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Flows in Complex Systems

Effects of Blade Wrap Angle Influencing a Pump as Turbine

[+] Author and Article Information
Sun-Sheng Yang1

 Research Center of Fluid Machinery Engineering and Technology,  Jiangsu University, Zhenjiang, Jiangsu, 212013, Chinayangsunsheng@126.com

Fan-Yu Kong

 Research Center of Fluid Machinery Engineering and Technology,  Jiangsu University, Zhenjiang, Jiangsu, 212013, Chinakongm@ujs.edu.cn

Hao Chen, Xiang-Hui Su

 Research Center of Fluid Machinery Engineering and Technology,  Jiangsu University, Zhenjiang, Jiangsu, 212013, China

1

Corresponding author.

J. Fluids Eng 134(6), 061102 (May 29, 2012) (8 pages) doi:10.1115/1.4006677 History: Received March 22, 2012; Revised April 17, 2012; Published May 29, 2012; Online May 29, 2012

A pump is not ideally designed to operate as a turbine. To improve the efficiency of a pump as turbine (PAT), the redesign of the PAT, according to the flow of the turbine, is required. The blade wrap angle is one of the main geometric parameters in impeller design. Therefore, an investigation into the blade wrap angle to the PAT’s influence can be useful. In order to understand blade wrap angle to the influence of the PAT, this paper numerically investigated three different specific speeds of PATs with different blade wrap angles. The validity of numerical simulation was first confirmed through a comparison between numerical and experimental results. The performance change of the PATs with the blade wrap angle was acquired. A detailed hydraulic loss distribution and a theoretical analysis were performed to investigate the reasons for performance changes caused by the blade wrap angle. The results show that there is an optimal blade wrap angle for a PAT to achieve the highest efficiency and the optimal blade wrap angle decreases with an increasing specific speed. A performance analysis shows the PAT’s flow versus pressure head (Q-H) and flow versus generated shaft power (Q-P) curves are lowered with the decrease of the blade wrap angle. The hydraulic loss distribution and theoretical analysis illustrate that it is the decrease of hydraulic loss within the impeller, together with the decrease of the theoretical head, that results in the performance decrease. The decrease of hydraulic loss within the impeller is attributed to the shortened impeller blade passage and the reduced velocity gradient within the impeller flow channel. With the decrease of the blade wrap angle, the slip factor of the PAT’s impeller is decreased; therefore, its theoretical head is also decreased.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Impellers of different specific speeds

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Figure 2

Division of 3-D model within the PAT’s control volume

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Figure 4

An open PAT test rig

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Figure 6

Experimental and numerical results

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Figure 7

Performance curves of PATs with different blade wrap angles

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Figure 8

Flow zones in a PAT control volume

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Figure 9

Hydraulic loss distribution within the investigated PATs

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Figure 10

Difference of the hydraulic loss distribution with different blade wrap angles

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Figure 11

Velocity distribution of the PATs with different blade wrap angles

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