Theoretical and experimental study on the effect of adjustable journal bearings on the vibration response of rigid and slender rotor systems

Adjustable/controllable bearings are the future direction of journal bearings and are used to correct design blind spots and handle changing operating conditions. This study investigates a clearance-adjustable bearing structure and its adjustment method to improve the operating stability of a rotor system under different working conditions. The theoretical model of this adjustable journal bearing was constructed and its lubricating characteristics under different clearances are analyzed. The Reynolds equation and the rotor dynamics equation were coupled to calculate the oil film force of the adjustable bearing introduced into the rotor system. The effect of the adjustable bearings on the dynamic response of the rigid rotor was investigated under different speeds and loads. Further, the adjustment methods required to improve the operation of the rigid rotor system were identified. Consequently, a finite element model of the adjustable bearing-rotor system was established to study the effect of the adjustable bearing on the dynamic behavior of the slender rotor system. In addition, the vibration response of the slender rotor within different speed regions was analyzed and the reasons for the change in amplitude owing to bearing clearance adjustment were explained. Furthermore, the corresponding test bench was constructed for experimental verification, and the essence of the adjustable bearing changing the dynamic response of the rotor system was described.