Analysis And Improvement Of Vehicle Exhaust Muffler

Exhaust noise control is a subject of a great value whether for the purpose of environmental protection or market competitiveness improvement.Based on an improvement project of a three-cylinder vehicle’s exhaust muffler,this paper analyzed the performance of mufflers,and proposed improved schemes,the specific work and innovative points are as follows:The structure model and the acoustic cavity model of mufflers were established by software CATIA and the flow field mesh and acoustic mesh were made in software HyperMesh.Flow fields results including velocity,pressure and turbulent kinetic energy were calculated in FLUENT,and the pressure loss curve is drawn.The analysis of acoustic performance was conducted in acoustic FEM module of software Virtual.Lab and the influence of flow,temperature and tailpipe radiation was taken into account.Temperature boundary setting was conducted with temperature field results calculated in FLUENT rather than simply to define the fluid material attributes.The accuracy of GT-POWER,a widely used software,was evaluated.It is found that there is a big difference between the simulation results,especially aerodynamics simulation ones,and the test results.The simulation lacks in accuracy,but exceed in efficiency and the acoustic simulation is able to reflect the characteristics of the muffler to a certain extent.So the simulation of acoustic performance have some reference and application value.Based on the simulation results,the effect of perforation structure and perforation rate on the performance of the muffler was investigated,and improved schemes of front muffler were proposed.In order to achieve a better noise control effect,hybrid muffler scheme was designed,the performance of the muffler under different arrangement of absorbing material was discussed.The resonance cavity is designed in rear muffler for the roaring problem.Finally,the effectiveness of the proposed schemes was verified by test using LMS Test.Lab and its data acquisition terminal.In order to reflect the true noise cancel effect of muffler,tailpipe noise was simulated respectively in GT-POWER and Virtual.Lab.Although,there is a noticeable difference between GT-POWER simulation results and the test results,superiority of better scheme can still be distinguished in the results.Due to the computer performance constraints,simulation in Virtual.Lab was conducted with a bigger increment.The result of order noise differs from testresults both in trend and numerical value,but the total noise keep a better consistency with the test results.