Effect of Charge Non-Homogeneity on Cycle-by-Cycle Variations in Combustion in SI Engines

The influence of charge non-homogeneity on the cycle-by-cycle variations in combustion for a SI engine was studied experimentally and analyzed theoretically. Charge non-homogeneity was determined from the exhaust gas composition. Cycle-by-cycle variations in the maximum combustion pressure and the angle of maximum pressure were determined by using a real time data acquisition system. A linear relationship between charge non-homogeneity and the cyclic variations in maximum pressure was found.

Computed results showed that cyclic variations in maximum combustion pressure increase with increase in charge non-homogeneity at a given mixture strength. For the same charge non-homogeneity, cyclic variations also increase with leaning of the mixture and with increase in the duration of initial phase of combustion.