Canted Knife Edge Seals for Gas Turbine Leakage Reduction
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Solution Overview
Problem
Existing gas turbine engine labyrinth seals with cylindrical sealing surfaces and knife edge seals fail to adequately minimize leakage of combustion products radially inwardly, despite the use of abradable materials and radial spacing, indicating a need for further reduction in fluid leakage.
Innovation Solution
The introduction of canted pockets with angled connecting faces between radially inner and outer sealing surfaces, combined with canted knife edge seals that extend at an angle in the same direction as the connecting faces, creates a more restrictive flow path by generating vortices that enhance leakage resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If cylindrical sealing surfaces with radial spacing are used, then the seal structure is simple and easy to manufacture, but fluid leakage cannot be adequately minimized
Solution Approach 1:
The sealing surface is segmented into multiple distinct pockets (first, second, and third pockets) with different geometries and orientations. Each pocket creates a separate flow restriction zone, dividing the leakage path into multiple segments that collectively reduce overall fluid loss through the seal interface.
Solution Approach 2:
The sealing surfaces transition from symmetric cylindrical geometry to asymmetric canted pockets with varying angles and orientations. The first pocket has a first cant angle, the second pocket has a second cant angle, and the third pocket has a third cant angle, creating asymmetric flow paths that increase resistance to leakage while maintaining manufacturing feasibility.
2Loss of substance
If closely spaced knife edge seals are used, then leakage is reduced, but the risk of contact and wear between rotating and stationary components increases
Solution Approach 1:
Different regions of the sealing interface have locally optimized properties through the use of multiple pockets with different cant angles and geometries. Each pocket is tailored to create specific flow resistance characteristics, allowing the seal to achieve effective leakage prevention without requiring uniform close spacing that would increase wear risk across the entire interface.
Solution Approach 2:
The sealing mechanism transitions from relying solely on radial spacing to utilizing the angular dimension through canted pockets. By introducing cant angles in the axial direction, the seal creates flow restriction through three-dimensional path complexity rather than just reducing radial clearance, thereby maintaining reliability while improving leakage prevention.
3Loss of substance
If multiple radial sealing surfaces are used, then a labyrinth path is created to limit leakage, but some leakage still occurs and further reduction is desired
Solution Approach 1:
The sealing structure incorporates dynamic flow interaction through canted pockets that create vortex formation and flow separation effects. As fluid moves through the canted pockets, the angled surfaces dynamically alter flow direction and create recirculation zones, increasing effective flow resistance without adding more static sealing surfaces.
Solution Approach 2:
The canted pockets utilize fluid dynamic effects including vortex generation, flow separation, and pressure gradient creation to enhance sealing performance. The angled surfaces manipulate the combustion products flow to create hydraulic resistance through three-dimensional flow patterns, achieving superior leakage prevention compared to simple radial labyrinth structures.
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 configuration significantly reduces fluid leakage by presenting a more restrictive path for fluid flow, effectively minimizing radial inward leakage through the creation of vortices and maintaining a close seal between rotating and stationary components.
Implementation Method 1
The combination of the canted knife edge seals and the pockets limits leakage by generating vortices that enhance leakage resistance
Data Source
Figure 1
Figure 2~4
AI summary
A gas turbine engine (10) is provided with turbine sealing structures including knife edge seals (104) which extend at an angle relative to an axial center line (12) of the engine (10). Each knife edge seal (104) is associated with a pocket (114) defined between a radially inner surface and a spaced radially outer surface. The pockets (114) and their associated knife edge seals (104) create a difficult flow path (X) to prevent leakage into radially inner portions of the turbine section (20, 22).