CFD simulation and parameter optimization of the internal flow field of a disturbed air cyclone centrifugal classifier

Abstract

In the present study, a new disturbance structure is designed to improve the performance of classification air cyclones. To this end, numerical simulations and experiments are carried out to analyze the flow field inside the disturbance structure. It is found that the perturbation structure has a great effect on the velocity and pressure distributions, properties of gas and particles, and the classification performance of the cyclonic air centrifugal classifier. The obtained results show that the pressure and velocity profile in different radial sections has W-shaped and Rankin distributions, respectively. The outer layer is quasi vortex-free, while the inner layer is quasi forced vortex, and the forced vortex is the dominant force field that affects the classification performance. The critical speed of the perturbation structure to reach a uniform stability of the graded flow field is 1500 rpm. When the particle motion path is completed and the trajectory of different particle sizes is regular, the helix angle of the gas flow trajectory is 28°, the gas flow has low speed and high density, the effective graded flow field occupies more space, and the vortex flow field is strong, uniform, and stable. It is found that any speed other than the critical speed (1500 rpm) affects the uniformity and stability of the airflow. The obtained results show that for a rotational speed of 1500 rpm, a feed speed of 0.3 kg/s, and an inclination angle of 4°, macroscopic and microscopic classification efficiencies exceed 91 %. The order of significant effects between parameters was determined as Rf > v > β, and the correlation model between classification index and parameter factors was established. This article is expected to provide a reference to study the influence of internal flow field and classification performance of large-scale industrial air classifiers.