THE BURNING CHARACTERISTICS OF N-BUTANOL, GASOLINE, AND N-BUTANOL GASOLINE MIXTURE DROPLETS
Normal butanol has received extensive attention as a promising additive to reduce the consumption of conventional petroleum-based fuels and extend their supplies. The advantages of n-butanol reside in its higher cetane number, lower vapor pressure, and higher miscibility compared to ethanol. This study compares the burning characteristics of butanol to gasoline and a mixture of butanol and gasoline from the perspective of an isolated droplet burning with near-spherical symmetry. Data are reported that compares the isolated droplet combustion characteristics of butanol, an 87-octane (ethanol-free) gasoline, and a mixture of gasoline (90 vol%) and butanol (10 vol%). Spherical symmetry is promoted by carrying out the experiments under free-fall conditions in which the test droplet (in a sealed container of the standard atmosphere) is ignited and its burning history recorded by digital video cameras onboard the free-fall package. The results show that butanol and gasoline have burning rates that are almost identical even though soot formation is observed for gasoline and virtually no soot is formed during combustion of butanol droplets. And gasoline droplet flames are farther from the droplet than butanol droplet flames. The results suggest that butanol may be an attractive additive to gasoline with minimal degradation of performance through blending.