Abstract: Aiming at the problem of the drag force change in turbulent fluidization system of phosphogypsum particles, on the basis of experiments, considering the existence of nonuniform structures which would influence gas-solid drag force, 2D fluidized bed was simulated using the Gidaspow drag model modified by correcting factor φ. By comparing the simulative results of the Gidaspow model under different φ values with the experimental results, the influence of the changing φ on the simulative results and the variation characteristics of drag force in turbulent fluidization system of phosphogypsum particles with different gas velocities were studied. The results showed that particles aggregated obviously along the horizontal direction in the experimental system, which reduced the drag force between gas and solid phase, the Gidaspow model overestimated the drag force and had a poor prediction capacity on the turbulent fluidization characteristics of phosphogypsum particles. The introduction of appropriate φ can significantly improve the simulative accuracy of Gidaspow model on bed expansion, pressure drop and non-uniformity of the system. The simulative results reflected that the smaller the φ value, the smaller the bed expansion, the more heterogeneous the particle concentration distribution in the bed, and the greater the fluctuation of the bed pressure drop were. As the gas velocity increased (0.144~0.240 m/s), the degree of particle aggregation along the horizontal direction intensified and the value of φ decreased nonlinearly (0.31~0.24). The non-uniformity of fluidization system increased with the increase of gas velocity, the particle concentration was higher near the side walls and lower at the center, a large gradient of particle concentration existed along the radial, ring-core structures appear near the walls on both sides, and the symmetry of flow field distribution was poor.

Key words: two-phase flow, fluidization, numerical simulation, drag change, non-uniformity

摘要： 针对磷石膏颗粒湍动流化体系曳力变化的问题，在实验的基础上，考虑非均匀结构对曳力的影响，引入修正因子φ修正Gidaspow曳力模型，对2D流化床进行了数值模拟研究。通过将Gidaspow模型在不同φ值下的模拟结果与实验结果进行对比，研究φ值的改变对模拟结果的影响规律及一定气速范围内磷石膏颗粒湍动流化体系曳力变化特性。结果表明，Gidaspow模型高估了实验体系曳力，对体系流化特性的预测效果较差；适当φ值的引入能明显提高Gidaspow模型对床层膨胀、压降及体系非均匀度的模拟精度。模拟结果反映出φ值越小，床层膨胀高度越低，床内颗粒浓度分布越不均匀，床层压降波动性越大。随着气速的升高(0.144~0.240 m/s)，颗粒沿水平方向上的聚集程度加剧，φ值呈非线性减小(0.31~0.24)。流化体系的非均匀度随着气速增加而增大，颗粒浓度沿径向存在较大梯度，两侧边壁处附近出现环-核结构且流场分布对称性较差。

关键词: 两相流, 流态化, 数值模拟, 曳力变化, 非均匀度