Non-Contact High-Frequency Vibration Measurement Using Blade Tip Vibration Acceleration

High-cycle fatigue in turbine blades often results from high-frequency vibrations induced by cyclic pulsations in heavy-load conditions. Monitoring these vibrations, especially those occurring at higher multiples of the rotational frequency, is crucial for diagnosing and predicting high-cycle fatigue. However, the conventional blade tip vibration displacement measurement technique faces challenges in accurately measuring such high-frequency vibrations and often introduces calculation errors when estimating the expected time of arrival (TOA). To address these challenges, a two-sensor blade tip velocity measurement technique, named BTV-V, has been proposed. Although this method eliminates the need for estimating the expected arrival time, it still necessitates estimating rotational speed, which could lead to measurement uncertainties. In order to accurately capture the rapid changes in high-frequency blade vibrations and provide more comprehensive vibration characteristic details, the BTV-V method has been further extended to include a third sensor, enabling the measurement of blade tip acceleration, defined as BTV-A. Simulation studies confirm the advantages of the BTV-A method, highlighting its independence from Once-Per-Revolution (OPR) sensors and speed calculations, and its ability to precisely capture high-frequency blade vibrations, thereby offering richer and more accurate vibration characteristic information compared to traditional displacement or velocity measurement methods.