MESOPHASE AND PYROLYTIC CARBON FORMATION IN AIRCRAFT FUEL LINES

Exposure of jet fuel to high temperatures in aircraft fuel lines trigg ers pyrolysis reactions which eventually lead to deposition of carbona ceous solids on metal surfaces. This is a particularly important probl em for advanced future aircraft which may expose fuel to very high tem peratures. Different optical textures were observed in samples of depo sits formed in different sections of aircraft fuel systems. Deposits f rom a burner fuel line consist only of pyrolytic carbon, indicating th at gas phase reactions were responsible for solid formation. Afterburn er line deposits, on the other hand, contain both pyrolytic carbon and carbonaceous mesophase structures, implicating also liquid phase carb onization reactions. The FTIR data shows that solids containing mesoph ase consist of polynuclear aromatic hydrocarbons with a low degree of condensation and alkyl substitution. In contrast, solids with pyrolyti c carbon structure are composed of highly condensed, large polyaromati c species. It is clear that jet fuels go through extensive cracking, a romatization, and aromatic polymerization reactions before solid depos ition takes place in the fuel lines. Copyright (C) 1996 Elsevier Scien ce Ltd