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

Abstract

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 ( ${\phi }_{P_M}$ ) and the CA where 50% of the total heat released ( ${\phi }_{\mathrm{CA}50}$ ) 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.