Numerical Study On Gas-Liquid Cyclone Separator Using CFD-PBM Method

The gas-liquid cyclone separator has the advantages of simple structure,high processing capacity,and high separation efficiency,and is widely used in fields such as petrochemical industry,energy conservation,and environmental protection.However,due to the complex flow mechanism of gas-liquid two-phase flow in the separator,liquid droplet aggregation and breakage lead to continuously changing droplet size distribution,forming a complex and polydisperse multiphase system,which causes great difficulties in predicting the separation performance of the separator.To address this challenge,this study aims to construct a CFD-PBM mathematical model that considers the variation of droplet size,to numerically simulate the flow and separation behavior of gasliquid two-phase flow in a tubular cyclone separator.The research methodology is as follows: Firstly,a CFD model of the separator was constructed to investigate the flow characteristics of gas-liquid two-phase flow.Based on this,the Eulerian film model was coupled to calculate the formation and flow of the liquid film.Secondly,the CFD and PBM models will be combined to investigate the aggregation and breakage behavior of liquid droplets,as well as the influence of the evolution of droplet size distribution on the separation performance.Finally,building on the previous research mentioned above,this study investigates the effects of geometric parameters and operational conditions on the separation performance of the separator.Specific research contents and conclusions are as follows:(1)Adopting the Eulerian multiphase flow model,the influence of drag force and surface tension was considered.The turbulent model selected for this study is the RNG k-ε model,which is more suitable for the operating conditions involved in this thesis.Introducing the EWF model,the influence of liquid film flow on the flow field was fully considered.By the constructed CFD model,the two-phase flow field of GLCC was simulated.Analyzed the gas phase velocity,pressure distribution,and liquid volume distribution.Studied the formation and flow of the liquid film,as well as the characteristics of the film thickness and velocity distribution.The research provides certain reference value for improving the mathematical model of GLCC.(2)On the basis of the CFD model for gas-liquid two-phase flow,the PBM was incorporated to describe the aggregation and breakage behaviors of liquid droplets,as well as the effect of the resulting change in droplet size distribution on the two-phase flow field.By using the liquid droplet size group source term,the agglomeration and breakage characteristics can be determined.In the size range of 1 to 7.36 μm,the liquid droplets mainly experienced aggregation.Liquid droplets with a diameter of 8.52～14.79 μm were found to be more prone to breakage behavior.The probability of droplet aggregation and breakage is closely related to droplet concentration and size distribution.The research content is of great significance for improving the separation efficiency of the separator.(3)The effect of geometric parameters and operating conditions on the flow characteristics and separation efficiency was studied based on the previous research.Analyzed the effects of different inlet crosssectional sizes and cylinder diameters on the gas phase velocity,liquid droplet size distribution,and separation efficiency.The research findings can provide certain theoretical support for optimizing operating conditions and the rational design of the structure of the separator.