Aircraft Air Flow Limiter Structure for Low-Noise Resistance
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Solution Overview
Problem
Conventional flow limiters in air distribution systems generate noise and turbulence, making them a nuisance and complicating integration in vehicles with limited space due to their size and weight, especially when additional sound absorbers are required to mitigate noise.
Innovation Solution
A flow limiter with a resistance element that extends axially and is partially perforated, featuring a conical shape and radial air-impermeable regions, which reduces turbulence and noise by creating a more orderly airflow, and an absorber material positioned downstream to further attenuate any remaining turbulence and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional aperture plate flow limiters are used, then flow resistance is achieved, but noise and turbulence increase significantly
Solution Approach 1:
The aperture plate is divided into multiple individual holes instead of a single opening. This segmentation creates multiple small flow paths that reduce turbulence and noise while maintaining the required flow resistance, directly resolving the contradiction between achieving flow control and minimizing harmful flow disturbances
Solution Approach 2:
The plate structure is designed with specific local characteristics including hole distribution patterns, hole shapes, and varying hole sizes across different regions of the plate. This local quality optimization allows different areas to contribute differently to flow resistance while minimizing turbulence and noise generation
2Object-generated harmful factors
If additional sound absorbers are added downstream of the aperture, then noise is reduced, but weight and radial dimensions increase
Solution Approach 1:
The noise reduction function is extracted from a separate downstream sound absorber component and integrated directly into the aperture plate structure itself. The plate design inherently minimizes noise generation through its hole configuration, eliminating the need for additional weighty sound absorber materials
Solution Approach 2:
The flow resistance function and noise reduction function are merged into a single integrated plate structure. The same plate that provides flow resistance through its hole pattern also inherently reduces noise through the same structural design, eliminating the need for separate components
3Object-generated harmful factors
If additional sound absorbers are added downstream of the aperture, then noise is reduced, but radial extension beyond the air line increases
Solution Approach 1:
The noise reduction capability is extracted from a separate downstream component and embedded within the aperture plate structure itself. This integration ensures that the noise reduction function is achieved within the existing radial boundaries of the air line connection, eliminating radial extension
Solution Approach 2:
The flow control and noise reduction functions are merged into a single compact plate structure that fits within the existing air line radial dimensions, eliminating the need for additional radial space
4Productivity
If aperture plates with abrupt cross-section changes are used, then flow resistance is achieved, but turbulent flow fields and directional air jets are created
Solution Approach 1:
The single abrupt aperture is segmented into multiple smaller holes distributed across the plate. This segmentation eliminates the abrupt cross-section change effect by distributing the flow contraction across many small openings, creating more orderly flow patterns while maintaining overall flow resistance
Solution Approach 2:
The flow resistance function is transitioned from relying on abrupt cross-sectional changes in a single direction to being achieved through the two-dimensional distribution pattern of multiple holes. This dimensional change allows flow resistance to be achieved while maintaining more uniform and orderly flow characteristics
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 solution results in a compact, low-noise, and low-turbulence flow limiter that maintains desired airflow resistance while minimizing noise generation and turbulence, allowing for easier integration in air distribution systems, particularly in aircraft where space is limited.
Implementation Method 1
The resistance element imposes a predetermined flow resistance on an air flow that extends from the air inlet to the air outlet
Implementation Method 2
no central and strongly directional air jet arises that is surrounded by turbulent flow fields. Instead, depending on the selection of the size and number of the perforation openings, a more orderly air flow is to be expected in which the turbulent portion is kept within narrow limits
Implementation Method 3
an absorber material in the form of an absorber is positioned, which absorber material attenuates any remaining turbulence that extends in an outer radial region, thus also attenuating the associated noise generation
Data Source
AI summary
A flow limiter comprises a line segment with an air inlet and an air outlet and at least one resistance element. The resistance element is positioned within the line segment and impresses a predetermined flow resistance on an air flow that extends from the air inlet to the air outlet. Preferably, the resistance element extends at least in part in an axial direction of the line segment. Such a flow limiter is used to adjust an air volume flow and comprises particularly low generation of intrinsic noise.