The Wear of Seal Fins during High-Speed Rub between Labyrinth Seal Fins and Honeycomb Stators at Different Incursion Rates

Abstract

Labyrinth seals as a noncontact sealing technology are widely used in aero-engine. To improve the efficiency of the aero-engine, the clearance between the rotor and stator must be as small as possible. However, the change of the clearance between the rotor and stator because of thermal expansion, vibration, mechanical loading may lead to undesirable high-speed rub, which will lead to the cracking of the seal fins. This paper focuses on the wear of the seal fin after the rub and presents the rubbing tests between seal fins and the metal honeycomb under rubbing speed of 380 m/s and incursion rates between 20 and 180 μm/s, with an incursion depth of 1500 μm and a temperature of 350 °C. The rubbing force and temperature were recorded, and the seal fins were checked by SEM and EDS. The results show that the wear mechanism of seal fins changed from oxidation wear and adhesive wear to delamination wear and then to metal wear with the increasing incursion rate. The axial cracks appeared on the worn surface of the seal fins due to the cracking of tribo-layers under periodic thermomechanical stress. The wear mechanism of the seal fin also has a great influence on the rubbing force and temperature.

An investigation into the role of specimen geometry when undertaking tribological testing on seal fin components

“…However, it is also noticeable once again that for the longer fins, and in particular for the segmented test sample, that larger, extruded chips of material are also formed. Comparing back to previous results, 2,10 the influence of incursion speed is well documented, and the expected transition from compression/release through to displacement of material occurs as this parameter increases. However, it is interesting to note the influence of fin length on these two mechanisms, and this requires further consideration.…”

“…Recently, Lu investigated the wear behaviour of honeycomb abradable with segmental fin samples [10] Whilst as discussed these test arrangements go some way to addressing the aforementioned issues surrounding single fin testing, they represent a more complex test, and as such less repeat tests are performed, as well as reduced instrumentation to investigate the contact mechanics. Comparing back to work on compressor blade -liner interactions [11][12][13][14], increased insight with respect to wear mechanics has been achieved via a simple, easy to instrument test, where multiple repeats can be performed.…”

“…Recently, Lu et al. 10 investigated the wear behaviour of honeycomb abradable with segmental fin samples. Whilst as discussed these test arrangements go some way to addressing the aforementioned issues surrounding single fin testing, they represent a more complex test, and as such less repeat tests are performed, as well as reduced instrumentation to investigate the contact mechanics.…”

“…Similarly, a continuous circular fin was also employed in Pychynski et al's, 7 Munz et al's 8 and Th evenot et al's 9 studies where the wear behaviour of a labyrinth-honeycomb seal system was investigated. Recently, Lu et al 10 investigated the wear behaviour of honeycomb abradable with segmental fin samples. Whilst as discussed these test arrangements go some way to addressing the aforementioned issues surrounding single fin testing, they represent a more complex test, and as such less repeat tests are performed, as well as reduced instrumentation to investigate the contact mechanics.…”

Investigating Al-Si base abradable material removal mechanism with axial movement in labyrinth seal system

“…In this latter case, engine data suggests that a typical turbine fin can move at a rate of 1.5mm/s, or the equivalent of 10 microns per revolution considering the test rig used to investigate fin seals previously [1]. Fig 1 shows an example of a fin seal contact subject to axial motion, where the fin first moves radially into the liner, following a path investigated in multiple previous studies [1,5,6], before progressing in the axial direction. In this latter case (Fig 1c), the fin makes contact with the side of the groove generated by the radial incursion, resulting in significantly different contact mechanics to that investigated previously.…”