A study on the combustion strategy of gasoline/diesel dual-fuel engine

In this investigation, a diesel engine is selected as the prototype to deeply study the combustion strategy of gasoline/diesel dual-fuel engine. Based on the research, the combustion mode of premixed gasoline injection at the intake port and direct diesel injection and induced ignition in the cylinder can be realized by increasing the gasoline injection system in intake port. The experiments were conducted based on optimization of gasoline ratio, number of diesel injection (single and double), diesel injection timing, EGR rate under 1800 rpm-70 Nm, 1400 rpm-50 Nm, and 2200 rpm (variable torque). The results show that engine fuel consumption, its exhaust temperature, its NOx, and its soot emission was reduced with the increasing of gasoline ratio, the engine obtains perfect economic and emission performances with 66% of gasoline ratio, fuel consumption is 249 g/kW-h, lower than 254 g/kWth of prototype diesel engine, the values of NOx emission and soot emission are 0.22 g/kWth and 0.0015 g/kW-h respectively; At the 1400 rpm-50 Nm, if a single injection is adopted, fuel consumption is higher more than 280 g/kWth, the maximum pressure rise rate is also higher most above 1 MPa/ CA, therefore, at medium and high load, the twice injection should be considered instead, two times injection can effectively reduce pressure rise rate by retarding first injection timing, while engine load can be increased by adding second injection quantity; At the 1400 rpm-50 Nm, the trade-off relative between NOx and soot emission was solved perfectly by using hot EGR, economic performance was also improved.