Vibration Characteristics of a Specific Hydroelectric Generator Rotor Supported by Journal Bearings

To investigate the nonlinear lateral vibration characteristics of a large pumped-storage generator rotor supported by guide bearings, an efficient nonlinear time-domain analysis framework was developed. A three-dimensional finite-element model containing 46,788 degrees of freedom was established by considering gyroscopic effects, rotor unbalance, and nonlinear oil-film forces described by the Capone short-bearing model. A speed-dependent Craig–Bampton reduction method with matrix interpolation was combined with the Newmark-β method and Newton–Raphson iteration. By retaining eight internal modes, the model was reduced to 17 generalized degrees of freedom, corresponding to a model-size reduction of 99.96%, while the maximum relative error of the first seven natural frequencies remained below 1% over 0–1000 r/min. In a numerical comparison of the two solution schemes at 500 r/min, the Newton–Raphson scheme required 8.1 s, compared with 23.9 s for the lagged-update scheme, reducing the computation time by 66.1%. At the rated speed of 375 r/min, increasing the bearing radial clearance or decreasing the lubricant viscosity increased the journal vibration amplitude and orbit area. Within the investigated parameter ranges, the system maintained stable single-period responses, with the rotational-frequency component remaining dominant. The proposed framework provides an efficient approach for the nonlinear dynamic analysis of large pumped-storage rotor-bearing systems.