An analytical study has been carried out to investigate how the factors affecting ignition and formation of NOx and smoke can be influenced in indirect injection (IDI) diesel engines in order to increase engine output and reduce idling noise.
It was found that controlling the heat release ratio between the swirl and main chambers was effective in reducing smoke and NOx emissions and in improving engine output. It vas also found that making the air jet flow counter to the fuel spray injected into the swirl chamber was effective in dispersing and atomizing fuel. This shortened the ignition delay period and reduced idling noise as a result.
These factors have been incorporated into a newly developed dual-throat jet combustion system in which a sub-throat is provided in the swirl chamber, in line with the center axis of the fuel injection nozzle, in addition to the ordinary main throat. The new system achieves marked improvements in engine output and idling noise level of IDI diesel engines while reducing exhaust emissions.