Experimental investigation of the effect of droplet size on the vaporization of butanol in turbulent environments at elevated pressure

Abstract

This paper presents an experimental study of the effect of droplet size on the vaporization rate of butanol fuel under turbulent flow conditions at elevated pressure and room temperature. The butanol droplet is suspended at the intersection of two micro-fibers in the center of a spherical vessel. The initial size of the butanol droplet is varied in the range between 300 and 700 μm. A controlled turbulent flow field, characterized by quasi-zero mean velocity and turbulence intensity of up to 1.5 m/s, was generated by eight axial fans. The findings reveal an improvement in the vaporization rate of butanol droplet as the droplet size increases. This improvement is more pronounced under conditions of elevated pressure and turbulence intensity. The results show that turbulence begins to influence the vaporization process when the droplet diameter exceeds the Kolmogorov length scale. Butanol droplet vaporization rate is found to lie between heptane and decane, leaning towards decane under all explored test conditions. The results reveal that the vaporization rate of hydrocarbon fuels is more sensitive to the droplet size variations than butanol. Turbulence is found to exert greater impact on the vaporization of fuels that have lower gas-phase mass diffusivity and higher thermal diffusivity. Finally, the previously proposed correlations, expressed in terms of Damköhler and turbulent Reynolds numbers, are assessed and found capable of predicting the vaporization of butanol droplet over a wide range size.