Variable Width Gap Seal for Aircraft Exhaust Thermal Growth
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Solution Overview
Problem
Aircraft exhaust systems face challenges in maintaining consistent sealing efficiency across varying interface widths due to thermal growth differences between materials, leading to air leakage and performance issues.
Innovation Solution
A seal design incorporating a sheet with a fixed end, cover portion, movable portion, and tensioning element, along with an expansion element and spacing elements, which accommodates changes in interface width by maintaining a constant gap for cooling air, ensuring effective sealing across varying temperatures and material growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fixed seals are used between exhaust components, then sealing is effective at a specific interface width, but sealing efficiency deteriorates when interface width changes due to thermal growth
Solution Approach 1:
The seal assembly incorporates a movable portion that can shift position along the interface to accommodate changes in interface width. The tensioning element dynamically adjusts to maintain proper seal contact pressure regardless of thermal expansion or contraction, allowing the seal to adapt to varying interface dimensions while maintaining sealing efficiency
Solution Approach 2:
The seal is divided into distinct functional segments: a fixed end anchored to one component, a movable portion that can shift to accommodate width changes, and a free end with tensioning elements. This segmentation allows each portion to perform its specific function - the fixed end provides stable anchoring, the movable portion absorbs dimensional changes, and the tensioning elements maintain contact pressure
2Reliability
If the seal is made rigid to maintain sealing contact, then sealing efficiency is improved, but the seal cannot accommodate thermal growth differences between materials
Solution Approach 1:
The seal utilizes a flexible sheet material that can bend and deform to accommodate thermal growth differences between the exhaust deck and trailing edge. This flexibility allows the seal to conform to changing interface geometries while maintaining continuous contact for effective sealing
Solution Approach 2:
The movable portion of the seal is designed to dynamically adjust its position and shape in response to thermal expansion or contraction of the interface materials. This dynamic adjustment capability allows the seal to maintain sealing effectiveness without rigid constraints that would prevent thermal growth accommodation
3Adaptability or versatility
If the interface width varies due to thermal growth, then adaptability to temperature changes is improved, but air leakage increases and sealing efficiency deteriorates
Solution Approach 1:
The tensioning element continuously applies force to keep the cover portion taut and maintain proper seal contact pressure as the interface width changes with temperature. This dynamic tensioning ensures that the seal remains effective across the full range of thermal conditions without air leakage
Solution Approach 2:
The separation of fixed and movable portions allows the seal to accommodate temperature variations - the fixed end remains stable while the movable portion adjusts to interface width changes, preventing air leakage while maintaining sealing efficiency across different temperatures
4Adaptability or versatility
If a movable portion is added to accommodate interface width changes, then adaptability is improved, but device complexity increases
Solution Approach 1:
The movable portion is implemented as a simple flexible sheet component that naturally bends and shifts to accommodate interface width changes. This flexible film approach provides the needed adaptability without complex mechanical linkages, joints, or actuation mechanisms, thereby limiting the increase in device complexity
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 seal effectively maintains a consistent cooling air gap and sealing efficiency despite changes in interface width, protecting components from thermal stresses and enhancing aircraft performance.
Implementation Method 1
The tensioning element is attached to the free end and provides tensioning force keep the cover portion taut
Implementation Method 2
The spacing element engages the movable portion and defines a gap for cooling air between the movable portion and the aircraft exhaust deck
Implementation Method 3
The expansion element is located between the first fitting and the second fitting. The expansion element exerts an expansion force against both the first fitting and second fitting to accommodate changes in interface size
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A seal (10;94;170) for bridging an interface (16;100;176) between an aircraft exhaust deck (14;98;174) and a trailing edge (12;96;172) of an aircraft exhaust system includes a sheet (42;122;196), a spacing element (90, 164), and a tensioning element (44;124;198). The sheet has a fixed end (68;152;218), a cover portion (69;150;216), a movable portion (71;151;217), and a free end (70;148;214). The fixed end is anchored to the trailing edge. The cover portion extends upstream from the fixed end and across the interface. The movable portion is located adjacent the aircraft exhaust deck. The spacing element engages the movable portion and defines a gap (18) for cooling air between the movable portion and the aircraft exhaust deck. The tensioning element is attached to the free end and provides tensioning force keep the cover portion taut.