关键词: 计算流体力学-离散单元法, 水力旋流器, 计算流体力学, 离散单元法, 欧拉-拉格朗日, Freestream曳力模型

Abstract:

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 and 70μm. 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.

Key words: CFD-DEM, hydrocyclone, computational fluid dynamics, discrete element method, Eulerian-Lagrangian, Freestream drag model