传动比对汽车实际行驶排放试验动力学特性与排放的影响

Influence of Transmission Ratio on Dynamic Characteristics and Emissions of Vehicle RDE Test

为研究传动比对轻型车CO_(2)、CO、PN、NO_(x)排放以及动力学参数的影响,选择4辆7挡干式双离合变速器轻型车作为试验车辆在相同道路上进行实际行驶排放(real driving emission,RDE)试验,依据传动比对数据进行划分.结果表明:(1)随着传动比、相对正加速度(relative positive acceleration,RPA)的升高,CO_(2)、CO、NO_(x)排放因子以及未装汽油机颗粒捕集器(gasoline particulate filter,GPF)车辆的PN排放因子均呈增加趋势.其中,CO_(2)、CO、PN(未装GPF)的排放因子与传动比的相关系数平均值分别为0.963、0.933、0.949,与RPA的相关系数平均值分别为0.971、0.955、0.975,均呈显著正线性相关;NO_(x)排放因子与传动比、RPA的相关系数平均值分别为0.567、0.543,相关性均较弱.(2)以传动比作为变量的轻型车排放因子分析方法表明,随着传动比的升高,单位里程中发动机的工作循环与排放次数均增加,CO_(2)与污染物排放因子呈增加趋势,这解释了CO_(2)、CO、PN(未装GPF)、NO_(x)的排放因子均与传动比呈正线性相关的原因.(3)RPA与传动比的相关系数平均值为0.953,二者呈显著正线性相关.v·a_(pos)_[95](车速与大于0.1 m/s^(2)正加速度乘积的第95个百分位)与传动比的相关系数平均值为-0.487,呈负线性相关,且相关性较弱.增加低速挡使用时间,RPA呈升高趋势,v·a_(pos)_[95]呈降低趋势,可远离行程无效判定界限,从而提高RDE试验动力学检验通过几率.研究显示,传动比、RPA与CO_(2)、CO、PN(未装GPF)的排放因子均呈显著相关,借助调节传动比对碳和污染物排放进行控制,为减少汽车实际行驶排放提供了新的途径.

In order to study the influence of transmission ratio on CO_(2),CO,PN,NO_(x)emissions and dynamic parameters,four light-duty vehicles with 7-gear dry dual clutch transmission were selected as test vehicles,and real driving emission tests were carried out on the same road.The data were divided according to the transmission ratio.The results showed that CO_(2),CO,NO_(x)and PN(without gasoline particulate filter,GPF)emission factors tended to increase with the increase of transmission ratio and RPA(relative positive acceleration).Furthermore,the average correlation coefficients of CO_(2),CO and PN(without GPF)emission factors with transmission ratios are 0.963,0.933 and 0.949 respectively,and the average correlation coefficients with RPA are 0.971,0.955 and 0.975 respectively.CO_(2),CO,PN(without GPF)emission factors has a significant positive linear correlation with the transmission ratio and RPA.The average correlation coefficient of NO_(x)emission factor with transmission ratio and RPA is 0.567 and 0.543,respectively,and the correlation is slightly weaker.The number of engine cycles and emissions per unit mile increases with the increase of transmission ratio.The reason for correlation between CO_(2),CO,PN(without GPF),NO_(x)emission factors and transmission ratio can be explained by the analytical method for emission factors of light-duty vehicles using transmission ratio as a variable.RPA has a significant positive linear correlation with the transmission ratio.The average correlation coefficient is 0.953.v·a_(pos)_[95](the 95th percentile of the product of vehicle speed and positive acceleration greater than 0.1 m/s^(2))has a slightly weaker negative linear correlation with the transmission ratio.The average correlation coefficient is-0.487.With the increase of low-speed gear use time,RPA tends to increase and v·a_(pos)_[95]tends to decrease,staying away from the judgment boundary of the invalid trip,which can improve the chance of passing the dynamics test.The study shows that CO_(2),CO and PN(without GPF)emission factors have a significant correlation with the transmission ratio and RPA.The method of controlling carbon and some pollutant emissions by adjusting the transmission ratio provides a new way to reduce real driving emissions.