Generation mechanism and noise suppression for the flow-excited resonance of shaftless pumpjet impellers
To cope with abnormal shaftless pumpjet noise with a high-frequency comb spectrum,we studied the cause and noise suppression characteristics of such a comb spectrum.First,by analyzing the comb spectrum of the radiated noise and the direction pattern of the thruster vibration,the source of the comb spectrum was confirmed to be closely related to the pumpjet impeller.Second,a one-way fluid-structure coupling analysis verified that the ab-normal spectrum at high frequency was generated by the two-bend in-plane bending modal resonance of the impeller because of flow excitation.Third,a scheme for welding a circular plate in the impeller passages was chosen to strengthen the blade.The results from fluid-structure interaction analysis and experimental measurement show that the sound and vibration levels of a shaftless pumpjet with a strengthened impeller were considerably reduced,and the abnormal comb spectrum was suppressed.Compared with the original design,the noise level was reduced from 25.2 to 30.2 dB at different frequencies,and no noise transfer to another frequency range was observed.