A mathematical model for hydrocarbon autoignition at high pressures

Abstract

We have developed a generalized mathematical model for the autoignition of hydrocarbons under the conditions of high pressure and temperature achieved in a rapid-compression machine. The model is able to simulate the essential phenomena of the two-stage autoignition of alkanes under these conditions; these are a well-defined cool flame that is often quenched rapidly and completely before the onset of a sharp ignition. It also pre­dicts correctly the transition to single-stage autoignition at even higher temperatures and the variation with temperature of the characteristic induction periods. The model is based on a degenerate-branched-chain mechanism. We show that it must contain as necessary features two termination processes, one linear and the other quadratic in radial concen­tration, and two routes for the formation of branching agent, one of which involves intermediate products of oxidation. The model also predicts, without any adjustment of the kinetic parameters, the essential pheno­mena of cool-flame and ignition behaviour that are observed at low pressures.