Noise Reduction Analysis Of Fairing Based On Porous Media

In the launch of the launching stage,the carrier rocket was inspired by more than 150 d B,and its harsh acoustic vibration environment caused the internal equipment structure to be affected by the internal sound pressure field of the fairing.In order to prevent damage to the internal parts,the sound pressure level of the fairing must be reduced.The noise inside the fairing can be greatly reduced by sticking porous ceramic fiber material inside the fairing.The random fiber modeling method is used to reconstruct the microstructure of porous fibers and generate three-dimensional random micro geometry models.The effects of fiber diameter and porosity on the sound absorption and insulation properties of three-dimensional random structures were calculated by finite element method,which provides a reference for the design of porous ceramic fiber materials.Firstly,according to the acoustic simulation research of acoustic-vibration coupling theory,the sound insulation amount of the structure is calculated.The random fiber generation algorithm is used to reconstruct the three-dimensional random microscopic geometry of porous ceramic fiber materials.The low Reynolds number viscous flow equation,the inertia equation of non-viscous flow and the Poisson equation related to heat dissipation were established respectively.Through COMSOL software,the 3D random geometric model was simulated and solved to establish the JCA acoustic equivalent model,and the sound absorption coefficient of the structural model was solved and obtained.Secondly,according to the randomness of the fiber distribution,with fiber diameter,porosity,fiber diameter distribution,fiber location and fiber number as random variables,the three-dimensional random fiber structure generation algorithm is used to discuss the influence of fiber diameter and porosity on the sound absorption and sound insulation performance of the structure.The results show that the sound absorption performance of porous materials is improved with the increase of porosity.And under the condition of the same porosity,the increase of fiber diameter at high frequencies can improve the sound absorption performance of materials,but the smaller fiber diameter in the low frequency sound absorption performance is better.The sound insulation performance of porous fiber materials is mainly related to the flow resistance of the material.The higher the flow resistance,the better the sound insulation performance of the material.Finally,the finite element method is used to predict the low frequency noise reduction of the porous fiber material attached to the inner wall of the fairing.The fiber diameter and porosity of porous fiber materials are compared and analyzed on the noise reduction effect of the fairing.Two kinds of materials with good noise reduction effect are selected,and the influence of two kinds of sound absorbing materials on the noise reduction effect of different materials of fairing is compared and analyzed.The results show that for different materials of fairing with the same wall thickness,the noise reduction effect of porous material is less affected by the material of fairing structure.The porous material with fiber diameter of 8μm and porosity of 94.5% can achieve the best noise reduction effect at low frequency.