Analysis of bending and torsional vibration characteristics of rotor under the influence of air gap eccentricity-rub impact coupling fault

Abstract Considering the challenges posed by air gap compound eccentricity fault and rubbing fault in gas turbine generator groups, we undertake an analysis of the air gap magnetic field variation in the presence of air gap compound eccentricity. Leveraging the energy method of the air gap magnetic field, we establish a model for an unbalanced magnetic pulling force induced by air gap compound eccentricity. Concurrently, we develop a dynamic model for rotor rubbing fault, from which we derive the expression for rubbing force. Subsequently, we formulate the dynamic equations governing rotor systems afflicted with both unbalanced magnetic pull fault and rub-impact fault. Employing the 4-order Runge-Kutta method, we investigate the impact of mass eccentricity, static eccentric parameters, and dynamic eccentric parameters on the system’s dynamic response. Our findings reveal that mass eccentricity mitigates the impact of an unbalanced magnetic pulling force on the system. Additionally, the introduction of dynamic and static compound eccentricity significantly alters the system’s dynamic characteristics, leading to an increase in the components of multiple frequency doubling. These outcomes serve as a theoretical foundation for the design of rotor system structures and fault diagnosis methodologies.