Study of the internal flow in a rotary atomizer and its influence on the properties of the resulting spray

Rotary atomizers are often used in spray drying applications because they are able to atomize complex, highly viscous, multicomponent liquids. Spray drying is widely used in the chemical and food industry and is the preferred method of drying many materials such as dairy products, foods, pharmaceuticals, polymers, etc. An important design parameter of spray dryers is the drop size distribution, since it determines the resultant powder size distribution. In this study the evolution of the rivulet thickness of the feed within the inserts of a rotary atomizer is modelled theoretically and compared to numerical and experimental data. Furthermore, the phase Doppler measurement technique has been used to analyse size and velocity of the resulting spray drops. It is shown that the average dimensionless drop diameter, scaled by the jet thickness, correlates very well with the dimensionless stretching parameter. Finally a semi-empirical model for the average diameter of drops in the spray is developed.