| 摘要 |
A fan 10 includes a hub 12, a plurality of fan blades 14 attached to the hub at one end and extending outwardly from the hub, and a ring 18 concentric with the hub and coupled to tips 16 of the blades. A dimensionless radius (r/R) is defined from a center of the hub (r/R=0) radially outwardly, wherein each tip of the blades is r/R=1. A pitch ratio increases up to about r/R=0.85, and decreases in a range of about 0.85<r/R<1.0. In the range of about 0.6<r/R<1.0, a chord length decreases continually.
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