扰流锥对立式涡流空气分级机流场和颗粒分级性能的影响

立式涡流空气分级机淘洗区内部结构是影响其流场分布的重要因素之一，采用数值模拟方法对淘洗区内有、无扰流锥两种不同结构下的空气分级机流场分布及颗粒分级效果进行对比分析。数值模拟结果表明：扰流锥可以阻碍旋涡的形成，使得淘洗区筒体内气流绝对速度整体变小，高频脉动湍涡数量减少；扰流锥减小了环形区和转笼叶片间通道气流径向的速度波动，使得流场分布均匀，有利于提高分级精度。然而，扰流锥的存在使得气流上升过程中的能量消耗增大，导致气流速度降低。碳酸钙粉体分级实验和离散相模拟结果相吻合，物料分级实验结果表明，当进风口风速29 m/s、转速800 r/min时，扰流锥的存在可以使分级粒径减小13.2%，分级精度提高4.2%；然而扰流锥的存在会妨碍粉体在淘洗区筒体内充分分散，导致粗粉中残留较多细粉，旁路值增大1.4%，产生“鱼钩效应”。

Influence of a disturbing cone on the flow field and particle classification performance in a vertical turbo air classifier

The elutriation chamber is one of the important factors affecting the flow field distribution in a vertical turbo air classifier. The flow field and particle classification performance in vertical turbo air classifiers with or without a disturbing cone have been simulated and compared using numerical simulation methods. The simulation results show that the disturbing cone can prevent the formation of a vortex, and the absolute velocity of the airflow and the number of high frequency turbulence eddies are decreased in the elutriation chamber. In the annular region and the channel of the rotor cage, the fluctuations of radial velocity decrease in the presence of the disturbing cone, so that the flow field becomes well-distributed, which improves the classification accuracy. However, the energy consumption of the airflow is increased in the presence of the disturbing cone, which causes the velocity of the airflow to decrease. The results of calcium carbonate powder classification experiments are in agreement with the discrete phase model results. The experimental classification results show that the particle size for the air classifier with a disturbing cone is reduced by 13.2% and the classification accuracy is improved by 4.2% with an inlet air velocity of 29 m/s and a rotor cage speed of 800 r/min. However, the disturbing cone hinders the powder dispersion in the elutriation chamber, resulting in some fine powder remaining amongst the coarse powder, so that the “by-pass” value increases by 1.4% and the “fish-hook effect” is strengthened.