竖直涡旋向对卧轮式分级机流场及性能影响

Effect of vertical vortex direction on flow field and performance of horizontal turbo air classifier

采用数值模拟方法对卧轮式分级机内气相流动特性进行了研究,重点考察了竖直涡旋向对分级机内全流场的影响。模拟结果表明,分级机锥体段以旋转上升的竖直涡为主流型,竖直涡旋向对分级室内流型有重要影响。根据右手定则,竖直涡旋向与转笼旋向满足象限Ⅰ和Ⅲ时,分级室内形成两股旋向相反的水平涡,局部出现二次涡流,转笼外缘气流切向速度接近为0;竖直涡旋向与转笼旋向满足象限Ⅱ或Ⅳ时,分级室内流场分布一致性较好,转笼外缘及叶片间速度分布比较均匀且波动较小。以流化催化裂化(FCC)催化剂为分级物料,处于象限Ⅳ的分级机其分级粒径平均减少5.3?m,分级精度平均提高7.5%;以粉煤灰为物料,分级粒径平均减少2.2?m,分级精度平均提高8.4%,粉料分级试验结果与数值模拟结果吻合。研究结果对卧轮式分级机的结构设计有一定指导作用。

Flow field characteristics in horizontal turbo air classifier were investigated by numerical simulation. Effects of swirling direction of the vertical vortex were taken into account. The simulated results showed that, an upwind vertical vortex is the dominant flow in conical part of the classifier, and the vertical vortex direction has a significant influence on flow pattern inside the classifying chamber. By controlling the vertical vortex direction, the flow field distribution can be greatly improved. For the classifiers in quadrant 11 or IV according to the right-hand rule, the flow field inside the classifying chamber was evenly distributed. Cut sizes of the classifier are decreased by 5.3μm for FCC catalysts and 2.2μm for fly ash while the classification accuracies are increased by 7.5% and 8.4%, respectively. The powder classification experiments well validate the simulation results. Those results could provide guidance to the design of horizontal turbo air classifier.