Ignition and Flame Propagation Modeling with an Improved Propane Oxidation Mechanism

An improved chemical mechanism for the combustion of propane has been developed which describes experimental results for a broad range of ignition and combustion phenomena. Simulations of shock tube induction times, measurements of chemical component concentrations in flow reactor experiments, flame speeds, and flame compositions have been carried out with a reasonable degree of success. The rate-determining reactions for some of the experimental simulations have been determined with "brute force" sensitivity analysis Minimum ignition energies were also calculated for spherical ignitions where the ignition energy was added in the form of internal energy which served only to increase the temperature of the gas (heat). The calculated minimum ignition energy gave reasonable agreement with the experimental value for near-stoichiometric mixtures. The H = 0 2 = OH + O reaction was shown to play a dominant role in determining the minimum ignition energy. This paper also attempts to correct errors which appeared in the previous methane-air mechanism (Sloanc, 1989) Previous ignition experiments have shown that for methane-air mixtures the equivalence ratio yielding the lowest minimum ignition energy is leaner than for propane-air mixtures. Modeling studies by others employing a one-step chemical mechanism have suggested that this is due to the different diffusivities of the two fuels relative to oxygen. That explanation was determined in this work to also hold when a detailed chemical kinetics mechanism was used in the model.