New paper published: Experimental study on the detection of vibrations of an operating turbine runner with sensors on the casing
Feb 11, 2025
Keywords: Francis turbine, Modal behavior, Natural frequencies, Piezo patches, Condition monitoring, Stationary sensors
Mònica Egusquiza from CDIF-UPC has recently published a paper in collaboration with the Centre d'Innovation en Hydroélectricité (HEKI) from Université Laval. This study, developed under the Tr-Francis project, demonstrates that natural frequencies of Francis runners undergo a splitting phenomenon during operation and that these frequencies shift when measured from the casing. This effect was experimentally observed and analytically demonstrated in a disk by CDIF-UPC in 2015. This research enhances our understanding of how resonances in hydraulic turbines can be triggered and detected using stationary sensors.
Abstract:
Hydraulic turbine runners experience strong vibrations in operation, especially when resonances between runner natural frequencies and hydraulic excitations occur. Precise determination of prototype runner frequencies in operation is essential, but direct measurements are costly and technically challenging.
This study presents an experimental investigation on a reduced-scale Francis model to evaluate the use of non-intrusive stationary sensors to measure runner vibrations. The runner was instrumented with accelerometers and piezoelectric patches, and an accelerometer was installed on the casing. The natural frequencies of the operating runner were excited with the patches and the vibration was measured simultaneously in the rotating and stationary structures.
Results prove the feasibility of monitoring runner vibrations externally and demonstrate the correlation between rotating and stationary frames. Runner natural frequencies change and split due to confined rotation. The stationary sensor measures them with a frequency shift depending on rotating speed and nodal diameters of the excited mode shape.
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