Mixer Duct Shell Acoustic Lining for Turbofan Exhaust Noise
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Solution Overview
Problem
Conventional aircraft turbofan engines emit significant noise and heat, which can be reflected and amplified, causing disturbance to nearby communities and increasing the susceptibility of military aircraft to heat-seeking missiles.
Innovation Solution
A method involving a mixer duct shell with an acoustic lining, including a honeycomb core structure, is used to route fan exhaust between the inner and outer surfaces of the mixer duct shell, directing a portion through the core engine shroud and another over the outer surface, to absorb and dissipate noise and heat radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional aircraft engines are installed beneath the wings, then the engines can provide thrust for the aircraft, but the engine exhaust noise and heat can be reflected and amplified by the wing surfaces, causing disturbance to nearby communities and increasing susceptibility to heat-seeking missiles
Solution Approach 1:
The patent introduces a mixer duct as an intermediary component between the engine exhaust and the external environment. This mixer duct contains acoustic linings that act as mediators to absorb and attenuate both noise and heat from the exhaust gases before they are discharged, thereby reducing the harmful effects without compromising engine performance
Solution Approach 2:
The patent modifies the physical parameters of the exhaust flow by changing its temperature, velocity, and composition through the mixing process within the duct. The exhaust gases undergo parameter changes as they mix with ambient air and pass through the acoustically lined duct, transforming the harmful hot high-velocity flow into a cooler, slower, and less noisy discharge
2Object-generated harmful factors
If acoustic lining with honeycomb core structure is applied to the mixer duct, then noise radiation is absorbed and reduced, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent employs porous honeycomb core structures as acoustic linings within the mixer duct. These porous materials provide effective noise absorption through their cellular architecture, which traps and dissipates sound energy while maintaining a relatively compact and manageable duct structure
Solution Approach 2:
The acoustic lining is constructed as a composite structure combining the honeycomb core with facing layers, creating a multi-layer composite material system. This composite approach provides both acoustic absorption and structural integrity, balancing noise reduction performance with manufacturing feasibility
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 approach effectively reduces noise radiation and heat emissions, minimizing community disturbance and enhancing the aircraft's defense against heat-seeking missiles by internal mixing and cooling of exhaust gases.
Implementation Method 1
At least one of the inner surface and an outer surface of the mixer duct shell may have an acoustic lining including a honeycomb core structure
Implementation Method 2
A first portion of fan exhaust may be routed through the mixer duct shell between an inner surface of the mixer duct shell and an outer surface of a core engine shroud
Data Source
AI summary
A method of controlling plume exhaust heat and/or noise radiation from a turbofan engine assembly having a short nacelle. A mixer duct shell is supported such that a downstream edge of the short nacelle overlays an upstream portion of the mixer duct shell. A first portion of fan exhaust may be routed through the mixer duct shell between its inner surface and an outer surface of a core engine shroud. A second portion of fan exhaust may be routed over an outer surface of the mixer duct shell. At least one of the inner surface and an outer surface of the mixer duct shell may have an acoustic lining including a honeycomb core structure.