The effect of ethanol and iso-butanol blends on polycyclic aromatic hydrocarbon (PAH) emissions from PFI and GDI vehicles

Özet

This study assessed particulate emissions characteristics from two flexible fuel vehicles (FFVs) equipped withport fuel injection (PFI) and gasoline direct injection (GDI) engines. Emissions testing was conducted over theFederal Test Procedure on E10, E51, and E83, and an iso-butanol blend (iBut55). The results showed significantly higher particulate matter (PM) emissions for the GDI-FFV compared to those of the PFI-FFV. Theaddition of alcohol blends resulted in PM reductions for the GDI-FFV, while PM emissions gradually increasedwith higher alcohol blending for the PFI-FFV. Elemental carbon (EC) emissions dominated the PM compositionfor the GDI-FFV, whereas the organic carbon (OC) fraction was higher for the PFI-FFV. The most prominentpolycyclic aromatic hydrocarbons (PAHs) in the vapor-phase were the two- and three-ring aromatic compounds,followed by the middle molecular weight PAHs (four-ring compounds). For the particle-phase PAHs, the middleand high molecular weight PAHs were the most abundant compounds, especially for the GDI-FFV. Overall, theGDI-FFV exhibited markedly higher PAH emissions compared to the PFI-FFV. Both vapor- and particle-phasePAH emissions showed reductions with higher ethanol and iso-butanol fueling for both vehicles, except for thePFI-FFV, where particle-phase PAHs increased and trended similarly with the PM mass and OC for this vehicle.Alcohol blending reduced the carcinogenic potential of the exhaust emissions for both vehicles. The GDI exhaustshowed significantly higher metal emissions than the PFI-FFV. The use of higher alcohol blends led to reductionsin metal emissions, including redox-active transition metals and other metals originating from the lubricant oil.