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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Jet Fuel Thermal Stability

Various aspects of the thermal stability problem associated with the use of broadened-specification and nonpetroleum-derived turbine fuels are addressed. The state of the art is reviewed and the status of the research being conducted at various laboratories is presented. Discussions among representatives from universities, refineries, engine and airframe manufacturers, airlines, the Government, and others are presented along with conclusions and both broad and specific recommendations for future stability research and development. It is concluded that significant additional effort is required to cope with the fuel stability problems which will be associated with the potentially poorer quality fuels of the future such as broadened specification petroleum fuels or fuels produced from synthetic sources.

Taylor, W. F.↗
NASA NTRS1978

Simulation study of the effect of fuel-conservative approaches on ATC procedures and terminal area capacity

Fuel-conservative procedures have been investigated using real-time air traffic control simulations linked to two piloted simulators. The fuel-conservative procedures studied were profile descents and two types of landing approaches. The investigation determined the effect of these procedures on the ATC system and terminal area capacity. It examined the mixing of aircraft executing fuel-conservative approaches with those executing conventional approaches. The results indicate a systems fuel savings for the landing approaches under all tested conditions except at, or near, maximum system capacity. Also, there is a fuel savings and reduced controller workload for the profile descent procedures.

Tobias, L.↗
NASA NTRS1977

Alternative aviation turbine fuels

The efficient utilization of fossil fuels by future jet aircraft may necessitate the broadening of current aviation turbine fuel specifications. The most significant changes in specifications would be an increased aromatics content and a higher final boiling point in order to minimize refinery energy consumption and costs. These changes would increase the freezing point and might lower the thermal stability of the fuel and could cause increased pollutant emissions, increased smoke and carbon formation, increased combustor liner temperatures, and poorer ignition characteristics. This paper discusses the effects that broadened specification fuels may have on present-day jet aircraft and engine components and the technology required to use fuels with broadened specifications.

Grobman, J.↗
NASA NTRS1979

A partial oxidation staging concept for gas turbines using broadened specification fuels

A concept is described for using a very fuel-rich partial oxidation process as the first stage of a two-stage combustion system for onboard processing of broadened specification fuels to improve their combustion characteristics. Results of an initial step in the experimental verification of the concept are presented, where the basic benefits of H2 enrichment are shown to provide extended lean-combustion limits and permit simultaneous achievement of ultralow levels of NOx, CO, and HC emissions. The H2 required to obtain these results is within the range available from a partial oxidation precombustion stage. Operation of a catalytic partial oxidation reactor using a conventional aviation turbine fuel (JP5) and an unconventional fuel (blend of JP5/xylene) is shown to produce a 'fuel gas' stream with near-theoretical equilibrium H2 content. However, a number of design considerations indicate that the precombustion stage should be incorporated as a thermal reaction.

Clayton, R. M.↗
NASA NTRS1979

Simulation study of the operational effects of fuel-conservative approaches

Fuel-conservative procedures have been investigated using real-time air traffic control simulations linked to two piloted simulators. The fuel-conservative procedures studied were profile descents and two types of landing approaches, delayed flap and IATA. The investigation determined the effect of these procedures on the ATC system operation. It examined the mixing of aircraft executing fuel-conservative approaches with those executing conventional approaches. The most difficult approach type mix of traffic was found to be 50% conventional and 50% delayed flap. However, for the test scenario chosen, arrival rates of at least 30 aircraft per hour were feasible and resulted in a net average fuel saving, even for the most difficult mix. Also, there is a fuel savings and reduced controller workload for the profile descent procedures.

Tobias, L.↗
NASA NTRS1979

The role of fuel cells in NASA's space power systems

The advances in fuel cell technology which have expanded the capabilities of the fuel cell from that of power generation to include energy storage also expanded its potential role in space power systems. This paper presents a brief evolutionary history of the fuel cell technology and compares this with NASA's increasing space power requirements. The role of fuel cells is put in perspective with other energy storage systems applicable for space using such criteria as type of mission, weight, reliability, costs, etc. Potential applications of space fuel cells with projected technology advances are examined.

Been, J. F.↗
NASA NTRS1980

Aviation fuels outlook

Options for satisfying the future demand for commercial jet fuels are analyzed. It is concluded that the most effective means to this end are to attract more refiners to the jet fuel market and encourage development of processes to convert oil shale and coal to transportation fuels. Furthermore, changing the U.S. refineries fuel specification would not significantly alter jet fuel availability.

Momenthy, A. M.↗
NASA NTRS1980

Atomization of broad specification aircraft fuels

The atomization properties of liquid fuels for the potential use in aircraft gas turbine engines are discussed. The significance of these properties are addressed with respect to the ignition and subsequent combustion behavior of the fuel spray/air mixture. It is shown that the fuel properties which affect the atomization behavior (viscosity, surface tension, and density) are less favorable for the broad specification fuels as compared to with those for conventional fuels.

Skifstad, J. G.↗
NASA NTRS1980

Preliminary studies of combustor sensitivity to alternative fuels

Combustion problems associated with using alternative fuels ground power and aeropropulsion applications were studied. Rectangular sections designed to simulate large annular combustor test conditions were examined. The effects of using alternative fuels with reduced hydrogen content, increased aromatic content, and a broad variation in fuel property characteristics were also studied. Data of special interest were collected which include: flame radiation characteristics in the various combustor zones; the correponding increase in liner temperature from increased radiant heat flux; the effect of fuel bound nitrogen on oxides of nitrogen (NO sub x) emissions; and the overall total effect of fuel variations on exhaust emissions.

Humenik, F. M.↗
NASA NTRS1980

Combustion behavior of solid fuel ramjets

Nonreacting flowfield characteristics and fundamental fuel properties are considered with respect to their use in estimating the obtainable combustion efficiency for fuels and/or combustor geometries. It is shown that near wall turbulence intensity in nonreacting flow appears to correlate reasonably well with the fuel regression pattern in identical geometries. The HTPB based fuels exhibit solid phase exothermic reactions in contrast to purely endothermic reactions for plexiglas. It is further shown that combustion pressure oscillations appear to be related to physically induced disturbances to the fluctuating shear layers at the fuel grain and aft mixing chamber inlets.

Netzer, D. W.↗
NASA NTRS1981

Aviation turbine fuel properties and their trends

Fuel property values and their trends were studied through a review of a recognized, wide ranging sample population from actual fuel inspection data. A total of 676 fuel samples of Jet A aviation turbine fuel were compiled over an eleven year period. Results indicate that most fuel samples have one to three near-specification properties, the most common being aromatics, smoke point, and freezing point.

Friedman, R.↗
NASA NTRS1981

Small gas-turbine combustor study: Fuel injector evaluation

As part of a continuing effort at the Lewis Research Center to improve performance, emissions, and reliability of turbine machinery, an investigation of fuel injection technique and effect of fuel type on small gas turbine combustors was undertaken. Performance and pollutant emission levels are documented over a range of simulated flight conditions for a reverse flow combustor configuration using simplex pressure-atomizing, spill-flow return, and splash cone airblast injectors. A parametric evaluation of the effect of increased combustor loading with each of the fuel injector types was obtained. Jet A and an experimental referee broad specification fuel were used to determine the effect of fuel type.

Norgren, C. T.↗
NASA NTRS1981

The effects of organosulfur compounds upon the storage stability of Jet A fuel

This study examined the effect of sulfur-containing compounds on the storage stability of Jet A turbine fuel. It was found that alkyl sulfides and disulfides increased the fuel's stability while all thiols and thiophene derivatives tested decreased fuel stability (increased deposit formation) at temperatures and sulfur concentrations selected. Linear Arrhenius plots of sulfur-spiked fuel samples demonstrated that deposit formation decreased with increased slope for all alkyl sulfides, alkyl disulfides, thiols, and thiophene derivatives. A plot of insoluble deposit vs. concentration of added alkyl sulfide produces a negative slope. It appears that the inhibiting mechanism for alkyl sulfides is a result of the compound's reactivity with intermediate soluble precursors to deposit in the fuel. A method of approximating the relative basicity of weak organosulfur bases was developed via measurement of their resonance chemical shifts in proton NMR. Linear plots of log gm. deposit vs. change in chemical shift (shift differences between sulfur bases neat and complexed with I2) were found for alkyl sulfides and alkyl thiols. This suggests the possibility that increased deposit formation is due to base catalysis with these compound classes.

Heneman, F. C.↗
NASA NTRS1981

Small gas-turbine combustor study - Fuel injector evaluation

As part of a continuing effort at the Lewis Research Center to improve performance, emissions, and reliability of turbine machinery, an investigation was undertaken to determine the effect of fuel injection technique and fuel type on similar improvements for small gas-turbine combustors. Performance and pollutant emission levels are documented over a range of simulated flight conditions for a reverse-flow combustor configuration using simplex pressure-atomizing, spill-flow return, and splash cone airblast injectors. A parametric evaluation of the effect of increased combustor loading with each of the fuel injector types was obtained. Jet A and an experimental referee broad specification fuel were used to determine and compare effects of burning different types of fuels in a small experimental gas turbine combustor.

Norgren, C. T.↗
NASA NTRS1981

Autoignition characteristics of aircraft-type fuels

An investigation was conducted of the ignition delay characteristics of five liquid hydrocarbon fuels in air. The test apparatus developed permitted independent variation and control of temperature, pressure, air flow rate, and fuel/air ratio in order that the effects of each parameter could be investigated independently. All of the fuels tested behaved in a predictable manner, that is, ignition delay time decreased as temperature, pressure, and fuel/air ratio increased. The results for the different fuels tested (Jet-A, MP-4, No. 2 diesel, ERBS, and cetane) were directly comparable, since it can be shown that the fuel spray characteristics from the multiple conical tube injector are relatively insensitive to small changes in fuel properties (viscosity, surface tension, and density).

Spadaccini, L. J.↗
NASA NTRS1982

ERBS fuel addendum: Pollution reduction technology program small jet aircraft engines, phase 3

A Model TFE731-2 engine with a low emission, variable geometry combustion system was tested to compare the effects of operating the engine on Commercial Jet-A aviation turbine fuel and experimental referee broad specification (ERBS) fuels. Low power emission levels were essentially identical while the high power NOx emission indexes were approximately 15% lower with the EBRS fuel. The exhaust smoke number was approximately 50% higher with ERBS at the takeoff thrust setting; however, both values were still below the EPA limit of 40 for the Model TFE731 engine. Primary zone liner wall temperature ran an average of 25 K higher with ERBS fuel than with Jet-A. The possible adoption of broadened proprties fuels for gas turbine applications is suggested.

Bruce, T. W.↗
NASA NTRS1982

Develop and test fuel cell powered on-site integrated total energy systems: Phase 3: Full-scale power plant development

The development of a commercially viable and cost-effective phospheric acid fuel cell powered on-site integrated energy system (OS/IES) is described. The fuel cell offers energy efficients in the range of 35-40% of the higher heating value of available fuels in the form of electrical energy. In addition, by utilizing the thermal energy generated for heating, ventilating and air-conditioning (HVAC), a fuel cell OS/IES could provide total energy efficiencies in the neighborhood of 80%. Also, the Engelhard fuel cell OS/IES offers the important incentive of replacing imported oil with domestically produced methanol, including coal-derived methanol.

Source record↗
NASA NTRS1982

Low NO sub x heavy fuel combustor concept program phase 1A gas tests

The emissions performance of a rich lean combustor (developed for liquid fuels) for combustion of simulated coal gases ranging in heating value from 167 to 244 Btu/scf were assessed. The 244 Btu/scf gas is typical of the product gas from an oxygen blown gasifier, while the 167 Btu/scf gas is similar to that from an air blown gasifier. Although meeting NOx goals for the 167 Btu/scf gas, NOx performance of the rich lean combustor did not meet program goals with the 244 Btu/scf gas because of high thermal NOx, similar to levels expected from conventional lean burning combustors. The NOx emissions are attributed to inadequate fuel air mixing in the rich stage resulting from the design of the large central fuel nozzle delivering 71% of the total gas flow. NOx generation from NH3 was significant at ammonia concentrations significantly less tha 0.5%. These levels occur depending on fuel gas cleanup system design, However, NOx yield from ammonia injected into the fuel gas decreased rapidly with increasing ammonia level, and is projected to be less than 10% at NH3 levels of 0.5% or higher.

Cutrone, M. B.↗