Impact of high-speed steam-droplet spray on solid surface

A novel technique for the generation of impact by a high-speed steam-droplet spray is proposed. Relatively low-pressure super-purified steam (0.1-0.2 MPa) is mixed with super-purified water in a nozzle, and then sprayed on a solid surface, which is located at approximately 10 mm from the nozzle. This spray is found to cause harsh erosion. The most striking result of this experiment is that the degree of erosion is strongly dependent on temperature; this dependence is hardly explained by the classical droplet impact theory. We recognize the occurrence of a strong focused rarefaction wave in the middle of the droplet; this rarefaction wave may cause cavitation. The existence of cavitation may be supported by the temperature susceptibility of erosion. We experimentally measure both the droplet velocity and diameter distributions by a Phase-Doppler Anemometer. We also numerically study the dynamics of a high-speed liquid droplet impact on a solid surface by solving the Euler equation using the conditions obtained by the experiments. We discuss the possibility of the formation of cavitation bubbles as the primary cause of the experimentally observed harsh erosion on a solid surface.