MMT对汽油机催化前后微粒排放的影响

在一台自然吸气式PFI汽油机上,开展了甲基环戊二烯三羰基锰(MMT)汽油添加剂对发动机催化前后微粒数量浓度分布、粒径分布和质量浓度分布影响的试验,并研究了不同MMT含量对催化器催化效率的影响.结果表明,随着汽油添加剂MMT含量的增加,催化前后核态和积聚态的数量浓度均增加,MMT含量为12.5 mg·L-1和17.5 mg·L-1的燃油增加显著,相对于超细微粒,经催化器后细微粒和大微粒降幅比较明显.催化前后核膜态峰值粒径基本不变,催化后的积聚态峰值粒径明显大于催化前.随着MMT含量的增加,催化后积聚态峰值粒径向催化前移动.相比于基础油,随着MMT含量的增加,催化器对总数量浓度的催化效率有所降低,但MMT的增加大幅度提高了催化器对微粒总质量浓度的催化效率.

Effect of gasoline blended with MMT on PM emissions before and after the catalyst for a PFI engine

Particulate matter (PM) emissions from a PFI gasoline engine with the catalysts operating on conventional gasoline fuel were examined and compared with those from the fuel blending with the organometallic antiknock additive methylcyclopentadienyl manganese tricarbonyl (MMT). The conversion efficiency of the three-way catalyst (TWC) on PM was analyzed as well. The results showed that, with the increase of the concentration of MMT, both nucleation mode and accumulation mode concentration of PM increased, especially for the fuel containing 12.5 mg·L^-1 and 17.5 mg·L^-1 of MMT. Compared with ultrafine particle, fine particle and large particle dropped significantly after the three-way catalyst. The number peak particle size remained unchanged for nucleation mode particle after TWC, when the number peak particle size increased significantly for nucleation mode particle after TWC and the number peak particle size moved towards that before catalyst with the increase of the concentration of MMT. Compared with baseline gasoline, increase of the concentration of MMT decreased slightly the number concentration conversion efficiency of TWC, while significantly increased the mass concentration conversion efficiency.