柴油机SCR后处理系统控制策略

SCR Post-processing System Control Strategy of Diesel Engine

摘要:

国Ⅳ/Ⅴ柴油机采用SCR后处理技术相比其它技术有更多优势。为开发NH3-SCR后处理系统控制策略，采用试验与仿真相结合的方法，首先应用状态机理论设计SCR系统协调控制策略，并在Matlab平台中进行仿真测试，然后通过台架试验对建立的原机排放预估模型、催化器内部氨氮反应当量比计算模型和NH3目标覆盖度预估模型进行测试和标定，最后完成催化器载体瞬态温变滞后修正算法和瞬态工况NH3泄漏控制策略。设计的SCR控制系统瞬态工况的鲁棒性好，NOx转化率控制在60%左右，NH3泄漏平均值控制在1.0×10 -5 以下。将基于本系统控制策略的计量控制单元（DCU）应用到目标发动机，ESC和ETC试验测试的NOx比排放分别为3.01g/(kW·h)和3.15g/(kW·h)，满足国Ⅳ标准。

Abstract:

SCR post-processing technology had more advantages than other technology which applied to Euro Ⅳ/Ⅴ diesel engine. In order to develop control strategy of SCR post-processing system, methods of experiment and simulation were employed. Firstly coordination control strategy was designed and tested in matlab based on the state machine theory, then raw emission model, NH3 target coverage rate estimation model and mass ratio calculation model of NH3 and NOx chemical reaction from SCR catalyst were calibrated by bench test, finally correction algorithm for heat hysteresis of catalyst substrate and NH3 leak control strategy in the transient operation condition were fulfilled, which improved the SCR control system robustness. The dosing control unit using above control strategy was adopted in the target engine, which made NOx conversion efficiency achieve 60 percent and average NH3 leak equal to 1×10 -5 . Emission NOx value of ESC and ETC was 3.01g/(kW·h)和3.15g/(kW·h), which validated the heavy duty diesel engine can satisfy Euro Ⅳ emissions regulations.