Numerical analysis of effects of puffing on evaporation characteristics of bi-component droplet

This study investigates the puffing-induced secondary atomization and evaporation behavior of a bi-component droplet composed of miscible species (n-heptane and n-hexadecane) using three-dimensional numerical simulations. The gas–liquid interface is captured using the coupled level-set and volume of fluid (CLSVOF) method, and evaporation of two components is modeled based on a non-ideal vapor–liquid equilibrium (VLE) formulation. The simulation consists of two stages: a stationary stage to establish initial thermal and concentration fields assuming a quiescent droplet, and a puffing stage where a vapor bubble of n-heptane is initially embedded within the droplet. The results qualitatively reproduce the fundamental dynamics of puffing droplets, including bubble growth, burst, vapor ejection, ligament formation, and its fragmentation as reported in previous experimental and numerical studies. The analysis reveals a strong dependence of the evaporation behavior on the embedded bubble positioning. While n-heptane shows a sharp decline in evaporation rate after bubble bursts, evaporation rate of n-hexadecane exhibits a transient enhancement owing to rapid redistribution over the droplet surface. Furthermore, placing the bubble deeper inside the droplet leads to stronger puffing and sustains fuel, especially n-heptane, evaporation, highlighting the critical role of internal distribution of species and bubble positioning in bi-component droplet evaporation under puffing conditions.