Due to the rapid development of powder technology around the world, powder materials are being widely used in various fields, including metallurgy, the chemical industry, and petroleum. The turbo air classifier, as a powder production equipment, is one of the most important mechanical facilities in the industry today. In order to investigate the production efficiency of ultrafine powder and improve the classification performance in a turbo air classifier, two process parameters were optimized by analyzing the influence of the rotor cage speed and air velocity on the flow field. Numerical simulations using the ANSYS-Fluent Software, as well as material classification experiments, were implemented to verify the optimal process parameters. The simulation results provide many optimal process parameters. Several sets of the optimal process parameters were selected, and the product particle size distribution was used as the inspection index to conduct a material grading experiment. The experimental results demonstrate that the process parameters of the turbo air classifier with better classification efficiency for the products of barite and iron-ore powder were an 1800 rpm rotor cage speed and 8 m/s air inlet velocity. This research study provides theoretical guidance and engineering application value for air classifiers.

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This paper aims to disclose the mechanism of the screw conveyor and detail the particle flow inside this type of conveyor. To this end, the author discussed the relationship between the trajectory angle of particle motion and several key parameters based on the fluid mechanics. Then, a theoretical model of particle flow was established for screw conveyor of sand, considering the lateral sliding efficiency, the fill rate and the theoretical maximum mass flow rate. The theoretical analysis shows that the outlet mass flow rate depends on such parameters as the inclination angle, rotation velocity and pitch. Through several tests, the author obtained the variation patterns of the fill rate with rotation velocities and pitches, and those of the outlet mass flow rate with inclination angles, rotation velocities and pitches. After that, the change law obtained by our theoretical model was contrasted with that observed in Reference. The comparison shows that the two laws are basically the same. Thus, the proposed model is accurate enough to be applied in the practical design of the screw conveyor.

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