Numerical analysis of a burning droplet with internal circulation in a gravitational environment

Abstract

A theoretical analysis of steady burning droplets with internal circulation in the presence of normal atmosphere and gravity is presented. The normalized system governing the gas phase consists of the complete set of conservation equations in r-z coordinates and includes finite-rate global kinetics. For the liquid phase, it includes continuity and momentum conservation equations. Thermodynamic equilibrium is assumed along the gas-liquid interface, which is not stationary. A body-fitted grid generation technique is used to handle irregular boundaries. The parametric study is performed by changing droplet diameter. The induced convection flowfield is presented to demonstrate its interaction with the flame and the liquid flow motion. The predicted results show that there exists one, two, or three cells within the burning droplet, depending on its diameter. The occurrence of an extra cell is due to reverse flow in the gas phase generated by interaction of the induced flow and blowing velocity. Comparison with the case where internal flow is not considered, for a small droplet the effect of internal circulation on mass evaporation rate can be neglected. On the other hand the internal flow will increase the mass evaporation rate.