颗粒碰撞恢复系数对循环流化床提升管内气固流动模拟的影响

摘要

将基于能量最小多尺度方法的曳力模型耦合到欧拉-欧拉双流体模型中,采用全滑移边界条件处理壁面处的颗粒相,对颗粒相为Geldart A类颗粒的循环流化床体系进行了模拟研究.考察了6种颗粒碰撞恢复系数(ess)(0,0.5,0.8,0.9,0.99,0.995)对提升管内轴向空隙率和颗粒循环量等气固流动特性的影响.模拟结果表明,由6种ess计算的轴向空隙率分布结果均呈现典型的底部密相区、中间过渡区和顶部稀相区的“S”型分布；ess较大( 0.99,0.995)时能够提高提升管内轴向空隙率分布预测值和实测值的吻合程度,预测值更真实.；当ess=0.99,0.995时,提升管底部的颗粒相浓度分布预测结果呈现典型的“环-核”结构特征；ess对提升管底部颗粒相浓度和速度径向分布的影响较大.%A circulating fluidized bed riser with Geldart A particles was simulated by using the Eulerian-Eulerian two-fluid model coupling the drag force model based on energy minimization multi-scale(EMMS) approach with the Johnson and Jackson solid phase boundary conditions. The influence of particle-particle restitution coefficients(ess)(0, 0.5, 0.8, 0.9, 0.99, 0.995) on the gas-solids flow was investigated experimentally. It was found that the two-fluid model could predict correctly the axial distribution of the voidage with EMMS approach and free-slip boundary conditions for the solids phase. When ess was 0.99 and 0.995, the predicted results indicated that there was the "core-annulus" heterogeneous flow structure in the riser and the axial voidage distribution was in agreement with the experimental data.