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This paper describes a two-year programme of research conducted by the authors investigating HCCI in direct injection gasoline engines. Poppet-valved two-stroke cycle operation has been investigated experimentally, using conventional gasoline compression ratios and fuel, and ambient temperature intake air. Extensive combustion and emissions data was gathered from the experimental engine. Computational Fluid Dynamics (CFD) has been used to model HCCI combustion, and the CFD tool validated using experimental data. Based on experience with the two-stroke engine and modelling techniques, a four-stroke engine has been designed and tested. Using this range of tools, practical options for gasoline HCCI engines are evaluated, and a scenario for the market introduction of HCCI is presented.

A system for stratifying recycled exhaust gas (EGR) to substantially increase dilution tolerance has been applied to a port injected four-valve gasoline engine. This system, known as Combustion Control through Vortex Stratification (CCVS), has shown greatly improved fuel consumption at a stoichiometric air/fuel ratio. Both burnrate (10-90% burn angle) and HC emissions are almost completely insensitive to EGR up to best economy EGR rate. Cycle to cycle combustion variation is also excellent with a coefficient of variation of IMEP of less than 2% at best economy EGR rate. This paper describes a research programme aimed at gaining a better understanding of the in-cylinder processes in this combustion system.