Gradient Porosity Coating for Turbomachine Noise Reduction
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Solution Overview
Problem
Current noise reduction technologies for aircraft engines, particularly in new generation turbofans, are inadequate in reducing noise across a wider frequency range, including low frequencies, while maintaining engine performance, and often require additional machining to correct shape defects in composite casings.
Innovation Solution
A property gradient coating with multiple layers of thermosetting materials is applied via additive manufacturing to the internal walls of turbomachine casings, featuring ordered networks of channels and microchannels with controlled porosity, designed to reduce noise, aerodynamic losses, and absorb acoustic and ballistic energy, while addressing shape defects and non-axisymmetric geometries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional composite panels with honeycomb core are used for acoustic coatings, then noise reduction is achieved, but the available area is reduced in new generation engines and additional machining is required to correct shape defects
Solution Approach 1:
The patent changes the physical and chemical parameters of the coating material by using a property gradient approach, where the material composition and porosity vary through the thickness of the coating. This allows the coating to simultaneously achieve acoustic absorption, aerodynamic performance, and shape defect compensation without requiring additional machining operations.
Solution Approach 2:
The patent employs composite materials with a gradient structure, combining materials with different porosity values (first porosity in the range of 60-80%, second porosity in the range of 80-95%) to create a multi-functional coating that addresses noise reduction, aerodynamic losses, and shape defects simultaneously.
2Object-affected harmful factors
If acoustic coatings are applied to reduce noise, then sound intensity is reduced, but the frequency range coverage is insufficient particularly for low frequencies in new generation engines
Solution Approach 1:
The patent applies local quality by creating different porosity zones within the coating thickness. The first porosity (60-80%) is optimized for certain frequency ranges while the second porosity (80-95%) targets different frequency ranges, particularly low frequencies. This local differentiation of material properties enables broad frequency coverage.
Solution Approach 2:
By varying the porosity parameter through the coating thickness, the patent optimizes acoustic absorption across different frequency ranges. The gradient in porosity creates different acoustic impedance zones that effectively absorb sound waves of varying frequencies, particularly enhancing low-frequency noise reduction.
3Object-affected harmful factors
If porous materials are used for acoustic absorption, then acoustic absorption is maximized, but radial aerodynamic losses increase
Solution Approach 1:
The patent optimizes the porosity parameter by implementing a gradient structure rather than using uniform porosity. The first porosity (60-80%) provides a balance between acoustic absorption and aerodynamic performance, while the second porosity (80-95%) enhances acoustic absorption. This gradual transition minimizes aerodynamic losses while maximizing acoustic absorption.
Solution Approach 2:
Different porosity zones are strategically positioned within the coating thickness. The lower porosity region (60-80%) is optimized for aerodynamic flow, while the higher porosity region (80-95%) is optimized for acoustic absorption. This local optimization reduces aerodynamic losses while maintaining effective noise reduction.
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 coating effectively reduces noise pollution across a broader frequency range, maintains engine performance, and compensates for shape defects with minimal impact on specific fuel consumption, offering a commercial advantage by enhancing noise reduction and aerodynamic stability.
Implementation Method 1
a first layer consisting of a three-dimensional scaffolding of filaments of an abradable material forming an ordered network of channels or micro-channels whose pore sizes are between 50 and 250 microns and the porosity greater than 85%
Implementation Method 2
a second layer having a energy dissipation function of the acoustic waves striking said outer surface of said coating and consisting of a three-dimensional scaffolding of filaments of a first thermosetting material forming an ordered network of channels and or micro-channels whose pore sizes are between 50 and 400 microns and porosity greater than 60%
Data Source
Figure 1
Figure 2~3
Figure 4a~4d
AI summary
Coating with property gradient intended to be affixed by additive manufacturing to an inner wall of a housing (46) mounted at the periphery of mobile rotor blades of a turbomachine, the coating comprising, as superposed layers, from an outer surface of the coating to this inner wall of a housing, on the one hand a first layer (54) constituted by a three-dimensional scaffold of filaments of an abradable material forming an ordered network of channels or microchannels, of which the pore sizes are between 50 and 250 microns and the porosity is greater than 85%, and on the other hand a second layer (52) having a function of energy dissipation of the acoustic waves hitting the outer surface of the coating and constituted by a three-dimensional scaffold of filaments of a first thermosetting material forming an ordered network of channels or microchannels, of which the pore sizes are between 50 and 400 microns and the porosity is greater than 60%.