EFFECTS OF OXYGEN AND ADDITIVES ON THE THERMAL-STABILITY OF JET FUELS

A previously developed flowing single-pass heat-exchanger test rig (Ph oenix rig) has been used to evaluate the effectiveness of various addi tives and the kinetic mechanism of both deposit formation and oxygen c onsumption. The Phoenix rig has been modified to include not just a he ated single tube, but also a cooling test section and both hot and col d filters. The effects of flow conditions, antioxidants, and metal dea ctivator additives on the location and amount of the deposit are discu ssed. In general, antioxidants were effective at reducing the deposits on the hot test section, but almost invariably caused increased plugg ing of cool downstream filters. Downstream plugging of cool filters al so increased with decreased temperatures in the heated section or with increased flow. Tests with both oxygen-saturated and oxygen-depleted fuels have shown that the solubility of oxygen is linearly related to the fraction of oxygen in a sparge gas, and that the amount of deposit is linearly related to the total quantity of dissolved oxygen passed. Finally, in contrast to initial modeling efforts, the consumption of oxygen is shown to be significantly more complex than a simple bimolec ular, pseudo-first-order in oxygen, process. It is found to be much cl oser to pseudo-zero-order in the early stages, decaying to pseudo-firs t-order when the oxygen nears depletion.