A UNIFIED APPROACH TO THE REDUCED KINETIC MODELING OF ALKANE COMBUSTION

A methodology for the generalized kinetic modelling of the combustion of alkanes is presented. By contrast to previous approaches to kinetic modelling of hydrocarbon oxidation, the reactions incorporated in the present model do not evolve from a specified fuel molecule. They are based directly on the numbers of primary, secondary or tertiary C-H bo nds formed selectively from the molecular structure of a single compon ent fuel, or a mixture of components. The low-temperature oxidation of alkyl radicals, formed from the selective abstraction processes, is t hen represented by the modes of alkylperoxy radical isomerization whic h each type of alkyl radical can undergo. Competitive branching (via d iperoxy species) and propagation reactions (via OH and HO2) are includ ed in the scheme. The transition to the ''high temperature'' mechanism is made in a unified way to avoid a multiplicity of supplementary rea ctions as the complexity of the molecular fuel structure changes. The overall model comprises 41 species in 116 reactions, but this is appli cable to a variety of alkane isomers and their mixtures without qualit ative change. The model is tested against the ignition delays of a ran ge of fuels measured in a rapid compression machine. Comparisons are m ade also with recent shock tube data. The simulation of pressure and t emperature changes in two-stage ignition are demonstrated. Aspects of the kinetic structure of low temperature alkane oxidation are also dis cussed.