Multi-Splice Acoustic Liner for Aircraft Engine Noise Reduction
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Solution Overview
Problem
Conventional acoustic liners for aircraft engines face challenges in minimizing acoustically inactive zones, which are difficult and costly to achieve, and result in incomplete noise attenuation due to scattered noise energy into lower order modes that are hard to attenuate.
Innovation Solution
The acoustic liner assembly incorporates a face sheet with noise energy absorption areas and noise reflective areas, where the reflective areas scatter higher order acoustic modes into lower modes that cancel each other out, reducing the propagation of difficult-to-attenuate low order modes, and aligning honeycomb splices under face sheet splices minimizes scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional acoustic liners use a splice-free face sheet to minimize acoustically inactive zones, then noise attenuation is improved, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The face sheet is divided into multiple modular panels that can be spliced together. Each panel contains acoustic openings, and the spliced configuration creates acoustically inactive zones. This segmentation allows practical manufacturing while maintaining noise attenuation performance through the distributed acoustic activity across multiple panels.
Solution Approach 2:
Different regions of the face sheet are designed with different properties: acoustic openings in active zones for noise transmission, and solid reflective zones for scattering sound waves. This local differentiation allows the liner to handle both higher-order modes (through acoustic openings) and lower-order modes (through reflective scattering), resolving the contradiction between manufacturing practicality and noise attenuation effectiveness.
2Ease of manufacture
If acoustic liners include splices and seams in the face sheet, then manufacturing becomes practical, but noise energy is scattered into lower order modes that are difficult to attenuate
Solution Approach 1:
The splices and seams that create acoustically inactive zones are not eliminated but instead utilized as reflective surfaces. These previously harmful features are converted into beneficial scattering elements that redirect lower-order mode noise into higher-order modes, which are then effectively attenuated by the acoustic openings in the face sheet panels.
Solution Approach 2:
Instead of trying to eliminate acoustically inactive zones caused by splices, the invention inverts the approach by designing these zones to actively scatter and redirect noise energy. The solid portions between acoustic openings serve as reflective surfaces that convert difficult-to-attenuate lower-order modes into easier-to-attenuate higher-order modes.
3Object-affected harmful factors
If the liner assembly includes both noise absorption areas and noise reflective areas, then both higher order and lower order acoustic modes are effectively attenuated, but the structure becomes more complex
Solution Approach 1:
The face sheet panels serve multiple functions simultaneously: they provide structural support, contain acoustic openings for absorbing higher-order modes, and have solid reflective portions for scattering lower-order modes. This multi-functionality achieves broadband noise attenuation without requiring separate components for each function, thereby limiting the increase in structural complexity.
Solution Approach 2:
The acoustic absorption function and acoustic reflection function are merged into a single integrated face sheet structure. The same panels that provide acoustic openings for absorption also provide solid surfaces for reflection, combining multiple noise control functions into one unified component system.
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 effectively reduces noise emission from aircraft engines by efficiently attenuating higher order acoustic modes and eliminating low order noise propagation, without the complexity of creating a completely acoustically active and absorptive liner assembly.
Implementation Method 1
The noise reflective areas scatter higher order acoustic modes into either a plurality of lower order acoustic modes that tend to cancel each other, or even higher order modes that are easier to attenuate
Implementation Method 2
Acoustic energy generated by rotation of the fan blades is transmitted through a plurality of openings in the face sheet to the honeycomb structure where the acoustic energy dissipates to provide an overall noise reduction
Data Source
AI summary
A liner assembly for an aircraft engine housing includes a noise attenuation structure that is covered by a face sheet. The face sheet covering the noise attenuation structure includes a surface having a plurality of circumferentially spaced apart acoustic energy absorption areas that are interspersed between a corresponding plurality of acoustic energy reflective areas. The acoustic energy reflective areas scatter higher order acoustic modes into a plurality of lower order modes. The difficult to attenuate lower order acoustic modes produced by the various acoustic energy cancel each other out to provide significant improvement in liner noise reduction efficiency.