OPR-free blade tip timing using a single sensor for abnormal blade detection

Rotor blades are critical components in aeroengines, and monitoring their condition through blade vibration is essential to ensure engine safety. Blade tip timing (BTT) is a non-contact blade vibration measurement method for blade condition monitoring; however, traditional BTT relies on the use of an once-per-revolution (OPR) sensor and multiple BTT sensors, which limits its practical application. Existing OPR-free methods often involve complex computations, and the traditional abnormal blade detection technique based on blade displacement requires quantitative comparison. To address these limitations, this paper proposes an OPR-free BTT approach for abnormal blade detection using a single BTT sensor. The first part of the proposed approach is the blade spacing change with speed smoothing (BSC-SS) method, which measures the spacing change between adjacent blades. The speed smoothing method provides a simple way to eliminate speed calculation errors present in traditional BTT. The second part is the BSC-based abnormal blade detection (BABD) strategy, which detects the abnormal blade through qualitative analysis of the time–frequency spectrum. Simulated and experimental results demonstrate that the BSC obtained by BSC-SS exhibits less disturbance compared to blade displacement and displacement differences. Furthermore, the BABD strategy proves effective as an intuitive approach for abnormal blade detection.