Cross flow fan blade, cross flow fan, and air conditioner indoor unit
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Solution Overview
Problem
Cross flow fans in air conditioner indoor units face inefficiencies due to flow separation at the negative pressure face, leading to increased energy loss, which existing designs fail to adequately address.
Innovation Solution
The cross flow fan blade design features a base part with a maximum thickness position closer to the inner edge than the outer edge, where the thickness of the inner edge is greater than 1.5 times that of the outer edge, and the ratio of maximum thickness to blade chord length is optimized between 0.054 and 0.094, to suppress flow separation and maintain a wide flow path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the maximum thickness position of the blade is set closer to the inner edge, then flow separation at the negative pressure face is suppressed, but the blade structure becomes more complex
Solution Approach 1:
The blade thickness is varied locally along its length, with the maximum thickness positioned at a specific location closer to the inner edge rather than being uniformly distributed. This local variation in thickness creates favorable pressure distribution that suppresses flow separation at the negative pressure face, reducing energy loss while maintaining a relatively simple overall blade structure.
Solution Approach 2:
The patent optimizes the blade thickness parameter by setting the maximum thickness position closer to the inner edge and specifying that the inner edge thickness exceeds 1.5 times the outer edge thickness. This parameter change modifies the flow characteristics around the blade, suppressing flow separation and reducing energy loss without requiring complex structural modifications.
2Loss of energy
If the maximum thickness to blade chord length ratio is reduced, then flow separation is suppressed, but the blade strength may be compromised
Solution Approach 1:
The blade maintains sufficient strength by concentrating thickness at the inner edge region where maximum thickness is positioned, rather than uniformly reducing thickness across the entire blade. This local quality variation ensures that critical stress-bearing areas maintain adequate thickness while the overall tmax/L ratio is reduced to suppress flow separation.
Solution Approach 2:
The blade exhibits asymmetric thickness distribution with the inner edge thickness being more than 1.5 times the outer edge thickness. This asymmetric design allows the blade to have reduced overall thickness ratio for flow separation suppression while maintaining sufficient strength at the inner edge where structural demands are highest.
3Area of stationary object
If the inner edge thickness is increased relative to the outer edge, then flow path width is maintained, but manufacturing complexity increases
Solution Approach 1:
The patent specifies a clear quantitative parameter relationship where inner edge thickness exceeds 1.5 times the outer edge thickness, providing a straightforward manufacturing guideline. This parameter specification maintains adequate flow path width while avoiding excessive manufacturing complexity by establishing a simple proportional relationship rather than requiring complex variable thickness profiles.
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 enhances energy efficiency by reducing energy loss and power consumption, while maintaining airflow efficiency and reducing noise by minimizing turbulence and flow velocity.
Implementation Method 1
reducing loss by suppressing separation of a flow at a negative pressure face
Data Source
AI summary
A cross flow fan blade includes an inner edge disposed on an inner circumferential side of a cross flow fan, an outer edge disposed on an outer circumferential side of the cross flow fan, and a base part formed between the inner edge and the outer edge. The base part has a pressure face and a negative pressure face. A thickness of the inner edge is larger than 1.5 times a thickness of the outer edge. An interval between the pressure face and the negative pressure face in a direction perpendicular to the pressure face is a thickness of the base part. A maximum thickness position of the base part is closer to the inner edge than to the outer edge. When a blade chord length is L and a maximum thickness of the base part is tmax, tmax/L≤0.094, and a range of tmax/L≤0.08 is excluded.