Methods For The Vibration And Noise Prediction Of Marine Gear Box And Structure Design For Noise Reduction

The 21^st century maritime Silk Road is a part of the Belt and Road strategy and has become an important national stategy.As the core equipment to support the national maritime strategy,ships are always given priority to develop in our country.Vibration and noise not only affect the comfort of ships,but also threaten their stealth.Gear transmission is widely used in marine propulsion system because of its advantages such as high power/weight radio,high reliability,long life and etc.However,vibration and noise can be produced during the working process of gear box which is one important component in gear transmission.This vibration and noise is one of the main sources of vibration and noise in ships.Therefore,the study of how to predict the vibration and noise of marine gear box accurately and reduce it effectively has great significance.In this study,the vibration and noise prediction method of marine gear box considering the admittance of base is built and validated by experiment,and the influence of admittance of base on the vibration and noise of gear box is analyzed using this method.The structure design method for the noise reduction is proposed and validated by experiment,and the radiated noise of a gear box is reduced by using this method.The main research works and achievements are as follows:1.The estimate and control methods of vibration and noise of marine gear box are summarized and evaluated.The results show current research is insufficient in some aspects such as how to consider the influence of admittance characterstic of base on the vibration and noise of marine gear box,the structure design method for the noise reduction and etc.2.Combined with finite element method?FEM?/boundary element method?BEM?and dynamic substructure method,the vibration and noise prediction method of marine gear box which can consider the admittance of base is built.In this method,the base is equivalent and the finite element model/boundary element model of base is avoided to build.So this method is more efficient and has a wider range of application than the full FEM/BEM.The vibration and noise of a single stage double helical gear box which is mounted on a base is simulated using this method.The test rig is built and the vibration and noise of this gear box is measured.The accuracy of the proposed method is verified by comparing the measured vibration and noise with the simulated ones.It is found that the self admittance of base should be considered preferentially during the vibration and noise simulation of marine gear box.3.The effects of admittance of base on the vibration and noise of gear box are analyzed.The results show the self admittance of base has more remarkable influence on the vibration and noise of gear box than the mutual admittance.The greater the admittance of base is,the more remarkable influence on vibration and noise of gear box it has.If the acceleration produced by the self admittance and the mutual admittance has opposite phase,the acceleration on the connection point will have a minimum value as the change of admittance of base.4.The distribution of acoustic transfer vector?ATV?is studied.It is found the higher the frequency is,the more dispersed the distribution of ATV is.For a field point,the ATV on the surface which opposite the field point is larger than the ATV on other surfaces.The effects of gear box structure on ATV are analyzed.The results show as the change of rib layout,the variation of the value of ATV is not more than 30%and the distribution of ATV has no significant change.5.Based on acoustic contribution analysis and topology optimization,the topology optimization design method for the noise reduction is proposed.In this method,the region having maximum acoustic contribution can be determined by ATV analysis,modal acoustic contribution analysis?MACA?and panel acoustic contribution analysis?PACA?firstly.Then the topology optimization model can be established to reduce the velocities on this region.Finally the ribs can be arranged according to the optimal topologies.The rib layout on a plate which is fixed along all side is designed using this method.Four plates are manufactured according to different rib layouts.The radiated noise of each plate is measured and the effectiveness of the proposed method is verified by comparing the measured radiated noise.6.The structure design procedure for the noise reduction of marine gearbox is proposed and the structure design of the single stage double helical gear box is completed.The results show after structure design,the radiated noise on the whole sound field is reduced.The average equivalent sound pressure level on the main field points is reduced by 4.98dB?A?and the maximum equivalent sound pressure level is reduced by 9.44dB?A?.Finally,some conclusions and comments are given and the further research works are pointed out.