Parallel Fluid Jets for Aircraft Engine Noise Reduction
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Solution Overview
Problem
Existing noise reduction devices for aircraft engines, such as those described in WO2002/013243 and FR 2 892 152, lose effectiveness at larger nozzle diameters and generate parasitic noise at higher frequencies due to the interaction of converging micro-jets with the surrounding air flow.
Innovation Solution
The aircraft engine incorporates ducts around the periphery of the downstream end of the nacelle wall, each duct ejecting a fluid jet substantially parallel to others, forming a side-slip angle with the longitudinal axis, which interacts with the gas flow to generate longitudinal vortices and reduce noise by creating a fluidic screen around the ejected gas stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If converging ducts are used to generate fluid triangles, then noise reduction is achieved for small nozzle dimensions, but effectiveness is lost for large nozzle diameters (e.g., one meter)
Solution Approach 1:
The invention divides the single large nozzle flow into multiple smaller effective interaction zones by using multiple distributed ducts around the periphery. Each duct creates its own fluid triangle interaction with the main jet, effectively segmenting the large nozzle problem into multiple smaller, manageable interaction zones that collectively cover the entire jet perimeter.
Solution Approach 2:
The invention transitions from a single-point or single-line interaction approach to a distributed three-dimensional arrangement of multiple ducts around the nozzle periphery. This spatial distribution in multiple dimensions allows each duct to interact with different portions of the large jet, maintaining effectiveness across the entire nozzle diameter.
2Object-affected harmful factors
If converging micro-jets are used to generate fluid triangles, then noise reduction is achieved, but parasitic noises at higher frequencies are generated due to jet interactions
Solution Approach 1:
The invention uses the main jet flow itself as an intermediary medium between the micro-jets and the surrounding air. The micro-jets interact with the main jet to create fluid triangles, and this interaction modifies the main jet's behavior as it encounters the external air, thereby reducing noise while avoiding direct harmful interactions between the micro-jets and ambient air.
3Object-affected harmful factors
If fluid jets are ejected to interact with the propulsive jet, then noise is reduced by creating longitudinal vortices, but the jets must be precisely oriented to avoid forming fluid triangles
Solution Approach 1:
The invention segments the noise reduction function across multiple ducts with simpler individual orientations. Rather than requiring one complex duct configuration, multiple ducts with simpler, standardized orientations collectively achieve the desired effect, distributing the complexity across identical or similar modular units.
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 configuration effectively reduces noise generated by the interaction of the gas stream with the surrounding air by creating a fluidic screen that minimizes flow interactions, thereby reducing noise levels during take-off and approach phases without penalizing aerodynamic performance.
Implementation Method 1
The fluid jets perform an interaction with the propulsive jet (ejected gas flow) of a nature comparable to that of the convergent jets (described in application WO2002/013243) in the generation of longitudinal vortices
Implementation Method 2
These jets thus oriented (with a lateral incidence) are distributed on the outer periphery of the flow of gas ejected longitudinally and wrap around the latter in the manner of a helix. The jets of fluid thus generated reduce the interaction between the flow of gas ejected at the downstream end of the wall and the flow of gas (for example air) flowing at the outer periphery of the wall of the reactor
Data Source
Figure 1
Figure 2a
Figure 2b~2c
AI summary
Aircraft jet engine with a longitudinal axis (XX'), comprising a wall (30) enclosing a gas flow which is ejected from a downstream end of the wall in the longitudinal axis, several ducts (32, 34, 36, 38, 40, 42, 44, 46) being distributed around the periphery of the downstream end (30a) of the wall each comprising a terminal section, provided with an outlet opening. Each duct can eject a fluid jet through the outlet opening thereof, characterised in that the ducts are designed to eject the fluid jets essentially parallel to each other, each fluid jet ejected through the corresponding outlet opening (32b) forming a lateral angle (d) with the longitudinal axis (XX') in a projection view in a plane with the longitudinal axis.