In the diesel engine field, increasingly strict emission regulations and customer requirements have necessitated advanced technology.
One important subject for diesel engines is cold startability and white smoke under cold conditions. In this paper, the combustion mechanism of a multi cylinder engine under cold conditions is discussed.
First, during a starting condition, it is proved that the cold flame, which is caused by previously misfired fuel during intermittent combustion, promotes good combustion on the following cycle.
Secondly, following engine starting, it is estimated that there is minimum fuel quantity above which combustion is carried out. The minimum fuel quantity depends upon the temperature of the combustion chamber. Unbalance between the minimum fuel quantity and actual injection quantity results in white smoke emission.
From this analysis, in order to improve diesel engine performance at cold condition, we have introduced a “MULTI INJECTION” strategy by using a common rail type fuel injection system, called, “ECD-U2”. Great improvement in both cold starting time and white smoke emission are confirmed.