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All three TSIAs reduce the amount of thermal deposits, measured via carbon burnoff, in both laminar and turbulent test units for the three (3) different base fuels tested. For the laminar test unit, Betz 8Q462 shows better deposit inhibition than MDA by a narrow margin. Therefore, MDA shows a ysnergistic effect when added to the Betz 8Q406 (to produce Betz 8Q462) in the laminar unit.
NAVAIRSYSCOM has evaluated the individual benefits of 3 different thermal stability improving additives (TSIAs) in jet fuel using 2 separate, small-scale test devices - one laminar flow and the other turbulent. Both systems pump fuel at constant flowrate and use stainless steel tubes that are heated to maintain the bulk fuel at a constant, elevated test temperature. The laminar device has an inside diameter of 0.1 in. (0.262 cm) and an approximate Reynolds No. of 200, whereas the turbulent has an inside diameter of 0.01 in. (0.0254 cm) and a Reynolds No. of 13,000. The results have shown that all 3 TSIAs, when test at their maximum dose levels, reduce the amount of thermal deposits (measured via carbon burnoff) in both flow regimes for 3 different base fuels tested. Both units rank the level of thermal stability in the same order for the 3 baseline fuels tested. In addition, both devices show that Betz 8Q462. is the most effective additive of the 3 tested, with MDA demonstrating almost similar performance in controlling deposit formation. Furthermore, Betz 8Q406 was not as effective as the 2 other additives, but a change in its formulation by the addition of 2 mg/l MDA (to produce 8Q462) greatly improved its performance in both test devices, but most notably in the laminar unit. However, one exception had occurred when MDA was added to one of the test fuels (Tank 20122), which caused an increase in deposition compared to the neat fuel when tested in the turbulent unit. Overall, the combination of the accelerated test conditions in the turbulent unit of higher bulk fuel temperate, higher flowrate, turbulent flow (i.e., flatter temperature profile across the tub ID), and shorter residence time make this a more severe test when compared to the laminar device.
This report describes the high heat sink fuels thermal stability additive evaluation protocol of test methods as they apply to the evaluation of additives for JP-8+100. Individual test methods are described and a standardized methodology for test operation is presented. Acceptance criteria for both baseline fuels and candidate additives are also given.
Technical effort was directed at increasing the design limit of current JP-8 fuel from 325 deg F (163 deg C) to 425 deg F (218 deg C) at the fuel nozzle. The objective was to accomplish this near-term thermal stability goal solely through the use of a fuel soluble additive package. JP-Thermally stable fuel was considered the thermal stability target since it has the high- temperature properties sought from the significantly more economical JP-8 + 100 formulation. The additives were evaluated in an additive-free Jet A considered typical of fuel most likely to be encountered in the field. DuPont JFA-5, currently the only accepted thermally stability improving additive, was considered state of the art and used as a bench mark. Additive manufacturers were surveyed and solicited for candidate additives that had potential for improving fuel thermal oxidative stability. Test methods were developed and/or refined for use in screening additives. Using the Hot Liquid Process Simulator (HLPS) in conjunction with a LECO Carbon Determinator, 152 additives were screened. Additive performance was ranked based on surface carbon and differential pressure. Additional screening was performed using the Isothermal Corrosion Oxidation Test (ICOT). Additives screened included oxygen, sulfur, and nitrogen-type antioxidants; dispersants; detergents; metal deactivators; antifoulants; and proprietary thermal stability improvers. Twenty-seven experimental blends comprised of various additive combinations were tested. Five baseline fuels were evaluated.
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.
A program to investigate the effect of storage time and temperature on changes in thermal stability quality as measured by the CRC-Modified (SSF) Coker for five widely different fuel types continues to show no significant deterioration of any fuels after 36 weeks at ambient field conditions or 22 weeks at 130 F. After storage at 180 F for 36 days, four of the fuels showed no loss in thermal stability but an HF alkylate fuel containing abour 2% olefins showed a statistically significant loss of about 100 F after storage periods of 6, 18 and 36 days. Removal of dissolved oxygen (to
Two fluorocarbon lubricity additives were tested in the Minex heat exchanger to determine their effect upon the thermal stability of a highly refined jet fuel. The jet fuel without additives and the fuel with a standard metal deactivator additive were tested first to provide a base line for testing with the lubricity additives. The results show that the additive-free jet fuel would not degrade the heat transfer efficiency in a Minex heat exchanger at 680 F. The addition of the metal deactivator N, N' - disalicylidene - 1, 2 - propane diamine, had no effect upon the thermal stability of the fuel but the fluorocarbon lubricity additives would degrade thermal stability. Additive A changed thermal stability from greater than 680 F to 600 F, and Additive B decreased the break point to 650 F. Although there was an adverse effect upon thermal stability, the jet fuel with the fluorocarbon additive is still usable for modern high speed aircraft.