Piezoelectric Flutter Damper for Turbofan Fan Blade 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 do not effectively address this issue in the limited space of propulsion systems.
Innovation Solution
A flutter damper is integrated into the nacelle inlet structure, featuring a box-shaped chamber with parallel membranes embedded with piezoelectric elements, connected to an electronic engine control, which absorbs acoustic energy associated with fan flutter frequencies, providing optimal impedance characteristics to prevent fan flutter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a flutter damper is integrated into the nacelle inlet structure, then fan flutter is mitigated through acoustic energy absorption, but the available space in the propulsion system is reduced
Solution Approach 1:
The flutter damper chamber is nested within the nacelle inlet structure, with the chamber volume integrated into the existing inlet geometry. The membrane is positioned within the chamber space, creating a nested configuration that provides flutter mitigation functionality without adding external volume to the propulsion system.
Solution Approach 2:
The flutter damper utilizes the radial dimension of the nacelle inlet by positioning the chamber radially outward from the fan assembly. This dimensional approach allows the damper to occupy space that would otherwise be unused, providing acoustic energy absorption without interfering with the axial flow path or increasing the overall engine length.
2Reliability
If piezoelectric elements are embedded in membranes within the chamber, then acoustic energy absorption is enhanced at targeted frequencies, but the device complexity increases
Solution Approach 1:
Piezoelectric elements are embedded only in specific regions of the membrane where maximum acoustic energy absorption is required, rather than throughout the entire membrane structure. This localized approach enhances acoustic energy absorption at targeted flutter frequencies while minimizing the overall complexity and material requirements of the device.
Solution Approach 2:
The piezoelectric elements are configured to change their electrical properties in response to acoustic pressure variations, enabling dynamic adjustment of the membrane's acoustic impedance. This parameter change capability allows the flutter damper to effectively target specific flutter frequencies without requiring complex mechanical adjustment mechanisms.
3Ease of manufacture
If the chamber is designed to be box shaped with parallel membranes, then manufacturing is simplified, but the acoustic energy absorption efficiency may be reduced
Solution Approach 1:
The acoustic performance of the box-shaped chamber is optimized by adjusting parameters such as chamber volume, membrane surface area, and piezoelectric element configuration. These parameter changes allow the simple box-shaped geometry to achieve effective acoustic energy absorption at targeted flutter frequencies without requiring complex chamber shapes.
Solution Approach 2:
The parallel membrane configuration within the box-shaped chamber creates multiple acoustic pathways that replicate the sound absorption function of more complex geometries. This copying approach allows the simple chamber shape to achieve effective flutter mitigation through multiple simplified acoustic paths rather than a single complex structure.
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 providing peak energy absorption in the targeted frequency range, allowing for integration into optimized propulsion systems without requiring inlet redesign, and offers a lightweight, scalable design that boosts fan flutter margin.
Implementation Method 1
A flutter damper may include a chamber and a membrane embedded with a piezoelectric element, the piezoelectric element being suspended within the chamber
Implementation Method 2
providing peak energy absorption in the targeted frequency range
Implementation Method 3
absorbs acoustic energy associated with fan flutter frequencies
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
Disclosed is a flutter damper (102), including an acoustic liner (101) configured for peak acoustical energy absorption at a frequency range that is greater than a frequency range associated with fan flutter, a chamber (118, 202, 302), and a piezoelectric element disposed within a first surface of the chamber, and the chamber being configured for peak acoustical energy absorption at a frequency range that is associated with one or more fan flutter modes, and wherein the piezoelectric element is operatively connected to an electronic engine control (205).