Computational fluid dynamics methodology for characterisation of leading edge erosion in whirling arm test rigs

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.

Experimental and CFD simulation of interactions between water droplets with different surface features to understand water droplet erosion

“…6. The outward radial airflow is reported by Herring et al (2019) and Sor et al (2016) in the form of sample wakes. Similar effects are presented in Figs.…”

“…This is mainly due to the effect of the droplet impact angle, which is caused by the twist angle in this blade and the various impact speeds across the length of the rotor. However, recently some researchers (Das et al 2005;Sor et al 2016;Herring et al 2019) realized that this phenomenon may also be influenced by the nature of the complex air flow patterns in the compressor section.…”

Atmospheric Drivers of Wind Turbine Blade Leading Edge Erosion: Review and Recommendations for Future Research

“…Reports suggest "structural repair of a single wind blade can cost up to $30,000, and a new blade costs, on average, about $200,000" [8], both of which inflate the Levelized Cost of Energy (LCoE) from wind. Increasing evidence of blade LEE has spurred development of advanced methods for detection of LEE [8][9][10][11], and to replicate the process of LEE in the laboratory [12,13] or using numerical modeling [14][15][16]. As an example of the latter, the Springer model has been applied for assessing the material properties and combined with Minor's rule to assess time to failure [17].…”