Piston Seal Assembly Anti-Rotation for Stable Gap Offset
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Solution Overview
Problem
Existing piston seal assemblies in bleed air systems for gas turbine engines face challenges in maintaining effective fluid sealing and limiting relative circumferential movement, leading to leakage and performance degradation due to thermal expansion and vibration-induced changes in the offset angle between the ring and seal gaps.
Innovation Solution
The introduction of an anti-rotation feature, which includes a ring and seal assembly with a circumferentially offset ring and seal gap, and protrusions or recesses to limit relative circumferential movement within a threshold rotation limit, maintaining consistent leakage characteristics and sealing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piston seal assembly is used in bleed air systems, then fluid sealing is facilitated, but relative circumferential movement between ring and seal occurs due to thermal expansion and vibration, leading to leakage and performance degradation
Solution Approach 1:
The anti-rotation feature is pre-configured with protrusions and recesses that engage before thermal expansion or vibration occurs, establishing a fixed reference relationship between the ring and seal gaps. This preliminary geometric constraint prevents subsequent circumferential drift that would otherwise occur during operation.
Solution Approach 2:
The anti-rotation feature acts as an intermediary element between the ring and seal, using its protrusions and recesses to mediate their relative positioning. This intermediary structure transfers and maintains the correct angular relationship without requiring direct constraint between the ring and seal themselves.
2Temperature
If the ring and seal are allowed to move freely to accommodate thermal expansion, then thermal stress is reduced, but fluid leakage increases due to changes in the offset angle
Solution Approach 1:
The seal assembly is segmented into distinct functional zones: the ring body and seal body can expand thermally independently, while the anti-rotation feature with its protrusions and recesses provides a separate constraint mechanism. This segmentation allows thermal expansion without compromising the angular relationship critical for preventing leakage.
Solution Approach 2:
The anti-rotation feature uses asymmetric protrusions and recesses positioned at specific circumferential locations to create a unidirectional constraint. This asymmetric geometry allows the ring and seal to expand thermally while maintaining a fixed offset angle, preventing the symmetric rotation that would lead to leakage.
3Reliability
If an anti-rotation feature is added to limit circumferential movement, then sealing consistency is improved, but device complexity increases
Solution Approach 1:
The anti-rotation feature is merged with the existing ring and seal structures by integrating protrusions and recesses directly into their bodies. This combining approach eliminates the need for separate anti-rotation components, reducing overall device complexity while maintaining the leakage control function.
Solution Approach 2:
The anti-rotation feature with its protrusions and recesses serves multiple functions simultaneously: it prevents circumferential rotation, maintains the optimal offset angle, and provides a reference for proper assembly. This multi-functionality reduces the need for additional components, offsetting the complexity increase through functional consolidation.
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 anti-rotation feature effectively limits circumferential movement between the ring and seal, maintaining consistent leakage characteristics and sealing efficiency, reducing fluid leakage and enhancing the operational stability of the bleed-off valve by maintaining the optimal offset angle and accommodating thermal expansion.
Implementation Method 1
The ring body and the seal body form an anti-rotation feature of the piston seal assembly. The anti-rotation feature configured to limit relative circumferential movement between the ring body and the seal body.
Data Source
AI summary
A piston seal assembly includes a ring and a seal. The ring includes a ring body. The ring body extends circumferentially about a centerline axis. The ring body extends circumferentially between a first circumferential ring end and a second circumferential ring end. The ring body forms a ring end gap between the first circumferential ring end and the second circumferential ring end. The seal includes a seal body. The seal body extends circumferentially about the centerline axis. The seal body extends circumferentially between a first circumferential seal end and a second circumferential seal end. The seal body forms a seal end gap between the first circumferential seal end and the second circumferential seal end. The ring body and the seal body form an anti-rotation feature of the piston seal assembly. The anti-rotation feature configured to limit relative circumferential movement between the ring body and the seal body.