Circumferential Seal Stiffness via Bifurcated Flow Grooves
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Solution Overview
Problem
Existing circumferential seal designs in gas turbine engines face challenges in maintaining an effective seal between compartments due to low pressure differentials and translational effects on the sealing interface, leading to potential contamination and degradation of the seal over the operational range of the engine.
Innovation Solution
A circumferential seal assembly featuring an annular seal housing with rotatable runner and annular seal rings, where groove structures on the runner redirect fluid flows to form thin-film layers between the seal rings and the runner, enhancing the seal's stiffness and preventing fluid migration between compartments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional circumferential seal designs are used, then the seal structure is simple, but the seal fails to prevent fluid migration under low pressure differentials
Solution Approach 1:
The seal ring is segmented into multiple functional zones with different groove patterns. The first groove pattern (e.g., circumferential grooves) is located in one region to capture gas, while the second groove pattern (e.g., radial or spiral grooves) is located in another region to manage lubricant flow. This segmentation allows each zone to perform its specific function optimally, preventing fluid migration under low pressure differentials while maintaining a manageable structure.
Solution Approach 2:
Different regions of the seal ring are given different local properties through varying groove patterns. The upstream region may have grooves optimized for gas capture, while the downstream region has grooves optimized for lubricant drainage. This local differentiation enables the seal to address multiple sealing challenges simultaneously, improving reliability without requiring complete structural redesign.
2Reliability
If the seal is designed for optimal performance at one operating condition, then sealing is effective at that condition, but performance degrades under translational movements
Solution Approach 1:
The seal incorporates dynamic elements such as flexible seal rings or adjustable groove patterns that can adapt to translational movements. The grooves are designed to maintain their sealing function even when the seal experiences axial or radial displacement during operation. This dynamic design allows the seal to maintain effective sealing across a range of operating conditions rather than being optimized for a single static position.
Solution Approach 2:
The seal ring is designed with multi-functional groove patterns that can handle both gas sealing and lubricant management simultaneously, while also accommodating translational movements. The grooves serve multiple purposes: capturing gas, draining lubricant, and maintaining sealing contact during displacement. This universal design approach enables the seal to adapt to various operating conditions including translational movements without sacrificing sealing effectiveness.
3Reliability
If grooves are added to form thin-film layers, then sealing effectiveness improves, but manufacturing complexity increases
Solution Approach 1:
The complex groove patterns are extracted as separate features that can be added to the seal ring through secondary processing methods such as machining, EDM, or laser processing, rather than requiring complex tooling during primary manufacturing. This allows the thin-film layer forming grooves to be incorporated into existing seal manufacturing workflows without fundamentally changing the base manufacturing process, thus limiting the increase in manufacturing complexity.
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 solution minimizes fluid mixing between compartments, reduces wear on the seal assembly, and maintains effective sealing performance across varying operational conditions, including low pressure differentials and translational movements.
Implementation Method 1
bifurcated hydrodynamic flow for use within a gas turbine engine
Implementation Method 2
form a pair of thin-film layers sealing one compartment from another compartment
Data Source
AI summary
A circumferential seal assembly capable of dividing a gas into separate flow paths before communication between a rotatable runner and a pair of seal rings is presented. The assembly includes an annular seal housing, a rotatable runner, a pair of annular seal rings, and a plurality of groove structures. Each groove structure separates a source flow communicated into a feed groove so that a portion enters at least two grooves to form a longitudinal flow therein. Each groove includes at least two adjoining steps defined by base walls. The base walls are arranged along the groove to decrease depthwise opposite to rotation of the rotatable runner. Two adjoining base walls are disposed about a base shoulder. Each base shoulder locally redirects the longitudinal flow to form an outward radial flow in the direction of one annular seal ring. The base walls are bounded by and intersect a pair of side walls. Each side wall includes at least one side shoulder which narrows the groove widthwise and locally redirects the longitudinal flow away from the side wall to form a lateral flow in the direction of the other side wall. Each reduction to the volume of the gas at the downstream end of each groove structure increases pressure and enhances the stiffness of a thin-film layer between each annular seal ring and the rotatable runner.