Quantitative Analysis of Water Injection Mass and Timing Effects on Oxy-Fuel Combustion Characteristics in a GDI Engine Fuelled with E10

The climate change issue has become a growing concern due to the increasing greenhouse gas emissions. To achieve carbon neutrality for mitigating the climate problem, the oxy-fuel combustion (OFC) technique on internal combustion engines (ICEs) has attracted much attention. Furthermore, the water injection (WI) strategy was proven effective in improving the combustion process and thermal efficiency in engines under OFC mode. However, WI strategy effects on gasoline direct injection (GDI) engines fuelled with gasoline–alcohol blends have not been reported. This study quantitatively analysed WI mass and timing effects on oxy-fuel combustion performance from a GDI engine fuelled with E10 (10% ethanol and 90% gasoline in mass) by simulation. The results show that equivalent brake-specific fuel consumption (BSFCᴇ) shows a monotonically decreasing trend with the increase in the water–fuel mass ratio (Rwf) from 0 to 0.2. However, further increasing Rwf would cause a deterioration in BSFCᴇ due to the enhanced cooling effects of water vaporisation. Moreover, an appropriate water injection timing (tWI) could be explored for improving OFC performance, especially for large Rwf conditions. The difference in BSFCᴇ between tWI = −100°CA and tWI = −60°CA can be up to around 6.3 g/kWh by increasing Rwf to 0.6.