Effect of pilot injection on diesel combustion (3rd Report, Effect of decrease in the amount of pilot injection)

For reducing exhaust emissions, the effect of pilot injection with a short pilot-main interval on combustion was investigated in a turbocharged direct injection diesel engine. Although the amount of pilot injection could be decreased by increasing the Dodge plunger seat diameter, two types of technique for reducing the amount of pilot injection were examined to suppress an increase in smoke due to pilot injection; one is a reduction in the nozzle-hole diameter and the other is an increase in the spring chamber pressure. Each technique was compared from the view points of combustion, smoke density and the trade-off relationship between NO_x and fuel consumption. Smoke is reduced as the amount of pilot injection decreases while the trade-off between fuel consumption and NO_x is markedly improved by reducing both the nozzle-hole diameter and the amount of pilot injection.