Mixed Convective Droplet Combustion with Internal Circulation

Abstract

The combustion of a fuel droplet in a mixed convective environment once the initial transient heating of the droplet has been completed is analyzed considering the internal motion of the liquid. The coupled gas and liquid phase analyses are solved simultaneously by a series expansion approach in terms of the polar angle. A previously developed mixed convection formulation is used to provide solutions ranging from the forced to the free convective limit. Detailed results are presented for the forced convective combustion of a hexadecane droplet in a standard atmosphere. The pure evaporation of the hexadecane droplet is presented as a particular case of the analysis. The effect on the local mass burning and droplet regression rates of the liquid motion and mixed flow intensities is presented in terms of the parameters that represent the respective processes. It is shown that the internal circulation of the liquid has only a moderate influence in enhancing the evaporation rate of the droplet. A single explicit expression for the droplet regression rate is applicable to the whole range of mixed flow intensity.