Improvement on the distribution uniformity of hydrodynamics in a stirred tank with a novel H-like fractal impeller

Fractal theory provides a new strategy for the equipment design and industrial amplification. In this work we propose a novel H-like fractal (HLF) impeller to improve the distribution uniformity of hydrodynamics in stirred tanks. The impeller with two vertical blades becomes fractal impellers by designing each vertical blade as an H-shaped sub-blade (HLF-1) or uniform arrangement of H-shaped sub-blades (HLF-2). Flow characteristics including velocity and turbulent kinetic energy (TKE) distributions, vortices, power number, are predicted by large eddy simulation. Compared with Rushton turbine (RT) impeller when H/T=1 (or dual RTs when H/T=1.5, triple RTs when H/T=2), the HLF impeller can produce a flow field with more uniform distributions of larger velocities and TKE level. The HLF-2 impeller can further improve distribution uniformity of hydrodynamics in the case of high H/T. Power analysis shows that this is mainly due to the improved energy utilization efficiency by the fractal structure design.