An innovative single-probe method for measuring coupled static deformation of rotor blades: Proof of concept and initial validation

Rotor blades in aero-engines experience coupled static deformation under complex loading conditions. However, the high rotational speed of the blades and the challenging measurement environment within the engine casing have hindered the development of reliable measurement techniques for this deformation. To address this challenge, this study proposes a novel method for measuring the coupled static deformation of rotor blades using a single fiber-bundle probe. The method analyzes the shape characteristics of sensor pulse signals to derive the motion trajectory of the laser spot across the blade tip in the rotor coordinate system. By incorporating stable offsets in Blade Tip Timing (BTT) signals, the static coupled deformation of the blade, including arbitrary deformation components, is further deduced. A two-dimensional mathematical model capable of simulating sensor dynamic signals was developed to numerically validate the proposed method. Additionally, an experimental setup simulating translational and torsional blade deformations was constructed to perform sensor calibration and experimental validation of the measurement approach. Although the measurement accuracy is slightly lower than that of existing multi-probe tip-timing methods, the use of a single probe significantly reduces system complexity, making the method highly valuable for engineering applications.