Reduced chemistry descriptions for ignition and detonation of higher hydrocarbons

Abstract

Introduction The chemistry of ignition and detonation of higher hydrocarbons and especially propane in oxygen-diluent mixtures is studied for post-shock temperatures between 1000 K and 2500 K, pressures between 1 to 100 bar and equivalence ratios between 0.5 to 2.0. A detailed mechanism that had been previously developed is extended for ignition and detonation by including 26 additional propane-related reactions. The resulting detailed mechanism of 174 reactions and 36 species for propane predicts autoignition times that are in good agreement with data from shock-tube experiments. A short mechanism of 34 reactions is identified by sequentially removing reactions that do not influence the ignition chemistry of propane. Steady-state species are identified for both high and low-temperature conditions. Application of steady-state approximations leads to reduced chemistry descriptions, which describe the distinct stages in the ignition chemistry of propane. These reduced mechanisms form the basis for further simplified descriptions that can be used in computational studies on multidimensional ignition and detonation. Numerical and theoretical studies on detonation of fuels like propane (CaHs) and JP-10 are in need of realistic chemical-kinetic descriptions that retain the essential features of the detailed descriptions. Reduced chemistry descriptions have been previously developed successfully for a number of lower hydrocarbon fuels. Recently the ignition behavior of n-heptane has been studied for high, low and intermediate temperature regimes as well. In the present work, the chemistry of ignition of propane in oxygendiluent mixtures is studied with emphasis on developing systematically reduced mechanisms for use in detonation studies. The overall activation energy and ignition times for propane are similar to those of JP-10, which is a suitable fuel for use in Pulse Detonation Engines. For this reason, propane has been used as a model fuel for several numerical and experimental studies on detonations. In addition, the ignition mechanism for propane is found to be similar to that of other higher hydrocarbons and different from that of the lower hydrocarbons addressed previously. * Current affiliation: GE Corporate Research and Development Center, NY 12309 ^ Corresponding author American Institute of Aeronautics and Astronautics (c)2002 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.