Impact characteristics of high-temperature alumina droplets on a cold wall: Rebound and adhesion

Abstract

The adhesion and rebound characteristics of alumina droplets in solid rocket motors are important for accurate prediction of slag deposition. This paper develops an experimental system for high-temperature alumina droplets impacting the wall. The system uses induction furnace to melt the alumina and use argon to squeeze the liquid alumina to obtain high-temperature alumina droplets. The particle diameter of the alumina droplets is 0.2 mm ∼ 6 mm, which can be used to explore the impact characteristics of the alumina drop on the cold wall. The experimental system is used to carry out the droplet impact experiments on the tungsten wall at different temperatures, and the droplet temperature is obtained by the two-color pyrometer. The studies show that the contact line stops moving during spreading when the small micron droplets adhere; while the larger droplets adhere, the contact line stops moving during retracting. When alumina droplets impact with the wall vertically then rebound, two sharp corners will be formed near the contact line. When they impact with the wall obliquely then rebound, the primary sharp corner and the secondary sharp corner will be formed gradually. The regime map of adhesion and rebound is obtained, and it is found that the condensation effect will dominate the adhesion stage when the impact energy of the droplet is small.