Experimental Study on Emission Characteristics of Engine Under Cold and Hot Start-up Condition at Room Temperature

The emission of pollutants is large during the cold and hot start-up condition of fuel vehicles, so the research on the emission characteristics of start-up has important application and research value to further control the emission of pollutants. Based on the engine testing bench and vehicle on-board emission testing system (portable emissions measurement system, PEMS), the cold and hot start-up emissions of four diesel and two gasoline engines were measured, and the emission characteristics of particulate number (particulate number, PN) and gas pollutants were analyzed and compared. It is found that the PN emission characteristics of diesel and gasoline engine on the cold and hot start condition are similar, but the PN concentration peak is obviously increased on cold start condition, and its concentration is higher than that on hot start condition. The CO and THC emission of diesel on cold start condition is obviously greater than that on hot start condition, but NO_x emission is lower than that on hot start condition. The PN emission peak of gasoline engine is also formed on the cold and hot start-up condition, but it is different from that of diesel, and PN emission peak gradually decreases after surging, while diesel gradually tends to be stable. The CO and THC emissions of gasoline engine on cold and hot start condition show the same varying tendency and similar emission concentrations, but the NO_x emission on cold start condition is significantly higher than that on the hot start condition.