Author(s): M Zorn; J Ada; L Auch; E Micciche; S Riedelbauch; C Gouveia; A Oliveira

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Abstract: The introduction of hydraulic short circuit operation in existing pumped-storage power plants increases their flexibility but may cause unfavourable flow conditions at pipe junctions, head or tailwater reservoirs. Consequently, this operation is investigated for the Alqueva II power plant by means of CFD simulations prior to on-site tests as the outlets of the draft tubes are positioned very close to each other. The simulations, that are initially carried out using a single-phase approach, show that the tailwater level as well as the configuration, which of the two pump-turbines is operated in pump or turbine mode, influences the flow field in the tailwater reservoir and thus, the inflow conditions for the pumping unit. With the pump-turbine located further away from Alqueva I running as a turbine and the tailwater level at minimum level, the least favourable flow field is present. The initial choice of the single-phase setup is confirmed by the results of two-phase simulations. Moreover, the flow behaviour observed during the on-site tests is similar to the results of the CFD simulations. The on-site tests successfully demonstrate the capability of Alqueva I and II to be operated in hydraulic short circuit for all configurations.

DOI: https://doi.org/10.1088/1755-1315/1483/1/012020

Year: 2023