Abstract: The cut-on sound mode in fan duct increases seriously with the increase of the aero-engine hub ratio. In order to improve the accuracy of mode identification and decomposition technology of broadband noise in fan duct， it is necessary to study the coherence of sound mode in duct. A single-stage low-speed axial flow fan experimental bench is used as the experimental object. The mode coherence and sound field coherence of a single-stage low-speed axial fan are studied. The effects of mode coherence on the sound power level at the duct inlet are compared with the reference microphone mode decomposition method and the cross-correlation mode decomposition method. The results show that the mode coherence has little influence on the incident sound wave but strong influence on the reflected sound wave. Therefore， it is necessary to consider mode coherence and adopt a more reasonable mode decomposition technique in the high-precision mode decomposition experiment.

Key words: Fan;Coherence;Mode decomposition;Duct acoustics;Microphone array

摘要： 航空发动机轮毂比的增加使得处于“截通”状态的管道声模态数目急剧增加，为了提高风扇管道宽频噪声模态识别及分解技术的准确性，需要对管道声模态相关性进行分析研究。以一台单级低速轴流风扇实验台为实验对象，研究了单级风扇的模态相关性以及声场相关性。进一步结合参考传声器模态分解法和互相关模态分解法，对比了模态相关性对管道进口声功率级产生的影响。结果表明，管道模态相关性对入射声波影响较小，对反射声波影响较大。因此，在高精度模态分解实验中，有必要考虑到模态相关性，并采用更加合理的模态分解技术。

关键词: 风扇;相关性;模态分解;管道声学;传声器阵列