Effect of injection strategies on particulate matter structures of a turbocharged GDI engine

A study on particulate matter (PM) compound of a turbocharged gasoline direct injection (GDI) engine for different injection strategies has been performed. Particularly, morphology and structure of PM and soot pro- duced by GDI engine were investigated as a function of injection rail pressure and start of injection before top dead center (SOI bTDC). The produced particulate matter and soot have been analyzed on a wide range of operating conditions by means of imaging and sampling techniques. To study the relationship between parti- culate morphology and engine working conditions, microscopic analyses (SEM and TEM) of several samples at the exhaust were performed. Therefore, these investigations were coupled with soot measurements before the catalyst and at the exhaust by means of a soot detector, able to measure the carbon component of particulate matter. Besides, the same measurements were compared with smoke opacity analyses to detect also the non- carbon components. The results demonstrated high influence of injection strategies on soot morphology-com- position and on catalyst efficiency, revealing also a wear phenomenon of the piston under high pressure con- dition.