摘要
以柴油机选择性催化还原(SCR)后处理系统为研究对象,对SCR催化器化学反应机理进行了系统的研究,并建立了SCR催化器模型,设计了基于模型的SCR控制策略和车载故障诊断(OBD)策略.为了便于建模,沿着气流轴线方向将SCR催化器分为数个理想的SCR单元,并建立了SCR催化器的化学反应动力学模型和温度模型等.然后设计了基于自适应滑模观测器的催化器状态观测器.利用反步法设计了SCR控制器,对SCR催化器沿着气流轴线方向的储氨状态分布进行控制,实现减少NOx排放的同时避免氨(NH3)泄漏造成的二次污染.最后,开发了基于模型的OBD策略,并进行了试验验证,结果表明:基于模型的SCR控制策略和OBD策略是有效的.
The selective catalytic reduction(SCR)after-treatment technique for diesel engine was studied. The model of SCR catalyst was established by investigating its chemical reaction mechanism systematically. Then,the SCR control strategy and the on-board diagnostics(OBD)strategy were designed. In order to establish the model conveniently,the SCR catalyst was divided into several ideal SCR cells along the direction of the airflow axis. A state observer based on adaptive sliding mode observer was provided. The SCR controller was designed by the backstepping method,hence,the distribution state of SCR ammonia storage in the direction of the airflow was controlled.Therefore,the ammonia storage control could implement the objectives of which the NOxemission is reduced and the secondary pollution caused by ammonia leakage is avoided simultaneously. Then,a model-based OBD strategy was provided. The performance of the proposed strategies was verified. The results show that the proposed strategies are effective whether there encounter faults.
引文
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