Computational study on the charge mixing of internal exhaust gas recirculation initiated controlled auto ignition

Controlled Auto Ignition (CAI) uses compression heat to auto ignite a homogeneous air/fuel mixture. Using internal exhaust gas re-circulation (IEGR) as an indirect control method, CAI offers potentially superior fuel economy and pollutant emission reductions. The local chemical and thermal conditions of the engine charge towards the end of the compression stroke have significant influences toward fuel auto ignition performance. In this study, KIVA-3V has been employed to investigate the mixing process involving the fuel, air and the IEGR inside a pentroof engine. The calculated results were compared with experimental data. A mixing index was formulated to show the level of homogeneity in the mixture during the compression process. Good correlations were obtained between the measured and calculated data. Results showed that the level of mixing between trapped burnt gas and the fresh mixture is enhanced by increasing the percentage of trapped IEGR.