Demonstrating the Potential of Mixture Distribution Control for Controlled Combustion and Emissions Reduction in Premixed Charge Compression Ignition Engines

The present experiment employs two fuel injectors which are capable of port injection and direct one. The former was used to supply a highly-homogeneous mixture and the latter with late injection timing was employed to control the mixture heterogeneity. Thus, these sets of injection equipments are capable of setting a wide variety of mixture heterogeneity. Furthermore, two primary reference fuels were used in order to know the influences of chemical character. The experiments were conducted in order to clarify the combustion and emissions characteristics through engine tests. Optical diagnostic was also performed to gain additional insight into the combustion processes for a wide variety of mixture distribution.

The results using the port injection showed that the steepness of the combustion was affected by the local equivalence ratio rather than the overall one. The double injection using both injection equipments demonstrated that the ignition source was the mixture formed by the direct injection and there was the optimum mass fraction of direct injection to reduce the maximum pressure rise rate in the case of combination of lower octane number fuel and lower compression ratio. In contrast, the different tendency was observed for the combination of higher octane number fuel and higher compression ratio.