| 摘要 |
PROBLEM TO BE SOLVED: To reduce the noise generated from the air current flowing on the negative pressure surface side of a blade part by forming a rough face on the negative pressure surface side of the blade part from the boss part side over an outer peripheral surface, and gradually widening a rough face formation range toward the outer peripheral side. SOLUTION: A plurality of blade parts 3 are radially formed from an outer periphery of a boss part 1. On the negative pressure surface side of the blade part 3, a rough face 4 is formed on an inner zone among three zones defined from a root part of the blade part 3 toward the outer peripheral edges on the counter rotating direction side and the rotating direction side. The rough face 4 comprises a number of irregularities like the ground glass, the sand-paper or the like. The width of the rough face 4 is widest on the outer peripheral side of the blade part 3 where a flow speed of the air current is the fastest, and the separation is easily generated, that is, by surely disturbing the air current of high speed by the rough surface 4, the separation can be inhibited, and the noise caused by the separation of the air current flowing on the outer peripheral side of highest capacity, can be surely reduced.
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