Novel entrance and exit designs towards fully developed dual Vortexes in cyclone separators

Stairmand-type cyclones are commonly used in industry to separate particles from gas streams by inertia, driven by the dual-vortex flow patterns. Here, new designs are proposed to eliminate the local non-ideal vortex patterns in a conventional Stairmand cyclone by inserting a flow divider at the entrance and adjusting the elbow exit orientation. A two-way coupled CFD–DPM approach is employed to analyze the performance of the modified cyclones. Simulation results show that the cyclone with the elbow exit oriented orthogonal to the entrance direction demonstrates better performance in terms of the cut size and sharpness. The installation of the flow divider reduces the vortex eccentricity by approximately 50%. The flow divider increases the gas velocity near the outer wall, allowing the quasi-free vortex in the cyclone's outer region to become nearly fully developed at the entrance section through the reduction of the local secondary recirculation flows. The optimum flow divider outer wall thickness correlates to the wall shear stress distribution. With the optimum 2 mm outer wall thickness flow divider installed, the separation efficiency for 2 μm particles increases from 56.74% to 77.4%, and the cut size decreases from 1.87 μm to 1.23 μm.