Leading Edge Erosion of Wind Turbine Blades

: An Assessment and Improvement of the Translation Between Test Results and In-situ Performance

Abstract

Greater blade lengths and higher tip speeds, coupled with a harsh operating environment, have caused blade leading edge erosion to develop into a significant problem for the offshore wind industry. Raindrop and hailstone impacts erode material from the blade surface, reducing turbine efficiency and requiring expensive in-situ repairs. Leading Edge Protection (LEP) systems, including coatings and tapes, are employed to protect the blade edges, but do not last the turbine lifetime and must be regularly replaced. LEP performance is typically evaluated in an accelerated whirling arm rain erosion test, but there has been no published methodology that accurately translates test results to in-situ performance. A recent joint industry project attempted to resolve this and published a Recommended Practice (RP). However, the RP lacks validation and is only regarded as a first step towards a standard that will reliably examine LEP systems.

This Thesis completes the first assessment of the RP and combines industrial projects, commercial LEP systems, rain erosion test facilities, offshore measurements, and in-situ erosion data to evaluate each aspect of its approach. It is shown how the RP’s use of an outdated damage model and challenges in the appropriate characterisation of modern LEP systems risk inaccurate translations. Moreover, an investigation into rain erosion testing revealed that the RP’s lack of guidance on test rig parameters allows the unrepresentative assessment of an LEP system’s erosion performance. Thus, a developed data derived approach is presented alongside test parameter guidance to remove the requirement for material properties and provide a representative quantitative approach. Furthermore, identified gaps in the understanding of the offshore environment and particle impingement characteristics were respectively tackled through the first characterisation of offshore precipitation and the development of a novel sensor based methodology. Finally, the first validation of the RP against in-situ data found that the original RP predictions greatly overestimate the in-situ lifetime of an LEP system. However, when the recommendations made in the Thesis are applied, a significantly improved translation between test rig results and in-situ performance is achieved.

Overall, the Thesis shows that the RP has too many limitations to provide accurate predictions and the improvements contributed within this Thesis should be adopted to support an improved methodology. Further in-situ data is required to conclusively confirm and quantify the extent of the benefits offered by the improvements contributed, and this is being delivered in an ongoing industrial project supported by this research. Ultimately, the Thesis plays a crucial role in ensuring that LEP systems are correctly evaluated, therefore facilitating the identification and development of the improved LEP systems required to combat the serious problem of leading edge erosion in the offshore wind industry.

Date of Award	12 May 2022
Original language	English
Awarding Institution	University of Bristol
Supervisor	Carwyn Ward (Supervisor) & Kirsten P Dyer (Supervisor)