Gas Turbine Fan Mounting System with Frangible Link
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Solution Overview
Problem
Aircraft gas turbine engines face challenges in maintaining balance and reducing loads on shafts and bearings when fan blades detach, requiring an improved fan mounting system that allows the fan to continue rotating while minimizing damage from out-of-balance conditions.
Innovation Solution
A gas turbine engine with a support arrangement featuring a first and second load path, where a frangible link breaks under predetermined radial loads, allowing the fan shaft to be supported by a single bearing, reducing loads on the mechanical ground and incorporating damping material to absorb vibrational energy from orbiting motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frangible connection breaks in the event of an out of balance condition, then the fan is supported by a single bearing and can continue to rotate, but the load on the mechanical ground increases
Solution Approach 1:
The support arrangement is segmented into two separate load paths (first and second support members) instead of a single rigid support. This segmentation allows the system to distribute loads differently during normal operation versus blade-off conditions, enabling the fan to continue rotating while controlling the load on the mechanical ground through the flexible connection of the first support member.
Solution Approach 2:
The first support member changes its effective stiffness parameter dynamically - acting as a flexible connection during blade-off conditions to allow orbital motion and reduce mechanical ground load, while providing rigid support during normal operation. This parameter change enables the system to adapt to different operational states.
2Reliability
If the fan is supported by a single bearing after blade detachment, then the fan can continue to rotate, but large loads are imposed on the shafts and bearings
Solution Approach 1:
The first support member is designed with inherent flexibility beforehand to cushion and absorb the shock loads that occur during blade-off conditions. This pre-designed flexibility allows the fan to transition into orbital motion without imposing excessive peak loads on the bearing and shaft, protecting these components from damage while maintaining rotation continuity.
3Strength
If a rigid support structure is used to support the fan shaft, then the bearing is well-supported, but the fan cannot accommodate orbiting motion in the event of blade-off
Solution Approach 1:
The support arrangement transitions from a static rigid structure to a dynamic system where the first support member can flex and deform. This dynamic capability allows the bearing to move relative to the mechanical ground, accommodating the orbiting motion of the fan during blade-off conditions while still providing necessary support strength during normal operation.
4Object-affected harmful factors
If vibration damping is added to reduce vibrational energy from orbiting motion, then damage to the engine is reduced, but the device complexity increases
Solution Approach 1:
The damping function is merged with the existing first support member structure rather than adding a separate damping system. The support member's flexible connection inherently provides vibration damping by absorbing and dissipating vibrational energy through its deformation, thus reducing engine damage without significantly increasing device complexity.
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 enables the fan shaft to remain supported and absorb vibrational energy, reducing damage to the engine and allowing controlled orbiting motion, while also decoupling the fan shaft from the gearbox to reduce torsional loads and facilitate shutdown, thus minimizing structural loads and potential damage.
Implementation Method 1
The gas turbine engine may comprise a damping material configured to damp bending movement of the first support member. Advantageously, vibrational energy from orbiting motion of the fan following a fan blade-off event can be absorbed, thereby reducing damage to the engine.
Data Source
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AI summary
A gas turbine engine (10) comprises a fan (13), a fan shaft (32) configured to rotationally support the fan (13), a first bearing (34) configured to rotationally support the fan shaft (32) and a support arrangement configured to support the first bearing (34). The support arrangement comprises a first support member (38) coupled to the first bearing (34) and to a mechanical ground (40) to define a first load path, and a second support member (44) coupled to the mechanical ground (40) and the first bearing (34) to define a second load path. The second support member (44) is coupled to one of the first bearing (34) and the mechanical ground (40) by a first frangible link (46). In normal use, a load extends between the bearing (34) and the mechanical ground (40) through the first and second loads paths, and in the event of a predetermined radial load being applied to the first bearing (34), the frangible link (46) breaks such that the load extends between the first bearing (34) and the mechanical ground (40) through the first load path, but not the second load path.