Floating Brush Seal Assembly for Oil Leakage and Bristle Wear
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Solution Overview
Problem
Conventional seals in gas-turbine engine main shaft bearing compartments, such as carbon and labyrinth seals, fail to prevent oil leakage effectively, leading to imbalance and safety risks, while brush seals suffer from excessive wear during operation.
Innovation Solution
A floating brush seal assembly with a radially inwardly open housing, a brush seal with offset bristles, and a combination of radial and axial springs to absorb radial excursions and maintain proper sealing without excessive wear, along with a design that includes a backing plate, side plate, and a friction-reducing coating to minimize contact forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brush seals are used to seal the bearing compartment, then sealing performance is improved and cooling is not required, but excessive wear occurs on the bristles during operation
Solution Approach 1:
The brush seal assembly is made dynamically movable within the housing through radial and axial springs, allowing the bristle holder to float and adjust its position radially and axially during operation. This dynamic capability enables the seal to adapt to rotor excursions without excessive bristle wear while maintaining effective sealing.
Solution Approach 2:
The brush seal assembly is divided into separate functional components: a bristle holder containing the bristles, radial springs for radial positioning, axial springs for axial positioning, and a housing with floating gap. This segmentation allows each component to perform its specific function independently, with the radial and axial springs working together to reduce wear on the bristles while maintaining sealing effectiveness.
2Reliability
If conventional carbon seals are used to seal the bearing compartment, then sealing is achieved, but cooling oil is required which can leak into the compressor or turbine
Solution Approach 1:
The conventional carbon seal system that requires cooling oil is replaced with a brush seal system that does not require external cooling. The brush seal uses its own structure and spring mechanisms to maintain sealing effectiveness without requiring additional cooling oil that could leak into the compressor or turbine, thereby eliminating the harmful oil leakage effect.
3Device complexity
If the brush seal is fixed in position, then structural simplicity is maintained, but the seal cannot accommodate radial excursions of the rotating body
Solution Approach 1:
The brush seal transitions from a fixed position to a dynamically movable position within the housing. The radial and axial springs enable the bristle holder to float and adjust its position, allowing the seal to accommodate radial excursions of the rotating body while maintaining sealing effectiveness. This dynamic design balances structural simplicity with adaptability.
Solution Approach 2:
The radial and axial springs act as intermediary elements between the fixed housing and the movable bristle holder. These springs mediate the interaction by providing flexible connection that allows radial and axial movement while maintaining force balance, enabling the seal to accommodate excursions without requiring complex active control mechanisms.
4Stability of the object's composition
If the bristle holder is constrained to prevent rotation, then proper seal orientation is maintained, but friction and wear increase at the contact points
Solution Approach 1:
The bristle holder is given dynamic freedom to rotate slightly within controlled limits while the anti-rotation member prevents excessive rotation. This dynamic approach allows the bristle holder to self-adjust its orientation to minimize friction during operation while still maintaining proper seal orientation, reducing wear compared to a completely constrained design.
Solution Approach 2:
The degree of rotational constraint is optimized by adjusting the parameters of the anti-rotation member and the floating gap dimensions. This parameter optimization allows the bristle holder to have just enough rotational freedom to minimize friction and wear while maintaining sufficient orientation stability for effective sealing, balancing the two opposing requirements.
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 floating brush seal assembly effectively reduces oil leakage and wear on bristles, maintaining a robust seal and preventing oil from entering the compressor or turbine, thereby enhancing engine efficiency and safety by absorbing radial excursions and returning to a centered position.
Implementation Method 1
a radial spring positioned to exert a radial inwardly directed force against the brush seal relative to the housing
Implementation Method 2
the bristle holder is radially elastic so that a radial excursion of the rotating body against the brush seal moves the brush seal toward the radial spring, and the radial spring returns the bristle holder to a centered position
Implementation Method 3
an axial spring positioned to exert an axially directed force against the brush seal relative to the housing
Implementation Method 4
a friction reducing coating is provided at points of contact between the bristle holder and the backing plate
Data Source
AI summary
A floating brush seal assembly includes a ring-shaped housing defining a radially inwardly open internal cavity; a brush seal in the cavity and having bristles extending radially inwardly and offset to seal against a rotating body; a radial spring positioned to exert a radial inwardly directed force against the brush seal relative to the housing; and an axial spring positioned to exert an axially directed force against the brush seal relative to the housing.