Propeller Fan Ribs for Stagnation Reduction
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Solution Overview
Problem
The axial fan experiences significant stagnation regions around the cylindrical portion, leading to reduced air-sending efficiency due to the formation of large stagnation regions upstream and downstream of the rotation axis.
Innovation Solution
The propeller fan design incorporates first and second ribs on the pressure and negative-pressure surfaces of the blades and connection portions, which structurally reinforce the shaft and blades while aerodynamically diffusing air from stagnation regions, reducing their size and enhancing airflow efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a cylindrical portion is formed to support the shaft hole portion from the outer peripheral side, then the structural strength is improved, but large stagnation regions are formed upstream and downstream along the rotation axis, reducing air-sending efficiency
Solution Approach 1:
The cylindrical portion is segmented by introducing first ribs and second ribs that divide the stagnant air regions into multiple sections. These ribs create flow passages that guide air from the upstream stagnant region through the shaft hole portion to the downstream stagnant region, converting one large stagnant region into multiple smaller flow paths that improve overall air-sending efficiency while maintaining the structural strength provided by the cylindrical portion.
2Stability of the object's composition
If the cylindrical portion is made slightly larger than the shaft hole portion, then the support stability is improved, but stagnation regions increase in size, reducing airflow efficiency
Solution Approach 1:
The ribs are strategically positioned at specific locations where stagnation occurs most severely. The first ribs extend from the upstream end of the shaft hole portion toward the cylindrical portion, while the second ribs extend from the downstream end. This localized placement of flow-guiding structures addresses the stagnation problem in critical areas without requiring changes to the overall dimensions of the cylindrical portion, thereby maintaining support stability while improving airflow efficiency.
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
The ribs effectively reduce stagnation regions by diffusing air from the downstream region into the mainstream flow and transmitting centrifugal force to air on the upstream side, thereby improving air-sending efficiency and reducing air resistance.
Implementation Method 1
transmitting centrifugal force to air on the upstream side
Data Source
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AI summary
A propeller fan includes: a cylindrical shaft portion provided on a rotation axis of the propeller fan; a plurality of blades provided on an outer peripheral side of the shaft portion; a connection portion provided adjacent to the shaft portion and connecting two of the plurality of blades that are adjacent to each other in a circumferential direction of the propeller fan; a first rib provided on at least one of a pressure surface of each of the plurality of blades and a surface of part of the connection portion that is located on a downstream side in the flow of air, the first rib extending outwards from the shaft portion in a radial direction of the propeller fan; and a second rib provided on at least one of a negative-pressure surface of each of the plurality of blades and a surface of part of the connection portion that is located on an upstream side in the flow of air, the second rib extending outwards from the shaft portion in the radial direction.