Abstract: The particle classification performance of air classifier mainly depends on the flow field distribution. Two cyclone classifiers were designed which characterized by different air inlet positions. The effect of flow field pattern on particle tracking and classification performance was investigated by using numerical simulation and classification experiments. The results showed that some fine particles were carried into coarse powder by the downward stream near the wall,which aggravates the fine particle entrainment and impairs the classifying accuracy. Two vortexes were formed in the new type cyclone classifier. The upper vortex with 80% of the total air volume moves upward and classifies the fine particles secondarily near the wall,which helps to improving classification efficiency. The downer vortex carries little fine particles,which decrease the particle entrainment in coarse powder. When inlet air velocity varies from 10 m/s to 22m/s,classifying accuracy index increases 27% on average and the pressure drop decrease to 53%-62% compared with the traditional cyclone classifier.

Key words: powder technology, cyclone classifier, flow field pattern, numerical simulation, classification performance, particle size distribution

摘要： 气流分级器性能的优劣很大程度上取决于流场分布，改变常规旋风分级器的切向进风口位置，在分级空间建立不同类型的离心流场，采用数值模拟和分级试验手段分析了分级流场形态对颗粒运动过程和分级性能的影响。结果表明，传统旋风分级器边壁下行流造成粗粉中细颗粒夹带较多，影响分级精度；新型旋风分级器内形成上下两个旋涡，上旋涡均为上行气流，其流量约占总风量的80%，下旋涡携带细颗粒较少，降低了细颗粒进入粗组分的概率；上旋涡可实现对边壁区的细颗粒的轴向淘洗、再分级，提高了分级精度。试验结果表明，入口气速从10m/s增加至22m/s。相较于传统旋风分级器，新型旋风分级器的分级性能明显改善，分级精度指标平均提高27%，压降损失为传统旋风分级器的53%~62%。

关键词: 粉体技术, 旋风分级器, 流场形态, 数值模拟, 分级性能, 粒度分布