DYNAMICS AND HEAT TRANSFER ANALYSIS OF DROPLET IMPACT ON HIGH TEMPERATURE SPHERICAL SURFACE

Leidenfrost phenomenon is a physical phenomenon caused by droplet impact on high-temperature wall surface, which is widely used in electronic engineering, mechanical engineering, power engineering, chemical engineering and other fields. However, most of the existing research focus on the Leidenfrost phenomenon on a plane, and few studies have focused on high-temperature curved surfaces, such as spheres. In order to investigate the dynamic characteristics and heat transfer characteristics of droplet impact on a high-temperature sphere, numerical simulation methods were used to study the Leidenfrost phenomenon caused by droplet impact on the hot sphere. The Leidenfrost phenomenon was analyzed from the aspects of droplet and gas film morphology, wall heat flux and pressure distribution. The interaction between droplets, gas film, and hot spherical surface was studied. It was found that the wall heat flux is higher when the gas film thickness is thinner, and the Poiseuille flow will be formed when the vapor between the droplet and the wall is discharged, thus affecting the exhaust speed. The article further studied the influence of factors such as droplet impact velocity, droplet size, wall temperature. The results indicate that both impact velocity and droplet size can enhance droplet spreading and heat transfer, but there are differences in the changes of the gas film. An increase in impact velocity leads to accelerated exhaust and a decrease in the thickness of the central gas film. The increase in droplet size will lead to an increase in the thickness of the central gas film. Because the initial droplet impact kinetic energy has no change, the change in wall temperature has little effect on the droplet spreading situation. However, the increase of the wall temperature will increase the heat absorption of the droplet and accelerate the evaporation rate, resulting in an increase in the thickness of the center gas film.