Study Of Simulations And Measurements Of Flow Field In A Turbo Air Classifier

In the powder industry classification is one of the most important basic operation, which makes the particle size suit to the demand of powder product. With the rapid development of materials science, strict requirements are proposed for the preparation of powder, such as lower limits on diameter size, narrower standard deviations on size distributions, and the like. As the third-generation dynamic air classification equipment, turbo air classifier has high classification precision and good classification performance. It has been widely utilized in different fields, such as in the materials, chemical industry, mineral processing, pharmaceuticals, foods, and so on. Flow field in the turbo air classifier is complex and its distributions determine the particle movement trajectory. In this study, simulations and measurements were carried out to investigate the flow field characteristics in turbo air classifier.Simulations of flow field characteristics were performed by the software of Fluent and measurements of air flow between blades of rotor cage of turbo air classifier were also carried out, the flow field simulation results match the results of measurements. The study indicates that: when the inlet velocity is settled, there is a vortex near the impeller blade when rotary speed is low and the vortex's orientation is accordant to rotor cage, there will be a counter-rotating vortex between blades when rotary speed is too high and the vortex's orientation is contrary with rotor cage. So when the inlet velocity settles, there must be a critical rotation speed to make the flow field between the blades stablest, the intensity of vortex is correlative to rotation speed of rotor cage and would weaken along with the rotation speed approaching the critical rotation speed.The structure improvement of rotor cage of turbo air classifier were done and the air flow between blades can be optimized by changing the setting angle and shape of blades. Compared with conventional classifier, air flow in New-structure1 is more symmetrical, the intensity of vortex is decreased especially when the rotary speed is high. The New-structure rotor cage is favorable for particle dispersion before separation and its classification performances excelled conventional turbo air classifier.