【作者】 胡振奇；

【导师】 朱昌吉；

【作者基本信息】 吉林大学 ， 动力机械及工程， 2012， 硕士

【摘要】 面对越来越严格的排放法规，重型柴油机SCR后处理技术已成为满足日益严格的排放法规的主流技术路线。本文针对SCR后处理系统中的核心技术——尿素喷射策略进行了深入研究，设计了SCR控制系统软件构架，分别提出了基于标定脉谱和SCR模型的尿素喷射策略并进行了实验验证。设计了基于标定脉谱的尿素喷射控制策略，并通过软件仿真进行了验证。其中包括带瞬态修正的发动机的NOx原始排放估算算法；NOx的最大转化效率脉谱选择；尿素喷射量计算算法，及利用温度、储氨、老化等参数对喷射量进行修正的算法；以上算法功能都通过MATLAB/SIMULINK软件进行了验证。基于化学动力学及传热学原理，设计了SCR模型，并提出了基于模型的尿素喷射控制策略。该策略利用观测器计算SCR催化器内部的储氨及温度，根据状态观测器的结果及目标NH3的泄露浓度反推尿素喷射量，从而实现基于模型的前馈算法，仿真结果表明该算法可以更为有效的控制系统的NH3泄露。为了对算法进行实验验证，本文根据国内外文献设计了一套SCR系统管理软件。该管理软件分三个层次：上层状态机模块、中层状态迁移监控模块和底层设备控制模块。状态机模块控制SCR系统不同的工作状态；状态迁移监控模块负责采集底层设备模块处理好的各种信息，并将这些信息整合提供给上层状态机，同时根据上层状态机的状态控制底层设备动作；底层硬件设备模块主要是进行传感器的信号调理和执行器驱动；喷射策略只在系统计量喷射状态下有效。为了验证算法的有效性，本文搭建了发动机试验台架，将SCR尿素喷射控制策略及软件管理系统下载到dSPACE快速原型中，旁路原有ECU中的后处理算法，驱动后处理系统中的部件。ESC稳态测试循环和ETC瞬态测试循环实验结果表明，应用本文提出的尿素喷射策略的后处理系统SCR下游NOx及NH3浓度都得到了很好的控制，达到国Ⅴ排放法规的要求。更多还原

【Abstract】 As the emission regulation becomes more and more strict, The Selective CatalystReduction of the heavy-duty diesel engine has become the main stream of the after-treatmenttechnique to meet increasingly stringent emissions regulations. The paper is based on theresearch of the SCR urea dosing control strategy, which is the core of the SCR technology. Itgives a design of control system of the SCR manage software, it also has accomplished theurea dosing strategy on calibration of the map and the SCR model,as well as experimentalverification on test bed.A control strategy based on the map has been designed and were verified throughsoftware simulation.,which including the estimation of the original NOx emission withtransient correction of the algorithm, the design of the NOx conversion efficiency Map; thecalculation algorithm of the urea injection, and the correction algorithm of temperature,storage ammonia,aging parameters on the injection quantity, The above dosing strategyarithmetic verified by MATLAB/SIMULINK software.The paper also designed a model of catalytic converter on the basis of the chemicalkinetics and heat transfer theory,and also given a model based urea dosing controlstrategy.The strategy takes advantage of the observer to calculate the internal storage ofammonia and temperature of the SCR model, obtains the amount of the urea injectionaccording to the results of the state observer and the target of NH3concentration to achievemodel-based feedforward algorithm, the simulation results show that the algorithm can bemore effective on the leak of NH3.In order to verify the algorithm on test bed, The SCR management software system hasbeen designed based on the documentations from home and abroad. The system is consistedof three layers: the upper is the state machine module, the middle is the monitoringcomponent module and the lower is equipment control module. The state machine modulecontrols the the SCR system under different states.The monitoring component module is responsible for the collecting the variety of message from the lower equipment module,assembling them as the prerequisite of the state transformation, at the same time controllingthe actions of the lower equipment module according to the state of the state machinemodule.The lower equipment control module mainly drives the actuator, and adjusts sensorsignal. According to the calculated amount of urea injection control strategy it controls thedosing system on the urea dose volume in meteringcontrol state.In order to testify the effectiveness of the algorithm, the engine test bench was set up.the SCR urea dosing control strategy and software management system were downloadedinto RCP based on the dSPACE. And the RCP was taken as the DUC instead of the originalECU to control the SCR components. The ESC steady-state test cycling and ETC transienttest cycling were carried out respectively. The results show that the concentration of NOxand NH3on the SCR downstream have been well controlled with the application of the ureadosing strategy system proposed here, and it can meet the requirements of State Ⅴemission regulations.更多还原