Fan Assembly Mistuning Band for Flutter Reduction
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Solution Overview
Problem
Gas turbine engine fan blades experience dynamic instability known as flutter, leading to high-cycle fatigue and potential failure due to energy transfer from airflow, which existing technologies have not adequately addressed.
Innovation Solution
Incorporating an annular mistuning band that engages a predetermined number of blades, positioned between fore and aft retainers, to reduce flutter by selectively engaging and stiffening specific blade roots, thereby reducing vibrations and fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fan assemblies without mistuning bands are used, then the structure is simple and easy to manufacture, but the blades experience flutter and high-cycle fatigue leading to potential failure
Solution Approach 1:
An annular mistuning band is introduced as an intermediary component between the fan wheel and the blades. This band selectively engages with specific blade roots to modify their stiffness characteristics, thereby reducing flutter vibrations and preventing high-cycle fatigue without requiring fundamental changes to the overall fan assembly structure
Solution Approach 2:
The mistuning band applies local stiffness modifications to specific blade roots rather than uniformly affecting all blades. By engaging only certain blades at their root regions, the solution creates localized property changes that disrupt the synchronous vibration pattern causing flutter, while maintaining simplicity of the overall assembly
2Reliability
If mistuning bands engage all blades, then flutter reduction may be maximized, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The mistuning band is designed to engage only a predetermined number of blades (more than one but less than all) rather than requiring engagement with every blade. This partial engagement is sufficient to disrupt the flutter mechanism while significantly simplifying the assembly process and reducing manufacturing complexity compared to full-blade engagement systems
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 annular mistuning band effectively reduces flutter and high-cycle fatigue in fan blades, enhancing the durability and efficiency of the fan assembly by selectively engaging and stiffening specific blade roots, thus improving the fan's operational stability and longevity.
Implementation Method 1
During operation, the blades may experience an undesirable dynamic instability called flutter. Flutter may occur when energy associated with the airflow through the fan assembly is transferred to the blades in the form of vibrations.
Implementation Method 2
The annular mistuning band may engage the root of a predetermined number of the plurality of blades to stiffen the engaged blades relative to the unengaged blades.
Data Source
AI summary
A fan assembly for use in a gas turbine engine includes a fan wheel and a plurality of blades extending radially from the fan wheel away from a central axis of the fan assembly. Each of the blades includes a root coupled with the fan wheel and an airfoil extending radially outwardly from the root. The blades are adapted to rotate about the central axis to push air.