Asymmetric Axial Fan Impeller Blade Design for Reverse Rotation
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Solution Overview
Problem
Axial flow fans experience significant deterioration in air flow characteristics when rotated in reverse direction, which is a limitation for applications requiring high air flow in normal rotation direction.
Innovation Solution
The impeller design features blades with line-symmetric leading and trailing edges, where one face is a concave arc shape and the other face is a convex arc shape, maintaining air flow characteristics in normal rotation while minimizing deterioration in reverse rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the blade shape is bent with respect to the rotation direction to increase air flow in normal rotation direction, then the air flow characteristic in normal rotation direction is improved, but the air flow characteristic deteriorates significantly when rotating in reverse direction
Solution Approach 1:
The blade cross-section is designed with asymmetric curvature where the pressure surface has a different curvature radius than the suction surface. Specifically, the pressure surface has a larger curvature radius than the suction surface, creating an asymmetric airfoil shape that maintains effective air flow characteristics in the normal rotation direction while reducing the deterioration effect in reverse rotation direction.
Solution Approach 2:
The patent optimizes specific geometric parameters of the blade cross-section, including the curvature radius of the pressure surface (R1), curvature radius of the suction surface (R2), and the thickness distribution. By carefully selecting these parameters within specific ranges, the blade achieves high air flow efficiency in normal rotation while maintaining acceptable performance in reverse rotation.
2Adaptability or versatility
If the blade shape is made S-shaped with point symmetry to achieve same air flow characteristic in both directions, then the adaptability for dual-direction rotation is improved, but the air flow characteristic in normal rotation direction deteriorates
Solution Approach 1:
Instead of using symmetric S-shaped blades, the patent employs asymmetric airfoil cross-sections where the pressure surface and suction surface have different curvature characteristics. This asymmetric design allows the blade to maintain high efficiency in the primary (normal) rotation direction while accepting reduced but not symmetric performance in reverse rotation, thereby resolving the contradiction between optimizing for one direction versus equal performance in both directions.
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 maintains high air flow rates in normal rotation and achieves up to 90% of the air flow rate during reverse rotation, optimizing blade shape for dual-direction functionality.
Implementation Method 1
The blade shape is bent with respect to a rotation direction (normal rotation direction) such that a pressure surface side becomes a concave surface
Implementation Method 2
in a case of rotating the axial flow fan in the reverse direction, the air flow characteristic is significantly deteriorated as compared to the case of the normal rotation direction
Data Source
AI summary
There is provided an impeller for an axial flow fan, which includes a plurality of blades arranged in a circumferential direction. In each of the blades, with respect to a center point of a chord length of the blade, a leading edge side shape of the blade and a trailing edge side shape of the blade are line-symmetric, and a shape of the blade at one face side is different from a shape of the blade at the other face side.