为解决传统SCR（Selective Catalytic Reduction）催化器在排气温度较低的低负荷工况下出现在尿素喷嘴或混合器壁面形成尿素结晶等问题，运用CFD方法对传统SCR催化器进行结构优化，设计出了一种新型SCR混合器，并提出了新的尿素喷嘴布置方案。仿真结果表明：优化后的SCR催化器能够促进尿素溶液和尾气的充分混合，尿素热解率和载体前端面NH₃分布均匀性指数分别提高了9.76%和6.06%。对优化后的SCR催化器进行稳态点性能验证试验、瞬态ETC排放测试试验以及30 h发动机台架尿素结晶验证试验。试验结果表明：新结构在氨氮比为0.7，0.9和1.2时的NO_x转化率分别提高0.89%，1.76%和0.61%；与传统结构相比，新结构NO_x排放明显降低；新结构混合器壁面未出现尿素结晶。

In order to avoid the urea crystallization on urea nozzle or mixer wall of conventional SCR catalyst under low load conditions with low exhaust gas temperature, the structural optimization of SCR catalyst was conducted with CFD method and a newtyped SCR mixer was designed. The corresponding distribution pattern of urea nozzle was also proposed. The simulation results show that the optimized SCR converter can promote the mixing between urea solution and exhaust gas. The thermolysis rate and concentration distribution uniformity index of NH₃ for fore end face increases by 9.76% and 6.06% respectively. A series of verifications such as steadystate test, ETC test and 30hour urea crystallization test are conducted on the test bench. The test results show that the new structure can increase NO_x conversion rate by 0.89%, 1.76% and 0.61% respectively when the ratio of ammonia and nitrogen is 0.7, 0.9 and 1.2. Compared with the original structure, the new structure can significantly reduce NO_x emission and avoid urea crystallization on the wall of new mixer.