Gasoline Direct Injection Engines and Particulate Emissions

Gasoline direct injection (GDI) engines are increasingly used in transport sector worldwide in recent years due to the advantages they offer. These include superior fuel economy and better engine response and control due to introduction of electronic control unit (ECU) and high-pressure fuel injection system. One of the main challenges of using GDI engine vehicles is that they emit particulates, which are not an issue in case of multipoint port fuel injection (MPFI) engines. However, there is potential to further improve GDI engines for lower particulate matter (PM) emissions. Particulates from GDI engines are of different sizes such as coarse, fine and ultra-fine, and they also vary in composition and origin. The particulate of different sizes is known to cause adverse health effects. In this chapter, fundamental aspects of both homogeneous and stratified modes of combustion of GDI engines have been discussed, in addition to wall, spray and air-guided GDI engine concepts. A section of the chapter covers detailed comparison of particulate emitted by GDI and MPFI engines. Various size and concentration-based PM measurement techniques and instruments available commercially are included in this chapter. A discussion on influence of engine load, fuel type and spray characteristics on particulate emissions is elaborated towards the end of this chapter in addition to GDI soot morphological studies.