Effect of Alcohol Addition to Gasoline on Soot Distribution Characteristics in Laminar Diffusion Flames

Alcohols are widely used as alternative fuel for spark ignition engines to reduce soot emission. 2D soot distributions of alcohols-gasoline blends were studied in laminar diffusion flames by two-color laser-induced incandescence technique. The soot volume fraction decreases significantly with the alcohol blending ratio. At the same blending ratio, the soot-reducing ability declined with the carbon length of the alcohol, but the reducing effect for short-chain alcohols, i.e., methanol and ethanol, deteriorated at high blending ratio while it remained constant for the long-chain alcohol n-butanol. At fixed oxygen content, the soot-reducing ability of a short-chain alcohol is still higher than that of a long-chain alcohol, i.e., not only the oxygen content but also the molecular structure dominates the soot-reducing ability.