Movable Skin Cellular Structure for Aircraft Nacelle Acoustic Panels
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Solution Overview
Problem
Aircraft propulsion unit nacelles face challenges in attenuating noise and managing thermomechanical stresses due to the differential thermal expansion of ceramic and metal materials used in acoustic panels, leading to mechanical stresses and reduced durability.
Innovation Solution
A cellular structure with movable skin elements connected to lateral partition walls, allowing for thermal expansion flexibility and reduced mechanical stresses, combined with a continuous skin for acoustic attenuation, using materials like nickel or titanium alloys with ceramic or composite skins for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ceramic materials and metal components are integrated in acoustic panels to reduce costs, then material cost is reduced, but thermomechanical stresses increase due to different thermal expansion coefficients
Solution Approach 1:
The acoustic panel is divided into a cellular structure with individual cells that can expand independently, and skin elements that are separately attached to partition walls. This segmentation allows different materials to expand at different rates without creating excessive stress across the entire structure.
Solution Approach 2:
The skin elements are made movable relative to the partition walls through specific attachment mechanisms, allowing the structure to dynamically adapt to thermal expansion. The skin elements can move along the partition walls to accommodate dimensional changes without creating rigid constraints that would generate high stresses.
2Stress or pressure
If skin elements are made movable to accommodate thermal expansion, then thermomechanical stresses are reduced, but structural stability decreases
Solution Approach 1:
The skin elements are pre-attached to the partition walls in a controlled manner during manufacturing, establishing their initial positions and movement constraints before the structure is installed in the aircraft engine environment. This preliminary attachment ensures proper alignment and controlled movement during thermal cycles.
Solution Approach 2:
The skin elements function as flexible components that can deform and move relative to the partition walls while maintaining their structural integrity. This flexibility allows the skin elements to accommodate thermal expansion without compromising the overall structural stability of the acoustic panel.
3Reliability
If multiple skin elements are used to close channels, then acoustic attenuation performance is improved, but device complexity increases
Solution Approach 1:
The skin elements serve multiple functions: they close the channels to improve acoustic attenuation, provide attachment points for the cellular structure, and act as flexible components to accommodate thermal expansion. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in overall device complexity.
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 reduces thermomechanical stresses and maintains acoustic attenuation performance, improving the durability and conformability of acoustic panels in aircraft propulsion units while minimizing material costs.
Implementation Method 1
Such a longitudinal mobility can be caused by thermal expansion of the cellular structure
Data Source
AI summary
The present disclosure relates to a cell structure for an acoustic attenuation device for a nacelle of an aircraft propulsion assembly. This cell structure includes lateral partitions forming channels that each extend between a first end and a second end and skin elements arranged so that each channel is at least partly closed at the first end thereof by at least one skin element. Each skin element is connected to a respective lateral partition and can move relative to the other lateral partitions. A continuous skin can be assembled on this cell structure so as to at least partly close the channels at the second end thereof and to thus form an acoustic attenuation device.