A WIDE-RANGE MODELING STUDY OF PROPANE AND N-BUTANE OXIDATION

Propane and n-Butane are the smaller and simpler hydrocarbons that already show the different behaviours of the combustion process; detailed chemistry and general kinetic mechanisms can unify the complexity of these phenomena by properly taking into account slow combustion, cool flames, negative temperature coefficient, transition temperature and hot ignition processes. Carbonyl-hydroperoxides are the main cause of the negative temperature cofficient (NTC) in the transition region (600-650 K). At intermediate temperatures the equilibrium between alkyl and peroxy radicals shifts towards alkyl radicals and hydrogen peroxide becomes the dominant branching agent. At higher temperatures (T > 1000 K), decomposition reactions of alkyl radicals prevail on the direct oxidation and combustion process mainly proceeds through smaller olefins oxidation. As a consequence, only the low temperature, primary oxidation reactions of propane and butane need to be added to a comprehensive kinetic scheme already available for methane and C-2 species. The overall scheme discussed in this paper is constituted by more than 100 species involved in about 2000 reactions. Furthermore a new method of formalizing this large quantity of mechanistic rate data facilitates the application and the extension of this scheme. Several comparisons with experimental data, obtained over a wide range of temperatures (550-1200 K), pressures and oxygen concentrations, support and validate the proposed kinetic model.