【作者】 王凤滨；

【导师】 乔维高； 高俊华；

【作者基本信息】 武汉理工大学 ， 车辆工程， 2009， 硕士

【摘要】 重型柴油发动机占发动机的总比例逐年增大,应用范围越来越广泛。目前对于重型柴油发动机的排放测试主要是发动机的台架测试方法,而根据其测试原理的不同可分为全流稀释采样系统和部分流稀释采样系统。本课题是根据GB17691—2005和ISO16183—2002的规定对两套测试系统进行发动机的排放测试,并对排放结果进行相关性分析。通过分析两种不同测量方法的测试原理,分析结果差异,对两套设备的相关性做出评价。试验主要包括两大部分,一是发动机的工作参数对各排放物比排放的影响,包括中冷后温度、排气背压、进气温度和进气湿度。一是采样系统参数对PM采样的影响,部分流PM采样系统包括经过滤纸的稀释排气流量G_tot、采样比r、稀释通道温度、传送管温度和稀释空气温度;全流系统包括CVS的流量Q_CVS、经过滤纸的稀释排气质量流量G_TOT和二级稀释空气的质量流量G_sec。研究分析了发动机工作参数和采样系统参数对测试结果的影响。在结果分析过程中,采用基于偏最小二乘法（PLS）的数学理论方法对各排放物进行建模,对影响参数进行量化的直观分析,以试图寻找一种研究不同测试系统相关差异性的简便方法。试验研究及分析表明,随着中冷后温度的升高,NOx的排放一直增大,PM比排放先降低后增大;而CO和HC的比排放随着中冷温度的升高一直降低。随着背压的增大,除了HC外,各排放物的比排放呈增大趋势。随着进气温度的升高,CO和HC的比排放降低,而NOx和PM得比排放呈增大的趋势。随着进气湿度的增大,CO、HC和PM的值增大,NOx的比排放降低。对部分流PM采样系统的各参数研究表明,除了经过滤纸的稀释排气流量G_tot和采样比r外,其余各参数对PM的影响很小,比排放结果几乎没有什么变化。其中,G_tot增加会导致PM的比排放增大,而r增大会导致PM的比排放减小。本课题研究的全流系统的各参数值增大,PM的比排放都有增加的趋势。通过PLS的数学理论及方法对各排放物的比排放进行了建模,建立了以比排放值为因变量,以各研究参数为自变量的函数关系式。通过分析回归系数与先前的试验结果,结合实际比排放值和模拟比排放值的相对偏差认为模型的建立是成功的。随后,对全流和部分流的PM模型进行了比对分析研究,认为在发动机工作参数设定一致的情况下,理论上可以满足法规中规定的同一发动机同一台架同时使用不同测试系统测试偏差在5%以下的要求。但是随后对气体比排放值的模拟发现,除了NOx的相对偏差在10%左右外,CO和HC的模拟值与实际值的偏差最大在30%左右,认为是由于多种误差造成的,并建议通过采用实际全流气态污染物的比排放模型等措施加以改进。由于本课题是对两不同试验室采用不同测试原理的台架系统进行的试验测试研究,由于试验室不同导致不确定性因素增多,以试验研究测试结果为基础的相关差异性研究对未来试验室的评估和改进试验室的缺陷,提高测试水平具有一定的指导意义。更多还原

【Abstract】 The proportion of Heavy-duty diesel engine used vehicles in the country has been increasing year by year. At present, for heavy-duty diesel engine emissions testing is mainly the engine bench testing methods, which can be divided into Full-flow dilution sampling system (FFDSS) and Partial-flow of the dilution sampling system (PFDSS) according to the different testing principles.The emission experiments based on GB17691-2005 and ISO16183-2002 are made in both of the two methods, the correlation between test results are analyzed in this paper in order to assess the performance of the two testing cells. The principles of the two testing system and the difference of the results are also analyzed in this paper. The tests mainly include two parts, one is engine operating parameters, including the temperature of the air at the outlet of the intake intercooler, exhaust back pressure, intake air temperature and intake air humidity; the other is sampling system parameters of the PM. For the Partial-flow system, which includes the dilution exhaust flow rate through the filter, sampling ratio, the temperature of dilution channel, the temperature of transmission tube and the temperature of dilution air. The Full-flow system contains the CVS volume flow rate, the flow through the filter and secondary dilution air mass flow. Subsequently, with the purpose of analyzing the impact of the parameters in depth, the partial least squares (PLS) is used in the specific emission. Then emissions models about the mathematical theory are made, trying to find a simple method to assess the correlation of different test systems in theory method.Experimental research shows that, with the temperature of the air at the outlet of the intake intercooler increase, NO_x has been increasing; the PM lower than the first, and then increased after; while CO and HC decreased all the time. As the back pressure increases, the values of all emissions are larger than before in addition to HC. With the increase of intake air temperature, CO and HC emissions decreased, while the specific emissions of NO_x and PM increase. With the increase of inlet humidity, the CO, HC and PM values increase, but the NO_x is in contrary trend.To the parameters of PM sampling system for PFDSS, most parameters have a little impact on the PM in addition to dilution exhaust flow rate through the filter and sampling ratio. For the FFDSS, the specific results increase with the increasing of all parameters, particularly, the CVS volume flow rate and secondary dilution air mass flow have a significant impact on the PM specific results.The models on the specific emission results are made based on the PLS mathematical theory. The models indicate the relationship among the studying parameters. Compared the regression coefficients with previous experimental results, combined with the relative deviation of actual value and the simulation value proved that the models are successful.Subsequently, when the engine operating parameters are set in the same circumstances both of benches, the compared are made between the FFDSS PM model and the PFDSS PM model. The results show that it is possible to meet the test regulation under the deviation of 5% or less range. But to the value of the gas simulation specific emissions, in addition to NO_x relative deviation is about 10%, the maximum deviation of simulated values and the actual value of CO, and HC is 30% which is due to a variety of measure error and calculative error.As the engine is tested during the two different laboratories in different testing principle in this article, which leads the uncertainty factors appeared for this test. This article could help to improve the engine testing level between different laboratories in future.更多还原