Analysis Of The Acoustic And Fluid Dynamic Performance Of Muffler Based On CFD Method

Noise has different degrees of harm on human health and the environment.With the increase of car ownership in China,effects of exhaust noise have become increasingly prominent.At the meantime,noise regulations become more and more stringent.Muffler is the most economical and effective way to control the exhaust noise,but the exhaust resistance leads to waste engine power.Therefore,the muffler design process should take the acoustic and fluid mechanics characteristics into account and obtain a better comprehensive performance.A simple muffler was taken as an example to compare the different calculation methods of acoustics and fluid mechanics.According to the calculation accuracy and efficiency,the three-dimensional finite element and three-dimensional time domain pulse method was combined to calculate the acoustic characteristics,the method of computational fluid dynamics was applied to analyze the fluid characteristics.The simulation model of a plurality of different structure parameters were simulated in order to analyze the acoustic and fluid dynamic law of expansion of cavity length,cavity expansion diameter,intubation arrangement,intubation length,cavity expansion number,cavity expansion proportion,cavity expansion section of the connecting pipe layout,the import and export of bias,the resonant silencer.During actual work condition,there is airflow passing through the internal structure.The flow velocity will affect the transmission characteristics of the sound in the pipe.After the simulation process with no flow condition,the acoustic characteristics of mufflers under the changes of different inlet velocity were analyzed of simple muffler multi cavity muffler,single cavity resonant silencer,parallel resonant cavity muffler and external series resonant muffler.The results obtained the transmission loss frequency characteristic and the degree of influence of inlet flow on different mufflers.Through the experimental method the exhaust noise spectrum at rated speed was measured,which has made a significant contribution to extract the exhaust frequency order noise and provide a reference for further optimization of the muffler.The acoustic transmission loss and pressure loss was evaluated after modeling and analyzing the original configuration muffler.Under the premise of keeping the external integral constant of the muffler,the internal structure parameters were adjusted to reduce the noise attenuation performance and reduce the pressure loss of the muffler.