期刊
ENERGY
卷 255, 期 -, 页码 -出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.energy.2022.124532
关键词
Axial flow pump; Pump as turbine; Tip leakage flow; Tip clearance; Vorticity transport equation; Entropy production
资金
- National Natural Science Foundation of China [52009033]
- Natural Science Foundation of Jiangsu Province [BK20200509]
- Fundamental Research Funds for the Central Universities [B210202066]
- High Performance Computing Platform, Hohai University, China
- Hohai University, China
The study found that tip leakage flow (TLF) and the associated tip leakage vortex (TLV) can affect the performance of PAT, decreasing hydraulic efficiency, increasing flow rate, and affecting shaft power output. The effect of TLF on the pressure distribution along the blade depends on flow conditions, while the form of TLV is influenced by the flow incidence angle.
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. (C) 2022 Elsevier Ltd. All rights reserved.
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