A simulation model of ultra high pressure common rail system with variable fuel injection rate was established by AMESim software

and the characteristics of the fuel injection rate under same injection quantity were analyzed. Using the combustion model of a single cylinder diesel engine built by GT-Power software

the different fuel injection rate was inputted into the engine model to research the effect of different fuel injection rates on cylinder pressure

cylinder temperature

heat release rate

exhaust emissions

torque and fuel consumption. Simulation results show that the comprehensive performance of the engine can be optimized by matching a saddle-shaped injection rate with an appropriate fuel injection timing. At the same time

the injection control experiment with different fuel injection rate was carried out on a test bench. Experimental results show that: compared with the same fuel quantity of high pressure common rail injection

the ultra high pressure fuel injection with variable injection rate can be used for diesel engine to obtain more excellent power performance and fuel economy. This will make the power output increased by 5% and the fuel consumption decreased by 6% with higher NOx emissions and lower soot emissions. The research conclusions can help to explore the fuel injection law

thus improving the engine performance.