Design of impeller blades for fluid laminar mixing in an unbaffled stirred reactor

Background: Many studies reported that the isolated zones are obstacles for the fluid laminar mixing process. The key to intensify the laminar mixing process lies in minimizing or eliminating the isolated zone while maximizing the chaotic mixing zone. In this work, dislocated fractal impeller (DF impeller) was applied to minimize the isolated zone and maximize the chaotic mixing zone for fluid laminar mixing process. Methods: The mixing performance of dislocated pitched-blade impeller (DPB impeller) and DF impeller were explored through numerical simulation and experimentation. Significant findings: Results showed that the impeller blades with dislocated fractal structure design resulted in a reduction in power consumption and power number compared to the straight impeller blades with the same blade area. Meanwhile, this design could improve the shear action of impeller blade edges on the fluid, enhance the radial and axial velocity, and minimize the pressure differential between its front and rear sides while reducing the recirculation zone behind the impeller blades compared to straight impeller blades under the same operating conditions. In addition, DF impeller could decrease mixing time, reduce the isolated zone and increase the chaotic mixing zone compared with DPB impeller under the same operating conditions.