Vaporization of a spinning fuel droplet

The influence of rotation on droplet vaporization is investigated theoretically. A single, spherical liquid fuel droplet, spinning at a constant angular velocity about its own axis is considered. The analysis assumes that the rotational Reynolds number is small and that quasisteady conditions prevail in the gas phase. Thus, the swirling flow field and the accompanying heat transfer process are obtained as modifications of the classical solution of a stationary vaporizing droplet. It is found that the induced secondary flow, inwards towards the droplet poles and outwards from its equator, enhances the vaporization rate and shortens the droplet lifetime. An explicit expression is obtained for the correction to the evaporation rate and consequently a modification to the d²-law is derived. For most practical cases, the dependence of the evaporation rate on the rotational Reynolds number, Re_r, and on the Prandtl number, Pr, is approximately of the form (Re_r)⁴ Pr^7/5. Finally, an explicit expression for the torque exerted on the evaporating droplet compared to that exerted on a solid sphere is derived.