Aspirating Face Seal Tooth Layout for Leakage and Tilt Control
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Solution Overview
Problem
Aspirating face seals in gas turbine engines face challenges with fluid leakage, which increases fuel consumption, affects engine efficiency, and causes component damage, due to transient variations and deteriorating seal assemblies, and existing designs struggle with controlling deflections and tilt moments caused by rotor and stator eccentricity.
Innovation Solution
A turbomachine aspirating face seal assembly with annular labyrinth seal teeth, a pull-off biasing mechanism using coil springs, and a deflector seal tooth to direct airflow through vent passages, enhancing sealing engagement and reducing leakage by maintaining a stable force balance and ventilation across varying engine conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If aspirating face seals are used to minimize fluid leakage, then fuel consumption and engine efficiency are improved, but the seals deteriorate over time due to transient variations and operating environment
Solution Approach 1:
The seal assembly incorporates a compliant seal element that can dynamically adapt its position and shape in response to transient variations in gap dimensions and operating conditions. This dynamic compliance allows the seal to maintain effective sealing contact despite changes in rotor-stator spacing, thereby preventing deterioration and extending service life while continuing to minimize fluid leakage and fuel consumption.
Solution Approach 2:
The seal design utilizes changes in material properties or geometric parameters under operating conditions to optimize performance. For example, the seal element may exhibit elastic deformation or phase changes that allow it to accommodate transient variations in the sealing gap, maintaining sealing effectiveness across different operating states without premature deterioration.
2Loss of energy
If seal assemblies are positioned between rotor and stator to control fluid leakage, then engine efficiency is improved, but tilt moments are generated due to rotor and stator eccentricity
Solution Approach 1:
The seal assembly incorporates counterbalancing features or symmetric design elements that generate opposing forces to counteract the tilt moments produced by rotor-stator eccentricity. This may include dual seal elements positioned to create balanced force distributions, or mechanical counterweights that offset the asymmetric loading, thereby reducing net tilt moments while maintaining effective sealing to prevent energy loss.
Solution Approach 2:
The seal design intentionally introduces asymmetric features that compensate for the asymmetric loading conditions caused by eccentricity. By positioning seal elements or structural features asymmetrically, the design creates force distributions that balance the tilt moments, allowing the seal to maintain effective sealing performance without generating excessive tilting forces on the rotor-stator assembly.
3Loss of energy
If primary seal tooth is mounted on stator to form air curtain, then leakage is reduced, but venting effectiveness is reduced and assembly is difficult
Solution Approach 1:
The seal system is divided into modular components, with the primary seal tooth, secondary seal elements, and vent passages configured as separate, pre-fabricated modules that can be independently manufactured and then assembled. This segmentation allows each component to be optimized for its specific function while simplifying the overall assembly process, reducing manufacturing complexity, and enabling easier maintenance and replacement without compromising the air curtain sealing effectiveness.
4Loss of energy
If aspirating face seal restricts fluid flow from high pressure to low pressure, then leakage is minimized, but ventilation may be insufficient under certain operating conditions
Solution Approach 1:
The seal design incorporates multiple sealing elements and redundant vent passages arranged to provide continuous sealing and ventilation functionality across the full range of operating conditions. As one seal element or passage becomes less effective under certain conditions, others remain active to maintain both leakage restriction and adequate ventilation, ensuring continuous useful action without compromising either sealing or breathing requirements.
Solution Approach 2:
The vent passages and seal elements are designed to dynamically adjust their effective flow areas in response to operating conditions such as pressure differential, rotational speed, and temperature. This dynamic behavior allows the seal to automatically balance leakage restriction with ventilation requirements, opening vent passages when pressure builds up and maintaining sealing when pressure differential is favorable, thereby providing both functions simultaneously under varying conditions.
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 effectively restricts high-pressure air leakage to low-pressure regions, minimizes tilt moments, and maintains effective ventilation, thereby improving engine efficiency and reducing maintenance costs by enhancing the sealing performance and stability of the aspirating face seal.
Implementation Method 1
a pull-off biasing means (82) having a plurality of circumferentially spaced apart coil springs (84)
Implementation Method 2
Radially inner and outer tooth rings axially extend away from a first one of the rotatable and non-rotatable gas bearing face surfaces
Implementation Method 3
the air jet from the primary tooth forms an air curtain and reduces the venting effectiveness
Data Source
AI summary
An aspirating face seal between high and low pressure regions of a turbomachine at a juncture between rotatable and non-rotatable members of turbomachine includes gas bearing rotatable and non-rotatable face surfaces. A starter seal tooth and optional deflector seal tooth are mounted on a seal teeth carrier on the rotatable member. The primary seal tooth and non-rotatable face surface are mounted on an annular slider on the non-rotatable member. A pull-off biasing means urges the annular slider away from the rotatable member and the non-rotatable face surface away from the rotatable surface. A secondary seal is in sealing engagement with the annular slider in the low-pressure region and the pull-off biasing means is located radially outwardly of the annular slider in the high pressure region.