In-situ Methods for Study of Fuel Thermal Stability

The development of advanced high speed aircraft using hydrocarbon fuels will require fuels which have very high thermal stability, including fuels which are stable above the critical temperature and pressure. The elucidation of the chemcial mechanisms for fuel degradation would greatly benefit from the availability of on-line diagnostics for measurement of these products. The Phase I proposal is to develop a methodology for in-situ optical measurements of peroxide decomposition products and demonstrate how this information can be used to elucidate the chemical mechanisms of fuel degradation. The fuels would be studied under subcritical and supercritical conditions. The optical methods would include FT-IR and FT-NIR transmission spectroscopy. Experimental variables to be examined would include fuel type,time-temperature history, and the pressure or absence of dissolved oxygen. The Phase I program will demonstrate the capability of these optical diagnostics to make in-situ measurements of oxygenated species known to be involved in fuel degradation. The Phase II program will combine these techniques with previously developed diagnostics for mass deposit rate and composition into an advanced Fuel Stability Test System (FSTS). The FSTS will be used to make measurements for a suite of fuels and establish a database for model development. The final product of Phase II will be the advanced FSTS and a physicochemical model of fuel stability that could be a submodel for an comprehensive code for simulation of deposit formation under actual aircraft conditions.