Ceramic Seal Runner Mounting Assembly for Edge Load Relief
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Solution Overview
Problem
Existing ceramic runner mounts in gas turbine engines experience excessive edge loading and stress due to clip-type designs, leading to wear and reduced sealing efficiency, as they require a portion of the radially outer surface for mounting instead of sealing.
Innovation Solution
A mounting assembly comprising an annular base member with flexible members extending radially outward and an annular sleeve member, which supports a ceramic seal runner in axial and radial alignment with a rotatable shaft, reducing edge loading by accommodating thermal expansion and distributing stress tangentially, thereby maintaining effective sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a clip-type runner mount contacts both radially inner and radially outer surfaces of the runner, then the runner is securely held in place, but excessive edge loading and stress occur at the runner/runner mount interface
Solution Approach 1:
The invention extracts the mounting function from the radially outer surface of the runner, using only the radially inner surface for mounting purposes. The runner mount includes a mounting assembly with a radially inner member that contacts the radially inner surface, while the radially outer surface is freed for sealing engagement with the seal ring, eliminating edge loading stress at the outer interface
Solution Approach 2:
The invention introduces an intermediary mounting assembly structure consisting of a radially inner member, radially outer member, and spokes that mediate between the shaft and the runner. This intermediary structure distributes loads through the spokes rather than concentrating them at the runner interface, reducing edge loading stress while maintaining securement
2Strength
If a portion of the radially outer surface of the runner is dedicated to mounting, then the runner can be securely attached, but the sealing area is reduced
Solution Approach 1:
The invention extracts the mounting function from the radially outer surface, allowing the entire outer surface to be dedicated to sealing engagement with the seal ring. The mounting is achieved through the radially inner surface and the intermediary mounting assembly, freeing the outer surface for maximum sealing area
Solution Approach 2:
The invention segments the mounting function into separate components (radially inner member, radially outer member, spokes) that do not interfere with the sealing surface. This segmentation allows the sealing surface to be fully utilized while mounting is achieved through the segmented mounting assembly structure
3Manufacturing precision
If rigid mounting structures are used to hold the runner, then precise alignment is achieved, but thermal expansion stress is not accommodated
Solution Approach 1:
The invention introduces dynamic flexibility into the mounting structure through the spokes connecting the radially inner member and radially outer member. The spokes can flex and deform to accommodate differential thermal expansion between the ceramic runner and metal shaft, while the overall mounting assembly maintains precise alignment through its structured design
Solution Approach 2:
The invention allows parameter changes in the mounting assembly structure, particularly in the spoke geometry and material properties, to accommodate thermal expansion. The structure can change its physical parameters (flexibility, deformation) in response to temperature changes while maintaining functional alignment
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 reduces stress and wear on the ceramic runner and seal assembly, enhances sealing efficiency, and frees up the radially outer surface for increased sealing area, while accommodating differential thermal expansion between the ceramic runner and metal shaft.
Implementation Method 1
accommodating differential thermal expansion between the ceramic runner and metal shaft
Implementation Method 2
flexible members extending radially outward... distributing stress tangentially
Data Source
AI summary
A seal assembly is disclosed for sealing a higher pressure fluid cavity from a lower pressure fluid cavity. The seal assembly comprises a ceramic seal runner and a mounting assembly. The ceramic seal runner extends around an axial portion of a shaft. The mounting assembly is affixed to and carries the seal runner in axial and radial alignment with the shaft. The mounting assembly comprises an annular base member, a plurality of flexible members, and an annular sleeve member. The plurality of flexible members are circumferentially spaced about the base member and each extend radially outward from one end affixed to the base member in a direction opposite the direction of rotation of the shaft to a distal end. The annular sleeve member is positioned to engage the distal ends of the flexible members and a radially inner surface of the seal runner.