NDLI: Study of Airflow Features Through Step Seals in the Presence of Dis-Engagement Due to Axial Movement

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Wang, Yi Young, Colin Snowsill, Guy Scanlon, Tim
Copyright Year	2004
Abstract	Step seals are a particular design variant of the basic labyrinth seal configuration which is widely used to limit leakage from the space between rotating and stationary components. Seals of this type are employed in aero-engines to prevent oil leakage from bearing chambers and to control the flow of secondary cooling air and it follows that the design of step seals is of great importance in the achievement of optimal aero-engine performance. In this paper, numerical modelling of the flow through stepped seals has been carried out in order to gain an insight into the behaviour of the flow in the presence of dis-engagement. In the context of this work, dis-engagement would be deemed to have occurred when to the axial movement between the rotor and stator results in a clear line of sight through the step seal. The flows through the seals were calculated using the commercial CFD package Fluent and the numerical predictions were validated by comparison with test data previously presented in the literature. The model predictions were initially obtained using a number of alternative two-equation turbulence models and the RNG k-ε turbulence model with the non-equilibrium wall function was found to be in closest agreement with the measured data. It was noted that for a given radial clearance the step seal’s flow characteristic is largely dictated by the fin tip to step distance. It was found that there are two distinct stages of step seal dis-engagement. The first stage of dis-engagement occurs when the seal fin is displaced axially from its nominal position, but the seal fin still remains within the axial extent of the corresponding seal step. In this case the flow through the seal only deviates slightly from that of the fully engaged seal. The second stage occurs when the fin is subjected to a larger axial displacement and as a result assumes a position beyond the corresponding seal step. This results in a much larger seal clearance and the flow through the seal increases significantly with the fin tip to step distance in the case.
Sponsorship	International Gas Turbine Institute
Starting Page	241
Ending Page	248
Page Count	8
File Format	PDF
ISBN	0791841693
DOI	10.1115/GT2004-53056
e-ISBN	0791837394
Volume Number	Volume 4: Turbo Expo 2004
Conference Proceedings	ASME Turbo Expo 2004: Power for Land, Sea, and Air
Language	English
Publisher Date	2004-06-14
Publisher Place	Vienna, Austria
Access Restriction	Subscribed
Subject Keyword	Leakage Turbulence Cooling Computational fluid dynamics Bearings Equilibrium (physics) Rotors Clearances (engineering) Aircraft engines Flow (dynamics) Modeling Displacement Design Air flow Stators
Content Type	Text
Resource Type	Article

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