Hydrodynamics of a Pump-Turbine at Off-Design Operating Conditions: Numerical Simulation

Flow numerical simulations in a low specific speed radial pump-turbine scale model are performed to investigate off-design operating conditions in generating mode. The Best Efficiency Point (BEP) and the runaway operating conditions at 10° guide vanes opening are addressed. The computational domain includes the full reduced scale model water passage from the spiral casing inlet to the draft tube outlet. The numerical simulation is performed using the Ansys CFX code, solving the incompressible unsteady Reynolds-Averaged Navier-Stokes equations. Wall pressure measurements in the stator are used to validate the numerical results. Then, detailed analysis is focused on the onset of the flow instabilities when the machine is brought from BEP to runaway. In these severe operating conditions, one single stall cell is found to rotate with the impeller at subsynchronous speed in the vaneless gap between the impeller and the guide vanes. It is found to be the effect of flow separation developed at the inlet of several consecutive impeller channels which lead to their blockage.

Published in:
Proceedings of ASME-JSME-KSME Joint Fluids Engineering Conference 2011
Presented at:
ASME-JSME-KSME Joint Fluids Engineering Conference 2011 - 7th International Symposium on Pumping Machinery, Hamamatsu, Japan, July 24-29, 2011

Note: The status of this file is: EPFL only

 Record created 2011-06-30, last modified 2018-03-17

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