Improvement of Diesel Combustion Using Pilot Injection and Reduction of Initial Fuel Injection Rate

• Published in: Nihon Kikai Gakkai rombunshuu. B hen Vol. 63; no. 613; pp. 3158 - 3164
• Main Authors: TANAKA, Shotaro, NAKATANI, Koichiro, IKEGAMI, Makoto, YAMANE, Koji
• Format: Journal Article
• Language: Japanese
• Published: The Japan Society of Mechanical Engineers 25.09.1997
• Subjects: Exhaust gases; Fuel injection; Gas emissions; Nitrogen oxides; Nozzles; Orifices; Smoke
• ISSN: 0387-5016; 1884-8346
• DOI: 10.1299/kikaib.63.3158

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 NOx 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 NOx and engine noise. At high load, a reduced rate of initial injection lowers the exhaust NOx 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.