涡轮桨变速搅拌槽内湍流混合的实验研究

Experimental study on turbulent mixng characteristics in a tank stirred with unsteadily rotating Rushton impeller

以NaCl颗粒在水中的溶解为例,对湍流状态下周期性变速旋转的(改变桨叶转向或速度大小,分别称为周期性换向搅拌和周期性依时搅拌)Rushton桨搅拌槽内的混合特性进行了实验研究,并与稳速搅拌进行了对比。实验过程中测量了不同搅拌模式、不同桨叶安装高度时颗粒的溶解时间,结果证明,搅拌槽底部的流型对NaCl的溶解有重要影响;桨叶安装高度对溶解速度的影响不大,周期性依时搅拌时的溶解时间比稳速搅拌时稍短,而周期性换向搅拌则能明显加快溶解速度,提高混合效率。

In this paper, the dissolution of sodium chloride particles in water is choosen as an example to study the mixing characteristics in a tank stirred with periodically co-reversely and time-dependently rotating Rushton impeller. The time needed to achieve completely dissolution status at different impeller off-bottom clearance is measured and compared with different impeller rotational schemes. Results show that the flow pattern of the fluid at the bottom of the tank is critical to the dissolution process. The impeller off-bottom clearance has little influence on the dissolution rate. As far as equivalent power is consumed, the dissolution time of unsteady time-dependent periodic rotational scheme is only a little better than that of the steady scheme. Otherwise, the co-reverse periodic rotational scheme can significantly accelerate the dissolution process, and accordingly increase the mixing efficiency.