Finger Seal Interface With Deflection Stop and Diaphragm
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining effective sealing due to irregular component profiles, tolerances, and large deflections, leading to potential permanent deformation of metallic finger seals, which compromises sealing effectiveness, especially in constrained spaces.
Innovation Solution
The solution involves an adaptive seal assembly for gas turbine engines that includes a finger seal with conical lead-in sections and a diaphragm with ripples, allowing for nominal deflection accommodation while preventing excessive deformation during transient conditions by transferring additional deflection to a stop and diaphragm, maintaining sealing effectiveness across a range of engine operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the packaging geometry of the seal is increased to accommodate a larger range of motion/deflection, then the seal can handle larger deflections, but physical space is consumed in the engine
Solution Approach 1:
The seal is divided into multiple fingers that can deflect independently. Each finger is segmented into a head portion and a stem portion, allowing distributed deflection across multiple elements rather than requiring a single large seal structure. This segmentation enables the seal to accommodate large relative motions between components while maintaining a compact overall packaging geometry.
Solution Approach 2:
The seal transitions from a static structure to a dynamic one where the fingers can deflect elastically within their elastic limits. The fingers are designed to bend and flex in response to varying deflection demands, adapting their shape to maintain sealing contact under different operating conditions without requiring excessive packaging space.
2Reliability
If the seal is designed for normal range of motion within elastic strain, then sealing effectiveness is maintained, but the seal cannot accommodate large magnitude deflections without permanent plastic deformation
Solution Approach 1:
The seal fingers are pre-designed with specific geometric features (tapered stems, optimized thickness profiles) that provide elastic cushioning capacity before permanent deformation occurs. This preliminary design ensures that during transient events with large deflections, the fingers absorb the excessive motion through elastic deformation and geometric compliance, cushioning against plastic deformation and maintaining sealing reliability.
Solution Approach 2:
The seal geometry parameters (finger thickness, stem taper ratio, head portion dimensions) are optimized to change the mechanical properties of the seal. By carefully selecting these parameters, the seal achieves sufficient elastic deformation capacity to accommodate large deflections while remaining within elastic limits under normal operating conditions, thus expanding the usable deflection range without sacrificing reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This assembly ensures effective sealing both under normal and abnormal engine conditions without causing permanent deformation, maintaining compliance and sealing capability even during extreme maneuvers, thus enhancing engine stability and performance.
Implementation Method 1
Under excessive deflection (e.g., deflection exceeding a threshold), the seal may be crushed or deflected to the point where permanent plastic deformation occurs. This deformation results in loss of subsequent sealing capability/effectiveness.
Data Source
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AI summary
Aspects of the disclosure are directed an engine having a central longitudinal axis, comprising: a first case that at least partially defines a first flow path (B), a second case located radially outward of the first case, where the second case and the first case at least partially define a second flowpath (C), and an assembly that includes a first duct wall (322), a second duct wall (340), a finger seal (424) disposed in a gap defined between the first duct wall (322) and the second duct wall (340) such that a first flow in the first flow path (B) is isolated from a second flow in the second flowpath (C), a stop (406) that projects from the first duct wall (322) towards the second duct wall (340), and a diaphragm (430) coupled to the second duct wall (340).