Angled Corrugated Core Acoustic Panel for Low Frequency Noise
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Solution Overview
Problem
Aircraft gas turbine engines generate relatively low frequency noise, which existing acoustic panels struggle to attenuate effectively due to space constraints and structural integrity limitations, necessitating a solution that can reduce noise without increasing panel thickness or compromising structural integrity.
Innovation Solution
The acoustic panel features a cellular core with angled baffles and septums, forming an open cavity structure that increases surface area for bonding and enhances stiffness, allowing for effective noise attenuation of low frequency noise without increasing panel thickness, and includes a perforated face skin and solid back skin, with the cellular core being at least ten to forty times thicker than the skins, providing enhanced structural integrity.
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 and space requirements increase
Solution Approach 1:
The patent transitions from a conventional flat honeycomb core to a corrugated core structure that introduces out-of-plane geometry. The corrugations create three-dimensional pathways for sound waves, effectively increasing the acoustic path length and resonating chamber volume without proportionally increasing the panel's overall thickness. This dimensional transformation allows low frequency noise attenuation while maintaining space constraints.
Solution Approach 2:
The corrugated core structure introduces curved and angled surfaces instead of flat planes. The sinusoidal or triangular corrugation profiles create varying path lengths for sound waves, enhancing acoustic performance. The curved geometry of corrugations allows sound waves to travel longer distances through the core, improving low frequency attenuation without requiring a thicker panel.
2Object-affected harmful factors
If the core thickness is increased to improve noise attenuation, then acoustic performance is improved, but structural integrity and shear force resistance deteriorate due to increased flexibility
Solution Approach 1:
The corrugated core structure inherently provides superior structural integrity compared to flat panels of equivalent thickness. The curved geometry of corrugations creates arch-like structures that naturally resist bending and shear forces. This curvature distributes mechanical loads more effectively throughout the panel, maintaining structural strength while enabling the acoustic performance benefits of increased effective thickness.
Solution Approach 2:
The patent employs a composite structure combining the corrugated core with face sheets. This composite construction leverages the high stiffness-to-weight ratio of the corrugated geometry working in conjunction with the face sheets, creating a sandwich structure that simultaneously achieves excellent acoustic performance and structural integrity. The multi-material or multi-layer composite design allows optimization of both acoustic and mechanical properties.
3Ease of manufacture
If conventional honeycomb core is used, then manufacturing is simple, but noise attenuation of low frequency noise is ineffective due to space constraints
Solution Approach 1:
The corrugated core structure can be manufactured using adapted honeycomb fabrication processes, maintaining relative manufacturing simplicity. The corrugation pattern can be integrated into the honeycomb cell structure during manufacturing, allowing the complex three-dimensional geometry to be produced using established techniques with minimal additional complexity. This preserves ease of manufacture while achieving superior acoustic performance.
4Length of stationary object
If panel thickness is reduced to meet space constraints, then space efficiency is improved, but noise attenuation performance deteriorates
Solution Approach 1:
The corrugated core structure creates acoustic pathways that extend in the out-of-plane direction, effectively increasing the acoustic treatment volume within a thin profile. Sound waves navigate through the three-dimensional corrugation geometry, experiencing extended path lengths and enhanced attenuation without requiring increased panel thickness. This dimensional approach allows thin panels to achieve the noise attenuation performance of much thicker conventional panels.
Solution Approach 2:
The curved corrugation profiles create varying sound paths that maximize acoustic interaction within the available thickness. The sinusoidal or triangular wave patterns ensure sound waves traverse longer distances through the core material, improving attenuation efficiency per unit thickness. This curved geometry allows the panel to achieve superior noise attenuation in a space-constrained application.
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 attenuates low frequency noise while maintaining or improving structural integrity and space efficiency, enabling the panel to withstand higher shear forces and distribute loads uniformly, thus addressing the limitations of previous acoustic panels.
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
The cellular core includes a plurality of angled baffles and septums that form a corrugated structure. The increased surface area of the cellular core provides enhanced bonding area to the first and second skins.
Data Source
Figure 1
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AI summary
A panel (20) is provided for attenuating noise. This panel includes a first skin (22), a second skin (24) and a core (26), which forms a plurality of cavities (54) vertically between the first skin (22) and the second skin (24). The core (26) includes a first wall (48), a second wall (48), a first baffle (50), a second baffle (50) and a first septum (52). The cavities (54) include a first cavity (54) formed laterally between the first wall (48) and the second wall (48) and longitudinally between the first baffle (50) and the second baffle (50). The first septum (52) is longitudinally between the first baffle (50) and the second baffle (50) and divides the first cavity (54) into fluidly coupled sub-cavities (54A,54B). The first septum (52) is angularly offset from the first wall (48) by an acute angle (88). One or more perforations (34) in the first skin (22) are fluidly coupled with the first cavity (54).