Reversible Fan Fin Geometry for Equal Noise in Both Airflow Directions
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Solution Overview
Problem
Reversible fans often produce different noise levels when blowing air in normal and reverse directions, leading to suspicions of malfunction even when noise levels are equal, as existing designs fail to maintain equal noise levels across both directions.
Innovation Solution
The reversible fan design includes a fin with a first curved surface protruding in the normal rotation direction and a second curved surface recessed in the normal rotation direction, creating a separation space that increases noise in the normal direction while reducing noise in the reverse direction, ensuring equal noise levels by altering airflow patterns and fluid resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fin design is used in a reversible fan, then the structure is simple, but the noise levels in normal and reverse directions are unequal
Solution Approach 1:
The fin is designed with asymmetric curvature: the first curved surface (facing normal rotation direction) has a different curvature radius than the second curved surface (facing reverse rotation direction). This asymmetry creates different fluid resistance characteristics for airflow in normal versus reverse directions, enabling noise level equalization while maintaining a relatively simple single-piece fin structure
Solution Approach 2:
Different regions of the fin are given different local properties through the curved surfaces with different radii. The first curved surface region provides one fluid resistance characteristic while the second curved surface region provides another, allowing the fin to locally adapt to different airflow conditions in normal and reverse directions
2Reliability
If the fin design alters airflow patterns to equalize noise levels, then noise equality is achieved, but airflow characteristics might be affected
Solution Approach 1:
The curvature radius parameters of the fin surfaces are specifically optimized to achieve noise equalization without significantly affecting airflow characteristics. By carefully selecting the radius values (first radius different from second radius), the design changes local flow parameters to equalize noise while maintaining overall airflow performance
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 achieves equal noise levels in both directions without affecting airflow characteristics, static pressure, or power consumption, eliminating the suspicion of malfunction when noise levels are equal across both normal and reverse airflow operations.
Implementation Method 1
The fin has a shape that allows producing louder noise upon producing the current of air in the normal direction than upon producing the current of air in the reverse direction
Implementation Method 2
a separation space is formed between the second curved surface of the fin and the inner peripheral surface of the frame, the separation space being configured in such a manner that, when the impeller rotates in the reverse rotation direction, a part of the current of air in the reverse direction is separated to flow in the separation space
Data Source
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AI summary
Provided is a reversible fan including: a fin configured to produce a current of air in both of a normal direction and a reverse direction; an impeller configured to be rotatable about a rotation axis; a motor configured to rotate the impeller; and a tubular frame housing the impeller and the motor, wherein the fin has a shape that allows producing louder noise upon producing the current of air in the normal direction than upon producing the current of air in the reverse direction, and protrudes inward in a radial direction from an inner peripheral surface of the frame.