Effect of Pilot Injection on Diesel Combustion. 2nd Report. Improvement in Trade-Off between NO_x and Fuel Consumption

To reduce the level of exhaust emissions and to improve ignition characteristics, the effect of pilot injection was investigated in a turbocharged direct-injection diesel engine. As a result, it is found that the pilot injection shows some significant effects on reducing the ignition delay and on improving the trade-off relationship between NO_x and fuel consumption. The improvement in the trade-off relationship by pilot injection is observed in both the low-cetane fuel and the high-quality fuel. This simultaneous reduction in NO_x and fuel consumption is caused by a slow rate of pressure rise during the initial combustion which results in a higher mechanical efficiency and a lower cooling loss. In the short interval between pilot and main injection, a small amount of pilot injection is rcommended to reduce both NO_x and fuel consumption without increasing smoke.