The effects of EGR and ignition timing on engine emissions and combustion were studied through an experiment carried out on an air-guided GDI engine.The test results showed that the ignition timing significantly affected the GDI engine emissions,that the NOx emissions significantly reduced when the ignition timing was retarded,and that NOx emissions decreased with the EGR level increasement.A higher EGR rate could reduce CO emissions while the CO emissions were less affected by the ignition timing.The HC emissions decreased at a lower EGR rate.At 2500 r/min,an appropriate EGR rate could cut down CO emissions.The exhaust gas temperature could significantly decrease with improving the EGR rate,and the exhaust gas temperature at 2500 r/min was clearly higher than that at 1850 r/min.The nucleation mode particles increased clearly,the accumulation mode particle number decreased gradually with the increase of EGR rate,and the typical particle size of nucleation mode particle was in the range of 10–25 nm.
ZHAO LiFengYU XiuMinQIAN DingChaoDONG WeiSUN PingHE LingYANG Song
