插管结构对膨胀腔消声器声学性能的影响

将数值模态匹配法(NMM)拓展应用于计算和分析外插管膨胀腔消声器的声学性能,推导了相应的理论公式并编写了计算程序。使用二维有限元法提取横向波数和本征向量,应用模态匹配法计算消声器的传递损失。使用数值模态匹配法和三维有限元法(FEM)研究了插管长度和进出口位置对带有外插进出口管椭圆形非同轴膨胀腔消声器声学性能的影响,两种方法计算结果吻合良好,从而验证了本文数值模态匹配法的正确性。研究结果表明,设置特定的插管长度和进出口位置可以消除消声器的通过频率,进而改善消声器中低频的消声性能。

Effects of extended ducts on acoustic attenuation performance of expansion chamber mufflers

A numerical mode-matching(NMM) method is extended to predict the acoustic attenuation performance of expansion chamber silencer with extended inlet and outlet.The corresponding theoretic formulation is derived and the computational code is written.The two-dimensional finite element method is used to extract the transversal wavenumbers and eigenvectors,and the mode-matching technique is employed to determine the transmission loss of expansion chamber silencer.Effects of different extensions and locations of inlet/outlet on the acoustic attenuation performance of the elliptical non-concentric expansion chambers with extended inlet and outlet ducts are investigated by using the present NMM approach and the FEM,and good agreements between them verified the accuracy of the present numerical mode-matching approach.The results show that the pass frequencies of the elliptical expansion chambers can be eliminated by choosing the extensions and locations of inlet and outlet,therefore the acoustic attenuation performance in the low-middle frequency range is improved.