Skirted Leaf Seal Assembly for Nozzle Flap Gap Sealing
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Solution Overview
Problem
Gas turbine engine exhaust nozzles experience leakage of core air due to gaps between movable flaps and stationary sidewalls, reducing thrust and efficiency, and existing dynamic seals face challenges in accommodating sliding motion, thermal variations, and pressure gradients while minimizing additional hardware complexity.
Innovation Solution
A skirted leaf seal assembly with a flap arm and wall arm, pre-loaded to exert a resilient force, biases away from each other to seal gaps between the flap and sidewall, accommodating sliding motion and dynamic variations in gap size, and includes a support arm to manage distortions and pressure loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a dynamic seal is added to seal the gap between the movable flap and stationary sidewall, then core air leakage is reduced, but device complexity increases
Solution Approach 1:
The seal apparatus is divided into two separate seals: a first seal attached to the movable flap and a second seal attached to the stationary sidewall. Each seal independently addresses the gap sealing function, allowing the system to reduce core air leakage while maintaining manageable complexity through modular design. The segmentation enables each seal to be optimized for its specific mounting condition and motion characteristics.
Solution Approach 2:
The first seal is designed with dynamic characteristics to accommodate the sliding motion of the movable flap relative to the stationary sidewall. The seal includes flexible elements and biasing mechanisms that allow it to adapt to changing gap sizes during operation, maintaining sealing effectiveness while the flap moves between different positions to control exhaust flow.
2Reliability
If the seal apparatus accommodates sliding motion and thermal variations, then sealing effectiveness is maintained, but device complexity increases
Solution Approach 1:
The seal apparatus incorporates elements that respond to parameter changes during operation. The first seal includes biasing mechanisms that adjust to thermal expansion and contraction, maintaining contact pressure between sealing surfaces despite temperature variations. The flexible construction allows the seal to adapt to dimensional changes in the flap and sidewall, ensuring continuous sealing effectiveness under varying thermal conditions.
Solution Approach 2:
The seal design allows for dynamic adjustment to accommodate sliding motion between the movable flap and stationary sidewall. The flexible seal elements can deflect and reposition themselves as the gap size changes during flap actuation, maintaining sealing contact without requiring complex mechanical adjustment mechanisms. This dynamic capability ensures reliable sealing throughout the full range of motion.
3Ease of manufacture
If the seal apparatus is designed to minimize weight and hardware complexity, then manufacturing cost is reduced, but sealing performance may deteriorate
Solution Approach 1:
By segmenting the sealing function into two separate seals mounted on different components, the design achieves effective sealing without requiring a single complex seal mechanism. Each seal can be manufactured as a relatively simple component attached to its respective mounting surface, reducing overall manufacturing complexity while maintaining sealing performance through the combined action of both seals.
Solution Approach 2:
The first seal incorporates biasing mechanisms that provide self-adjusting sealing force without requiring external actuation or complex control systems. The seal automatically adapts to gap variations through its resilient construction, eliminating the need for additional hardware to maintain sealing pressure, thereby reducing overall system complexity while preserving sealing effectiveness.
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
Effectively seals core air within the nozzle core, reducing leakage to the ambient environment, while minimizing weight and hardware complexity by adapting to dynamic conditions and maintaining efficient operation under thermal and pressure loads.
Implementation Method 1
a first seal or flap arm having a first proximal end portion, a first distal end portion with a first bend, and a first skirt extending away from the first bend; wherein the first seal biases away from the second seal to seal a gap between a moveable flap and a stationary structure
Data Source
AI summary
Apparatuses are provided herein useful to sealing a gap between a movable flap and a stationary structure, such as a gap between a gas turbine engine nozzle flap and a corresponding sidewall. An apparatus for sealing such a gap may be a dynamic skirted leaf seal which may include a flap arm, a wall arm opposite the flap arm, and a support arm disposed between the flap and wall arms. A distal end portion of the flap arm may comprise a first skirt and a distal end portion of the support arm may comprise a second skirt that engages the first skirt. When positioned in a gap, the skirted leaf seal may exert a force to urge the first flap arm towards the flap and to urge the wall arm and the support arm towards the structure to seal the gap.