Nacelle Liner Unit Cell Resonator Networks for Broadband Noise Attenuation
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Solution Overview
Problem
Conventional acoustic panels for noise attenuation in propulsion systems, such as gas turbine engines, often have limitations in effectively reducing noise across a broad frequency range, particularly in aerospace applications, where they may not provide sufficient noise reduction at specific frequencies and are heavy, leading to weight and fuel efficiency issues.
Innovation Solution
The development of a noise attenuation panel featuring a periodic structure composed of interconnected unit cells with axial and lateral tubes, where the tubes are sized differently and can be partially or completely sealed, forming a complex network that enhances sound absorption across a broader frequency range, and can be fabricated using additive manufacturing techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional single-degree of freedom cell-based structures are used, then the panel structure is simple and lightweight, but the noise attenuation performance is insufficient across broad frequency ranges
Solution Approach 1:
The unit cell is segmented into multiple independent axial tubes (first axial tube and second axial tube) and lateral tubes, each capable of resonating at different frequencies. This segmentation allows the single unit cell to provide broadband noise attenuation across multiple frequency ranges simultaneously, resolving the contradiction between simple structure and effective noise attenuation.
Solution Approach 2:
Multiple axial tubes and lateral tubes are nested within the single unit cell structure, with tubes positioned concentrically or adjacently. The first axial tube, second axial tube, and lateral tubes are all contained within the same unit cell boundary, enabling complex multi-frequency attenuation functionality while maintaining a compact form factor that doesn't significantly increase overall panel complexity.
2Reliability
If multiple layers of resonators are used to provide broader frequency noise reduction, then the noise attenuation bandwidth increases, but the panel weight increases
Solution Approach 1:
Instead of adding multiple layers in the thickness direction (z-dimension), the invention utilizes the radial and lateral dimensions within a single layer by incorporating multiple axial tubes and lateral tubes. This dimensional approach achieves broadband attenuation without increasing panel thickness or weight proportionally, as the additional resonating elements share the same structural space.
Solution Approach 2:
Multiple resonating elements (first axial tube, second axial tube, lateral tubes) are merged into a single integrated unit cell structure rather than being separate layers. This merging allows the combined structure to function as a unified broadband attenuator, achieving the noise reduction of multiple layers while using a single physical layer, thereby reducing overall panel weight.
3Reliability
If tubes of different sizes are used in the unit cell, then the frequency attenuation range is broadened, but the manufacturing precision requirements increase
Solution Approach 1:
The invention deliberately employs parameter changes by using axial tubes and lateral tubes with different sizes, lengths, and cross-sectional areas within the same unit cell. These parameter variations are designed to create resonators tuned to different frequencies, broadening the attenuation range. The additive manufacturing process enables these parameter changes to be implemented with controlled precision, balancing performance requirements with manufacturing capabilities.
4Strength
If additive manufacturing techniques are used to fabricate the panel, then structural efficiency and design flexibility increase, but manufacturing complexity increases
Solution Approach 1:
Multiple complex geometric features (axial tubes, lateral tubes, central bodies, sealing structures) that would require separate manufacturing steps and assembly operations are merged into a single monolithic structure fabricated in one additive manufacturing process. This eliminates assembly complexity while maintaining the structural efficiency and design flexibility benefits of the complex geometry, effectively resolving the manufacturing complexity concern.
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
This solution provides improved noise attenuation performance with potential weight reduction and increased structural efficiency, allowing for better noise suppression at specific frequencies and broader bandwidths compared to conventional single-degree of freedom cell-based structures.
Implementation Method 1
This enables the cells of the core structure to act like individual Helmholtz or quarter-wave resonators that attenuate a certain tone or tones
Implementation Method 2
This enables the cells of the core structure to act like individual Helmholtz or quarter-wave resonators that attenuate a certain tone or tones
Data Source
AI summary
An acoustic attenuation structure for a gas turbine engine includes a periodic structure having a first unit cell, the first unit cell having a first central body and a first axial tube disposed on the first central body and a second axial tube disposed on the first central body, opposite the first axial tube, each of the first axial tube and the second axial tube being in fluid communication with one another through the first central body.