Aircraft Nozzle Guiding Devices for Jet Noise Reduction
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Solution Overview
Problem
Current nozzles used in aircraft engines and process engineering systems fail to adequately reduce jet noise during take-off while minimizing aerodynamic losses.
Innovation Solution
A nozzle design featuring alternating nozzle-like and diffuser-like guiding devices with varying axial lengths and oblique trailing edges, which create a higher spatial variance in swirl intensity vectors, reducing the intensity of coherent swirl structures and noise generation without increasing high-frequency noise or adding moving parts, energy supply, or control devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional guiding elements are used to reduce jet noise, then noise reduction is achieved, but aerodynamic losses increase
Solution Approach 1:
The guiding elements are segmented into multiple types (nozzle-like and diffuser-like) with different geometries arranged alternately around the nozzle rim. Each segment has specific guide walls and edges configured to generate swirls with different characteristics, allowing selective noise reduction while preserving aerodynamic efficiency through optimized local flow control
Solution Approach 2:
Different regions of the nozzle rim are assigned different guiding element configurations. The first guiding elements have first azimuthal guide walls with first trailing edges, while the second guiding elements have second azimuthal guide walls with second trailing edges. This local differentiation creates spatially varying swirl intensities that target specific noise frequencies without uniformly increasing aerodynamic losses across the entire nozzle exit
2Ease of manufacture
If guiding elements with uniform trailing edges are used, then manufacturing is simplified, but noise reduction effectiveness is limited
Solution Approach 1:
The guiding elements incorporate asymmetric trailing edge configurations where the first and second azimuthal guide walls have different axial lengths, creating oblique trailing edges that are not symmetric with respect to the nozzle axis. This asymmetry generates higher spatial variance in swirl intensity vectors, effectively breaking up coherent swirl structures and reducing noise, while the overall modular design maintains 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
The design efficiently reduces low-frequency noise while maintaining low flow losses, is sturdy, weight-neutral, and requires minimal maintenance, effectively breaking down large swirl structures into smaller ones for improved noise reduction.
Implementation Method 1
The guiding elements impart a swirl to the outflowing medium at the nozzle rim where the outflowing medium meets the surrounding medium
Implementation Method 2
These effect a higher spatial variance in the direction of the swirl intensity vector for the outgoing swirls, thus leading to a reduction in the intensity of the large, stable and coherent swirls
Data Source
AI summary
A nozzle has a nozzle surface area and a nozzle rim, on which first and second guiding devices are alternatingly provided in the circumferential direction, where the first guiding devices are of the nozzle-type design and the second guiding devices are of the diffuser-type design. The first guiding devices each have a first azimuthal guide wall and two wall elements. The second guiding devices each have a second azimuthal guide wall and two wall elements. A wall element connects a first guiding device and a second guiding device. At least some of the first azimuthal guide walls of the first guiding device and at least some of the second azimuthal guide walls of the second guiding device have differing axial lengths, so that first and second trailing edges thereof have differing axial positions.