Abstract:

The flow fields in the classifiers with or without the guide-vane were simulated and compared using ANSYS-Fluent 17.0 to study the effect of the guide-vane on the flow field in turbo air classifiers. The simulation results show that the airflow tangential velocity at the outer edge of the rotor cage is reduced because of the guide-vane. It influences the vortex distribution in the channel of the rotor cage and makes the steady operating conditions of these two structures different. The guide-vane can reduce the radial velocity fluctuation and turbulence dissipation rate near the outer edge of the rotor cage, where the flow field distribution is relatively uniform, and it is helpful to improve the classification accuracy. Besides, the guide-vane changes the velocity field distribution of the annular region through guiding the airflow. The tangential velocity of airflow decreases and the radial velocity increases. Increase of radial velocity leads to the increase of the cut size. The calcium carbonate classification experimental results show that the cut size is increased and the classification accuracy is improved for the turbo air classifier with the guide-vane. The large turbulent dissipation rate near the guide-vane is conducive to dispersing the powder, weakening the fish-hook effect obviously.

Key words: powder technology, computational fluid dynamics(CFD), numerical simulation, turbo air classifier, guide-vane, fish-hook effect

摘要：

利用ANSYS-Fluent 17.0软件对有、无导风叶片两种结构的涡流空气分级机内流场进行数值模拟和对比分析，研究了导风叶片对涡流空气分级机内流场的影响。数值模拟结果表明：导风叶片降低了转笼外缘处气流切向速度，从而影响转笼通道内旋涡的分布情况，使有、无导风叶片两种结构的稳定工况不同；导风叶片减小了转笼外缘处气流径向速度的波动和湍流耗散率，此处流场分布相对均匀，有利于提高分级精度；此外，导风叶片在导流过程中，改变了环形区速度场的分布，气流切向速度减小，径向速度增大，径向速度的增大使其分级粒径增大。碳酸钙物料分级实验结果表明：具有导风叶片结构的涡流空气分级机分级粒径较大，分级精度较高；导风叶片处较大的湍流耗散率有助于粉体分散，明显减弱“鱼钩效应”现象。

关键词: 粉体技术, 计算流体力学, 数值模拟, 涡流空气分级机, 导风叶片, 鱼钩效应