Acoustic Panel Assembly with Folding Chamber for Low-Frequency Noise
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Solution Overview
Problem
Traditional acoustic panel configurations for aircraft propulsion systems are inadequate for attenuating longer wavelength, low-frequency noise due to space constraints and evolving engine designs, as they require thicker panels which are not feasible in all cases.
Innovation Solution
A composite acoustic panel structure comprising a perforated and non-perforated sheet with a core having cavities, forming a chamber that overlaps the core, allowing for efficient noise attenuation without excessive thickness, utilizing unoccupied space in the nacelle and inner fixed structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional thick acoustic panels are used to attenuate long wavelength, low frequency noise, then noise attenuation performance is improved, but space allocation is exceeded and the panel becomes excessively thick
Solution Approach 1:
The acoustic panel is segmented into multiple functional layers including a perforated facing layer, a porous core layer with cavities, and a non-perforated back layer. This segmentation allows each layer to contribute differently to noise attenuation, achieving effective low-frequency noise reduction through the combined effect of perforations and cavities rather than relying on uniform panel thickness
Solution Approach 2:
The invention transitions from a traditional single-layer thick panel to a multi-layer thin panel structure that utilizes the depth dimension through cavities and the surface dimension through perforations. This dimensional transformation allows the panel to achieve the acoustic performance of a thick panel while maintaining a thin overall profile suitable for modern engine nacelle space constraints
2Length of stationary object
If relatively thin acoustic panels are used, then space allocation is optimized, but the ability to attenuate long wavelength, low frequency noise is insufficient
Solution Approach 1:
The core layer of the acoustic panel is designed as a porous material with a network of cavities and interconnected pores. This porous structure allows sound waves, particularly low-frequency long wavelength noise, to penetrate into the material and be attenuated through viscous losses and thermal conduction within the pore structure, achieving effective noise reduction in a thin panel configuration
Solution Approach 2:
The invention changes the physical parameters of the panel by introducing specific cavity dimensions, perforation patterns, and porous material properties. These parameter optimizations enable the thin panel to resonate at frequencies that match low-frequency noise sources, enhancing attenuation performance without increasing panel thickness
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 longer wavelength, low-frequency noise while maintaining a compact design, optimizing noise reduction without the need for excessively thick panels, thus addressing the limitations of traditional configurations.
Implementation Method 1
an acoustic panel structure for an aircraft propulsion system. This acoustic panel structure includes a first sheet, a second sheet, a core and a third sheet... The core is configured with a plurality of cavities between the first perforated region and the second perforated region
Data Source
AI summary
An acoustic panel structure includes a perforated front sheet, a back sheet and a porous core between the front sheet and the back sheet. The acoustic panel structure also includes a non-perforated back cover which overlaps a portion of the back sheet. A portion of the back sheet is perforated and another portion of the back sheet is not perforated. An acoustic chamber is formed at least in part by the space between the back sheet and the back cover. The acoustic chamber may also be formed in part by the space between the front sheet and back cover. The space between the back sheet and the back cover is generally elongated in the x-y direction of the acoustic panel structure. This relatively thin acoustic panel structure is configured to attenuate long wavelength and low frequency noise.