Flow pattern in reverse-flow centrifugal separators

Experimental flow patterns, determined by Laser Doppler Anemometry (LDA) for two types of reverse-flow centrifugal separators, are presented. The flow patterns in (a) a conventional cylinder-on-cone cyclone with tangential inlet and (b) a swirl tube with vane-generated swirl and a cylindrical body are compared. The experimental data are also used to test the validity of the flow assumptions of some widely used cyclone separation models for each of the two devices. The measured flow patterns are also compared with the results of computational fluid dynamics (CFD) simulations wherever this was helpful for the interpretation. Although the data globally support the standard flow assumptions, some features were quite surprising; for instance, it appears that the surface delimiting the central region of upward flow is largely determined by the diameter of the body and not that of the vortex finder. The similarities and differences between the flow patterns in cyclones and swirl tubes are discussed, as is the suitability of using cyclone separation models for the prediction of swirl tube performance.