Article: Xu, YH; Avedisian, CT; (2015) “Combustion of n-Butanol, Gasoline, and n-Butanol/Gasoline Mixture Droplets”, Energy & Fuels, 29 (5):3467-3475
Abstract: Fuels derived from biofeedstocks are receiving attention for their potential as additives to conventional petroleum-based transportation fuels. Normal butanol, in particular, can enhance performance compared to ethanol because of its higher energy density. To better understand the combustion dynamics of n-butanol in the context of gasoline, experiments are reported here to examine the isolated droplet combustion characteristics of an 87 octane (ethanol-free) gasoline and a mixture of gasoline (0.9, v/v) and n-butanol (0.1, v/v, B10), along with n-butanol.
The experiments are performed in an ambience that minimizes convection and promotes spherical droplet flames. The initial droplet diameters range from 0.52 to 0.63 mm, and the experiments are carried out in room-temperature air at normal atmospheric pressure. Measurements of the evolution Of the droplet diameter show that butanol and B10 droplets have burning rates that are almost identical to gasoline, even though other features of the burning process, such as soot formation and the relative position of the droplet and flame, are quite different. With butanol mixed with gasoline, the mixture flames are comparatively closer to the droplet than for gasoline droplets. A scale analysis is developed that expresses the droplet burning rate in terms of temperature-dependent properties. The results support the experimentally observed similarity of burning rates for butanol, gasoline, and their mixtures, even though soot formation is neglected.
Funding Acknowledgement: National Aeronautics and Space Administration (NASA) [NNX08AI51G].
Funding Text: This work was supported by the National Aeronautics and Space Administration (NASA) under Grant NNX08AI51G with Michael Hicks as the Project Monitor. The authors also thank Zain Ali of Cornell and Prof. Yu-Cheng Liu of the University of Michigan Flint for discussions and assistance with some of the experiments. The assistance by Zain All with some of the data analyses is also appreciated. The authors also appreciate the interest of Drs. Forman Williams, Ben Shaw, Fred Dryer, and Tanvir Farouk in the work on droplet combustion.