Modal Attenuator with Varying Chamber Volumes
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Solution Overview
Problem
Existing noise reduction technologies for fluid flow in process systems, such as valves and regulators, either reduce fluid flow rates or are inefficient in attenuating a broad range of acoustic frequencies, and previous solutions like modal coincidence suppression devices are heavy and difficult to assemble.
Innovation Solution
A modal attenuator with a series of chambers along its length, where the width, height, and volume of the chambers vary to effectively attenuate acoustic waves, utilizing a perforated screen to direct sound waves into the chambers, which are designed to disrupt and cancel sound waves of specific frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multi-port cages or trims are used to reduce noise, then noise is reduced, but fluid flow rates are reduced
Solution Approach 1:
The attenuator body is divided into multiple chambers (first chamber, second chamber, third chamber) with different volumes, each chamber acting as an independent noise attenuation element. This segmentation allows the device to attenuate noise across multiple frequency ranges simultaneously while maintaining overall fluid flow through the system.
Solution Approach 2:
Each chamber is designed with specific volume characteristics (first chamber with largest volume, second chamber with intermediate volume, third chamber with smallest volume) to target different acoustic frequencies. The perforated screen is strategically positioned to allow acoustic energy entry while minimizing fluid flow restriction. This local optimization of chamber properties enables effective noise reduction without compromising overall fluid flow rates.
2Object-affected harmful factors
If sound absorbing materials are disposed in the flow path, then sound waves are absorbed, but fluid flow through the material is reduced
Solution Approach 1:
The perforated screen acts as an intermediary element that selectively allows acoustic energy to pass into the chambers while presenting minimal resistance to the main fluid flow. The screen's perforations are sized and positioned to capture sound waves across a broad frequency range without creating significant pressure drop for the fluid stream, thus decoupling the noise attenuation function from fluid flow restriction.
Solution Approach 2:
The perforated screen functions as a porous structure that permits acoustic energy transmission into the chambers while maintaining high fluid flow capability. The controlled porosity of the screen allows it to interact with sound waves (enabling attenuation) while preserving the primary fluid flow path, avoiding the trade-off inherent in solid sound-absorbing materials.
3Object-affected harmful factors
If modal coincidence suppression device is used, then noise is reduced, but device weight increases and assembly difficulty increases
Solution Approach 1:
The noise suppression function is divided into multiple discrete chambers of varying volumes rather than using a single large heavy structure. This segmentation achieves broad-spectrum noise attenuation through distributed acoustic resonance in smaller chambers, reducing overall material requirements and device weight compared to traditional modal coincidence suppression devices.
Solution Approach 2:
The device uses variations in chamber volume parameters (first chamber largest, second chamber intermediate, third chamber smallest) to achieve noise attenuation across different frequencies. By optimizing the volume parameters of individual chambers rather than using a uniformly heavy structure, the device achieves effective noise suppression with reduced overall weight and simplified assembly.
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 modal attenuator effectively reduces noise across a broad range of frequencies without significantly impacting fluid flow rates, offering a lightweight and easily integratable solution for process systems.
Implementation Method 1
the widths of the chambers increase in size from a first end chamber adjacent an inlet toward an intermediate chamber... the depths of the chambers are staggered... acoustic waves passing through the perforated screen can enter into the chamber through the open end
Implementation Method 2
designed to disrupt and cancel sound waves of specific frequencies
Implementation Method 3
materials disposed in the flow path that absorb sound waves and convert the sound waves to heat energy
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A modal attenuator includes annular chambers disposed between an attenuator body and a perforated screen surrounding a primary flow path. The modal attenuator in some arrangements is in the form of an expander section. In some arrangements one or both of the height and the width of the annular chambers may vary along the length of the attenuator body such that the volumes of the chambers vary along the length of the attenuator body. Each chamber preferably has an open end facing the perforated screen such that acoustic waves passing through the perforated screen can enter into the chamber through the open end.