Solids suspension in stirred tanks with pitched blade turbines
Solids suspension in stirred tanks with pitched blade turbines
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DOI：
10.1016/s0009-2509(03)00023-x
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发表时间：
2003-05
影响因子：
4.7
通讯作者：
R. Sharma;A. A. Shaikh-A.
中科院分区：
文献类型：
--
作者：
R. Sharma;A. A. Shaikh-A.
为了建立一个普遍适用的悬浮临界转速关联式，在15-121 cm的水槽中，用四种不同尺寸的球形玻璃珠，以四叶片和六叶片的斜叶涡轮作为叶轮，进行了广泛的悬浮试验。修改罐底部的周边，以包括永久性圆角，以消除诱导再循环回路的影响，其导致形成未悬浮固体的周边圆角。悬浮液的临界转速Nc和功率Pc被观察到独立地随D和T而变化，从而为每个变量Nc和Pc给出两个相关性;一个用于紧密接近的叶轮操作，其中Nc和Pc都与离底叶轮间隙保持不变，第二个用于Nc和Pc受叶轮位置显著影响的区域。固体的物理特性的影响也包括在所提出的四个相关性。可以清楚地注意到，相关性在D/T的临界值以下都是有效的，超过该临界值，叶轮下方的停滞区中的捕获颗粒需要额外的能量才能被耙出和悬浮，从而打破了迄今为止保持的Nc（或Pc）和D/T之间的对数线性关系。悬浮速度和功率的比较已与公开文献。更重要的是，早期的研究在Nc预测中彼此不同的原因已经被确定。
In view of developing a universal correlation for critical speed of suspension, extensive suspension experiments were conducted with tank scales in the range of 15–121 cm , D/T from 0.083 to 0.625, using four different sizes of spherical glass beads and employing Pitched Blade Turbines with four and six blades as the impellers. The periphery of the tank bottom was modified to include a permanent fillet in order to eliminate the effect of induced recirculation loop, which account for the formation of peripheral fillets of unsuspended solids. The critical speed of suspension Ncand power Pcwere observed to vary independently both with D and T to give two correlations for each of the variables, Ncand Pc; one for the close proximity impeller operation where both Ncand Pcremained invariant with off-bottom impeller clearance and the second for the region where Ncand Pcwere affected significantly by the impeller position. The effects of the physical characteristics of the solids were also included in the four correlations so proposed. It was clearly noticed that the correlations were valid up to a critical value of D/T beyond which the trapped particles in the stagnant zone below the impeller needed extra energy to be raked out and suspended, thus breaking the log-linear relationship between Nc(or Pc) and D/T hitherto maintained. Comparisons of the suspension speed and power have been made with open literature. More importantly, the reasons why the earlier studies differed with each other in Nc-predictions have been identified.