Effect of particle self-rotation on separation efficiency in mini-hydrocyclones

High-speed particle self-rotation near the wall of a hydrocyclone that causes the radial migration of the particles has been extensively investigated. However, the influence of this radial migration on the separation efficiency of the hydrocyclone remains unclear. Since this influence cannot be easily experimentally verified, we employed computational fluid dynamics to investigate the effect of particle rotation on the separation efficiency of a mini-hydrocyclone. A Reynolds stress model and discrete phase model were used to model the flow field and particle migration within the hydrocyclone. Considering the shear flow field and wall collision causing the rotation of particles, the movement trajectory, rotation velocity, and radial migration characteristics of particles entering from different inlet positions in a mini-hydrocyclone were studied. For the numerical simulation, the actual particle size distribution was considered. The results demonstrated that the particles rotated at a high velocity near the wall; the spiral-orbit radius of rotating particles was smaller than non-rotating particles; and high-speed rotating particles migrated from the wall to the central axis of the hydrocyclone. By including particle rotation into the hydrocyclone simulations, the simulated separation efficiency was consistent with experimental results. Further, the accuracy of the rotating particle simulation was 65% higher than the non-rotating particle simulation. Therefore, particle rotation is crucial for simulating the mini-hydrocyclone performance.