基于CFD的SCR混合器设计与结构优化

Design and Structure Optimization of SCR Mixer Based on CFD

为了提高柴油机选择性催化还原(selective catalytic reduction,SCR)后处理系统氨气分布均匀性,设计了扇形和百叶窗型两种不同的混合器结构。利用计算流体动力学(computational fluid dynamics,CFD)技术对这两种混合器结构进行了优化处理,并针对优化后的两种混合器方案,对其速度均匀性、氨气均匀性、压力损失等进行了仿真分析和对比。CFD分析结果表明:百叶窗型混合器结构催化器载体前端氨气分布均匀性更高,百叶窗型混合器的压力损失小于扇形的;进一步分析排气流量和排气温度对氨气均匀性影响,排气流量增加使得氨气均匀性指数降低,排气温度增加使得氨气均匀性指数增高;百叶窗型的氨气均匀性指数高于扇形的。综合考虑,百叶窗型结构混合器优于扇形结构。

In order to improve the ammonia distribution uniformity of diesel selective catalytic reduction(SCR)post-treatment system,two different mixer structures,fan-shaped and louver,were designed.The two mixer structures were optimized by using computational fluid dynamics(CFD)technology.For the optimized two mixer schemes,the velocity uniformity,ammonia uniformity and pressure loss were simulated,analyzed and compared.The CFD analysis results show that the louver mixer structure has higher ammonia distribution uniformity at the front end of the catalyst carrier,and the pressure loss of the louver mixer is less than that of the fan-shaped one.Further analysis of the impact of exhaust flow and exhaust temperature on ammonia uniformity shows that an increase in exhaust flow leads to a decrease of ammonia uniformity index,while an increase in exhaust temperature leads to an increase of ammonia uniformity index.The ammonia uniformity index of louver type is always higher than that of fan-shaped structure.Overall,the louvered structure mixer is superior to the fan-shaped structure.