Fan Air Supply Duct Structure for Broad-Band Noise Reduction
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Solution Overview
Problem
Conventional air supply ducts for fans in combustion devices do not effectively reduce noise, as existing resonance-type silencers often fail to achieve optimal noise reduction across a wide frequency range.
Innovation Solution
The air supply duct incorporates a space portion surrounding the air supply port with a wider width in the y direction, allowing for the generation of standing waves with different wavelengths, which cancel noise vibrations, and is arranged near the fan to enhance noise reduction, with a preferred aspect ratio of 15% to 35% and a configuration that includes a first and second region protruding in the y direction to generate multiple standing waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a cavity portion constituting a resonance type silencer is arranged in an air supply duct for fan, then noise at a specific resonance frequency can be reduced, but the noise reduction effect is limited and cannot be achieved across a wide frequency range
Solution Approach 1:
The invention transitions from a one-dimensional cavity resonance approach to a three-dimensional space portion where standing waves can form in multiple directions (x-direction along air passage and y-direction perpendicular to it). This dimensional expansion allows generation of multiple standing waves with different wavelengths, thereby broadening the noise reduction frequency range.
Solution Approach 2:
The space portion is divided into multiple regions (first region and second region protruding in y-direction) that can generate different standing waves. Each region acts as an independent noise cancellation zone, collectively covering a broader frequency spectrum.
2Object-affected harmful factors
If the space portion is made wider in the y direction to generate multiple standing waves, then the noise reduction frequency range is widened, but the duct size increases
Solution Approach 1:
The space portion is nested within the existing duct structure, utilizing the available internal volume efficiently. The first and second regions protrude into the duct space rather than expanding the overall duct dimensions, allowing multiple standing waves to form within the constrained cross-sectional area.
Solution Approach 2:
Instead of uniformly increasing the duct cross-section, the invention creates localized protrusions in the y-direction within the existing duct volume. This allows generation of multiple standing waves without significantly increasing the overall duct area.
3Object-affected harmful factors
If the space portion is arranged near the fan which is a noise source, then the noise reduction effect is enhanced, but the available space for arrangement is limited
Solution Approach 1:
The space portion is nested at the air supply port of the fan, utilizing the existing structural space near the noise source. This positioning maximizes the noise reduction effect at the source while fitting within the limited available space in the combustion device.
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
This configuration effectively reduces noise across a broader frequency range by diffusing sound pressure and attenuating sound energy, providing a more significant noise reduction effect without increasing the duct size, and can be optimized to target the frequency range with the highest sound pressure.
Implementation Method 1
the air column vibration is generated in the space portion, and thereby a standing wave having a phase opposite to the noise is generated, and the noise can be canceled
Implementation Method 2
configured as a space portion capable of generating air column vibration
Implementation Method 3
the sound pressure is diffused in the space portion, and an effect of attenuating the sound energy can also be obtained
Implementation Method 4
an effect of attenuating the sound energy can also be obtained
Data Source
AI summary
An air supply duct for fan is used to guide air to an air intake port of a fan, and includes a duct main body portion in which an air passage extending in a predetermined x direction with one end side set as an air inlet port is formed inside, and an air supply port for supplying air travelling through the air passage to the air intake port of the fan is arranged. A peripheral region of the air supply port of the inside of the duct main body portion is surrounded by wall portions in the periphery except for a communication portion with the air passage, and is configured as a space portion for generating air column vibration and having a width in a y direction intersecting the x direction larger than a width of the air passage. A combustion device including the air supply duct is provided.