Research On Vibration And Noise Reduction Method For High Power Marine Gearbox Housing Structure

As one of the main noise sources of ship power transmission,the vibration and noise of gearbox have great influence on the ship’s concealment and performance.Most of the noise emitted by the gearbox radiates outward in the form of structural noise,so it is of great significance to analyze the acoustic vibration characteristics of the gearbox and then reduce its vibration and noise level.In this paper,a large complex gearbox is studied.According to the analysis results of acoustic vibration characteristics,the vibration and noise reduction is achieved by reinforcing the box body and adding damping.The geometric model of the large complex gearbox housing is simplified,the modal of the gearbox housing is analyzed,and the characteristics of the modal of the gearbox are studied.Based on the theory of modal superposition,the acceleration vibration stages of critical response points under simple harmonic excitation are calculated.The velocity boundary conditions of acoustic analysis are established and the noise radiation characteristics of the gearbox are obtained by using the boundary element method.The acoustic plate contribution of the gearbox is analyzed,and the position that contributes more to the acoustic power of the gearbox is taken as the key optimization area.Considering the gearbox housing is composed of thin-walled structure,establishment of stiffened plate model,the analysis about the quantity,location and size of the steel structure of the influence of acoustic vibration characteristics,found that the reinforcement of thin plate structure has good vibration damping noise reduction effect,which based on the advantage of the modal vibration mode optimizing the section size of stiffener location,increase muscle(height,width),the increase of reinforcement ratio can reduce structural vibration and noise level different level.The damping is added to the plate to verify the accuracy of the damping composite model.The influence of damping material parameters on the structure is studied and the damping material is selected accordingly.The modal damping ratio of different types of damping structures with different base thickness and damping thickness is calculated.The analysis shows that the damping effect of constrained damping is better than that of free damping.The damping laying is determined according to the acoustic plate contribution principle.According to the analysis results of stiffeners and dampers on the characteristics of thin-walled structures,the box bodies with different quantities,positions and sizes of stiffeners were first established,and the form of stiffeners was determined by comparing the vibration and noise levels at a specific frequency range(447～562Hz).Secondly,damping was laid at the position where the acoustic contribution of the box was large.The vibration and noise reduction effects of the composite box with different damping thicknesses were analyzed,and the optimization scheme was finally determined.Compared with the original box,its total sound power level decreased by 12.6d B and average acceleration level decreased by 17.8d B.