Oxygen Diffusion through JP-8 as Related to Thermal Oxidative Coking and Titania-Based Remediation Measures
Thermal oxidative coking in jet engine injector passages leads to costly maintenance procedures as well as a significant decrease in engine efficiency. Research has shown that removing dissolved oxygen from the fuel before it reaches a heated passage can result in 1/70th of the coke buildup in injector passages. However, the concern is that the high pressure, high temperature environment of an engine’s combustion chamber will cause the fuel to re-oxygenate rapidly, negating any positive effects of the de-oxygenating process. In connection with attempting to better understand and find solutions to the re-oxygenation leading to coking problem, the objective of this work was twofold. First, to develop a better understanding of the rates and important factors in the re-oxygenation of common jet fuels (Jet A, JP-8, etc.), where computer models and representative physical tests aided the education of the important parameters. The second focus was then on mitigating the effects of the re-uptake of oxygen. In particular, the possible use of titanium dioxide (titania, TiO2) nano-structures within the injector passage are being studied for their potential anti-coking properties. Titania structures have been shown to render a surface oleophobic (i.e. able to readily shed oils), and, separately, able to photocatalytically decompose coke when exposed to UV irradiation. Theoretically, if the oleophobic and photocatalytic behaviors of titania were combined within a single passage, an injector could be manufactured such that shutting off individual injectors within a large injector array during low power demand periods (i.e. cruise or idle) would not run the risk of coking because there would be limited fuel to re-oxygenate and the small amount of coke build up would be passively removed.
Pourpoint, Purdue University.
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