The pod propeller shaft receives many excitations during operation, so there are complex vibration forms. When the vibration of the shaft is severe, it will not only reduce the concealment and comfort of the ship, but may even cause the motor rotor and stator to collide, which seriously endangers safety of motor operation. Therefore, studying vibration characteristics and transmission mechanism of pod propeller shaft is of great significance for reducing vibration and ensuring the safety of ship operation. Based on the analytical method, this paper establishes the dynamic model of the pod propeller shaft system, bearings are simplified to springs, and the propeller is simplified to a concentrated mass with the moment of inertia, the boundary conditions and the continuity conditions of each shaft section are given, thus an effective analytical calculation method for pod propeller shaft vibration characteristics is formed. The unbalanced propeller rotation and the deformation of pod propeller cabin are considered as excitations on the shaft system. The transverse and longitudinal vibration characteristics of pod propeller shaft has been analyzed. The mainly conclusions are as follows: propeller excitation has a greater impact on the shaft transverse vibration in the low-frequency range; the frequency of each resonant peak of longitudinal vibration is relatively large; the excitations transmitted by the bearings will cause a large vibration amplitude of the motor shaft. This research provides theoretical support for the design and optimization of the pod propeller.

Ship power system,Propulsion shaft,Dynamic responses,Ship,Podded propulsors