Performance Simulation Analysis And Optimization Of Muffler Considering Flow Regeneration Noise

The muffler is the main equipment to reduce engine exhaust noise.When the engine works at high speed,the exhaust velocity increases,the complex structure of the muffler is easy to generate flow regeneration noise,thus affecting the noise elimination effect.However,it is very difficult to analyze the flow regeneration noise independently in the traditional muffler exhaust noise testing process.Even if the flow regeneration noise of the muffler is measured,it is also difficult to determine the specific areas accurately for improvement,which results in the presence of blindness in the muffler design on flow regeneration noise control,and makes the actual noise elimination effect of muffler quite different with the expectation.So it's necessary to predict the flow regeneration noise in the muffler design stage.In this paper,a commercial vehicle muffler was taken as the research object,by the means of combining CAE simulation and experiment,a prediction process about flow regeneration noise is attempted to establish,which is suitable for the actual muffler development.First of all,according to the relevant national standard of the muffler,the performance of each working condition was tested.It was found that the insertion loss of some high speed working conditions was less than 16dB(A),so there is room for improvement.And then through the simulation method,the GT-Power is used to simulate the engine and exhaust system,comparing the engine performance curve with the test results,which error is less than 5%.However,it is found that the one-dimensional characteristic of GT-Power cannot accurately predict the tail pipe noise of the engine under high speed condition,so the FLUENT is used for three-dimensional simulation to the inner flow field of the muffler.Using the broadband noise models to get sound power level distribution of the muffler wall,and analyze qualitatively the flow field characteristics and flow regeneration noise of the muffler,using LES model to simulate the sound source data of flow regeneration noise.Finally,the acoustic propagation of the sampled flow regeneration noise is calculated in the Virtual.lab.Compared with the experimental data,it is found that the simulation results under the condition of transient mass flow are more close to the experimental value.Based on the above simulation analysis,the 3 groups of improvement program are put forward to improve the flow regeneration noise of the perforated area,then compared and analyzed the improved muffler with the original model.Considering the overall noise elimination effect,the scheme C has little effect on the low speed of noise reduction,and the average 1.42 d B(A)is reduced in the high speed airflow,which basically meets the requirement of improvement.Combined with the traditional test method,an allied simulating method of giving full play to their respective advantages of the three kinds of software is used to get prediction results which satisfied engineering precision requirement of flow regeneration noise.It provides a new concept to flow regeneration noise prediction,which has certain guiding significance to improve the accuracy of the acoustic design of the muffler.