EQUIVALENT SUPPORTING POINT OF MISALIGNED STERN TUBE BEARING AND ITS EFFECT ON WHIRLING VIBRATION OF SHAFTING

摘要

Marine stern tube bearings support propeller shafts stretching outside the ship. The gravity of propeller leads to journal misalignment in vertical direction. In rotor dynamic analysis, bearings are usually simplified as equivalent supporting points with stiffness. The vertical misalignment of journal moves the equivalent supporting point away from the axial midplane. The accuracy of the bearing's equivalent supporting point location influences the reliability of the results of rotor dynamic analysis. In this paper, a solving approach of equivalent supporting point location is given, the equivalent supporting point location of a misaligned stern tube bearing is obtained, and the natural frequency and mode shape of the propeller shaft are analyzed. The results show that, bearing's misalignment leads the equivalent supporting point moving to the down-warping end. The influence of bearing misalignment on natural frequency and mode shape of stern shaft is nonnegligible.