COMBUSTION IMPROVEMENT FOR REDUCING EXHAUST EMISSIONS IN IDI DIESEL ENGINE

Means for reducing PM from a swirl chamber type diesel engine were examined and the mechanisms of the PM reduction were investigated using both a multi-cylinder and an optically accessible single-cylinder engine. The following points were clarified. (1) At light load, suppression of initial injection rate reduces PM, because of both the change of ignition point to reduce SOF, and the retarded flowout of dense soot from the swirl chamber to reduce smoke. (2) Over medium load, the main cause of the exhaust smoke is hard spray-wall impingement which leads to both fuel adhesion on the wall and the stagnation of rich fuel-air mixture.