Impeller of a centrifugal blower

Abstract

In an impeller of a centrifugal blower of the backward type having a relatively large blade inlet width as contrasted with the diameter of the impeller, blades are each shaped, as seen from the axial direction of a rotary shaft, in a concave curve with respect of rotation of the impeller, each of the blades has a larger inlet diameter on the shroud plate side than on the hub plate side, and each of the blades has a leading edge shaped, in a meridional plane, in a smooth convex curve directed radially inwardly of the impeller. By these structural features, it is possible to bring the inlet blade angle into agreement with the inlet relative flow angle at each point of the leading edge of each blade and to reduce the rate of a reduction in the velocity of flow on the shroud plate side. Thus separation of the flow from blade surfaces and production of noise caused thereby can be prevented, and a sufficiently large blade area to achieve high efficiency can be obtained, so that a loss of load on the blade surfaces can be avoided and a higher pressure coefficient than in conventional impellers can be obtained. Each blade can be developed in a plane, and its leading edge can be in the form of a circular arc centered on a side edge of the blade either on the hub plate side or on the shroud plate side. Thus the impeller is hydrodynamically advantageous and easy to fabricate.