Numerical Simulation and PIV Study of the Turbulent Flow in a Cyclonic Separator

Abstract

The cyclonic separator, as a kind of gas-solid separate device, has been successfully used in industry field for century years. The investigators did much work over the separating theory and the movement of the solid particles to improve the structure of separator in the past years. In recent years, as the advanced test instruments appeared and the numerical simulation developed more reliably, the study of the turbulent flow and separate theory in the cyclonic separator entry a new stage. Some recent researches show that the vortex core bends to and rotates around the wall of separator, forming the ring-shaped pattern normally observed at the vortex end which is called PVC (processing vortex core). The PVC could rewind up the solid particles which have been separated by the separator, and influence the separating ability of the cyclonic separator. In this paper, the large eddy simulation (LES) and the particle image velocimetry (PIV) technique are used to study the flow field, especially the PVC phenomenon, in the cyclonic separator of a circulating fluidized bed (CFB) boiler. Through the numerical simulation, firstly the velocity fields in the cyclonic separator, especially the tangential velocity field as Rankine vortex, are gotten. Secondly the phenomenon of vortex end sticking to the wall of separator is found. The frequency of the PVC is gotten. Thirdly we find that because the core of the vortex inclines and bends to the wall of separator, there is a component of eddy vector which is perpendicular to the longitudinal profile of the cyclonic separator. So there is a vortex in this profile. In PIV test, the velocity in longitudinal profile of the cyclonic separator is measured. The time-averaged and instantaneous velocity fields are gotten. The time-averaged velocity fields overlap with the tendency of velocity fields which were gotten by Linden. And the instantaneous velocity fields are mutual corroboration with the results of numerical simulation.