Book Description

The objective of this work was to develop a methodology for in-situ optical measurements of peroxide decomposition products from aviation fuels and demonstrate how this information could be related to fuel stability. Three fiber optic probes (2 Mid-IR, 1 Near-IR) were designed and constructed, and used to monitor the changes in composition of two fuels (Shell Jet A #2827 and Sun Jet A-1 #2747) after thermal stressing. Both mid-IR probes were found to be very sensitive to changes in fuel composition. The large gap (1 mm) IR cell was used to make in-situ IR transmission measurements for peroxide decomposition products, including carbonyls (free and acid form), alcohols, and CO2 (two forms). These measurements were consistent with the generally accepted free radical mechanism of fuel degradation, including the inverse relationship between oxidative and thermal stability. The data from the small gap (0.1 mm) IR cell were found to be consistent with changes in deposit formation tendencies with temperature for similar fuels reported in the literature. In an option task, an FT-Raman probe was evaluated and found to be much less sensitive than the Mid-IR probes. This disadvantage may be remedied by the use of a surface enhanced probe. The potential applications include an instrument for development and evaluation of thermally stable fuels or supercritical fuels, improved global models of fuel degradation mechanisms, and on-board monitors of fuel thermal stability.