Effects of EGR on combustion process of DI diesel engine during cold start

Experiments on the effects of external and internal exhaust gas recirculation (EGR) on combustion and emission performance during a cold start process were investigated in a 135 single-cylinder DI diesel engine. Combustion was improved during the initial ignition cycles by introducing internal or external EGR. The addition of an appropriate amount of internal or external EGR can promote the combustion stability significantly. However, excessive amounts of external EGR could lead to extremely unstable combustion or even misfiring. An appropriate amount of internal or external EGR decreased smoke opacity effectively during a cold start. External EGR reduced NO _x emissions effectively while internal EGR led to an increase in NO _x emissions due to thermal effects. __________ Translated from Transactions of CSICE, 2007, 25(3): 193–201 译自:内燃机学报]