Bearing Compartment Centering Spring for Compact Axial Packaging
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Solution Overview
Problem
Existing centering springs in gas turbine engines face challenges in achieving desired packaging, deflection, and structural criteria due to limited axial space, which restricts the overall length and stiffness, leading to stress and reduced fatigue life.
Innovation Solution
The design incorporates first and second rings interconnected by axially extending circumferentially spaced beams with apertures between them, featuring lugs with a support surface that engages the engine static structure, allowing for a shorter overall length while enabling longer beams for increased stiffness and reduced stress, and includes a radially extending flange and sealing surfaces for secure mounting and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the overall length of the centering spring is reduced for better packaging, then the axial space is reduced, but the beam length is reduced leading to decreased stiffness and increased stress
Solution Approach 1:
The patent moves the mounting interface from the end face of the first ring to its outer cylindrical surface. This dimensional shift allows the beams to extend further radially outward, effectively increasing beam length and stiffness without increasing axial length. The lugs projecting from the first ring's outer surface provide a new interface plane that resolves the contradiction between compact axial footprint and sufficient beam stiffness.
Solution Approach 2:
The lugs are pre-positioned on the outer surface of the first ring at strategic locations between the beams. This preliminary placement creates apertures that receive the free ends of the beams, effectively pre-configuring the stress distribution path. By establishing this interface in advance, the design ensures optimal stress transfer from beams to engine static structure without requiring additional axial space.
2Strength
If the beam length is increased for higher stiffness, then the stress on beams is reduced, but the overall length of the centering spring increases reducing packaging efficiency
Solution Approach 1:
Instead of extending beam length in the axial direction, the patent enables the beams to utilize radial space by mounting the first ring interface on its outer cylindrical surface. The lugs project radially outward to receive beam ends, allowing effective beam length to increase while keeping axial length compact. This dimensional reconfiguration directly resolves the contradiction between beam stiffness and overall package size.
3Volume of moving object
If the centering spring is designed for compact packaging, then the axial space is minimized, but the fatigue life is reduced due to increased stress on shorter beams
Solution Approach 1:
The lugs are pre-positioned on the first ring to create apertures that receive the beam ends. This preliminary configuration establishes an optimized stress distribution path from the beginning, ensuring that loads are effectively transferred to the engine static structure through the lugs. By pre-configuring this interface, the design maintains lower stress levels on beams despite compact axial dimensions, thereby preserving fatigue life.
Solution Approach 2:
Mounting the interface on the outer surface of the first ring rather than its end face allows beams to achieve greater effective length within the same axial space. This dimensional change enables the beams to be longer and experience lower bending stresses, directly improving fatigue life without compromising the compact axial packaging.
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
This configuration allows for a more compact centering spring with enhanced stiffness and fatigue life, reducing stress on the beams and enabling better packaging within limited axial space, thereby improving the structural integrity and operational life of the bearing compartment.
Implementation Method 1
The first ring is mounted to the engine static structure via a tight, interference fit to the engine static structure
Implementation Method 2
Load from the bearing is passed through the beams, which are the flexible portion of the centering spring, to the first ring
Implementation Method 3
The second ring includes a sealing surface having at least one groove. A seal is provided in the groove. The seal engages the engine static structure.
Data Source
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AI summary
A bearing compartment (66, 166) for a gas turbine engine (20) includes an engine static structure (36, 136). A rotating structure (45, 145) is configured to rotate about an axis (A) relative to the engine static structure (36, 136). A bearing (72, 172) supports the rotating structure (45, 145). A centering spring (70, 170) has first and second rings (82, 182, 84, 184) interconnected by axially extending circumferentially spaced beams (86, 186). An aperture (94, 194) is provided between an adjacent pair of the beams (86, 186). The first ring (82, 182) is mounted to the engine static structure (36, 136). The bearing (72, 172) is mounted to the second ring (84, 184). The first ring (82, 182) includes multiple circumferentially spaced lugs (102, 202). Each of the lugs (102, 202) axially extend into a corresponding one of the apertures (94, 194). The lugs (102, 202) include a support surface (104, 204) that engages the engine static structure (36, 136).