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The effects of charge non-uniformity on autoignition of methane/air mixtures in a motored engine are investigated analytically using a varying global kinetic data model derived from the results of a detailed chemical kinetic scheme under similar conditions in a simple adiabatic constant volume reactor. These derived varying global kinetic data model was implemented in the CFD KIVA-3 code. The relative contribution of fluid motion generated by piston motion, heat transfer, chemical reactivity of the cylinder charge and swirl movement to the inhomogeneities in the properties of the cylinder charge and their consequent effects on the evolution of the autoignition process are presented and discussed.

The paper examines the rapid compression process of methane-air mixtures while using a zero-dimensional simulation and a detailed chemical kinetic scheme involving 137 reaction steps for methane-air combustion with an account made for heat transfer. The results of this simulation are compared with the corresponding values obtained when using multi-dimensional CFD simulation of the temporal and spatial evolution of the physical properties inside the cylinder while using KIVA-3 code both for reactive and non-reactive “methane”-air mixtures. The reaction rate data used in the code were overall rates of varyingly fitted data based on results of the full detailed kinetic scheme under the same local conditions. The effects of the non-uniformity in the charge physical properties due to heat transfer and compression effects on the evolution of the chemical processes leading to autoignition are presented and discussed.