Surface wettability effect on atomization and evaporation of wall-impinging liquid fuel jets in crossflow

The effect of surface wettability on the atomization-evaporation process of wall-impinging liquid fuel jets in crossflow is investigated by detailed numerical simulations of two-phase flows using an Eulerian/Lagrangian framework. The surface wettability is varied with equilibrium contact angles of 30°, 90°, and 150° (three cases) by imposing the contact-angle boundary condition coupled with the dynamic contact angle model, considering the conjugate heat transfer. The results show that for all three cases, the injected fuel forms a liquid film on the impinged wall, and many droplets are stripped out from the liquid film, which increases the gas–liquid interface area and enhances evaporation downstream. Additionally, evaporation from the atomized droplets dominates over that from the liquid column and film because of the larger total interface area and the higher local evaporation rate of the atomized droplets than those of the liquid column and film. Furthermore, heat energy is transferred from the impinged wall with a higher temperature to the liquid film across the contact area, which increases the temperature of the liquid film downstream and enhances evaporation there. With decreasing surface wettability, the liquid film easily detaches from the wall surface upstream, enhancing the atomization. Consequently, the total interface area of the atomized droplets increases with an identical Sauter mean diameter, whereas that of the liquid film decreases, resulting in more active evaporation from the atomized droplets. Additionally, the transferred heat energy decreases owing to the decrease in the contact area, influencing the temperature and evaporation of the liquid film.