Patent GB-802154-A (GB)
Title: Liquid flow delivery system
Inventor: JACOBSON JOHN WILLIAM
IPC: F04D15/00
Filed: 1955-02-02
Abstract: 802,154. Centrifugal pumps. GENERAL ELECTRIC CO. Feb. 2, 1955, No. 3100/55. Class 110 (1). [Also in Group XXIX] A pump discharges through a valve for dividing the flow between an orifice connected to the low pressure side of the pump and an orifice connected to a throttle valve leading to a consumer, and pressure-sensing lines are connected respectively to the inlet and outlet of the throttle valve and to the respective ends of the flow-dividing valve for controlling the latter to maintain a predetermined pressure across the throttle valve, so that the volume of liquid delivered by the throttle valve is always substantially proportional to the size of its discharge orifice. A centrifugal pump 12 is driven by a turbine 10 which is operated by compressed gas supplied from a pressure vessel by way of a valve 27 which is biased by a spring 28 into the closed position and opened by a solenoid 29. The pump delivers liquid by way of a pipe 14, a valve 15, a pipe 17 and a throttle valve 18 to a discharge pipe 19. A solenoid-actuated valve 52 may be provided to give a positive shut-off. The throttle valve 18 is adjusted, either manually or automatically, by means of an electric motor 20 which drives a cam 25. The piston 42 of valve 15 has lands 43 and 44 which control the flow of liquid from the pipe 14 to a by-pass pipe 16 and to the pipe 17, respectively. The pressures at the inlet and outlet of the throttle valve 18 are communicated, through pipes 50 and 49 respectively, to opposite ends of the piston 42, the latter taking up a position determined by the difference between these pressures (i.e. the pressure drop across the throttle valve 18) acting in opposition to a spring 45. The position of the piston 42 determines the ratio in which the pump discharge is divided between the pipe 17 and the by-pass pipe 16, the effect of the arrangement being to maintain a substantially constant pressure drop across the throttle valve 18. An adjustable needle valve 51 may be provided in the pipe 49 to prevent too rapid displacement of the piston 42. The return of liquid through the by-pass pipe 16 ensures that under low load conditions there is sufficient flow through the pump to prevent overspeeding, instability or excessive pressure. Preferably, the cut-out portion of the valve bore 41 adjacent the land 43 is smaller in area than the cut-out portion adjacent the land 44 so that the pump discharge pressure is maintained at the maximum permissible value, regardless of the position of the piston 42, under conditions of maximum input of motive fluid to the turbine 10, to prevent overspeeding. A by-pass valve 54, which communicates through pipes 60 and 57 with the suction and discharge of the pump, opens against the action of a spring 56 in the event of excessive pressure across the pump, thereby relieving the pressure in pipe 49 through pipes 60 and 16 and causing the piston 42 to move to the left to increase the flow through the by-pass pipe 16 and decrease the flow through the pipe 17. A pipe 61 and a bore 62 in the piston of the throttle valve 18 are provided for the discharge of liquid leaking past the lands of the piston.