Effect of Injection Strategy on Quick Start of Gasoline Direct Injection Engine

Abstract:

The research on two stage spray strategy of quick start of one gasoline direct injection（GDI）engine is studied by using the computational fluid dynamics (CFD) method. The result shows that，earlier first injection timing will cause much more oil film on the surface of piston and less fuel evaporation which may lead to dilute mixture in cylinder and the ignition requirements can’t be met. Then later first injection timing may result in more rich mixture being detained in the exhaust valve pit which will lead to more hydrocarbon emissions. The first spray timing should be set from 270° CA BTDC(before top dead center) to 240° CA BTDC. Compared to the first injection, the influence on oil film of second spray timing during compression process is little. The injection timing earlier 90° CA BTDC may cause more crash between droplets and cylinder liner. According to the simulation results, the second injection timing should be set after 90° CA BTDC.

Key words:vehicles; engine; direct injection; quick start; two stage spray; oil film