方形旋风分离器内部两相流场的PDA实验研究

应用三维颗粒动态分析仪(3D-PDA)对方形下排气分离器内的气固两相流场进行了测试，得到了几种工况条件下的流场矢量分布。研究发现分离器方腔内的流场偏离其几何中心，并呈中间为强旋流动和边壁附近为弱旋的准自由涡区的特点，且在边角处存在局部小旋涡。不等温流场比等温流场要均匀一些，但旋流强度减弱，分离效率降低。研究结果对于分析分离器的分离机理和结构优化有一定的指导意义。

AN EXPERIMENTAL STUDY ONTHE GAS-SOLID TWO-PHASE FLOW IN A SQUARE CYCLONE SEPARATOR WITH DOWNWARD GAS EXIT BY3D-PDA

Three dimensional Particle Dynamic Analyzer (3D-PDA) was employed to measure the gas-solid two-phase flow in a lab-scale square cyclone separator with downward gas exit under 4 cases of different inlet velocity and particle concentration. The particle used in the test was glass bead of mean diameter 30～40μm.It's found that the center of the flow field deviated from the geometric center of the cyclone. The flow fields showed a feature of Rankine eddy, i.e. strongly swirling region in the central part and pseudo-free eddy region of weak swirling intensity near the cyclone wall. Local vortex existed at the corners where the flow changed its direction sharply. When the cyclone wall was heated and the suspension temperature was elevated, it's found that the flow field became more uniform than that under room-temperature condition. The local vortex at the corners were weakened and the swirling intensity became poorer which led to a decreased total mean separation efficiency from about 81% to 76.5%. The results of this paper provide a further understand of the separation mechanism and guidance for the optimization of the square cyclone separator structure.