Calculations of in-cylinder flow of a controlled auto-ignition (CAI) engine

摘要

After validation of the numerical model against published laser doppler anemometry (LDA) experimental data (Pitcher et al., 2003), numerical calculations have been carried out to investigate the in-cylinder transient flow structure of a controlled auto-ignition (CAI) engine running at speeds of 1,500 rpm and 2,000 rpm. The geometry configuration of the engine is imported into the computational fluid dynamics (CFD) code used in this study. The simulations take into account the movement of the inlet, exhaust valves and the piston. To simulate an engine in controlled auto-ignition (CAI) mode, the same valve timing that allows 36% gas residuals was applied to the model. The evolution of the flow pattern inside the cylinder at the symmetrical cross section is described. Also, the turbulence intensity (TI), the turbulent kinetic energy (TKE) and turbulent dissipation rate (TDR) are described for a better understanding of the effect of engine speed on the turbulences generated. The effects of engine speed on fresh charge velocity are also revealed.