SECONDARY DROPLET FORMATION DURING BINARY SUSPENSION DROPLET COLLISIONS

Abstract

The outcome of collision dynamics of suspension drops (process fluids) is an interesting and challenging problem in industrial spray applications as e.g. spray drying. As a result of the liquid fragmentation process as well as a result of a binary droplet collision in the spray, fine droplets may be formed at the very low end of the overall droplet size distribution in the spray. The fine particles (dust) during spray drying are considered to be a difficult process to control. One of the main causes is the complex interaction of suspension droplets in the hot air flow and the collision of droplets. An experimental study of binary collisions of suspension droplets in off center collisions (impact parameter of B > 0) is discussed. The aim is to study the collision phenomena and derive dominant physical mechanisms of binary droplet collision of suspensions. Two suspension droplet streams of equal size have been generated by means of piezoelectric droplet generators. The drop velocities of the two streams of suspension drops have been varied systematically to change the Weber number of the collision. A collision map for suspension droplet collisions will be derived. The formation of satellite droplets by suspension droplets collisions is correlated by a function based on the basic parameters and dimensionless numbers of the process. The results support the understanding of the phenomena of binary droplet collision dynamics between droplets from pure fluids and suspensions. Paper ID ILASS08-4-7