Face Seal Groove Geometry for Lower Axial Closing Force
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Solution Overview
Problem
High axial closing force and heat generation in face seal arrangements of gas turbine engines due to a high balance ratio and spring force, leading to reduced service life and oil coking.
Innovation Solution
A face seal arrangement with a balance ratio between 0.5 and 0.64, where a coil spring biases a sealing ring into contact with a seal seat, and a groove provides a pressure face exposed to high-pressure air, reducing the axial closing force and heat generation by optimizing the sealing ring's dimensions and materials such as titanium alloy or ceramic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high balance ratio and high spring force are used in the face seal arrangement, then the sealing force is improved, but the axial closing force and heat generation increase, leading to reduced service life and oil coking
Solution Approach 1:
The patent changes the balance ratio parameter from a high value (prior art) to a reduced value between 0.5 and 0.64. This parameter change optimizes the distribution of forces on the face seal, reducing the axial closing force and subsequent heat generation while maintaining adequate sealing force through the combined action of spring force and reduced air pressure on the sealing face
Solution Approach 2:
The patent specifies that the seal housing be formed of advanced materials such as titanium alloy or ceramic. These composite or advanced materials have superior thermal properties including higher melting points and better heat resistance, allowing the seal to operate at elevated temperatures without degradation, thus addressing the heat generation issue while maintaining structural integrity
2Reliability
If a high spring force is used to bias the face seal into contact with the seal seat, then the sealing reliability is improved, but the axial closing force increases, causing high heat generation and oil coking
Solution Approach 1:
The patent optimizes the spring force parameter to work in conjunction with the reduced balance ratio (0.5-0.64). By reducing the balance ratio, the air pressure component of the closing force is reduced, allowing the spring force to be optimized at a lower level while still achieving adequate sealing reliability, thereby reducing overall axial closing force and heat generation
Solution Approach 2:
The use of titanium alloy or ceramic for the seal housing provides materials with superior thermal stability and resistance to thermal degradation. These materials can withstand the reduced but still present heat generation without experiencing oil coking or material failure, thus maintaining sealing reliability without requiring excessively high spring forces
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 reduced balance ratio and optimized design lower component temperatures, mitigate oil coke formation, and improve seal reliability by reducing seal wear and axial closing force.
Implementation Method 1
A coil spring biases the seal housing towards the seal seat
Implementation Method 2
Pressurized air acting on a surface of the face seal also provides a bias force
Implementation Method 3
A face seal is biased in the contact with the seal seat
Data Source
AI summary
A face seal arrangement includes a seal seat rotating with the shaft and a non-rotating face seal including a sealing ring. The sealing ring includes a sealing face biased into contact with the seal seat. The sealing ring also has a groove defined remote from the seal face relative to the seal seat. The groove provides a pressure face that will be exposed to high pressure air outward of the bearing compartment. A coil spring biases the seal housing towards the seal seat, such that the sealing face of the sealing ring is biased into contact with seal seat by air pressure against the pressure face, and the coil spring. A balance ratio is defined between an area of the pressure face and an area of the sealing face, the balance ratio is between 0.5 and 0.64.