Plunger Seal Assembly for Variable Exhaust Nozzle Gaps
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Solution Overview
Problem
Dynamic seals in gas turbine engine exhaust nozzles face challenges in effectively sealing gaps between movable components and stationary structures due to pressure and temperature variations, leading to leakage of core air, which reduces engine efficiency and thrust.
Innovation Solution
A plunger seal assembly comprising a plunger with a sealing edge, an actuating edge, a guide pin, and a biasing element, which is anchored to a housing and designed to accommodate sliding motion and variations in gap size, using high-temperature polymer or ceramic matrix composites to enhance conformability and reduce weight, while a double overlapped interface minimizes air excursion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dynamic seals are used in exhaust nozzles, then sealing is provided between movable and stationary components, but core air leakage occurs due to pressure and temperature variations, reducing engine efficiency
Solution Approach 1:
The seal assembly incorporates a plunger that can dynamically adjust its position along the longitudinal axis to accommodate variations in gap size between the movable flap and stationary sidewall. The biasing element enables the plunger to move automatically in response to pressure and temperature changes, maintaining effective sealing contact under varying operating conditions and preventing core air leakage.
Solution Approach 2:
The seal assembly utilizes changes in pressure and temperature parameters to its advantage. The biasing element is designed to respond to pressure differential changes across the seal, automatically adjusting the plunger position to maintain sealing effectiveness. The conformable sealing element adapts to thermal expansion and contraction, ensuring continuous sealing despite temperature variations in the exhaust nozzle environment.
2Reliability
If the seal assembly is designed to accommodate sliding motion and gap variations, then conformability and sealing effectiveness are improved, but the depth of the seal increases
Solution Approach 1:
The biasing element is nested within a recess formed in the plunger, allowing the plunger to move longitudinally while containing the biasing mechanism within a compact volume. This nesting arrangement enables the seal assembly to accommodate sliding motion and gap variations without requiring excessive depth, as the biasing element is housed efficiently within the plunger structure rather than extending externally.
Solution Approach 2:
The seal assembly transitions from a purely longitudinal adjustment mechanism to a multi-dimensional solution. The conformable sealing element provides radial compliance to accommodate gap variations, while the plunger provides longitudinal adjustment. This multi-dimensional approach allows the seal to handle complex movements and deformations without requiring excessive depth in any single dimension.
3Weight of moving object
If high-temperature polymer or ceramic matrix composites are used, then weight is reduced and conformability is enhanced, but manufacturing complexity increases
Solution Approach 1:
The seal assembly utilizes composite materials, specifically high-temperature polymer matrix composites or ceramic matrix composites, to achieve reduced weight and enhanced conformability. These composite materials provide the necessary strength-to-weight ratio and thermal resistance while allowing the sealing element to conform to surface variations. The composite structure enables the seal to operate in high-temperature exhaust nozzle environments while maintaining flexibility and reducing overall assembly weight.
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 plunger seal assembly effectively prevents core air leakage to the ambient environment, improves conformability, reduces the risk of binding, and minimizes the depth of the seal, thereby enhancing engine efficiency and thrust.
Implementation Method 1
a biasing element disposed to urge the at least one guide pin towards the actuating edge of the plunger, the at least one guide pin automatically moved towards the actuating edge of the plunger in response to a gap size between a movable flap and a stationary sidewall increasing
Data Source
AI summary
In some embodiments, apparatuses are provided herein useful to sealing a gap, such as a gap between a gas turbine engine nozzle flap and sidewall. An apparatus for sealing such a gap may be a plunger seal that includes a plunger, a retaining element, a guide pin, and a biasing element. The plunger includes a sealing edge and an actuating edge having at least one recess and an opening formed therein. The biasing element and a portion of the guide pin are nested in the recess. The retaining element anchor the plunger to the retaining element. The retaining element also anchors the plunger seal to the housing When installed in a gap, the housing engages the flap and the plunger engages the sidewall. The biasing element is under compression and urges the guide pin into the actuating edge to urge the plunger toward the sidewall and seal the gap.