| 摘要 |
PROBLEM TO BE SOLVED: To inhibit a reduction of discharge efficiency of an air by an impeller and a deterioration of a blowing performance and to inhibit an increase of a noise by a difference of a flow speed of an inflow air flow flowing from an air inlet port into the impeller at a circumferential position. SOLUTION: A distance L from a rotation axis of an impeller to a tip end of a bell mouth of a casing is varied so as to be gradually shortened in a rotation direction of the impeller from a throat portion 24 side L1 to an air discharge port 25 side L2 and is varied so as to be gradually lengthened from the air discharge port 25 side L2 to the throat portion 24 side L1. Thereby, a flow speed of an inflow air flow is made uniform and a blowing performance is enhanced to reduce a blowing noise.
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