Study on Real Driving Emission Characteristics of Light Vehicle

杨超

韩永强

硕士

吉林大学

实际行驶排放;;排放特性;;环境温度;;PM指数;;行程动力学特征

大气污染源解析表明,机动车已经成为重点城市地区空气污染的主要来源,世界主要国家和地区相继加严排放法规来减少机动车所造成的环境污染问题。研究表明,机动车实际道路排放与实验室认证工况排放存在较大差异,为了减少这一差异,车载排放测试技术越来越多的应用于机动车排放测试。欧盟、日本和中国相继在排放标准中引入了实际道路排放测试(RDE)法规。我国于2016年颁布的第六阶段轻型车排放标准中将RDE测试纳入型式核准试验,给出了过渡限值,2022年7月1日前需重新评估。对于国Ⅵ车型RDE测试时的整体排放水平目前无明确结论,不同技术路线车型结果的差异研究也较少,同时国Ⅵ标准规定了行驶动力学边界条件,但有研究表明,同一车辆在不同行程动力学特性满足标准的条件下结果相差达10倍以上,同一辆车不同满足标准要求的测试燃料颗粒物结果差异明显,因此有必要开展实际道路排放系统性研究。本项目对于典型国Ⅵ轻型车系统的开展了实际道路排放测,研究了不同技术路线和行驶特征实际道路排放特性,分别开展油品指数以及驾驶动力学特性对RDE测试结果的专项研究。主要研究成果如下:1.对于典型国Ⅵ标准轻型车开展实际道路排放测试,研究不同喷油方式、后处理系统、行驶特征、道路拥堵情况以及冷起动对实际行驶排放的影响,研究国Ⅵ车型RDE测试整体排放水平。2.调研了国外PM指数预测模型,在5辆试验车辆上采用4种不同PM指数油品开展相应测试,研究了油品PM指数与车辆PM、PN排放相关性,基于测试结果得出了车辆PN排放预测模型;针对燃料中添加乙醇后该模型的适应性进行了试验研究,结果表明该PM指数预测模型也可以用来评估乙醇汽油PN排放。3.在实际道路上开展三种不同驾驶激烈程度RDE测试,研究不同驾驶方式对应行程动力学参数对RDE测试结果影响。结果表明,不同驾驶激烈程度会显著影响RDE测试CO和PN排放,随着驾驶激烈程度增加,CO和PN排放呈升高趋势。行程动力学参数(v*a)k-[95]和RPA反映驾驶激烈程度,通过测试结果拟合得出行程动力学参数与RDE测试排放数学模型,可以用来评估驾驶行为对RDE测试结果影响。4.针对国Ⅴ车型开展实际道路排放测试,研究了国Ⅴ车型RDE测试的污染物排放状况,确定国Ⅴ车型RDE测试应加入NOx排放限值。其次对比了不同数据处理方法对RDE测试结果影响。

The analysis of air pollution sources shows that motor vehicles have become the main source of air pollution in key urban areas.Major countries and regions in the world have successively tightened emission regulations to reduce environmental pollution caused by motor vehicles.Studies have shown that there is a big difference between the actual road emissions of motor vehicles and the emissions from laboratory certification conditions.In order to reduce this difference,on-board emission testing technology is increasingly used in motor vehicle emissions testing.The European Union,Japan and China have successively introduced actual road emission testing(RDE)regulations in their emission standards.In the sixth phase of light vehicle emission standards promulgated by my country in 2016,the RDE test was included in the type approval test,and the transition limit was given.It needs to be reassessed before July 1,2022.There is currently no clear conclusion on the overall emission level of the national VI motor vehicles during the RDE test,and there are few studies on the differences in the results of different technical routes.At the same time,the national VI standards stipulate the boundary conditions of driving dynamics,but studies have shown that the same vehicle runs on different journeys.When the dynamic characteristics meet the standard,the results are different by more than10 times.The results of the test fuel particles that meet the standard requirements of the same car are significantly different,so it is necessary to carry out a systematic study of actual road emissions.This project carried out actual road emission tests for typical national VI light vehicle systems,studied the actual road emission characteristics of different technical routes and driving characteristics,and carried out special tests on the RDE test results of environmental temperature,fuel index and driving dynamics characteristics.The main research results are as follows:1.Carry out the actual road emission test for typical national VI standard light vehicles,study the influence of different fuel injection methods,after-treatment systems,driving characteristics,road congestion and cold start on actual driving emissions,and study the overall emission level of RDE tests of national VI motor vehicles.2.Investigated foreign PM index prediction models,and carried out corresponding tests on 5 test vehicles with 4 different PM index oil products.The correlation between oil PM index and vehicle PM and PN emissions was studied.Based on the test results,the vehicle PN prediction model emissions were obtained.An experimental study on the adaptability of the model after ethanol is added to the fuel,the results show that the PM index prediction model can also be used to evaluate the PN emissions of ethanol gasoline.3.Three RDE tests with different driving intensity levels were carried out on actual roads to study the influence of different driving modes on the RDE test results.The results show that different driving intensity will significantly affect the CO and PN emissions in the RDE test.As the driving intensity increases,CO and PN emissions tend to increase.The travel dynamics parameters(v*a)*k-[95] and RPA reflect the intensity of driving.The mathematical model of travel dynamics parameters and RDE test emissions can be obtained by fitting the test results,which can be used to evaluate the impact of driving behavior on the RDE test results.4.Carry out the actual road emission test for the National V motor vehicles,study the pollutant emission status of the National V model RDE test,and determine that the National V model RDE test should include the NOx emission limit.Secondly,it compared the impact of different data processing methods on the RDE test results,compared the actual road conditions in Beijing and the differences between different certification conditions.