| 摘要 |
PROBLEM TO BE SOLVED: To reduce a blowing noise and to increase a fan efficiency by more effectively suppressing the separation of air flow from the inner surface of a shroud. SOLUTION: This centrifugal blower comprises an impeller 9 formed by disposing a rotatably driven hub 13 and a divergently varying shroud 14 on a same axis opposedly to each other and disposing a plurality of vanes 15, 15, etc., between the hub 13 and the shround 14. In this case, a communication port 20 for circulating air from an outer surface 14c to an inner surface 14b by a difference in pressure between the inside and oiutside of the shround 14 is provided in the shroud 14. By this, the separation of a main air flow from the inner surface 14b is suppressed by air flow circulated from the communication port 20 to the inner surface 14b side, a turbulence of air flow along the inner surface 14b resulting from the separation can be suppressed, and thus a reduction in blowing noise and an increase in fan efficiency are promoted.
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