Aspirating Face Seal Leakage Control via Pull-Off Biasing
Solution Overview
Problem
Fluid leakage through gas turbine engine seal assemblies increases fuel consumption, affects engine efficiency, and causes damage to components, with existing seal designs deteriorating over time and being ineffective in controlling deflections and contamination.
Innovation Solution
A turbomachine aspirating face seal assembly with primary, starter, and deflector seal teeth mounted on a rotatable member, featuring a pull-off biasing means using coil springs and an annular slider to restrict high-pressure air leakage to a low-pressure region, and a drain assembly to prevent oil ingestion, while maintaining effective air pressure balance and reducing fouling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional seal assemblies are used, then fluid leakage is reduced to some extent, but the seals deteriorate over time and become ineffective in controlling deflections and contamination
Solution Approach 1:
The seal assembly is divided into multiple functional segments: primary seal teeth for leakage restriction, deflector seal teeth for contamination control, and a drain assembly for oil removal. Each segment performs a specific function, allowing the system to maintain reliability while adapting to multiple threats simultaneously
Solution Approach 2:
The deflector seal teeth act as an intermediary element between the primary seal and the contamination source. They deflect contaminants away from the primary seal interface, protecting it from fouling while maintaining the seal's primary leakage restriction function
2Loss of energy
If seal assemblies are positioned in the engine environment, then fluid leakage is controlled, but the seals are exposed to contamination and deteriorate
Solution Approach 1:
The drain assembly converts the harmful effect of oil contamination into a beneficial drainage function. By providing a dedicated drainage path, the system allows oil to be actively removed rather than passively accumulating, transforming the contamination threat into a controlled drainage process that protects the seal
3Reliability
If existing seal designs are used, then some fluid leakage control is achieved, but they are ineffective in preventing oil fouling
Solution Approach 1:
The drain assembly extracts oil from the seal environment by providing a dedicated drainage path. This separates the oil removal function from the sealing function, allowing the primary seal to focus on leakage restriction while the drain assembly handles oil extraction, preventing fouling without compromising seal effectiveness
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 fluid leakage, maintains engine efficiency, prevents oil fouling, and reduces maintenance costs by enhancing force balance and preventing contamination, thereby improving the durability and performance of gas turbine engines.
Implementation Method 1
a pull-off biasing means using coil springs and an annular slider to restrict high-pressure air leakage
Implementation Method 2
Aspirating face seals control fluid leakage in the engine by restricting fluid flow from areas of higher pressure to areas of lower pressure
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. Primary and starter seal teeth and optional deflector seal tooth are mounted on seal teeth carrier on rotatable member. Non-rotatable face surface is 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. Biasing means may include coil springs within spring chambers of circumferentially spaced cartridges. Tongues extend inwardly from spring chambers into grooves in slider.