An investigation of the processes during the rapid compression of premixed fuel-air systems

The compression ignition and combustion processes of fuel-air mixtures were investigated analytically using in turn a zero-dimensional single zone model, a quasi-dimensional multi-zone model and a mufti-dimensional CFD computer code (KIVA-3). A detailed chemical kinetic model made up of 137 elementary reaction steps with 32 chemical species and a specially developed "flexible" global kinetic model were employed in the simulation for the oxidation of common gaseous fuels and their mixtures. The cases modeled included an adiabatic constant-volume reactor, a pneumatically driven rapid compression machine, a gas fuelled motored engine and a dual fuel engine with pilot diesel fuel injection.;Effective "flexible" global kinetic reaction data for fuel oxidation were derived while using a fitting procedure of the results of the comprehensive chemical kinetic modeling applied to a single zone system. Such an approach was shown to permit indirectly the effective incorporation of detailed chemical kinetic modeling in the CFD KIVA-3 code.;The compression ignition process of methane-air and hydrogen-oxygen-argon mixtures in a rapid compression machine and the effects of charge non-uniformity on heat transfer and autoignition of methane-air mixtures in a motored engine were examined. Predicted results were validated satisfactorily against a range of corresponding experimental values available. 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.;A generalized heat transfer correlation which was derived from the resulting computed instantaneous unsteady heat transfer rates together with experimentally derived corresponding values can provide an estimate of the overall heat transfer coefficient and its variations during rapid compression and expansion of the gas.;The effects of the addition of the products of electrically dissociated water to a dual-fuel engine operating on methane were investigated analytically using a multizone model with detailed chemical kinetics and the merits of such a procedure were evaluated.