Numeric investigation of EGR and post-injection diesel emissions

In this paper, the effects of post-injection with EGR (exhaust gas recirculation) on diesel emissions are investigated to provide fundamental basis for controlling of EGR and post-injection on diesel. Various EGR rate with or without post-injection keeping the same total injection fuel under the speed of 1650r/min and 50% load conditions were simulated. It was found that soot emissions could keep constant as EGR rate increasing with post-injection compared to without post-injection conditions under low EGR rate (lower than 5%), at the same time NO emissions effectively decreased about 5%. However, as EGR rate is going to increase, soot emissions worsen sharply. Different dwell of Main and Post injection has irregular effects of NO and soot emissions under higher EGR rate of 14.7%, at the same time. NO and soot emissions changed regularly as main and post injection dwell increasing. It was also found that as Main injection timing advancing, the indicated thermal efficiency and soot emissions under high EGR rate were improved. And with 20% EGR, main injection timing advanced to 20° CA BTDC, the indicated thermal efficiency and soot emissions are more perfect than non-EGR.