Wind energy is an increasingly important contributor of power within the renewable energy sector. In recent years, there has been a rise in the number of reports of defective blades contributing towards turbine failure. At present, regular, costly inspections are conducted on turbine blades to ensure structural integrity and prevent degradation due to fatigue or impact.
The objective of the WinTur project is to design a structural health monitoring system that integrates Acoustic Emission (AE) and Long Range Ultrasonics Guided waves (LRU) - into one sensor algorithm system. Signal processing techniques are utilised to provide an indicator for system integrity.
The integration of LRU and AE sensors was explored by TWI on a full 9.8m turbine blade. The AE system passively detects the onset of composite deterioration whilst LRU guided waves actively interrogate the structure. The LRU sensors (Macro Fibre Composite) are low-profile, conformable and unobtrusive. Experimental analysis revealed the in-plane (S0) Guided wave mode to be most sensitive to boundary and material changes. This finding (and attenuation measurements) informed the design of the GW array. AE measurements were performed using broadband sensors (250-500kHz).
The resultant integrated AE/GW spatial sensor array was applied to the blade to analyse the effects of blade geometry. The AE sensors identified the fastest wave-mode (S0) thereby providing validation of the GW system without compromising system integrity. A pulser/receiver (TeletestT) was used to excite the blade with propagating ultrasonic waves on one sensor and receive data on all other sensors within the array.
Signal processing techniques were developed to provide a multi-parametric analysis on structural integrity. Cross-correlation analysis was performed using baseline data to identify the onset of defects.
To summarise, the WinTur SHM system provides:
- A visual blade display indicating latest blade status over an area of 3.8m for growing defects; 800mm for impact damage, and sensitivity of fibre-breakage down to 2mm. Location of the defect is also provided.
- A Graphical User Interface providing signal visualisation, a visual status indicator, easy-to-use navigation tools, tabulated display of critical information and a reporting facility.
For more information, please contact us.