湍动流化床颗粒流动特性的数值模拟

采用欧拉-拉格朗日研究方法,通过数值模拟对湍动流化床流化特性开展研究,得出了床层内压力、固含率、颗粒速度及粒度分布规律。结果表明:床层中心处的压力沿轴向高度逐渐减小;固含率沿轴向高度逐渐减小,呈“ε”型分布,分为底部密相区、中间过渡段及上部稀相区,在稀相区呈现出中间低、边壁高的“环核”结构,且该结构沿轴向逐渐减小,直至消失;颗粒轴向速度沿轴向起伏变大,中心区域的颗粒速度普遍大于边壁处的颗粒速度,且颗粒下落位置由边壁向中心存在移动;颗粒粒径分布沿轴向逐渐降低,稀相区分布相对比较均匀。

NUMERICAL SIMULATION OF PARTICLE FLOW CHARACTERISTICS IN TURBULENT FLUIDIZED BED

The Eulerian-Lagrangian two-fluid model was used to study the fluidization characteristics of the turbulent bed by numerical simulation.The pressure,solid holdup,particle velocity and particle size distribution of the bed were studied.The results show that the central pressure gradually decreases along the axial height,while the solid holdup gradually decreases along the axial elevation,showing a“ε”-type distribution.Accordingly,the bed is divided into a bottom dense phase zone,a middle transition zone,and a top dilute phase zone.In the dilute phase region,the core-annular-structure gradually decreases along axial direction until it disappears.Besides,the axial velocity of the particles fluctuates in the radial direction,which in the central zone is generally greater than that at the wall,and the position where the particles falling moves from side wall to the center.The average particle size gradually decreases along the axial axis,and the particle diameter distribution of the dilute phase zone is relatively uniform.