Vibration characteristics investigation of a dual rotor-bearing outer ring–pedestal-casing system with clearance fit.

Due to thermal expansion of the mechanical structure, assembly processes, bearing wear, and long-term vibration during operation, a clearance fit may occur between the bearing outer ring and its pedestal. The clearance fit may result in relative motion between the bearing outer ring and pedestal, thereby altering the support characteristics of the rotor and subsequently impacting the dynamic characteristics of the rotor-bearing system. The stable operation of the system may be at risk in this case. In this paper, the dynamic model of the coupling system of a dual rotor-bearing outer ring-pedestal-casing with clearance fit is established based on the finite element method and lumped parameter method. The dimensionality of the system equation is reduced using the fixed-interface component mode synthesis (CMS) method and solved numerically. The impact of clearance fit on the vibration characteristics of the system is investigated under three operational conditions: imbalance of the inner rotor, imbalance of the outer rotor, and simultaneous imbalance of both two rotors. Furthermore, an analysis is conducted to evaluate the motion state of the system with clearance fit. Lastly, the vibration transmission characteristics between the rotor-bearing outer ring-pedestal-casing are studied. The results indicate that the harmonic components corresponding to the rotational speed frequency of rotors will appear on the spectrum and envelope spectrum of the system with clearance fit. The natural frequency of the system may be excited in the resonance region. Due to the influence of gravity, the dynamic characteristics of the system vary significantly at low and high rotational speeds. Additionally, the vibration transmission characteristics of the system are significantly influenced by both the rotational speeds and clearance fit. [ABSTRACT FROM AUTHOR]