Investigation of the Intensified Chaotic Mixing and Flow Structures Evolution Mechanism in Stirred Reactor with Torsional Rigid-Flexible Impeller

Abstract

This investigation addresses the development of a Möbius strip with torsional structure as the flexible connection pieces for rigid-flexible impellers, enhancing the macroinstability of the flow field structure, the fluid transfer efficiency, and the chaotic mixing degree in the stirred tank. The effects of intrinsic parameters, including the impeller types and length and width of the flexible connection piece among impellers on the laminar flow field were explored. In addition, the chaotic characteristic parameters, helicity distribution, vorticity distribution, flow field structure evolution, power consumption, and fluid velocity of different rigid-flexible impeller systems were investigated as well. The experiment and computational fluid dynamics calculations demonstrated that the DRFMSC-PBDT system with torsional structure has better mixing characteristics at a lower level for power consumption, being clearly superior to DRFC-PBDT and DRFTSC-PBDT in the LLE and NTm values. The torsional structure of the Möbius strip could facilitate strengthening to form the axial circulation of the flow field, decreasing mass transfer resistance and destroying the stability of the flow field structure while contributing to improving the mixing efficiency of the system. In addition, the enhanced superior proportion of the stagnant zone and the mixing zone is also attributed to the increased secondary flow, as well as the generated perturbation wave with larger amplitude and smaller frequency, which are responsible for mixing in laminar flows.