为研究重型柴油货车实际运行状态下EGR、SCR控制技术对NOx排放的影响，开展了车辆RDE试验研究。设计了单EGR、SCR+EGR与无排放控制技术3种配置的车载试验方案。测试车辆沿市区、市郊与高速路况行驶,测试瞬时NOx排放、车速、排气温度、EGR率、发动机转速与负荷等。分析了NOx排放与车速、发动机工况、EGR率、排气温度的关系，比较不同排放控制方案下NOx排放的异同。结果表明：无排放控制技术时，NOx排放随车速增加而增加；配置EGR+SCR时，NOx排放随车速增加呈下降趋势，高速区NOx排气体积分数低于低速区。分析表明，排气温度升高，SCR对NOx的净化效率提高，EGR率增大NOx排放降低，低速工况下EGR率最高。EGR、SCR、EGR+SCR 3种控制技术对NOx的减排率分别在16%，51%，92%以上。
The RDE test of a heavyduty diesel truck was carried out in order to study the effects of EGR and SCR control techniques on improving NOx emission in real conditions. Three test schemes were designed including single EGR, SCR and EGR, and uncontrolled measures. The vehicle ran along the urban, suburb and high way and the instantaneous NOx emission concentration, vehicle speed, exhaust temperature, EGR rate, engine speed and load were measured. The analysis was conducted to find the relationship between NOx emission and vehicle speed, engine operating conditions, EGR rate and exhaust temperature, and the comparison was conducted to find the differences of NOx emission between different control configurations. The results show that NOx emission increases with the increase of vehicle speed without any emission controls, decreases with the increase of vehicle speed and has a higher concentration in high speed region with EGR and SCR controls. In addition, the high exhaust temperature can lead to a better efficiency of SCR and the increase of EGR rate can also lead to the reduction of NOx. It is found that the EGR rate is the highest at low speed. The reductions of NOx emission for EGR, SCR, and EGR and SCR were over 16%, 51% and 92% respectively.
