先立ち噴射および初期噴射率抑制によるディーゼル燃焼の改善

抄録

The effects of pilot injection and reduced initial fuel injection rate on combustion and pollutantand noise-emissions were experimentally studied on a high-speed direct injection diesel engine using an injection system which gives different injection rate waveforms. The results show that the exhaust NO_x concentration at middle load is lowered at a reduced rate of initial injection. For the pilot injection, the pilot fuel amount and the interval between pilot and main injections significantly influence the engine performance and exhaust emissions. At middle load, the pilot injection with a smaller amount and a longer interval may reduce NO_x and engine noise. At high load, a reduced rate of initial injection lowers the exhaust NO_x concentration and noise emission and increases the concentration of smoke. However, the smoke can be significantly reduced by increasing the average injection rate. This characteristic is marked at lower engine speeds and shows little dependency on the nozzle orifice diameter. For this reason, it is concluded that the most favorable situation is high-pressure injection with low-pressure pilot injection.