Numerical analysis on the effect of the length of arc-shaped vortex finder on the hydrocyclone's flow field and separation performance

Because of the short-circuit flow, coarse particles may be carried in overflow when using a conventional hydrocyclone, which seriously affects the separation precision. Many scholars found that using arc-shaped vortex finder can effectively reduce short-circuit flow rate, however, the effect of arc segment length on the hydrocyclone's separation performance has rarely been investigated. For this reason, this study employed computational fluid dynamics (CFD) for numerical simulation on the 050 mm hydrocyclones with different lengths of arcshaped vortex finders. The pressure field, the velocity field, the turbulent intensity and the separation efficiency of each hydrocyclone were examined in depth. Then the simulation results were compared with classical experimental data by Hsieh for effectiveness validation. Results show that both tangential velocity and pressure drop first increased and then dropped with the increasing arc length, both of which reached the maximum at an arc length of 30 mm; greater pressure drop and tangential velocity promoted the separation of particles. The axial velocity in the hydrocyclone with arc-shaped vortex finder was lower than that in a conventional hydrocyclone, accordingly, particles stayed in the hydrocyclone with arc-shaped vortex finder for a longer time, resulting in more thorough separation. Additionally, as the arc length increased, both the split ratio and the short-circuit flow rate dropped, which lowered the number of misplaced particles. In the arc-shaped vortex finder, particles moved smoothly, accompanied with the decline in collision probability among particles. The turbulent intensity dropped with the increasing arc length so as to make the flow field more stable. Finally, as the arc length increased, the cutting dimension first dropped and then increased, while the steepness index first increased and then dropped. At an arc length of 30 mm, the cutting dimension dropped to the minimum and the separation precision was highest. Conclusively, the 050 mm hydrocyclone including the vortex finder with an arc length of 30 mm can manufacture fine and high-quality products.

Automated summary

The use of an arc-shaped vortex finder in a hydrocyclone can effectively reduce short-circuit flow and improve particle separation. Increasing the arc length led to a rise and then a drop in tangential velocity and pressure drop, with the most efficient separation achieved at an arc length of 30 mm.