CIESC Journal ›› 2020, Vol. 71 ›› Issue (10): 4621-4631.doi: 10.11949/0438-1157.20200313

• Fluid dynamics and transport phenomena • Previous Articles     Next Articles

Experiment and numerical simulation of chaotic mixing performance enhanced by perturbed rigid-flexible impeller in stirred tank

Zuohua LIU1,3(),Hongjun WEI1,3,Xia XIONG1,3,Changyuan TAO1,3,Yundong WANG2,Fangqin CHENG4   

  1. 1.School of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China
    2.Department of Chemical Engineering, Tsinghua University, Beijing 100084, China
    3.State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
    4.Institute of Resources and Environment Engineering, Shanxi University, Taiyuan 030006, Shanxi, China
  • Received:2020-03-24 Revised:2020-04-26 Online:2020-10-05 Published:2020-05-25
  • Contact: Zuohua LIU E-mail:liuzuohua@cqu.edu.cn

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Abstract:

To eliminate the isolated mixing regions in the stirred tank, factors associated with chaotic mixing performance were studied, including flow field structure and fluid velocity of rigid RT impeller (R-RT), perturbed rigid RT impeller (PR-RT) and perturbed rigid-flexible RT impeller (PRF-RT). The maximum Lyapunov exponent (LLE) and multi-scale entropy (MSE) were calculated by using Matlab software programming, and the differences in flow field structure and fluid velocity of the three blade systems were studied through computational fluid mechanics. The experimental and computational results showed that perturbed rigid-flexible RT impeller could destroy the boundary of the mesostatic flow field in the isolated mixing regions and the symmetry flow in the process of fluid mixing through the random disturbance of the flexible blade, eliminating the isolated mixing regions. At 90 r/min, the LLE of the perturbed rigid-flexible RT impeller is larger than that of rigid RT impeller and perturbed rigid RT impeller. The LLE of the rigid-flexible RT impeller compared with the rigid RT impeller and perturbed rigid RT impeller increases 13.29% and 7.25% respectively and the MSE of the perturbed rigid-flexible RT impeller is also larger than that of rigid RT impeller and perturbed rigid RT impeller. The perturbed rigid-flexible RT impeller enhances the flow field instability, forms an asymmetric flow field structure, and reduces the distribution range of isolated mixing regions. The perturbed rigid-flexible RT impeller enhances the energy dissipation of the blade, improves the fluid velocity at the bottom and top of the tank and the wall of the tank, and reduces the mixing time.

Key words: perturbed rigid-flexible impeller, largest Lyapunov exponents, multi-scale entropy, numerical simulation

CLC Number: 

  • TQ 027.2

Fig.1

Mixing experimental apparatus and mesh model"

Fig.2

Impellers used in experiment and impeller size"

Fig.3

Grid independence (R-RT)"

Fig.4

Effect of impeller types on θm"

Fig.5

Effect of impeller types on LLE"

Fig.6

Flexible pieces shape in experiment"

Fig.7

Effect of flexible piece shape on LLE"

Fig.8

Effect of impeller types on MSE"

Fig.9

Effect of flexible piece shape on MSE"

Fig.10

Effect of impeller types on P"

Fig.11

Effect of impeller types on contour plots of velocity magnitude"

Fig.12

Effect of impeller types on the area size of fluid moving speed (V≤0.20 m/s)"

Fig.13

Effect of impeller types on velocity magnitude of axial direction"

Fig.14

Effect of impeller types on velocity magnitude of radial direction"

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