Font Size: a A A

Multiple Factors Analysis On Flow Regeneration Noise Of Automobile Muffler

Posted on:2018-08-20Degree:MasterType:Thesis
Country:ChinaCandidate:T LiuFull Text:PDF
GTID:2322330518468813Subject:Vehicle Engineering
Abstract/Summary:PDF Full Text Request
Noise not only affects people's physical and mental health but also affects daily life.With the increasing of amount of automobile,vehicle noise has become one of the main noise source which influences the urban noise environment and residents' health.And that,automobile exhaust noise is the main contribution of automobile noise.With the development of the internal combustion engine to high speed and high performance,the effect of the muffler on the airflow is seriously affecting the engine performance,at the same time,the rapid flow of air flow generates air flow regenerative noise in the muffler,reducing the muffler performance.Especially when the engine is in high speed,the regenerative noise has become the main contribution to exhaust noise.Therefore,it is of great significance to study the relationship between the acoustic performance and the flow performance of the muffler,and to study the influence factors of the air flow regenerative noise.Firstly,based on the Lighthill acoustic analogy theory,using computational aero-acoustics(CAA)hybrid method,using Fluent-ACTRAN joint simulation software,the flow field and the aerodynamic noise field on four kinds of classical cavities which expansion of cavity,cavity,perforated plate,perforated pipe are analyzed.Through the orthogonal design experiments,studied the main structural parameters of the chamber effect on aerodynamic noise,established the mathematical model parameters and the sound pressure level of the tail pipe structure,analyzed the spectral characteristics of the aerodynamic noise of the muffler and the relationship between back pressure difference and the aerodynamic noise.Secondly,the sound and solid coupling model of muffler chamber is established,and the wall radiation of aerodynamic noise is studied,It is concluded that the relationship be-tween the spectral characteristics of wall radiation and the structural mode of the muffler wall.Then the paper analyzes the influence of temperature on the aerodynamic noise,The temperature will affect the airflow state,which will affect the distribution of the regeneration noise source,and affect the noise frequency and sound propagation characteristics.The increase of the temperature can reduce the noise of the airflow regeneration noise.In order to solve the noise problem of a commercial vehicle with multi cavity muffler,a coupling model was established in GT-Power.The simulation and experimental data show that when the engine speed is below 1450r/min,the one-dimensional finite element calculation is in good agreement with the experimental results.When the engine speed is more than 1750r/min,the noise of muffler regeneration cannot be obtained by one-dimensional simulation,and has become the main contribution to the noise of the tail pipe.The flow field,sound field and radiation field of the multi cavity muffler are studied by using the mixed CAA method.The calculation is well consistent with the experimental results.Finally,Using the response surface method with exhaust back pressure difference for indirect optimization target the five factors of internal cavity muffler structure is optimized.Then,the aerodynamic noise is calculated according to the optimized structural parameters,compare with the original machine reduces 5.6 dB(A).The method is feasible.
Keywords/Search Tags:Aerodynamic Noise, Hybrid CAA Method, Lighthill Acoustic Analogy, Sound and Solid Coupling, Response Surface Method
PDF Full Text Request
Related items