Experimental Investigation on the Effects of Injection Strategy on Combustion and Emission in a Heavy-Duty Diesel Engine Fueled with Gasoline

摘要

Gasoline partially premixed combustion shows the potential to achieve clean and high-efficiency combustion. Injection strategies show great influence on in-cylinder air flow and in-cylinder fuel distribution before auto-ignition, which can significantly affect the combustion characteristics and emissions. This study explored the effects of various injection strategies, including port fuel injection (PFI), single direct injection (DIm), double direct injection (DIp+DIm) and port fuel injection coupled with a direct injection (PFI+DIm) on the combustion characteristics and emissions in a modified single cylinder heavy-duty diesel engine fueled with 92# gasoline at low load. The investigation consists of two parts. Firstly, the comparison among PFI, PFI+DIm, and DIp+DIm strategies was conducted at a fixed CA50 to explore the effects of PFI+DIm and DIp+DIm strategies on the thermal efficiency and combustion stability. The results show that the coefficient of variation (COV) of indicated mean effective pressure (IMEP) with PFI+DIm and DIp+DIm strategies is lower than that of PFI strategy. High thermal efficiency can be achieved while still maintaining low NO_x and soot emissions by using PFI+DIm strategy. Injection timings of DIm and DIp have strong effects on concentration stratification. Next, in order to explore the behavior of PFI+DIm and DIp+DIm strategies in improving the controllability of auto-ignition and combustion phasing, DIm timings of PFI+DIm, DIp+DIm and DIm strategies were swept from 9 to MAX°CA BTDC (limited by peak pressure rise rate and in-cylinder pressure). The results show that PFI+DIm and DIp+DIm strategies have significant advantages in controlling CA5 and CA50 over a wide stable operation range.