Detailed thermokinetic modelling of alkane autoignition as a tool for the optimization of performance of internal combustion engines

The purpose of this paper is to show how detailed chemical models of combustion processes may be applied to the optimal design of internal combustion engines. Despite the complexity of the low-, intermediate- and high-temperature oxidation mechanisms of hydrocarbon fuels, there is a sufficiently quantitative understanding of the elementary reaction steps involved, and satisfactory kinetic schemes are available, especially for alkanes. Typical non-isothermal phenomena such as cool flames and the oscillatory behaviour can be properly predicted, and these are the basis for validation of the models. The kinetic model for alkane combustion as described and its performance tested against experiments performed in closed vessels, well-stirred flow reactors and rapid compression machines. Reaction of a fuel + air mixture at the high pressures and temperatures achieved in the cylinder of a reciprocating engine is then studied in an idealized way by considering the combustion chamber to be represented by a perfectly stirred reactor with changing volume. The results of the predicted autoignition are compared with experimental results obtained in a motored engine. These comparisons show that knowledge of the detailed chemistry of oxidation may be used not only for exploring engine design, but also for the new formulation of fuels and the proper understanding of the effect of gasoline additives and their effect on pollutant formation. (C) 1998 Elsevier Science Ltd