Fluid Dynamic And Acoustic Performance Analysis Of Automotive Expansion Chamber Muffler

Energy and environment are two main research subjects with which people arefaced in this century;therefore, people pay more and more attention on automotivenoise and economy. The research object of this paper is the muffler, which is a keyfunction in automotive noise control. In order to obtain goals in the two aspects ofenergy and environment, this paper studies the most common used expansionchamber muffler in the two fields of fluid dynamic and acoustics. So that a design thatresults in high noise attenuation value and low backpressure structure can be obtained.Using fluid dynamics FEM (two dimensional, three dimensional andaxisymmetric) and three dimensional acoustic FEM in meticulous analysis ofexpansion muffler structure, this paper studies the influences of each mufflercomponents' position, dimension, form and quantity on the fluid dynamic andacoustic performances;therefore the paper indicates that the end of the intruding tubeis the linchpin of the fluid dynamic performance of the whole muffler structure, thespringhead of muffler fluid dynamic performance is the smoothness of air current, themain factor which affects the acoustic attenuation value of expansion chamber muffleris the grade of saltation of the section of air conducting access, and the attenuationvalue of specific frequency can be dramatically enhanced by carefully designing thelength of expansion chamber. Based on the integration of the results of acoustic andfluid dynamic analysis, this paper points out that synthetical acoustic and fluiddynamic performance of muffler can be obtained by using square expansion chamber,by stringing together several podgy expansion chambers, by applying noise absorbingmaterial on chamber walls, by making chambers and pipers co-axial, by adding filletson the end of intruding pipes, and by making the diameter of outlet pipe a little greaterthan the diameter of the inlet pipe.Finally, based on the results of expansion chamber muffler noise attenuationtesting, the validity of the finite element analyzing in this paper is verified, and thefurther studies in the future is envisaged.