Vortex analysis and flow field optimization for the particle classifier with three rotary cages

[Display omitted] •Turbulent flow in particle classifiers with three rotary cages was investigated using Q criterion.•Formation process and distribution of the vortices were intuitively exhibited.•The unwanted large-scale columnar vortex is eliminated by extending the guide cone.•The optimized guide cone significantly increases the Newton efficiency of the classifier. The particle classifiers with three rotary cages have significant advantage in powder handling capacity. The flow field inside the classifiers were investigated from the perspective of vortex using Q criterion. Formation process and distribution of the vortices were intuitively exhibited. Structure of the guide cone was further optimized, and the classifying performance of the classifiers was evaluated. The results show that complex vortex structures were formed inside the classifier. The large-scale columnar vortex under the guide cone oscillates irregularly. This unwanted vortex is eliminated by extending the guide cone. The structure of the guide cone has little effect on the cut size, but the optimized guide cone with the long cylinder and cone significantly enhances the separation degree of the fine and coarse particles. The classifier obtains finer silica powder with a median size of 2.5 μm and higher Newton efficiency about 71.5%.