Abstract: Obvious electrostatic effects are commonly found in industrial fluidized bed, which influences the hydrodynamics of fluidized bed and causes security risks constantly.However, the application of external electric field can 'turn harm into benefit'.In order to investigate the hydrodynamics of gas-solids fluidized bed with applied electric field, CFD simulation coupled with the electrostatic model was carried out.Through a decoupling method, the axial electrostatic potentials profiles and particle movements in the fluidized bed were investigated.The simulations presented a Z-shaped axial profile of potential in traditional fluidized bed, which was in good agreement with the experimental data.With the application of direct current (DC) electric field, the simulations showed that the region of positive potential expanded obviously, whilst the region of negative potential was also spread.Under DC electric field, the assembling of small particles was weakened near the wall, but aggregation of small particles appeared near the central electrode.By using AC electric field, the concentration of small particles near the wall was slightly lower than that in the normal fluidized bed.According to the mean electric field distribution produced by charged particles in AC field, it was observed that the electrostatic field had different directions.In the region near the distribution plate, the electrostatic field directed towards the center, while in the region near the bed level, the direction of electrostatic field headed towards the wall.

Key words: gas-solids fluidized bed, CFD, electrostatic, applied electric field

摘要： 工业流化床中通常存在显著的静电效应,会影响流化床的流体力学特性,并常常带来一定的安全隐患,而引入外加电场可以达到"化害为利"的作用。为了获知外加电场下流化床内的流体力学特性,本文采用CFD耦合静电模型及解耦求解的方式,研究了外加电场下气固流化床内的轴向电势分布和颗粒的运动规律。研究结果表明,传统流化床的轴向电势分布呈Z形,与实验结果一致,引入直流电场后,颗粒自身产生的电场正电势区域明显增大,而负电势区域也有小幅增大。直流电场可以使得壁面处小颗粒的聚集减少,但在床中心出现明显的颗粒聚集。在交流电场下,小颗粒在壁面处的分布比正常流化床时的稀疏。通过对颗粒自身产生电场的分析,发现近分布板区和料位区的电场方向不同,近分布板区的电场指向床中心,而料位区的电场指向壁面。

关键词: 气固流化床, 计算流体力学, 静电, 外加电场