结合大涡模拟和声比拟方法，对膨胀腔消声单元内部的流场及气流再生噪声进行了分析。建立流场数值仿真模型，采用大涡模拟方法对膨胀腔内部非稳态流动进行计算。建立声场仿真模型，通过提取流场信息计算气流再生噪声的声源分布。结合声比拟方法，将气流噪声源导入声场网格中计算远场响应点的气流噪声声压值，仿真结果与实验结果在声压级及共振频率上都吻合良好。根据腔内气流再生噪声产生的机理，选用穿孔管对气流再生噪声进行抑制。搭建气流再生噪声实验台，并加工实验样件，对不同气流速度下的穿孔管膨胀腔的噪声抑制效果进行分析验证。研究结果表明：穿孔管膨胀腔通过阻断强剪切层的形成可以有效抑制腔内低频气流再生噪声，并且随着气流速度的增加，抑制效果向中高频范围扩展；穿孔管膨胀腔对气流再生噪声声压级的抑制效果随着气流速度的增加而增强。
Abstract
Combined with the large eddy simulation and acoustic analogy method, the flow field and airflow regeneration noise inside the expansion chamber of muffler were analyzed.The numerical simulation model for the flow field of expansion chamber was set up.The unsteady flow in the expansion cavity was calculated with the large eddy simulation method.A sound field simulation model was established, and the sound source distribution of the airflow regeneration noise was calculated with the information extracted from the flow field simulation results.Through the acoustic analogy method, the airflow regeneration noise source was introduced into the sound field grid to calculate the sound pressure at the far field response point.The simulation results are in good agreement with the experimental results on the sound pressure level and the resonance frequency.According to the generation mechanism of the airflow regeneration noise in the cavity, perforated tube was used to suppress the airflow noise.The experimental setup of airflow regeneration noise was built, and the experimental samples were processed.The noise suppression effect of perforated tube in the expansion chamber with different airflow velocity was analyzed and verified.The results show that the perforated tube in the expansion chamber can effectively suppress the low frequency airflow regeneration noise in the cavity by blocking the formation of the strong shear layer, and with the increase of flow velocity, the noise suppression effect extends to the middle and high frequency range.The suppression effect of the perforated tube in the expansion chamber on the sound pressure level of the airflow regeneration noise improves with the increase of airflow velocity.
关键词
消声器 /
膨胀腔 /
气流再生噪声 /
大涡模拟 /
声比拟 /
穿孔结构
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Key words
muffler /
expansion chamber /
airflow regeneration noise /
large eddy simulation /
acoustic analogy；perforated structure.
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