Pylon Microjet Nozzles for Jet Engine Noise Reduction
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Solution Overview
Problem
Current jet engine noise reduction methods, such as pyramidal bodies and nozzle adjustments, fail to effectively reduce noise generated by the interaction of core and bypass streams with ambient air streams at the pylon, leading to increased noise and reduced thrust during cruising.
Innovation Solution
A jet propulsion system with a noise reducing device featuring microjet nozzles and pylon-caused noise reducing nozzles that inject compressed air from the compressor into the noise generation sources, specifically the mixing layer formed by the core and ambient air streams, to disperse turbulence and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pyramidal bodies are permanently fixed to the cylindrical partition wall to guide core stream and bypass stream in different directions, then noise from merging streams is reduced, but thrust during cruising is reduced due to excessive mixing
Solution Approach 1:
The invention replaces permanently fixed pyramidal bodies with adjustable nozzles that can change their flow guidance characteristics. The nozzles are positioned on the cylindrical partition wall and can be adjusted to provide flow guidance during takeoff when noise reduction is prioritized, while allowing more direct flow paths during cruising to maintain thrust efficiency.
Solution Approach 2:
The invention changes the flow parameters (direction, velocity distribution) of core and bypass streams dynamically through adjustable nozzle configurations. By modifying the nozzle angles or positions, the system can optimize the mixing characteristics at different operating phases, reducing noise during takeoff while maintaining thrust during cruising.
2Object-affected harmful factors
If nozzles are arranged on the cylindrical partition wall to inject air toward the merging portion of core stream and bypass stream, then the mixture state is adjusted, but noise from the pylon region (interaction of core stream, bypass stream, and ambient air) is not reduced
Solution Approach 1:
The invention designs the noise reduction system to handle multiple noise sources simultaneously. The nozzles are configured to address both the merging noise from core and bypass streams and the pylon region noise from interaction with ambient air. The system can be adjusted to provide effective noise reduction across different operating conditions and locations.
Solution Approach 2:
The invention extends the noise reduction approach from the traditional two-stream merging region to include the third dimension of the pylon region where ambient air interacts with core and bypass streams. Additional nozzles or adjusted nozzle positions target the pylon region specifically, creating a more comprehensive three-dimensional noise reduction strategy.
3Strength
If the jet engine is connected to the wing via a pylon, then structural support is provided, but noise is generated from the interaction of core stream, bypass stream, and ambient air in the downstream region of the pylon
Solution Approach 1:
The invention introduces nozzles as intermediary devices between the engine components and the external environment. These nozzles act as mediators that control and modify the flow patterns of core and bypass streams as they interact with ambient air in the pylon region, reducing noise generation while maintaining the structural support function of the pylon.
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
The system effectively reduces noise generated by the jet engine connection to an airplane wing via a pylon by dispersing turbulence in the mixing layer, maintaining thrust during cruising and improving overall noise reduction.
Implementation Method 1
a high shearing stress region with rapid fluctuations in speed is produced in the boundary region, and thus serves as another noise generation source
Implementation Method 2
the core stream and the bypass stream are suitably mixed by the generation of a vortex
Implementation Method 3
a compressor that is configured for compressing air that, in use, is taken into the cylindrical partition wall
Implementation Method 4
the core stream and the bypass stream are suitably mixed by the generation of a vortex
Data Source
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AI summary
A noise reducing device in a jet engine that has a cylindrical casing, a cylindrical partition wall that is inserted in the casing while protruding partially from a trailing edge of the casing, and a compressor that compresses air that is taken into the cylindrical partition wall, with the inside of the cylindrical partition wall serving as a duct in which a core stream of high-speed air flows, and the space between the cylindrical partition wall and the casing serving as a duct in which a bypass stream of low-speed air flows, and being connected with a wing of an airplane by a pylon that has a projection portion that extends beyond the casing to the downstream of the core stream and the bypass stream, the noise reducing device includes a nozzle, disposed at the pylon on the downstream of the core stream, that injects a fluid toward a noise generation source that is produced from the mutual approach of an ambient air stream that is produced outside of the bypass stream and the core stream.