Study on Structure Optimization and Flow Field Characteristics of A Two-stage Tandem Hydrocyclone

Author:Tan Fang

Supervisor:jiang ming hu


Degree Year:2017





The application of hydrocyclone separation in oil-water separation field is in the process of deepening,owing to its advantages of less cover an area of occupation,high efficiency,low cost and pollution-free.Separation is incompletion,the structure parameters are the key factors restricting the separation performance.Further improvement on the separation efficiency of cyclone is rather difficult once a certain maximum optimization is achieved.The hydrocyclone separator is highly sensitive to the fine oil droplet size,the operating parameters(inlet flow rate and split ratio mainly)and pulsatile inlet flow.To solve these problems,focusing on the optimization design of the tandem hydrocyclone and the flow field characteristics analysis,the fluid-structure optimization design of the tandem cyclone separator is carried out,the effects of breakage and coalescence of oil droplets,pulsating flow rate and fluctuating oil phase concentration on the separation performance were discussed as well.The structure of the second-stage hydrocyclone with spiral entrance is designed,and the length of second-stage hydrocyclone is optimized by the dimension optimization method.Based on the mesh deformation principle of Fluent,the optimum structure parameters of the hydrocyclone are determined by using the shape optimization method with the separation efficiency as a single objective function,and the maximum separation efficiency is achieved.Based on the time averaged Navier-Stokes equation,used the Reynold Stress turbulence model and mixture multiphase model,the flow regularity of the deoil separator,the first-stage hydrocyclone and tandem hydrocyclone is simulated comprehensively.Base on ANSYS Workbench design explorer module,aimed at the separation efficiency and pressure drop as the multi-objective function,used the multi-objective optimization method,furthered improvement on the structure of the first-stage hydrocyclone.Without increasing pressure drop,ameliorated the separation performance of first-stage hydrocyclone,broke through the limitation of hydrocyclone structure optimization,achieved the efficiency and pressure balance values.The optimum operation parameters of the first-stage hydrocyclone are established by using the multi-parameter and multi-objective optimization algorithm.It is demonstrated by experiments that the separation performance of hydrocyclone is real and reliable.The separation performance of the tandem separator was evaluated on the basis of the separation efficiency,the pressure drop,the oil particle size and the operation parameters,analyzed the flow characteristics of the cyclone series,the PIV experiment confirmed the speed of simulation and experimental values have the same distribution,experimental verification of the separation performance of tandem separator by oil-water separation error in 5%.The basic characteristics of swirl separation as well as the influence factors of oil breaking and polymerization is summarized.By using Fluent PBM model,the distribution law of oil droplet size,the distribution law of oil droplet number density,the influence of fragmentation and polymerization on the separation performance of oil droplets in tandem flow field were determined.It provides a theoretical reference for the analysis of factors affecting the separation performance of the tandem hydrocyclone.The characteristics of flow field under pulsating flow are discussed,and the influence of pulsating flow rate and volume fraction of pulsating oil phase on the separation performance is quantitatively analyzed.Together with high separation performance and good adaptability to oil droplet size as well as operation parameters,two-stage tandem separator after optimized design achieves the design expectation.