Vibration characteristics analysis of shaft system for bulb hydroelectric generating unit based on magnetorheological fluid damper

Abstract

In order to reveal the influence law of magnetorheological fluid damper on shaft system vibration for bulb hydroelectric generating unit, based on the modified LuGre friction model, the rub-impact dynamic model of magnetorheological fluid damper-rotor-runner-bearing system is established considering multi-effect of unbalanced magnetic pull, oil film force, and unbalanced hydraulic excitation. The suppression pattern of passive control for the magnetorheological fluid damper on vibration from rotor as well as runner under different rotating speed and mass eccentricity is investigated by using numerical method, and the stability of periodic solution for system is analyzed combined with Floquet theory. Models with and without magnetorheological fluid damper are studied, and the results show that the nonlinear dynamic characteristics of bulb hydroelectric generating unit, can be significantly improved by valuable passive control from magnetorheological fluid damper damping. The system response becomes orderly due to the existence of magnetorheological fluid damper, which can attenuate vibration generated during the parameters variation including rotating speed and mass eccentricity, with trend towards synchronous periodic motion form. Magnetorheological fluid damping passive control has good applicability to bulb hydroelectric generating unit, which can provide a conducive reference for shaft system vibration reduction of unit.