基于CFD的非道路车辆尾气后处理器性能研究

Research on the Performance of Off-Road Vehicle Exhaust Processor Based on CFD

摘要: 本文针对一款非道路柴油机的尾气后处理装置进行了仿真和实验研究。应用计算流体力学软件建立了尿素溶液的喷射、液滴雾化以及蒸发模型，液滴与固体壁面相互作用模型。研究了一种基本型系统的SCR系统对尿素液滴雾化、蒸发和分解及SCR催化剂载体入口NH3分布均匀性、烟气速度均匀性、压力损失、液膜分布的影响。数值计算结果显示，该系统的结构紧凑化设计(短系统)后在烟气速度均匀性、氨气浓度均匀性、系统总压损失方面均满足设计要求；基于对液膜分布与累积量的计算和评价，短系统的抗结晶性能好于长系统，具备相对更高的系统耐久性能。同时，设计了一组稳态发动机台架结晶对比实验，台架试验得出了与仿真相一致的结晶趋势，短方案抗结晶能力强于长方案，另一方面也验证了CFD手段在系统结晶风险预测上的有效性。

Abstract: On this paper, the simulation and experimental research on the exhaust gas after-treatment device of an off-road diesel engine is carried out. The models of injection, droplet authorization and evapo-ration of urea solution and the interaction between droplet and solid wall were established by using computational fluid dynamics software. The effects of SCR system on automation, evaporation and decomposition of urea droplets, distribution uniformity of NH3 at the inlet of SCR catalyst carrier, velocity uniformity of flue gas, pressure loss and liquid film distribution were studied. The numeri-cal results show that the basic design of the system (short system) meets the design requirements in terms of flue gas velocity uniformity, ammonia concentration uniformity and total pressure loss. Based on the calculation and evaluation of liquid film distribution and accumulation, the crystalli-zation resistance of the short system is better than that of the long system, and the system durabil-ity is relatively higher. At the same time, a set of steady-state engine bench crystallization compari-son experiments were designed. The bench tests obtained the crystallization trend consistent with the simulation, and the anti-crystallization ability of the short scheme was stronger than that of the long scheme, which also verified the effectiveness of CFD method in the system crystallization risk prediction.