Progress in the Development of a Kinetic Database for Heptane Combustion
This paper deals with the development of a chemical kinetic database for use in the simulation of heptane combustion. The database consists of the thermodynamic properties of all reactants, intermediates and products and the consequences, in terms of rate constants, of their interactions with each other and the oxidant. These elements represent fundamental molecular properties and are not adjustable parameters. Heptane is a liquid under ambient conditions and can be considered to be prototypical of liquid fuels. Linear alkanes are generally the largest component of liquid fuels . The reactions of concern with heptane as a fuel can be expected to be of a subset of the reactions of longer alkanes. In terms of a combustion database our interest is not only in the oxidation processes, for which there has been considerable experimental and simulation work [2-4], but also in the pyrolysis processes that lead ultimately to soot formation. The focus of the work is on the unimolecular decomposition and isomerization reactions of heptane, heptyl radicals, product olefins and the olfinic radicals. The intention is to enumerate and give recommendations on the rate expressions that lead to the formation of the smaller unsaturates that arethe inputs to existing PAH/soot formation models [5,6,]. It will also more properly define the relative importance of cracking and oxidation processes in combustion models. The emphasis on unimolecular reactions is because these are the reactions that actually reduce the size of the fuel. They have generally been neglected in oxidation models. Many bimolecular processes shuffle atoms from one molecule to another. Bimolecular rate constants for the reactons of smaller compounds can be found in existing data bases are easily carried over to the larger species.
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