Isamu Hotta

A Study of a DISI Engine with a Centrally Located High-pressure Fuel Injector

Vehicle manufacturers developed two mixture formation concepts for the first generation of gasoline direct-injection (GDI) engines. Both the wall-guided concept with reverse tumble air motion or swirl air motion and the air-guided concept with tumble air motion have the fuel injector located at the side of the combustion chamber between the two intake ports. This paper proposes a new GDI concept. It has the fuel injector located at almost the center of the combustion chamber and with the spark plug positioned nearby. An oval bowl is provided in the piston crown. The fuel spray is injected at high fuel pressures of up to 100 MPa. The spray creates strong air motion in the combustion chamber and reaches the piston bowl. The wall of the piston bowl changes the direction of the spray and air motion producing an upward flow. The spray and air flow rise and reach the spark plug. The fuel injection pressure, the spray shape and the piston bowl geometry are important factors for the performance of stratified combustion with this concept.