【作者】 刘传宝；

【导师】 颜伏伍；

【作者基本信息】 武汉理工大学 ， 动力机械及工程， 2013， 博士

【摘要】 在国N/V阶段,对于柴油机排放控制有两条技术路线可以选择,其中选择催化还原(SCR)技术是一种能显著降低柴油机NOx排放的后处理技术。围绕SCR系统产业化需要解决的关键技术,论文着重研究了SCR电控单元硬件可靠性设计、SCR电控单元匹配标定系统、添蓝喷射控制策略和SCR系统故障诊断,并将开发的SCR电控单元安装到某主机厂6.6L柴油机进行匹配应用。论文首先根据控制需求,综合考虑振动、散热、可靠性、成本、安装、调试和版本升级等因素,完成SCR电控单元硬件设计。从电路原理和印刷电路板两个方面进行电磁兼容性设计,并对设计的电控单元进行可靠性测试。然后应用成熟通用标定软件Vision建立SCR电控单元标定平台,可实现数据实时采集、在线标定以及刷写标定数据等功能。引入ASAM的MCD三层模型,基于CCP协议利用VB环境自主开发了标定软件,同时将基于ISO1576协议开发的诊断软件集成到标定系统中,实现测量、标定和诊断一体化。其次通过理论分析结合试验研究结果建立了原机NOx排放预估模型以及NOx传感器信号加速计算子模型。通过对SCR催化剂活性研究确定使用催化器床温和排气流量代替转速和负荷作为添蓝最佳供给系数kop和NOx目标转化效率等基础脉谱的输入量,可以削弱环境影响,并设计了基于模型的添蓝预喷射前馈控制策略,并通过ESC和ETC循环试验对排放模型预测精度和前馈控制算法鲁棒性进行验证。之后进行NH3存储特性试验研究,结果表明NH3覆盖度对瞬态过程中的NH3泄漏影响很大,每个工况对应一个能确保快速升温过程中NH3泄漏体积浓度不超过1.0×10-5并能尽量提高NOx转化效率的NH3覆盖度限值。基于研究结果建立了催化器表面NH3覆盖度和存储量估计模型,提出了NH3泄漏控制策略。最后根据OBD法规对SCR系统要求监视的内容,应用阈值诊断法对SCR传感器电路开路和短路进行诊断；应用逻辑诊断法对传感器信号合理性进行诊断；应用综合诊断法对SCR系统状态异常和NOx排放超标等进行在线诊；利用稀释添蓝的方法对NOx超标诊断模型进行故障模拟测试,验证其算法的鲁棒性,利用对下游NOx浓度衰减的方法对NOx传感器信号失真诊断算法的合理性进行验证。更多还原

【Abstract】 There are two technical routes that we can choose for National IV/V stage, among them selective catalytic reduction (SCR) can significantly reduce the NOx emission of diesel engine. Around the key technologies that need to be solved of industrialization of SCR system, this paper focuses on the research of SCR ECU Hardware reliability design, AdBlue injection control strategy, fault diagnosis system and SCR ECU calibration system, we also install the developed SCR ECU to the6.6L diesel of a host plant to matching application.Firstly, this paper completed the hardware design of SCR electronic control unit according to functional requirements, considering the vibration, heat dissipation, reliability, cost, installation, debugging, version upgrades, et al. Electromagnetic compatibility design was taken based on two aspects:circuit schematic and PCB, and reliability of designed electronic control unit was tested.Then this paper apply ATI’s calibration software Vision to establish the SCR ECU calibration platform, which can realize monitoring variable, online calibration, write calibration data to ECU Flash, et al. Based on Polling and DAQ mode of CCP protocol, introduced the MCD three layer model of ASAM, we develop a calibration system for electronic control unit using VB environment. A diagnostic software was developed based on ISO15765protocol and was integrated into the calibration system.Secondly, through theoretical analysis and experimental research results we established the raw emissions NOx prediction model and calculation model of accelerated NOx sensor signal. Based on the research on the performance of SCR catalyst we determined using the catalyst bed temperature and exhaust mass flow instead of speed and load as input of basic pulse spectrum of optimal AdBlue supply coefficient KoP and NOx target conversion efficiency, which can reduce environmental impact. we design the feedforward control strategy of AdBlue injection control based on the model. ESC and ETC cycle test verified emissions prediction accuracy and robustness of the feedforward control algorithm.The paper also studied on NH3storage characteristics of catalytic converter during work, the results show NH3coverage ratio has a great influence on NH3leakage in the transient process. Each operation point has a NH3coverage ratio threshold which can ensure NH3leakage volume ratio is less than1.0×10-5during the rapid heating process and try to improve the NOx conversion efficiency. According to the research results of the NH3coverage ratio and storage capacity on the catalyst surface, we established estimation model, put forward the leakage control strategy.According to the OBDI+NOx stage monitoring requirements for SCR system, this paper apply threshold diagnosis method, logical diagnosis method and the synthetical diagnosis method to make diagnosis of electrical circuit, system state abnormity and sensor signal rationality. In order to prevent further emission deterioration, NOx emission excess diagnosis algorithm was developed. Finally, each type of diagnostic algorithm was validated.更多还原