Slip-Based Radial Bearing Support for Fan Blade-Off Load Relief
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Solution Overview
Problem
Existing bearing support designs in gas turbine engines face challenges in managing load and vibrations during a fan blade off event, particularly in breaking bearings to limit these effects without compromising low-cycle fatigue performance and stress requirements.
Innovation Solution
A bearing arrangement with a first and second bearing supported by respective supports, featuring radial spokes and destabilizers that initiate sliding upon exceeding a threshold, allowing controlled failure to manage loads and vibrations, rather than relying on fracture-based failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bolts are configured to always break at FBO requiring high stress, then bearing support function is achieved, but low-cycle fatigue life and stress requirements cannot be met
Solution Approach 1:
The bearing support transitions from a static bolted connection to a dynamic system where radial spokes can slide along the shaft. This dynamic behavior allows the support to provide high stress resistance during normal operation while enabling controlled sliding during FBO events, resolving the contradiction between maintaining structural integrity and allowing failure modes.
Solution Approach 2:
The friction coefficient between the radial spokes and shaft is carefully controlled to be within a specific range (0.05-0.20). This parameter change enables the system to maintain high load-bearing capacity during normal operation while allowing spokes to slide at controlled rates during FBO events, achieving both reliability and fatigue life requirements.
2Object-affected harmful factors
If radial spokes are designed to slide freely, then load and vibration transfer is limited, but support stiffness is reduced
Solution Approach 1:
The radial spokes transition from a fixed position to a dynamic sliding mechanism. During normal operation, friction maintains the spokes in position providing full stiffness. During FBO events, controlled sliding reduces load and vibration transfer while maintaining sufficient support stiffness through the friction force.
Solution Approach 2:
Friction acts as an intermediary mechanism between the radial spokes and shaft. This frictional force serves as a mediator that provides full support stiffness during normal operation while enabling controlled sliding during FBO events, thus resolving the contradiction between stiffness and harmful factor reduction.
3Reliability
If destabilizers contact radial spokes at high position, then sliding initiation is effective, but axial direction control is reduced
Solution Approach 1:
The destabilizer mechanism operates in the axial dimension to initiate sliding in the radial direction. By positioning destabilizers at different axial heights, the system controls which radial spokes engage first during FBO events, enabling sequential engagement and improved axial direction control while maintaining effective sliding initiation.
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 limits load and vibration transfer by controlled sliding of radial spokes, improving low-cycle fatigue performance and reducing stress on the engine and aircraft structure.
Implementation Method 1
Each spoke extends from a spoke base to a spoke tip. A raised pedestal is positioned at a contact point of each spoke tip... at least one destabilizer is secured to the second bearing and is configured to contact at least one radial spoke of the plurality of radial spokes when the predetermined threshold is exceeded to initiate sliding of the plurality of radial spokes from their respective raised pedestal
Data Source
AI summary
A bearing arrangement of a gas turbine engine includes a first bearing and a second bearing axially offset from the first bearing. A first bearing support extends from a bearing housing to the first bearing to support the first bearing, and a second bearing support extends from the bearing housing to the second bearing to support the second bearing. One or more radial bearing supports including a plurality of radial spokes extend between the bearing housing and the second bearing. Each spoke extends from a spoke base to a spoke tip. A raised pedestal is positioned at a contact point of each spoke tip, and at least one destabilizer is secured to the second bearing and is configured to contact at least one radial spoke when the predetermined threshold is exceeded to initiate sliding of the plurality of radial spokes from their respective raised pedestal.