Abstract: A two-stage cyclone combining multiple helical tubes and a cylinder was designed to improve the separation efficiency. The liquid-solid two-phase flow characteristic and separation performance were investigated inside the cyclone by experiment and numerical simulation. The enhanced separation mechanism was revealed which the spiral tube group in parallel connection method was used as the cyclone inlets. The results showed that the first stage swirling flow was formed inside the spiral tube, and the fluid was subjected to centrifugal force based on the Dean eddy current principle. The denser solid particles moved towards the outside of the spiral tube, and the solid phase was concentrated on the outside and bottom of the spiral tube. Multiple spiral tubes were evenly arranged in the circumferential direction, and all of the spiral tube outlets were tangentially installed to the inner wall of the cyclone. The jet flow superposition was generated and the second stage swirling flow was strengthened. Three factors and five levels of the first stage swirl parameters were selected for orthogonal test, and the conclusion was obtained that the spiral tube number N had the most significant impact on the liquid-solid separation in the second stage swirling region. Under the same flow rate of a single tube, the solid bottom flow distribution rate decreased as the number of helical tubes increased. In the second stage swirling region below the spiral tube outlets, the swirling velocity and axial velocity were relatively lower for N≤3, and there were a large number of particles in the central region. In the secondary swirl region with N>4, the shear layer between adjacent jets was superimposed, and the fluid vortex near the outlet of the spiral tube was significantly increased, resulting in enhanced disturbance of axial flow to the central fluid. The appropriate number of spiral tubes effectively enhanced the swirling intensity near the inner wall, with relatively less disturbance to the central fluid. The distribution of particles in the near wall swirl zone increased, which was beneficial for the liquid-solid separation process in the two-stage swirling cyclone.

Key words: two-stage swirling separation, spiral tube, concave-wall jet, flow field superposition, liquid-solid two-phase

摘要： 为提高旋流器分离效率，设计了螺旋管组与圆筒体组合的两级旋流分离器，采用实验和数值模拟研究了旋流器内液固两相流动特性及分离性能，揭示了螺旋管组并联作为旋流器入口的强化分离机理。结果表明，螺旋管内形成一级旋流流动，螺旋管出口与分离器内壁面相切，螺旋管组周向均匀布置，射流流场叠加强化了二级旋流流动，有效提高了物料处理量和分离效率。选取一级旋流参数的3个因素5个水平进行正交试验，结果表明，螺旋管数量N对二级旋流区液固分离有较大影响。单管流速的相同工况下，随着螺旋管数量增加，固相底流分配率下降。对混合相流场的研究表明，二级旋流区内相邻射流间流场叠加对剪切层内流体扰动增强，螺旋管数量N>4时不利于液固分离。

关键词: 两级旋流分离, 螺旋管, 凹壁面射流, 流场叠加, 液-固两相