Author(s): Jean Decaix; Olivier Pacot; Mathieu Mettille; Cecile Munch-Alligne

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Abstract: Due to the changes in the electricity market, the hydraulic turbines are more and more used to balance the grid, which requires to operate the machines at off design operating points. In the framework of the HydroLEAP Swiss project, aiming at upgrading the hydro-power plants in Switzerland to successfully matching the Energy strategy 2050 of the Confederation, a double Francis turbine at prototype scale has been simulated. Due to the implementation of the turbine above the free surface level of the tail race channel, cavitation occurs for all operating points. Therefore, cavitation simulations have been performed including surface roughness, and the results are compared with on-site measurements. The main goal is to provide an overview of the most critical operating points in terms of instabilities such as pressure and force fluctuations or cavitation erosion, which impact the lifetime of the turbine. The unsteady simulations are performed using the Ansys CFX software for four operating points: deep part load, part load, best efficiency point and full load. The analysis of the converged statistics shows that the part load operating point is the one for which the pressure, runner torque and axial force standard deviations are the highest. Whereas the full load operating point is characterized by a large standard deviation of the outlet pressure. These results are correlated by the vibration content index derived from on-site measurements.

DOI: https://doi.org/10.1088/1755-1315/1561/1/012001

Year: 2025