# Investigation on Characterization of Typical Characteristic in Compressor Based on Flat Plate Model
## 5 Conclusions  
1. The experimental test of the noise between the stages of the compressor is implemented in this investigation. The internal noise spectrum of the compressor presents typical broadband noise characteristics, and there are several characteristic frequencies with discrete pure sound components. The pure sound component appears at 1402 Hz, when the abnormal vibration of high-amplitude value occurs in Rotor1 of the high-pressure compressor. The sound pressure levels of the noise signals measured at four different measuring points along the axial direction of the compressor at the characteristic frequency of 1402 Hz, before and after the abnormal vibration of Rotor1 of the high-pressure of the compressor occurs, are all the maximum value at the position directly above the measuring point over all rotational speed conditions. When the vibration amplitude of the rotor blade sustains a relatively large value, the sound pressure level of the noise signal measured at all measuring points also reaches the maximum at this characteristic frequency. In addition, the sound pressure level directly above the rotor blade is the highest, which is up to 154 dB. 2. The characteristic frequency of 1402 Hz remains constant over a specific speed range, when the high-amplitude vibration of Rotor1 of the high-pressure compressor of the engine occurs, i.e., the phenomenon of \"frequency-locked\". The characteristic frequency sound signal is the same sound wave at the different axial positions of the compressor, and its propagation state in the compressor flow channel is a helix structure. The characteristic above is consistent with the features when the onset of acoustic resonance is excited in the compressor. The work presented in this research can provide data basis for the analysis of the vibration mechanism of the compressor rotor blades, and provide the guidance for the application of acoustic methods in the engineering field for the condition monitoring and structural troubleshooting of a compressor. 3. The typical Parker resonance regime occurs in the rectangular tube model by the calculation method proposed in the paper, which characterizes the distribution characteristics of the shedding vortices at the acoustic resonance condition in detail. The acoustic resonance frequency of the tube coincided with the corresponding result in the literature. The resonance frequency error between the calculation result and the result in reference is 3.6%. Additionally, the \"frequency locking\" feature and \(\beta\) mode of acoustic resonance are captured. The acoustic analogy method is suitable for the characterization of the mechanism of pipeline acoustic resonance over the flow conditions of low Mach number and high Reynolds number. In addition, the typical characteristics of a compressor can be captured effectively at the onset of acoustic resonance. The research method can provide certain method guidance for the research on the mechanism of acoustic resonance of aeroengine compressors. Conceptualization, F.Z. and B.C. ; methodology, F.Z. ; software, B.C., F.W. and M.Y. ; validation, F.Z. and S.J. ; formal analysis, F.W. and M.Y. ; investigation, S.J. and Y.C. ; resources, F.W., S.J. and M.Y. ; data curation, F.Z. ; writing--original draft preparation, F.Z. and B.C. ; writing--review and editing, F.Z. and B.C. All authors have read and agreed to the published version of the manuscript. This research was supported by the China Aviation Development Shenyang Engine Research Institute for the experimental test of compressor noise. And it was supported by Basic Research Project of the Science and Technology Department of Liaoning Province (No. JYT2020009), Scientific Research Foundation for Introduced Scholars of Shenyang Aerospace University (No. 21 YB01), Liaoning Natural Science Foundation Guiding Plan of China (No. 2019-ZD-0237). Not applicable. **Acknowledgments:** This research was supported by China Aviation Development Shenyang Engine Research Institute for the experimental test of compressor noise.