桨式搅拌器功率准数三种取得方法的对比

在有挡板条件下,对常用的桨式搅拌器(单层二叶平桨、二叶斜桨、四叶斜桨及双层四叶斜桨),桨槽径比为0.5—0.6,进行搅拌功率曲线的测绘。利用经验公式对功率准数进行了计算,通过关联值与实验值的对比发现,Nagata关联式在层流状态时关联值与实验值相差较小,在湍流时二者相差较大,而Kamei和Hiraoka关联式则在过渡流和湍流区与实验值比较吻合,在层流区的偏差比较大。利用计算流体力学模拟了搅拌器各种状态的功率准数值,模拟值与实验值对比发现,模拟值在不同的雷诺数时都与实验值吻合较好。

Comparison of power number for paddle type impellers by three methods

Power number in baffled stirred tank with paddle type impellers was measured over a range of Reynolds numbers from laminar to turbulent flow regions.Impellers include 2-blade flat paddle impeller,2-blade pitched paddle impeller,4-blade pitched paddle impeller and 4-blade pitched paddle impeller(double-stage),with impeller-to-tank diameter ratio of 0.5-0.6.The measured power number was compared with other two methods,the correlations from literature and computational fluid dynamics(CFD).The power number correlations from the literatures show that the estimated values from the empirical correlations of Nagata agree well with the measured ones in the laminar regions,but the deviation is large in the turbulent regions.However,the power numbers from the correlations of Kamei and Hiraoka have good agreement in turbulent regions,but deviation is large in laminar regions.The power number in stirred tank was also simulated by CFD method.The numerical results present a satisfactory agreement with the experimental data at wide range of Reynolds number.