| 摘要 |
PURPOSE:To reduce the generation of noise, by a method wherein a closed space part is formed at the interior of a blade, a through-hole, through which an impeller passage is communicated with the closed space part, is formed in either of two blade walls with which the closed space part is surrounded. CONSTITUTION:A closed space part 22 is formed in a blade 14 and in a range of from an approximately central part to the outer peripheral side. Pores 23, serving as a through-hole through which the closed space part 22 is communicated with an impeller passage, are formed in a blade wall 14a of two blade walls 14a and 14b with which the closed space part 22 is surrounded. Thus, energy of generated noise enters the interior of the closed space part 22 through the pores 23, and resistance and the like is repeated for damping. This constitution enables reduction of a noise level.
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