Comprehensive assessment of the effects of Ethanol Direct Injection (EDI) mass ratio on the combustion, thermal efficiency and emission characteristics in a Dual-Fuel Spark Ignition (DFSI) engine under low load

There has been a growing focus on Dual-Fuel Spark Ignition (DFSI) engines to reduce harmful vehicle exhaust emissions in industry and academia. In this research, the effects of Ethanol Direct Injection (EDI) mass ratio (δEDI) on the combustion, thermal efficiency and emissions characteristics were comprehensively explored and assessed in a DFSI engine with Gasoline Port Injection (GPI) plus EDI system. The experimental results show that increasing δEDI from 0 % to 100 %, the reduction of ignition delay, maximum in-cylinder temperature and exhaust gas temperature can be up to 2.44°, 263.87 K and 20 K, respectively. Moreover, thermal efficiency and emissions characteristics are very sensitive to the change of δEDI. Compared to the condition of δEDI = 0 %, there is a marked reduction of 41.76 g/kWh in equivalent brake specific fuel consumption under δEDI = 100 %. As δEDI increases from 0 % to 100 %, the maximum reduction in brake specific emissions of Carbon monoxide (CO), Hydrocarbon (HC) and Nitrogen Oxides (NOX) can be 18.46 %, 67.74 % and 39.29 %, respectively. Meantime, a significant decrease of about 99 % can be achieved for the particulate number. Regarding the size distribution of particulate number, the form of the curve transitions from bimodal to unimodal when the δEDI reaches 25 % or more. In summary, the findings presented in this research would provide valuable information on EDI strategy optimisation, primarily benefiting thermal efficiency and emissions mitigation in advanced DFSI engines.