Duplex Tab Exhaust Nozzle Noise Attenuation
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Solution Overview
Problem
Current noise attenuation mechanisms in turbofan gas turbine engines either increase aircraft weight, reduce engine efficiency, or are only required during takeoff, not addressing the need for effective noise reduction during cruise operations without performance loss.
Innovation Solution
The implementation of a duct with a row of vortex generating duplex tabs in the exhaust nozzle, featuring compound radial and circumferential aft inclination, to generate streamwise vortices that attenuate exhaust noise while minimizing performance loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise attenuation mechanisms are implemented, then noise reduction is achieved, but engine efficiency and performance are reduced
Solution Approach 1:
The exhaust nozzle is designed with movable tabs that can dynamically adjust their position between a first position (protruding into the exhaust flow for noise attenuation during takeoff) and a second position (retracted for maximum efficiency during cruise). This dynamic adaptability allows the system to optimize performance for different operating conditions, resolving the contradiction between noise reduction and engine efficiency.
2Object-affected harmful factors
If noise attenuation mechanisms are implemented, then noise reduction is achieved, but additional weight is added to the aircraft
Solution Approach 1:
Instead of implementing a full noise attenuation system throughout the exhaust nozzle, the invention uses localized tabs positioned at specific locations within the nozzle. These tabs provide noise attenuation functionality only where needed in the exhaust flow, minimizing the additional weight while achieving effective noise reduction during takeoff operations.
3Object-affected harmful factors
If noise attenuation is optimized for takeoff, then noise reduction is maximized, but cruise performance is compromised
Solution Approach 1:
The movable tabs can be repositioned between takeoff and cruise configurations, allowing the exhaust nozzle to be optimized for noise attenuation during takeoff while maintaining maximum aerodynamic efficiency during cruise. This dynamic reconfiguration ensures that the system performs optimally for each flight phase without compromising overall productivity.
Solution Approach 2:
The exhaust nozzle system periodically transitions between different configurations corresponding to different flight phases (takeoff with tabs extended for noise attenuation, cruise with tabs retracted for efficiency). This periodic adaptation allows the system to address noise concerns during takeoff while maintaining cruise performance, resolving the contradiction between the two operational requirements.
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 solution effectively reduces noise during takeoff while maintaining engine efficiency by promoting mixing of exhaust streams and ambient airflow, minimizing pressure losses and performance degradation.
Implementation Method 1
The tabs have compound radial and circumferential aft inclination inside the outlet for generating streamwise vortices
Implementation Method 2
generating streamwise vortices for attenuating exhaust noise
Data Source
AI summary
An exhaust nozzle includes a conical duct terminating in an annular outlet. A row of vortex generating duplex tabs are mounted in the outlet. The tabs have compound radial and circumferential aft inclination inside the outlet for generating streamwise vortices for attenuating exhaust noise while reducing performance loss.