Effects of Piston Shape on the Performance of a Gasoline Direct Injection Engine

Abstract

In this study, two different piston structures (bowl-shaped pit and trapezoidal pit) are constructed; the mixture formation, combustion, and emissions of a gasoline direct injection engine with the two piston types are compared and analyzed by computational fluid dynamics simulation. The results show that piston A (bowl-shaped) can form a combustible mixture near the spark plug at the ignition time and has higher pressure peaks and accumulated heat release than piston B (trapezoidal), which helps improve the combustion efficiency of the internal combustion engine. Furthermore, three pistons with different bowl-shaped pit depths (pistons A1, A2, and A3) are designed based on piston A. The results show that piston A2 (7.7 mm) has advantages in terms of strengthening the turbulence in the cylinders, promoting fuel evaporation, increasing the in-cylinder turbulent kinetic energy and the velocity of the airflow near the spark plug at the ignition time, and accelerating the rapid diffusion of combustion and the rapid increase in in-cylinder temperature and pressure. Also, piston A2 can reduce the CO and soot emissions.