Acoustic Panel Sidewall Stringers for Low Frequency Noise
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Solution Overview
Problem
Aircraft gas turbine engines generating relatively low frequency noise pose a challenge for acoustic panels due to space constraints, requiring a solution that effectively attenuates low frequency noise without increasing panel thickness, while also simplifying assembly, reducing complexity, and lowering costs.
Innovation Solution
The acoustic panel features a corrugated core with stringer bodies and sidewalls that form open cavities, allowing for longer resonance chambers without increasing panel thickness, utilizing composite or metal materials, and includes a configuration of baffles and septums to fluidly isolate adjacent portions, enabling efficient noise attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the core thickness is increased to tune resonating chambers for low frequency noise, then noise attenuation performance is improved, but panel thickness increases which violates space constraints
Solution Approach 1:
The patent introduces stringer bodies with sidewalls that extend into the channels formed by corrugations, creating a three-dimensional resonance chamber structure. This allows the resonance chambers to utilize the lateral dimension (channel width) in addition to the vertical dimension, effectively increasing the resonating volume without increasing the overall panel thickness. The stringer bodies create subdivided resonance chambers that resonate at lower frequencies while maintaining a compact thickness profile.
Solution Approach 2:
The patent segments the resonance chambers by introducing stringer bodies with multiple sidewalls that divide the channels into multiple sub-chambers. This segmentation creates a series of smaller resonating volumes along the length of the panel, each contributing to the overall low frequency noise attenuation. The segmented structure allows for distributed resonance throughout the panel volume, achieving effective low frequency attenuation without requiring a single large thick core.
2Object-affected harmful factors
If traditional acoustic panel configurations are used, then noise attenuation is achieved, but assembly time and complexity increase
Solution Approach 1:
The patent merges the stringer bodies with the corrugated core structure, where the stringer bodies are integrated directly into the channels formed by the corrugations. The sidewalls of the stringer bodies extend into the channels and are attached to the corrugated structure, creating a unified assembly. This integration eliminates the need for separate assembly steps for installing stringers into pre-formed channels, significantly reducing assembly time and complexity while maintaining the noise attenuation functionality.
3Object-affected harmful factors
If traditional acoustic panel configurations are used, then noise attenuation is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The stringer bodies serve multiple functions: they create the resonance chambers for noise attenuation, provide structural support within the panel, and define the channels for acoustic wave propagation. This multi-functionality reduces the need for additional separate components, simplifying the overall panel configuration and reducing manufacturing complexity. The same stringer structure that creates resonance chambers also provides structural integrity and acoustic channel definition.
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 configuration effectively attenuates low frequency noise by creating longer resonance chambers, reducing panel assembly time, complexity, and cost, while maintaining a compact design.
Implementation Method 1
The honeycomb core includes a plurality of resonating chambers. These resonating chambers are tuned by selecting a desired chamber length and, thus, core thickness that corresponds to a specific target frequency of noise to be attenuated.
Implementation Method 2
Each of the second sidewalls may be disposed within the second channel and configured to fluidly isolate longitudinally adjacent portions of the second channel from one another.
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A panel for attenuating noise includes a porous first skin, a second skin, and a core (26) connected between the porous first skin and the second skin. The core (26) includes a corrugated body (42) and a stringer body (44). The corrugated body (42) includes a plurality of corrugations (48) configured from at least a plurality of baffles (52) and a plurality of porous septums (53). Each of the corrugations (48) includes a respective one of the baffles (52) and a respective one of the porous septums (53). A first of the corrugations (48) forms a first channel (76) that extends laterally between and longitudinally along a first of the baffles (52) and a first of the porous septums (53). The stringer body (44) includes a plurality of sidewalls (80) arranged longitudinally along the first channel (76). Each of the sidewalls (80) is disposed within the first channel (76) and configured to fluidly isolate longitudinally adjacent portions of the first channel (76) from one another.