Hybrid Seal with Stacked Elements for Turbomachinery
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Solution Overview
Problem
Current seal technologies in turbomachinery, such as labyrinth, brush, and carbon seals, face issues with leakage, heat generation, vibration, and directional limitations, which affect engine performance and reliability, particularly in applications like gas turbine engines.
Innovation Solution
A hybrid non-contact seal design featuring a shoe with spring elements and side-by-side sealing elements that create both primary and secondary seals, allowing for flexible radial movement and maintaining effective sealing under pressure loads, reducing the dependency on precise radial clearances and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If labyrinth seals are used to seal the circumferential gap, then sealing effectiveness is improved, but radial clearance tolerance sensitivity increases and heat generation occurs
Solution Approach 1:
The seal shoe is designed to be movable in the radial direction, allowing it to dynamically adjust its position relative to the rotor surface. This dynamic capability enables the seal to maintain effective clearance under varying operating conditions without requiring extremely tight manufacturing tolerances, thus resolving the contradiction between sealing effectiveness and radial clearance tolerance sensitivity
Solution Approach 2:
The invention changes the clearance parameter from a fixed value to a variable that can adjust within a range. By allowing the seal shoe to move radially, the system can adapt clearance parameters to different operating conditions, reducing sensitivity to initial manufacturing tolerances while maintaining sealing effectiveness
2Reliability
If brush seals are used to reduce leakage, then sealing performance is improved, but wire wear increases and rotor contact risk occurs
Solution Approach 1:
The invention uses a flexible seal shoe with a compliant sealing surface that can deform to maintain contact with the rotor. This flexible approach distributes contact stresses and reduces localized wear compared to rigid brush wires, while the controlled flexibility prevents excessive interference that could lead to rotor contact
Solution Approach 2:
The seal shoe acts as an intermediary element between the stator and rotor, providing a controlled contact interface. This intermediary structure allows for wear accommodation through replaceable sealing surfaces while preventing direct rotor-stator contact, thus extending seal life while maintaining sealing performance
3Reliability
If hardcoated knife edges are used to reduce rub debris, then sealing durability is improved, but low cycle fatigue life and rub induced cracking occur
Solution Approach 1:
The invention employs a seal shoe with a replaceable sealing surface that can be designed as a consumable component. Instead of attempting to make the entire seal structure durable through hard coatings, the sealing surface is designed to be replaceable when worn, while the main structural components remain durable. This approach prioritizes overall system reliability over component-level durability
Solution Approach 2:
The seal structure is segmented into a durable support structure and a separate sealing surface. This segmentation allows the sealing surface to be optimized for low wear and replaced independently, while the support structure maintains structural integrity and fatigue resistance, resolving the contradiction between sealing durability and component strength
4Reliability
If labyrinth seal clearances are minimized to improve sealing, then leakage is reduced, but heat generation from rub increases
Solution Approach 1:
The movable seal shoe allows for dynamic adjustment of the sealing clearance, enabling the system to maintain optimal clearance under different operating conditions. This dynamic capability reduces the need for extremely tight clearances, thereby reducing frictional heat generation while maintaining sealing effectiveness
Solution Approach 2:
The seal shoe serves as an intermediary that controls the interaction between the seal and rotor. By providing a controlled contact interface with appropriate clearance, it reduces direct rubbing and associated heat generation while maintaining effective sealing through the compliant sealing surface
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 hybrid seal reduces leakage, minimizes heat generation, and improves durability by maintaining effective sealing across a range of operating conditions, including reverse rotation, while reducing the number of parts required and eliminating the need for precise radial clearance maintenance.
Implementation Method 1
The spring element(s) deflect and move with the shoe(s) in response to the application of fluid pressure to the shoe(s) to create a primary seal
Implementation Method 2
The spring element(s) is flexible in the radial direction
Implementation Method 3
The sealing elements deflect and move with the shoe(s) in response to the application of fluid pressure applied to the shoe(s) to assist in the creation of a secondary seal
Implementation Method 4
The sealing elements oriented side-by-side which contact the at least one shoe to assist in creating a secondary seal
Data Source
Figure 1A~2B
Figure 3~4
Figure 5
AI summary
A hybrid seal for sealing the circumferential gap (11) between a first machine component and a second machine component comprises at least one shoe (16) extending along one of the machine components in a position to create a non-contact seal, at least one spring element (24) connected between one of the machine components and the shoe (16) and a stack of sealing elements (48, 50) located within a slot (22) formed in the shoe (16) wherein a primary seal and secondary seal of the circumferential gap (11) is created by the shoe (16) in cooperation with the spring element (24) and sealing elements (48, 50) respectively.