缸内直喷汽油机排放PM_(2.5)的理化特征及影响因素

通过发动机台架实验研究了发动机的转速、负荷对缸内直喷(GDI)汽油机排放PM_(2.5)的排放水平、化学组成及颗粒物数浓度等的影响.结果表明:GDI汽油机排放PM_(2.5),OC,EC的排放因子分别为(49.8±28.2),(21.6±6.9),(11.4±10.8)mg/kg.低转速时,PM_(2.5)排放量随着负荷的增加先减少后增加,中、高转速时随着负荷的增加逐渐增加.碳质气溶胶是GDI汽油机排放的PM_(2.5)的主要组成成分,有机物(OM)和元素碳(EC)分别占PM_(2.5)的45.6%~70.6%和7.9%~42.7%.PM_(2.5)数浓度呈核态(10nmDp30nm)和积聚态(30nmDp200nm)的双峰分布,数浓度排放量比进气道喷射(PFI)汽油机高2个数量级,不同转速下积聚态颗粒数浓度随着负荷的增加而增加.

Physical and chemical characteristics of PM2.5 emissions from gasoline direct injection engine and its influence factors

This paper investigated the effect of engine speed and load on the emission factors, characteristics of chemical composition and size distribution of the PM_2.5 from a GDI engine. Results demonstrated that the emission factors of PM_2.5, OC and EC were(49.8±28.2), (21.6±6.9), (11.4±10.8)mg/kg. At low engine speed, with the increase of engine load, PM_2.5 firstly decreased and then gradually increased. While it showed an increasing trend with the increase of load in media and high engine speed. The major components of PM_2.5 produced from GDI engine were organic matters and element carbons, respectively, accounting for 45.6%~70.6% and 7.9%~42.7%. Particles from GDI engine were bimodal distribution including nucleation mode (10nm< Dp< 30nm) and accumulation mode (30nm< Dp< 200nm). The number concentration of GDI engine was two orders of magnitude higher than that of port fuel injection (PFI) engine. At different engine speeds, accumulation mode particles increased as the load increased.