Numerical investigation on the effects of spark timing and low intake temperature on thermal efficiency and combustion characteristics from an OFC GDI engine fuelled with E40 and E85

Oxy-fuel Combustion (OFC) technology implemented in Spark-Ignition (SI) engines has been a promising solution to reduce Greenhouse Gas (GHG) emissions and achieve carbon neutrality. In this research, a comprehensive numerical investigation has been conducted to explore the effects of spark timing and low intake temperature ( T IN ) on thermal efficiency ( η B ) and combustion characteristics from an OFC Gasoline Direct Injection (GDI) engine fuelled with mid or high-ethanol content blended fuel, E40 (40% ethanol and 60% gasoline in mass) and E85 (85% ethanol and 15% gasoline in mass). The results show that under intake temperature of 298 K, the highest η B for E40 and E85 is each 25.73% at the Crank Angle (CA) of spark timing ( φ ST ) = −50°CA and 26.70% at φ ST = −54°CA, while an inappropriate φ ST is deleterious to thermal efficiency and combustion performance for both E40 and E85. With the decrease of T IN from 288 to 238 K, η B shows a small increment to 25.79% and 26.74% for E40 and E85, respectively. Maximum cylinder pressure ( P M ) and maximum in-cylinder temperature ( T M ) each has a gradual decline. Meantime, the CA of P M ( φ P M ) and the CA where 50% of the total heat released ( φ CA 50 ) exhibit low sensitivity to low T IN , which just have a slight delay. The findings could provide new insights into the implementation of OFC engines fuelled with E40 and E85 under low T IN , contributing to the advancement towards carbon neutrality in the transportation sector.