通用型SCR系统的自学习控制及适用性评价

发布时间：2018-08-03 18:38

【摘要】：在传统往复活塞式内燃机中,相对于汽油机而言,由于柴油机当量压缩比大,所以在经济性、动力性以及排放性中的降低温室气体排放方面优势显著,因此,柴油机不仅站稳了商用车的主流市场,而且在乘用车市场份额也在增长。然而,柴油机具有氮氧化物和颗粒排放高的缺点,而且两者是一种trade-off的关系,因选择性催化还原后处理系统在降低氮氧化物(NOx)排放方面具有很大的优势,因此成为众多商家满足日益严格排放法规的首选技术手段。然而,由于历史原因,柴油机电子控制系统、还原剂喷射系统大量借鉴和引入国外产品,对整机控制算法、信号协议、核心硬件自主开发不足,造成产品构架、控制策略、信号模式均采用了国外的开发模式,一个系统一个标准,无统一性。而本文是在吉林大学韩汛峰通用型SCR系统自学习控制策略和算法研究的基础上,利用实验室资源对其控制策略和算法进行了优化、改善,并进行了开发性的研究和控制策略功能的实现,引入了闭环控制的PID调节,为通用型SCR系统进一步研究和实现产品化提供了研究思路和基础。本文首先详细介绍了后处理SCR系统的化学反应机理,并把发动机排气中的氮氧化物所有可能发生的反应用化学方程式量化,为通用型SCR系统的设计提供了重要的参考依据,基于SCR系统对尾气中氮氧化物的反应的化学方程式的量化分析,重新设计了通用型SCR系统的储液罐、补液罐、恒压罐,保证了通用型SCR系统应用到实际中的可行性及实用性。详细介绍了新的硬件设备的结构以及工作原理,根据新硬件设备的工作原理开发相应的软件控制程序,实现了对尿素自动供给系统电磁阀和尿素喷嘴的控制,并实时的进行信号的反馈和显示。使得控制得到量化,保证控制的稳定性与准确性。利用飞思卡尔单片机MC9S12XS128开发板以及相应的开发软件Codewarrior,实现了液位、温度、氮氧化物的信号数据的采集以及控制,制定了补液和恒压喷射电磁阀以及喷嘴的控制策略。编写了尿素喷嘴的喷射程序,并在此程序下研究了新一代博世喷嘴在不同喷射压力和喷射频率下的喷射特性,为下面的研究提供了参考依据。通过试验,可以生成氮氧化物的总生成量脉谱和催化转化效率脉谱,绘制了通用型SCR系统的氨氮比脉谱以及还原喷射量脉谱,为确定喷嘴的控制策略奠定了依据。根据PID算法制定了实现尾气中氮氧化物自调节控制的策略,并进行了B50工况进行试验,进行了该控制系统PID参数的整定。利用LabVIEW软件实现了通用型SCR系统计算机软件的开发,进行了LabVIEW与下位机电控单元的通讯试验,验证了该软件通讯功能可行性,使得更直观监测实验数据。
[Abstract]:In the traditional reciprocating piston internal combustion engine, compared with the gasoline engine, because of the large equivalent compression ratio of the diesel engine, the advantages of reducing greenhouse gas emissions in economy, power performance and emission are significant. Diesel engines have not only secured the mainstream market of commercial vehicles, but also increased their market share in passenger vehicles. However, diesel engine has the disadvantage of high NOx and particle emission, and the relationship between them is a kind of trade-off, because the selective catalytic reduction post-treatment system has great advantages in reducing NOx (NOx) emissions. Therefore, it has become the preferred technical means for many businesses to meet the increasingly stringent emission regulations. However, due to historical reasons, the electronic control system of diesel engine and the reducing agent injection system have been widely used for reference and introduced into foreign products. The lack of independent development of the control algorithm, signal protocol and core hardware of the whole engine has resulted in the product structure and control strategy. The signal mode adopts the foreign development mode, one system and one standard, no unity. Based on the study of self-learning control strategy and algorithm of Hanxunfeng SCR system in Jilin University, this paper optimizes and improves the control strategy and algorithm by using laboratory resources. The development research and the realization of the control strategy function are carried out, and the PID regulation of the closed-loop control is introduced, which provides the research idea and foundation for the further research and realization of the general-purpose SCR system. In this paper, the chemical reaction mechanism of reprocessing SCR system is introduced in detail, and all possible reactions of NOx in engine exhaust are quantified by chemical equation, which provides an important reference for the design of general SCR system. Based on the quantitative analysis of the chemical equation of the reaction of nitrogen oxides in tail gas by SCR system, the storage tank, rehydration tank and constant pressure tank of the general SCR system are redesigned, which ensures the feasibility and practicability of the universal SCR system applied in practice. The structure and working principle of the new hardware equipment are introduced in detail. According to the working principle of the new hardware equipment, the corresponding software control program is developed, and the control of the solenoid valve and the urea nozzle in the urea automatic supply system is realized. And real-time signal feedback and display. The control is quantified to ensure the stability and accuracy of the control. The signal data acquisition and control of liquid level, temperature and nitrogen oxide are realized by using Freescale single chip computer MC9S12XS128 development board and the corresponding development software Codewarrior. The control strategy of rehydration and constant pressure injection solenoid valve and nozzle is established. The injection program of urea nozzle was compiled, and the injection characteristics of the new generation Bosch nozzle under different injection pressure and injection frequency were studied under this program, which provides a reference for the following research. The total output pulse spectrum and catalytic conversion efficiency pulse spectrum of nitrogen oxides can be generated by experiments. The ammonia nitrogen specific pulse spectrum and reduction jet pulse spectrum of the universal SCR system are plotted, which lays a foundation for determining the control strategy of the nozzles. According to the PID algorithm, the strategy to realize the control of nitrogen oxides in exhaust gas is established, and the B50 test is carried out, and the PID parameters of the control system are adjusted. The computer software of general SCR system is developed by using LabVIEW software. The communication experiment between LabVIEW and the lower computer electronic control unit is carried out. The feasibility of the communication function of the software is verified, which makes it more intuitive to monitor the experimental data.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK423

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