柴油轿车NEDC循环的颗粒排放特性

Exhaust Particle Emissions from a Diesel Car under NEDC Cycle

以一台轻型柴油轿车为试验样车,采用颗粒数量及粒径分析仪对轿车NEDC循环的排气颗粒进行测试,研究其排气颗粒数量、粒径分布和几何平均粒径.结果表明:车辆加速阶段,总颗粒数密度增大且出现峰值;车辆减速阶段,总颗粒数密度先出现一个波峰,然后急剧下降,这在EUDC循环最后期的减速区域尤为明显.UDC首个循环单元的初始怠速工况下,核态颗粒数密度高于聚集态颗粒.暖机后的UDC和EUDC循环单元内,等速工况的聚集态颗粒数密度普遍高于核态颗粒.加速阶段,聚集态颗粒和核态颗粒数密度均有所升高.减速阶段,聚集态颗粒数密度降低,但核态颗粒数密度却有所升高且占主导地位,其数量分数大都在80%以上.UDC首个循环单元的单位里程颗粒数量排放最高,其余3个市区循环基本相同,而EUDC循环的单位里程排放颗粒数则明显低于UDC循环.NEDC每个循环单元的颗粒粒径均呈准正态分布,峰值粒径都出现在50～60,nm范围内.整个NEDC循环的颗粒几何平均粒径,最大为怠速工况时的55,nm,最小为减速工况时的37,nm.

Particle number concentration, size distribution and geometric average diameter of a diesel passenger car under the New European Driving Cycle （NEDC）test were studied using an EEPS particle size analyzer. Experimental results show that the total particle number concentration increases and gives a peak value during accelerating condition, while it gives a peak value firstly and then decreases sharply during decelerating condition. The latter is especially obvious during the last decelerating condition in the Extra Urban Driving Cycle （EUDC） unit. The number concentration of nucleation mode particles is higher than accumulation mode particles during initial idle speed condition in the first unit of the Urban Driving Cycle （UDC）.After warm-up, the number concentration of accumulation mode particles is generally higher than nucleation mode particles during constant velocity condition in the EUDC and other three UDC units. Both nucleation and accumulation mode particles ascend when accelerating. The number concentration of nucleation mode particle increases, and dominates the total particle number. Its proportion is over 80% when decelerating. The exhaust particle number of unit distance in the first UDC unit is highest, and there is no obvious difference among the other three UDC units. The exhaust particle number of unit distance in the EUDC unit is obviously lower than that of the UDC units. Particle size distribution in each NEDC unit appears quasi-normal distribution, and the peak value of particle number in each unit ranges from 50 nm to 60 nm in particle diameter. The maximum geometric average particle size is 55 nm when idling, while the minimum is 37 nm when decelerating.