安装SCR系统的国Ⅳ发动机排放特性研究

试验采用50×10-6和350×10-6两种不同硫含量的燃油,对装有SCR系统的发动机进行ETC和ESC测试,研究了SCR开启/关闭情形下的排放;并采用ELPI分析了在不同条件下颗粒排放差异的原因以及细颗粒的排放特性。试验结果表明:在使用不同硫含量的燃油条件下,NOx排放降低率均可以达到60%以上;SCR开启时,ETC下硫含量350×10-6比50×10-6的颗粒排放增加18%,ETC下颗粒排放均比ESC下增加30%~50%。在50%~70%负荷时,颗粒数目排放较低,低负荷和全负荷时颗粒排放较高,全负荷时最高;在负荷一定时,转速越高,颗粒排放浓度越高;使用低硫燃油,颗粒物质量排放较低,而数目排放却增多;多出的部分主要是粒径小于100 nm的超细颗粒。

Study on Emission Characteristic of Engine with SCR System

An engine with SCR system was tested on the engine bench according to ETC and ESC test cycle, and two kinds of diesel fuel with sulfur content of 50×10~(-6) and 350×10~(-6) were used in the test .The emission results with and without SCR system were compared. The transient PM emission was measured by ELPI, and the PM emission difference and the characteristics of fine particles under different conditions were also analyzed. The results show that when using SCR, the NO_x emission is decreased by more than 60%, and the PM emission of 350×10~(-6) sulfur fuel is higher 18% than that of 50×10~(-6) sulfur fuel in ETC test cycle. The PM emission in ETC is higher 30% to 50% than that in ESC. At 50% to 70% load, the particulate amount is lower, at low load the particulate amount is higher, and at full load the PM amount is highest. At constant load, the higher the speed, the higher the particulate emission. Using lower sulfur fuel, the PM mass emission is lower but the PM amount increases, and the most particles are ultra-fine particles with diameters less than 100nm.