Natural Frequency Identification of Rotating Blades: A Functional Beamforming-based Method for Spectral Aliasing Suppression in Blade Tip Timing Signals

doi:10.3901/JME.2025.24.028

Abstract

Abstract: A functional beamforming(FB) method is proposed for identifying the natural frequencies of rotating blades from under-sampled blade tip timing(BTT) signals. Compared with the conventional subspace method, the proposed FB method eliminates the need for pre-estimating the number of frequencies, which makes it more valuable for application in practical scenarios. From the perspective of conventional beamforming(CB), the point spread function(PSF) of frequency in the spectrum is derived, and the contribution of the frequency components in the spectrum to the CB output is obtained. Further, combining the properties of the PSF of frequency, the concept of exponent is introduced into the cross-correlation matrix and output of the CB, the aliasing components in the spectrum are suppressed, and the output of the FB is constructed. The effectiveness and superiority of the proposed FB method are verified by numerical simulation and rotating blade disc experiments. The results show that the proposed FB method can effectively suppress spectral aliasing and identify the target frequency. At a signal-to-noise ratio of 5 dB, the proposed method can achieve a 100% identification success rate in the given numerical examples; in the rotating blade disc experiment, the absolute errors for identifying two-order natural frequencies of the blade do not exceed 1 Hz.

Key words: blade tip timing, spectrum aliasing, natural frequency identification, functional beamforming, subspace method

CLC Number:

TH113

ZHANG Chenyu, XIAO Youhong, XIAO Zhicheng, YU Liang. Natural Frequency Identification of Rotating Blades: A Functional Beamforming-based Method for Spectral Aliasing Suppression in Blade Tip Timing Signals[J]. Journal of Mechanical Engineering, 2025, 61(24): 28-37.

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