Investigation of the combustion and particle emission characteristics of a GDI engine with a 50 MPa injection system

Abstract

The effects of injection pressure and injection timing are investigated in a gasoline direct injection engine with a 50 MPa injection system at part-load operating condition by experimental methods. The engine was invariably operated in stoichiometric air/fuel ratio, 1500 r/min engine speed and 5–15 bar break mean effective pressure (BMEP). The characteristics of combustion, particle size distribution (PSD) and particle number (PN) concentration of the emission are analyzed. The results indicate that delaying the injection timing can suppress the knocking tendency at higher engine loads, and significantly reduce fuel consumption, but the delayed injection increases particle emission. With the fuel injection pressure increased from 35 MPa to 50 MPa, the PN of all particle size segments are significantly reduced. High injection pressure has a significant effect on reducing the accumulation particles, and the PN concentration is reduced by more than 20%. The particles with a diameter of 5–23 nm (sub-23 nm) are a problem that cannot be ignored, which accounts for more than 50% of the total PN emission. A high fuel injection pressure can effectively reduce particulate matter emissions caused by late injection, thereby achieving both fuel consumption and particle emission reduction.