Abstract:

Pollutant emissions for a Gasoline Direct Injection (GDI) engine with double injection at cold start in cylinder process were investigated using a visualization method. The spray and combustion images in an optical single cylinder engine were recorded simultaneously from two directions perpendicular to each other utilizing two high-speed cameras. A combustion analyzer and a micro-soot-sensor were used to analyse combustion stability and soot emission. A CLD500 type fast NOx system and a HFR500 type fast Flame Ionization Detector (FID) system were used to sample nitrogen oxide and hydrocarbon emission. The results show that the main reason for high soot emission caused by impinging more fraction fuel on piston crown and forming oil film under cold start condition using delayed second injection timing. While, advancing second fuel injection improves combustion stability. Increasing first injection fraction decreases the emissions of soot, NOx and HC with a slight negative effect on the combustion stability.

Key words: engines, gasoline direct injection (GDI), cold start, double injection, combustion stability, visualization, pollutant emission