Coordination of fuel reactivity and injection timing to achieve highly efficient and stable gasoline compression ignition combustion in a wide load range

Gasoline compression ignition combustion is a new combustion mode with great development potential and is highly influenced by fuel reactivity and injection strategy. This paper coordinates the fuel octane number and single-injection timing to operate gasoline compression ignition combustion with high efficiency in a wide load range, with the speed fixed at 1500 r/min. The primary reference fuels with octane numbers 60, 70, 80, and 90 were used, labeled as PRF60, PRF70, PRF80, and PRF90, respectively. The results proved that under steady-state conditions where the speed and load changed slightly, taking the fuel economy and combustion and emission performance into account, PRF60 and PRF70 should be applied at a load lower than 2 bar and 2–8 bar, respectively, and the start of injection timing should be set at 13 °CA before top dead center. When the load is higher than 8 bar, PRF90 should be applied at the start of injection timing of 11 °CA before top dead center. It is noteworthy that PRF70 under medium-load conditions could achieve the indicated thermal efficiency of up to 47%. The injection timing of PRF90 was limited to 9–1711 °CA before top dead center due to the limit of the peak value of pressure rise rate, whereas PRF60 had a wider injection timing boundary than PRF90.