Chaotic Mixing Intensification and Flow Field Evolution Mechanism in a Stirred Reactor Using a Dual-Shaft Eccentric Impeller

Nearly 95% of the energy in the stirred reactor maintains the symmetrical flow field structure formed by fluid rotation, which reduces the efficiency of fluid transfer. In this paper, a dual-shaft eccentric impeller based on the Rushton turbine (RT) and pitched blade Rushton turbine (PBRT) was proposed to eliminate the stable symmetrical flow field structure in the mixing tank and improve the fluid transfer efficiency and chaotic mixing degree. The effects of impeller types, the height difference between impellers, and shaft eccentricity on the single-phase flow field were researched. The power consumption, mixing time, chaotic characteristic parameter the largest Lyapunov exponents, flow field structure evolution, and fluid velocity of different dual-shaft eccentric impeller systems were also investigated through experiments and computational fluid dynamics simulation. Results showed that changing the impeller types and height difference on different shafts could improve the mixing efficiency at a lower power consumption incremental level. Meanwhile, both visual experiments and numerical simulation analysis demonstrate that the reasonable combination of the above two variables can make full use of the advantages of different impellers, strengthen the fluid transfer, destroy the symmetrical structure of the flow field in the stirred reactor, and enhance the energy dissipation of the system through the fluid transfer effect between blades and the coupling effect of height difference, which is conducive to improving the mixing efficiency of the system.

Automated summary

This study proposes a dual-shaft eccentric impeller to improve the flow field structure in a stirred reactor and enhance fluid transfer efficiency and mixing degree. The results show that changing the impeller types and height difference between shafts can improve mixing efficiency, as the reasonable combination of these variables can utilize the advantages of different impellers and disrupt the symmetrical flow field structure, enhancing energy dissipation and improving mixing efficiency.