Power and flow characteristics of flexible-blade Rushton impeller

doi:10.11949/0438-1157.20190960

Abstract

Abstract:

Based on the traditional Rushton impeller, a flexible-blade Rushton impeller was developed. The emphasis was layed on characterization of the power and flow characteristics of this flexible-blade Rushton impeller. The power consumption as well as laminar and turbulent flow fields was numerically investigated by using the computational fluid dynamics (CFD) technique. Besides, they were experimentally validated by employing the dynamic torque sensor and particle image velocimetry (PIV), respectively. The results show that, when the viscosity of the fluid medium is close to that of glycerin, rubber can be used as the material for making flexible blade for the experimental scale stirred vessel. Power consumption of flexible-blade impeller is greater than the rigid impeller when Reynolds number is no more than 100. However, after that value, with the increase of Reynolds number, flexible-blade impeller consumes less power. The fluid-structure interaction (FSI) makes the flexible blades adaptable to the agitated fluid by deformation and accordingly, increases the radial flow capacity of the fluid. Specifically, when the viscosity fluid is low, flexible blade impeller can improve velocity of fluid near the blade and improve circulation capacity of fluid away from the impeller. When the agitated fluid has high viscosity, flexible-blade impeller can increase fluid velocity both near and far from the blade. As far as tailing vortex is concerned, flexible-blade impeller produces small magnitude vortex and is less energy consuming.

Key words: stirred vessel, flexible-blade Rushton impeller, power consumption, flow field, experimental validation, computational fluid dynamics

摘要：

基于传统的Rushton桨，开发了一种柔性叶片Rushton搅拌桨。采用数值模拟方法研究了柔性桨的功耗及层流和湍流流场特性，并分别采用扭矩测量法和粒子图像测速法进行了实验验证。结果表明，对于实验规模的搅拌容器，当介质黏度与甘油接近时，可用橡胶作为柔性桨叶制作材料。Reynolds数≤100时，柔性桨的功耗大于刚性桨；Reynolds数大于该值后，柔性桨的功耗小于刚性桨。柔性桨叶对被搅拌流体具有自适应特性，流固耦合作用下产生的变形增加了流体的径向流动能力。搅拌低黏度流体时，柔性桨能提升近桨区流体的速度，增加桨叶远端流体的循环流动能力；搅拌高黏度流体时，近桨区和桨叶远端流体的速度均大于刚性桨。就尾涡而言，柔性桨产生的涡量较小，耗能少。

关键词: 搅拌容器, 柔性Rushton搅拌桨, 功耗, 流场, 实验验证, 计算流体力学

CLC Number:

TQ 027

Fengling YANG, Cuixun ZHANG, Tenglong SU. Power and flow characteristics of flexible-blade Rushton impeller[J]. CIESC Journal, 2020, 71(2): 614-625.

杨锋苓, 张翠勋, 苏腾龙. 柔性Rushton搅拌桨的功耗与流场特性研究[J]. 化工学报, 2020, 71(2): 614-625.

Figures/Tables 17

References 30

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柔性桨叶材料	物性参数
柔性桨叶材料	弹性模量 E/MPa	泊松比	密度 ρ/(kg·m ^-3)
超高分子量聚乙烯	1~1.25×10 ⁵	0.3	935~945
硬聚氯乙烯	3.14~3.92×10 ³	0.319	1350~1400
橡胶	7.8	0.47	900~1000
硅橡胶	2.1	0.48	1200

柔性桨叶材料	物性参数
柔性桨叶材料	弹性模量 E/MPa	泊松比	密度 ρ/(kg·m ^-3)
超高分子量聚乙烯	1~1.25×10 ⁵	0.3	935~945
硬聚氯乙烯	3.14~3.92×10 ³	0.319	1350~1400
橡胶	7.8	0.47	900~1000
硅橡胶	2.1	0.48	1200

Reynolds数	转速 N/ (r·s ^-1)	密度 ρ/ (kg·m ^-3)	动力黏度 μ/(Pa·s)	搅拌介质
10	0.5	1263.3	1.412	甘油
40	2	1263.3	1.412	甘油
100	5	1263.3	1.412	甘油
254	2	1236.79	0.219	90%甘油水溶液
906	2	1210.28	0.060	80%甘油水溶液
2367	2	1183.77	0.023	70%甘油水溶液
4735	4	1183.77	0.023	70%甘油水溶液
11196	0.5	998.2	0.001	水
44784	2	998.2	0.001	水
111961	5	998.2	0.001	水

Reynolds数	转速 N/ (r·s ^-1)	密度 ρ/ (kg·m ^-3)	动力黏度 μ/(Pa·s)	搅拌介质
10	0.5	1263.3	1.412	甘油
40	2	1263.3	1.412	甘油
100	5	1263.3	1.412	甘油
254	2	1236.79	0.219	90%甘油水溶液
906	2	1210.28	0.060	80%甘油水溶液
2367	2	1183.77	0.023	70%甘油水溶液
4735	4	1183.77	0.023	70%甘油水溶液
11196	0.5	998.2	0.001	水
44784	2	998.2	0.001	水
111961	5	998.2	0.001	水

Reynolds数	功率准数 N _P
Reynolds数	刚性桨（模拟）	刚性桨（实验）	柔性桨（模拟）	柔性桨（实验）
10	5.779	6.241	6.198	6.570
40	2.921	3.184	3.350	3.618
100	2.545	2.723	2.569	2.749
254	2.339	2.573	2.213	2.412
906	2.035	2.198	1.794	1.973
2367	1.755	1.913	1.452	1.597
4735	1.500	1.604	1.253	1.353
11196	1.445	1.560	1.237	1.324
44784	1.291	1.408	1.170	1.240
111961	1.204	1.325	1.190	1.297