Abstract:

The behavior of non-sphere particles in a gas-solid dense phase fluidized bed allocated with three vertical internals was simulated by the Eulerian two-fluid model. The effects of particle shapes were taken into account by an inter-phase drag model, and more effort was devoted to the effects of the boundary conditions of particles at walls. Meanwhile, experiments of a three dimensional lab-scale fluidized bed were conducted to provide available validation data. The quantitative analyses included axial profile of the pressure, radial profile of solids concentration, and power spectral density of particle mass flow rate at the bed outlet. It showed that specular reflection coefficient only affects the macroscopic behavior of the bed slightly, but the local particle motion near walls significantly for the bed without internals. While for the bed with internals featuring a remarkable increase in wall area, specular reflection coefficient can significantly influence dynamics of gas and solids. Therefore, the value of specular reflection coefficient should be selected in an appropriate range for beds with internals, to predict the system reasonably.

Key words: two-phase flow, fluidized-bed, internals, particles with irregular shapes, CFD, wall boundary condition

摘要：

采用双流体模型对设置竖直隔板的气固密相流化床中非球形颗粒的运动进行了模拟，颗粒形状的影响由相间曳力模型考虑，重点考察壁面处颗粒边界条件的影响。同时进行了实验室规模三维流化床的流化实验，以验证模型的有效性。通过压降轴向分布、颗粒浓度径向分布以及物料出口处颗粒质量流率功率谱估计等定量分析，结果表明：对不设置内构件的自由床，壁面反射系数对系统宏观流动特性影响较小，而对壁面处局部颗粒运动影响较大；对壁面面积大幅增加的内构件床，壁面反射系数可显著改变气体和颗粒的运动特征，取值需控制在适当范围内。

关键词: 两相流, 流化床, 内构件, 非球形颗粒, 计算流体力学, 壁面边界条件