Multi Degree of Freedom Flutter Damper for Geared Turbofan
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Solution Overview
Problem
Geared turbofan architectures with low pressure ratio fans are susceptible to fan flutter, an aeromechanical instability that can be detrimental to fan blade life, and existing solutions fail to effectively absorb acoustic energy within the limited space of propulsion systems.
Innovation Solution
A flutter damper comprising an acoustic liner and modular chambers configured for peak acoustical energy absorption at frequencies associated with fan flutter modes, with the chambers disposed radially outside the acoustic liner and separated by circumferential gaps, allowing for efficient energy absorption and integration into optimized propulsion systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional acoustic liner is used alone, then it provides basic noise absorption, but it cannot effectively absorb acoustic energy at fan flutter frequencies
Solution Approach 1:
The acoustic treatment is divided into two distinct segments: a conventional acoustic liner for general noise absorption and additional modular chambers specifically tuned to fan flutter frequencies. This segmentation allows each component to specialize in absorbing acoustic energy within its optimal frequency range, with the modular chambers providing targeted attenuation at flutter frequencies that the standard liner cannot achieve alone.
2Reliability
If larger acoustic treatment structures are added to improve flutter damping, then acoustic energy absorption improves, but the available space in the propulsion system is exceeded
Solution Approach 1:
The modular chambers are nested within the existing nacelle inlet structure, utilizing the available radial and axial space efficiently. The chambers are positioned between the acoustic liner and the nacelle inlet skin, conforming to the contours of the existing structure. This nesting approach allows the addition of flutter-damping functionality without significantly increasing the overall envelope of the propulsion system.
Solution Approach 2:
The acoustic treatment extends into the radial dimension by placing chambers between the acoustic liner and the inlet skin, rather than only extending axially. This dimensional approach allows effective flutter damping within the constrained axial length of the nacelle inlet, utilizing the radial space that would otherwise be unused.
3Stability of the object's composition
If modular chambers are placed adjacent to each other without gaps, then structural integrity improves, but manufacturing and assembly complexity increases
Solution Approach 1:
The chamber array is segmented into discrete modular units that can be manufactured independently and then assembled together. The circumferential gaps between chambers serve as natural separation features that simplify manufacturing by allowing each chamber to be produced as a separate component rather than as a single complex integrated structure.
Solution Approach 2:
The circumferential gaps between adjacent modular chambers serve as intermediary spaces that facilitate assembly. These gaps allow for alignment tolerances, enable the insertion of sealing elements or fasteners, and provide space for thermal expansion or structural deformation without compromising the overall structural integrity of the chamber array.
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 mitigates fan flutter by absorbing acoustic energy at targeted frequencies, enhancing fan stability and compatibility with reduced space constraints, thereby improving engine reliability and performance.
Implementation Method 1
the acoustic liner being configured for peak acoustical energy absorption at a frequency range that is greater than a frequency range associated with fan flutter, and a plurality of modular chambers, each of the plurality of modular chambers being configured for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes
Data Source
AI summary
Disclosed is a flutter damper, including an acoustic liner in fluid communication with a fluid flow, the acoustic liner being configured for peak acoustical energy absorption at a frequency range that is greater than a frequency range associated with fan flutter, and a plurality of modular chambers, each of the plurality of modular chambers being configured for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes, and the plurality of modular chambers being disposed radially outside of the acoustic liner, and the plurality of modular chambers including a circumferential gap between proximate circumferential ends of at least one adjacent pair of modular chambers, wherein, the plurality of modular chambers each include a plurality of circumferentially aligned and connected chamber segments.