Fuels Combustion Research: Supercritical Fuel Pyrolysis
Final rept. 1 Dec 1997-30 Nov 1999
PRINCETON UNIV NJ DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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Present and anticipated variation in jet propulsion fuels due to advanced engine compression ratios and airframe cooling requirements necessitate greater understanding of chemical phenomena associated with the feed system and combustion aspects of the airbreathing propulsion systems under consideration by the U.S. Air Force. With AFOSR support an integrated, fundamental research program had been established at Princeton. The focus during the subject period was directed to understanding the pyrolysis and combustion of endothermic fuels under subcritical conditions and the pyrolysis of these fuels under supercritical conditions. Main consideration was given to methylcyclohexane, decalin and tetralin, which are not only endothermic fuels, but alkylcyclohydrocarbons, the naphthene components of JP fuels. The subcritical conditions in the study were 0.1 MPa 1 atm and temperatures ranging between 900-1200 K. The supercritical conditions were between 4-9 MPa 40-90 1 atm and 720-820 K. The Princeton Turbulent Flow Reactor was used for the subcritical studies and a newly designed coiled tubular reactor for the supercritical studies. Substantial experimentation and analytical evaluation revealed distinct differences between the subcritical and supercritical results. From the rate of fuel decay under the conditions described, it was determined that, although the activation energies were of the same order, the supercritical 4.5 MPa preexponential factor A was two orders of magnitude greater than the subcritical 0.1 MPa one. Further, not only were complete scission products of all these fuels found for both cases, but, interestingly, cyclo-intermediates were found under supercritical conditions as well. As the supercritical pressure was increased, the ration of cyclo-intermediates to scission products increased.
- Combustion and Ignition