Published: 2000
Total Pages: 0
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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.