Numerical study of airflow regimes and instabilities produced by the swirl generation chamber in counter-current spray dryers

Abstract

[EN] In this work a CFD numerical study is performed to evaluate the influence of the geometry of the swirl generation chamber on the flow behaviour, the swirl intensity and the unstable oscillations in the airflow pattern. The study shows four different regimes for the flow, separated by three critical swirl intensities. The first one is used to identify the formation of the vortex breakdown. The second one makes a distinction between a free and a wall governed vortex. For a free vortex the instabilities ofthe flow pattern decrease when the swirl intensity increases showing a negative power correlation between them. However, in a wall governed vortex the instabilities do not correlate with the swirl intensity, being uncontrollable. The third critical swirl intensity indicates the formation of a backflow region near the walls at the bottom zone of the dryer but without impacting the top cylindrical part of the chamber.