Study On Automotive Exhaust Muffler Performance Based On Coupling Gas Solid Acoustics With Thermal

When thin shell exhaust muffler actually works, there will be high temperature and high speed airflow. Analyzing the influence of the elastic wall, airflow and temperature to the acoustic performance, pressure loss and the modal parameters of the muffler accurately is of great significance. Based on the numerical simulation and related experiments, some research done in this paper by coupling the gas-solid-acoustics-thermal is as follows.(1) Aero-dynamic&acoustic test rig which can measure the acoustics performance and pressure loss of the muffler has been set up. By comparing the measuring result and the simulation result with the theoretical value in the one-dimensional plane wave of the simple expansion chamber muffler transmission loss, the indirect calibration of transmission loss measurement is realized on the test rig on condition that there is no precise theoretical value. By comparing measuring result and simulation result of pressure loss, only little difference between them is found. The confidence of the muffler’s GT-POWER simulation model is verified by the test rig and by conducting the acoustic experiments and measuring the pressure loss of two other structure-complicated mufflers, the test results are evaluated comprehensively to choose the relatively better muffler.(2) From the sides of gas-solid coupling and thermal-solid coupling, the airflow and temperature on the influence of the simple expansion chamber muffler structure modal parameters is analyzed on the Workbench software and the conclusion is made that airflow has less effect on the modal parameters, while the temperature factor can not be ignored.(3) Based on the Virtual. Lab software, the influence of elastic wall to transmission loss of muffler has been studied using acoustics-solid coupling finite element method.Whether only the inlet side is constrained or both the inlet and outlet sides are constrained in the acoustics-solid coupling analysis, the transmission loss always decreases and jumps in some structure modal frequency. And the conclusion is made that changing the shell thickness, the thinner the shell, the more obvious the jump phenomenon.(4) The boundary condition of temperature field based on the CFD analysis is used in the one-way thermal acoustic coupling analysis and it is found that the transmission loss of muffler increases in high frequency when it is full of non-uniform distribution high temperature gas, and on this bases of acoutics-solid coupling and thermal-acoustic coupling, the transmission loss curve is analyzed under the thermo-fluid-structure coupling condition.(5) The acoustic modal frequency and sound pressure distribution are analyzed under normal temperature and high temperature condition. Compared with the normal temperature, the acoustic modal frequency increased and the sound pressure distribution basically remained unchanged on high temperature condition.(6) Considering the influence of airflow velocity to transmission loss of the muffler, the simulation result shows that compared with no flow case, the velocity direction of airflow determines whether the transmission loss increases or decreases, the greater the absolute value of the airflow velocity, the greater the change of transmission loss.The research work of this paper has certain innovations as follows.The transmission loss will be more accurate under the combined action of the elastic wall and non-uniform distribution high temperature, coupling thermal acoustics with solid in the study of muffler is rarely seen.