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The ignition delay period in dual fuel engines is examined, while employing the gaseous fuels methane, propane, ethylene and hydrogen. It is shown that the changes due to gaseous fuel admission in the temperature and pressure levels during the delay period, the extent of energy release due to preignition reaction processes, variations in the parameters of external heat transfer to the surroundings and the contribution of residual gases are the most important factors that determine the ignition delay characteristics of dual fuel engines. The consequences of these factors on the observed values of the ignition delay were evaluated while using detailed reaction kinetics for the oxidation of the gaseous fuel and employing an experimentally based formula for the ignition of the liquid pilot.

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.