重型柴油机欧Ⅵ后处理系统构型方案试验研究

摘要

以柴油机氧化催化器(DOC)、催化型柴油机颗粒捕集器(CDPF)、选择性催化还原催化器(SCR)及氨氧化催化器(ASC)为研究对象,利用发动机台架,对DOC-CDPF-SCR-ASC和DOC-SCR-CDPF两种不同的后处理系统构型方案在不同测试循环下的NOx转化效率、NH3泄漏、N2O排放、颗粒(PM)排放、颗粒数(PN)排放及CDPF的被动再生效果进行了对比研究.研究表明:两种构型方案下的PM及PN排放基本一致;DOC-CDPF-SCR-ASC构型方案具有更高的NOx转化效率和颗粒物被动再生效果,该构型方案下CDPF对SCR催化器入口处的NO2/NOx摩尔比起到调控作用,使其更有利于SCR的反应,同时由于CDPF中的被动再生及NO氧化反应会释放热量,SCR催化器平均温度与DOC-SCR-CDPF构型方案下差别不大;而DOC-SCR-CDPF构型方案下,CDPF可以起到ASC的作用且具有更低的氨泄漏,但会产生较高的NO2和N2O排放.%Taking diesel oxidation catalyst (DOC), catalyzed diesel particulate filter (CDPF), selective catalytic reduction (SCR) catalyst, and ammonia slip catalyst (ASC) as objects, the performances of DOC-CDPF-SCR-ASC and DOC-SCR-CDPF aftertreatment system configurations were compared on an engine test bench with several test cycles, including NOx conversion efficiency, NH3 slip, N2O emission, particle mass (PM) and particle number (PN) emission, and CDPF passive regeneration.The results show that these two kinds of configurations almost have the same effect of PM and PN emission reduction.The DOC-CDPF-SCR-ASC configuration has a better NOx conversion efficiency and CDPF passive regeneration performance.For this configuration, the CDPF has a regulating effect on the NO2/NOx ratio at the inlet of the SCR catalyst, which can improve the SCR conversion efficiency, and the mean temperature of the SCR catalyst of this configuration is very close to that of the DOC-SCR-CDPF configuration due to the heat release of passive regeneration and NO oxidation in the CDPF.For the DOC-SCR-CDPF configuration, the CDPF can play a role of ASC and lead a lower NH3 slip, but it will produce a certain amount of NO2 and N2O emission.