Mechanism of Particle Collection in a Cylindrical Cyclone Separator (1st Report, Validation of Large Eddy Simulation and Investigation on Detailed Flow Structures)

Abstract

A cyclone separator separates particles by using centrifugal force that acts on the particles in a swirl flow and the separated particles finally fall to the bottom part of the separator by the gravity force. For a gas cyclone separator, the Reynolds number of the bulk flow is typically in the order of 104 to 105, and complicated vortical structures are generated. The particle behaviors in such vortical flows have not yet been fully understood. The final goal of the present study is to clarify the mechanism of particle separation in a cyclone separator and to improve the separation efficiency. To achieve this goal, the unsteady flow in cyclone separators is firstly computed by large-eddy simulation. The computed flow velocities will then be fed to the subsequent analysis of particle tracking. This first report describes results of validations for the large-eddy simulation, where we compared the computed velocity profiles with the experimental data. We also compared the precession frequency of the vortex rope with that reported in the literature. Regarding the vortical structures in the cyclone separator, we identified longitudinal vortices which are generated in the periphery of the large vortex rope. These vortices have one end attached to the inner wall and their strength is stronger than the longitudinal vortices in the boundary layer on the wall. The identified vortices are most likely to play an important role in the particle separation, which will be proven in the second report that describes particle motion in the cyclone separator.