Brush Seal Bristle Pattern for Wear and Friction Reduction
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Solution Overview
Problem
Brush seal bristles in gas turbine engines experience wear and heat generation due to pressure differentials, leading to reduced sealing effectiveness over time.
Innovation Solution
An annular brush seal design with varying bristle lengths and patterns, including chamfers and hydrodynamic lift features, to manage pressure differentials and reduce wear and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform bristle lengths are used in the brush seal, then the seal structure is simple and easy to manufacture, but the bristle tips experience excessive wear and heat generation due to pressure differential forces
Solution Approach 1:
The brush seal employs bristles of varying lengths arranged in different patterns (gradual variation, circumferentially repeating, or random distribution) to create local variations in bristle tip positions. This local quality variation allows different bristle groups to experience different contact conditions with the rotor surface, distributing wear more evenly and reducing peak contact forces that cause excessive wear and heat generation at uniform bristle tips.
2Reliability
If longer bristles are used to improve sealing effectiveness, then the seal performance is enhanced, but the friction and heat generation increase during operation
Solution Approach 1:
By implementing bristles with varying lengths, the seal maintains effective sealing contact through the cumulative effect of multiple bristle rows while preventing excessive heat generation. The length variation ensures that not all bristles contact the rotor simultaneously, distributing the frictional heating across different bristle groups and reducing peak temperatures at any single location.
Solution Approach 2:
The varying bristle lengths create a more dynamic interaction with the rotating rotor surface, where different bristle groups engage and disengage in a sequenced manner. This dynamic distribution of contact forces reduces continuous frictional heating compared to uniform bristle lengths, where all bristles would experience simultaneous and continuous contact.
3Reliability
If the bristle pack is designed with varying bristle lengths to reduce wear, then the manufacturing complexity increases
Solution Approach 1:
The varying bristle length configuration achieves superior wear control through local quality variation in bristle dimensions. While this increases manufacturing complexity compared to uniform bristles, the patent provides specific guidance on acceptable variation patterns and ranges that can be implemented using conventional manufacturing techniques, balancing the trade-off between improved reliability and manufacturing feasibility.
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 reduces bristle tip wear and friction, maintaining effective sealing performance by controlling contact forces and generating hydrodynamic lift, thereby minimizing leakage and fuel consumption.
Implementation Method 1
The circumferentially repeating pattern may be configured to generate hydrodynamic lift when the brush seal seals a rotating member such as a shaft of a gas turbine engine.
Implementation Method 2
During operation, a pressure differential across the brush seal may act on the bristles of the brush seal, forcing the tips of the bristles against the adjacent component
Implementation Method 3
The at least one radially extending groove (if present) is configured to permit the application of a pressure force between the downstream bristles of the bristle back and the surface of the backing plate facing the bristle pack. This reduces frictional forces acting between the most downstream bristles and the backing plate, permitting easier movement of the downstream bristles.
Data Source
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AI summary
An annular brush seal (100) comprises a bristle pack (114) formed of bristles (112) and a bristle pack support (116), which supports the bristle pack (114). The bristle pack (114) has an upstream face (117), a downstream face (118) and a sealing face (119). The sealing face (119) comprises an upstream portion (119a) and a downstream portion (119b) that is adjacent to the upstream portion (119a). A length of at least a fraction of the bristles (112) of the upstream portion (119a) is shorter than a length of the bristles (112) of the downstream portion (119b) to form a circumferentially repeating pattern (160) at an interface between the upstream portion (119a) of the sealing surface (119) and the upstream surface (117).