Study On Test Methods Of Heavy-duty Vehicles Emission

In recent years,the issue of environmental pollution has become increasingly prominent,and the emission of motor vehicles,especially heavy-duty vehicles,as an important source of air pollution,has gradually attracted the attention of the production enterprises and environmental regulatory authorities.All along,heavy-duty vehicles,as the main body of road transport in China,its emission levels are based on engines emission test and indirectly determinated,and the lack of the related emission standards and testing technology requirements for HDV,resulting in the failure to properly regulate the discharge of HDV.With the tightening of emission standards,at present,the national six-stage standard newly added two test methods based on complete-vehicles emission of on-board method and chassis dynamometer method.In this paper,the latest emission test standards,the consistency of different PEMS devices research and the study of on-board method and chassis dynamometer method emissions test comparative are respectively carried out.It is instructive for the correct assessment of the emission levels of HDV and the implementation of the national six-stage standard.This paper firstly verify the consistency of different PEMS devices.Four different types of PEMS devices and CVS devices of full-flow diluted car exhaust analyzer were used to test the emission of a HDV.Among them,the CVS device was used as a benchmark for the measurement of gaseous pollutants in PEMS devices and the PN emissions test results were compared among the four devices.In this paper,on-board method and chassis dynamometer method were respectively used to test the emissions of two HDV that meet the European sixth emission standards.（1）Different types of PEMS devices show good test repeatability and consistency of measurement results for higher concentrations of CO₂ and NO_x emissions,whereas for lower concentration CO emissions measurement,poor consistenc y measurement results and the test repeatability.（2）Under different test conditions,the PEMS equipment has a large difference between the test results of PN,and the test repeatability and the measurement result have poor consistency.（3）Emissions test results using on-board method and chassis dynamometer method for vehicles are shown that the engine running conditions of the road test cover a wide range and the test methods have a wide range of applicability to the vehicle.（4）Under the two test methods,the proportion of running hours of vehicles in urban areas,suburbs and high-speed operating conditions basically meets the requirements of the sixth national standard for the travel time al ocation of prototype vehicle.（5）NO_x emission test results show that under steady-state conditions,the vehicle hasthe highest contribution to NO_x emission.under urban conditions,both on-board method and chassis dynamometer method.Under transient conditions,the vehicle’s NO_x emissions are mainly concentrated on accelerated conditions...