Study on vibration transmission characteristics of integrated vibration isolation system for marine thrust bearings

  Objectives   The Integrated Vibration Isolation System (IVIS) for marine thrust bearings can be used to change the longitudinal vibration transmission path of the propulsion shafting system and attenuate the vibration energy transmitted from the propeller to the hull, thereby achieving the purpose of noise reduction.

  Methods   In order to obtain the transmission rules of the propeller excitation in different directions, a numerical analysis model of the propeller-shaft-hull was established. Then, the vibration transmission characteristics of the IVIS under the propeller's unit excitation forces in the longitudinal and lateral directions were analyzed. Under these two installation methods of thrust bearings, i.e. by means of the IVIS and the traditional rigid support, the vibration responses of the hull were compared and the corresponding dominant modes were identified. In addition, the longitudinal force spectrum of the propeller was calculated by indirect identification method, and the vibration isolation performance of the IVIS was evaluated by using it as an input. Finally, the experimental study on the response characteristics resulting from the propeller excitation of the IVIS was carried out.

  Results   The results show that, compared with the traditional rigid support method, the IVIS has no obvious vibration isolation effect for the propeller's lateral excitation force, but has a vibration isolation effect of more than 10 dB for the longitudinal excitation.

  Conclusions   The application of the IVIS can generate satisfactory vibration isolation effect of the marine thrust bearings in longitudinal direction, and this result can provide a new method for the design of marine thrust bearing vibration isolation devices。