Rotating Labyrinth Seal Crack Prevention via Segmented Design
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Solution Overview
Problem
Conventional rotating labyrinth seals in gas turbine engines are prone to cracking due to rub damage, which can propagate into the torque-carrying load path, leading to hazardous events such as turbine overspeed and disc burst, and result in increased economic costs for inspections and coatings.
Innovation Solution
The introduction of a separate component within the seal geometry that separates the seal from the load transmitting structures, and the use of notches in the seal fins to reduce hoop stress and prevent crack propagation, along with alternative attachment mechanisms such as retaining rings, bolts, and bayonet features to secure the seal in place.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the seal teeth are made thin to thermally isolate them from the base, then thermal isolation is improved, but susceptibility to handling damage and crack initiation increases
Solution Approach 1:
The seal structure is divided into separate components: the seal teeth are made as a distinct element that can be attached to the base structure. This segmentation allows the thin teeth to provide thermal isolation while the separate base structure provides strength and crack resistance, resolving the contradiction between thermal isolation and damage susceptibility.
2Strength
If the seal teeth are integrated into the shaft or disc structure, then structural strength is improved, but crack propagation into the load path becomes possible
Solution Approach 1:
The seal teeth are extracted from the integral structure and made as a separate attachable component. This extraction creates a discontinuity in the load path, preventing crack propagation from the seal teeth into the shaft or disc structure, while the seal teeth remain attached to provide sealing function.
Solution Approach 2:
A separate seal tooth structure acts as an intermediary element between the base structure and the sealing function. This intermediary component isolates the load-carrying structure from crack initiation and propagation, allowing the thin seal teeth to perform sealing while the base structure maintains structural integrity.
3Strength
If conventional attachment methods are used to secure the seal to the shaft, then attachment strength is improved, but crack propagation into the torque-carrying structure remains possible
Solution Approach 1:
The seal attachment system is extracted from the integral structure, creating a separate attachable seal component. This extraction breaks the continuous load path, preventing crack propagation while maintaining secure attachment through dedicated attachment features.
Data Source
AI summary
A rotating labyrinth seal especially useful for effecting sealing between two plenums in aircraft gas turbine engines comprising a base and a plurality of radially-directed seal teeth rings extending circumferentially around the outer peripheral surface of the base. The seal separated from a load transmitting component via abutting surfaces which prevent cracks from migrating into the load transmitting component from the seal.