Cross-Flow Fan Blade Rib Layout for Stable Low-Noise Airflow
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Solution Overview
Problem
Existing cross-flow fans face issues with noise and air blowing efficiency due to unstable flow caused by dust accumulation, rib design flaws, and turbulence, leading to backward flow and separation of air from the blade surface.
Innovation Solution
A cross-flow fan design featuring an impeller with support plates and blades divided into regions with varying blade outlet angles and a coupling portion with ribs formed on or adjacent to the coupling portion, which stabilizes airflow and reduces noise by regulating flow separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the blade outlet angle is increased in the second region (blade ring center portion) to improve air blowing efficiency, then the air blowing efficiency is improved, but the flow becomes unstable when operation state changes due to dust accumulation, causing backward flow
Solution Approach 1:
The blade is divided into three regions with different outlet angles: the first region (blade ring vicinity portion) has a smaller outlet angle, the second region (blade ring center portion) has a larger outlet angle, and the third region (inter-blade portion) has a moderate outlet angle. This local differentiation allows each region to perform its specific function optimally while maintaining overall flow stability.
Solution Approach 2:
The blade is segmented into multiple regions with distinct outlet angles to address different flow conditions. The segmentation allows the blade to handle both high-efficiency requirements in the center region and stability requirements in the vicinity portions, preventing backward flow while maintaining productivity.
2Reliability
If the rib is shaped to protrude from the blade outer peripheral end to the outside of the impeller, then the flow separation is reduced, but the workability during fan cleaning becomes unsatisfactory
Solution Approach 1:
The rib is positioned locally in the blade ring vicinity portion rather than extending to the outer peripheral end. This localized placement provides flow stabilization where needed while maintaining cleanability in the outer regions where dust accumulation occurs.
3Reliability
If the rib end portion is formed extremely thin to reduce flow separation, then the flow stability is improved, but the workability during fan cleaning becomes unsatisfactory
Solution Approach 1:
The rib is positioned in the blade ring vicinity portion where flow stabilization is most needed, rather than at the outer peripheral end. This allows the rib to have optimal thickness for flow control while keeping the outer peripheral regions accessible for cleaning operations.
4Manufacturing precision
If the upstream end portion of the rib has a flat surface to simplify manufacturing, then the manufacturing precision is improved, but the inflow current is curled up at the flat surface, disturbing the flow and deteriorating air blowing efficiency
Solution Approach 1:
The upstream end portion of the rib is formed with a curved surface instead of a flat surface. This curvature allows the inflow current to follow the rib contour smoothly without curling up, maintaining flow uniformity and preventing disturbance to the surrounding flow, thereby preserving air blowing efficiency.
5Object-affected harmful factors
If a metal-piece rib is formed extremely thin to reduce turbulence and noise, then the noise is reduced, but the workability during fan cleaning becomes unsatisfactory
Solution Approach 1:
The rib is positioned in the blade ring vicinity portion rather than extending to the outer peripheral end. This localized placement allows the rib to be sufficiently thin to reduce turbulence and noise while keeping the outer regions accessible for cleaning operations.
6Reliability
If the rib is formed to extend to the blade outer peripheral end to stabilize flow, then the flow stability is improved, but holes remain after bending the blade surface, causing turbulence and noise
Solution Approach 1:
The rib is extracted from the outer peripheral end region and positioned only in the blade ring vicinity portion. This eliminates the formation of holes at the blade outer peripheral end during bending, thereby preventing turbulence and noise while maintaining flow stability in the critical region where the rib is positioned.
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 design reduces noise and enhances air blowing efficiency by stabilizing airflow and preventing flow separation, resulting in a quieter and more energy-efficient fan operation.
Implementation Method 1
a flow is liable to separate from the blade surface, which may cause an unstable flow to increase the noise
Implementation Method 2
the turbulence of the flow passing through the hole
Data Source
AI summary
A cross-flow fan includes an impeller and a shaft. The impeller includes a plurality of support plates and a plurality of blades. The blades are different in a blade cross section orthogonal to an impeller rotational axis, and each have a plurality of regions arranged in a direction of the impeller rotational axis and a coupling portion formed so as to couple the plurality of regions to each other. A rib is formed on the coupling portion, or formed in a region adjacent to the coupling portion within a range separated away from the coupling portion by up to 20% of a length of the region adjacent to the coupling portion in the rotational axis direction.