基于模型的柴油机Urea-SCR系统闭环控制策略仿真

Model-Based Closed-Loop Control Strategy of Diesel Urea-SCR System Simulation

针对某型柴油机的尿素选择性催化还原(Urea-SCR)系统,在相关SCR化学反应特性试验的基础上,考虑到NH_3泄漏引起的NO_x传感器交叉敏感问题,采用Matlab/Simulink建立了基于模型的SCR闭环控制策略,主要包括动态床温估算模型、起喷温度控制模型、基于NO_x传感器的原机NO_x排放估算模型、空速计算子模型、目标转化效率修正模型、尿素水溶液换算子模型、NH_3泄漏峰值修正以及储氨修正模型等.在此基础上搭建了基于Simulink和GT-Power的耦合仿真平台,并对SCR控制策略进行模型验证.结果表明:柴油机最终NO_x排放为1.92,g/(k W·h),NH_3泄漏的平均体积分数值为9.26×10^(-6),能达到国Ⅴ排放标准.

Based on experiment results of SCR reaction characteristics of a diesel engine with Urea-SCR（urea- selective catalytic reduction）system, a model-based SCR closed-loop control strategy was established by Mat- lab/Simulink code, in which cross-sensitivity of NOx sensor by NH3 leakage was also considered. The control strategy model includes the dynamic bed temperature estimation model, the dosing temperature control model, the original engine-out NOx emission estimation model based on the NOx sensor, the space velocity calculation model, the goal conversion efficiency correction model, the urea aqueous solution conversion model, the NH3 leakage peak correc- tion model and the NH3 storage correction model, etc. Then, the coupling Simulink simulation with the SCR post- processing model in GT-Power was established, and the SCR closed-loop control strategy model was validated. The simulation results show that NOx emissions of the diesel engine is 1.92 g/（kW h） and the mean NH3 leakage is 9.26 × 10-6, which meets China Stage V emission standard.