多叶片组合式搅拌桨釜内流动特性和混合性能研究

doi:10.11949/0438-1157.20200795

摘要/Abstract

摘要：

开发可适用于较宽黏度范围的搅拌桨，强化釜内的流体流动和混合过程对于搅拌釜的节能增效具有重要的意义。实验与数值模拟相结合，在大涡模拟层面研究了多叶片组合式搅拌桨（MBC桨）从层流到湍流状态下，釜内的功率特性、流场分布、湍流特性和混合性能。结果表明：预测的功率曲线与实验结果一致；层流状态下釜内以切向流动为主，随着Reynolds数（Re）的增大，釜内轴向和径向流动逐渐增强，当Re达到486时，速度场分布与湍流状态下基本一致；在相同的能耗水平下，MBC桨对高黏度流体的混合性能优于商业Maxblend桨。桨叶的分散组合布置，强化了釜内的轴向和径向流动，使得MBC搅拌桨在从过渡流到湍流状态下均可实现较大的轴径向流动，湍动能分布较为均匀，混合过程显著加快。

关键词: 混合, 多叶片组合式搅拌桨, 计算流体力学, 过渡流, 层流

Abstract:

Developing an agitator suitable for wide viscosity range is of great significance to the energy saving and efficiency improvement by the intensification of fluid flow and mixing process. The power characteristics, flow field distribution, turbulence characteristics and mixing performance of multi-blade combined (MBC) agitator under laminar to turbulent flow state were studied experimentally and numerically at the level of large eddy simulation. The predicted power curve is consistent with the experimental results. Tangential flow is the main flow in laminar flow. With the increase of Reynolds number (Re), axial and radial flows in the vessel gradually increase. When Re reaches 486, the velocity field distribution is basically the same as that in the turbulent flow. At the same energy consumption level, MBC agitator is superior to the commercial Maxblend agitator in mixing high viscosity fluid. The intensification of axial and radial flows is due to the dispersed arrangement of the blades, enabling the MBC agitator to achieve larger axial and radial flows from the transitional flow to the turbulence state. Moreover, the turbulent kinetic energy is evenly distributed and the mixing process is significantly accelerated.

Key words: mixing, multi-blade combined agitator, computational fluid dynamics, transitional flow, laminar flow

中图分类号:

TQ 028.8

许言,王健,武永军,骆培成. 多叶片组合式搅拌桨釜内流动特性和混合性能研究[J]. 化工学报, 2020, 71(11): 4964-4970.

Yan XU,Jian WANG,Yongjun WU,Peicheng LUO. Study on the flow characteristics and mixing performance of multi-blade combined agitator[J]. CIESC Journal, 2020, 71(11): 4964-4970.

图/表 9

图1 多叶片组合式搅拌桨1—固定环；2—连接叶片；3—长叶片；4—短叶片

Fig.1 Multi-blade combined agitator

图2 计算网格示意图

Fig.2 Diagram of computational grids

表1 模拟流体物性参数（20℃）

Table 1 Physical parameters of the simulated fluid

模拟流体	密度/ (kg·m^-3)	黏度/ (Pa·s)	转速/ (r·min^-1)	Reynolds数
77%(质量)玉米浆水溶液	1300	9.77	120	2.7
70%(质量)糖浆水溶液	1341	0.31	120	87
55%(质量)糖浆水溶液	1250	0.0257	60	486
甘油	1300	1.055	20~300	4.1~61.7
水	998	0.0010	90	14928

图3 MBC搅拌桨功率准数曲线

Fig.3 Power number curve of MBC agitator

图4 不同流动状态下无量纲速度矢量图和时均速度云图

Fig.4 Dimensionless velocity vectors and contour plots of mean velocity under different flow states

图5 不同流动状态下两个径向位置处（r/R=0.6,0.8）无量纲轴向、径向和切向速度分布

Fig.5 Profiles of the dimensionless axial, radial and tangential velocities at two radial positions (r/R=0.6, 0.8)

图6 不同流动状态下的P45平面上无量纲湍动能分布云图

Fig.6 Contours of the predicted dimensionless turbulent kinetic energy on the plane of P45

图7 层流区域搅拌釜内死区体积随Re的变化曲线

Fig.7 Curve of dead zone volume ratio vs. Reynolds number in the laminar flow region

图8 Maxblend搅拌桨和MBC搅拌桨混合过程浓度场分布比较(P/V=148 W·m-3)

Fig.8 Comparison of concentration field changes in the mixing process stirred by Maxblend agitator and MBC agitator(P/V=148 W·m-3)

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