GB997948A - Centrifugal blowers - Google Patents

Abstract

997,948. Centrifugal blowers. B. ECK. July 13, 1961, No. 25432/61. Heading F1C. In a centrifugal blower, preferably of the drum type, each blade is so bent over in the flow direction that the flow impinges on it without shock, the outer and inner peripheries of the impeller provided by the blades being cylindrical or approximately cylindrical and the interior being unobstructed and free of any blading. In the blower shown in Fig. 2, the impeller blades 4 are bent forwardly at their front ends as shown in sections A-B and E-F, and the inlet nozzle 6 of the casing is located at the outer diameter of the blades instead of the inner diameter whereby, in addition to the radial flow into the blades at the inner edges 8 there is an axial flow into the blades at their front ends. The usual cover ring closing the front ends of the blades is replaced by a cylindrical ring 7. Over their straight portions, the blades have the usual curved cross-section shown at C-D. The ring 7 may be curved outwardly as shown in Fig. 5 whereby the drag of the boundary layer produces a sharper deflection of the air. As shown, the forwardly curved front ends 9 of the blades may be separate from the straight parts 10 of the blades. The intake capacity of the impeller can be increased by providing the ring 7 with a concavity as shown in Fig. 6 and extending the inlet beyond the outer diameter of the main part of the impeller. Fig. 8 shows a blower in which the casing inlet nozzle 17 extends into an impeller shroud 18. Reinforcing rings 15, 16 are welded to the blades. In a blower with radially-shallow blades, the ring 7 may be omitted, the bent front ends of the blades then projecting axially beyond the casing into, it may be, a cylindrical suction pipe connected to the casing.