Comparison of ethanol-, isobutanol-, and 2-methyl-3-buten-2-ol–gasoline sprays from a gasoline direct injector

Abstract

Sprays of alcohol–gasoline fuel blends from a direct-injector were visualized with a high-speed camera utilizing a diffuse back-illuminated imaging technique. Blends of ethanol, isobutanol (2-methyl-1-propanol), and methylbutenol (2-methyl-3-buten-2-ol) with gasoline were injected into an environment representative of engine conditions. Ethanol was blended at 10, 20, and 30% by volume (E10, E20, and E30). Isobutanol and methylbutenol blends were matched to the ethanol blends on an oxygen weight percent basis resulting in blends of 16, 32, and 49% and 18, 37, and 56% by volume for isobutanol and methylbutenol, respectively. Changes in spray behavior were largely driven by changes in vapor pressure. Low-level blends of isobutanol and methylbutenol behaved nearly identically to the neat base gasoline due to their similar vapor pressures. Higher blends of isobutanol and 2-methyl-3-buten-2-ol reduced flash-boiling while ethanol blends increased it. The ambient-to-saturation pressure ratio was found to be sufficient to describe the flash-boiling transitions for all of the fuels. Measurements of spray width were found to become more dependent on ambient density with downstream distance. It was found that blending isobutanol or 2-methyl-3-buten-2-ol into gasoline in lieu of ethanol can result in significant changes to spray behavior depending on the blend level.