Face Seal Feed-Slot Geometry for Lower Closing Force
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Solution Overview
Problem
High contact pressure and net closing force in face seal arrangements of gas turbine engines lead to increased heat generation, friction losses, and reduced service life due to high heat generation and additional engine system friction.
Innovation Solution
A face seal arrangement with a non-rotating sealing ring biased by a coil spring, featuring a contact portion and a feed portion with circumferentially spaced feed slots connected to annular grooves, which reduces contact pressure and net closing force by utilizing high-pressure air to counteract the bias force, thereby optimizing the sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spring force and pressurized air bias the face seal into the seal seat, then the sealing contact is maintained, but the contact pressure and net closing force become relatively high resulting in high heat generation and friction losses
Solution Approach 1:
The sealing face is divided into two distinct portions: a contact portion that contacts the seal seat and a feed portion that is recessed from the seal seat. This segmentation allows the contact portion to maintain sealing while the feed portion receives high-pressure air to reduce the net closing force, thereby reducing friction losses without compromising sealing reliability.
Solution Approach 2:
High-pressure air is introduced into the feed portion through feed slots and annular grooves. This pneumatic pressure counteracts the spring force and reduces the net closing force on the sealing face, thereby reducing contact pressure and friction losses while maintaining adequate sealing contact through the contact portion.
2Reliability
If high contact pressure is applied to maintain sealing, then the seal effectiveness is improved, but heat generation increases and service life is reduced
Solution Approach 1:
By segmenting the sealing face into contact and feed portions, the patent concentrates the sealing function in the contact portion while using the recessed feed portion to house high-pressure air. This reduces the overall contact pressure and heat generation while maintaining seal effectiveness through the dedicated contact portion.
Solution Approach 2:
High-pressure air supplied to the feed portion creates a counter-pressure that reduces the contact pressure between the sealing face and seal seat. This pneumatic counteraction lowers heat generation and component temperatures while maintaining adequate sealing effectiveness through the contact portion.
3Force
If the feed portion is recessed from the seal seat, then the net closing force is reduced, but the sealing geometry becomes more complex
Solution Approach 1:
The sealing face is segmented into a contact portion at the seal seat level and a recessed feed portion. This segmentation allows the feed portion to be recessed for receiving high-pressure air while the contact portion maintains proper sealing geometry, balancing force reduction with geometric simplicity.
Solution Approach 2:
The feed portion is recessed axially from the seal seat, introducing a dimensional variation that allows high-pressure air to be supplied without increasing radial or circumferential complexity. This axial recess provides the necessary volume for pneumatic pressure while maintaining a relatively simple overall sealing geometry.
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 reduces contact pressure and net closing force, enhancing the service life of face seal arrangements and minimizing engine friction losses and heat generation, while maintaining an appropriate seal.
Implementation Method 1
A coil spring biases the seal housing towards the seal seat
Implementation Method 2
The seal housing is exposed to high pressure air outward of the bearing compartment
Data Source
AI summary
A bearing is mounted to a static structure outwardly of the shaft, and supporting the shaft. A bearing compartment is defined by face seal arrangements on each of two axial sides of a bearing. Each face seal arrangement includes a seal seat rotating with the shaft and a non-rotating sealing ring. The seal housing is 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 is biased into contact with the seal seat by a bias force including a net fluid force acting on the seal housing and the coil spring. The sealing face is defined by a contact portion contacting the seal seat and a feed portion recessed from the seal seat. The feed portion includes a plurality of circumferentially spaced feed slots fluidly connected to at least one annular groove.