冲缝单元堵塞过程数值模拟研究

Numerical Simulation Study of Blockage Process of Punching Screen Unit

摘要: 冲缝套作为独立防砂单元或优质筛管的常用保护壳，常被用作防砂管的第一层挡砂单元，然而大多数筛管在考虑其防砂性能时往往只考虑筛管内部挡砂介质的影响，而忽略冲缝套的堵塞对于筛管整体挡砂性能的影响。为探究冲缝套的堵塞过程，本文以微观的视角，利用计算流体力学–离散元法(CFD-DEM)耦合的方法，模拟单个冲缝套防砂单元在含有细粉砂的条件下内部颗粒、流体运动，分析内部流动状态对颗粒运动的影响。结果表明：冲缝单元堵塞过程分为开始初始、堵塞加剧、堵塞稳定三个阶段；在堵塞开始阶段粗颗粒形成稀松的桥架结构；堵塞加剧阶段颗粒聚集成砂团，由两边缝口向单元中心发展；堵塞平衡阶段细粉颗粒沉积，呈现分层现象。

Abstract: Punched seam sleeves are commonly used as a protective casing for individual sand control units or high quality screen tubes, and are often used as the first layer of sand retaining units for sand con-trol tubes. However, most of the punching screen only consider the influence of the sand barrier media inside the screen pipe when considering its sand barrier performance, and ignore the influ-ence of the blockage of the punching screen on the overall sand barrier performance of the screen pipe. In order to investigate the blockage process of the punching screen, this paper uses the cou-pled computational fluid dynamics-discrete element method (CFD-DEM) to simulate the internal particle and fluid motion of a single punching screen sand control unit under the condition of con-taining fine powder sand, and analyze the influence of the internal flow state on the particle motion from a microscopic viewpoint. The results show that: the blockage process of the punching screen unit is divided into three stages: initial blockage, intensified blockage and stable blockage; the coarse particles form a loose bridge structure in the initial blockage stage; the particles gather into sand clusters in the intensified blockage stage and develop from the two slit openings to the center of the unit; the fine powder particles are deposited in the blockage equilibrium stage, showing the phenomenon of stratification.