重型柴油机固体尿素SCR控制系统设计

Design of Solid Urea SCR Control System for Heavy-duty Diesel Engine

目前SCR系统主要采用基于MAP的前馈控制方式,但是由于NO_X排放模型控制尿素喷射精度低、MAP标定困难等原因,导致下游NH3泄漏量大或者NO_X浓度过高。为了提高SCR控制系统喷射NH3的精确性,使NH3和NO_X的排放量均满足法规要求,针对重型柴油机尿素选择催化还原(Selective Catalytic Reduction,SCR)后处理系统进行了研究。利用MATLAB/Simulink,搭建了化学反应模型和控制策略模型,并将两者整合为以化学反应模型为前馈控制模型。使用RTW将控制模型转化为C代码,将程序移植到Code Warrior的目标工程区进行编译调试。将调试好的程序刷入MC9S12DG256芯片,通过台架试验对所开发的DCU进行功能验证。结果表明,在欧洲稳态循环(European steady state cycle,ESC)和欧洲瞬态循环(European transient cycle,ETC)测试下,NO_X和NH3的排放量均能满足国V法规要求。

SCR system mainly adopts MAP as feed-forward control.But the urea injection control NOx model has low precision,and MAP calibration is difficult,which causes large amount of NH3 leakage or high NOX concentration at the downstream.In order to improve the precision of the SCR control system ejecting NH3,ensure the emission of NH3 and NOX concentration meets the regulatory requirements,this article studied the heavy diesel engine aftertreatment of urea selective catalytic reduction system,set up the model of chemical reaction model and control strategy model by MATLAB/Simulink,and integrated them.It built the control model that used chemical reaction mode as feed-forward,used RTW to convert the control model into C code,and transfered the program to target engineering area that belong to Code Warrior for compilation and debugging.Download the program into the MC9S12DG256 chip.The development of DCU was verified by bench test.The results show that,under the ESC/ETC test,the emission of NOX and NH3 can meet the requirements of the national V regulation.