GB1077291A - Liquid fuel supply system, for example, for gas turbine engines - Google Patents

Abstract

1,077,291. Supplying liquid fuel to burners. DOWTY FUEL SYSTEMS Ltd. Jan. 6, 1965 [Jan. 9, 1964], No. 1063/64. Heading F4T. [Also in Division F1] In a fuel supply system for burner means, for example a fuel .supply system of a gas turbine engine, including a delivery conduit arranged to supply liquid fuel from a pressure source to the burner means, valve means are provided which are operable to divert the fuel flow in the delivery conduit from the burner means to a low pressure part of the system through a jet pump having a suction zone in which a reduction of pressure is established by that flow, there being a suction conduit extending from the burner means to the suction zone, and second valve means which close the suction conduit until the first valve is operated to divert fuel flow from the burner means to the jet pump. In a first embodiment, fuel supplied by pump 11 passes through line 13 to shut-off valve 14, the fuel normally passing through the valve to the line 15 in which is disposed a minimum pressure valve 16 and non-return valve 17 to the fuel manifold 18, the fuel then passing through line 19 and non-return valve 21 to the fuel burners (not shown) which may be of the spill type. A device 32 is provided which includes a jet pump 33, 41 whereby when the shut-off valve 14 is moved to the closed position, fuel in the burner line 19 is passed through the lines 39 and 44 back to the low pressure side of the system. The shut-off valve 14 comprises a sleeve 23 having ports 24, 25, 26 and an axially movable spool valve 27 having lands 29, 31. In the open position shown fuel in line 13 passes through ports 24, 25 to the line 15, the port 26 being closed off by the land 31. Upon shutdown, the valve spool is moved so that land 29 closes off port 25 while land 31 moves to open port 26 so that fuel from line 13 now passes through line 22 to the nozzle 33 of the jet pump so that a region of reduced pressure is created in the suction zone 41. The device 32 comprises also a timing valve which consists of a sleeve 35 having ports 37, 38 also a spool valve 36 having lands 46, 47, and a leak orifice 43. In the normal position shown, the spool valve is urged to the right by means of the spring 45 so that the land 47 covers the port 38. When the valve 14 is moved to the shut-off position and fuel under pressure passes to line 22, the fuel pressure acts through line 34 on the right-hand end of the spool valve 36 which therefore moves to the left causing the land 47 to open the port 38. Fuel in the line 19 now passes through line 39 and ports 37, 38 to the suction zone 41 of the jet pump and it is then discharged through line 44 to a low pressure part of the system. The spool valve continues to move to the left, the rate of movement being controlled by flow of fuel through the orifice 43. When the land 46 covers the port 37 flow of fuel through the line 39 ceases. A pressure relief valve 48 is provided to limit pressure in the line 22. In a second embodiment, Fig. 2, the fuel pressure in line 13 always acts through line 22 on the righthand end of the spool valve 36, also through line 67 and restricted orifice 43 on the left-hand end of the spool valve 36. When the spool valve 57 of the shut-off valve 51 is moved upwardly from the normal position shown to the shut-off position, the fuel pressure acting on the lefthand end of the spool valve 36 is communicated through orifice 43 and line 67 through the ducts 63 and 62 in the spool valve 57 to a chamber 59 connected to low pressure. The spool valve is therefore immediately moved to the left so that land 46 of spool valve 36 uncovers port 66 and high pressure fuel in line 22 passes to the nozzle 33 of jet pump, also to the pressure relief valve 48, and land 47 of spool valve 36 uncovers port 38 so that fuel in the burner line 19 now passes through line 39, ports 37 and 38 to the suction zone 41 of the jet pump and is then discharged through line 44. The spool valve 36 continues to move to the left, the rate of movement being controlled by fuel flow through the restriction 43, until the land 46 blocks the port 37.