LOW-TEMPERATURE COMBUSTION - AUTOMATIC-GENERATION OF PRIMARY OXIDATION REACTIONS AND LUMPING PROCEDURES

The aim of this paper is to present some general rules for the automat ic generation of primary oxidation reactions of large hydrocarbon fuel s. The proposed approach is applied to n-paraffins for reason of simpl icity. Nevertheless, the final goal is to feed the tested rules and ki netic parameters into a more general and effective expert system for t he generation of primary mechanisms of real mixtures containing heavie r branched hydrocarbons. The first step is the classification of the p rimary reactions involved in low-temperature oxidation, together with the definition of a limited set of their intrinsic kinetic parameters. These independent rate constants are validated on the basis of primar y experimental measurements of pyrolysis and oxidation. In addition to this, the paper analyzes some useful simplifications for the kinetic modeling of secondary combustion processes. As the carbon number of th e hydrocarbon fuel rises, the detailed reaction schemes become very co mplex. The number of isomers of the same homologous class of molecules and radicals increases and the number of reactions increases simultan eously. In these cases, the automatic generation of the primary oxidat ion reactions and properly conceived lumping procedures, both for reac tions and components, become very useful. These lumped mechanisms of h eavy species consist of a limited number of equivalent reactions. Then , this small subset of equivalent reactions has to be coupled with a v ery detailed scheme for the oxidation of C-1-C-4 species. The final re sult is still a very large number of reactions, which makes it incompa tible with c.f.d. calculations, but whose extension to heavier species becomes easier to handle. A few comparisons of experimental and predi cted results for the low-temperature oxidation of n-butane and n-penta ne illustrate the applicability of this approach.