| Ventilation ducts were widely used in ships as an important structure to improve the living environment of cabins.However,since pipelines can become carriers for transmitting vibration and noise,domestic and foreign scholars have done a lot of research on the vibration and noise control of pipelines.In this paper,the experimental methods were used to explore the vibration damping and noise reduction performance of the blocking joint and the plug-in resistive muffling tubes,and combined with theoretical analysis and simulation methods to analysis their working principles.In this paper,I also explored the feasibility of using acoustic metamaterials in pipelines.The research focus of this paper was as follows:Firstly,based on the Euler-Bernoulli theory of the rod class,the wave equation of the pipeline was derived,and then the vibration transmission loss of the pipeline was calculated after installing the rigid blocking joint.Three kinds of rigid blocking joints were designed and the vibration transmission loss and insertion loss of each joint were tested by designing experiments.The vibration damping performance of each group of rigid blocking joints was simulated by COMSOL software,which was found that the simulation results were in good agreement with the experiments,and the correctness of the simulation settings was verified about the rigid blocking joints.Based on the results of rigid joints,an elastic composite blocking joint was designed and its vibration-damping performance was explored.By simplifying the elastic composite type blocking joint into a mass-damping-stiffness system,the four-terminal parameter method was used to derive the transmission loss of the elastic composite type blocking joints in the pipeline and the design experiment to tested their value of transmission loss.According to experimental results found that the elastic composite type blocking joint has better vibration damping effect.Secondly,based on finite element method(FEM),hybrid method(FE-SEA)and statistical energy method(SEA),VA-one software was used to predict acoustic effects after installing the plug-in resistive muffling tubes in the pipeline at 100-5000 Hz.According to the effects of different material thicknesses,different sound absorbing materials,and the airflow state and the airless state,the noise reduction of muffing tubes were studied respectively,and related experiments were designed according to the boundary conditions of the simulation.Finally,the accuracy of the simulation was verified by the experimental results.And then,the structure of the ventilation duct and the cruise cabin all were established.The noise sound pressure level in the cabin before and after the installation of the muffling tube was predicted,which was found that the acoustic environment of the cabin after the installation of the muffling tube was better.Finally,based on COMSOL software,the sound absorption coefficients of two acoustic metamaterials were calculated.And the transmission loss of the two acoustic metamaterials was compared,which was found that the sound absorption type acoustic metamaterial has better acoustic performance under the same conditions of film area and mass size.Based on the above research,the noise reduction effect simulation model of the sound absorbing metamaterial in the pipeline was designed and the simulation results of the model were analyzed and summarized.Through the research work in this paper,the understanding of the vibration-damping performance of the blocking joint was deepened.At the same time,the silencing mechanism of the plug-in resistive muffling tubes and the acoustic metamaterial was deeply discussed,and the influence of relevant parameters on the vibration-damping performance of the joint,the muffling performance of the muffling tubes and the noise reduction performance of the acoustic metamaterial were revealed respectively,it has certain reference value for damping and noise reduction of ventilation ducts. |
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