| 摘要 |
An axial flow fan has a hub and plural blades. Each blade extends from hub to a blade support ring and has a pitch which decreases over a first inner part of the radial extent and increases over a second outer part of the radial extent.In a preferred embodiment, the trailing edge of the blade tip and the median point of the blade root are situated on a common radial line. In a further preferred embodiment, a median point on the tip chord of the blade is disposed angularly ahead of a median point of the root chord.The fan provides improved noise performance.
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