流体流变性对错位六弯叶桨流场特性的影响

利用计算流体力学(CFD)的方法,以高黏牛顿流体和假塑性非牛顿流体为研究对象,对错位六弯叶桨在层流域的搅拌流场特性进行了研究。结果表明:数值计算得到的功率值与实验测量值吻合较好,搅拌雷诺数对假塑性流体搅拌流场的量纲一速度和切应变速率影响较大,因此提高转速对改变流场的速度及切应变速率分布是一个有效的办法;而流体的流变性只对假塑性流体的量纲一速度有明显影响,对切应变速率影响较小,当流变指数n<0.3时与n基本无关。当流动由层流向过渡流转变时,搅拌桨的流量准数及泵送效率有显著提高;假塑性流体的流变指数降低时,其泵送效率显著下降。研究进一步认识了错位桨在不同流体中的搅拌流场特点,为高黏假塑性流体搅拌桨的设计、应用以及开发新型搅拌桨提供了参考。

Influence of fluid rheology on flow field features stirred by impeller of perturbed six-bent-bladed turbine

The laminar flow field stirred by impeller of perturbed six-bent-bladed turbine(6PBT) in a cylindrical vessel was studied by means of computational fluid dynamics(CFD),with highly viscous Newtonian fluid and pseudoplastic non-Newtonian fluid as research object.The results show that the numerical calculated value of power consumption in glycerine is in good agreements with that of the experimental measurement.For pseudoplastic fluids,the value of Reynolds number has a major influence on the normalized velocity and shear rate,and the proper increasing speed would be a better way for improving the distribution of velocity field and shear rate.The rheological properties of fluids have obvious influences on the normalized velocity,but minor influences on shear rate specially;there is no correlation between the rheological index and shear rate when n<0.3.With the flow development from the laminar flow to the transitional flow regime,the flow number and pumping efficiency of 6PBT impeller increase considerably.Moreover,the pumping efficiency of the impeller decreases obviously as the rheological index of pseudoplastic fluids reduces.The research results promote the understanding of the stirring performance of the 6PBT impeller in the different fluids and provide valuable instructions and references for the design,application and development of new type impeller in highly viscous fluids.