Asymmetric Modular Flutter Damper for Fan Stability
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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 are inadequate for effectively absorbing 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 unique dimensions and shapes, and circumferential gaps, to absorb energy and prevent fan flutter, while being integratable into optimized propulsion systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional flutter dampers are used, then fan flutter may be suppressed, but they occupy excessive space and cannot be integrated into optimized propulsion systems
Solution Approach 1:
The flutter damper is divided into multiple discrete acoustic chambers arranged in a circumferential array around the fan inlet. Each chamber is a separate acoustic resonance element that can be independently sized and positioned, allowing the overall structure to fit within the limited space of optimized propulsion systems while collectively providing comprehensive flutter suppression across multiple frequency ranges
Solution Approach 2:
The acoustic chambers are positioned in the circumferential direction around the fan inlet rather than extending axially or radially. This circumferential arrangement utilizes the available circumferential space in the propulsion system, allowing effective flutter suppression without increasing the axial length or radial dimensions of the engine
2Loss of energy
If acoustic energy absorption is targeted at higher frequencies, then non-flutter acoustic energy may be absorbed, but flutter-related frequencies remain unaddressed
Solution Approach 1:
Different acoustic chambers in the array are designed with different dimensions, shapes, and acoustic properties to target specific frequency ranges. Some chambers are optimized for higher frequency acoustic energy absorption while others are specifically tuned to resonate at and absorb energy at lower fan flutter frequencies, ensuring comprehensive coverage of both flutter and non-flutter frequency ranges
Solution Approach 2:
The acoustic chambers vary in key parameters including size, shape, and acoustic impedance to create different resonant frequencies. By changing these parameters across the chamber array, the system can simultaneously target multiple frequency ranges, including both the higher frequency acoustic energy and the lower frequency fan flutter modes
3Ease of manufacture
If symmetric chamber designs are used, then manufacturing is simplified, but adaptability to different flutter modes is limited
Solution Approach 1:
The acoustic chambers in the array are designed with asymmetric variations in dimensions and shapes rather than using identical symmetric designs. This asymmetry allows each chamber to be tuned to different frequency ranges and flutter modes, providing adaptability to suppress multiple distinct fan flutter modes while still using standardized manufacturing processes for each chamber type
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 absorbs acoustic energy at targeted frequencies, preventing fan flutter and enhancing fan flutter margin without requiring inlet redesign, offering a lightweight and scalable solution that can be integrated into existing engines.
Implementation Method 1
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
Implementation Method 2
a plurality of modular chambers 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 greater than a frequency range associated with fan flutter, and a plurality of modular chambers configured for peak acoustical energy absorption at a frequency range associated with one or more fan flutter modes, the plurality of modular chambers disposed radially outside the acoustic liner, the plurality of modular chambers including a circumferential gap between proximate circumferential ends of at least one adjacent pair of modular chambers, and the plurality of modular chambers each including a plurality of circumferentially aligned and connected chamber segments, and wherein at least one of the chambers in the plurality of modular chambers has a mutually unique length, width and/or height or shape.