基于国Ⅵ标准柴油机SCR系统性能试验研究分析

Research and analysis on SCR system performance test of diesel engine based on ChinaⅥstandard

文章为了研究选择性催化还原(selective catalytic reduction,SCR)系统性能,搭建柴油机后处理试验台架,在柴油机氧化催化器(diesel oxidation catalyst,DOC)+柴油颗粒捕集器(diesel particulate filter,DPF)+SCR+氨氧化催化器(ammonia slip catalyst,ASC)后处理技术路线下进行试验。通过对后处理系统排气背压、温度损失和NO_(x)传感器偏差测试确定搭建的后处理系统的可行性;研究在不同废气流量、不同温度下NH_(3)存储量与NO_(x)转化效率之间的关系以及不同混合器对NO_(x)转化效率的影响。结果表明:NO_(x)的转化效率随着NH_(3)存储量增大而逐渐变大,但该关系又受温度和废气流量的影响;当SCR上游温度在400℃以下时,NO_(x)转化效率随着温度的上升逐渐增加,在400℃以上时,转化效率逐渐减小;NO_(x)的转化效率随着废气流量增大而逐渐降低;新混合器对NO_(x)的转化效率有明显的提升效果。该发动机排放试验结果表明,在WHTC测试循环中的排放测试结果达到国Ⅵ标准要求。

In order to study the performance of selective catalytic reduction(SCR)system,the diesel engine post-treatment test bench was built and the test was carried out under the technical route of diesel oxidation catalyst(DOC)+diesel particulate filter(DPF)+SCR+ammonia slip catalyst(ASC).Through the exhaust back pressure,temperature loss and NO_(x) sensor deviation test,the feasibility of the post-treatment system was determined.The relationship between NH_(3) storage and NO_(x) conversion efficiency under different exhaust gas flow and different temperatures and the influence of different mixers on NO_(x) conversion efficiency were studied.The results show that the NO_(x) conversion efficiency gradually increases with the increase of NH_(3) storage,but this relationship is affected by temperature and exhaust gas flow.When the upstream temperature of SCR is below 400℃,the NO_(x) conversion efficiency gradually increases with the increase of temperature.When the temperature is above 400℃,the conversion efficiency gradually decreases.The NO_(x) conversion efficiency gradually decreases with the increase of exhaust gas flow.The new mixer can also improve the NO_(x) conversion efficiency.Finally,the engine emission test was carried out,and the test results meet the requirements of ChinaⅥstandard in the WHTC test cycle.