Study of China In-use Vehicle Emission Test Methods

Author:Liu Jia

Supervisor:huang ying


Degree Year:2017





With the rapid development of automobile industry and the rise of the number of automobiles,the management of vehicle emission in China faces new challenges and problems.Controlling vehicle emissions could be realized by raising emissions standards and reducing new vehicles emissions,and the in-use vehicles emissions should not be neglected.Effective test methods of in-use vehicles emissions are necessary conditions to recognize high emissions vehicles and to take timely measures.This study was based on the China’s existing system of in-use vehicle emissions management,combined the provincial testing results,which put forward suggestions for amendments of in-use vehicle testing standards.Meanwhile,according to the characteristics of vehicle technology and application in China,and present situation of air pollution in major cities,the suggestions of additional test items methods were proposed to meet urban air pollution control requirements.The statistics of ASM and VMAS test results showed that for vehicles whose emissions were lower than the emission standardⅠ,the detected standard-exceeding rates of VMAS were slightly higher than ASM.With the emission standard improved,the detected standard-exceeding rates of two method decreased by degrees,and were roughly the same.There was a high degree of consistency of ASM5025 and ASM2540.When using only one detection test,the test method ASM5025 should have the first right of refusal,in order to improve the detection efficiency.The VSP stability range of the actual road test by use of remote sensing method was[-5,14],which had the same width as US EPA standard([3,22]).But for China the actual road vehicles covered more vehicles,and broadened the scope of application of remote sensing.For different emission standards vehicles and the emissions,the VSP stability range varied.With the increase of emission levels,the stability range broadened.For the current remote sensing measurement standards,two improved schemes were proposed.The first scheme,for all vehicles to be inspected,the new VSP range was adopted([-5,14]).This Scheme does not need to change the remote sensing devices,and has strong applicability.The second scheme,the differentiation interval of VSP ranges were adopted to meet the different emission standards vehicles and emissions.The advantage of this method is to improve the effectiveness of the emissions test data.Base on the real driving emission test method,the in-use vehicle emissions management could be strengthened under real road conditions.Compared with the test results under laboratory conditions,the emissions of CO and NO_x of gasoline vehicles were out of limits under real road conditions.The Current regulations did not require the particulate matter emission tests of gasoline vehicles with PFI engines,however,the PN of partial gasoline vehicles with PFI engines exceeded under real road conditions.The NO_x emission of diesel vehicles under real road conditions seemed quite different to the laboratory conditions.The application of OBD system of light-and heavy-duty vehicles was investigated by a large number of field research.The results showed that it can be considered that our country has been qualified for carrying out vehicle emission test by use of OBD diagnosis.Comparative tests were carried out between OBD diagnosis and new vehicle emission certification mode for 210 vehicles which met Chinese emission regulationⅢandⅤ.The results showed that the number of the same test results by use of the two mode was 174,accounting for 82.8 percent of the total.Consequently,OBD diagnosis can basically reflect the level of in-use vehicle emissions and can be used as an important means of in-use vehicle emissions test.Based on the reality of high NO_x emissions of diesel vehicles in our country,the addition of NO_x emission limit values of heavy-duty diesel vehicles was proposed.The test results of vehicle and diesel engine bench showed that the existing diesel vehicles loaded deceleration measurement conditions was suitable to carry out NO_x emission test for vehicles.The comprehensive study of NO_x emission test data of diesel engine emissions certification,load deceleration detection field and actual road heavy-duty diesel vehicle emissions showed that it is reasonable that the limit value of the NO_x emission of diesel vehicles which met Chinese emission regulationⅣwas set to 800-1000ppm.The test method and evaluation system of the effect of emission control of diesel vehicles after the DPF modification were proposed.The results of the reconstruction are evaluated by efficiency coefficient method.It is no need to establish limit values for the pollutants indexes respectively,which facilitates testing and evaluation.