A Numerical Analysis of Methane Direct Injection System for Spark Ignition Engines(CNG and Alternative Fuels, CNG Engines)

Abstract

A numerical study of the spark ignition engine combustion system with direct methane injection to combustion chamber is presented. Poor penetration of gaseous fuel jet and poor mixing with air in the engine cylinder together with very short time available for mixing create serious difficulties in choosing proper injection parameters and in arranging the combustion chamber geometry. The results of preliminary analysis showed that mixing process of methane with air is very complex. Early beginning of injection extends the time available for mixing and strong vortex in combustion chamber makes mixing process more efficient. Direction of injection has also influence on mixing process and thanks to this a larger amount of fuel can be involved in mixing process. When the methane jet breaks up at the surface of combustion chamber wall gaseous fuel penetrates longer distance but mixing is not so efficient and layers with well-stirred mixture are surrounded with non-flammable mixture. The two-dimensional numerical simulations of methane direct injection system were performed with the use of KIVA-3V computer code. The results of calculations allow for optimisation of this system including combustion chamber geometry, location of the spark plug and injector together with the injection and ignition timing. The results of this study create the base for the further numerical investigation of the engine combustion system with methane direct injection, which will be performed together with related experimental research.