柴油机双SCR体积分配仿真分析

王加林^1，2，王琛^1，2，孙建颖^1，2*，冯海娣^1，2

1.潍柴动力股份有限公司，山东 潍坊  261061；2.内燃机与动力系统全国重点实验室，山东 潍坊  261061

摘要：为满足不断升级的排放标准对柴油机污染物排放日趋严格的要求，采用AVL Cruise M软件建立双选择性催化还原(selective catalytic reduction，SCR)系统仿真模型，基于全球统一瞬态测试循环（world harmonized transient cycle，WHTC）分析紧耦合SCR和后级SCR体积分配对NO_x和N₂O排放、尿素喷射的影响。结果表明：紧耦合SCR体积减小，其下游NO_x累计排放先减少后增多，N₂O累积排放逐渐减少，第二级尿素喷射提前；后级SCR体积增大，NO_x比排放减少但N₂O比排放增大，第二级尿素喷射延迟；最优紧耦合、后级SCR体积分别为1/3V、V(V为现有某国六柴油机SCR的体积)，此时对应的冷态WHTC、热态WHTC、加权NO_x比排放分别为0.609、0.037、0.119 g/(kW·h)；冷态WHTC、热态WHTC、加权N₂O比排放为0.222、0.218、0.219 g/(kW·h)。双SCR系统体积优化分配后，NO_x与N₂O排放均较低。

关键词：双SCR系统；紧耦合SCR；体积分配；NO_x排放；N₂O排放

Volume allocation simulation analysis for dual SCR system in a diesel engine

WANG Jialin^1,2, WANG Chen^1,2, SUN Jianying^1,2*, FENG Haidi^1,2

1.Weichai Power Co., Ltd., Weifang 261061, China;

2.State Key Laboratory of Engine and Powertrain System，Weifang 261061, China

Abstract: In order to meet the increasingly stringent requirements for diesel engine pollutant emissions from constantly upgrading emission standards, AVL Cruise M software is used to establish a simulation model of a dual selective catalytic reduction (SCR) system. Based on the world harmonized transient cycle (WHTC), the impact of close-coupled SCR and under flow SCR volume allocation on NO_x and N₂O emissions, as well as urea injection, is analyzed. The results show that as the volume of close-coupled SCR decreases, the downstream cumulative NO_x emissions first decrease and then increase, the cumulative N₂O emissions gradually decrease, and the second stage urea injection ad vances. The volume of the under flow SCR increases, the NO_x specific emissions decrease but the N₂O specific emissions increase, and the second stage urea injection is delayed. The optimal volumes of close-coupled SCR and under flow SCR are 1/3V and V(V is the current volume of SCR in a China VI engine), respectively. At this time, the corresponding cold WHTC, hot WHTC, and weighted NO_x specific emissions are 0.609, 0.037, and 0.119 g/(kW·h), respectively; the cold WHTC, hot WHTC, and weighted N₂O specific emissions are 0.222, 0.218, and 0.219 g/(kW·h), respectively. After optimizing the volume allocation of the dual SCR system, both NO_x and N₂O emissions are lower.

Keywords: dual SCR system; close-coupled SCR; volume matching; NO_xemission; N₂O emission