均匀流直通穿孔消声器的声学特性分析

Acoustic characteristics analysis of straight-through perforated tube silencers with mean flow

将数值模态匹配法(NMM)扩展应用于计算有均匀流存在时直通穿孔管抗性和阻性消声器的声学特性,编写了相应的计算程序。对于圆形同轴穿孔管抗性和阻性消声器,应用数值模态匹配法计算得到的传递损失结果与实验测量结果吻合良好,从而验证了计算方法和计算程序的正确性。进而应用数值模态匹配法研究了运流效应和穿孔阻抗以及穿孔管偏移对穿孔管抗性和阻性消声器传递损失的影响。研究结果表明,马赫数越高,穿孔管抗性消声器在中高频的消声量越高,阻性消声器在整体频段内的消声性能越差;低马赫数时运流效应对穿孔管抗性消声器的影响可以忽略,马赫数较高时运流效应和穿孔阻抗的影响比较明显;对于穿孔管阻性消声器,穿孔阻抗对消声器声学特性的影响比运流效应的影响小,但是与真实值的差别不可忽略;穿孔管偏移对消声器声学特性的影响与频率和消声器结构均相关。

Numerical mode matching （NMM） method is extended to calculate the acoustic attenuation performance of perforated tube reactive/dissipative silencers with mean flow, and the computational code is written. For the circular coaxial perforated tube reactive and dissipative silencers with mean flow, good agreements between the transmission loss results from NMM method and experiments are observed, which verified the accuracy of the present method and computational code. Then, the effects of flow convection and perforate impedance as well as perforated tube offset on transmission loss of perforated tube reactive/dissipative silencers are investigated by using NMM method. From the predictions it can be seen that, as the Mach number increasing, the acoustic attenuation of perforated tube reactive silencer increases in the mid to high frequency range and the acoustic attenuation of dissipative silencer is lowered in the whole frequency range; in the case of lower Mach number, the effect of flow convection on the acoustic attenuation performance of perforated tube reactive silencer is negligible, and the effects of convection and perforate impedance are noticeable at higher Mach number; for the perforated tube dissipative silencer, the effect of perforated impedance on the acoustic attenuation performance is smaller than that of the convection, and the difference with the real values is not neglected; the effect of perforated tube offset is dependent on frequency range and configuration of silencer.