穿孔管消声单元气流再生噪声产生机理

Producing Mechanism of Flow Noise Generation from Perforated Duct Muffler Element

利用双传声器传递函数法和消声器静态传声损失,基于消除传声器头部栅格气流自噪声和气流源中本底噪声的影响,提出了一种测量消声器气流再生噪声的方法。对穿孔管消声单元在不同结构尺寸和气流速度下进行了气流再生噪声测量,分析了主要结构参数对气流再生噪声的影响。结果表明:气流再生噪声总声功率随穿孔直径、穿孔率、穿孔部分长度的增大而增大。声模态数值计算和试验对比发现声模态频率和气流再生噪声峰值频率一致,进一步的流场数值计算表明,流体剪切层的不稳定产生了气流噪声,激起了穿孔管消声单元空腔的声模态,导致气流再生噪声增大,揭示了穿孔管消声单元气流再生噪声的产生机理,为优化消声器内部流场、抑制气流再生噪声和提高动态消声性能分析提供了重要依据。

Based on erasing effect from flow noise in the head lattice of microphones and background noise in the flow source, a method to measure the flow noise regeneration from mufflers is proposed by using two- microphone transfer function method and static transmission loss of mufflers. Flow noise regeneration from perforated. pipe muffler of different dimensions is performed under flow condition, and the effects of main structure parameters on flow noise generation are analyzed. The study shows that total power of flow noise generation increases with the increase of perforated diameter, perforated rate and length of perforated part. Some acoustic mode frequencies from numerical simulation agree well with the peak frequencies of experi- mental flow noise generation. Flow field analysis indicates that flow noise generation is producing due to shear layer instability, and it excites muffler acoustics mode, leading to enlargement of flow noise regener- ation. Producing mechanism of flow generated noise on perforated muffler element is clarified. The study provides the guidance on optimization of flow field inside the muffler, retraining flow generated noise and improvement of dynamic attenuating ability.