Model updating for rotor-discs system and its application in dynamic coefficients identification of journal bearings

An accurate finite element (FE) model of the rotor-discs system is essential on the field identification of dynamic coefficients for journal bearings. This paper proposes a novel model updating method using the measured modal parameters. In this method, system mass and stiffness matrices were firstly updated by the particle swarm optimization (PSO) algorithm, in which the sensitivity analysis was used to select the appropriate variables to be optimized. Based on the updated results, the damping matrix defined as an improved Rayleigh Damping was then determined according to the experimental modal frequencies and damping ratios. To evaluate the effectiveness of this method, the FE model of a dual rotor-discs system was updated. The frequencies responses predicted by the updated model perform a good agreement with that from measured. Moreover, to validate the reliability of the updated model, the identifications of the dynamic coefficients were conducted on the flexible rotor test rig experimentally. The results demonstrated that the updated model has higher accuracy in field identification of dynamic coefficients than the original model, especially the system under critical speed. This study provides a feasibility strategy for updating the rotor-discs system and thereby establishes a foundation for further parameters identification and dynamic analysis.