Structural optimization of vortex finder for a centrifugal air classifier

Abstract

To further improve the centrifugal air classifier performance, effects of the fully-inserted vortex finders with slots are investigated. Experimental results show that the classifier with the non-uniform slotted vortex finder has the higher particle selectivity, smaller cut size and narrower product particle size distribution than the classifier with the uniform slotted vortex finder and the base partly-inserted vortex finder. The classifier obtains the particle classifying sharpness of 1.72 when the primary and secondary gas velocities are 12 m/s and 2.4 m/s. The experimental curves present a same distorted S-shape with the fish-hook dip at about 4 μm. Simulation results indicate that the non-uniform slotted vortex finder could accelerate the swirling flow with the gas tangential velocity averagely increased by 3 m/s. The static pressure varies from −350 Pa to 1700 Pa. Meanwhile, the slotted vortex finder can reduce the influence of the short circuit flow on coarse particles. The DPM model can well predict the cut size with a maximum error of 4.9%, but not the fish-hook effect. The obtained results can provide a guideline for the vortex finder design of the centrifugal air classifier.