Research On The Flow Field And Separation Characteristics Of The Compact Two-Stage Gas And Liquid Cylindrical Cyclone

The two-stage gas and liquid cylindrical cyclone is intended to be applied to the low gas-liquid ratio slug flow condition and the high gas velocity annular mist flow condition,in order to better cope with the impact of slug and liquid film climbing problem.In this paper,the design points of the two-stage swirl separation mechanism were analyzed,and the basic design theory of the cyclone separator was used to optimize the structural parameters of the separator by means of numerical simulation.Finally,the experimental prototype was processed according to the results of numerical simulation and the experimental platform was set up for experimental exploration.The main contents and conclusions are as follows:The distribution of the flow field and the stability of the swirl were analyzed.The results show that the tangential velocity distribution shows the distribution characteristics of the“Rankine's Vortex”.Correspondingly,the dynamic pressure and the total pressure also appear as the"combined vortex"distribution characteristics,while the static pressure gradually decreases along the radial direction from the wall to the center.As a whole,the axial velocity presents"inverted V"type distribution,but when the diameter of vortex finder increases to a certain extent,the"M"type distribution occurs due to the static pressure recovery.Swirl instability is the inherent property of straight tangential entrance separator,the instability and pressure loss were used as the indexes to evaluate the separation performance.The results show that:The degree of instability of the swirling flow decreases with the increase of the entrance cross section ratio,the decrease of the diameter of the vortex finder and the increase of the depth of the vortex finder.The pressure loss increases with the increase of the inlet cross-sectional ratio,the decrease of the diameter of the riser,the increase of the extender's insertion depth.After consideration,the corresponding structural parameters were determined as follows:K_A=7.85,Dc=90 mm,S=200 mm.With the increase of the gap spacing L,the swirl strength in the vortex finder increases,while the pressure loss of the separator increases.After consideration,L=10 mm was preferred.With the increase of the diameter of the reflow tube,the return flow increases,which is beneficial to the liquid film reflow,but at the same time the swirling strength of the main separation zone decreases.After consideration,d_h=20 mm was preferred.In order to study the applicability of the separator,the Malvern-Insitec on-line laser particle size analyzer was used to measure the particle size of the separator outlet and the liquid content in the gas.The operational envelope of the separator in the corresponding flow pattern was also calibrated.It was found that the droplet size distribution of the separator outlet is significant with the apparent gas velocity in the annular flow pattern,and whether the influence of the particle size distribution with the apparent liquid velocity is mainly or not is affected by the apparent gas velocity.The liquid content in the gas decreases first and then increases with the increase of the apparent gas velocity,which mainly involves the balance between the increase of the swirl intensity and the increase of the droplet breakup.In the range of experiments,when the apparent velocity of gas is between 27 m/s and 29 m/s,the two physical processes are balanced,the gas content is the smallest,and the separator is the most efficient.Under the annular mist flow,the performance of the separator and the mist catcher was tested in the range of the working conditions that could be achieved in the test system,and the operational envelope was calibrated and fitted.It was found that when the apparent velocity of gas is about 32 m/s,the failure point begins to appear.Under the slug flow,the operational envelope of the separator was calibrated and fitted in the range of selected test conditions,and the failure modes of different working points on the curve were studied.It was found that v_sg=12.13 m/s,v_sl=0.12 m/s is the demarcation point.The similarity between the left and right sides is that there are sticky droplets adhere to the wall to escape and the difference is that gas core carrying liquid occurs on the right side of the demarcation point.