Circumferential Seal Stepped Grooves for Low-Pressure Leakage Control
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Solution Overview
Problem
Existing circumferential seal designs in gas turbine engines face challenges in maintaining effective sealing between compartments with low pressure differential and translational effects, leading to potential leakage and contamination, which can cause degradation and failure of the seal.
Innovation Solution
A circumferential seal assembly featuring annular seal rings and groove structures on a rotatable runner with intersecting grooves and steps that redirect fluid flows to form a thin-film layer, enhancing the stiffness and effectiveness of the seal by converging lateral and radial flows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional circumferential seal designs are used, then the seal structure is simple, but the sealing effectiveness deteriorates under low pressure differential conditions
Solution Approach 1:
The seal groove is divided into multiple segments including a feed groove, first groove, second groove, and third groove. Each groove has specific functions: the feed groove receives fluid, the first groove forms a thin film layer, the second groove redirects flow radially outward, and the third groove directs flow laterally. This segmentation allows the seal to effectively prevent fluid migration even under low pressure differential conditions.
Solution Approach 2:
The invention introduces multi-directional flow redirection by creating grooves that direct fluid flow in different dimensions: axial direction (feed groove), radial direction (second groove), and lateral direction (third groove). This multi-dimensional flow control enhances sealing effectiveness by preventing fluid migration through the seal interface in all possible directions.
2Reliability
If conventional seal designs are used, then the manufacturing is simple, but the seal performance deteriorates when the runner translates axially
Solution Approach 1:
The seal groove structure is designed to be dynamically adaptive to axial translation of the runner. The grooves are positioned and oriented such that they maintain their sealing function regardless of the runner's axial position. The feed groove, first groove, second groove, and third groove work together to redirect fluid flow in a manner that remains effective even when the runner moves axially within its operational range.
3Reliability
If conventional seal designs are used, then the structure is simple, but fluid leakage increases between compartments
Solution Approach 1:
The seal groove is divided into multiple segments including a feed groove, first groove, second groove, and third groove. Each groove has specific functions: the feed groove receives fluid, the first groove forms a thin film layer, the second groove redirects flow radially outward, and the third groove directs flow laterally. This segmentation allows the seal to effectively prevent fluid migration even under low pressure differential conditions.
Solution Approach 2:
The invention introduces multi-directional flow redirection by creating grooves that direct fluid flow in different dimensions: axial direction (feed groove), radial direction (second groove), and lateral direction (third groove). This multi-dimensional flow control enhances sealing effectiveness by preventing fluid migration through the seal interface in all possible directions.
4Duration of action of moving object
If conventional seal designs are used, then the design is simple, but wear increases leading to seal failure
Solution Approach 1:
The seal groove structure is designed to preliminarily redirect fluid flow away from the seal interface before wear can occur. The feed groove receives fluid, the first groove forms a protective thin film layer, the second groove redirects flow radially outward, and the third groove directs flow laterally. This preliminary flow redirection prevents fluid from reaching and wearing the seal interface, thereby extending seal operational life.
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, and maintains sealing integrity even under translational effects, thereby extending the seal's operational life and preventing contamination.
Implementation Method 1
A plurality of groove structures are disposed along an outer annular surface of the rotatable runner. Each groove structure includes at least two grooves intersecting a feed groove. The groove structure separates a source flow communicated into the feed groove so that a portion of the source flow enters each groove to form a longitudinal flow therein.
Implementation Method 2
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.
Data Source
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AI summary
A circumferential seal assembly (1 or 21) capable of dividing a gas into separate flow paths before communication between a rotatable runner (15, 35, or 67) and a pair of seal rings (3, 4 or 23, 24) is presented. The assembly (1 or 21) includes an annular seal housing (2 or 22), a rotatable runner (15, 35, or 67), a pair of annular seal rings (3, 4 or 23, 24), and a plurality of groove structures (66). Each groove structure (66) separates a source flow (83) communicated into a feed groove (70) so that a portion enters at least two grooves (69) to form a longitudinal flow (80) therein. Each groove (69) includes at least two adjoining steps (71) defined by base walls (72). The base walls (72) are arranged along the groove (69) to decrease depthwise opposite to rotation of the rotatable runner (15, 35, or 67). Two adjoining base walls (72) are disposed about a base shoulder (73). Each base shoulder (73) locally redirects the longitudinal flow (80) to form an outward radial flow (78) in the direction of one annular seal ring (3, 4 or 23, 24). The base walls (72) are bounded by and intersect a pair of side walls (74). Each side wall (74) includes at least one side shoulder (75) which narrows the groove (69) widthwise and locally redirects the longitudinal flow (80) away from the side wall (74) to form a lateral flow (79) in the direction of the other side wall (74). Each reduction to the volume of the gas at the downstream end of each groove structure (66) increases pressure and enhances the stiffness of a thin-film layer (20) between each annular seal ring (3, 4 or 23, 24) and the rotatable runner (15, 35, or 67).