GB827566A - Improvements in centrifugal fluid fans - Google Patents

Abstract

827,566. Centrifugal fans. FULLER CO. Nov. 4, 1957 [Dec. 3, 1956], No. 34338/57. Class 110(1). A centrifugal fan impeller has axially-extending blades, and a channelway extending along the back of each blade, each blade forming the front wall of its channelway, the front and back walls converging outwardly, and each channelway has an inlet near the impeller hub and an outlet near its radially outer edge. Radially extending blades 17 are attached to a hub 3 and a back plate 20 which is of spider form as shown, the plate 20 comprising a single sheet or separate members welded together. A secondary blade 22 is attached to the forward face of each blade 17 and also to the back plate 20 and to an individual wall 25, and extends outwardly towards the preceding blade 17. Bearing 7 and driving motor 12 are protected from the hot gas handled by the fan by a radiation shield 35. The space between the shield 35 and the fan casing wall 6 is enclosed by a hood 33 which extends to a point beyond the bearing 7. In operation, the fan draws in hot gas at 14 and discharges it at 16, and at the same time air is drawn in through ports 27 in the back plate 20 and passes through the channels between the blades 17 and 22 to cool the fan shaft, hub and blades. Most of this air enters through a hole 36 in the shield 35, and passes over and cools the bearing 7 and shield 35, but some enters through a hole 38 in the base and helps to reduce the transmission of heat to the motor 12 and bearing 7 through the base. Air may, however, be discharged through the hole 38. Flow of air is assisted by an impeller 29, which is larger in diameter than the hole 36 to prevent radiation of heat through the hole 36. A ring 28 secured to the back plate 20 has a close clearance with a surrounding hole in the wall 6, to prevent leakage of air or gas through the hole. By adjusting the position of the impeller 29 on the shaft, the size of the annular air-flow space between the impeller and the ring 28 can be varied, thereby varying the flow of cooling air. The blades 17 may curve forwardly or rearwardly at their tips. Dispersed liquids may be introduced into the air stream, to provide evaporative cooling. In a modification, the impeller 29 and hood 33 are omitted, and the radiation shield is located close to the fan casing wall and has a central hole with a small clearance from the ring 28. In addition to the flow of cooling air into the fan through the ring 28, air flows through the aforementioned clearance and the space between the radiation shield and the fan casing wall to form a barrier against heat transmission.