Characteristic Simulation And Improvement Of The ATV Muffler

Most of the exhaust system design methods developed earlier have dealt primarily with one-dimension-plane wave theory. But the theory is hard to provide accurate analysis result because of the effect of the three dimensional wave. The three dimensional numerical method such as the finite element method can simulate the exhaust system's characteristic accurately and take the influence of several outside factors into account. So it is an effective method to an improved design.In this thesis, aiming at a muffler of a 400 ATV, a vibration model and an acoustics model of the muffler are built by FEM. The vibration and acoustics characteristic analysis of the muffler are carried out according this model, and some improvements were achieved as the demand of the factory. The final result of road test proves the improved projects feasibility.Firstly, simple expansive chambers, expansive chambers with inserting cubes and helmholtz resonators are calculated by the 1D and 3D FEM method ,the comparison of the result concludes that 3D FEM is more exact and feasibility. The calculation and comparison also help to know further about the characteristic of each chamber and offers gist to improvement.Secondly, the 3D model of the original muffler is carried out by UG and geometry clean-up and mesh job are finished to get the FE model for vibration analysis. The free and restriction analysis of the muffler model is completed. The comparison between the simulation result and the experimental result concludes that the 3D model is exact and it is possible to generate regeneration noise.Geometry cleanup was based on acoustics characteristic and then the FE model for acoustics was completed. The acoustics characteristic analysis of the muffler and each chamber are achieved according the FEA model. The muffler is shortened to some degree at the basis of understanding the purpose of the designer of the original muffler. The emphasis of improvement is targeted at the fifth chamber under the demand of new legislations.Aiming to the fifth chamber, the helmholtz resonator project and expansive chamber project are suggested separately. The helmholtz resonator project can't fulfill the improved request, while the expansive chamber project can meet the request in middle and high frequency but it is worse than the original muffler in law frequency. The road test is completed at the new legislations, and the result proves the expansive chamber project's availability. But it is worse than the original when noise measured that emitted by stationary ATV.Lastly, for improving the muffler in low frequency, the third and fourth chambers are deleted and the length of second chamber is extended. The simulation result explains that the new project can meet the requests.