Comparative study of the flow characteristics in several frame-type impeller stirred tanks

doi:10.11949/0438-1157.20200910

Abstract

Abstract:

The flow characteristics in a stirred tank equipped with traditional frame impellers, the traditional frame combined impeller and the new frame type combined impeller was investigated by particle image velocimetry (PIV) measurements. The velocity, flow pattern and turbulent kinetic energy of the three type of frame impellers in a stirred tank was compared under the same experimental and working condition. The results show that the fluid flow of the traditional frame impeller in stirred tank is mainly horizontal circulation, and fluid flow is insufficient in the upper and middle part of the frame impeller. Due to the two-fold-blade impeller, the fluid velocity in upper part of the traditional frame combined impeller is increased, the fluid flow in the upper and lower parts of the tank is strengthened, but there is still dead mixing zone at the center of the frame impeller. For the new frame type combined impeller, the connecting flow between the two layers of blades in the stirred tank is enhanced. The exchange of material and energy between the bottom and the middle area of the frame impeller is more sufficient. The comparison results show that the new frame type combined impeller has the best mixing performance among the three types of frame impellers. The research results can provide reference for the application of the new frame type combined impeller in the polyester synthesis industry.

Key words: new frame type of combined impeller, mixing, flow field, stirred tank, particle image velocimetry(PIV)

摘要：

用粒子成像测速（PIV）技术对传统框式桨、传统框式组合桨和新型框式组合桨的流动特性进行研究，对比了三种框式桨在相同工况下搅拌槽内的速度、流型和湍动能。结果表明：传统框式桨搅拌槽内流体流动以水平环流为主，在框式桨上方和框式桨中间区域流体流动不充分；传统框式组合桨搅拌槽内框式桨上方由于二折叶桨的作用使得框式桨上部流体流速变大，槽内流体上下部的流动得到加强，但在框式桨中心区域依旧存在流动死区；新型框式组合桨搅拌槽内两层桨叶间的连接流得到了加强，框式桨底部和中间区域物质和能量的交换更加充分。在考察的三种框式桨中，新型框式组合桨的混合效果更好。研究结果可为新型框式组合桨应用于化工合成工业中提供参考。

关键词: 新型框式组合桨, 混合, 流场, 搅拌槽, 粒子成像测速

CLC Number:

TQ 027

LI Wenjin, ZHOU Yongjun, YUAN Mingyue, HE Hua, SUN Jianping. Comparative study of the flow characteristics in several frame-type impeller stirred tanks[J]. CIESC Journal, 2021, 72(4): 1998-2005.

李文金, 周勇军, 袁名岳, 何华, 孙建平. 几种框式桨搅拌槽内流动特性的比较研究[J]. 化工学报, 2021, 72(4): 1998-2005.

Figures/Tables 8

Fig.1 Square slot model

Fig.2 Structure and dimension of mixing tank and impellers

Table 1 Main operating parameters of stirred tank and impellers

参数	数值/mm
H	675
T	430
D₁	330
D₂	330
d	240
d₂	100
C₁	100
C₂	310

Fig.3 Structure of three impellers

Fig.4 Velocity contour in the mixing tank of three impellers

Fig.5 Comparison of axial velocities of three impellers in different radial positions

Fig.6 Flow pattern in the mixing tank with different impellers

Fig.7 Turbulent energy cloud of three impellers

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