Study On Band Gap And Vibration Reduction Performance Of Sea Pipeline System Based On Periodic Structure

In recent years,with the effective control of the vibration of power equipment such as ship main and auxiliary machinery,the radiation noise problem of ship pipeline system has become increasingly prominent.The pipeline system is an important channel for the ship equipment to transmit energy and material,but the pipeline system will also transmit the vibration generated by the power equipment while playing the role of material transmission.In addition,the interaction between the fluid with large flow velocity and the pipe wall will also produce the problem of regenerative vibration noise.Therefore,it is of great significance to carry out the dynamic characteristics analysis and vibration reduction method research of ship sea pipeline system.In this thesis,the dynamic model of periodic pipeline system is established based on periodic structure and pipeline vibration theory.The elastic wave transmission characteristics of periodic pipeline system and the influence of related parameters on band gap are studied.The vibration reduction effect of periodic structure in fluid-solid coupling pipeline model is analyzed.Finally,a set of pipeline system models are designed and processed,and experimental verification is carried out.The main research contents and conclusions of this thesis are as follows:(1)Based on the bending vibration dynamic equation of pipeline system and the basic theory of phononic crystals,the elastic wave transmission characteristics and energy band structure of Bragg periodic pipeline and locally resonant periodic pipeline are studied.The results show that the band gap range of Bragg periodic pipeline and local resonance periodic pipeline obtained by numerical calculation is consistent with the peak frequency band of the vibration level drop curve obtained by simulation analysis.(2)Taking the locally resonant periodic pipe as the main research object,the influence of structure and material parameters on the band gap of periodic pipe is analyzed.The results show that the increase of lattice constant and oscillator width will increase the band gap width,thus improving the vibration reduction effect of the pipeline system,but has little effect on the initial frequency of the band gap.The increase of the thickness of the inner and outer rings can effectively reduce the starting and ending frequency of the band gap,but the improvement of the vibration reduction effect will gradually weaken.The bandwidth of the inverted trapezoidal local oscillator is higher than that of the traditional local oscillator,and the band gap center frequency is also reduced by 16 Hz.The arrangement of local oscillators of various sizes can form a ’band gap fusion’ phenomenon in the pipeline system.While maintaining the cutoff frequency of the band gap,the band gap width can be increased by up to 10 Hz,and the starting frequency of the band gap can be reduced to 18 Hz.(3)For the fluid-solid coupling locally resonant periodic pipeline structure,the effects of initial surface pressure and fluid velocity on the band gap characteristics and vibration reduction performance of the pipeline system are studied.The results show that the increase of initial gauge pressure and fluid velocity will lead to the aggravation of the vibration of the pipeline system,and the local resonance periodic structure can effectively reduce the vibration of the output end of the pipeline.With the increase of initial gauge pressure and fluid velocity,the vibration reduction effect of locally resonant periodic structure will also be improved.When the initial gauge pressure is 100 k Pa and the fluid flow rate is 10 m / s,the average displacement of the output end of the periodic pipeline is reduced by 76.1 % and68.3 % respectively.(4)A periodic pipeline system was built and its vibration characteristics were tested.A set of periodic pipeline models were designed and processed,and a vibration reduction performance test system was built.The vibration transmission characteristics of the localized periodic pipeline were studied.At the same time,the ’band gap fusion’phenomenon of the localized resonance periodic pipeline was verified by experiments.The results show that the total vibration level drop of the periodic structure pipeline is 1.6 d B higher than that of the ordinary pipeline in the range of 10 Hz～200 Hz,and the experimental results are consistent with the simulation analysis.The research conclusions of this thesis can provide reference for the vibration reduction design of ship sea pipeline.