Effect of ambient gas composition on butanol droplet vaporization in turbulent High-pressure environments

• Evaporation of butanol droplets studied in N 2 , O 2 , CO 2 , and their mixtures. • Butanol droplet evaporation follows the classical d 2 -law in all cases. • CO 2 suppresses evaporation more than N 2 and O 2 under all conditions. • Butanol droplet evaporation rate nears the heavier component in a binary gas mixture. • Ambient turbulence and pressure reduce droplet evaporation sensitivity to gas composition. The present work systematically investigated how ambient conditions influence the evaporation characteristics of butanol droplets. Experiments were conducted in a spherical chamber capable of generating isotropic, homogeneous turbulence with negligible mean flow, using four pairs of axial fans to generate turbulence intensity up to 3.0 m/s. The investigation involved varying ambient pressure, up to 10 bar, and gas compositions, including pure and binary mixtures of N 2 , O 2 , and CO 2 , all at room temperature. Single butanol droplets of 500 µm in diameter were delicately positioned in the center of the chamber onto the intersection of two or four micro-fibers and observed throughout the evaporation process using a high-speed camera with precise magnification. Results demonstrated that the normalized squared diameter of the droplets exhibited a linear decline with time, consistent with the classical d 2 -law. More importantly, the evaporation rate was found to be highly sensitive to ambient gas composition under stagnant conditions, with C O 2 reducing the evaporation rate by 26 % compared to N 2 , while O 2 caused only a slight decrease. However the presence of a turbulent flow field with intensities up to 3.0 m/s reduced these disparities by nearly half. In binary gas mixtures, the evaporation rate was found to be intermediate between those of the corresponding pure gases, with a tendency to follow the characteristics of the heavier component. It was found that the presence of turbulence and elevated pressure reduced the effect of ambient gas by diminishing the role of molecular diffusion. The effectiveness of turbulence increased with both pressure and turbulence intensity and was more pronounced in heavier ambient gases.