基于LSD-DEM模型的鼓泡流化床物料运动特性分析

Study on material movement characteristics of bubbling fluidized bed based on LSD-DEM model

鼓泡流化床内部的气固流动结构在整体和局部上呈现出明显的非均匀性的特征,因此会对床内颗粒的流动状态、热量传递、掺混造成显著的影响。文章基于计算流体力学和离散元模型(Discrete Element Model,DEM),结合局部结构相关(Local-Structure-Dependent,LSD)曳力模型,充分考虑了两相流中颗粒相、气泡相以及乳化相之间多尺度的相互作用,对鼓泡流化床内的气固两相流动特性进行数值模拟,分析了床内颗粒浓度、颗粒速度等分布特性。结果表明,LSD-DEM曳力模型下床层膨胀比较小而气泡直径较大。LSD-DEM曳力模型能够更好地预测鼓泡流化床内气固两相流动。

The gas-solid flow structure in the bubbling fluidized bed shows obvious heterogeneous in the whole and local,which will have a significant impact on the flow state,heat transfer and mixing of particles in the bed.In this paper,the gas-solid two-phase flow characteristics are simulated,the distribution of solids concentration and particle velocity are analyzed in the bubbling fluidized bed based on DEM(Discrete Element Method)and LSD(Local-Structure-Dependent)drag model,which fully consider the multi-scale interaction among solids phase,bubble phase and emulsion phase in the two-phase flow.The results show that bed expansion ratio is smaller while the bubble diameter is larger which indicates that the LSD drag model could predict gas-solid two-phase flow better in the bubbling fluidized bed.