The Effect Of Load On The Emission Of Heavy Vehicles With Two Technical Routes

In our study,two vehicles which accorded with the national emission level Ⅵ of heavy vehicles as the research object,study on the emission of national heavy duty vehicle.Tests were performed on a heavy-duty chassis dynamometer,select 0%,25%,50%,75% and 100% vehicle load for different working conditions,run C-WTVC loop.Two cars were treatmented by technical routes of DOC+SCR +DPF+EGR and DOC+SCR +DPF,prior to the test,two vehicles were tested for repetitive emission for determine whether the consistency of the data and the performance of the two models are in line with the experimental requirements,and analysis of the resistance parameters of two prototypes under different loads.In this paper,the nitrogen oxygen analyzer and the CVS full flow dilution sampling system are installed in parallel.The emission data of NOx,HC and CO under different vehicle load conditions were obtained,the quality and quantity of the particles were measured,the NOx emission was analyzed by using nitrogen oxygen analyzer and the emission of NH3 was measured,at the same time,the basic operating parameters of the exhaust gas temperature,NOx emissions,EGR flow rate were collected.Based on the data obtained,the emission law of NOx and particulate matter under heavy load was analyzed,and the emission law of NO,NO2 and NOx of the main components of the N2 O was analyzed.We discussed the influence of vehicle gas and particulate pollutant emission on the load change,and the difference of vehicle emission load under different technical routes.The main contents and conclusions are summarized as follows:(1)Through the study of the influence of the load change on the emission of two types of gas pollutants,the heavy vehicles which accorded national standard VI,HC and CO emissions from heavy duty vehicles were not affected by the two kinds of post-processing techniques.For vehicles without EGR technology,under the condition of ensuring the conversion efficiency of NOx,the emission of NH3 increases with the increase of load in the medium and high load conditions and the NOx emission decreases with the increase of load.(2)Based on the study of NOx emission,it was found that in the C-WTVC cycle experiment,the NOx emissions of heavy duty vehicles with two technical routes were mainly provided by the first half of the cycle.In the first 500 ~ 800 s,NOx emissions accounted for more than 80% of the whole cycle,and this ratio increased with the increase of load.The load changed the operating point of the SCR post-processing by affected the exhaust temperature.The exhaust temperature of vehicles with different technical routes was affected by different loads,the exhaust temperature increased rapidly with the EGR technology,but the fluctuation range of the exhaust temperature with the load was small;the exhaust temperature of the vehicle without the EGR technology rised slowly,but the variation range of exhaust temperature varies with the load.Overall,the vehicle without the EGR technology,the NOx emissions impacted on the change of load sensitive effects were more susceptible to the load change;using EGR technology of the vehicle,the NOx emission load change effect was relatively smal.(3)Based on the study of the original NOx emission,it was found that the original NOx emission had a great influence on the emission of post NOx with the same load condition.SCR did not start to transform efficiently in the first few hundreds of seconds before the start of the cycle,the post NOx is same as original NOx.If the vehicle was not using EGR technology,the emissions of the NOx original machine will increased with the increase of the load.The original NOx emission of the vehicle with EGR technology will increased firstly and then remain stable as the load increases.Under different load conditions,the NOx emissions of two vehicles were mainly affected by the change of exhaust temperature,which was not affected by the variation of NOx emissions.The impact of EGR technology on emissions was also for two aspects of exhaust temperature and exhaust emissions.(4)Further analysed of the NOx,as well as the NO,NO2 and N2 O emission laws were found,the maximum emission values of each component of NOx will increased with the increase of the load,and the extreme discharge was more likely to occur with the increased of the load.The N2 O emission was lower and the NO2 emission was slightly higher for the heavy duty vehicle without using the EGR technology;The emission of NO,NO2 and N2 O decreasesd with the increased of load,and the three were mainly generated in the first half of the cycle,which was consistent with the emission trend of NOx.The vehicles with EGR technology,the N2 O emission was higher,the NO2 emission was very low,and the emission trend of N2 O was consistent with the EGR flow.Among them,NO and NO2 were mainly produced in the first half of the cycle,N2 O was mainly produced in the second half of the cycle.(5)Through the studied of the particle emission law and the change of load,the particulate emissions of vehicles that without EGR technology were mainly concentrated in the beginning and the end of the C-WTVC cycle,and the particulate emission of vehicles with EGR technology was provided by the whole cycle.Compared with the vehicles without EGR technology,the vehicles with EGR had less extreme particle emissions,a steady state in the whole cycle fluctuations,particulate reduced emissions range,relatively stable and has little effect by driving conditions.The vehicles without EGR technology,the particulate emissions decreased gradually with the change of vehicle load.With the EGR technology,the particulate emissions of vehicles decreased and then increased.The reason was that a small amount of EGR flow will make the combustion duration longer and lower the oxidation time of particles.With the increase of the vehicle load,the EGR flow rate increased gradually,which leaded to the decrease of oxygen content in the cylinder,the deterioration of combustion,and the decrease of the temperature in the cylinder.