Research On Acoustical Performance Of Helmholtz Muffler

Developing of good performance of mufflers is an effective way to reduce the noise of intake and exhaust systems of engine. Helmholtz muffler has simple structure, good acoustical performance and small pressure loss. But it can reduce noise with low frequency and the frequency range is narrow, so it is mainly used in intake systems.In the condition of keeping the installing space unchanged, in order to increase the transmission loss of muffler and improve the frequency of muffler further to reduce the intake system noise well, This thesis used lumped parameter method,1-D plane wave method and 3-D method to research the acoustical performance of Helmholtz muffler detailed and comprehensively.The lumped parameter model, 1-D plane wave model and 3-D model for analyzing were built in this thesis based on theory of acoustic and mufflers. First, the impact the structural parameters on the acoustical performance of Helmholtz muffler is studied in this thesis. It has got the influence rule of volume of resonant cavity, length of connecting pipe, cross-sectional area of connecting pipe and cross-sectional area of main pipe take on resonant frequency.Then, the affect the shape of resonant cavity on the performance is studied in this thesis. It got the conclusion that the shape of resonant cavity had impact on acoustical performance. Based on this result, It has researched the influence law of resonant frequency when the height to parameter ratio, height to width ratio and length to width ratio changed in detail. And the compare between rectangle and circular cross-section resonant cavities is taken. It got the influence rule of the height to diameter ratio or height to width ratio of the cavity take on the resonant frequency. According to the compare of the three kinds of methods, it has got the application range of the 3 kinds of models.At last, the performance of muffler when the resonant cavities are series connected, parallel connected and when the temperature was different has been researched. The results have shown that multiple frequency noise can be reduced with resonant cavities series connected and transmission loss can be increased significantly with resonant cavities parallel connected. The resonant frequency increased with the rising of temperature.