A Flexible Rotor on Flexible Bearing Supports: Part II — Unbalance Response
Abstract An experimental study of the effects of bearing support flexibility on rotor unbalance response is presented. A flexible rotor supported by fluid film bearings on flexible supports was used with fifteen support configurations. The horizontal support stiffness was varied systematically while the vertical stiffness was kept constant. The support characteristics were determined experimentally by measuring the frequency response functions of the support structure at the bearing locations. These frequency response functions were used to calculate polynomial transfer functions that represented the support structure. The second critical speed of the rotor varied from 3690 rpm to 5200 rpm, depending on the support configuration. The predicted first critical speeds agree with the experimental data within −1.7%. The predicted second critical speeds agree with the experimental data within 3.4%. Predictions for the rotor on rigid supports are included for comparison.