Carbon Hydrostatic Face Seal for Turbomachine Rotor
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Solution Overview
Problem
Existing seals in gas turbine engines, such as labyrinth seals and gas bearing face seals, face issues with radial clearance limitations, imbalance, deformation, and inefficient venting, leading to leakage and potential engine damage or fires due to lubricant leakage.
Innovation Solution
A force-balanced seal using a stationary annular carbon graphite member with a face dam, groove, and air bearing surface, combined with passageways and orifices, is employed to maintain a balanced state and separate high and low pressure compartments using a hydrostatic thrust balance, ensuring concentric alignment and efficient fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ring member is pressed radially inwardly to maintain close spacing, then sealing capability is improved, but ring deformation to out-of-round shape occurs
Solution Approach 1:
Spring elements provide a radial outward biasing force that counteracts the inward pressing force from high pressure regions. This counterbalancing force prevents the ring member from deforming into an out-of-round shape while still allowing it to maintain close spacing to the rotor sealing surface for effective sealing.
Solution Approach 2:
The face seal ring member is made of carbon graphite, a composite material that combines the lubricating properties of graphite with the structural integrity of carbon. This material composition enables the ring to resist deformation under radial pressure while maintaining its roundness and sealing capability.
2Reliability
If auxiliary restrictor tooth is added to ring member to improve sealing, then sealing effectiveness is improved, but ring member weight and pressure closing forces increase
Solution Approach 1:
The auxiliary restrictor tooth is integrated into the face seal ring member structure, merging the sealing function with the existing ring component. This integration improves sealing effectiveness by creating additional flow restriction while minimizing the weight increase compared to adding a separate component.
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 seal effectively maintains a consistent operating clearance, prevents fluid leakage, and ensures a balanced state during both static and dynamic conditions, reducing the risk of engine damage and fires by efficiently venting air and maintaining a stable seal.
Implementation Method 1
A stationary annular carbon graphite member with a face dam, groove, and air bearing surface, combined with passageways and orifices, is employed to maintain a balanced state and separate high and low pressure compartments using a hydrostatic thrust balance
Implementation Method 2
During higher power operation high pressure compressor discharge air acts on the ring to urge the ring and tooth toward the sealing surface. A portion of the high pressure discharge air is supplied to a gas bearing space between the ring and the rotating sealing surface to establish a predetermined gas bearing face clearance
Implementation Method 3
The seal effectively maintains a consistent operating clearance, prevents fluid leakage, and ensures a balanced state during both static and dynamic conditions
Data Source
AI summary
A force balanced seal for use with a rotor in the turbomachine has a member in opposed facing disposition to the rotor with a face dam portion of the member having a surface parallel with the sealing surface of the rotor, a groove in the member facing the rotor and bounding the face dam surface, an air bearing surface in the member facing the sealing surface of the rotor, a second passageway through the member from the air bearing surface to a radially outwardly facing surface of the member and a first passageway through the member from the groove to a member surface facing oppositely from the air bearing surface. An operating clearance between the seal and rotor is maintained by a closing force, exerted through a plurality of springs, and an opposing opening force created by pressurized air venting through the second passageway to the first passageway.