On the Leidenfrost effect of water droplet impacting on superalloy plate surface

Abstract

The boiling of liquid water on the superalloy surface is important in applications such as steam and gas turbines, for which it is necessary to explore the mechanisms of the Leidenfrost phenomenon. The molecular dynamics simulation method provides an effective way to study this phenomenon at the nanoscale. Previous studies, however, have not revealed the Leidenfrost effect of liquid molecules on a superalloy surface. This work investigated the effects of surface temperature and impact velocity on the nanoscale Leidenfrost phenomenon of water droplet over the Fe-Cr superalloy plate. When the surface temperature is higher than 798 K, the Leidenfrost phenomenon occurs on the superalloy surface with apparent temperature, stress, and pressure differences. The results indicate that the Leidenfrost phenomenon is related to the high surface temperature, rather than its impacting velocity. Furthermore, it is found that the Leidenfrost phenomenon is the combined results from the temperature and pressure differences exist in the vapor film, as enough kinetic energy can be generated by the thermal motion to cause the bounce phenomenon of droplet. The revealed mechanisms are critical for the design of a gas turbine, in which vapor film could be dominant in determining the film cooling effectiveness of gas/vapor on the blade surface.