Asymmetric Annular Centering Spring for Bearing Vibration Damping
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Solution Overview
Problem
Conventional centering and damping assemblies in gas turbine engines face challenges in reducing cyclic fatigue and undesirable vibrations, particularly due to the limitations of traditional squirrel cage designs which can lead to excessive structural loads and damage.
Innovation Solution
The introduction of asymmetric annular springs, formed by adjusting material, thickness, turns per unit area, length, or shape, to create an asymmetrical design that reduces undesirable vibrations and improves damping efficiency, allowing for a more compact and efficient centering and damping assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional squirrel cage centering springs are used, then the bearing assembly is supported and shaft centering is achieved, but cyclic fatigue and undesirable vibrations occur leading to excessive structural loads
Solution Approach 1:
The patent applies asymmetry by configuring the annular spring with non-uniform wire spacing around its circumference. Specifically, the wire spacing varies in at least one radial plane, creating asymmetric regions that generate beneficial vibration counter-forces. This asymmetric configuration directly addresses the harmful cyclic vibrations by introducing controlled asymmetry that produces counteracting vibrational forces, thereby reducing overall vibration amplitudes and preventing the excessive structural loads associated with conventional symmetric squirrel cage designs.
Solution Approach 2:
The patent implements parameter changes by varying the wire spacing parameters of the annular spring. The distance between adjacent wires is intentionally made non-uniform, with different spacing values in different circumferential regions. This parameter variation allows the spring to generate differential forces that counteract harmful vibrations while maintaining the required shaft centering function, thus resolving the contradiction between reliability and harmful vibrational effects.
2Strength
If traditional centering spring designs are used, then structural support is provided, but damage risk increases due to excessive structural loads from vibrations
Solution Approach 1:
The asymmetric wire spacing configuration generates counter-vibrations that reduce the amplitude of harmful oscillations transmitted to the bearing assembly and shaft. By positioning wires at non-uniform intervals, the spring creates differential elastic forces that actively counteract the cyclic loads, thereby protecting the structural components from excessive loads and reducing damage risk while maintaining adequate structural support.
Solution Approach 2:
The patent converts the potentially harmful vibrational forces into beneficial counter-forces by strategically positioning the spring wires asymmetrically. The same elastic properties of the spring material that could amplify vibrations are instead harnessed to generate counter-vibrations through the asymmetric configuration. This transforms the harmful effect of vibrations into a beneficial protective mechanism that reduces overall vibrational amplitudes and structural loads.
3Ease of manufacture
If symmetric annular spring configurations are used, then manufacturing is simplified, but damping efficiency is reduced due to inadequate vibration counter-forces
Solution Approach 1:
The patent deliberately introduces asymmetry into the annular spring configuration to enhance damping efficiency. By varying the wire spacing in at least one radial plane, the spring generates differential forces that create effective vibration counter-forces. While this increases manufacturing complexity compared to uniform spacing, it significantly improves the damping capability by enabling the spring to actively counteract harmful vibrations rather than merely providing passive structural support.
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 asymmetric annular spring design effectively reduces undesirable vibrations, enhances damping fluid scavenging, and provides improved structural retention, leading to reduced damage risk and increased operational efficiency in gas turbine engines.
Implementation Method 1
an asymmetric first radial plane of the first annular spring may reduce undesirable vibrations of the bearing assembly and the shaft due to the asymmetry of the first annular spring in the axial direction and in the circumferential direction
Implementation Method 2
One commonly used viscous damper is the squeeze film damper, which utilizes a small, fluid-filled annular gap between the bearing and a nonrotating housing. Radial motion of the rotating shaft causes relative motion between the bearing and the nonrotating housing, which changes the gap to squeeze a damping fluid within the annulus, dampening the motion of the rotating shaft.
Implementation Method 3
A first spring is between the bearing and the bearing support and configured to resist bearing movement to center a shaft radially inward from the bearing
Data Source
Figure 1
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Figure 2B
AI summary
An assembly (100) for use in a bearing compartment (102) having an axis includes a bearing outer race (124) configured to be located in the bearing compartment (102). The assembly (100) further includes at least one annular spring (112) positioned in the bearing outer race (124) and being asymmetric in at least one of the axial direction or the circumferential direction relative to the axis to reduce the likelihood of amplification of vibration experienced by the at least one annular spring (112).