弯管稀相气力输送CFD-DEM法数值模拟

利用CFD-DEM方法对稀相气固两相流在带有弯管的气力输送管道内的流动特性数值模拟。通过CFD求解连续气相流场,使用DEM求解离散颗粒相运动及受力,为提高仿真速度,模型忽略了空隙度对气相的影响。仿真结果显示了颗粒在弯管内形成颗粒绳及在垂直管道内颗粒绳分散的过程,并获取了颗粒-颗粒、颗粒-壁面的碰撞信息。对比弯管上下两部分的碰撞情况,颗粒及壁面在弯管下半部分受到的撞击和磨损更严重。通过对气力输送各类工作参数的研究发现,其对管道内气固两相流的流动特性和碰撞情况有着不同程度的影响。气流速度对颗粒绳分散影响甚微,但对弯管内颗粒碰撞强度有明显影响。随着颗粒质量流量的增加,形成的颗粒绳更紧凑、分散速度更慢,并在弯管中形成了阻碍颗粒-壁面碰撞的防护层。弯径比的增加也能加强颗粒绳的紧凑度,减缓颗粒绳的分散速度。

Simulation of dilute pneumatic conveying with bends by CFD-DEM

CFD-DEM model was used to simulate the gas-solid flow in dilute pneumatic conveying with bends. In CFD-DEM, the discrete particle phase was obtained by Discrete Element Method (DEM), and the flow of continuum gas phase was determined by Computational Fluid Dynamics (CFD). In order to consume less simulation time, the effect of the particle solid fraction on the gas phase was not taken into account. The results showed the particle rope formation in the bend and its dispersion in the vertical pipe, and obtained the particle-particle and particle-wall collision information. Comparison of the collision information in the bend, the collision and abrasion seemed more intensive at the bottom of the bend. It is also found that the geometry and parameters have different magnitude effects to the gas-solid flow and collisions in the pipe. The gas velocity was considered to be limited influence to the rope dispersion, but significant effect to the collisions in bend section. With the increase of the solid mass flow, the particle rope seemed stronger and dispersed at a low rate, and there was a shield formed to impede particle-wall collision at the bend section. The increase of the bend radius ratio also made the particle rope stronger, and the dispersion rate lower.