Presentations

Abstract

Wind turbine blades are prone to structural failures and environmental damage, such as internal delamination and leading edge erosion, and are reported to be one of the main sources of failures in wind turbine systems [1]. Remote inspection methods have gained increasing attention, as they avoid turbine shutdown and the installation of additional sensors on the blades [2]. In this work, an experimental study on the remote blade inspection using aeroacoustic and thermal measurements is performed in the Open Jet Facility (OJF) at Delft University of Technology, aiming to investigate the combination of these two non-contact methods for detecting various types of blade damage on a rotating wind turbine. The tested wind turbine rotor was scaled down to 2.5 m from a 2.3 MW NM80 reference wind turbine [3]. Three different types of damage were created during the manufacturing process: internal structural delamination, trailing edge cracks and leading edge erosion. A Bionic M-112 microphone array was used for acoustic measurement, and by applying a beamforming technique, background noise can be effectively suppressed. A Cedip Titanium infrared camera equipped with a 25 mm focal-length lens was used for thermal measurement; three 500 W halogen lamps were used to heat the blades and the surrounding air to mimic the natural solar heating. The experimental results show that, as the crack potentially increases the trailing edge thickness, , a tonal component is observed in the spectra and peaks at the trailing-edge-thickness-based Strouhal number,, between 0.15 and 0.25, which agrees with the results reported in the previous studies [4]. In contrast, infrared thermography demonstrates the capability to visualize internal delamination, where the damaged region exhibits a higher temperature than the normal section. In addition, leading edge erosion promotes an early boundary layer transition to turbulence, which alters the blade surface temperature distribution and can be used as an indicator of erosion damage. The results show that aeroacoustic measurements are sensitive to edge damage, whereas thermography is effective in detecting internal defects. This suggests that the combination of these two techniques can provide a complementary and robust approach for the comprehensive detection of both edge and internal damage in wind turbine blades. References 1. Ribrant, J. and Bertling, L.: Survey of failures in wind power systems with focus on Swedish wind power plants during 1997-2005, 2007 IEEE Power Eng. Soc. Gen. Meet. PES, 2–9, 2007. 2. Sun, S., Wang, T., and Chu, F.: In-situ condition monitoring of wind turbine blades: A critical and systematic review of techniques, challenges, and futures, Renew. Sustain. Energy Rev., 160, 112326, 2022. 3. van der Velden, W. C. P. and Casalino, D.: Towards digital noise certification of serrated wind turbines, 25th AIAA/CEAS Aeroacoustics Conf., 2019. 4. Zhang, Y., Avallone, F., and Watson, S.: Wind turbine blade trailing edge crack detection based on airfoil aerodynamic noise: An experimental study, Appl. Acoust., 191, 108668, 2022.