GB1020995A - Centrifugal pump - Google Patents

Abstract

1,020,995. Centrifugal pumps. SOC. NATIONALE D'ETUDE ET DE CONSTRUCTION DE MOTEURS D'AVIATION. Aug. 14, 1963 [Sept. 4, 1962], No. 32120/63. Heading F1C. A fuel pump for the reheat burner of a jet propulsion engine comprises a branch pipe 12, Fig. 5, through which, when a valve 14 is closed, fuel is directed from the inlet conduit 8 and passes via a non-return valve 13, a channel 11, an annular collector 9 and a number of passages 10 to an annular channel 10b to enter the impeller 4 through holes 10a in the front shroud 4a, whereby the pump operates at reduced flow and delivery pressure. When the valve 14 is open, the fuel enters the impeller at its eye 3 to give maximum flow and delivery pressure, back flow through the branch pipe 12 being prevented by the non-return valve 13. The non-return valve 13 may be replaced by a valve operated in unison with the valve 14. The front shroud 4a may be omitted. To provide more progressive control, a disc valve 15, Fig. 6a, having three rows of holes 17, 18, 19, may be provided in co-operation with a stationary wall 16 having ports 20. By turning the valve 15, the holes 17, 18, 19 can be brought successively into position opposite the ports 20 to provide admission to the impeller 4 at varying radial distances from the axis of the impeller. When the valve 15 is turned further, all the holes 17, 18, 19 are masked by the wall 16, and a valve similar to the valve 14 is then opened to allow flow through the inlet conduit 8 to the impeller eye. In a further modification, Fig. 10 (not shown), the admission from the annular collector 9 to the impeller 4 takes place through passages 28 which are inclined to impart to the fuel a circumferential component of flow in the direction of impeller rotation, thereby reducing shock at entry to the impeller. Some of the fluid is returned from the impeller to the collector 9 through passages 29 inclined oppositely to the passages 28, whereby the fluid is set in rotation before entry. Alternatively, fluid is returned from the volute 7 to the collector 9 through an ejector located in the collector, the outlet nozzle of the ejector being inclined in direction so as to impart a circumferential component to the flow. The passages 10 may be replaced by an annular channel or a number of annular sectors. In a further embodiment, Fig. 11 (not shown), the front and back shrouds of the impeller are of smaller diameter than the impeller periphery, so that the portions of the blades opposite the passages 10 are unshrouded and a further set of passages similar to the passages 10 may be provided behind the impeller so that fluid can enter the blades from both the front and the back. The blades may then be of curved cross-section, approximately symmetrical about the plane of rotation so as to conform to the relative velocity of the entering fluid at both sides.