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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.
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.
For technical readers in the aviation and fuel industries, and in testing laboratories, explores the history and philosophy of the thermal stability of aviation fuel, and considerations during the fuel's manufacture, storage and transport, use, and assessment. The 13 papers, representing a number of
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.
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.
An initiative led by the US Air Force concluded that advances in military fighter aircraft systems would require fuels with over 50% improvement in heat sink capability over conventional JP8 fuel, This led to the creation of the "JP8 + 100" program during which hundreds of commercial additives were tested for thermal stability enhancing characteristics. The program demonstrated that the thermal stability of jet fuels (particularly JPS) could be enhanced through the use of particular additives and additive blends used at relatively low concentrations. Additionally, flight testing highlighted a significant reduction in fuel- and related maintenance costs, arising from cleaner combustion. One aspect of the incorporation of the most beneficial additives from a thermal stability viewpoint that has given some cause for concern, however, is the consequent effect on the water and solids separation from "JP8+100" fuel, a feature minimized by introduction of the "+100" additive as close to the skin of the aircraft as possible. Inspired by the USAF success, and anticipated consequential environmental benefits, we have conducted an experimental program for the design and development of a conceptually new multifunctional molecular species to enhance the thermal stability of jet fuels, without compromising other required essentials of jet a fuel product quality.
Current and planned gas turbine engines use fuel as their primary heat sink. When jet fuel is thermally stressed it will form gums and deposits. These deposits can block engine fuel nozzles, causing damage to the engine hot sections, especially the combustor region. The fuel.s thermal stability is a critical fuel property with respect to optimum performance of modern military gas turbine engines. The current standard method to rate fuel thermal stability, the Jet Fuel Thermal Oxidation Tester (JFTOT), is a subjective, pass-fail type test and is not adequate as a tool to quantitatively investigate fuel thermal stability. This report describes a program to design, construct and commission a rig capable of quantifying fuel.s thermal stability based on carbon and sulphur deposit formation in a heated metal test tube. A fuel known to be unstable both chemically and thermally, sourced from RAAF Townsville, was used as a test fuel for commissioning the rig. The rig was found capable of discriminating between differing test conditions and was successful in rating fuels. thermal stabilities based on quantification of the fuels. deposit-forming capacities. A significant finding of commissioning procedures was the high levels of sulphur deposit formed in the test fuel.