Abstract
Blade leading edge erosion has developed into a significant issue for the offshore wind industry. Protection solutions, including polymer coatings and tapes, are often applied to increase the blade lifetime. Experimental evaluation of protection systems is typically conducted in whirling arm rain erosion test rigs. Currently, there is no thoroughly validated method to relate the test results to real-world erosion performance. Furthermore, the design of rigs is not sufficiently limited to enable comparison of results between different rigs. Industry guideline, DNV-GL-RP-0171, provides a comparison method to address this issue. This paper describes the development of a droplet particle tracking Computational Fluid Dynamics methodology for rain erosion test rigs, which models the impact strike characteristics of a droplet, the number of impacts and the effect of rig aerodynamics. The methodology was applied to two rigs with different aerodynamics. Rain erosion tests were conducted in the rigs on identical coating and aluminium samples. The results were compared against predicted number of impacts from the DNV-GL guideline. Contradictory results were found, concluding that the guideline does not provide an accurate comparison between all test rigs, as it does not account for rigs where large aerodynamic effects cause droplet concentrations or droplet break-up.
Highlights
Blade leading edge erosion has developed into a significant issue for the offshore wind industry
This paper describes the development of a droplet particle tracking Computational Fluid Dynamics methodology for rain erosion test rigs, which models the impact strike characteristics of a droplet, the number of impacts and the effect of rig aerodynamics
The first model was validated against high speed video footage of the corresponding test rig, whilst the second model was validated through a comparison with the predicted kinetic energy of droplet impact against the analytical solution presented in the DNV-GL guideline
Summary
Blade leading edge erosion has developed into a significant issue for the offshore wind industry. DNV-GL-RP-0171 [3], does give a comparison method it does not account for rigs where large aerodynamic effects and droplet concentrations occur. This has been observed to lead to conflicting rain erosion test results due to the elastic and viscoelastic nature of polymer coatings. For the development of a realistic lifetime prediction model from rain erosion test results, which accounts for all protection systems and rain erosion rigs, a direct relationship needs to be established between test rig parameters and the characteristics of the erosion developed in different materials. The test rig at Offshore Renewable Energy (ORE) Catapult This rig is the wind industry standard design used within the DNV-GL guideline for geometrical droplet impact calculations
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