Propeller Shafting Dynamics Under Impulse Action

Abstract

Propeller shafts and countershafts are bent quite often on sea and river vessels. The cause of the curvature is a strong load on this node of the ship’s power plant. In addition to bending, the shafting experiences longitudinal and transverse loads with a dynamic and static component. A large number of scientific papers have been devoted to the study of the dynamics of the propeller and shafting. However, the problem has not been completely solved, and the increase in damages during the shafting operation and its intensive wear only confirm the relevance of further research in this direction. The aim of the work is to determine the dynamic forces in the shafting, which occur during impulse action due to the propeller impact on the ice. A model of a two-stage elastic rod with inert disks at the ends is presented in the paper. It allows considering different situations of dynamic impact on the shafting and propeller. The following design features such as different stiffness of the shaft sections, different speed of elastic waves of deformation (different densities and modules of elasticity on the shaft sections), reduced inertial load from the moving parts of the drive, can be taken into account in the model. It is concluded that the frequency of the main form of oscillations mainly depends on the inertial loads concentrated at the ends and the shaft rigidity. The proposed simplified model of the inertialess shaft makes it possible to determine the angles of rotation of the shaft sections with sufficient accuracy. For different sections of the stepped shaft, the dynamic torque coefficient can differ significantly.