Thrust Reverser Cascade Acoustic Treatment
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Solution Overview
Problem
Current acoustic treatment methods for turbomachines, particularly in thrust reversers, fail to effectively match the optimal thickness of acoustic panels with the available volume, leading to suboptimal noise attenuation due to changing dominant frequencies associated with slower rotating bladed wheels and fewer blades, and they also incur significant cost, mass, and bulk penalties.
Innovation Solution
A cascade type thrust reverser device with a perforated wall and movable acoustically reflecting wall, which includes a porous interface and a sealed frame, allows for reorientation of air flow and minimization of head losses during thrust reversal, while optimizing acoustic absorption by tuning cavities to specific sound frequencies using a Helmholtz resonator design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional acoustic treatment panels are integrated in thrust reversers, then acoustic absorption is provided, but the radial bulk of the panels increases the overall size of the thrust reverser device
Solution Approach 1:
The acoustic treatment panels are nested within the cavities formed by the cascade structure itself. The cascade partitions create internal cavities that house the acoustic panels, allowing the acoustic treatment to be integrated within the existing structural volume rather than adding external bulk.
Solution Approach 2:
The cascade structure serves dual functions: it provides thrust reversal capability through its geometry while simultaneously creating cavities that accommodate acoustic treatment panels. This multi-functionality eliminates the need for separate acoustic treatment structures, reducing overall device volume.
2Object-affected harmful factors
If the radial thickness of acoustic treatment panels is increased to match optimal treatment frequency, then acoustic attenuation effectiveness is improved, but the volume available in the nacelle is exceeded
Solution Approach 1:
The acoustic treatment is applied locally within the specific cavities formed by the cascade structure, rather than requiring uniform thick panels across the entire nacelle. Each cavity is positioned to treat specific noise frequencies generated by the fan-OGV module, providing targeted acoustic attenuation within available space.
3Volume of moving object
If thrust reverser cascade structure is made more compact to reduce bulk, then device size is reduced, but acoustic absorption capability is compromised
Solution Approach 1:
The cascade structure is segmented into multiple partitions that create numerous small cavities. These segmented cavities provide sufficient total acoustic absorption surface area and volume while maintaining a compact overall device geometry. The segmentation allows acoustic treatment to be distributed throughout the structure rather than concentrated in large bulk.
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 enables efficient reorientation of air flow and minimization of head losses during thrust reversal, while maximizing acoustic absorption when inactive, thus improving the overall performance and reducing the bulk and cost associated with thrust reversers.
Implementation Method 1
a porous interface formed by at least one layer of porous material and positioned at the interface between the perforated wall and the cascade
Implementation Method 2
optimizing acoustic absorption by tuning cavities to specific sound frequencies using a Helmholtz resonator design
Data Source
AI summary
A cascade type thrust reverser device for a turbomachine of an aircraft, comprising a cascade including first partitions, second partitions intersecting the first partitions, and cavities, and a casing including a housing into which the cascade can be inserted in a first direction, the casing and the cascade being in relative translation with respect to one another in the first direction. The casing comprises a perforated wall intended to be in contact with an air flow and including orifices and wall strips with no orifices and intended to face the first walls of the cascade when the device is in a first position in which the cascade is entirely positioned in the housing.