Evaporation of deformable liquid fuel droplets

Abstract

This work covers the effect of droplet deformation on its evaporation rate under convective flow conditions. A single component jet fuel surrogate n-decane is used as a liquid fuel. The large droplets in sprays tend to deform due to an imbalance of aerodynamic force and surface tension, hence deviate from a spherical shape. This influence of the deformation and planar flow on evaporation is investigated by varying the relevant non-dimensional groups such as Weber number (W e) ranging from 1 − 12 and Reynolds number (Re) ranging from 25 to 120. These numerical studies utilize a numerical framework for interface capturing Direct Numerical Simulation (DNS) for multiphase flows. The framework is built upon an in-house code NGA. A grid-independent study is performed in order to find an accurate and computationally feasible grid for this work.Furthermore, the numerical results are compared against the analytical correlations by Abramzon and Sirignano (Int. Journal of heat and mass transfer, 1989) to validate the accuracy of the solver.The results for grid size N d = 24 are found to be in good agreement with the analytical solution with 5% of difference.Finally, the effect of droplet shape on the evaporation rate at various Re is quantified in terms of total evaporation rate and its contributors: local evaporation rate and the total surface area.Results suggest that the evaporation of the droplet has a weak dependency with Weber number at low Re. However, as the deformation is significant for W e = 4, 8, 12 at Re = 120, it plays a key role in altering the total evaporation rate ( ṁ) by altering the flow around it.