搅拌槽内具滑移特性非牛顿流体的搅拌功率及混合特性研究

Agitating Power Demand and Mixing Performance of Non-Newtonian Fluid with Slip Behavior in a Stirred Tank

在直径为0.48m的搅拌槽内考察了包括CBY、45°斜叶桨及螺带在内的五种搅拌桨对三种不同流变特性的具有滑移现象的非牛顿高黏流体混合效果的影响。首先采用HAAKERS150流变仪对三种流体的流变特性进行测定和表征,比较各种桨型在液位与槽径比H/T为0.28～0.52内的混合效果,得出不同流体中适宜的搅拌桨型及桨型适宜的混合液位范围。结果表明,在具有滑移特性的流体中各种桨型的Metzner常数通常高于经验数值;螺带桨在很宽的表观黏度范围及较宽的雷诺数范围下均表现出较好的混合效果,而CBY及45°斜叶桨型只适用于流体表观黏度较小而雷诺数相对较高的情形。在液位最低时,流体的混合时间和混合能并非最低,各种桨型的最佳操作液位在槽径的0.35～0.43倍内。

Experiments were carried out in a transparent stirred tank with diameter of 0.48 m and dished bottom. Five different impellers including axial flow impeller CBY,45° pitched blade turbine and helical ribbons were used to investigate the mixing performances of three different kinds of non-Newtonian fluids with slip behavior. The theological performances of fluids used in this work were determined by HAAKE RS150 rheometer. Under the fluid level ranged from 0.28 to 0.52 times of the tank diameter,the mixing performances of five impellers were investigated for three different fluids,separately. Results show that the helical ribbon is suitable for different fluids with good mixing performance. In contrast,axial flow impeller CBY and 45° pitched blade turbine have high efficiency only for the mixing of relative lower viscous fluid. It was found that,when the fluid level in the stirred tank is too low,all kinds of impeller used in this work can＇t have good mixing performance; the optimal fluid level is between 0.35～0.43 times of the tank diameter.