共振式消声器气流再生噪声发生机理研究

Investigation on Gas Flow Noise Generation Mechanism of Resonant Muffler

在消声器模拟试验台上，对共振式消声器声学性能进行试验。结果发现：气流速度较低时，消声量基本保持不变；气流速度较大时，消声器的消声量为0，甚至为负值，由气流产生的再生噪声所致，说明气流是影响共振式消声器消声性能的重要因素。对高速气流产生的再生噪声频谱分析结果表明：马赫数在0．167～0．193之间时，空腔Rossiter 2阶和4阶振荡模态被激起，频率符合Rossiter空腔半经验公式。声模态和流场分析结果表明：剪切层的不稳定产生了气流噪声，激起了共振腔消声器腔体的声模态，导致气流与噪声耦合，揭示了共振腔消声器气流再生噪声的产生机理，为进一步进行消声器内部流场优化、抑制气流再生噪声和动态性能分析提供了重要依据。

The experiments of acoustic performance of a resonant muffler were performed on the muffler simulating test bench. The results confirm that the sound attenuation level of the resonant muffler at lower gas velocity is the same as that when no gas flow, the sound attenuation level of the muffler is zero or even negative value at higher gas velocity. This shows that the gas flow velocity is an important factor affecting sound attenuation performance of the resonant muffler. The analysis for frequency spectrum of the flow generated noise shows that Rossiter 2 and 4 vibration mode are provoked when Mach number is 0. 167 0. 193, which agrees with Rossiter＇s semi-empirical correlation. And results of acoustic mode and flow field analysis show that the gas flow noise is caused by shear layer instability and it excites the some acoustic modes in the resonant muffler, which leads to the coupling of gas flow and noise. This study reveals the mechanism of gas flow generated noise in resonant cavity mufflers and provides a significant foundation for optimizing flow field inside the muffler, controlling gas flow generated noise and analyzing dynamic characteristic of the mufflers.