Study On Real Driving Emission Characteristics Of Light Vehicle

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.