Real-time oxidation and coking behavior of ester aviation lubricating oil in aircraft engines

Herein, the real-time structural composition, physicochemical properties and oxidation behavior of ester aviation lubricating oil (ALO) in a complete oil change cycle is investigated deeply based on a certain in-service aeroengine. Theoretical calculations and gas chromatograph-mass spectrometer results reveal that the ester group (109.54 kcal mol-1), C-O bond (109.55 kcal mol-1) and C-C bond (123.38 kcal mol-1) between α-C and β-C in 1-decanoyl-3-nonanoyl-propyl-2-dodecanoate (base oil of ester ALO) breaks orderly at high temperature due to their lower bond energy. The further oxidation, cyclization, esterification and polymerization occurs among the formed intermediates and forms coking precursor via unsaturated double ester, unsaturated single ester and ternary ester. Based on these results, a possible oxidation and coking mechanism of 4050 ALO is proposed.