| 摘要 |
A leading edge of a rotating blade of an impeller is formed in an arc recessed in a direction opposite to a rotating direction of the impeller. An angle where an extended line of the recessed arc of the leading edge meets another extended line of a curve of a side edge is set in an acute angle of 30 to 37 degrees in a front view so that a leading tip of the rotating blade may be projected in the rotating direction. An opening angle of a suction-side slant portion of a venturi casing is set in the range of 12 to 17 degrees and an opening angle of a discharge-side slant portion is set in the range of 30 to 35 degrees. |
