环境温度对缸内直喷汽油车颗粒物排放特性的影响

Effect of Ambient Temperature on Particulate Emission Characteristics of GDI Passenger Car

利用电子低压冲击仪(ELPI)对一台满足国Ⅴ排放标准的缸内直喷汽油车进行了颗粒物排放特性研究。试验按照NEDC测试循环在转鼓试验台上进行,分别测量车辆在-15℃,-7℃和25℃下的颗粒物排放。通过对试验结果的研究表明:3个温度下,颗粒物的数量浓度随温度的下降大幅上升,粒径分布范围逐渐变大,均在相同粒径下出现峰值;颗粒物体积浓度随粒径的增大而增大;数量浓度对表面积浓度的影响大于体积浓度,尤其在-15℃下,这种影响更加显著。通过对颗粒物的瞬态排放结果的分析发现:3个温度下,颗粒物的排放主要集中在NEDC循环前200s,数量浓度随车辆的加速而上升,随减速而下降;在-15℃下,在整个NEDC循环的加速工况均出现表面积浓度的排放峰值,且峰值之间较为接近。

Particulate emission characteristics of China-Ⅴ gasoline direct injection passenger car were measured by ELPI.On the test bench of chassis dynamometer,the particulate emissions at-15 ℃,-7 ℃ and 25 ℃ were measured respectively.The results show that the particulate numbers greatly increase with the decrease of temperature and the particle size distribution extends.In addition,the particulate numbers under three temperatures reach the peak in the same particle size.The volume fraction of particle increases with the increase of particle size.The effect of particulate number on surface fraction is larger than that of volume fraction,which is more significant at-15 ℃.Through analyzing the transient particulate emission,it is found that the exhaust particles mainly discharge during the first 200 sof NEDC and the number concentration increases with vehicle acceleration and decreases with vehicle deceleration.At-15℃,the surface fraction reaches the peak in acceleration conditions of whole NEDC test cycle and the peaks at three temperatures are fairly close.