Rotor Decoupler System for Gas Turbine Windmilling Vibration Control
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Solution Overview
Problem
Conventional load reduction devices in turbofan gas turbine engines provide limited decoupling, leading to undesirable engine and airframe vibrations during windmilling operations due to insufficient reduction of imbalance forces after fan blade damage, and they restrict windmilling speed to avoid resonance.
Innovation Solution
A rotor decoupler system with a load reduction system comprising a fuse and a damper, such as a wire mesh or rope damper assembly, is implemented between bearing systems and support structures to transfer unbalance loads, allowing increased decoupling and load reduction at high speeds, thereby reducing vibrations and enabling windmilling operation without speed restrictions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional load reduction devices provide limited decoupling, then structural strength is maintained, but vibrations during windmilling operations increase
Solution Approach 1:
The decoupler system transitions from a static rigid connection to a dynamic system with multiple degrees of freedom. The radial and axial decouplers with different stiffness characteristics allow the system to adapt its load path based on operating conditions, enabling effective vibration isolation during windmilling while maintaining structural integrity during normal operation
Solution Approach 2:
The decoupler system combines elements with different mechanical properties - radial decoupler elements with lower stiffness and axial decoupler elements with higher stiffness - to create a composite load path structure that selectively transmits or isolates vibrations based on the direction and type of load
2Object-generated harmful factors
If increased decoupling is implemented, then vibrations are reduced, but windmilling speed must be restricted to avoid resonance
Solution Approach 1:
The system uses dynamic decoupling with tuned stiffness characteristics to shift the natural frequency of the fan assembly away from the windmilling speed range. The radial and axial decouplers are designed with specific stiffness ratios that dynamically adjust the system's vibrational characteristics, allowing higher windmilling speeds without resonant amplification
Solution Approach 2:
The decoupler system changes the stiffness parameters of the support structure by introducing frangible elements with controlled mechanical properties. By adjusting the stiffness of radial versus axial decoupler elements, the system modifies the natural frequency and mode shapes of the fan assembly to avoid resonance with windmilling speeds
3Force
If full decoupling is implemented, then load reduction is maximized, but residual stiffness becomes insufficient for stable operation
Solution Approach 1:
The decoupler system segments the load path into radial and axial components with different decoupling characteristics. This segmentation allows independent optimization of each direction - maximum radial decoupling for load reduction while maintaining axial stiffness for operational stability, preventing complete decoupling that would compromise stability
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 system effectively reduces in-flight engine vibrations by damping peak responses and maintaining stable operation during windmilling, allowing for higher windmilling speeds without resonance issues, thus enhancing the structural integrity and operational stability of the engine.
Implementation Method 1
a damper disposed between the outer race and the bearing support such that the damper transfers at least a part of the radial load from the rotor to the bearing support when at least one fuse fails
Data Source
AI summary
A rotor decoupler system for a gas turbine engine is disclosed, comprising a load reduction system disposed between a bearing system and the bearing support. The load reduction system comprises a fuse and a damper such that the damper transfers at least a part of the radial load from the rotor to the bearing support when a fuse fails. In one exemplary embodiment the damper comprises a wire mesh, disposed around the outer race of the bearing. In another exemplary embodiment the damper comprises a rope damper assembly. In yet another exemplary embodiment, a load reduction system is disposed between a support structure and a frame, comprising an extensional fuse and a damper disposed between the support structure and the frame such that the damper transfers at least a part of the unbalance load to the frame when an extensional fuse fails.