External Acoustic Panel Structure for Fan Case Noise Attenuation
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Solution Overview
Problem
Existing acoustic panels for aircraft propulsion assemblies are costly and time-consuming to manufacture, and they lack resilience while effectively attenuating noise.
Innovation Solution
The development of acoustic panels with a unitary core and back skin, mounted externally on the fan case system, utilizing a honeycomb structure and perforated portions for Helmholtz resonance to dissipate acoustic energy, allowing for simplified manufacturing and improved noise attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional acoustic attenuation panels are used, then noise attenuation is achieved, but manufacturing cost and time increase
Solution Approach 1:
The patent combines the acoustic panel with the fan case system by mounting the panel directly to the exterior surface of the fan case system, integrating two separate components into a unified assembly. This reduces manufacturing steps and assembly time while maintaining noise attenuation effectiveness through the resonant cavity structure formed by the integrated design.
2Reliability
If traditional acoustic attenuation panels are used, then noise attenuation is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The acoustic panel is segmented into distinct functional components: a core structure with resonant cavities, a face skin with perforations, and a back skin. This segmentation allows each component to be manufactured independently using optimized processes and then assembled, reducing overall manufacturing complexity while maintaining effective noise attenuation through the coordinated function of each segment.
3Reliability
If traditional acoustic panels are used, then noise attenuation is achieved, but panel resilience decreases
Solution Approach 1:
The acoustic panel employs composite construction with a core structure made from resilient materials capable of withstanding environmental conditions, combined with face and back skins. This composite approach enhances panel resilience and structural integrity while maintaining the resonant cavity geometry necessary for effective noise attenuation through Helmholtz resonance and acoustic absorption.
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 design reduces manufacturing time and cost while enhancing acoustic panel resilience and noise attenuation, minimizing foreign object damage and providing flexible configuration options.
Implementation Method 1
the cells of the core, covered by the face skin and the back skin, may form resonant cavities that contribute to the dissipation of incident acoustic energy by canceling acoustically reflected waves and/or converting acoustic energy into heat, such as by Helmholtz resonance
Implementation Method 2
form resonant cavities that contribute to the dissipation of incident acoustic energy
Data Source
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AI summary
A propulsion assembly (10) includes a fan (18) and a fan case system (20) disposed about the fan (18). The fan case system (20) includes at least one perforated portion (48) including a plurality of holes (50). The propulsion assembly (10) further includes at least one acoustic panel (24) mounted to the exterior surface (44) of the fan case system (20) coincident with the at least one perforated portion (48). The at least one acoustic panel (24) includes a core (26) including a plurality of cells (28) extending between a first side (30) of the core (26) and a second side (32) of the core (26). The at least one acoustic panel (24) further includes a back skin (34) attached to the second side (32) of the core (26). The first side (30) of the core (26) is in contact with the exterior surface (44) of the fan case system (20) to form a plurality of resonant cavities (52) defined by the plurality of holes (50), the plurality of cells (28), and the back skin (34).