Vibration analysis of coupled bending-torsional rotor-bearing system for hydraulic generating set with rub-impact under electromagnetic excitation

Based on Jeffcott rotor model, the coupled bending-torsional rotor-bearing system with rub-impact under electromagnetic excitation for hydraulic generating set is established and the corresponding equation is given. The influence of excitation current, mass eccentricity and electromagnetic torque in the system is investigated by taking use of numerical method. The simulation results show that eccentricity is the crucial factor causing the changes of system dynamic characteristics, compared to the effect of torsional degree of freedom. And the larger the eccentricity is, the more obviously it affects the system responses. While the complicated dynamic behavior of bending vibration response can be restrained, due to the introduction of torsion motion, which has the property to suppress complex dynamic response of system, particularly, the inhibited and improved effect is more evident, as the eccentricity turns to be smaller. In addition, the unstable jumping phenomena of torsional response can be motivated by electromagnetic torque, which has to be taken seriously during the process of model establishment and dynamic analysis of system. From the global view of electromechanical coupling characteristics, the coupled bending-torsional vibration model with rub-impact under electromagnetic excitation can supply a more comprehensive reflection about the dynamic characteristics of system and provide useful reference with system state recognition and fault diagnosis.