| 摘要 |
PURPOSE:To reduce noise by a method wherein an annular body, having arced curved surface, is formed at the tip end part of the fan to form a smooth air introducing path by the annular body and a suction port having the shape of bell mouth. CONSTITUTION:The annular body 4a, having the curved surface of the shape of arc, is formed at the tip end of the fan 4. The smooth air introducing path is formed by the annular body 4a and the suction port 3d of the shape of bell mouth. According to this method, when air flows from the suction port 3d of the fan case 3 into the fan case 3, the flowing air passes the suction port 4c of the fan 4 smoothly without causing any turbulence as shown by arrow signs B and, then, flows into the fan case 3 through spaces between blades 4b. Accordingly, noise may be reduced remarkably.
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