Mixing characteristics of high-viscosity fluids with laminar flow in a stirred tank with a fractal arranged perforated impeller

Abstract

Fractal arranged perforated impeller (FAP impeller) was introduced to minimize the isolated mixing region and expand the chaotic mixing region for the mixing process of high-viscosity fluids with laminar flow. The mixing performance of FAP impeller and Rushton turbine were comparatively investigated with numerical simulation and experimental analysis. Results showed that the introduction of fractal arrangement perforated holes in the impeller blades resulted in lower power consumption, power number and mixing efficiency number, and higher values of largest Lyapunov exponent compared with conventional ones. The higher mixing efficiency could be obtained with an increase in fractal iteration number of FAP impeller. Meanwhile, the design of fractal arrangement perforated holes in the impeller blades could destroy the recirculation zone behind impeller blades, enhance the strain rate, and reduce the dimension of isolated mixing region compared with standard ones, and the aforementioned phenomena became more prominent with the increase of fractal iteration number of FAP impeller. In addition, it could be also found that fractal arrangement perforated holes in the impeller blades could enhance the strain rate and improve the fluid mixing efficiency as compared to horizontal-vertical arrangement perforated holes and a simple whole perforated hole in the impeller blades with equivalent cut area.