Study On Size And Topology Optimization Of The Acoustic And Flow Performance Of The Muffler

The main objective of the muffler design is to reduce the pressure drop of airflow and to increase the transmission loss(TL)in the main frequency band of the noise.In this paper,the multidisciplinary size optimization method and topology optimization are used to optimize the performance of the muffler.The actual vehicle noise performance is tested with the muffler and the transmission loss measurement through the impedance tube.Aiming at the problem of multi-cavity perforation resistance muffler optimization,the acoustic and field performance of the muffler are considered.The multidisciplinary optimization analysis and design are carried out by numerical analysis.In the analysis of sound field and flow field,the finite element method based on Helmholz equation and Navier-Stokes equations is used respectively.The boundary conditions and initial values are set in the respective physical fields.The weighting function of two disciplines are established.The multidisciplinary optimization results of Nelder Mead algorithm based on sensitivity and Monte Carlo algorithm based on random sampling are compared.In addition,Genetic Algorithm(GA)as an adaptive global optimization probabilistic search algorithm has been successfully applied to silencer size optimization.By combining the Matlab GA toolbox and Comsol software,the appropriate population size and iteration number are set up.The acoustic-flow field multidisciplinary optimization of the muffler is successfully realized and compared with the optimization results of Nelder Mead and Monte Carlo algorithm.The size optimization method has great requirements with the experience of the designers and cannot change the topology of the existing structure,while the topology optimization method could propose the innovative functional structure.Based on the empirical formula of Delany-Bazley porous material,a three-phase material interpolation model with porous material is established.Combined with Helmholtz partial differential equation filtering technique and Heaviside function smoothing method,the topology optimization method is studied for two-dimension muffler to obtain the optimized transmission loss value.In this paper,based on the Darcy-Stokes equation,the permeability coefficient of artificial porous material is introduced by adjusting the volume force term in the equation,and the interpolation of the porous medium,fluid and solid is carried out.In this paper,LMS equipment is used for the sound pressure data acquisition and spectrum analysis,then the main noise band being determined.The size optimization method is used to optimize the design of the muffler.The optimized muffler was tested for sound pressure level,compared with the original muffler.The acoustic performance was improved.In order to eliminate the other noise interference at the experimental site,the impedance tube transmission loss test was carried out on the muffler.The results show that the theoretical simulation value agrees well with the experimental data.