Excitation force on a pump-jet propeller: The clocking effect of pre-swirl stator

The impact of the clocking effect of the pre-swirl stator on the excitation force of a pump-jet propeller is investigated in this paper. The clocking effect, a common concept in fluid machinery, is applied and extended to the relative circumferential position between the pre-swirl stator and the submarine hull in this paper. The research is conducted using computational fluid dynamics (CFD) and water tunnel experiments. The CFD results demonstrate that the clocking effect exerts a negligible influence on the steady performance of the pump-jet. However, the excitation force of the rotor is greatly influenced by it. This is due to the fact that the stator, when positioned at various clocking positions, generates different wakes that change the amplitude and phase distribution of the rotor strips' excitation force. Furthermore, the experimental results demonstrate that the influence of the clocking effect on the duct vibration and the noise radiated by the pump-jet should not be ignored, the trend of which is consistent with that of the excitation force obtained by CFD, thereby establishing a clear correlation between the excitation force and the vibration and noise level. This paper is of guiding significance for the low-noise design of submarine pump-jets.