Deployable Rough Surface for Gas Turbine Jet Noise Reduction
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Solution Overview
Problem
Gas turbine engines continue to produce significant noise, particularly at high power conditions, due to the interaction of air streams and ambient air, despite advancements in bypass ratios and nozzle designs.
Innovation Solution
A deployable noise-reducing component within the exhaust nozzle of a gas turbine engine, comprising an annular perforated sleeve and a displaceable wall with dimples, which forms a rough surface when pressurized to reduce jet noise by increasing the boundary layer thickness and slowing down the exhaust stream, and retracts when not needed to minimize drag and fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a permanent rough surface is added to the exhaust nozzle to reduce jet noise, then noise levels are reduced, but drag and fuel consumption increase
Solution Approach 1:
The patent applies the dynamics principle by making the rough surface geometry changeable through an inflatable envelope system. The displaceable wall with dimples can be inflated to create a rough surface for noise reduction during takeoff and landing, then deflated during cruising to minimize drag and fuel consumption. This dynamic adaptation allows the system to optimize performance for different operational phases.
Solution Approach 2:
The patent implements parameter changes by modifying the surface roughness parameter of the exhaust nozzle. The inflatable envelope with dimples changes the surface geometry from smooth to rough, altering the boundary layer characteristics to reduce noise. This parameter change is temporary and reversible, allowing optimization of noise reduction versus fuel efficiency based on flight conditions.
2Object-affected harmful factors
If a deployable noise-reducing component is added to the exhaust nozzle, then jet noise is reduced during takeoff and landing, but device complexity increases
Solution Approach 1:
The patent applies the nested doll principle by placing the inflatable envelope within the existing exhaust nozzle structure. The envelope is positioned inside the nozzle, utilizing the existing geometric space without requiring external additions. This nested configuration reduces overall system complexity compared to external noise reduction devices.
Solution Approach 2:
The deployable nature of the inflatable envelope provides dynamic control over noise reduction capability. The system can be inflated or deflated based on flight phase requirements, allowing operators to activate noise reduction only when needed during takeoff and landing operations, rather than maintaining a permanently complex structure.
3Object-affected harmful factors
If the displaceable wall is inflated to form a rough surface, then noise reduction is active, but the structure requires additional pressure control systems
Solution Approach 1:
The inflatable envelope system utilizes self-service by leveraging existing aircraft systems for inflation and deflation. The envelope can be pressurized using existing aircraft pneumatic systems or engine bleed air, eliminating the need for dedicated pressure control equipment. This approach reduces overall system complexity while maintaining the desired noise reduction functionality.
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
Effectively reduces jet noise levels during takeoff and landing while maintaining efficiency during cruising altitudes by selectively deploying a rough surface at the exhaust nozzle, thereby addressing the noise issue without permanent deployment and its associated penalties.
Implementation Method 1
the displaceable wall being displaced from the retracted position to the deployed position when the inflatable envelope is pressurized
Implementation Method 2
form a rough surface at the loft line of the nacelle exhaust nozzle which causes a reduction in the noise level of the gas turbine engine
Implementation Method 3
The jet noise comprises turbulent mixing noise, which is at least in part caused by: a) mixing of the core and bypass flow streams; and b) mixing of the mixed stream with the ambient air creating a shear layer
Data Source
AI summary
A nacelle exhaust nozzle having a deployable noise-reducing component is described. The noise-reducing component includes an annular perforated sleeve coinciding with the inner nacelle loft line and circumscribing a mixed exhaust gas flow exiting the nacelle. The annular perforated sleeve is radially spaced apart from of a displaceable wall of an inflatable envelope that is displaceable between a deployed position, wherein noise-reduction is active, and a retracted position, wherein noise-reduction is inactive. When the inflatable envelope is pressurized, portions of the displaceable wall project through openings in the perforated sleeve and into the exhaust gas flow to form a rough surface at the loft line which causes a reduction in noise level. The portions of the displaceable wall that project through the openings in the perforated sleeve when the inflatable enveloped is pressurized include a plurality of dimples formed on the inner wall and forming the rough surface.