Experimental study of hydrodynamic characteristics of cycloidal propeller and vibration characteristics of central shaft bearing

This paper presents an experimental study on the hydrodynamic characteristics of a six-bar linkage cycloidal propeller and the vibration characteristics of the central shaft bearing. A vertical circulating water channel-based experimental platform for cycloidal propeller performance is constructed, which introduces the key-phase detection technology for the first time, enabling the simultaneous acquisition of hydrodynamic and vibration data within a single rotation cycle at a low cost. On this basis, the platform is used to systematically investigate the influence of different operating parameters on the hydrodynamic characteristics of the pendulum propulsion and the vibration characteristics of the central shaft bearing. Preliminary tests show that the torque coefficient of the six-bar linkage cycloidal propeller increases with the azimuthal angle under 5°, 15° and 25° azimuthal angles, which is mainly attributed to the intensification of cavitation phenomenon. The amplitude spectrum of the thrust-induced excitation force shows significant peaks at the BPF (Blade Passing Frequency) and at twice the BPF under some operating conditions. Furthermore, the vibration spectrum of the central shaft bearing shows a significant response at twice the BPF, indicating that the thrust-induced excitation force directly affects the bearing vibration. The experimental data and regularity understanding obtained in this study are of great significance for the optimal design and stable operation of cycloidal propeller.