Blower Fan Noise Reduction via Half-Wavelength Sound Reflection
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Solution Overview
Problem
Conventional centrifugal blower fans in portable air-blowing machines generate significant noise due to air impingement at the narrow nose portion, requiring complex modifications that compromise performance to reduce noise levels.
Innovation Solution
A blower fan with a sound-reflecting means, such as a tray-like fan cover with a lattice framework and a blind patch, is positioned at a distance corresponding to half the wavelength of the noise from the noise source to reflect and attenuate noise waves without substantial structural changes or performance deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the configuration of blades or impeller is modified to reduce noise, then noise is reduced, but the structure becomes more complex and performance deteriorates
Solution Approach 1:
A sound-reflecting means is introduced as an intermediary component between the noise source (nose portion) and the environment. This mediator reflects noise waves back toward the source without requiring modification of the impeller or blades, thus reducing noise while maintaining simple structure and performance
Solution Approach 2:
The noise waves, which are harmful emissions, are converted into a beneficial effect by using them to illuminate or indicate the position of the sound-reflecting means through reflection. The harmful noise energy is redirected back to the source rather than being emitted to the environment
2Object-affected harmful factors
If the air intake port configuration is changed to reduce noise, then noise is reduced, but air intake efficiency and discharge capacity deteriorate
Solution Approach 1:
The sound-reflecting means acts as a mediator that addresses noise without interfering with the airflow path. By reflecting sound waves rather than modifying the air intake port geometry, the solution reduces noise while preserving air intake efficiency and discharge capacity
Solution Approach 2:
The solution segments the noise reduction function from the air intake function. The sound-reflecting means is positioned specifically to address noise while the air intake port maintains its original configuration for optimal airflow, separating these two functions to avoid performance deterioration
3Object-affected harmful factors
If a sound-reflecting means is added to minimize noise, then noise is reduced, but device complexity increases
Solution Approach 1:
The sound-reflecting means is designed to serve multiple functions: it reflects noise waves back to the source, can be integrated with the fan cover structure, and may provide additional benefits such as structural support or aesthetic purposes. This multi-functionality reduces the need for separate dedicated noise reduction components
Solution Approach 2:
Instead of modifying the original complex structures (impeller, blades, air intake port), the solution creates a simpler copy or addition (sound-reflecting means) that achieves noise reduction without replicating the complexity of the existing components
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
Effectively minimizes noise release into the environment by reflecting noise waves back to the source, reducing noise levels by at least 10 dBvr while maintaining air intake efficiency and discharge capacity, and is cost-effective with minimal modifications.
Implementation Method 1
a sound-reflecting means which is disposed to cover a portion of the air inlet port at a location which is spaced away from the nose portion by a distance corresponding to a half (1/2) of wavelength of noise in an emanating direction of noise to be minimized
Data Source
AI summary
A blower fan includes: an impeller having a predetermined number of blades; a fan casing having an air-intake port disposed to face a central portion of base of the impeller and eccentrically housing the blower fan and defining a spiral scroll passageway between an inner wall thereof and an external circumference of the impeller, the spiral scroll passageway having an inlet portion constituting a narrow nose portion and an outlet portion constituting a wide discharge port; and a driving source for rotating the impeller. In order to minimize the noise to be released from the nose portion, the blower fan further includes a sound-reflecting means which is disposed to cover a portion of the air inlet port at a location spaced away from the nose portion by a distance corresponding to ½ of wavelength of noise in an emanating direction of noise.