Leaf Seal Block Segmentation for Vibration Damping
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Solution Overview
Problem
Leaf seals in gas turbine engines face issues with fatigue cracking due to vibrations, particularly in large diameter applications where significant leaf-to-leaf interference at the tips is not feasible, leading to limitations in seal diameter and potential loss of material.
Innovation Solution
The solution involves forming an annular pack of leaves into blocks separated by spacers, allowing for increased leaf-to-leaf interference and frictional contact, which dampens vibrations and reduces fatigue cracking, while maintaining compliance and sealing effectiveness through adjustable spacer distribution and surface treatments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If leaves are arranged in a continuous pack without blocking, then sealing coverage is improved, but vibration-induced fatigue cracking increases
Solution Approach 1:
The continuous pack of leaves is segmented into multiple blocks by introducing blocking elements that create gaps between leaf groups. This segmentation reduces vibration-induced fatigue cracking while maintaining sealing effectiveness through the combined action of multiple leaf blocks.
Solution Approach 2:
Blocking elements are introduced as intermediary components between leaf blocks. These elements serve as mediators that reduce harmful vibrations and fatigue cracking while allowing the leaf edges to maintain contact with the sealing surface.
2Object-affected harmful factors
If blocking elements are introduced to reduce fatigue cracking, then leaf vibration damage is reduced, but leakage flow increases
Solution Approach 1:
The blocking elements are designed with specific local properties - they are positioned to block leakage paths at certain locations while allowing vibration reduction. The blocking elements create localized interference patterns that reduce vibration amplitude without creating continuous leakage paths.
Solution Approach 2:
The blocking elements are designed to interact dynamically with the leaf vibrations, creating a system where the blocking action is optimized for vibration reduction while minimizing leakage. The arrangement allows the leaves to flex and contact the sealing surface while the blocks provide dynamic damping.
3Object-affected harmful factors
If leaf-to-leaf interference is increased to reduce fatigue cracking, then vibration damping is improved, but device complexity increases
Solution Approach 1:
The leaf pack is segmented into blocks with standardized geometries, reducing the overall complexity compared to designing custom interference patterns for the entire pack. Each block can be designed and analyzed independently, simplifying the overall design process.
Solution Approach 2:
The invention controls vibration and fatigue cracking by changing key parameters such as block spacing, block size, and gap dimensions rather than complexly varying leaf geometries throughout the entire pack. This parameter-based approach simplifies design and manufacturing.
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 configuration enhances the sealing performance by reducing fatigue cracking and vibration-induced damage, allowing for larger diameter seals with improved leakage control and mechanical stiffness, while maintaining a compliant seal.
Implementation Method 1
respective edges of the leaves are presented for wiping contact with the other component
Implementation Method 2
the spacers are distributed around the pack such that the leaves are divided into blocks of two or more leaves sandwiched at their root portions between nearest-neighbour spacers
Implementation Method 3
Each leaf is generally compliant in order to adjust with rotation of the surface to ensure that a good sealing effect is created
Implementation Method 4
Large leaf-to-leaf interference at the tips has been seen to alleviate this problem. A similar effect has also been seen with very thick leaves.
Data Source
AI summary
A leaf seal is provided for effecting a seal between two coaxial, relatively rotating components. The leaf seal has an annular pack of leaves which are stacked face-to-face within the pack, and which are mountable to one of the components at respective root portions of the leaves such that the leaves extend towards the other component and respective edges of the leaves are presented for wiping contact with the other component. The pack includes a plurality of spacers, each spacer separating the root portions of neighboring leaves to form therebetween interleaf gaps which allow an axial leakage flow through the pack. The spacers are distributed around the pack such that the leaves are divided into blocks of two or more leaves sandwiched at their root portions between nearest-neighbor spacers.