Theoretical study on the axial excitation force transmission characteristics of marine propellers

Abstract

There are many researches on exciting forces of propellers. However, most of them have not studied their transmission characteristics (the influence of elastic blades, flexible shafts and bearings on forces during their transmission to the hull). Therefore, in this study, the transmission characteristics of axial exciting force of propellers are studied based on a FSI dynamic model of the fluid-propeller-shaft-bearing system which is established by coupled BEM and FEM. The research results show that elastic blades and the flexible shaft have an important effect on axial exciting force during its transmission to the hull. First, there are two kinds of vibration modes for blade bending vibration, one is jellyfish mode and the other is non-jellyfish mode. The axial exciting force has resonance peak only in the jellyfish mode. Second, the elastic coupling effect between the propeller and the shaft has large effect on the jellyfish mode and has small influence on the non-jellyfish mode. Finally, all these results are validated with analytical solution by simplifying the propeller-shaft-bearing system into a series of mass-spring models. This study can provide theoretical guidance for the optimal design of propeller-shaft-bearing system and minimize the excitation force transmitted to the hull.