Rain erosion of wind turbine blades and the effect of air bubbles in the coatings

Abstract

Leading edge erosion on a wind turbine blade from Vindeby offshore wind farm is characterized by X-ray tomography, and air bubbles within the top coat are observed. Similar coating systems with and almost without air bubbles within the top coat are tested on a R&D Test Systems style whirling arm rain erosion tester (RET) and found to have different V–N curves. In general, the slope of the two curves was comparable. However, the absolute performance value with RET differs significantly with up to 2.6 times performance advantage to the coating with less bubbles. A micromechanical model of the coating system that takes the air bubbles into account has been developed, and air bubbles are found to have critical effect on the crack initialization in the coating.