Numerical Simulation And Experiment Of Cyclones With Fresh Air

Cyclone separator is high-efficiency multiphase separation equipment.It is widely used in industry because of its advantages of simple structure,stable separation efficiency,no moving parts and easy to maintain.Due to secondary flows in the cyclone separator,such as longitudinal circulation,precession vortex core and short circuit flow,its separating efficiency for particles within 5μm is not satisfactory.As a result,lots of researchers aim to solve this issue with the approach of flow control.This study put forward an idea that using fresh air to control the flow field inside the cyclone separator.Two cyclones（Type C and Type D）with fresh air are designed.Separation efficiency as well as its mechanism is investigated by experiments and Computational Fluid Dynamics（CFD）simulation.Research contents and conclusions are listed as follows.CFD simulation of standard PV cyclone reveals that upper dust ring,short circuit flow and longitudinal circulation bring negative impact on the separating efficiency.Therefore,it is necessary to introduce fresh air into the cyclone separator in order to control its flow field,remove the upper dust ring and short circuit flow.CFD simulation of cylindrical vortex chamber reveals that the variation of fresh air’s velocity and inlet position could control the flow field.As a control method of vortex flow,the function of fresh air on vortex chamber also provides ideas for the design of cyclone separators.CFD simulation of cyclones with fresh air indicates that the high-velocity fresh air from the 180°symmetry inlet can increase the tangential velocity,improve the asymmetry of three-dimensional flow field,lower the short circuit flow rate and decrease the concentration and range of upper dust ring.The high-velocity fresh air from the top plate inlet can also increase the tangential velocity and suppress the upper dust ring.Therefore,cyclones with fresh air possess have better separation performance compared to the conventional PV cyclone.Experimental result of two standard cyclones（Type A and Type B）and two cyclones with fresh air（Type C and Type D）shows that their separation efficiency have an order as E>D>B>A.d_c50 of the four cyclones are respectively 0.645μm,0.58μm,0.55μm and 0.48μm.The order of pressure drop is C≈B>A=D when the total flow rate is constant.Under the experimental conditions,top plate fresh air inlet model（Type D）has the biggest collection efficiency and smallest pressure drop,which harvest the ideal effect to raise the efficiency and reduce the pressure drop.