Aircraft Leading-Edge Acoustic Attenuation for Propulsion Noise
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Solution Overview
Problem
The integration of large-diameter turbojet engines and turboprops on commercial aircraft generates significant noise due to the interaction of the air flow from rotating parts with the aircraft structure, particularly at the leading edge, which is exacerbated by reduced space for acoustic treatments.
Innovation Solution
A propulsion assembly with a turbomachine featuring an acoustic attenuation device that modifies the leading edge of structural elements, such as aircraft airfoils, with localized corrugations or porous materials to reduce noise without affecting aerodynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If large-diameter turbojet engines with high BPR are integrated on aircraft, then propulsive efficiency increases and fuel consumption decreases, but noise levels increase due to air flow interaction with structural elements
Solution Approach 1:
The patent applies local quality by implementing acoustic attenuation devices specifically at the leading edge of structural elements where air flow interaction generates noise. The corrugations are localized to the region most affected by turbulent flows from the rotating parts, rather than applying treatment across the entire structure. This targeted approach reduces noise at the source while preserving the overall aerodynamic efficiency of the large-diameter engine integration.
Solution Approach 2:
The corrugated leading edge acts as an intermediary element between the air flow and the structural element. The corrugations modify the air flow characteristics locally, creating a transition zone that reduces the intensity of turbulent flows impacting the flat surfaces. This intermediary structure dissipates acoustic energy while allowing the main air flow to pass through, thus mediating between the high-speed jet and the structural element.
2Object-generated harmful factors
If acoustic treatments are applied to reduce noise, then noise levels decrease, but available space for treatment is reduced due to short and thin nacelle configuration
Solution Approach 1:
The invention concentrates acoustic treatment on the leading edge of structural elements, which is the specific location where air flow interaction generates the most noise. By applying corrugations only to this critical region rather than covering the entire nacelle surface, the patent maximizes noise reduction effectiveness within the limited space available on short and thin nacelles.
Solution Approach 2:
The corrugations introduce a new dimensional feature (surface undulations) to the leading edge, transforming a two-dimensional flat surface into a three-dimensional textured surface. This dimensional change increases the effective surface area for acoustic treatment without significantly increasing the overall footprint or volume occupied by the nacelle, thus fitting within the constrained space.
3Object-generated harmful factors
If leading edge is modified with acoustic attenuation device, then noise from air flow interaction is reduced, but aerodynamic performance may be affected
Solution Approach 1:
The corrugations are applied locally to the leading edge region where air flow interaction generates noise, rather than modifying the entire airfoil surface. This localized modification minimizes the impact on overall aerodynamic performance while effectively addressing the noise generation zone. The rest of the airfoil maintains its original smooth surface optimized for aerodynamic efficiency.
Solution Approach 2:
The patent applies acoustic attenuation partially, only to the leading edge portion most affected by turbulent flows from rotating parts. The corrugation coverage is limited to the specific region where noise generation is most intense, rather than applying treatment across the entire leading edge or airfoil surface. This partial application reduces noise effectively while minimizing interference with aerodynamic flow.
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 acoustic attenuation device effectively reduces noise generated by the interaction of air jets with structural elements, adapting to local flow properties and minimizing impact on aerodynamic performance.
Implementation Method 1
The acoustic attenuation device being a local modification of the structure and/or of the profile of the leading edge... effectively reduces noise generated by the interaction of air jets with structural elements
Implementation Method 2
The turbulent flows generated in the wake of the fan 30 (or of the propellers 31) directly impact the leading edge 11... produces broadband noise
Data Source
AI summary
Propulsion assembly for an aircraft comprising a turbomachine having at least one rotating part rotating about an axis of rotation, an attachment strut, and a structural element carrying the turbomachine via the attachment strut, the rotating part being disposed upstream of the structural element and of the attachment strut such that an air jet emerging from the rotating part, in the wake of thereof, impacts the structural element and the attachment strut, a leading edge of the structural element and/or of said attachment strut locally comprising at least one acoustic attenuation device disposed at least partly in the wake of the rotating part, the acoustic attenuation device being a local modification of the structure and/or of the profile of the leading edge.