Numerical study of the effect of combustion chamber structure on scavenging process in a boosted GDI engine

Abstract

The scavenging process is helpful to suppress the super-knock in a 4-stroke turbocharged gasoline direct injection (GDI) engine because it can strengthen in-cylinder cooling and clear suspending residual particles from previous cycles. This paper investigates the effects of combustion system parameters on scavenging process. The simulation results showed that the piston pit with a shallow depth adjacent to the center of cylinder could intensify the scavenging motion and increase the velocity inside the pit, more residual gas and carbon particles could be therefore cleared. The intake and exhaust valve chamfer angle of 45° was beneficial to the scavenging process because more high-velocity scavenging motion occurred in piston pit and less fresh charge flowed into exhaust port directly. The injector location and ground electrode orientation has little influence on scavenging process because of its tiny volume. Finally, an optimum structural shape of combustion chamber was developed and proposed based on the research results.