Multi-ply Finger Seal Thermal Expansion Design
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Solution Overview
Problem
Gas turbine engine seals face extreme stresses due to varying temperatures and pressures, causing undesirable shape changes and potential failure, and existing solutions do not effectively manage these conditions to ensure reliable sealing.
Innovation Solution
A multi-ply finger seal design featuring a first ply and a second ply with different coefficients of thermal expansion and stiffness, allowing for tailored contact with a seal land surface through thermal expansion and stiffness mismatches, which generates forces to maintain or adjust sealing contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-material seal is used, then the structure is simple, but the seal cannot maintain consistent contact under varying temperatures and pressures
Solution Approach 1:
The seal is constructed from multiple plies of material with different coefficients of thermal expansion. This composite structure allows the seal to maintain consistent contact with the seal land surface under varying temperatures and pressures, as the differential expansion between layers compensates for thermal distortion and maintains sealing force.
Solution Approach 2:
The patent utilizes changes in physical parameters (coefficient of thermal expansion) of different materials to achieve the desired sealing performance. By selecting materials with specific thermal expansion properties, the seal adapts its contact characteristics in response to temperature and pressure changes, maintaining reliable sealing without structural complexity.
2Reliability
If expensive high-performance materials are used throughout the seal, then sealing performance is optimized, but material costs increase
Solution Approach 1:
Different plies of the seal are constructed from materials with different coefficients of thermal expansion, optimizing each layer's contribution to sealing performance. This allows the use of specialized materials only where needed rather than throughout the entire seal structure, reducing overall material costs while maintaining reliable sealing performance under varying operational conditions.
3Reliability
If the seal is designed to maintain contact under all conditions, then sealing reliability is improved, but stress on the seal increases
Solution Approach 1:
The multi-ply structure with different thermal expansion coefficients allows the seal to maintain contact through differential expansion rather than uniform high stress. The materials' natural response to temperature changes generates the necessary sealing force, reducing the mechanical stress burden on the seal structure while maintaining reliable contact under varying operational conditions.
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
The design enhances safety margins and allows for the use of less expensive materials while optimizing sealing performance by managing stresses and maintaining contact with the seal land surface effectively.
Implementation Method 1
The first ply is constructed from a first material that has a first coefficient of thermal expansion. The second ply is constructed from a second material having a second coefficient of thermal expansion that differs from the first coefficient of thermal expansion. The difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion generates a force that acts to move the second ply toward contact with the seal land surface.
Implementation Method 2
The difference in stiffness between the first ply and the second ply is due to one of a temperature or strain induced phase change. At least one of the first ply and the second ply is comprised of a shape memory alloy.
Data Source
AI summary
A multi-ply finger seal with a first ply that is subject to a first amount of deflection during operation of the gas turbine engine and a second ply that is subject to a second amount of deflection during operation of the gas turbine engine. The first amount of deflection of the first ply differs from the second amount of deflection of the second ply. The differing amounts of deflection can result from the first ply and second ply being constructed from materials that have different coefficients of thermal expansion. Additionally or alternatively, the first ply can have a stiffness that differs from the stiffness of the second ply.