Performance Simulation Analysis And Improvement Of Exhaust Muffler Of LJ276M EFI Gasoline Engine

The exhaust noise of automotive engine is one of main noise sources of automobile noise.The most effective measure to control exhaust noise is to using muffler in exhaust system.Designing a muffler with high anechoic performance and low press less has become an important subject on exhaust noise control.In this thesis,aiming at a muffler of LJ276M engine,engine test bench of muffler is built according to the national standard "GB/T4759-1995 measurement procedure for exhaust mufflers of engine" and tail pipe noise,insertion loss and press loss of the original muffler have been measured.Then,simulation models of LJ276M engine's original muffler,insertion loss and press loss are built using muffler simulation software of GT-Power.Through comparison analysis between simulation results and experimental results,the performance simulation models of muffler are verified to be accurate.So the paper is ready to next step of improvement design.The improved goal of reducing high frequency noise is established through the the anechoic performance analysis of the original muffler and the improved design is carried out:based on the original muffler,the housing numbers are changed, clapboards are transformed into perforate board and the insertion tubes are perforated so that the anechoic performance can be enhanced for all the noise frequency, especially the high noise frequency.The improved results show that the insertion loss increases 5～10dB(A) aiming at the high speed and the press loss changes little.Lastly,the 3D model of the improved muffler is carried out and geometry clean-up and mesh job are finished to get the FEM model for modal analysis.The improved muffler modal parameters can be obtained through the restriction analysis of the muffler model.The modal results show that exhaust's excited frequency of engine is far from natural frequency of the improved muffler and the resonating can be avoided.The numerical simulation of exhaust muffler in this thesis can provide reference and new method for muffler design and improvement.It is of important instructional significance for improving the design and analysis of muffler.