循环流化床内细长颗粒取向分布的多向耦合数值模拟

Numerical Simulation on Orientation Distribution of Slender Particles in a CFB Based on Gas-Solid Multi-Way Coupling

采用拉格朗日时间尺度与k-ε模型的耦合关联式,构建三维多向耦合的细长颗粒气-固两相流模型,并采用此模型对某一实际流化床内的细长颗粒两相流场进行了数值模拟.研究发现,在提升管内径向方向上,由中心区域到近壁区,细长颗粒的取向性越发趋于明显,除近壁区受壁面约束影响外,其他区域均以15°~30°章动角姿态流化运动的细长颗粒最多;在高度方向上,由床层底部到提升管出口处,细长颗粒的取向性越发趋于明显并在提升管出口处达到最大值.

In this paper,a three-dimensional two-way coupling model of slender particle gas-solid flow was proposed incorporating the coupling correlation between Lagrangian time scales andκ-εmodel.A cold-state slender particle flow was investigated using the model.It is found that from central region to near-wall region in radial direction in the riser,the orientation of slender particles becomes more evident,and the number of slender particles moving up with the nutation angle of 15°-30°is the highest in most radial regions except near-wall region because the walls affect local fluid field and hinder the free movement of cylindrical particles in near-wall regions.From the bottom to the exit in the perpendicular direction in the riser,the orientation of slender particles tends to be evident and approaches the maximum in the exit region,that is,the number of cylindrical particles moving up with the nutation angle of 15°-30°is the highest.