Experimental study on combustion and emission characteristics of diesel engine with high supercharged condition

The effect of diesel engine continuous strengthening on combustion and emission remains to be clarified. This study tested combustion and emission processes at different intake pressures on a single-cylinder diesel engine. The results show that the combustion of diesel engine after continuous strengthening is concentrated in diffusion and post-combustion periods, the overall heat release slows down, and the power increment decreases gradually. When the intake pressure increases to 0.25 MPa, the premixed heat release peak almost disappears, while the value of diffusion combustion period increases significantly. Meanwhile, the gravity center of combustion moves backward and the cumulative heat release rate decreases. The power increases by 95% as the intake pressure increases from 0.15 MPa to 0.25 MPa, but only 44% as it further increases to 0.36 MPa. Meanwhile, the exhaust temperature increases after high supercharging. The above effects are more prominent at high excess air coefficient and low speed. Moreover, with the decrease of excess air coefficient, the proportion of heat release in the post-combustion stage to the whole combustion increases and the power increment is limited. However, the thermal efficiency decreases approximately linearly and the fuel consumption rate increases sharply. In addition, as the excess air coefficient decreases, the exhaust temperature increases, PM increases and NO_x decreases. The above effects are more pronounced at higher boost ratio.