【作者】 王刚；

【导师】 郭晨海；

【作者基本信息】 江苏大学 ， 动力工程（专业学位）， 2017， 硕士

【摘要】 本文以两辆符合国Ⅵ排放水平的重型车整车为研究对象,开展国Ⅵ重型车整车排放实验研究。实验在重型底盘测功机上进行,选取0%、25%、50%、75%和100%整车载荷为不同工况点,运行C-WTVC循环。两辆样车分别采用DOC+SCR+DPF+EGR和DOC+SCR+DPF的后处理技术路线,实验前首先对两辆样车进行重复性排放验证,确定两辆样车的数据一致性与工况跟踪性是否符合实验要求,并对两辆样车进行不同载荷下的阻力参数分析。将氮氧分析仪与CVS全流稀释采样系统的采样设备并联安装,构建了符合本研究要求的实验系统。实验获得了不同整车载荷工况下的NOx、HC、CO等气体污染物的排放数据,测量了整车颗粒物质量及数量排放情况,利用氮氧分析仪对NOx排放进行了细化分析并对NH3的排放进行了测量,同时采集了排气温度、NOx原机排放、EGR流量等车辆基本运行参数。通过数据处理,分析了国Ⅵ重型车在不同载荷工况下NOx和颗粒物的排放规律,以及NOx主要组成成分NO、NO2和N2O的排放规律。探讨了车辆气体和颗粒污染物排放受载荷变化的影响,以及不同技术路线车辆排放受载荷影响差异性。全文工作内容及所得的主要结论概括如下:(1)通过两辆样车的气体污染物排放受载荷变化的影响研究发现,对于达到国Ⅵ排放标准的重型车整车,两种后处理技术路线重型车的HC和CO排放均不受载荷影响。未采用EGR技术的车辆,其NOx排放会随着载荷的增大而降低;采用EGR技术的车辆,NOx排放会随着载荷的增大先升高后降低。(2)通过对NOx排放规律研究发现,在C-WTVC循环实验中,两种技术路线的重型车,其NOx排放均主要由循环起始前半段提供。在循环前500~800s,NOx排放占整个循环的80%以上,且这一比例会随着载荷的增大而增加。载荷通过影响排气温度,改变后处理SCR催化器工作时间点来影响排放。采用不同技术路线车辆的排气温度受载荷影响不同,采用EGR技术的车辆其排温上升快,但排气温度随载荷变化的波动范围小;未采用EGR技术的车辆其排温上升慢,但排气温度随载荷变化的波动范围大。综合来看,未采用EGR技术的车辆,其NOx排放对载荷变化的影响比较敏感,较易受到载荷变化的影响;采用EGR技术的车辆,其NOx排放受载荷变化影响相对较小。(3)通过对NOx原机排放研究发现,在同载荷工况下,NOx原机排放对后NOx的排放影响较大。在循环起始前几百秒,SCR催化器未开始高效转化,此时原机排放水平将直接影响整个循环的排放水平。未采用EGR技术的车辆,其NOx原机排放随着载荷的增大而升高;采用EGR技术的车辆,其NOx原机排放随着载荷的增大先升高后保持平稳。在不同载荷工况下,两技术路线的车辆,其NOx排放均主要受排气温度变化的影响,不受NOx原机排放随载荷变化趋势的影响。(4)对NOx进一步分析,以及对NO、NO2和N2O的排放规律进行研究发现,两种技术路线的重型车,NOx各组成成分的排放最大值均会随着载荷的增大而升高,随着载荷的增大更容易出现极端排放情况。对于未采用EGR技术的国Ⅵ重型车,其N2O排放量较低,N02排放略高;NO、NO2和N2O的排放都会随着载荷的升高而降低,三者都主要生成于循环的前半段,与NOx总量的排放趋势一致。采用EGR技术的国Ⅵ重型车,其N2O排放量较高,NO2排放量极低,且N2O的排放趋势与EGR流量具有对应一致关系。其中NO和NO2主要产生于循环的前半段,N2O主要产生于循环的后半段。(5)通过对颗粒物排放规律和受载荷变化影响研究发现,未采用EGR技术的车辆其颗粒物排放主要集中在C-WTVC循环开始和末尾位置;采用EGR技术的车辆,其颗粒物排放由整个循环提供。相对于未采用EGR技术的车辆,其颗粒物排放极端情况较少,在整个循环内呈平稳波动状态,颗粒物排放值范围较小,排放比较稳定,受车辆行驶工况影响较小。未采用EGR技术的车辆,其颗粒物排放随着整车载荷的变化呈逐渐下降趋势。采用EGR技术的车辆,其颗粒物排放随着增和的增加先降低后升高。究其原因,低载荷时,少量的EGR流量会使燃烧持续期变长,延长颗粒物的氧化时间。随着整车载荷的增加,EGR流量逐渐增加,会导致气缸内氧含量减少,燃烧情况变差,降低缸内温度,从而降低颗粒物的氧化速率。更多还原

【Abstract】 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.更多还原