固相颗粒在旋流场形成过程中的运动分析
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摘要
通过CFD-DEM耦合计算方法模拟不同粒径颗粒在FX-50水力旋流器内的运动行为,分析旋流器内旋流分离场的形成过程,连续相的运动采用求解平均化的Navier-Stokes方程得到,离散相的运动通过离散元法计算。采用欧拉-拉格朗日方法,通过Freestream曳力模型传递相间数据,分析了流体的速度场、压力场,颗粒群的速度、受力、颗粒-颗粒和颗粒-壁面的接触作用力。结果表明,当循环流与入口流汇合时,颗粒速度损失较大;当旋流场稳定后,60μm粒径颗粒群在旋流器锥段的堆积最严重,分离速度较70μm、80μm颗粒低;颗粒平均速度的变化为先减小再增大,直到以后的稳定变化。旋流场未稳定时颗粒在竖直方向的运移速度大于旋流场稳定后竖直方向的运移速度,80μm颗粒竖直方向平均速度始终大于60μm和70μm。颗粒-颗粒和颗粒-壁面的接触过程中,颗粒的受力以法向方向为主,当颗粒与壁面接触时,所受合力最大;由于流动前期颗粒在旋流器内运动轨迹不稳定,颗粒随机碰撞明显,导致颗粒平均接触力波动较大,当旋流场达到稳定状态以后,数值改变很小。
The CFD-DEM(computational fluid dynamics-discrete element method) coupling calculation method was used to simulate the movement of particles with different particle sizes in the FX-50 hydrocyclone, which analyzed the formation process of the separation field. The continuous phase was obtained by solving the averaged Navier-Stokes equation. The movement of the discrete phase was calculated by the discrete element method. The fluid vlocity and pressure field, particle group velocity,total force, particle-particle and particle-wall contact force was analyzed by Eulerian-Lagrangian method and Freestream drag model. It was shown that the particle velocity loss was relatively large at the confluence of recirculation flow and inlet flow. The particles with diameter of 60μm showed the greatest possibility to accumulate at the cone part of the cyclone and the lowest separation efficiency compared to those particles with diameters of 70μm and 80μm. The variation of the average velocity of the particles experienced the process of decrease first and then increase until its final steady state. The velocity of the particle was larger in the unstable swirl field than that in the stable swirl field vertically. Furthermore, the average vertical speed of particles with 80μm was always greater than that of particles of 60μm and70μm. In the process of particle-particle and particle-wall contact, the force of the particle was mainly in the normal direction. When the particle was in contact with the wall, the force of contact was the maximum. Due to the instability of the particles trajectory in the early transient flow, the random collisions obviously, resulting in a large fluctuation of the average contact force of the particles. While the fluctuation became unconspicuous when the swirl field reached a steady state.
The CFD-DEM(computational fluid dynamics-discrete element method) coupling calculation method was used to simulate the movement of particles with different particle sizes in the FX-50 hydrocyclone, which analyzed the formation process of the separation field. The continuous phase was obtained by solving the averaged Navier-Stokes equation. The movement of the discrete phase was calculated by the discrete element method. The fluid vlocity and pressure field, particle group velocity,total force, particle-particle and particle-wall contact force was analyzed by Eulerian-Lagrangian method and Freestream drag model. It was shown that the particle velocity loss was relatively large at the confluence of recirculation flow and inlet flow. The particles with diameter of 60μm showed the greatest possibility to accumulate at the cone part of the cyclone and the lowest separation efficiency compared to those particles with diameters of 70μm and 80μm. The variation of the average velocity of the particles experienced the process of decrease first and then increase until its final steady state. The velocity of the particle was larger in the unstable swirl field than that in the stable swirl field vertically. Furthermore, the average vertical speed of particles with 80μm was always greater than that of particles of 60μm and70μm. In the process of particle-particle and particle-wall contact, the force of the particle was mainly in the normal direction. When the particle was in contact with the wall, the force of contact was the maximum. Due to the instability of the particles trajectory in the early transient flow, the random collisions obviously, resulting in a large fluctuation of the average contact force of the particles. While the fluctuation became unconspicuous when the swirl field reached a steady state.
引文
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[19]李建明,陈文梅,苏晓东.旋流器排口比对固粒轴向流场的影响[J].化工机械,1995,22(3):132-135.LI J M,CHEN W M,SU X D.Influence of the cone ratio of hydrocyclones on axial velocity fields of solid particles[J].Chemical Engineering&Machinery,1995,22(3):132-135.
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[2]黄思.水力旋流器内油水分离过程的三维数值模拟[J].华南理工大学学报(自然科学版),2006,34(11):25-28.HUANG S.3D numerical simulation of oil water separation in hydrocyclone[J].Journal of South China University of Technology(Natural Science Edition),2006,34(11):25-28.
[3]刘晓敏,檀润华,蒋明虎,等.水力旋流器结构形式及参数关系研究[J].机械设计,2005,22(2):26-29.LIU X M,TAN R H,JIANG M H,et al.Research on structural from and parametric relations of hydrocyclones[J].Journal of Machien Design,2005,22(2):26-29.
[4]苏劲,袁智,侍玉苗,等.水力旋流器细粒分离效率优化与数值模拟[J].机械工程学报,2011,47(20):183-190.SU J,YUAN Z,SHI Y M,et al.Separation efficiency optimization of liquid-solid hydrocyclone and numerical simulation[J].Journal of Mechanical Engineering,2011,47(20):183-190.
[5]张亭,王卫兵,冯静安,等.水力旋流器固液分离效率优化控制仿真[J].计算机仿真,2016,33(8):210-213.ZHANG T,WANG W B,FENG J A,et al.Numerical simulation of the solid-liquid separation flow field in hydrocyclone[J].Computer Simulation,2016,33(8):210-213.
[6]SRIPRIYA R,SURESH N,CHANDRA S,et al.The effect of diameter and height of the inserted rod in a dense medium cyclone to suppress air core[J].Minerals Engineering,2013,42:1-8.
[7]喻黎明,邹小艳,谭弘,等.基于CFD-DEM耦合的水力旋流器水沙运动三维数值模拟[J].农业机械学报,2016,47(1):126-132.YU L M,ZOU X Y,TAN H,et al.3D numerical simulation of water and sediment flow in hydrocyclone based on coupled CFD-DEM[J].Transactions of the Chinese Society for Agricultural Machinery,2016,47(1):126-132.
[8]黄思,杨富翔,宿向辉.运用CFD-DEM耦合模拟计算离心泵内非稳态固液两相流动[J].科技导报,2014,32(27):28-31.HUANG S,YANG F X,SU X H.Unsteady numerical simulation for solid-liquid two-phase flow in centrifugal pump by CFD-DEMcoupling[J].Science&Technology Review,2014,32(27):28-31.
[9]任立波.稠密颗粒两相流的CFD-DEM耦合并行算法及数值模拟[D].济南:山东大学,2015.REN L B.A parallel CFD-DEM coupling model and numerical simulation of dense particulate two-phase flows[D].Jinan:Shandong University,2015.
[10]CHU K W,WANG B,YU A B,et al.CFD-DEM modelling of multiphase flow in dense medium cyclones[J].Powder Technology,2009,193(3):235-247.
[11]CHU K W,KUANG S B,YU A B,et al.Prediction of wear and its effect on the multiphase flow and separation performance of dense medium cyclone[J].Minerals Engineering,2014,56(2):91-101.
[12]唐波.基于颗粒运动行为调控的旋流器分离过程研究及结构设计[D].上海:华东理工大学,2016.TANG B.Numerical study of the separation process and structure design by regulating the flow behavior of particle phase in hydrocyclones[D].Shanghai:East China University of Science and Technology,2016.
[13]喻黎明,谭弘,邹小艳,等.基于CFD-DEM耦合的迷宫流道水沙运动数值模拟[J].农业机械学报,2016,47(8):65-71.YU L M,TAN H,ZOU X Y,et al.Numerical simulation of water and sediment flow in labyrinth channel based on coupled CFD-DEM[J].Transactions of the Chinese Society for Agricultural Machinery,2016,47(8):65-71.
[14]胡国强,等.颗粒系统的离散元素法分析仿真[M].武汉:武汉理工大学出版社,2010:25.HU G Q,et al.Analysis and simulation of granular system by discrete element method using EDEM[M].Wuhan:Wuhan University of Technology Press,2010:25.
[15]孙其诚,王光谦.颗粒物质力学导论[M].北京:科学出版社,2009:16.SUN Q C,WANG G Q.Analysis of the force of particulate matter[M].Beijing:Science Press,2009:16.
[16]QIU L C,WU C Y.A hybrid DEM/CFD approach for solid-liquid flows[J].Journal of Hydrodynamics,Ser.B,2014,26(1):19-25.
[17]TONG Z B,YANG R Y,CHU K W,et al.Numerical study of the effects of particle size and polydispersity on the agglomerate dispersion in a cyclonic flow[J].Chemical Engineering Journal,2010,164(2/3):432-441.
[18]HSIEH K T,RAJAMANI R K.Mathematical model of the hydrocyclone based on physics of fluid flow[J].AIChE Journal,2010,37(5):735-746.
[19]李建明,陈文梅,苏晓东.旋流器排口比对固粒轴向流场的影响[J].化工机械,1995,22(3):132-135.LI J M,CHEN W M,SU X D.Influence of the cone ratio of hydrocyclones on axial velocity fields of solid particles[J].Chemical Engineering&Machinery,1995,22(3):132-135.
[20]NEESSE T,DUECK J.Dynamic modelling of the hydrocyclone[J].Minerals Engineering,2007,20(4):380-386.