Experimental and CFD study on a cyclonic classifier with new flow pattern

Abstract

Physical principle of conventional top-inlet classifier (CTC) with reverse-flow pattern leads to the heavily fine particles entrainment in coarse fraction. Present work concentrates on the flow-field design for less downward airflow at near-wall region of the classifier. A new middle-inlet classifier (NMC) is proposed and analyzed using computational fluid dynamics (CFD) method and powder classification experiments. The results showed that new flow pattern characterized by a pair of vortexes was created in the new classifier. The upper vortex with 80% of the total air volume moves upward and forms the washing effect at near-wall region, which effectively reduces the fine particles entrainment in coarse fraction. The downer vortex with reverse-flow pattern discharges the coarse particles timely. The radial centrifugal sedimentation combined with the axial counter-current washing effect dominates the particle classification in the NMC. Compared to the CTC, classification accuracy index of the NMC with double-vortex averagely increases by 27% with a pressure drop reduction of more than 38%. This work offers a new principle for high-efficiency particle classification and new strategy for improving the classification performance of turbo air classifiers and hydrocyclones.