Flexible Support Structure for Geared Gas Turbine Engine Gear Alignment
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Solution Overview
Problem
In gas turbine engines, backbone bending due to aero and maneuver loads causes transverse deflection, leading to misalignment of gear train elements, which results in efficiency losses and reduced component life due to increased stresses from misalignment and concentrated loads.
Innovation Solution
A flexible support structure is implemented, providing transverse and lateral stiffness that is significantly lower than the main support structure, allowing for the segregation of vibrations and transverse deflections, and is mounted to a static structure to accommodate misalignment and reduce stress on gear components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid support structure is used for the gear system, then structural strength and stability are improved, but misalignment and stress concentration occur due to backbone bending deflection
Solution Approach 1:
The support structure transitions from a rigid static configuration to a dynamic flexible configuration that can adapt to backbone bending deflections. The flexible support allows the gear system to maintain proper alignment despite engine case deflection during flight maneuvers, resolving the contradiction between structural strength and alignment reliability.
Solution Approach 2:
The stiffness parameter of the support structure is changed from high (rigid) to low (flexible). This parameter change enables the support to accommodate transverse deflections and maintain gear alignment, solving the contradiction between needing structural strength and maintaining alignment reliability under load.
2Stability of the object's composition
If the support structure stiffness is high, then structural stability is improved, but gear tooth stress and misalignment increase due to backbone bending
Solution Approach 1:
The support structure is made dynamically flexible rather than statically rigid, allowing it to absorb backbone bending deflections. This dynamic flexibility reduces gear tooth stress while maintaining overall structural stability during flight maneuvers.
Solution Approach 2:
The flexible support acts as an intermediary element between the rigid engine case and the gear system. It mediates the transmission of forces, allowing structural stability to be maintained while preventing excessive stress concentration at the gear teeth by accommodating deflections.
3Reliability
If a flexible support with lower stiffness is used, then gear alignment and stress are improved, but structural support capability may be reduced
Solution Approach 1:
The flexible support provides localized flexibility only where needed at the gear system interface, while maintaining adequate overall support capability. This local quality approach allows the support to be flexible enough to accommodate alignment requirements while still providing sufficient structural support.
Solution Approach 2:
The stiffness parameter is optimized to a specific low value that balances alignment reliability and support capability. By changing the stiffness parameter to be lower than the rigid structure but not excessively low, the system achieves both proper gear alignment and adequate structural support.
4Ease of manufacture
If rigid mounting is used for the gear system, then installation simplicity is improved, but efficiency losses occur due to misalignment from backbone bending
Solution Approach 1:
The mounting system is changed from rigid to flexible, allowing automatic adaptation to backbone bending deflections. This dynamic flexibility prevents misalignment-related efficiency losses while the flexible support itself can be integrated into the existing manufacturing process.
Solution Approach 2:
The flexible support acts as an intermediary between the rigid engine case and the gear system, mediating the effects of backbone bending. This intermediary approach maintains installation simplicity while preventing efficiency losses by ensuring proper gear alignment under all operating conditions.
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 flexible support structure reduces design loads by over 17%, increases system reliability, and maintains torque transmission during maneuvers, thereby extending the life of engine components by minimizing gear tooth stress variations and maintaining alignment.
Implementation Method 1
A flexible support at least partially supports the gear system, and defines at least one of a flexible support transverse and a flexible support lateral stiffness with respect to at least one of the support transverse and the support lateral stiffness
Data Source
AI summary
A gas turbine engine includes a fan shaft and a support which supports the fan shaft. The support defines at least one of a support transverse and a support lateral stiffness. A gear system drives the fan shaft. A flexible support at least partially supports the gear system, and defines at least one of a flexible support transverse and a flexible support lateral stiffness with respect to at least one of the support transverse and the support lateral stiffness. An input to the gear system defines at least one of an input transverse and an input lateral stiffness with respect to at least one of the support transverse and the support lateral stiffness. A method of designing a gas turbine engine is also disclosed.