Patent GB-1423361-A (GB)
Title: Priming valve arrangement for liquid fuel supply system
IPC: F02C9/28
Filed: 1972-04-06
Abstract: 1423361 Gas turbine jet engines; re-heat fuel systems LUCAS INDUSTRIES Ltd 26 March 1973 [6 April 1972 21 June 1972] 15881/72 and 28999/72 Heading F1J The invention relates to fuel control apparatus for gas turbine engine re-heat systems comprising a fuel pump 10, a variable metering device 14 for controlling fuel flow from the pump to the re-heat burners 20, 21, 22 in response to operating parameters of the engine, there being means for varying the pump delivery pressure in response to the operating parameters, and a priming valve arrangement 200 in parallel with the metering device, the valve arrangement including a control member 201, Fig. 7, movable in response to an increase in the pump delivery pressure PP first to open and then to close the valve arrangement and thereby to deliver a charge of fuel to the re-heat burners. The apparatus is shown generally in Fig. 1, the fuel pump 10 being of the vapour core type, flow of which is controlled by a throttle valve 11 which moves in response to servo-pressures PS1, PS2 applied through lines 12, 13. Fuel passes from the pump through line 15 to the variable metering apparatus 14 and through line 205 to the priming valve arrangement 200 disposed in parallel flow with the metering apparatus 14. Priming fuel passes through lines 215, 216, 217 and thence through inlets 132, 133, 134 to the distributer 130, then passing through outlets 135, 136, 137 to the primary, gutter and colander re-heat burners 20, 21, 22 to prime them; subsequently fuel passes from the priming valve 200 through line 221 to a hot-shot ignition device 222 thence to the re-heat igniter burners 223, 224 in the main combustion section and downstream of the turbine. Fuel then passes through the metering assembly 14 through lines 84, 76a, 78a and inlets 132, 133, 134, to the distributer 130, thence through lines 135, 136, 137 to the re-heat burners 20, 21, 22. The apparatus comprises also a pressure control arrangement 81, and a valve arrangement 90 which is movable between positions A to F, that is from re-heat off to re-heat maximum. The variable metering assembly 14 is shown in Fig. 2 and comprises a fuel inlet 15 from the pump 10, three metering devices 17, 18, 19 from which fuel is delivered through outlets 84, 76a, 78a at pressures PF1, PF2, PF3 to the distributer 130. The assembly comprises also a three-dimensional cam 23 mounted on a shaft 24 which is movable axially by a servosystem in dependence on compressor intake and discharge pressures P1, P2, and rotationally through a rack and pinion assembly 43, 42 by a servosystem in dependence on compressor intake temperature T 1 , the rack 43 being formed in a piston member 44 movable axially by servo-pressures applied at the ends thereof. The cam 23 is engaged by three cam followers such as 69, the cam follower 69 controlling the axial position of a piston member 62 of the metering device 17 by a servosystem. The piston 62 is formed with an orifice 63 which co-operates with an orifice 61 in the sleeve 60 to define a metering orifice whereby flow of fuel from inlet 15 to the outlet 84 at pressure PF1 is controlled. Flow of fuel to the outlets 76a and 78a at pressures PF2 and PF3 is controlled by similar metering devices 18, 19 having metering valves 70, 71. The pressures downstream of the metering orifices of the devices 17, 18, 19 namely DP1, DP2, DP3, are tapped off as indicated and are utilized in the pressure control arrangement 81. The metering assembly comprises also a shaft 73 carrying an edge cam 72, the angular position of the shaft 73 being controlled in dependence on angle # of power demand control by means of a servopiston assembly 75 and rack and pinion assembly 74, the shaft 73 controlling the valve assembly 90. Followers 72a on the control members 70, 71 engage the edge cam 72 so that the rotational positions of the members 70, 71 is dependent on angle # of the power demand control. Pressurizing valves 82, 76, 78 are associated with the metering devices 17, 18, 19 being loaded by pressures S1, S2, S3, pressure S1 being derived from a shuttle valve arrangement 120, and pressures S2, S3 being derived from the pressure control arrangement 81. The arrangement 81 is shown in Fig. 3 and comprises three spool valves 86, 101, 111 which are rotated by gearing 100, a centrifugal governor 87 also being driven by the gearing. Pump discharge pressure PP is applied to the spool valves, pressure DP1, the pressure downstream of metering device 17, is applied to the left hand side of all three valve spools, pressure DP2, the pressure downstream of metering device 18, is applied to the right-hand side of valve spool 101, and pressure DP3, the pressure downstream of metering device 19 is applied to the right-hand side of valve spool 111, the pressures S2 and S3 being derived as shown and transmitted to the pressurizing valves 76, 78 respectively. Pressure S applied to pressurizing valve 82 is derived from the shuttle valve arrangement 120, Fig 4 comprising a pair of shuttle ball members 123, 124; pressures PF2, PF3 and PR are applied as shown, the output pressure S1 being the greatest of these three pressures; pressures PF2 and PF3 are the fuel pressures downstream of the pressurizing valves 76 and 78 and pressure PR is the pressure within the chamber 41 and derived from the control unit 26, 29, 31 and communicated to the chamber 41 through the bore 40 through shaft 24. The output pressure PP of the pump 10 is controlled so as to maintain DPI constant; the system 81 acts to maintain pressure DP2 equal to DPI, also DP3 equal to DPI. The distributer valve arrangement 130 is shown in Fig. 5 and comprises three inlets 132, 133, 134 receiving the flows PF1, PF2, PF3 from the metering devices 17, 18, 19 of the assembly 14; the associated outlets 135, 136, 137 communicate with re-heat pilot, gutter and colander burners respectively. The valve 140 associated with the inlet 134 and outlet 137 comprises a dumb-bell type valve member 146 the valve member 147 being urged against seat 144 so as to close off the outlet 137 from the inlet 134, the outlet being connected through the open valve 148 to the passage 141 which is connected through clump valve 142 to low-pressure. Application of pressure PS3 through duct 198 on the piston 150 causes movement of the valve member 146 to the left so the left so that the valve 147 opens and valve 148 closes as shown whereby fuel passes from inlet 134 to outlet 137; valves 138 and 139 operate in similar manner. The dump valve 142 is normally closed but is opened by application of servopressure PS4 to the piston 156. The sequence valve 90 shown in Fig, 1 comprises a sleeve having a plurality of ports and within the sleeve a control element rotatable by the shaft 73, shown also in Fig. 2, the control element being rotatable in five steps from A to F which correspond to positions of the pilots control lever. The relay device 160 functions so as to pass servo-pressure PS3 to the distributer 130 when it attains a predetermined value thus acting to open the valves 138, 139, 140. The fuel control apparatus comprises also a priming valve arrangement 200 shown in Fig. 7, the priming valve being disposed in parallel flow with the metering assembly 14 between the outlet of pump 10 and the inlet ports 132, 133, 134 of the distributer 130. The priming valve comprises a housing connected at inlet 205 to pump delivery pressure PP, the housing having a bore 202 in which is disposed a control member 201, the member being shown at its extreme rightward position in which it abuts stop 204 being moved to this position by spring 203. Application of pump delivery pressure PP causes the control member to move leftward at a rate dependent on size of the restrictor 208. As the control member moves to the left the orifices 218, 219, 220 become aligned with the annular grooves 209, 210, 211 whereby fuel passes through the non-return valves 212, 213, 214 to the lines 215, 216, 217 and so through the distributor 130 to the re-heat burners 20, 21, 22 which are therefore primed. As the control member continues its leftward movement the orifices 218, 219, 220 pass out of alignment with the annular grooves so fuel flow to the lines 215, 216, 217 ceases. As the control member approaches the extreme leftward position, the bore in the control member aligns with the outlet line 221 whereby fuel passes to the "hot-shot" ignition device 222 from which the fuel passes to ignition injectors 223, 224 in the main combustion section and downstream of the turbine respectively. The control element remains in its leftward position as long as the re-heat system is in operation. The "hotshot" ignition device 222 is controlled by servopressure PS3. Several alternative forms of priming valve arrangements are described.