Axial Fan Blade Local Angle-Decrease Section for Noise Reduction
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Solution Overview
Problem
Existing axial flow fans experience decreased efficiency and increased noise due to air current collisions with blade edge eddies, which form at the suction surface of the blades, leading to pressure fluctuations and power consumption issues.
Innovation Solution
The axial flow fan design incorporates backward-tilted blades with an outer circumference reflexed portion and a local angle-decrease section at the leading edge, where the blade inlet angle decreases from the inner to the outer circumferential edge, stabilizing the main air current flow and reducing eddy formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If backward-tilted blades with outer circumference reflexed portions are used, then noise is reduced and efficiency is improved, but blade edge eddies form at the suction surface causing air current collision and decreased performance
Solution Approach 1:
The blade inlet angle is designed to locally decrease at the leading edge portion closer to the outer circumferential edge, creating a specific geometric feature (local angle-decrease section) that modifies flow characteristics only in the critical region where blade edge eddies form, rather than changing the entire blade geometry
Solution Approach 2:
The blade inlet angle parameter is specifically modified in the local angle-decrease section, where the angle decreases from the inner circumferential edge toward the outer circumferential edge, changing the flow direction and velocity distribution to prevent collision with blade edge eddies
2Loss of energy
If the blade inlet angle is decreased at the leading edge, then air current flows smoothly over the blade edge eddy, but the blade geometry becomes more complex
Solution Approach 1:
The blade leading edge is segmented into different radial zones: an inner circumferential edge portion and an outer circumferential edge portion, with the local angle-decrease section applied only to the outer portion. This segmentation allows the complex geometry to be applied only where needed (at the outer edge where blade edge eddies form) rather than throughout the entire blade
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 noise and increases efficiency by ensuring the main air current flows smoothly over the blade edge eddy, minimizing pressure loss and power consumption.
Implementation Method 1
an air current flows at the outer circumferential edge side of the blade from a pressure surface of the blade to a suction surface of the blade, thereby generating a spiral blade edge eddy
Implementation Method 2
the local angle-decrease section having, at a leading edge of the local angle-decrease section, a minimum point at which the blade inlet angle is a minimum, the local angle-decrease section having an intermediate point located at an intermediate position between both ends of the local angle-decrease section, the minimum point being formed closer to a rotation axis than the intermediate point
Data Source
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AI summary
An axial flow fan according to the present invention includes a plurality of blades, each of the blades including: a leading edge formed in front in a direction of rotation of the axial flow fan; an inner circumferential edge formed at an inner circumference of the blades; and an outer circumferential edge formed at an outer circumference of the blades, the outer circumferential edge configured to be at downstream of a fluid, forced to move by the axial flow fan, than the inner circumferential edge, the blade being reflexed toward upstream of the fluid at a portion adjacent to the outer circumferential edge, and having a local angle-decrease section having a blade inlet angle α at the leading edge decreasing from neighborhood, the local angle-decrease section being formed at a side of the leading edge and being located closer to the outer circumferential edge than to the inner circumferential edge.