Acoustic Performance Analysis Of Automobile Exhaust Muffler Based On Semi-analytical Meshless Metho

The acoustic analysis of engine exhaust muffler has important and extensive significance in the process of automobile research and design,and plays an important role in improving driving comfort and controlling external noise.With the development of the times and scientific progress,various numerical algorithms emerge as the times require.The meshless numerical calculation method is used to analyze the sound field of muffler for the first time.Compared with the traditional finite element method and boundary element method,it does not need grid division,but only needs discrete nodes.This method establishes the interpolation basis function through node information.The mathematical theory is relatively simple,the calculation accuracy is high and the program is easy to implement.Through the analysis of typical examples,the sound field of two-dimensional and three-dimensional automobile exhaust muffler model is simulated,the acoustic prediction of muffler is realized,and the noise reduction performance is further studied.Firstly,the acoustic problem of automobile exhaust muffler is studied.Based on the Helmholtz equation,the mathematical model of muffler sound field is established based on the singular fundamental solution and non-singular general solution of the governing equation,combined with the grid-free point allocation technique.Using a classical boundary-type global meshless method and a novel domain-type local meshless method,namely the Method of Fundamental Solutions and the Local Knot Method,according to the given physical model and boundary conditions,the calculation is derived,and the design of the MATLAB algorithm program.Secondly,two-dimensional and three-dimensional acoustic models of resistant mufflers are established by using the Method of Fundamental Solutions.Taking the singular fundamental solution of acoustic wave equation as the basis function,the corresponding boundary conditions are given according to the operating condition of the resistant muffler.Combined with the proposed algorithm,a program is designed to solve the problem and the results are tested.Compared with the finite element method,it is proved that the proposed method is accurate in analyzing the acoustics of two-dimensional and three-dimensional resistant mufflers.This method is used to discuss the change rule of transmission loss of muffler and analyze the acoustic performance.The results show that the method has high accuracy,reliability and stability.Finally,the acoustic calculation models of the two-dimensional expansion cavity and the three-dimensional impedance muffler with an external inlet and outlet tube are established.The Local Knot Method is used to discrete the nodes of the model.According to the node information,the non-singular general solution is used as the interpolation basis function.Combined with the boundary conditions,the matrix equation is obtained and the sound pressure is obtained.The influence of different sound absorbing materials on the transfer loss is discussed.Numerical experiments show that the local meshless algorithm is accurate in simulating the acoustic performance of mufflers and can be used as an important technical algorithm to analyze acoustic problems.