Continued Experimental Study on the Friction Contact between a Labyrinth Seal Fin and a Honeycomb Stator: Slanted Position

Abstract

Labyrinth seals are a state-of-the-art sealing technology to prevent and control leakage flows at rotor-stator interfaces in turbomachinery. Higher pressure ratios and the economical use of cooling air require small clearances, which lead to potential rubbing events. The use of honeycomb liners allows for minimal leakage by tolerating rub events to a certain extent. A previous study within an EU project investigated the complex contact conditions of honeycomb liners, with the idealized contact of a seal fin and a single parallel metal foil representing the honeycomb double foil section. In the present work, the results for the slanted foil position are shown and compared to the previous results. The variation of rub velocity, incursion speed, incursion rate, and seal geometry in a test rig allows for the identification of the influence on contact forces, temperatures, and wear. For the slanted position, significantly lower friction temperatures are observed, leading to a higher ratio of abrasive wear. Overall, the rub test results demonstrate strong interactions between the contact forces, friction temperatures, and wear.

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

“…They found that maximum rubbing forces were not proportional to the incursion rate, and smearing appeared on the worn surface of honeycomb. Pychynski et al [ 12 , 13 ] idealized the contact of a honeycomb seal with the contact between a single metal foil and a seal fin to reduce the complexity of the research. The contact forces, friction temperature, and wear were measured.…”

The Influence of the Axial Rub Added in the Radial Rub on the Wear of the Seal Fins during the High Speed Rub of Labyrinth-Honeycomb Seal

“…In this paper, the test temperature of 350 °C softened the material and facilitated the wear debris to stick to the seal fins to form the tribo-layer. Also, the wear of the seal fins in this paper was noticeable, which facilitated the spalling of the tribo-layer, while the wear of the seal fins in [ 9 , 10 , 11 , 12 ] was negligible. Hence, the honeycomb used in the rub tests should be large enough and the test temperature should be similar to that in the aero-engine to better simulate the formation of the tribo-layer and reflect the fluctuation of the rubbing forces and temperature.…”

“…Accompanied by periodical formation and spalling of the tribo-layer, small peaks on the curves of rubbing force and temperature become obvious. In the test results in [ 9 , 10 , 11 ], the small peaks on the rubbing forces and temperature curves were not as obvious as that as shown in Figure 5 . However, these small peaks were more obvious in the tests results in [ 12 ], where the single metal foil was replaced by honeycomb liner with the angle of 7.2°.…”

“…The smearing on the worn surface of honeycomb was also observed. The Institute of Thermal Turbomachinery (ITS, Karlsruhe, Germany) has published a serious research on the rubbing behaviors between the seal fins and the honeycomb [ 9 , 10 , 11 , 12 ]. They first simplified the rub by replacing the honeycomb with a single metal foil.…”

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

“…Delebarre et al, [4][5][6] investigated the contact between a sealing fin and an Al-Si abradable material using a fully circumferential arrangement consisting of a single circular fin and abradable sample. 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.…”