Mixing Characteristics of Shear-Thinning Fluids in a Fractal Perforating Impeller Stirred Reactor

Abstract

Fractal perforating impeller was introduced to minimize the stagnation zone and enlarge the well-mixed zone for the mixing process of shear-thinning fluids with yield stress in a stirred reactor. The mixing performance of the fractal perforating impeller was investigated by applying experimental analyses and numerical simulation. The results showed that the fractal spaces introduced in the impeller blades provided a reduction in power consumption and an improvement in mixing efficiency compared with standard ones, and the mixing efficiency and the energy-saving effect continued to improve with the increase of the fractal iteration number of fractal spaces in the impeller blades. The fractal-3 perforating impeller reduced about 27.92, 25.87, and 12.56% of power consumption compared with a Rushton turbine, fractal-1 perforating impeller, and fractal-2 perforating impeller at Re y = 128, respectively. Meanwhile, the fractal-3 perforating impeller decreased about 22.06, 18.18, and 8.25% of the mixing time compared with a Rushton turbine, fractal-1 perforating impeller, and fractal-2 perforating impeller at P v = 0.45 kW·m –3, respectively. In addition, the introduction of fractal spaces in the impeller blades could reduce the size of the trailing vortex and destroy the recirculation zone compared with standard ones, and this helped reduce the energy consumed at the tailing vortices and dedicate more energy to fluid mixing. A desired result was obtained that the design of a fractal perforating impeller could expand the high-velocity region and enlarge the size of the cavern compared with a Rushton turbine and increasingly so with the increase of the fractal iteration number of fractal spaces in the impeller blades.