DOC+DPF系统对柴油机污染物排放特性的影响

Effect of DOC+DPF system on diesel engine pollutant emission characteristics

对装有氧化催化器(diesel oxidation catalyst,DOC)和颗粒捕集器(diesel particulate filter,DPF)后处理系统的柴油机进行台架试验,利用烟气分析仪(Testo 350XL)和发动机废气排放颗粒物粒径谱仪(TSI EEPS 3090)研究不同负荷下柴油机原机、DOC后和DPF后排气中氮氧化物(NO_(x))和颗粒物(particulate matter,PM)的变化规律.结果表明:负荷大于50.0%时,DOC后的NO_(2)体积分数φ(NO_(2))显著增加,柴油机原机氮氧化物中NO_(2)体积分数φ(NO_(2)/NO_(x))随负荷增加而减小,DOC后和DPF后的φ(NO_(2))、φ(NO_(2)/NO_(x))随负荷增加先减小、后增大;柴油机原机PM排放取决于柴油机的运行工况,不同负荷下DOC的PM去除率为15%~30%,50.0%负荷下DOC的PM去除率最高,为26%;DPF的PM去除率超过90%,经过DPF后核态颗粒体积分数明显增加,聚集态颗粒体积分数明显减小.

Based on the diesel engine bench equipped with diesel oxidation catalyst(DOC)and diesel particulate filter(DPF),the flue gas analyzer of Testo 350XL and the engine exhaust particle size spectrometer of TSI EEPS 3090 were used to investigate NO_(x) and particulate matter(PM)variation under different loads before and after the DOC and after the DPF.The results show that the NO_(2) volume fraction ofφ(NO_(2))is increased significantly after DOC when the load is greater than 50.0%.With the increasing of engine load,NO_(2) volume fraction in nitrogen oxidesφ(NO_(2)/NO_(x))of the raw diesel engine is decreased,while theφ(NO_(2))andφ(NO_(2)/NO_(x))of the DOC and the DPF are decreased first with latter increasing.The raw diesel engine PM emission is depended on the operation conditions of the diesel engine.The PM removal rate of DOC is 15%-30%under different loads,and the PM removal rate of DOC under 50.0%load has the highest value of 26%.The PM removal rate of DPF is exceeded 90%.The nucleated particles volume fraction after DPF is increased,while aggregated particles volume fraction is decreased.