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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。
The numerical modal matching method (NMM) was extended to calculate and analyze the acoustic performance of the intubated expansion chamber muffler. The corresponding theoretical formula was deduced and the calculation program was compiled. The transverse wave number and eigenvector were extracted by two-dimensional finite element method. The modal matching method was used to calculate the transmission loss of the muffler. The effects of the length of the cannula and the location of the inlet and outlet on the acoustic performance of the muffler with an elliptical non-coaxial expansion chamber with an external pipe were investigated by numerical mode matching method and three-dimensional finite element method (FEM). The calculated results are in good agreement Which proves the correctness of the numerical modal matching method in this paper. The results show that setting a specific length of the cannula and the position of the inlet and outlet can eliminate the pass frequency of the muffler and improve the muffling performance of the muffler in the low frequency.