Steady flow test and numerical simulation of a GDI engine

In this paper, steady flow tests for air movement characteristics in cylinder and intake port flow coefficient of a GDI engine were carried out by means of steady flow test bench. Three-dimension numerical simulation model was established with consistent boundary conditions of steady flow tests. Experiment results indicated that tumble was the main air flow of this GDI engine. Intake port flow coefficient measured during tumble tests were lower than that of swirl tests, and as intake valves raised the difference between those two tests was more and more obvious. Simulation results were almost identical with experiment date. The in-cylinder velocity field and pressure field demonstrated that the structure of dummy cylinder in steady flow tests had a great influence on in-cylinder air flow. In tumble tests, air flow in dummy cylinder were turned back to intake valves and a part of intake air were pushed by the turned back flow. A sector of low speed and high back pressure area could be found near by intake valves. Such air flow impact was believed as the reason of such difference on intake port flow coefficient.