Collision regimes and dynamic behaviors of a viscous droplet impacting on a spherical particle at high temperatures

Understanding droplet–particle collision behaviors is essential for the pyrohydrolysis process of pickling liquor, where the pickling liquor is sprayed and dried into particles. This study systematically investigated the collision characteristics between a viscous droplet and a heated stainless steel particle whose temperature ranged from 100 to 700 °C. The results indicate that the vapor thrust promotes droplet rebound in smaller spreading diameters but induces disintegration in larger spreading diameters under the film boiling regime. The collision regime map is summarized, and the transition thresholds of collision patterns are significantly increased with increasing liquid viscosity. The spreading factor and contact line velocity are strongly affected by the particle temperature at high liquid viscosities. In addition, the hydrophobic nature of particle surface in film boiling regime is favorable for droplet spreading. The dynamic contact angle significantly depends on the particle temperature and droplet properties. The dimensionless contact time shows a power law dependency on the Weber number in the rebound pattern, but it is almost a constant in the disintegration pattern.