| 摘要 |
PROBLEM TO BE SOLVED: To provide a centrifugal fan free of risks that the flow of the fluid in logarithmic spiral shape in a passage formed between the outer edge of the fan and the casing side wall has a local turbulence, noise is generated due to turbulence, and that the wind quantity declines. SOLUTION: The centrifugal fan is composed of a fan 213B, a drive device to drive the fan 213B, and a fan casing to accommodate the fan 213B and formed from a logarithmic spiral shaped portion 213g and a straight shaped portion 213h stretching therefrom 213g in the tangential direction, wherein the corner R of the straight portion 213h is rounded continuously with a circular arc enlarging gradually from the connection part with the spiral portion 213g toward the outlet 213b, so that the width of the passage formed between the outer edge of the fan 213B and the casing side wall in the straight portion 213h does not enlarge any locally. Accordingly the flow of the fluid in the passage formed between the outer edge of the fan 213B and the casing side wall will have no local turbulence.
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