A Single-Probe Blade Tip Timing Method for Fast Extraction of Blade Natural Frequency

With the advantages of noncontact and the characteristic of the whole circumferential blade measurement, blade tip timing (BTT) technology shows vast potential for blade vibration monitoring. However, the frequency aliasing and nonuniformity in BTT signals remain the core challenges for accurate blade vibration reconstruction from BTT signals. In this study, a single-probe-based method that can extract the natural frequency of the rotating blade rapidly and accurately without considering the layout and number of the probes was proposed. First, a virtual signal is generated based on the BTT signal. Then, the two signals are multiplied and FFT is performed. By searching for peaks to find specific frequencies in the spectrum, de-aliasing can be achieved based on the frequency components in the product signal, and ultimately the natural frequency of the blade is obtained. The numerical and experimental results have verified the effectiveness of the method. The potential of the proposed method for small sample signal analysis and online blade health monitoring has also been demonstrated.