长短叶片复合型刚柔桨强化搅拌槽内流体混沌混合行为

doi:10.11949/0438-1157.20200225

化工学报 ›› 2020, Vol. 71 ›› Issue (11): 5080-5089.DOI: 10.11949/0438-1157.20200225

长短叶片复合型刚柔桨强化搅拌槽内流体混沌混合行为

刘作华^1,³(),魏红军^1,³,熊黠^1,³,陶长元^1,³,王运东²,程芳琴⁴

^1.重庆大学化学化工学院，重庆 400044
^2.清华大学化学工程系，北京 100084
^3.煤矿灾害动力学与控制国家重点实验室，重庆大学，重庆 400044
^4.山西大学资源与环境工程研究所，山西太原 030006

收稿日期:2020-03-04 修回日期:2020-05-18 出版日期:2020-11-05 发布日期:2020-11-05
通讯作者: 刘作华
作者简介:刘作华（1973—），男，博士，教授，liuzuohua@cqu.edu.cn
基金资助:
国家重点研发计划项目(2017YFB0603105);国家自然科学基金项目(21636004);重庆市教委科学技术研究计划项目重点项目(KJZD-M201900101);重庆市技术创新与应用示范专项产业类重点研发项目(cstc2018jszx-cyzdX0085)

Chaotic mixing performance enhanced by rigid-flexible impeller with long-short blades in stirred tank

Zuohua LIU^1,³(),Hongjun WEI^1,³,Xia XIONG^1,³,Changyuan TAO^1,³,Yundong WANG²,Fangqin CHENG⁴

^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:2020-03-04 Revised:2020-05-18 Online:2020-11-05 Published:2020-11-05
Contact: Zuohua LIU

摘要/Abstract

摘要：

搅拌反应器中混合隔离区的存在是强化流体混合的主要障碍。打破搅拌槽中的对称性流场结构，破坏混合隔离区，可以提高流体混合效率。采用Matlab软件编程计算最大Lyapunov指数（LLE）和多尺度熵（MSE），比较了不同桨叶类型、柔性片长度、柔性片数量和桨叶离底高度以及转速对流体混合的影响。结果表明，长短叶片复合型刚柔桨（RF-LSB）桨叶通过刚柔耦合错位连接，柔性片的形变与随机振动对流体的非稳态扰动，使流场结构不稳定性和不对称性增强，强化了流体混合效果。当柔性片数量为3，搅拌转速为90 r/min时，RF-LSB体系比刚性桨和刚柔桨体系的LLE值分别提高了20.22%和7.98%；三种体系[RF-LSB（柔性片数量为3）、刚性桨和刚柔桨体系]的混合时间（θ_m）与单位体积功耗（P_v）呈指数型关系，当P_v相同时，RF-LSB（柔性片数量为3）的θ_m最小，表明RF-LSB（柔性片数量为3）更有利于流体混沌混合。

关键词: 长短叶片复合型刚柔桨, 最大Lyapunov指数, 混沌混合, 多尺度熵

Abstract:

The presence of a mixing isolation regions in a stirred reactor is a major obstacle to enhancing fluid mixing. Breaking the symmetrical flow field structure in the stirred tank and destroying the mixing isolation area can improve the fluid mixing efficiency. The Matlab software was used to calculate the maximum Lyapunov exponent (LLE) and multi-scale entropy (MSE). The effects of different blade types, flexible blade length, flexible blade number, blade height from bottom and rotation speed on fluid mixing were compared. The results show that the rigid-flexible impeller with long-short blades (RF-LSB) can enhance the flow field structure more unstable and asymmetric with deformation and random vibration of flexible pieces, destroy the symmetry flow in the process of fluid mixing, induce the asymmetric flow field, and make more fluid into the chaotic state. When at 90 r/min and three pieces of flexible, the LLE of the RF-LSB is larger than that of rigid impeller and rigid-flexible impeller RF-LSB with increase of 20.22% and 7.98% respectively. The mixing time (θ_m) of the three systems [RF-LSB (three pieces), rigid impeller, rigid-flexible impeller] has an exponential relationship with the power consumption per unit volume (P_v). When P_v is constant, θ_m of the RF-LSB system is the smallest. Results showed that the RF-LSB (three pieces) is superior to rigid impeller and rigid-flexible impeller, which is more conducive to fluid chaotic mixing.

Key words: rigid-flexible impeller with long-short blades, largest Lyapunov exponents, chaotic mixing, multi-scale entropy

中图分类号:

TQ 027.2

刘作华,魏红军,熊黠,陶长元,王运东,程芳琴. 长短叶片复合型刚柔桨强化搅拌槽内流体混沌混合行为[J]. 化工学报, 2020, 71(11): 5080-5089.

Zuohua LIU,Hongjun WEI,Xia XIONG,Changyuan TAO,Yundong WANG,Fangqin CHENG. Chaotic mixing performance enhanced by rigid-flexible impeller with long-short blades in stirred tank[J]. CIESC Journal, 2020, 71(11): 5080-5089.

图/表 10

图1 搅拌实验装置1―frequency conversion motor; 2―programmable logic controller; 3―stirring shaft; 4―baffle; 5―impeller; 6―computer; 7―data acquisition card; 8―gas distributor

Fig.1 Mixing experimental apparatus

图2 实验所用桨叶类型

Fig.2 Impellers used in experiment

图3 单位体积功耗分析

Fig.3 Analysis of power consumption per unit volume

图4 搅拌桨类型对θm的影响

Fig.4 Effect of impeller types on θm

图5 柔性片数量对θm的影响

Fig.5 Effect of flexible piece number on θm

图6 三种体系θm随Pv的变化

Fig.6 θmof three systems at different Pv

图7 搅拌桨类型对LLE的影响

Fig.7 Effect of impeller types on LLE

图8 等转速下最大Lyapunov指数分析

Fig.8 Analysis of LLE under constant speed

图9 搅拌桨类型对MSE的影响

Fig.9 Effect of impeller types on MSE

图10 等转速下多尺度熵分析

Fig.10 Analysis of MSE under constant speed

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长短叶片复合型刚柔桨强化搅拌槽内流体混沌混合行为

Chaotic mixing performance enhanced by rigid-flexible impeller with long-short blades in stirred tank

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