Experimental Investigation on Combustion and Performance of Diesel Engine under High Exhaust Back Pressure

The use of exhaust gas recirculation, complex after-treatment systems, advanced technology of high-strength engines, and underwater exhaust will lead to increased diesel exhaust back pressure (EBP). This will increase the residual exhaust gas and the exchange temperature in the cylinder and reduce the fresh air charged in the next cycle. In this work, the effects of two high EBP conditions (10 kPa and 25 kPa) on the performance of medium-speed ship engines under different loads are explored through experiments. The results show that the increase in EBP from 10 kPa to 25 kPa has little effect on the heat release rate, engine power, and engine start-up time. However, it will lead to ignition advance and the maximum pressure rise rate, peak pressure, and exhaust temperature increase. The increase in EBP has a more significant impact on the small valve overlap angle. Because the reduction in the valve overlap angle has led to an increase in the residual exhaust gas, further increases in EBP causes residual exhaust gas effects to be more pronounced. The effect of increasing EBP on fuel consumption depends primarily on which effect of exhaust back pressure on temperature and fresh air intake dominates.