偏心轴搅拌槽内的层流流场特性

针对搅拌槽内处理层流状态下高黏度流体时混合效率偏低的现象,提出一种偏心轴(轴结构为曲轴)搅拌方式。首先以纯度为99%的甘油为介质,传统的二叶平桨为研究对象,对直径0.3 m的搅拌槽内的层流流场进行数值研究。中心搅拌时速度模拟结果与试验结果对比,验证了所建模型及模拟方法的可靠性。研究发现,与中心搅拌相比,偏心搅拌和偏心轴搅拌所产生的流场结构是非对称的;相同转速下,偏心轴搅拌相比中心搅拌时流体的槽内整体的体积加权平均速度增大了约68%,功率准数比中心搅拌增加了约15.3%;偏心轴搅拌对槽内速度的提升,扩大了流体扰动范围,对提高槽内流体混合效率具有一定的优势。

Laminar flow field characteristics in the stirred vessel equipped with an eccentric-shaft impeller

For the purpose of improving mixing efficiency of the stirred tank with high viscosity fluid laminar flow condition, an eccentric-shaft agitation method was proposed. With a purity of 99% glycerol as medium, and the traditional 2-flat-blade impeller as the research object, the laminar flow fields were numerically studied. The inner diameter of the stirred vessel was 0.3m and the agitated fluid was glycerol. The modeling reliability and simulation methods of the concentric agitation were validated by experimental results. In comparison with the concentric agitation, flow fields generated by eccentric and eccentric-shaft agitation were asymmetrical, and theoverall volume weitghted average velocity of the groove fluid generated by eccentric-shaft agitation could be raised by 68%. And furthermore, when operated under the same speed, the power consumption of eccentric-shaft agitation increased 15.3% than that of concentric agitation. However, the eccentric shaft agitation increased the speed in the tank and expanded the range of disturbance. Accordingly, the superiority of eccentric-shaft agitation of improving the mixing efficiency in the tank was apparent.