| 摘要 |
PROBLEM TO BE SOLVED: To enhance silencing performance by increasing an enlarged angle from the intake upstream side of the impeller of a centrifugal fan toward the intake downstream side thereof. SOLUTION: The impeller 100 of a multiblade radial fan in which a plurality of radial vanes 103 is integrally connected together having intervals in a circumferential direction between a circular plate 101 and an annular plate 102, is stored in a scroll type casing 1. The scroll type casing 1 has a logarithmic spiral enlarged shape represented by formula r=ro .exp[θtan(θc +αz)] wherein r is the radius of a casing side wall measured from the center of the impeller, ro is the outside radius of the impeller,θis an angle from a datum line,θc is a standard enlarged angle = tan<-1> [(Q/S)/V], Q is the designed flow of blowing off wind of the impeller of a centrifugal fan, S is the outlet area of the impeller of the centrifugal fan, V is the designed circumferential speed of the periphery of the impeller of the centrifugal fan,αis a constant and z is a coordinate in a height direction in which a center in the height direction of the impeller is recognized as a cardinal point.
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