阻抗复合消声器声学性能有限元预测方法及分析

Finite element predictive method and analysis for the acoustic attenuation performance of hybrid mufflers

为计算和分析具有复杂结构的阻抗复合式消声器的宽频消声性能,建立了一种高效声学有限元方法,给出了不同边界条件下的边界积分处理细节,得到有限元全局系数矩阵表达式,设计出计算程序框架以实现这些算法,其求解规模和计算速度与商业软件相比有优势。为计算阻抗复合式消声器的传递损失,通过阻抗管测量和数据拟合得到了吸声材料声学特性的经验公式。计算和测量了两通穿孔阻抗复合式消声器的传递损失,二者良好的吻合验证了声学有限元方法和计算程序的正确性。研究表明,插管长度影响消声器在中高频段的消声特性,右侧隔板上穿孔会消除共振峰,中高频消声性能随着出口管穿孔率的增加而提升。

A high-efficient acoustic finite element approach is established to predict and analyze the acoustic attenuation performance of combined reactive and dissipative(hybrid) mufflers with complicated structures in wide frequency range.The treatment details for the boundary integrals at different boundary conditions are presented,the finite element global coefficient matrix formula is obtained,and then a computational program is built to implement the algorithms,which has advantages in the scale of evaluation model and the speed of computation over commercial software.In order to predict the transmission loss of hybrid mufflers,the empirical expressions for acoustic properties of the long fiber glass wool are presented through the impedance tube measurement and curve fitting.The transmission loss is measured and predicted by using the present finite element program for a two-pass perforated hybrid muffler,and good agreements between them validated the present approach and program.The study demonstrates that the extended length affects the acoustic attenuation performance in middle to higher frequency range,perforations on the right bulkhead may eliminate the resonance,and the acoustic attenuation performance in middle to higher frequency range is improved with increase of the porosity of outlet tube.