立磨选粉机操作参数对分级流场影响的数值模拟

采用离散相流体模型和RNG k-ε湍流模型,对涡轮式立磨选粉机内的气-固两相流场进行数值模拟,对比分析不同操作参数下的速度场、压力场和设备分级效率,获得转笼转速和系统风量对选粉机分级流场的影响规律,并进行相关的试验研究。结果表明,较低的转笼转速和过大的系统风量均会引起叶片间退行面处正漩涡的产生;转笼转速过高或系统风量较小时,分级叶片间的进入面处会出现反漩涡。正、反漩涡的产生均加剧了分级叶片间的速度波动,严重影响了分级流场的稳定性,同时也导致选粉机循环负荷的增加。综合数值模拟与试验分析,系统风量为5 500 m3/min与转笼转速为55 r/min是SMG5500型立磨选粉机的最佳参数匹配。

Numerical Simulation on Effect of Operation Parameters on Grading Flow Field of Vertical Mill Classifier

The gas-solid two phase flow field in vertical mill classifier was simulated numerically with computational fluid dynamics(CFD),in which the discrete phase fluid model(DPM) and RNG k-ε turbulence model were applied.After comparatively analysing the velocity field,the stress field and the equipment classification efficiency under different operating parameters,the influence law of rotation speed of turn cage and air quantity of system to the grading flow field of classifier was acquired,and the experimental research was made.The results show that the lower speed of turn cage and bigger air quantity of system causes the production of positive vortexes between the retreative faces of blades,and the higher speed of turn cage and smaller air quantity of system brings the production of reverse vortexes between the entrance faces of blades.The production of positive and reverse vortexes exacerbates the speed fluctuation between grading blades,and impacts seriously on the stability of the grading flow field,but also leads to the increase of cycle load.Synthesizing the numerical simulation and experimental analysis,the best matching parameters of vertical mill classifier SMG5500 are that the air quantity of system is 5 500 m3/min and the rotation speed of turn cage is 55 r/min.