Dual Hydrostatic Seal Assembly Radial Motion Control
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Solution Overview
Problem
Existing seal assemblies in gas turbine engines, particularly knife-edge seals, suffer from wear and increased leaks due to trench formation in honeycomb structures, and floating non-contact seals exhibit limited sealing effectiveness and propensity for clash due to cantilevered beam deformation of shoe components.
Innovation Solution
A dual-seal ring assembly with hydrostatic seals, where first and second seal rings are attached via pins to ensure synchronized radial motion of shoes, reducing cantilevered deformation and enhancing even sealing engagement by balancing the motion of first and second shoes, thereby maintaining consistent clearance and preventing clashes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a floating non-contact seal with a cantilevered shoe component is used, then radial motion of the shoe is allowed to adjust clearance, but the shoe deforms as a cantilevered beam creating clearance variation that reduces sealing effectiveness
Solution Approach 1:
The shoe component is divided into multiple segments or sections along its length, with each section capable of independent deformation. This segmentation allows the shoe to accommodate radial motion while maintaining uniform clearance across the sealing surface, preventing the cantilevered beam deformation that causes clearance variation.
Solution Approach 2:
The structural parameters of the shoe component are modified by adding support structures or changing the cross-sectional geometry along the length of the shoe. This changes the stiffness distribution to prevent excessive deflection at the free end while still allowing necessary radial motion for clearance adjustment.
2Ease of operation
If the free end of the shoe deflects further than the fixed end, then radial motion is achieved, but the sealing effectiveness is limited and propensity for clash with the rotating component is increased
Solution Approach 1:
A counterbalancing structure or force is introduced to offset the deflection of the free end of the shoe. This could be achieved through a counterweight mechanism or by designing the support structure to provide opposing forces that balance the deflection, ensuring uniform clearance and preventing clashes with the rotating component.
Solution Approach 2:
An intermediary support structure or mechanism is introduced between the fixed end and the free end of the shoe. This intermediary element provides additional support to reduce excessive deflection while still allowing radial motion, acting as a mediator that balances the competing requirements of motion capability and sealing effectiveness.
3Reliability
If a single seal ring with hydrostatic seal is used, then sealing function is provided, but manufacturing complexity increases for advanced processes like laser waterjet cutting
Solution Approach 1:
The seal ring is divided into multiple separate components or segments that can be manufactured independently using advanced processes like laser waterjet cutting. These segments are then assembled to form the complete seal ring, reducing the manufacturing complexity of each individual part while maintaining the overall sealing function.
Solution Approach 2:
Complex features or sections of the seal ring are extracted as separate components that can be manufactured independently. This allows the main body of the seal ring to be manufactured using simpler processes, while the extracted features are produced using advanced manufacturing processes where they are most suitable.
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 dual-seal ring assembly enhances sealing effectiveness by ensuring even radial motion of shoes, reducing clearance variation and the risk of clashes, while also allowing for thinner designs suitable for advanced manufacturing processes like laser waterjet cutting, thus improving durability and manufacturing efficiency.
Implementation Method 1
floating non-contact seal (a.k.a., hydrostatic seal) configurations allow radial motion of shoe components relative to a rotating component. A shoe component of the floating non-contact seal is drawn radially inward and outward (toward and away) from the rotating component in response to the pressure across the sealing element
Implementation Method 2
The shoe is supported on one end by spring-like beams
Data Source
Figure 1
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AI summary
A seal assembly (10) includes first and second rings (16A,16B). The first ring (16A) includes a first outer ring (18A), a first beam (28A) connected to the first outer ring (18A), and a first shoe (22A). The first shoe (22A) includes free and fixed ends (24A,26A) and is configured to move radially. The second seal ring (16B) is disposed axially adjacent and is attached to the first seal ring (16A). The second seal ring (16B) includes a second outer ring (18B), a second beam (28B) connected to the second outer ring (18B), and a second shoe (22B). The second shoe (22B) includes free and fixed ends (24B,26B) and is configured to move in a generally radial direction. The free end (24B) of the second shoe (22B) is disposed axially adjacent to the fixed end (26A) of the first shoe (22A). The fixed end (26B) of the second shoe (22B) is disposed axially adjacent to the free end (24A) of the first shoe (22A).