Three dimensionally coupled computational fluid dynamics (CFD) and discrete element method (DEM) were used to investigate the flow of corn-shaped particles in a cylindrical spouted bed with a conical base. The particle motion was modeled by the DEM, and the gas motion by the k-ε two-equation turbulent model. A two-way coupling numerical iterative scheme was used to incorporate the effects of gas-particle interactions in terms of momentum exchange. The corn-shaped particles were constructed by a multisphere method. Drag force, contact force, Saffman lift force, Magnus lift force, and gravitational force acting on each individual particle were considered in establishing the mathematical modeling. Calculations were carried out in a cylindrical spouted bed with an inside diameter of 200 mm, a height of 700 mm, and a conical base of 60 . Comparison of simulations with experiments showed the availability of the multi-sphere method in simulating spouting action with corn-shaped particles, but it depended strongly on the number and the arrangement of the spherical elements. Gas-solid flow patterns, pressure drop, particle velocity and particle concentration at various spouting gas velocity were discussed. The results showed that particle velocity reaches a maximum at the axis and then decreases gradually along the radial direction in the whole bed. Particle concentration increases along the radial direction in the spout region but decreases in the fountain region, while it is nearly constant in the annulus region. Increasing spouting gas velocity leads to larger pressure drop, remarkably increased speed of particle moving upward or downward, but decreased particle concentration.
Bing RenWenqi ZhongYu ChenXi ChenBaosheng JinZhulin YuanYong Lu
Discrete element method(DEM)was developed to simulate the corn-shaped particles flow in the hopper.The corn-shaped particle was described by four overlapping spheres.Contact force and gravity force were considered when establishing the model.In addition,flowing characteristic of particles in the hopper was studied.The effect of friction coefficient on the wall pressure,voidage and velocity distribution was analyzed.The results show that the discharge rate decreases with the friction coefficient increasing;and the"over-pressure"phenomenon occurs in the discharging process for two different friction coefficients.The voidage also increases as the friction coefficient increasing.And the velocity distribution is more uniformity and is closer to the mass flow with the friction coefficient deceasing.
