The focus of this comparative study was to evaluate the oxidation behavior and related properties of exhaust particulates from dual fuel combustion with various low reactivity fuels. Samples from premixed gasoline, n-butanol and gasoline/n-butanol blends with a fixed substitution of 40% (noted as G40, B40 and G20B20, respectively) were characterized by high-resolution transmission electron microscope (HR-TEM), Raman spectroscopy (RS) and X-ray photoelectron spectroscopy (XPS) and thermogravimetric (TG). TG results showed that the oxidation reactivity of particulates from dual fuel combustion followed the order of G40 > G20B20 > B40, and above particles were more reactive to oxidation than diesel soot. It can be inferred that applying gasoline/diesel dual fuel combustion has beneficial implications for the diesel particulate filter regeneration and even lifetime, in comparison to n-butanol/diesel dual fuel combustion. In comparison to G40 soot, B40 soot exhibited a more ordered nanostructure with longer fringe length but shorter tortuosity from HR-TEM as well as lower ID1/IG and ID3/IG values from RS. Note that the differences in the soot nanostructure between B40 and G20B20 samples were low, and actually the effects of premixed fuels on both soot reactivity and nanostructure were slight. Hence, soot reactivity is only partially structure-controlled. In addition, TEM images showed that soot from premixed butanol had smaller primary particle than premixed gasoline. Particulates from dual fuel combustion exhibited higher C-OH concentrations than diesel soot, but no significant trend can be observed for CO concentrations among various samples. Both primary particle size and oxygenated surface functional groups were not correlated with soot oxidation reactivity.
Keywords: Dual fuel combustion; Gasoline/diesel; Nanostructure; Soot oxidation reactivity; Surface functional groups; n-butanol/diesel.
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