Comparative Study On The Flow Field And Gas-liquid Separation Performance Of Two Types Of Swirl Tubes

The swirl tube with guide vanes is a kind of centrifugal separation equipment widely used in the process of heterogeneous separation.Differing from the cyclone separator with a tangential inlet,it is with an axial inlet and rotates gas by guide vanes.According to the flow direction of gas,it can be divided into two types:the reverse-flow swirl tube(RST)and the uni-flow swirl tube(UST).Currently,gas phase flow field and separation performance have been paid attention for two types of swirl tubes.However,the size of these swirl tubes studied is different and little information can be found about the comparative study of their performance as gas-liquid separator.In this paper,a RST and UST with the same size are designed.The gas phase flow field and gas-liquid separation performance are compared by using experimental and numerical simulation methods.The results shows that the tangential velocity of RST attenuates significantly by 30%along the axial direaction and is generally lower than that of UST.However,that of UST keeps steady.The tangential velocity of RST is lower than UST in most areas.There are downstream outer vortex and upstream inner vortex in RST but the latter does not exist in UST.There are lip leakage and local vortex nearby the end of gas outlet tube in RST and gas flowing up in the collection gap of UST.For the water droplets with a median diameter of 4?m,the separation efficiency of UST is 38-80%and that of RST is 39-89%under different structures and working conditions.When the inlet gas velocity is 2-8 m/s,the gas-liqiud separation efficiency of RST is slightly higher than that of UST by 2-5%.When the inlet gas velocity is 8-15 m/s,the gas-liqiud separation efficiency of UST is higher than that of RST by 7-16%.The rotating water ring exists in RST when the inlet gas velocity is higer than 8m/s and the inlet droplet concentration exceeds 10g/m~3.This phenomenon can be attributed to the end of vortex and results in the efficiency reduction of RST at high inlet gas velocity.The separation efficiency of both RST and UST is affected by the droplet behaviors.Droplets aggregate when the inlet gas velocity is lower than 5 m/s and break up when the inlet velocity is higer than 8 m/s.Droplets break up severely in RST.The separation efficiency of RST and UST for gas-DOS separation is higher than that of gas-water separation.Reducing the exit angle of guide vanes improves the separation efficiency of both,the applicable angle of RST is28°,and that of UST is 35°.The pressure drop of RST is higher than RST at the same inlet gas velocity because of the inter vortex of RST.The average resistance coefficient of UST is 73.4%of RST.