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Q. Liang, M. Keller, M. Sick
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Published in:
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Proceedings of Hydro 2009, Lion, France
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Date:
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October 26 – 28, 2009
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The rapid availability of pumped storage schemes and the benefits to the power system by peak lopping (or peak shaving), by providing reserve and rapid response for frequency control are of great importance to a modern generation system [1, 2].
This mode of operation can arise for longer periods in pump turbines when running at speed in a no load condition with the generator not connected to the grid [3]. In this paper this mode of operation is denoted as the “speed no load” condition. From the point of view of fluid dynamics the speed no load operation is an unsteady condition with pressure pulsations and complex vortex structures [4]. This mode of operation is therefore impossible to simulate with steady state computational fluid dynamics [5].
Pressure pulsations occur mainly in the annular space between guide vanes and the runner. The unsteady CFD simulation of the rotor-stator interaction (RSI) in the turbine mode of a pump turbine and its validation with experimental results have already been presented [3, 6].
This method can also be applied in extreme part load and to the speed no load condition. While in this operation more complex flow phenomena start to play an important role [7], the rotor stator interaction is still the dominant factor.
The unsteady CFD simulation of the speed no load condition and its validation versus experimental results are presented in this paper. The numerically predicted pressure pulsations are compared to measurements on a test rig. Various numerical parameters such as grid size and boundary conditions are discussed. The good agreement between measurement and simulation shows the reliability of modern CFD methods for complex, unsteady flow structures. Limitations of the numerical prediction and further extensions of the CFD model are discussed.
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