Research on Broadband Noise Mode Identification Technology of Annular Cascades

The issue of broadband noise in turbomachinery duct has assumed increasing importance in the research of civil aviation noise reduction. In the acoustic measurement of turbomachinery duct, the characteristics of the acoustic power spectrum and the measurement of the magnitude are of great concern. For the mode decomposition of broadband noise in turbomachinery duct, this manuscript presents rotating rods-annular cascade model for emulating fan rotor-stator interaction noise. The model is intended to be used as a test platform for studying noise reduction techniques for turbofan fan noise. Concurrently, the experimental study of the broadband noise of a fan annular cascade duct is conducted utilising a new technique for measuring the mode amplitude distribution and sound power transmission. The innovative aspect of this method is that it uses the microphone array beamforming theory for reference, and exploiting the fact that the mode decomposition for azimuthal mode detection is exactly the same as Conventional Beamforming with microphone arrays. This method can reduce the processing time required for measuring broadband noise in the duct. In comparison with current mature measurement methods. The experimental findings demonstrate the efficacy of the proposed method in accurately measuring the radiated noise in the duct of a fan annular cascade. With regard to duct mode, the method is in good agreement with the mature measurement method, and the recognition results of highfrequency modes seem to be more accurate.