Investigation and optimization into flow dynamics for an axial flow pump as turbine (PAT) with ultra-low water head

•Energy loss at the draft tube directly affects the performance of the axial flow PAT.•The separation position of the TLV influences the energy loss at the runner.•Blade angles affect the efficiency of the runner and energy loss at the draft tube.•The runner with reasonable blade angles can improve...

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Veröffentlicht in:Energy conversion and management 2024-08, Vol.314, p.118684, Article 118684
Hauptverfasser: Zhu, Zehui, Gu, Qi, Chen, Hongxun, Ma, Zheng, Cao, Baohua
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Sprache:eng
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Zusammenfassung:•Energy loss at the draft tube directly affects the performance of the axial flow PAT.•The separation position of the TLV influences the energy loss at the runner.•Blade angles affect the efficiency of the runner and energy loss at the draft tube.•The runner with reasonable blade angles can improve the performance of PAT. When the water downstream is abundant, axial flow pumps are often used as turbines (PAT) for reverse power generation to obtain additional benefits. However, due to the actual water level difference, PAT usually operates at off-design conditions. The CFD technology and entropy production theory were used to study the working performance, flow characteristics, and energy loss mechanism of the blade adjustable axial-flow PAT under a low water head. The results indicate that the strength of the tubular vortex at the pressure surface and the separation position of the tip-leakage-vortex at the suction surface depend on the inlet angle of the blade. The energy loss in the draft tube is influenced by the velocity circulation at the runner’s outlet, which depends on the blade’s outlet angle. Subsequently, the blade inlet and outlet angles in the runner were optimized. In turbine mode, the overall efficiency of the optimized runner increased by an average of 0.99 %. The blade pressure load distribution of the optimized runner has improved, and the pressure fluctuation in the draft tube is also under control. In pump mode, due to the increasing of the inlet angle within the same demand pump head range, the optimized runner’s pumping flow increases by an average of 2 m3/s.
ISSN:0196-8904
DOI:10.1016/j.enconman.2024.118684