Abstract: The influence of four typical injection rate-shapes on direct injection highly-intensified diesel engine combustion process is studied by using three-dimensional CFD software. Through the analysis of ignition delay, heat release rate shape, ratio of premixed combustion and diffusion combustion heat release, the gravity of the combustion process, it shows that: the ignition delay of rectangular injection rate is the shortest, and it gets fired first. The ignition delay of slope-shaped injection rate is the longest. Heat release accounts of the premixed combustion stage of rectangular and trapezoidal injection rate have a larger proportion, and the gravity of combustion process is closer to the top dead center (TDC), combustion capacity is higher, thermal efficiency is higher. Heat release accounts of slope and wedge-shaped premixed combustion stage takes relatively small proportion.

Key words: power mechanical engineering, diesel engine, numerical simulation, fuel injection rate-shape, heat release rate