Abstract: Due to the distinct differences in size, density or shape of the particles' physical properties, the pattern of the two solid phases is complex. The hydrodynamics of binary mixtures of Geldart A particles and Geldart D particles in gas-solid fluidized bed, particularly the radial flow behaviors, are investigated. By comparing relative solid holdup, it is found that Geldart D particles tend to accumulate near the wall. However, few studies have discussed the occurrence for this phenomenon. The Kutta-Joukowski transverse force is introduced to analyze the distribution characteristics of local density and the local fractions of binary particles in the radial direction from the viewpoint of the forces on particles. Considering the fact that non-uniform structures in intermediate scale, the Eulerian-Eulerian multi-fluid model as well as the drag force model based on the energy minimization multi-scale (EMMS) is used. The Kutta-Joukowski transverse force on particles presents a non-uniform distribution in the radial direction. It is related to the gas-solid velocity-difference vector and the particle velocity radial gradient. Based on the radial profile of the Kutta-Joukowski transverse force, the flow regime is divided into three zones, the Kutta-Joukowski uniform influence zone (zone I), the velocity gradient dominant zone (zone II), and the velocity-difference vector dominant zone (zone III). The results show that the Geldart A particles and Geldart D particles exhibit similar tendencies in zone I to move towards the wall, resulting in a uniform distribution. In zone II and III, both Geldart A particles and Geldart D particles are exerted by the Kutta-Joukowski transverse force towards the wall, leading to a core-annulus phenomenon with low concentration at the center and high concentration near the wall. Compared to Geldart A particles, relatively higher Kutta-Joukowski transverse force on Geldart D particles results in a stronger tendency to move towards the wall region in zone II. In zone III, on the other hand, the tendencies for Geldart A particles and Geldart D particles travelling towards the wall are relatively weak.

Key words: gas-solid fluidized bed, binary particles, radial distribution, Kutta-Joukowski transverse force

摘要： 由于二元颗粒存在物性差异，气固流动体系会呈现出复杂的流体动力学行为。通过对相对固含率进行比较，发现Geldart D类颗粒更倾向于在边壁富集，但目前少有研究对该现象形成的具体原因进行报道。通过引入Kutta-Joukowski横向力，对气固流化床-提升管耦合反应器底部区域二元颗粒所受横向力进行考察，进而分析了二元颗粒局部浓度/局部分率沿径向的分布特性。Kutta-Joukowski横向力在床内的分布并非均匀，根据颗粒相与气相的速度矢量差以及颗粒速度分布梯度对Kutta-Joukowski横向力沿径向分布的影响程度，对耦合反应器底部流化床进行分区，包括Kutta-Joukowski横向力均匀影响区(I区域)、速度梯度主导区(II区域)、气-固速度矢量差主导区(III区域)。结果表明，在I区域，Geldart A类颗粒和Geldart D类颗粒向边壁运动的趋势相当，促使颗粒相沿径向均匀分布；在II, III区域，Geldart A类颗粒和Geldart D类颗粒均受到指向边壁的Kutta-Joukowski横向力，进而呈现中心低、边壁高的类“环-核”不均匀分布。在II区域Geldart D类颗粒受到的Kutta-Koukowski横向力更大，导致其向边壁聚集的趋势更明显。而在III区域，Geldart A类颗粒和Geldart D类颗粒向边壁运动的趋势均较弱。

关键词: 气固流化床, 二元颗粒, 径向分布, Kutta-Joukowski横向力