【作者】 杨菲；

【导师】 胡广地；

【作者基本信息】 西南交通大学 ， 动力机械及工程， 2017， 硕士

【摘要】 随着国Ⅵ及更高排放法规的颁布和实施,国家对柴油机尾气的排放要求越来越严格。对于国Ⅵ柴油机,优先采用机内净化技术将裸机的(NOx)与(PM)排放严格控制在一定范围内。现有的国Ⅳ/Ⅴ柴油机空气系统仅仅通过调节废气再循环(EGR)与可变截面涡轮增压器(VGT)已很难达到NOx与PM的严格排放要求,因而必须增加进气节气门,从而达到更大的EGR率以满足空燃比的控制要求,并将国Ⅵ柴油机裸机的氮氧化物(NOx)与微粒(PM)排放控制在一定范围内,再配合后处理系统以满足排放法规的要求。柴油机空气系统的优化目标主要是控制两类排放:一是微粒PM;二是氮氧化物NOx。微粒和NOx的生成与进气空气流量率(MAF)和进气增压压力(MAP)直接相关,因此,选择二者作为反馈变量设计输出反馈控制器,以对柴油机的主要排放物PM和NOx进行控制。本文由此展开了如下研究:1)利用GT-POWER建立了带有EGR、VGT和节气门的四缸柴油机模型,并在节气门全开的状态下对模型进行稳态及瞬态验证,结果表明,所建立的GT-POWER模型能准确模拟真实发动机的状态。2)对带有EGR、VGT及节气门的四缸柴油机,选取进气歧管压力、进气中冷器压力、排气歧管压力及涡轮转速作为状态建立了发动机平均值模型,并利用所建立的GT-POWER模型对该平均值模型进行验证,结果表明所搭建的平均值模型在稳态和瞬态下的精度分别达到96%和93%,且大大降低了模型的计算量。3)基于平均值模型设计柴油机空气系统模型预测控制算法,其控制目标是使进气空气流量率(MAF)和进气增压压力(MAP)跟踪目标值,以降低PM和NOx排放。同时为了与模型预测控制对比,文中还设计了基于观测器的状态反馈控制器,其中状态观测器对发动机的不可测状态进气中冷器入口压力进行了状态估计。对比表明,模型预测控制算法具有更高的控制精度及鲁棒性。更多还原

【Abstract】 With the promulgation and implementation of CHINA Ⅵ and higher emission regulations,diesel exhaust emission regulations become stricter and stricter.For the CHINA VI emission regulations,it gives priority to the use of internal cleaning technology to control NOx and PM emissions in a certain range for bare engine.It is difficult to meet the stringent emission requirements of NOx and PM by adjusting exhaust gas recirculation(EGR)and variable geometry turbocharger(VGT)in CHINA Ⅳ/Ⅴ diesel engine air systems.Therefore,the intake throttle must be added so as to achieve higher EGR rate to meet the air-fuel ratio control requirements,and the emission of NOx and PM can be controlled in a certain range.With the aftertreatment technology can meet the requirements of emission regulations.The following studies are carried out in this paper:1)A four cylinder diesel engine model with EGR,VGT and throttle is established in GT-POWER and validating the model in steady and transient state with full intake throttle.The results show that the GT-POWER model can accurately simulate the state of the real engine.2)The intake manifold pressure,intake air intercooler pressure,exhaust manifold pressure and the rotational speed of the turbine are selected to establish a mean-value model of a four cylinder diesel engine with EGR,VGT and throttle.The mean-value model is verified by the GT-POWER model.The results show that the average accuracy of the proposed model is 96%and 93%in steady and transient state respectively,the calculation of the model is also greatly reduced.3)Model predictive control algorithm for diesel engine air system are designed based on mean value model.The control objective is to make the intake air flow rate(MAF)and the intake pressure(MAP)to track the target value to reduce PM and NOx emissions.At the same time,in order to compare with the model predictive control,an observer based state feedback controller is designed,in which the state observer is used to estimate the state of the inlet intercooler pressure.The results show that the model predictive control algorithm has higher control precision and robustness.更多还原