Energy loss mechanism due to tip leakage flow of axial flow pump as turbine under various operating conditions

Kan Kan, Qingying Zhang, Zhe Xu, Yuan Zheng, Qiang Gao, Lian Shen

Research output: Contribution to journalArticlepeer-review

70 Scopus citations

Abstract

Owing to its ability to handle large flows, an axial flow pump as turbine (PAT) can generate considerable amounts of electricity in small-scale hydropower plants. However, a PAT's efficiency can be hindered by tip leakage flow (TLF), namely, flow through the clearance between the impeller blade tip and shroud. Accordingly, this study investigates the influences of TLF on the PAT's energy performance through numerical simulations in which the entropy production method has been adopted. TLF and the associated tip leakage vortex (TLV) are found to both decrease the hydraulic efficiency and increase the flow rate; the shaft power output is also affected, especially near the machine's best efficiency point. The effect of TLF on the pressure distribution along the blade depends on the flow conditions, and the form of the TLV directly generated by TLF is affected by the flow incidence angle. The vorticity transport equation reveals that the vortex stretching term plays a dominant role in the spatial evolution of the TLV and has the greatest impact on the pressure distribution. Finally, different operating conditions lead to different energy loss mechanisms: turbulent dissipation is the main cause of energy loss, and high flow conditions are marked by an increase in TLF-dependent wall shear stress dissipation.

Original languageEnglish (US)
Article number124532
JournalEnergy
Volume255
DOIs
StatePublished - Sep 15 2022

Bibliographical note

Funding Information:
This study was supported by the National Natural Science Foundation of China ( 52009033 ), the Natural Science Foundation of Jiangsu Province ( BK20200509 ), the Fundamental Research Funds for the Central Universities ( B210202066 ). The computational work was supported by High Performance Computing Platform, Hohai University, China . The support of Hohai University , China is also gratefully acknowledged.

Publisher Copyright:
© 2022 Elsevier Ltd

Keywords

  • Axial flow pump
  • Entropy production
  • Pump as turbine
  • Tip clearance
  • Tip leakage flow
  • Vorticity transport equation

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