Effective prevention of rain erosion on rotor blades

When operating, the wing tip of a wind turbine can reach speeds of 300 to 350 km/h and, as a result, rain drops act like sandpaper on the surface of the material. Researchers are developing reliable forecasting models for erosion damage to improve the effectiveness of protective mechanisms.

Comparison of samples with different coatings after the rain erosion test. Source: Jan Meier -

As part of the research project “Development of a method for determining the service life of rotor blade coatings” (BeLeB), tests are performed on the Fraunhofer IWES test bench.

Drop impact system improves damage prognosis

Both the amount and size of the drops as well as the timing and frequency of their impact can be regulated precisely on the rain erosion test bench. Moreover, over the course of the 3-year project, a drop impact system will measure exactly where the drops hit and the damage they cause. The entire test bench is modeled for this with the aid of a CFD simulation. A laser-based inspection system and a high-speed camera are used to document the damage, whereby both the topology of the sample and damage in the micrometer range are recorded. The development of an adequate material and damage model will improve understanding of the processes at material level.

Automatic inspections shorten testing periods

Continuous testing is possible thanks to the use of a laser-based automatic inspection system. The throughput of material samples increases and reliable results can therefore be achieved in shorter testing times. “Current automatic inspection systems in rain erosion test benches do not allow for detailed damage assessment and therefore reach their limits when it comes to deducing reliable damage models”, explained Benjamin Buchholz, Project Manager at Fraunhofer IWES.

Assessment of coating applications

The project partners aim to achieve a further procedural improvement with an ultra-sound-based method to establish the quality of coating application. After all, the product can only develop its full protective effect when it is ensured that application can be performed precisely. The repair process in the field is also supported in order to identify optimization approaches. To this end, damaged material samples are repaired in the climate chamber under environmental conditions and the various procedures are com-pared.

Reducing repairs and maintenance

The goal of the project partners is to improve the effectiveness of known protective mechanisms for rotor blades tangibly. They hope this will reduce the time and money invested in repairs and maintenance. This would represent a major step forward in ensuring the improved profitability and thus enhanced competitiveness of wind energy. The provision of effective rain erosion protection is not only of great interest to operators and maintenance companies, but also to suppliers of protective systems and manufacturers of matrix resins and gel coats.
Partners: Blade Care, DWT, Fraunhofer IWES (coordinator) Fraunhofer IZFP, FreiLacke, Jadewind, Nordex, Ocean Breeze, Senvion

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