptane 1%). Similar results have been obtained by the direct treatment of metal carbides by pulse laser vaporization mass spectrometry. These results show that the hydrolysis of iron carbides may have been a significant source of hydrocarbons on the primitive Earth. There appears to be a predominance of straight chain isomers, which may have been important in the prebiotic synthesis of membrane-forming compounds.

Marquez, C.↗