Leaf Seal Manufacturing Process for Gas Turbine Engines
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Solution Overview
Problem
Existing methods for forming leaf seals in gas turbine engines face challenges in efficiently presenting leaf edges for effective sealing, leading to inadequate control of spacing between leaf edges, which can result in either large gaps or excessive contact, compromising the sealing effectiveness.
Innovation Solution
A process involving a sheet of uniform thickness with defined leaf, root, and spacer sections, where the root and spacer sections are thinned while maintaining the leaf section's thickness, allowing the spacer to overlay the root and the leaf to extend, forming a leaf-spacer pair or stack with controlled spacing, achieved through folding and thinning along specific lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pleated band or strip is used to form leaf seals, then the assembly process is simplified, but the leaf edges are not efficiently presented towards the sealing surface and significant strain occurs at the folded corners
Solution Approach 1:
The leaf seal is divided into multiple individual leaves rather than using a continuous pleated band. Each leaf is a separate element that can be independently positioned and oriented, allowing the edges to be efficiently presented towards the sealing surface without the strain and misalignment issues of folded bands.
Solution Approach 2:
The invention transitions from a two-dimensional folded band to a three-dimensional stacked arrangement of leaves. The leaves are stacked with their edges aligned to present a continuous sealing surface, adding the dimension of vertical stacking to achieve proper edge presentation without the constraints of planar folding.
2Reliability
If leaves are closely spaced to improve sealing, then sealing effectiveness increases, but control of spacing becomes inadequate leading to either large gaps or excessive contact
Solution Approach 1:
Spacer elements are introduced as intermediary components between adjacent leaves. These spacers precisely control the spacing between leaves, maintaining an optimal gap that prevents both large openings and excessive contact. The spacers act as mediators that enable close spacing for sealing effectiveness while eliminating spacing control issues.
3Ease of manufacture
If the sheet is thinned to allow folding and spacer formation, then the leaf-spacer pair can be formed, but the leaf section may become too thin to maintain structural integrity and surface finish
Solution Approach 1:
The sheet is thinned only in specific local regions where folding and spacer formation are required, while the leaf sections retain their original thickness. This selective thinning approach allows the manufacturing process to proceed while maintaining the structural integrity and surface finish of the critical leaf sealing surfaces.
Solution Approach 2:
The sheet is divided into distinct functional zones: leaf sections that maintain full thickness for strength, and root/spacer sections that are thinned to enable folding and spacer formation. This segmentation allows different parts of the same component to have different thicknesses optimized for their specific functions.
Data Source
AI summary
A first process is provided for forming a stack of leaves for use in a leaf seal which effects a seal between two components. Corresponding processes are provided for forming a leaf-spacer pair and then for forming a stack of leaves from such pairs. Each leaf of the stack has a leaf section which maintains wiping contact with one of the components and a root section which is fixed relative to the other component and from which the leaf section extends. The stack includes a plurality of spacers which interpose between the root sections.