In situ measurements of thermal-mechanical wear in blade-abradable liner contacts

Abstract

The abradable coating on the casing of a jet engine minimises any air gaps by allowing blades to cut a path into the abradable, reducing efficiency losses. Unfortunately, abradable cutting performance varies significantly with rub conditions and abradable type, leading to poor cutting performance and potentially damaging the blades. This study further develops the abradable testing capabilities of a 200 m/s spindle test rig by applying previously researched stroboscopic imagining techniques to record the front of the blade alongside thermal imaging of the blade and the abradable. The front camera makes it possible to see how adhesions are forming along the width of the blade, and how the adhesion growth differs between materials. The thermal camera can then be used to identify hot spots on both the blade and the abradable, providing an insight into how hot spots relate to adhesions both spatially and temporally. These tools have been proven with testing of Metco 601 at a range of incursion rates. At the incursion rate of 0.2 μm/pass the tools were able to provide conclusive results, with video footage of the front, side, blade temperature and abradable temperatures being aligned temporally and spatially. Numerical data could then be extracted to produce rub maps of adhesion height, blade temperature and abradable temperature on separate plots which is a powerful tool when looking for relationships between the data sets, and for identifying time-based patterns. Further benefits of this tool set were shown when focussing on individual adhesions events within a rub, allowing for the delays between abradable heating, adhesions forming and blade heating to be observed and quantified. When applied to multiple materials and at different test conditions this tool will provide further insight into how adhesion formation differs, and potentially into why adhesions form.