Study On The Influence Of Longitudinal Resonance Changer Thrust Bearing On Vibration And Noise Of Hull Structure

A resonance changer with dynamic tuning function is added to the thrust bearing,which can control the longitudinal vibration of the propulsion shaft by controlling the vibration transmission at the thrust bearing.This structure can be called resonance changer thrust bearing.It is difficult to simulate the elastic boundary of the hull under laboratory conditions.The structural parameters of resonance changer thrust bearing are usually designed using the vibration characteristics of the propulsion shaft system under the rigid boundary conditions,and the vibration reduction effect is evaluated.Because the coupling between the propulsion shaft system and the hull cannot be ignored,in order to promote the engineering application of the resonance changer thrust bearing,it is particularly important to analyze the vibration reduction effect under the elastic boundary condition of hull and its influence on the underwater low-frequency radiated noise of hull structure.In this paper,the finite element model of the hull and the resonance changer thrust bearing is established.Combined with related theories,the numerical simulation method is used to study the vibration and noise of hull with resonance changer thrust bearing.The contents include analysis of vibration characteristics of hull structure,analysis of the influence of resonance changer thrust bearing on vibration and noise characteristics of hull structure and analysis of the influence of resonance changer thrust bearing on the vibration energy transferred from each bearing.Firstly,based on the principle of vibration reduction of resonance changer thrust bearing,the element types that should be used in finite element modeling are explained.The vibration characteristics of the propulsion shafting under the rigid boundary condition and the elastic boundary condition of the hull are analyzed by using the finite element coupled acoustic boundary element method.The influence of the longitudinal vibration of the propulsion shafting on the vibration characteristics of the hull is dominant at its natural frequency.The resonance changer thrust bearing can control the vibration transmitted to the hull through the propulsion shafting and then control the underwater low-frequency radiated noise generated by the hull.Then,by studying the influence of the resonance changer thrust bearing on the vibration response of the hull structure and radiated noise,the relationship between vibration and noise and the mechanism of vibration reduction and noise reduction of the resonance changer thrust bearing are analyzed.The results show that the trend of the vibration and radiated noise of the hull is the same as the vibration of the thrust bearing.The resonance changer thrust bearing designed according to the rigid boundary condition can reduce the peak value of vibration and noise of the hull,and has the effect of vibration and noise reduction.The influence of the resonance changer thrust bearing on the acoustic vibration characteristics of the hull structure can be divided into stiffness area,antiresonance area and mass area.The structural parameters of the resonance changer,the longitudinal stiffness of the thrust bearing and the thickness of the hull shell are changed.The variation law of hull vibration and sound power is analyzed.The influence of various structural parameters on the radiated noise of the hull with the resonance changer thrust bearing is predicted.The results show that increasing the mass ratio of the resonance changer,reducing the longitudinal rigidity of the thrust bearing,and increasing the thickness of the hull shell have a positive effect on vibration and noise reduction.Finally,from the perspective of energy transfer the power flow method based on the finite element method is used to explain the influence of the resonance changer thrust bearing on the vibration transmitted from the propulsion shaft system to the hull.The results show that the resonance changer consumes the vibration energy transmitted from the propulsion shaft system to the hull and redistributes the vibration energy transmitted from each bearing to the hull.