SCR系统尿素喷雾特性影响因素的CFD仿真分析

利用AVL Fire三维商用仿真软件对SCR系统尿素喷雾特性的影响因素进行了模拟计算,考察的因素包括工况、尿素喷射压力、尿素水溶液的温度及喷嘴的安装角度。结果表明:喷雾形态受来流影响较大,喷雾的速度及贯穿距离随排气流量增加,排气流量越小,排气温度(SCR喷嘴处排气温度)越高,越利于喷雾液滴的蒸发和热解;喷射压力对液滴的喷雾形态影响不大,但对NH3的浓度场分布影响较大,喷射压力越高,NH3的生成效率越低;尿素溶液温度对喷雾形态及NH3的转化影响不大;喷嘴安装角增大利于喷雾液滴蒸发和热解。

CFD Simulation of Factors Influencing Urea Spray Characteristic for SCR System

The influencing factors of urea spray characteristic for SCR system were simulated and calculated with the CFD simulation method.The researched factors mainly included working condition,urea injection pressure,urea solution temperature and nozzle mounting angle.The results show that the spray form is greatly influenced by the exhaust stream.The spray speed and penetrating distance increase with the increase of exhaust flow.The lower the exhaust flow is,the higher the exhaust temperature is(SCR box inlet temperature),and the spray droplet is easer to evaporate and thermally decomposed.The injection pressure has minor influence on droplet spray form,but has great influence on NH3 concentration distribution.The higher the injection pressure is,the lower the NH3 generation efficiency is.The urea solution temperature has minor influence on spray form and NH3 transformation.The increased nozzle mounting angle is helpful for spray droplet evaporation and thermal decomposition.