Abstract: Aiming at the problem that adding sufficient quantities of EGR is difficult for heavy duty diesel engine after the intercooler of intake and emissions is deteriorated in transient operating conditions, a lot of experiments were carried out on a CY6D180 high pressure common rail diesel engine by controlling EGR flow accurately to optimize air-to-fuel ratio,so improving the emissions performance of engine. Based on emissions optimization principle, the steady-state characteristics of engine was studied under the condition of adding EGR after the EGR valve introducted by throttle. A new strategy of two valve turn off and turn on to optimize the engine transient emissions was proposed. The emissions effects under transient operating conditions were verified by experiments,the results show that the proposed strategy can reduce the smoke emission lower than 3.5% as well as NO_x emission lower than 10% steady-state condition point.

Key words: power machinery and engineering, heavy duty diesel engine, exhaust gas recirculation, transient process control, air-to-fuel ratio