Water droplet erosion of aeroengine fan blades: the importance of form

The radius of typical water droplet, which an aeroengine encounters in-service, and the radius of curvature of a typical fan blade leading-edge are approximately the same; this is unlike previously investigated contexts, where the typical droplet radius is at least an order of magnitude smaller. The consequences of this have been explored theoretically but never experimentally. In this study, an established technique was used to generate high-speed impingements (210 m s−1 to 250 m s−1) of water on planar and curved (in one plane) samples of a comparatively well-understood material (polymethylmethacrylate). A novel, direct, characterisation methodology (using ultra-high-speed imaging) was employed to accurately describe each impingement. The form of damage changed significantly when a curved sample was subjected to a high-speed impingement; the circular damage pattern observed on planar samples changed to an oval. This is qualitatively consistent with the theoretical predictions and constitutes another step forward in the understanding of the WDE of aeroengine fan blades.