Self-excitation in Francis runner during load rejection

[摘要] Typically, transients such as load rejection generate only a few high vibration cycles in Francis runners. However, in the cases presented in this study, a sustained vibration around a natural frequency was observed on three (3) homologous Francis runners of different sizes during such events. The first two (2) runners were equipped with strain gauges on the blades and displacement sensors positioned circumferentially in the bottom ring and head cover around the runner labyrinth seals. The third runner was monitored only with displacement sensors on non-rotating components. The data from the first two (2) runners provided a better understanding of the parameters influencing the appearance of the high amplitude vibrations and allowed the implementation of a test plan to circumvent the phenomenon during commissioning of the third runner. Based on the measured data, the distributor's closing parameters were optimized to eliminate the vibration observed during load rejection on most of the operating range and reduce it significantly at full load.

[发布机构] Alstom Renewable Power Canada, 1350 Chemin St-Roch, Sorel-Tracy; QC; J3R 5P9, Canada^1;Institut de Recherche d'Hydro-Québec (IREQ), 1800 Lionel-Boulet, Varennes; QC; J3X 1S1, Canada^2

[关键词] Different sizes;Displacement sensor;High-amplitude vibrations;Labyrinth Seal;Load rejections;Operating ranges;Self excitation;Vibration cycle