Effects of axial positions of bearings on the whirling vibration of ship propulsion shafting: Numerical and experimental investigations

Suppression of whirling vibration is essential for the safe and stable operation of ship propulsion shafting systems. However, the mechanisms by which the axial positions of bearings influence the whirling vibration characteristics of ship propulsion shafting have not yet been fully elucidated. Therefore, using a ship propulsion shafting test bench as the study object, this research investigates the effects of the axial positions of different bearings on the whirling vibration characteristics of the shafting through numerical analysis. Furthermore, whirling vibration experiments are conducted using position-adjustable bearing pedestal assemblies with the bearings positioned at various axial locations, allowing validation of the numerical results. The results indicate that, while having a negligible effect on the natural frequencies and critical speeds, appropriately displacing the front stern bearing and the intermediate bearing toward the stern end can effectively reduce the whirling vibration response of the shafting under steady-state operating conditions. Moreover, adjustment of the front stern bearing produces a more pronounced vibration suppression effect than adjustment of the intermediate bearing. These findings provide valuable guidance for the control of whirling vibration and the optimal arrangement of bearings in ship propulsion shafting.