Cross-Flow Fan Blade Geometry for Lower Turbulence and Power Loss
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Solution Overview
Problem
Cross flow fans experience increased power loss and turbulence due to significant changes in air flow speed and flow path width between blades, leading to inefficient blowing performance.
Innovation Solution
The cross flow fan design features blades with a gradual decrease in flow path width from the inner to the outer peripheral side, achieved by positioning inner peripheral side arcs on the inner side and outer peripheral side arcs on the outer side of the support plate, with a maximum thickness region between 40% to 60% from the inner side, and pressure surface arcs with radii greater than suction surface arcs, reducing the change in air speed and turbulence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a blade with crescent cross-section is used, then the blade structure is simple and symmetric, but the flow path width decreases significantly from inner to outer peripheral side, causing greater air flow speed change and turbulence
Solution Approach 1:
The blade cross-section is designed with asymmetric thickness distribution where the inner peripheral side is thicker and the outer peripheral side is thinner. This asymmetric configuration maintains structural simplicity while controlling the flow path width variation, reducing air flow speed changes and turbulence, thereby decreasing power loss caused by the fan.
2Ease of manufacture
If the flow path width decreases significantly from inner to outer peripheral side, then the blade design is straightforward, but air flow turbulence increases and flow separation occurs on outlet side suction surfaces
Solution Approach 1:
The blade thickness is locally optimized with different thicknesses at different radial positions. The inner peripheral side maintains greater thickness for structural integrity, while the outer peripheral side has reduced thickness to control flow path width. This local quality variation ensures stable air flow throughout the blade passage, preventing flow separation and maintaining reliability.
3Loss of energy
If the change in air flow speed from inner to outer peripheral side is reduced, then power loss decreases, but the flow path width must be carefully controlled
Solution Approach 1:
The blade cross-sectional parameters are optimized by setting the inner peripheral side thickness to 0.05D to 0.15D and the outer peripheral side thickness to 0.02D to 0.06D, where D is the fan outer diameter. These parameter changes control the flow path width variation within 10% to 50%, reducing air flow speed changes and power loss while maintaining manufacturability.
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 reduces air flow turbulence and power loss by minimizing the change in air speed across the fan, resulting in improved blowing performance and reduced motor input.
Implementation Method 1
flow separation occurs on the outlet side suction surfaces
Implementation Method 2
air flow turbulence becomes greater
Data Source
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AI summary
The present invention provides a cross flow fan that suppresses a reduction in flow path width between plural blades and in which there is little power loss caused by the fan. A cross flow fan 10 is equipped with a circular support plate 50 and plural blades 100. A radius rp of a pressure surface arc Rp of each of the blades 100 is greater than a radius rs of a suction surface arc Rs, and a radius ri of an inner peripheral side arc Ri is greater than a radius ro of an outer peripheral side arc Ro. Furthermore, a region of maximum thickness of the blade is located in a position 40% to 60% from the inner peripheral side arc Ri in a lengthwise direction. The blades 100 are disposed in such a way that the inner peripheral side arcs Ri are positioned on an inner peripheral side of the support plate and the outer peripheral side arcs Ro are positioned on an outer peripheral side of the support plate, and the blades have a structure wherein a flow path width between the plural blades gradually decreases from the inner peripheral side toward the outer peripheral side of the support plate.