Advanced Instrumentation for Measuring Fluid-Structure Coupling Phenomena in the Guide Vanes Cascade of a Pump-Turbine Scale Model

In the present study, the fluid-structure coupling is investigated in the guide vanes of a pump-turbine scale model placed in one of the test rigs of the Laboratory for Hydraulic Machines (EPFL) in Lausanne. The paper focuses on the advanced instrumentation used to get reliable and complete fluid-structure coupling results. Semi-conductor strain gages are installed on three guide vanes which are especially weakened to account for stronger fluid-structure coupling phenomena. These are statically calibrated in terms of torsion torque and bending force. A laser vibrometer is used to measure the vibrating guide vane velocity. Piezo-resistive pressure sensors are placed around the weakened guide vanes to monitor the influence of the structural vibrations on the surrounding flow. A new non-intrusive excitation system is used to get the guide vanes impulse response. The instrument set enables a reliable fluid-structure coupling investigation in hydraulic pump-turbine scale model. Finally, the results show strong coupling between the vibrating guide vanes and the surrounding unsteady flow.