Cross-flow Fan Blade Protrusions for Flow Separation Control
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Solution Overview
Problem
Cross-flow fans experience noise generation due to flow separation phenomena at the blade surface, and existing solutions either fail to address both positive and negative pressure surfaces effectively or compromise durability and adaptability to various flow angles.
Innovation Solution
The design incorporates protrusions on both the positive and negative pressure surfaces of the blades, extending in the longitudinal direction, with varying diameters and thicknesses along the camber line, connected by a beam with decreasing thickness, to reduce flow separation and enhance durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If protrusion structure is formed on blade outer edge, then noise is reduced, but flow separation on positive pressure surface and negative pressure surface cannot be addressed
Solution Approach 1:
The blade surface is segmented into multiple regions with different protrusion structures. The first protrusions are located on the positive pressure surface while second protrusions are located on the negative pressure surface, allowing independent optimization of flow control for each surface to address flow separation effectively
Solution Approach 2:
Different protrusion structures are applied to different locations on the blade surfaces. The protrusions have varying sizes, shapes, and distributions tailored to specific regions of the positive and negative pressure surfaces, enabling localized flow separation control where needed most
2Strength
If blade thickness is changed to improve durability, then manufacturing cost increases
Solution Approach 1:
The blade thickness is not uniformly increased but is locally optimized. The protrusions are strategically positioned and sized to provide structural reinforcement only where flow separation and stress concentrations occur, maintaining durability while minimizing additional material usage and manufacturing cost
Solution Approach 2:
The blade incorporates protrusion structures that create composite-like reinforcement zones. These protrusions act as structural enhancements that improve durability through geometric reinforcement rather than simply increasing overall blade thickness, thereby controlling manufacturing costs
3Object-generated harmful factors
If protrusions are formed on both positive and negative pressure surfaces, then flow separation is reduced, but device complexity increases
Solution Approach 1:
The protrusion structures are segmented into distinct first protrusions on the positive pressure surface and second protrusions on the negative pressure surface. This segmentation allows for systematic design and manufacturing processes that manage complexity through modular construction approaches
Solution Approach 2:
The protrusion structures serve multiple functions simultaneously: they control flow separation on both surfaces, provide structural reinforcement to the blade, and can be designed with standardized geometries that simplify manufacturing. This multi-functionality reduces the need for additional separate components, managing overall device complexity
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 effectively reduces noise generation, improves blade durability, and maintains low manufacturing costs by adapting to various flow angles while minimizing changes to conventional blade specifications.
Implementation Method 1
the noise of the cross-flow fan is mainly generated near the blade. The biggest cause of noise generation near the blades is a flow separation phenomenon caused by friction with a blade surface
Data Source
AI summary
A cross-flow fan, and blades of a cross-flow fan are provided. The cross-flow fan includes a rotary shaft; a plurality of blades that extends in a direction parallel to the rotary shaft and having a positive pressure surface and a negative pressure surface; and a connector that connects the rotary shaft and the plurality of blades. At least one protrusion that protrudes in a thickness direction and extends in a longitudinal direction of the plurality of blades is formed on the plurality of blades, and by means of the at least one protrusion formed on a blade surface, a flow separation phenomenon caused by friction with the blade surface is suppressed, thereby reducing noise generated by the cross-flow fan.