Impacts of fuelling methods on knock-limited combustion and emissions of a dedicated hybrid spark-ignition engine

Abstract

This study investigates the impact of various fuelling methods on knock-limited combustion efficiency and emissions in a high compression ratio, turbocharged spark-ignition gasoline engine designed for hybrid applications. Different injection strategies, including port fuel injection (PFI), direct injection (DI), two-stage DI, PFI with late DI, and PFI with in-cylinder targeted fuel injection (TFI), were evaluated. TFI, a novel method where fuel is injected towards knock-prone regions based on knock spatial distribution, was seen capable of advancing the knock-limited spark advance (KLSA) by up to 3.75°, and hence reducing fuel consumption by 18.78 g/kWh, demonstrating significant knock suppression. Furthermore, trade-off characteristics between fuel consumption and particulate emissions resulting from injection strategies were exhibited from the measured data. DI produces the optimal fuel consumption and the worst particulate emissions, while PFI shows the opposite. Importantly, TFI improves the trade-off, reducing fuel consumption and emissions simultaneously. The refined TFI achieved a 96.6 % reduction in particulate emissions compared to DI, matching PFI levels while improving engine thermal efficiency. These different combustion characteristics are attributed to the localized fuel–air mixing and charge cooling affected by injection strategies.