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NASA NTRS1984

Fuel property effects on Navy aircraft fuel systems

Problems of ensuring compatibility of Navy aircraft with fuels that may be different than the fuels for which the equipment was designed and qualified are discussed. To avoid expensive requalification of all the engines and airframe fuel systems, methodologies to qualify future fuels by using bench-scale and component testing are being sought. Fuel blends with increasing JP5-type aromatic concentration were seen to produce less volume swell than an equivalent aromatic concentration in the reference fuel. Futhermore, blends with naphthenes, decalin, tetralin, and naphthalenes do not deviate significantly from the correlation line of aromatic blends, Similar results are found with tensile strenth and elongation. Other elastomers, sealants, and adhesives are also being tested.

Moses, C. A.↗

NASA NTRS2013

Thermal Stability Results of a Fischer-Tropsch Fuel With Various Blends of Aromatic Solution

Fischer-Tropsch (F-T) jet fuel composition differs from petroleum-based, conventional commercial jet fuel because of differences in feedstock and production methodology. F-T fuel typically has a lower aromatic and sulfur content and consists primarily of iso and normal paraffins. The ASTM D3241 specification for Jet Fuel Thermal Oxidation Test (JFTOT) break point testing method was used to test the breakpoint of a baseline commercial grade F-T jet fuel, and various blends of this F-T fuel with an aromatic solution. The goal of this research is to determine the effect of aromatic content on the thermal stability of F-T fuel. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonic Fixed Wing Project. Two different aromatic content fuels from Rentech, as well as these fuels with added aromatic blend were analyzed for thermal stability using the JFTOT method. Preliminary results indicate a reduction in thermal stability occurs upon increasing the aromatic content to 10% by adding an aromatic blend to the neat fuel. These results do not specify a failure based on pressure drop, but only on tube color. It is unclear whether tube color correlates to more deposition on the tube surface or not. Further research is necessary in order to determine if these failures are true failures based on tube color. Research using ellipsometry to determine tube deposit thickness rather than color will be continued in follow-up of this study.

Lindsey, Jennifer↗

NASA NTRS1984

Aviation-fuel property effects on combustion

The fuel chemical property influence on a gas turbine combustor was studied using 25 test fuels. Fuel physical properties were de-emphasized by using fuel injectors which produce highly-atomized, and hence rapidly vaporizing sprays. A substantial fuel spray characterization effort was conducted to allow selection of nozzles which assured that such sprays were achieved for all fuels. The fuels were specified to cover the following wide ranges of chemical properties: hydrogen, 9.1 to 15 (wt) pct; total aromatics, 0 to 100 (vol) pct; and naphthalene, 0 to 30 (vol) pct. standard fuels (e.g., Jet A, JP4), speciality products (e.g., decalin, xylene tower bottoms) and special fuel blends were included. The latter group included six, 4-component blends prepared to achieve parametric variations in fuel hydrogen, total aromatics and naphthalene contents. The principle influences of fuel chemical properties on the combustor behavior were reflected by the radiation, liner temperature, and exhaust smoke number (or equivalently, soot number density) data. Test results indicated that naphthalene content strongly influenced the radiative heat load while parametric variations in total aromatics did not.

Rosfjord, T. J.↗

NASA NTRS1984

Influence of fuel chemical properties on gas turbine combustors

In an attempt to rigorously study the fuel chemical property influence, UTRC (United Technologies Research Center) (under contract to NASA Lewis Research Center) has conducted an experimental program using 25 test fuels. The burner was a 12.7 cm dia cylindrical device consisting of six sheet metal louvers. A single pressure atomizing injector and air swirler were centrally mounted with the conical dome. Fuel physical properties were de-emphasized by using fuel injectors which produced highly atomized, and hence rapidly vaporizing sprays. A substantial fuel spray characterization effort was conducted to allow selection of nozzles which assured that such sprays were achieved for all fuels. The fuels were specified to cover the following wide ranges of chemical properties: hydrogen, 9.1 to 15 (wt) pct; total aromatics, 0 to 100 (vol) pct; and naphthalene, 0 to 30 (vol) pct. They included standard fuel (e.g., Jet A, JP4), specialty products (e.g., decalin, xylene tower bottoms) and special fuel blends. Included in this latter group were six, 4-component blends prepared to achieve parametric variations in fuel hydrogen, total aromatics and naphthalene contents.

Rosfjord, T. J.↗

NASA NTRS2009

Biofuels as an Alternative Energy Source for Aviation-A Survey

The use of biofuels has been gaining in popularity over the past few years because of their ability to reduce the dependence on fossil fuels. As a renewable energy source, biofuels can be a viable option for sustaining long-term energy needs if they are managed efficiently. We investigate past, present, and possible future biofuel alternatives currently being researched and applied around the world. More specifically, we investigate the use of ethanol, cellulosic ethanol, biodiesel (palm oil, algae, and halophytes), and synthetic fuel blends that can potentially be used as fuels for aviation and nonaerospace applications. We also investigate the processing of biomass via gasification, hydrolysis, and anaerobic digestion as a way to extract fuel oil from alternative biofuels sources.

McDowellBomani, Bilal M.↗

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 NTRS1983

Investigation of sources, properties and preparation of distillate test fuels

Distillate test fuel blends were generated for prescribed variations in composition and physical properties. Fuels covering a wide range in properties and composition which would provide a matrix of fuels for possible use in future combustion research programs were identified. Except for tetralin the blending components were all from typical refinery streams. Property variation blends span a boiling range within 150 C to 335 C, freezing point -23 C to -43 C, aromatic content 20 to 50 volume percent, hydrogen content 11.8 to 14.2 mass percent, viscosity 4 and 11 cSt (-20 C), and naphthalenes 8 and 16 volume percent. Composition variation blends were made with two base stocks, one paraffinic and the other napthenic. To each base stock was added each of three aromatic type fuels (alkyl benzenes, tetralin, and naphthalenes) for assigned initial boiling point, final boiling point, and hydrogen content. The hydrogen content was 13.5 mass percent for the paraffinic base stock blends and 12.5 mass percent and 11.5 mass percent for the naphthenic base stock blends. Sample 5-gallon quantities of all blends were prepared and analyzed.

Bowden, J. N.↗

NASA NTRS2011

Thermal Stability Testing of Fischer-Tropsch Fuel and Various Blends with Jet A, as Well as Aromatic Blend Additives

Klettlinger, J.↗

NASA NTRS2010

Thermal Stability Testing of a Fischer-Tropsch Fuel and Various Blends with Jet A

Klettlinger, Jennifer Suder↗

NASA NTRS2007

A Step Towards CO2-Neutral Aviation

An approximation method for evaluation of the caloric equations used in combustion chemistry simulations is described. The method is applied to generate the equations of specific heat, static enthalpy, and Gibb's free energy for fuel mixtures of interest to gas turbine engine manufacturers. Liquid-phase fuel properties are also derived. The fuels include JP-8, synthetic fuel, and two fuel blends consisting of a mixture of JP-8 and synthetic fuel. The complete set of fuel property equations for both phases are implemented into a computational fluid dynamics (CFD) flow solver database, and multi-phase, reacting flow simulations of a well-tested liquid-fueled combustor are performed. The simulations are a first step in understanding combustion system performance and operational issues when using alternate fuels, at practical engine operating conditions.

Brankovic, Andreja↗

NASA NTRS1947

Minimum Specific Fuel Consumption of a Liquid-Cooled Multicylinder Aircraft Engine as Affected by Compression Ratio and Engine Operating Conditions

An investigation was conducted on a 12-cylinder V-type liquid-cooled aircraft engine of 1710-cubic-inch displacement to determine the minimum specific fuel consumption at constant cruising engine speed and compression ratios of 6.65, 7.93, and 9.68. At each compression ratio, the effect.of the following variables was investigated at manifold pressures of 28, 34, 40, and 50 inches of mercury absolute: temperature of the inlet-air to the auxiliary-stage supercharger, fuel-air ratio, and spark advance. Standard sea-level atmospheric pressure was maintained at the auxiliary-stage supercharger inlet and the exhaust pressure was atmospheric. Advancing the spark timing from 34 deg and 28 deg B.T.C. (exhaust and intake, respectively) to 42 deg and 36 deg B.T.C. at a compression ratio of 6.65 resulted in a decrease of approximately 3 percent in brake specific fuel consumption. Further decreases in brake specific fuel consumption of 10.5 to 14.1 percent (depending on power level) were observed as the compression ratio was increased from 6.65 to 9.68, maintaining at each compression ratio the spark advance required for maximum torque at a fuel-air ratio of 0.06. This increase in compression ratio with a power output of 0.585 horsepower per cubic inch required a change from . a fuel- lend of 6-percent triptane with 94-percent 68--R fuel at a compression ratio of 6.65 to a fuel blend of 58-percent, triptane with 42-percent 28-R fuel at a compression ratio of 9.68 to provide for knock-free engine operation. As an aid in the evaluation of engine mechanical endurance, peak cylinder pressures were measured on a single-cylinder engine at several operating conditions. Peak cylinder pressures of 1900 pounds per square inch can be expected at a compression ratio of 9.68 and an indicated mean effective pressure of 320 pounds per square inch. The engine durability was considerably reduced at these conditions.

Brun, Rinaldo J.↗

NASA NTRS1984

Utilization of alternative fuels in diesel engines

Performance and emission data are collected for various candidate alternate fuels and compare these data to that for a certified petroleum based number two Diesel fuel oil. Results for methanol, ethanol, four vegetable oils, two shale derived oils, and two coal derived oils are reported. Alcohol fumigation does not appear to be a practical method for utilizing low combustion quality fuels in a Diesel engine. Alcohol fumigation enhances the bioactivity of the emitted exhaust particles. While it is possible to inject many synthetic fuels using the engine stock injection system, wholly acceptable performance is only obtained from a fuel whose specifications closely approach those of a finished petroleum based Diesel oil. This is illustrated by the contrast between the poor performance of the unupgraded coal derived fuel blends and the very good performance of the fully refined shale derived fuel.

Lestz, S. A.↗

NASA NTRS1980

Fuel character effects on the J79 and F101 engine combustion systems

The effects of select fuel property variations on two major engine classifications are summarized. Thirteen refined and blended fuels were used which exhibited significant variations in hydrogen content, aromatic type, initial boiling point, final boiling point, and viscosity. Trends were very similar but the degree of fuel sensitivity was not constant. For both systems the dominant fuel property during high pressure operation was found to be fuel hydrogen content. For operation at low pressure test points the fuel volatility and viscosity became the dominant fuel properties for both systems. Aromatic type and final boiling point did not significantly affect combustion data. Correlations of other fuel properties with these and other performance parameters are presented.

Jackson, T. A.↗

NASA NTRS1949

Altitude Performance of AN-F-58 Fuels in British Rolls-Royce Nene Single Combustor

An investigation was conducted with a single combustor from a British Rolls-Royce Nene turbojet engine to determine the altitude performance characteristics of AN-F-58 fuels. Three fuel blends conforming to AN-F-58 specifications were prepared in order to determine the influence of fuel boiling temperatures and aromatic content on combustion efficiencies and altitude operational limits. The performance of the three AN-F-58 fuels was compared in the range of altitudes from sea level to 65,000 feet, engine speeds from 40- to 100- percent normal rated, and flight Mach numbers of 0.0 and 0.6. Similar information was obtained for AN-F-32 fuel at a flight Mach number of 0.0

Cook, William P.↗

NASA NTRS1951

Ignition-delay Characteristics in Modified Open-cup Apparatus of Several Fuels with Nitric Acid Oxidants Within Temperature Range 70 to 105 Degrees F

Fluid properties and low-temperature ignition delays were obtained for approximately 90 fuel-oxidant combinations. A red fuming nitric acid containing approximately 3 percent water and 19 percent nitrogen tetroxide froze at approximately -87 degrees F and ignited several low-viscosity fuel blends of aromatic amines in triethylamine at -76 degrees F and lower. With this acid, the following average ignition delays were obtained with a blend of 30 percent o-toluidine in triethylamine: ...

FUEL SYSTEMS - ENGINES, ROCKET↗

NASA NTRS1946

Flight Investigation of the Knock-Limited Performance of a Triptane Blend, a Toluene Blend, and 28-R Fuel in an R-1830-75 Engine

Knock-limited performance data were obtained for three fuels on an R-1830-75 engine in a B-24D airplane at engine speeds of 1800, 2250, and 2600 rpm, a spark advance of 25 degrees B.T.C., and carburetor-air temperatures of 85 F for 1800 and 2250 rpm and 100 F for 2600 rpm. The test fuels were a blend of 80 percent 28-R plus 20 percent triptane (leaded to 4.5 ml TEL/gal), a blend of 80 percent 28-R plus 15 percent toluene (leaded to 4.5 ml TEL / gal), and 28-R fuel. The knock-limited manifold pressure of the toluene blend depreciated more in the lean region than the triptane blend or 28-R fuel. The knock-limited brake horsepower for the triptane blend varied from 16 to 25 percent higher than 28-R in the lean region and 18 to 30 percent higher in the rich region. The knock-limited brake horsepower of the toluene blend was approximately 15 percent higher than that of 28-R in the rich region and varied from 2 to 10 percent higher in the lean region. Knock limits of the triptane blend and 28-R fuel tested in the R-1830-75 engine agreed with limits for the same fuels determined with the R-1830-94 engine for engine speeds of 1800 and 2250 rpm.

Blackman, Calvin C.↗

NASA NTRS2000

Thermophysics Characterization of Kerosene Combustion

A one-formula surrogate fuel formulation and its quasi-global combustion kinetics model are developed to support the design of injectors and thrust chambers of kerosene-fueled rocket engines. This surrogate fuel model depicts a fuel blend that properly represents the general physical and chemical properties of kerosene. The accompanying gaseous-phase thermodynamics of the surrogate fuel is anchored with the heat of formation of kerosene and verified by comparing a series of one-dimensional rocket thrust chamber calculations. The quasi-global combustion kinetics model consists of several global steps for parent fuel decomposition, soot formation, and soot oxidation, and a detailed wet-CO mechanism. The final thermophysics formulations are incorporated with a computational fluid dynamics model for prediction of the combustor efficiency of an uni-element, tri-propellant combustor and the radiation of a kerosene-fueled thruster plume. The model predictions agreed reasonably well with those of the tests.

Wang, Ten-See↗

NASA NTRS2001

Thermophysics Characterization of Kerosene Combustion

A one-formula surrogate fuel formulation and its quasi-global combustion kinetics model are developed to support the design of injectors and thrust chambers of kerosene-fueled rocket engines. This surrogate fuel model depicts a fuel blend that properly represents the general physical and chemical properties of kerosene. The accompanying gaseous-phase thermodynamics of the surrogate fuel is anchored with the heat of formation of kerosene and verified by comparing a series of one-dimensional rocket thrust chamber calculations. The quasi-global combustion kinetics model consists of several global steps for parent fuel decomposition, soot formation, and soot oxidation and a detailed wet-CO mechanism to complete the combustion process. The final thermophysics formulations are incorporated with a computational fluid dynamics model for prediction of the combustion efficiency of an unielement, tripropellant combustor and the radiation of a kerosene-fueled thruster plume. The model predictions agreed reasonably well with those of the tests.

Wang, Ten-See↗