Numerical Simulation and Experiment of the Flow Field, Mixture Formation and Combustion Process in the Cylinder of a Turbocharged Direct Injection Gasoline Engine

Using the 3D engine model a tumble control valve was installed in the intake port to provide a means for controlling the engine airflow motion. Based on a CFD software, the evolution and development of the cylinder flow field with the change of crank angle were calculated, the tumble motion and turbulent kinetic energy were assessed, the spray atomization process and mixture concentration distribution were simulated under the condition of equivalent air/fuel ratio, and the combustion process was analyzed. Results show that use of tumble control valve can effectively improve the cylinder tumble ratio, and enhance the turbulent kinetic energy, allowing to improve the combustion rate and combustion process at the condition of 0.2 MPa at 2000 r/min and full load at 1750 r/min. Moreover, a special design of piston top shape was used to prevent the spray wall impingements. These improvements make the simulated cylinder combustion pressure curves and the actual engine bench test results have a good consistency.