Research On Impedance Homogenization Of A Ship Base

The broadband excitation generated by the mechanical equipment in the ship will inevitably cause the vibration of the hull structure.The broadband excitation vibration,in the form of elastic waves,will transmit through the base,deck and finally to the surface of the hull.Then the hull will be excited and radiate noise to the surrounding fluid medium.The equipment base is the primary link between the mechanical equipment and the hull structure which impedance characteristics directly reflect its ability to block equipment vibration.Therefore,with the use of the base impedance as the target parameter in the design of the high-efficiency isolation base is one of the most effective measures to reduce ship vibration and noise.This paper aims to reduce the vibration and acoustic radiation of ship,innovatively proposes the design concept of base impedance homogenization,through theoretical analysis,numerical calculation and experimental verification means.The analysis of homogenization design aims to provide new ideas and references for improving the vibration isolation performance of the equipment base and reducing the level of ship vibration and noise.Firstly,this paper sorts out the current high-efficiency vibration reduction and isolation technology of ship bases through investigating related documents,introduces the vibration energy suppression measures in the existing research.In addition,it summarizes the research status of the impedance optimization design of the base structure,analyzes the limitations of the current base impedance design method,and then leads to the main research content and direction of this paper,which lays the base for the follow-up work.Secondly,around the optimization design of the base impedance,the research on the traditional vibration isolation mechanism of equipment and the new mechanism based on waveform conversion was carried out.At the same time,based on the basic principles of mechanical impedance,the calculation method of the coupling impedance of the ship structure and the base is studied.Some numerical examples about the base under the typical reinforced form are given in order to investigate the relation between the homogenization of the impedance and the vibration isolation performance.After that,the design concept and evaluation index of the homogenization of the impedance of the base are proposed.Thirdly,based on impedance homogenization technology,a new type of impedance homogenization base design model is proposed,which contains the vibration isolation liquid layer and discontinuous base panel.These components are used to control the surface wave wavelength in the base structure and achieve the purpose of vibration reduction.Furthermore,the influence of design variables such as liquid layer characteristic parameters and arrangement schemes on the vibration characteristics of the base is explored,which provides support for the systematic application process in actual ships.Fourthly,a research of real ship application with the base impedance homogenization technology is carried out.The new impedance homogenization base above-mentioned is applied to the typical floating raft system and investigated the vibration reduction effect comparing with traditional base.The systemized application process in the real ship,and the recommended value range of the parameters in the design is given.On this basis,using the real-scale cabin as the research object,the change of radiated noise verifies systematic application process and the effectiveness of impedance homogenization technology.Fifthly,considering the simulation errors caused by the properties of the liquid bag and the connection of the impedance homogenized base,experiment method is used in this chapter.It compares the vibration isolation effect of traditional base with the new impedance homogenization base containing liquid vibration isolation layer under the action of excitation force and torque,which is further verifies the effectiveness of the base impedance homogenization technology for ship vibration and noise reduction.This paper focuses on ship vibration and noise reduction,explores the relationship between low-noise ship structure design and the homogenization of base impedance,and innovatively proposes the concept of impedance homogenization design of the base.Based on this concept,a new liquid-containing impedance homogenization base is designed.Then,the research on the influence of relevant characteristic parameters on the vibration isolation characteristics of the base,and the systemic application process of the impedance homogenization technology of the base in the actual ship are studied.The application effect analysis and effectiveness verification test provide a certain reference value for the practical engineering application of ship base impedance homogenization design.