Since combined stirring paddles have been used in many industrial fields, internal flow fields in a stirred tank generated by double helical ribbon stirring blade and six pitched blade disk turbine impellers at 180,240,300 r/min rotating speeds were studied by using CFD analysis. The NavierStokes equations in multiple reference frame (MRF) and standard kω turbulence model were used in numerical simulations. Tracers were put into in the tank to measure the mixing time in mixing processes. The results show that a typical vortex swirling flow appears in the stirred tank in liquid phase in the region between two paddles. The mixing time is determined to be 9.6 s based on analysis of tracer concentration curves at monitoring points. Stirring effect and mixing time and stirring power at 240 r/min rotating speed have an absolute advantage for industrial application. An industrial scale experiment has proven the correctness of the model mentioned above. The study in the paper can provide a theoretical basis for design and engineering application of stirred tank with nonNewtonian fluid turbulent mixing layers.
DONG Min,XIA Chen-Liang,LI Xiang. Numerical simulation of internal flow field and mixing time in stirred tank with combined impellers[J]. Journal of Drainage and Irrigation Machinery Engin, 2019, 37(1): 43-48.