To respond the China’s “14th Five-Year Plan” on the control of nitrogen oxides (NO) emission, urea-based selective catalytic reduction (SCR) system has been widely applied to reduce the NO emission from the diesel engine. NO is no longer a factor to be ignored while refining the SCR-DeNO system model because of the ship diesel engine's long-term low temperature and oxygen-rich condition, which provides abundant conditions for the creation of NO. Therefore, a refined eight-state two-cell SCR-DeNO model is established in this paper. Meanwhile, the trade-off between NO emission and tailpipe ammonia (NH) slip is one of the major challenges which SCR-DeNO system is facing. While meeting NO emission standards, the requirement of limiting NH slip to prevent secondary pollution is becoming increasingly urgent, which needs a better structure or controller. Therefore, a two-cell SCR-DeNO system with a by-pass valve in front of the NH injection is designed, integral sliding mode control based on inversion algorithm (IA_ISMC) is proposed for each cell. Based on the FTP-75 test cycle, there are three points of view are presented. Firstly, compared with the traditional six-state model, simulation results from the refined eight-state SCR-DeNO model are closer to the experimental data. Secondly, the introduction of the by-pass structure has a mild impact on the NO conversion efficiency, but can largely limit the NH slip. Finally, the controller based on IA_ISMC effectively improves the tracking performance of NH coverage ratio and reduces the cost of NH injection. To sum up, the refined two-cell SCR-DeNO system with a by-pass valve based on IA_ISMC can enhance SCR performance and lower costs.

中文翻译：

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基于IA-ISMC的新型两室SCR-DeNOX系统配置的氨覆盖率控制


为响应国家“十四五”控制氮氧化物（NO）排放的规划，尿素基选择性催化还原（SCR）系统已广泛应用于降低柴油机NOx排放。由于船舶柴油机长期处于低温富氧状态，为NO的生成提供了丰富的条件，NO不再成为精炼SCR-DeNO系统模型时不可忽视的因素。因此，本文建立了完善的八态两电池SCR-DeNO模型。同时，NO排放和尾气氨（NH）逃逸之间的权衡是SCR-DeNO系统面临的主要挑战之一。在满足NO排放标准的同时，限制NH逃逸以防止二次污染的要求变得越来越迫切，这需要更好的结构或控制器。因此，设计了在NH注入前带有旁通阀的两单元SCR-DeNO系统，并为每个单元提出了基于反演算法（IA_ISMC）的积分滑模控制。基于FTP-75测试循环，提出了三个观点。首先，与传统的六态模型相比，改进的八态SCR-DeNO模型的仿真结果更接近实验数据。其次，旁路结构的引入对NO转化效率影响较小，但可以很大程度上限制NH逃逸。最后，基于IA_ISMC的控制器有效提高了NH覆盖率的跟踪性能，降低了NH注入的成本。综上所述，基于IA_ISMC的带旁通阀的精制两室SCR-DeNO系统可以提高SCR性能并降低成本。