Centrifugal Fan Resonance Noise Absorbing Structure
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Solution Overview
Problem
Conventional centrifugal fans have a limited range of frequencies that can be suppressed, making it difficult to effectively reduce low-frequency noises without increasing the size of the outer casing, which affects noise reduction efficiency.
Innovation Solution
The centrifugal fan design incorporates a bell-mouthed orifice with a noise-absorbing structural material and a rear air layer, creating a resonance-type noise-absorbing structure that extends the path of sound waves, allowing for a broader range of frequency suppression without increasing the outer casing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the volume of resonant space is increased to suppress low-frequency noises, then the noise suppression effectiveness is improved, but the size of outer casing becomes larger
Solution Approach 1:
The patent extends the sound wave path in the resonant space by creating a winding path using reflective surfaces and structural elements. Instead of increasing the overall volume, the design makes the sound wave travel a longer distance through the existing space by reflecting off surfaces at strategic angles, effectively adding a dimensional path extension without expanding the outer casing boundaries.
Solution Approach 2:
The patent employs adjustable frequency tuning mechanisms within the resonant space that allow the noise suppression system to adapt to different frequency ranges. By dynamically adjusting the resonant characteristics through movable elements or adjustable structures, the system can suppress low-frequency noises effectively without requiring a larger fixed volume.
2Adaptability or versatility
If the range of frequencies to be suppressed is increased, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The patent divides the resonant space into multiple zones or segments, each capable of targeting specific frequency ranges. By segmenting the space and using multiple reflective surfaces or structural elements at different positions, the system can address a broader frequency spectrum without creating a single complex monolithic structure.
Solution Approach 2:
The patent designs the resonant space with multi-functional elements that serve multiple purposes. The same structural features and reflective surfaces are configured to handle different frequency ranges, allowing a single resonant space design to provide broad frequency coverage without requiring separate dedicated structures for each frequency band.
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 design enables effective suppression of noises at lower frequencies and adjusts the frequencies that can be suppressed, improving ventilation efficiency and reducing noise without enlarging the centrifugal fan's outer casing.
Implementation Method 1
Some of them are incident from inlet portion 115 having clearance distance i into resonant space 112. The incident sound waves of the noises at a frequency specified according to a volume and shape of resonant space 112 are resonated and suppressed in such a manner that air column resonance occurs in resonant space 112 and that inlet portion 115 and resonant space 112 function as a Helmholtz resonator.
Implementation Method 2
The incident sound waves of the noises at a frequency specified according to a volume and shape of resonant space 112 are resonated and suppressed in such a manner that air column resonance occurs in resonant space 112
Data Source
AI summary
A centrifugal fan used as a ventilating fan is provided which can increase a range of frequencies of noises in which noises can be suppressed and can adjust frequencies of noises at which noises can be suppressed. The centrifugal fan includes, in an outer casing, a motor that couples an impeller, a casing that surrounds a periphery of the impeller and has a bell-mouthed suction port on one side, and a bell-mouthed orifice that has an opening that is concentric with the suction port and has a diameter equal to or smaller than that of the suction port, wherein a member closing a clearance portion between an end of the orifice and the casing is a noise absorbing structural material, and a space formed by the orifice is a rear air layer, thereby forming a resonance type noise absorbing structure.