Effects of Wall Roughness on the Flow Field and Vortex Length of Cyclone

Abstract

Cyclone separators are widely used in gas solid separation process. Their dimensions and configurations have a great influence on the performance, and have been widely studied. However, for a long-time used cyclone, the surface roughness may increase due to erosion and solid collision, and also is an important factor regarding the cyclone performance. Unfortunately, the study of roughness has been ignored for a long time. In this paper, the effects of wall roughness on flow field of cyclone are investigated. The three-dimensional flow field is simulated with Reynolds Stress turbulence model using Fluent. The simulation results indicate that wall roughness has a great influence on flow field. The increased roughness leads to a decrease in vortex length, and this reduces the separation efficiency a lot. The tangential velocity also decreased along the axial position, but there is no obvious trend for the axial velocity. However, a lower pressure drop can be achieved when the wall roughness is increased. In conclusion, the increased wall roughness has its pros and cons, on one hand, it leads to lower pressure drop; on the other hand, the separation efficiency is also decreased. For a particular cyclone, there must be a compromise condition between pressure drop and separation efficiency, which is in coincidence with Pareto optimality, and will be studied further.