Abradable Hydrostatic Seal Shoe for Gas Turbine Rub Tolerance
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Solution Overview
Problem
Existing seal assemblies in gas turbine engines are not adequately configured to handle deflections during emergency maneuvers, leading to potential rubs between the seal and rotating hardware, which can cause damage.
Innovation Solution
A hydrostatic seal assembly with a radially movable seal shoe and abradable seal teeth formed from a softer material, such as a babbitt alloy, to absorb any rubs and prevent damage, while maintaining a consistent air gap for efficient engine operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seal is configured to handle deflections during emergency maneuvers, then damage to the seal and rotating hardware is prevented, but the device complexity increases
Solution Approach 1:
The seal shoe is made radially movable relative to the seal support, allowing it to dynamically adjust its position in response to deflections during emergency maneuvers. This dynamic capability enables the seal to accommodate rotor deflection without damage while maintaining a relatively simple overall structure.
Solution Approach 2:
The seal teeth are formed from a softer material than the seal shoe body, creating a localized parameter change in material hardness. This softer material allows the teeth to be abraded rather than cause damage during contact with rotating hardware, providing a simple yet effective damage prevention mechanism.
2Productivity
If the seal shoe is made radially movable, then the air gap is maintained for efficient operation, but the device complexity increases
Solution Approach 1:
The seal shoe's radial movability allows it to maintain a consistent air gap with the rotating rotor despite pressure variations or minor deflections. This dynamic adjustment ensures efficient engine operation by preventing leakage while avoiding the need for complex active control systems.
3Reliability
If abradable teeth are used, then the risk of damage is reduced, but the manufacturing complexity increases
Solution Approach 1:
The seal teeth are formed from a softer material than the seal shoe body, creating a localized parameter change in material hardness. This softer material allows the teeth to be abraded rather than cause damage during contact with rotating hardware. The softer material can be applied through coating processes, which are relatively simple manufacturing techniques.
Solution Approach 2:
The seal shoe combines a harder base material with a softer coating material applied to the teeth surfaces. This composite structure provides the durability needed for the seal body while the softer teeth surface prevents damage to rotating hardware, and the coating can be applied through standard manufacturing processes.
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 solution effectively reduces the risk of damage to both the seal and rotating hardware by allowing radial movement of the seal shoe and using abradable teeth to absorb deflections, ensuring efficient operation and minimizing maintenance needs.
Implementation Method 1
the plurality of seal teeth are formed from a second material softer than the first material such that the plurality of seal teeth are abradable in the event of a rub between the plurality of seal teeth and an adjacent rotating component
Data Source
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AI summary
A hydrostatic seal assembly (60) includes a seal support (104), a seal shoe integral to the seal support and radially movable relative to the seal support. A plurality of seal teeth (100) are located at a radially inboard surface (102) of the seal shoe. The seal shoe is formed from a first material and the radially inboard surface is formed from a second material softer than the first material such that the radially inboard surface is abradable in the event of a rub between the radially inboard surface and an adjacent rotating component (64).