Cross-Flow Fan Blade Geometry for Lower Turbulence 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 configuring the blades with a convex suction surface and concave pressure surface, where the radius of the pressure surface arc is greater than the suction surface arc, and the thickness decreases from the inner to the outer peripheral side, reducing the change in air speed and turbulence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a blade with crescent cross-section is used, then the blade structure is simple and easy to manufacture, 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-sectional shape is optimized locally at different positions. The outer peripheral side of the blade has a smaller thickness than the inner peripheral side, creating a non-uniform thickness distribution. This local quality variation maintains easier manufacturability while significantly reducing the flow path width decrease rate from inner to outer peripheral side, thereby stabilizing air flow and reducing turbulence.
2Shape
If the flow path width decreases significantly from inner to outer peripheral side, then the blade can be made thinner at the outer side, but this causes greater change in air flow speed and increased power loss
Solution Approach 1:
The blade thickness parameter is changed progressively from the inner peripheral side to the outer peripheral side. Instead of a sudden or linear decrease, the thickness reduces at a controlled rate, with the outer peripheral side being thinner than the inner side. This parameter optimization reduces the flow path width decrease rate to 20% or less, minimizing air flow speed changes and reducing power loss from flow separation and turbulence.
3Device complexity
If the flow path width changes greatly, then the blade design is simpler, but air flow turbulence increases and flow separation occurs on the outlet side suction surfaces
Solution Approach 1:
The blade design applies local quality optimization by making the outer peripheral side thinner than the inner peripheral side. This creates a specific thickness distribution pattern that gently guides the air flow from the inner to outer peripheral side, reducing the flow path width decrease rate. This local structural variation maintains design simplicity while preventing flow separation and improving air flow attachment reliability.
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 blades, 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
AI summary
A cross flow fan includes a support plate and an impeller with a plurality of blades disposed on the support plate at predetermined intervals. On each blade, a radius of a pressure surface arc is greater than a radius of a suction surface arc, a radius of an inner peripheral side arc is greater than a radius of an outer peripheral side arc, and a region of maximum thickness is located 40% to 60% from the inner peripheral side arc in the lengthwise direction. The blades are disposed such that the inner peripheral side arcs are positioned on an inner peripheral side of the support plate and the outer peripheral side arcs are positioned on an outer peripheral side of the support plate. A flow path width between the plurality of blades gradually decreases from the inner peripheral side toward the outer peripheral side of the support plate.