Impeller Blade Camber Layout to Limit Airflow Separation
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Solution Overview
Problem
Existing impellers experience airflow separation on blade surfaces due to convex shapes on the outer peripheral side, leading to deteriorated air-sending performance and noise during rotation.
Innovation Solution
The impeller design includes blades with a leading edge, trailing edge, outer end, and inner edge, where the maximum extreme point in chordwise-direction cross-sections is positioned closer to the trailing edge and air suction side, with at least one inflection point between the leading edge and maximum extreme point, reducing airflow separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If blades have a convex shape on the outer peripheral side to reduce noise, then noise is reduced, but airflow separation occurs leading to deteriorated air-sending performance
Solution Approach 1:
The patent applies different camber line configurations to different radial positions of the blade. Specifically, the camber line has an inflection point that divides the blade into two regions: the root portion (inner radius) with one camber configuration and the tip portion (outer radius) with another camber configuration. This local differentiation allows the root portion to contribute to air-sending performance while the tip portion controls airflow separation and noise, thus resolving the contradiction between noise reduction and air-sending performance.
2Object-generated harmful factors
If blades have a convex shape over the entire length from root to outer peripheral portion, then noise is reduced, but airflow separation occurs on the outer peripheral side leading to deteriorated air-sending performance
Solution Approach 1:
The patent introduces an inflection point on the camber line that divides the blade into root and tip portions with different camber characteristics. The root portion (from leading edge to inflection point) has a camber configuration that promotes stable airflow, while the tip portion (from inflection point to trailing edge) has a camber configuration that reduces airflow separation. This local differentiation maintains airflow stability while preventing the adverse effects of uniform convex shapes.
Solution Approach 2:
The blade camber line is segmented into two distinct regions by the inflection point: the root portion and the tip portion. Each segment is optimized independently - the root portion for airflow stability and the tip portion for separation control. This segmentation allows the blade to simultaneously achieve noise reduction and maintain reliable airflow without the adverse effects of a uniform camber configuration.
Data Source
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AI summary
In an impeller, where, in the case where imaginary cylinders concentric with a rotation axis are assumed, an imaginary cross-section of each of parts of each of blades that correspond to the imaginary cylinders is defined as a chordwise-direction cross-section; in the chordwise-direction cross-section, a straight line that connects the leading edge and the trailing edge is defined as a chord, and a central line of a cross-section of the blade is defined as a camber line; the distance between the chord and the camber line is defined as a camber height; on the camber line, a point equidistant from the leading edge and the trailing edge is defined as a camber midpoint; and a point at which the camber height is maximum is defined as a maximum extreme point, in the chordwise-direction cross-section close to the inner edge of the blade, the maximum extreme point is located closer to the trailing edge than to the camber midpoint and closer to an air suction side than to the chord, and the camber line has at least one inflection point between the leading edge and the maximum extreme point, and in the chordwise-direction cross-section close to the outer end of the blade, the maximum extreme point is located closer to the leading edge than to the camber midpoint and closer to the air suction side than to the chord.