Characteristics of high-speed mist generated by condensation of water vapor in pressurized air

The application of droplets has been extensively discussed and explored for decades. The cleaning effect, which is based on the typical application of droplets, requires small droplets and high droplet velocities to improve cleaning efficiency. In this study, a high-speed mist-generating device was developed based on the condensation of water vapor in pressurized air. It can stably produce high-speed mist with nanoscale droplets. Several experiments were conducted to determine mist characteristics. The cleaning effect was validated by cleaning process indicators, which proved that the mist can clean the surface within 10 s. The temperature and pressure distributions were measured. Then, the mist velocity in the range of 35–49 mm along the x-direction was estimated to be 52–65 m s⁻¹ at 35 mm and 40–51 m s⁻¹ at 49 mm. The mist at the nozzle exit was determined to be a supersonic flow based on the Schlieren visualization. Moreover, electric current was detected on the aluminum plate, which was set downstream. The current decreases with an increase in the distance from the nozzle exit and increases with an increase in the inlet gas pressure.