方今朝¹，刘会猛²，高超¹，董昕¹，张选国¹，李光义¹

1.万向通达股份公司技术中心，湖北 武汉 430056；

2.华中科技大学能源与动力工程学院，湖北 武汉 430074

摘要：为满足国六排放标准对NO_x转换效率的要求，优化设计某车用柴油机的选择性催化还原（selective catalytic redution，SCR）混合段结构，仿真分析不同混合段结构的三维流场，比较流场速度均匀性和氨均匀性；按照国六车用柴油机排放控制要求的工况条件，进行发动机台架试验，测试尿素结晶和NOx转化效率。仿真和试验结果表明：SCR混合段增加混流板可显著提高气体流场速度均匀性和氨均匀性；优化后，带混流板2的SCR混合段结构抗结晶试验测得的尿素结晶不大于1.0 g，氨均匀性大于0.985，氨氮摩尔当量比为1.2时NO_x转化效率超过99%，满足产品排放控制性能要求。

关键词：车用柴油机；排放后处理；SCR；混合段结构；结构优化设计

Abstract：In order to meet the NO_x conversion efficiency requirements of China VI emission regulations, the structural optimization design of SCR mixing section of a vehicle diesel engine is carried out. The 3D flow field characteristics in the mixing section of different structures is simulated and analyzed, focusing on the comparison of the velocity uniformity and ammonia uniformity of the flow field. The engine bench test is carried out, and the deposition mass and NO_x conversion efficiency are tested according to the working conditions required by the emission regulation of China Ⅵ vehicle diesel engine emission standards. The results show that adding a mixing plate in the SCR mixing section can significantly improve the velocity uniformity of the gas flow field and the ammonia uniformity. After optimization, the urea crystal of the SCR mixing section structure with the mixing plate 2 is no more than 1.0 g, the uniformity of ammonia is more than 0.985, and the NO_x removal efficiency exceeded 99% when the NH3/NOx molar equivalent ratio is 1.2. The optimized SCR mixing section structure with mixed flow plate 2 can meet the requirements of emission control.

Keywords:vehicle diesel engine; emission aftertreatment; SCR;mixing section structure; structural optimization