公交车实际道路颗粒物排放的数浓度特征

为获得城市公交实际道路颗粒物数量排放特性,利用车载排放测试系统(PEMS)在实际道路上对公交车颗粒物排放特征及粒径分布进行了研究. 结果表明:公交车车速低于30 km/h的工况占总工况的78.9%,其中车速小于10 km/h的工况所占比例最大,为33.7%；车速高于40 km/h的工况仅占总工况的2.1%. 利用低压荷电捕集器(ELPI)测试的粒径分布表明,公交车进、出站和稳定车速工况下排放的颗粒物数浓度峰值均出现在粒径为70 nm附近；粒径小于70 nm的颗粒物数浓度在3种不同工况下占颗粒物总数浓度的55.4%～69.7%；粒径大于770 nm的颗粒物非常少,其数浓度占颗粒物总数浓度的比例均小于0.1%. 

Study of PM Number Concentration Characteristics of Emissions from a Heavy-Duty Bus on Road

Particle number emissions and particle size distributions from a heavy-duty bus were investigated using a Portable Emission Measurement System (PEMS). The results showed that the bus was operated at a speed lower than 30 km/h over 78.9% of the total operation cycle, in which the speed was lower than 10 km/h for 33.7% of the total. The operation speed was higher than 40 km/h only 2.1% of the time. The particulate matter size distributions were similar at different vehicle speeds, and showed a unimodal peak distribution. The peak concentration of particles occurred at diameter 70 nm. The particulate matter smaller than 70 nm accounted for 55.4%-69.7% of the total number concentration at different modes. There were very few particles with diameter greater than 770 nm; the number concentration occupied <0.1% of the total.