Image Number 14 for United States Patent #5813837.
An axial-flow impeller having a maximum blade width less than 20% of the impeller diameter, the pitch angle at the radial position 0.6 is 12.degree.-22.degree., the width at the tip end portion of the blade is 12-75% of the width at the radial position 0.6, the pitch angle at the tip end portion of the blade is 5.degree.-10.degree. smaller than the pitch angle at the radial position 0.6, the width at the root of the blade is 40% or more of the width at the radial position 0.6, and the pitch angle at the root of the blade is 25.degree.-50.degree.. An axial-flow impeller having a maximum width of the blade 20% or more of the impeller diameter, the radial position of the maximum width portion is 0.4-0.8, the pitch angle of the maximum width portion is 12.degree.-22.degree., the width at the tip end portion of the blade is 12-75% of the maximum width, and the pitch angle at the tip end portion of the blade is 5.degree.-10.degree. smaller than the pitch angle at the maximum width portion, the width at the root of the blade is 40-100% of the maximum width, and the pitch angle at the root of the blade is 25.degree.-50.degree..
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