Air-Conditioning Duct End Fitting with Tubular Noise Reduction
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Solution Overview
Problem
Existing air-conditioning circuit ducts for vehicles and buildings face challenges in noise reduction due to the distance of noise-reducing devices from the compressor, leading to self-amplification of noise and high manufacturing costs, while current solutions generate significant head losses and have high production costs.
Innovation Solution
A duct structure with a tubular noise-reducing device mounted axially and radially inside a male end fitting, featuring an enlarged axial portion with a length greater than 0.6 times the nominal diameter, allowing for improved acoustic efficiency without modifying the conduit or end fitting diameters, and incorporating an annular dead volume to restrict fluid flow and enhance high-frequency attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an acoustic capacity is mounted in line in a duct between compressor and evaporator to attenuate noise, then noise attenuation is improved, but head losses increase significantly due to sudden modification of flow cross section
Solution Approach 1:
The acoustic capacity is divided into multiple perforated tubes arranged in parallel within the duct, rather than using a single large capacity. This segmentation allows the sound waves to be attenuated through multiple smaller pathways, reducing the sudden cross-section modification and associated head losses while maintaining noise attenuation effectiveness
Solution Approach 2:
The acoustic capacity uses perforated tubes with holes distributed along their length, allowing fluid to pass through while attenuating sound waves. The porous structure enables gradual flow modification rather than sudden cross-section changes, reducing head losses while maintaining acoustic performance
2Ease of manufacture
If the acoustic capacity is positioned far from the compressor due to volume constraints, then installation feasibility is improved, but noise self-amplification occurs in the resonance area between compressor and capacity
Solution Approach 1:
The acoustic capacity is transformed from a large voluminous component into a linear array of perforated tubes that can be mounted in-line within the existing duct space. This dimensional transformation allows the capacity to be positioned closer to the compressor along the duct length without requiring additional volume, thereby preventing noise self-amplification while maintaining installation feasibility
Solution Approach 2:
The multiple perforated tubes of the acoustic capacity are nested within the duct structure, utilizing the existing spatial configuration. This nesting allows the capacity to be integrated into the compact engine assembly space closer to the compressor without requiring additional external volume
3Object-affected harmful factors
If the acoustic capacity is installed in the immediate vicinity of the compressor, then noise attenuation is improved, but mechanical vibrations increase due to additional mass causing duct rupture
Solution Approach 1:
The acoustic capacity uses thin-walled perforated tubes that are flexible yet sufficient for the application. These thin-walled structures reduce the additional mass near the compressor, minimizing mechanical vibrations and duct rupture risk, while still providing effective noise attenuation through the perforated tube array configuration
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 achieves enhanced acoustic attenuation by positioning the noise-reducing device closer to the compressor, reducing noise amplification, and minimizing manufacturing costs through a more efficient design that maintains acoustic efficiency across various frequencies.
Implementation Method 1
a noise-reducing device for an air-conditioning circuit of a motor vehicle is formed of an acoustic capacity that is mounted in line in a duct of this circuit between a compressor and an evaporator, so as to attenuate the transmission of the sound waves generated primarily by the compressor and propagating in the cooling fluid inside the conduit, via a sudden enlargement of the cross section of the passage for the fluid entering this capacity
Data Source
AI summary
A duct for fluid under pressure for an air-conditioning circuit having a conduit including a male end fitting of nominal inside diameter D0 and a female end fitting connected to it in a fluid-tight manner in or in the immediate vicinity of an enlarged axial portion of inside diameter D2 of the male or the female end fitting, the female end fitting having a nominal inside diameter D0′, and a tubular noise-reducing device that is mounted inside the male end fitting and defines between an axially internal end and an axially external end of this device at least one fluid flow channel. The enlarged portion of the male or female end fitting has a length L2 such that L2≧0.6D, where D designates their common value if D0 and D0′ are equal or whichever is the lower of the values D0 and D0′ if they are not equal.