Segmented Acoustic Liner Geometry for Broadband Fan Noise
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Solution Overview
Problem
Existing noise attenuation liners in gas turbine engines are limited in their ability to efficiently attenuate all noise frequencies due to compromises required for optimal attenuation of undesirable frequencies, leading to suboptimal performance at other frequencies.
Innovation Solution
An acoustic liner assembly with varied geometric properties, including varying radial thicknesses, porosities, and core depths along the axial and circumferential length of the bypass duct, tailored to target specific noise frequencies for optimized noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a noise attenuation liner is tuned to efficiently attenuate the most undesirable frequencies, then noise reduction at those specific frequencies is improved, but the effective attenuation of other noise frequencies deteriorates
Solution Approach 1:
The acoustic liner is divided into multiple sections along the axial direction, with each section having different geometric properties (thickness, porosity, core depth) optimized for specific frequency ranges. This allows different parts of the liner to target different noise frequencies simultaneously, resolving the contradiction between specialized frequency attenuation and broadband coverage
Solution Approach 2:
The liner is segmented into multiple discrete sections, each with tailored acoustic properties. This segmentation enables independent optimization of each section for different frequency bands while maintaining overall broadband attenuation capability across the entire liner assembly
2Object-affected harmful factors
If the acoustic liner geometry is varied to target specific noise frequencies, then noise reduction performance is improved, but manufacturing complexity increases
Solution Approach 1:
The invention varies key geometric parameters (thickness, porosity, core depth) of the liner sections to optimize noise attenuation at different frequencies. By systematically adjusting these parameters across different sections, the design achieves superior noise reduction performance while maintaining manufacturability through controlled parameter variations rather than completely complex geometries
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 liner assembly achieves significant noise reduction, with tone noise reductions up to 10 dB and cumulative aircraft noise reductions of approximately 1-2 EPNdB, effectively addressing multiple frequency ranges.
Implementation Method 1
an acoustic liner assembly for reducing emitted noise propagating through a duct
Data Source
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AI summary
A geared turbofan engine (10) includes a first rotor (20), a fan (28), a second rotor, a gear train (26), a fan casing, a nacelle (12) and a plurality of discrete acoustic liner segments (38a, 38b, 38c, 38d, 38e, 38f). The fan (28) is connected to the first rotor (20) and is capable of rotation at frequencies between 200 and 6000 Hz and has a fan pressure ratio of between 1.25 and 1.60. The gear train (26) connects the first rotor (20) to the second rotor. The fan casing and nacelle (12) are arranged circumferentially about a centerline (CL) and define a bypass flow duct (30) in which the fan (28) is disposed. The plurality of discrete acoustic liner segments (38a, 38b, 38c, 38d, 38e, 38f) with varied geometric properties are disposed along the bypass flow duct (30).