Flow determination of a pump-turbine at zero discharge

27th IAHR Symposium on Hydraulic Machinery and Systems

Edinger, G.^1 ; Erne, S.^2 ; Doujak, E.^1 ; Bauer, C.^1

Vienna University of Technology, Institute for Energy Systems and Thermodynamics, Department of Fluid-Flow Machinery, Getreidemarkt 9/302, Vienna

1060, Austria^1

Voith Hydro GmbH and Co. KG, Linzer Straße 55, St. Pölten

3100, Austria^2

关键词: Experimental investigations;    Gate openings;    Pressure fluctuation;    Pump-turbines;    Separated flows;    Three-dimensional flow;    Vaned diffuser;    Zero discharge;   

Others  :  https://iopscience.iop.org/article/10.1088/1755-1315/22/3/032051/pdf
DOI  :  10.1088/1755-1315/22/3/032051

来源: IOP

【 摘 要 】

When starting up a reversible Francis pump-turbine in pump mode, the machine may operate at zero flow at a given gate opening. Besides reversal flow and prerotation in the draft tube cone, the onset of a fully separated flow in the vaned diffuser is observable at zero- discharge condition. In this paper, the occurrence of prerotation and reversal flow in the conical draft tube and the flow in one stay vane channel of a pump-turbine are examined experimentally and compared to numerical simulations. In order to assess the strongly three-dimensional flow in the stay vane channel, measurements with a 2D laser doppler velocimeter (LDV) were performed at various positions. The inlet flow in the draft tube cone, which becomes significantly at zero discharge in pump mode, is investigated by velocity measurements at two different positions. Pressure fluctuations in the draft tube cone induced by complex flow patterns are also recorded and analyzed. It is found that the swirl number at zero discharge does not significant differ from the values obtained at very low load pumping. Experimental investigations combined with CFD have shown that in the stay vane channel flow velocity components different from zero occur even at no discharge. Streamline plots show the fully separated flow structure.