TS-38 Comparative Study of the Methods for Detecting and Analyzing Rotating Stall Inception in Compressors(Session B-4: Unsteady Flow 1)
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概要
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This paper presents a comparative study of the methods for detecting and analyzing rotating stall inception in compressors. Experimental measurements were performed in a low-speed and a high-speed axial compressor at different operating speeds. The dynamic signals were acquired by using high-frequency pressure transducers mounted on the casing shroud along the direction of the blade chord. Several methods were implemented, such as conventional Low-Pass Filter, High-Pass Filter, Band-Pass Filter, Band-Stop Filter and Short-Time Fourier Transform, and two new methods: Wavelet Transform and Wavelet Filter which are recently developed tools for unsteady signal analysis. Low-Pass Filter and Band-Pass Filter are insensitive to the nonlinear components of the signal, which are often filtered out, but Wavelet Filter is able to capture this detail very well. According to Short-Time Fourier Transform, the time and frequency resolutions of the elementary functions are fixed once the window type is selected. But those of Wavelet Transform change over time to self-adapt different frequency components of the signal, and thus the whole range of the time-frequency characteristics of the signal could be observed. Through Wavelet Transform and Wavelet Filter, the inception process prior to rotating stall was observed to begin from an impulse of pressure signal, which is either filtered out by conventional filters, such as Low-Pass Filter, High-Pass Filter etc., or not obvious when using Short-Time Fourier Transform. Following the impulse, a low-frequency wave whose frequency steps up gradually was found through Wavelet Transform, while the results of Short-Time Fourier Transform only shows some stronger components of the signal during some periods and can not reflect the whole evolution process of the stall inception. It is clearly observed by the Wavelet Transform that in high-speed compressor, a time-delay exists along the chord of the blade for the emergence of the impulse and the following frequency step-up of the wave. The falling into full stall doesn't happen until the step-upped frequency of the wave near the leading edge reaches the first harmonic of the full stall. The process as such again could not be observed by Short-Time Fourier Transform. Based on the methods of Wavelet Transform and Wavelet Filter, the software was then developed specifically for detecting and analyzing rotating stall inception in compressors.
- 公益社団法人日本ガスタービン学会の論文
- 1999-11-14
著者
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Chen Jingyi
Institute Of Engineering Thermophysics Chinese Academy Of Sciences
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Nie Chaoqun
Institute Of Engineering Thermophysics Chinese Academy Of Sciences
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CHENG Xiaobin
Institute of Engineering Thermophysics Chinese Academy of Sciences