基于CFD-DEM的旋流泵混合颗粒固液两相流研究

Solid-liquid Two-phase Flow of Mixed Particles in Vortex Pump Based on CFD-DEM

为了探究折叶片旋流泵固液两相输送机理,基于CFD-DEM(Computational fluid dynamics-discrete element method)耦合算法,选用油菜籽和黄豆颗粒等比例混合,在不同流量工况和体积分数下对旋流泵进行固液两相流数值模拟和试验研究。同时也研究了折叶片旋流泵内部流动规律及颗粒分布特征。小流量工况下,进口管内螺旋回流长度较长,对进口来流扰动较大。随着流量增大,进口管回流长度逐渐缩短。叶轮前端面旋涡随流量增大,数量先增加后减少,且逐渐向折点方向聚拢。泵内颗粒受循环流和贯通流的共同作用,进口管中心部颗粒主要受贯通流影响,直接穿过无叶腔,冲击叶轮进口;靠近管壁的颗粒受循环流影响较大。无叶腔内颗粒分布呈现出:中心部最高,中间部随外径增大浓度逐渐降低,外缘部浓度稍有上升。叶轮前半部颗粒数量明显少于叶轮后半部,颗粒沿叶片第1段折边运动,在折点处开始发生分离,不再跟随第2段折边。不同工况下,泵进口有不同程度的螺旋回流现象,导致进口过流面积减小。循环流的存在,使得无叶腔和进口管的颗粒充分旋起,泵送能力增强,不易发生堵塞。

In order to explore the mechanism of solid-liquid two-phase flow in the folded-blade vortex pump,based on the computational fluid dynamics-discrete element method(CFD-DEM) coupling algorithm,the rapeseed and soybean particles were mixed in equal proportion,and the solid-liquid two-phase flow numerical simulation and experimental research of the vortex pump were carried out under different flow conditions and volume concentrations.The internal flow law and particle distribution characteristics of the folded blade vortex pump were also studied.Under the condition of small flow rate,the rotating reflux length in the inlet pipe was longer,and the disturbance to the inlet flow was greater.As the flow rate was increased,the reflux length of the inlet pipe was decreased gradually.With the increase of flow rate,the number of vortices on the front surface of the impeller was increased first and then decreased,and gradually gathered towards the turning point.The particles in the pump were affected by the combined action of circulating flow and through flow.The particles in the center of the inlet pipe were mainly affected by the through flow,directly passing through the vaneless cavity and impacting the impeller inlet.The particles near the pipe wall were greatly affected by the circulating flow.The particle distribution in the leafless cavity showed that the concentration in the center was the highest,the concentration in the middle was decreased gradually with the increase of the outer diameter,and the concentration in the outer edge was increased slightly.The number of particles in the front half of the impeller was significantly less than that in the rear half of the impeller.The particles moved along the folding edge of the first section of blade,and began to separate at the folding point,and no longer followed the folding edge of the second section.Under different working conditions,the pump inlet had different degrees of rotational reflux,resulting in a decrease in the inlet flow area.The existence of circulating flow made the particles in the vaneless cavity and the inlet pipe fully rotated,the pumping capacity was enhanced,and the blockage was not easy to occur.