Carbon Face Seal Pressure Boosting for Low-Speed Leakage Control
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Solution Overview
Problem
Gas turbine engines face challenges in maintaining effective sealing at low rotational speeds due to low fluid pressure, which compromises the ability of hydrodynamic grooves to generate sufficient pressure for sealing, leading to increased leakage and wear.
Innovation Solution
A pressure boosting mechanism is introduced, utilizing a cavity in the seal plate coupled with a gap and angled holes to enhance fluid pressure delivery to hydrodynamic features, such as spiral grooves, by imparting rotational components to the fluid, thereby increasing the pressure within the grooves and reducing leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrodynamic grooves are used to generate sealing pressure, then sealing effectiveness is improved at normal rotational speeds, but sealing pressure becomes insufficient at low rotational speeds due to low fluid pressure
Solution Approach 1:
The seal plate introduces fluid into the grooves before the rotor reaches full operational speed, ensuring that sealing pressure is established in advance. This preliminary fluid introduction occurs through dedicated fluid introduction holes that deliver fluid directly to the groove entrances, allowing the hydrodynamic seal to become effective earlier in the acceleration process and maintain reliability at low rotational speeds.
Solution Approach 2:
A fluid introduction mechanism acts as an intermediary between the fluid source and the hydrodynamic grooves. This intermediary system includes fluid introduction holes in the seal plate and potentially a fluid source positioned to deliver fluid directly to the groove entrances, mediating the fluid delivery to ensure adequate pressure is provided to the grooves even when rotational speed is low.
2Loss of substance
If fluid pressure is increased to improve sealing at low speeds, then leakage is reduced, but the complexity of the fluid delivery system increases
Solution Approach 1:
The seal plate performs multiple functions: it serves as a structural component of the seal assembly, a fluid distribution manifold with integrated fluid introduction holes, and a support for the hydrodynamic grooves. By combining these functions into a single component, the design reduces overall system complexity while still achieving the goal of increased fluid pressure for reduced leakage at low speeds.
Solution Approach 2:
The seal plate utilizes its own structure to deliver fluid to the grooves through integrated fluid introduction holes, rather than requiring a separate external fluid delivery system. The rotor shaft or housing may serve as the fluid source, and the seal plate itself manages the fluid distribution, making the system self-sufficient and reducing the number of additional components needed.
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
This solution extends the usable lifetime of seals by minimizing wear and reducing leakage through increased differential pressure across the carbon seal and seal plate, particularly at low shaft speeds, enhancing hydrodynamic lift and sealing efficiency.
Implementation Method 1
enhancing hydrodynamic lift and sealing efficiency
Implementation Method 2
The fluid is pumped within the spiral grooves 234, raising the pressure thereof such that the elevated pressure of the fluid within the grooves 234 forms a fluid barrier
Data Source
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AI summary
Aspects of the disclosure are directed to a system (300;400;500) associated with an engine (10) of an aircraft, the system (300;400;500) comprising a fluid source (240) that is configured to provide a fluid at a first pressure value, a carbon seal (210), a seal plate (216) that includes at least one lift-off feature (234') that interfaces to the carbon seal (210), and a pressure boosting mechanism configured to obtain the fluid from the fluid source (240), increase the pressure of the fluid to a second pressure value, and provide the fluid at the second pressure value to the at least one lift-off feature (234').