Jet Engine Nozzle Projections and Flow Injection
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Solution Overview
Problem
Current aircraft engine noise reduction techniques, such as chevrons and fluid injection, do not adequately meet stringent noise certification standards, particularly for low-frequency noise and cabin noise reduction.
Innovation Solution
Jet engine nozzles with trailing edge projections (chevrons) and proximate flow injection apertures, where the second flow is injected axially aligned with and downstream of the projection tips, and can be controlled based on engine operating parameters or flight conditions, are used to enhance noise reduction by increasing vorticity and decreasing shear stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If chevrons or fluid injection are used to reduce engine exhaust noise, then noise levels decrease, but the noise reduction is insufficient to meet stringent noise certification standards
Solution Approach 1:
The patent combines two separate noise reduction techniques - chevrons (trailing edge projections) and fluid injection - into a single integrated nozzle system. The chevrons create vortex structures that enhance mixing, while simultaneously injected fluid (from apertures in the nozzle wall or chevrons themselves) further promotes turbulence and mixing. This merging of techniques produces a synergistic effect that achieves greater noise reduction than either technique alone, meeting stringent noise certification standards.
Solution Approach 2:
The nozzle employs a composite structural approach, combining solid geometric features (chevrons/projections) with fluid injection systems. The chevron structure provides a fixed geometric framework for flow separation and vortex generation, while the injected fluid (typically bypass air or exhaust gases) creates a composite flow field that enhances mixing and reduces noise. This composite approach allows optimization of both structural integrity and acoustic performance.
2Object-affected harmful factors
If chevrons are used to reduce low-frequency noise, then mixing between exhaust and freestream air improves, but further noise reduction is needed to meet community noise standards
Solution Approach 1:
The injected fluid acts as an intermediary substance that facilitates enhanced mixing between the high-speed exhaust jet and the surrounding freestream air. By introducing this intermediate fluid layer through nozzle wall apertures or chevron-mounted apertures, the system creates additional mixing interfaces that dissipate acoustic energy more effectively, particularly for low-frequency noise components that are difficult to control with chevrons alone.
3Object-affected harmful factors
If high pressure fluid jets are applied at or near the nozzle exit to reduce noise, then noise reduction is achieved, but the technique requires additional system complexity
Solution Approach 1:
The nozzle design integrates multiple functions into a single component structure. The chevron projections serve both aerodynamic purposes (flow control, mixing enhancement) and acoustic purposes (noise reduction). The fluid injection system, utilizing existing bypass air or exhaust gases, provides both cooling and noise reduction benefits. This multi-functionality reduces overall system complexity compared to separate dedicated noise reduction devices.
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 achieves significant noise reduction, exceeding the effectiveness of either chevrons or fluid injection alone, by up to 2dB in broadband noise, and can be optimized for different flight conditions to balance noise reduction and engine efficiency.
Implementation Method 1
increasing vorticity and decreasing shear stress
Implementation Method 2
increasing vorticity and decreasing shear stress
Implementation Method 3
enhance noise reduction by increasing vorticity and decreasing shear stress
Data Source
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AI summary
Jet engine nozzles with projections (e.g., chevrons) and injected flow, and associated systems and methods are disclosed. A method in accordance with one embodiment includes generating a first flow of gas with a jet engine, delivering the first flow through a nozzle having a trailing edge perimeter that includes multiple projections extending in an aft direction, and injecting a pressurized second flow of fluid into the first flow proximate to the projections. In other embodiments, other mixing enhancement devices (e.g., vortex generators) are carried by the projections. It is expected that the combination of the projections and the mixing enhancement devices will reduce engine exhaust noise levels below the levels achievable with either projections or injected flow individually.