GB1135431A - Fuel supply system for a jet propulsion engine - Google Patents

Abstract

1,135,431. Gas turbine jet propulsion plant; fluid logic circuits. DOWTY FUEL SYSTEMS Ltd. June 7, 1966 [June 10, 1965], No. 24653/65. Heading F1J. [Also in Division G3] A gas turbine has a main burner gallery 8 and reheat burner galleries 31-34 the flow to which is controlled by a single throttle lever 11. Over the range O-P the lever operates a device 12 to control the delivery from a pump 9 to gallery 8, and over the range P-S the lever operates a device 13 to control the delivery from a pump 16 to galleries 31-34. An on-off valve 22 in reheat line 19 is controlled by a switching valve 14 and is opened to supply gallery 31, when the lever moves from P-Q. Progressive movement of the lever from R to S operates a device 15 having an output shaft 35 carrying cams 37, 39, 42 which operate valve devices 23-25 successively, the devices 23-25 controlling priming and main flow to galleries 32-34 respectively. A variable area nozzle 50 controlled by a unit 55 responsive to the rate at which reheat fuel is burned, e.g. the ratio of compressor delivery pressure to jet pipe pressure, is connected to a feedback shaft 36 having cams 38, 41, 43 which also engage devices 23-25, the arrangement being such that when the lever selects reheat at one or more of the galleries 32-34 the corresponding devices 23-25 will only function to allow reheat fuel flow if nozzle 50 is in its correct position. Device 23, which is identical to devices 24, 25, is shown in Fig. 2 and comprises, a valve 66 having a closure member 71, 72 controlling flow to line 27 feeding gallery 32, a fluid logic servo-device 67 controlling valve 66, and a pilot valve device 68 having piston valves 44, 45 which extend outwardly into contact with cams 37, 38 respectively. When lever 11 starts to turn from R to S to demand more reheat, cam 37 allows piston 44 to move to the position shown and, assuming nozzle 50 has opened sufficiently, cam 38 allows piston 45 to move to the position shown. Fuel from priming supply line 18 now flows via port 88 to lines 91, 95 to divert the output flows of bi-stable switches A, B to an AND gate F to produce a signal in line 105 which diverts the output of bi-stable switch C to lines 106, 76. Fuel thus reaches chamber 75 in valve 66 and starts to move the closure member to the left to allow priming fuel flow to line 27 via lines 18, 109, vortex restrictor H. (which is unrestricted since there is no signal in line 108), port 111, line 79, annular chamber 81, passage 82 and chamber 83. As the closure member moves to the left, chamber 77 discharges through line 78 and the inlets 107, 113 of a summing junction G, and some fuel in the main reheat line 19 is allowed to pass to line 27 and gallery 32 but is not immediately burned. The flow to gallery 31 is correspondingly reduced, however, and nozzle 50 is automatically reduced in area and this moves piston 45 slightly to the left to cause a piston 99 thereon to transmit a signal to bi-stable switch D via line 102 to divert the output of switch D to chamber 77 via line 112, diode J, Tesla diode 115, summing junction G and line 78. Furthermore, the resistance of vortex restrictor K is reduced (since there is no signal in line 116), and the closure member is stabilized in a position partly covering a port 84 connected to chamber 77 via restrictor K and port 85. In this position, priming fuel flows to line 27 together with a small quantity from main line 19. When gallery 32 is primed and its discharge starts to burn, nozzle 50 is enlarged in area and piston 45 is allowed to move to the right to produce a pulse in line 103 to switch the output of switch D to line 116. The resistance of restrictor K is thus increased so the supply to chamber 77 from port 84 falls and since the supply from line 78 is lost the closure member is moved to a fully open position at which the priming flow is cut-off. At this stage, lever 11 is one-third of the way from R to S and must be moved further to supply the other galleries. To close down reheat, lever 11 is returned and moves piston 44 to inwardly to supply pressure fluid to line 92 to divert the output of switch A to AND/OR gate E to provide a signal in line 104 which simultaneously acts to divert the output of switch C to line 107 and to increase the resistance of restrictor H. Restrictor K is still restricted by the signal in line 116 so fuel entering chamber 77 via line 78 moves the closure member to the right to close the valve, chamber 75 at this time being vented through line 106. Flame failure will also cause shut down of reheat flow since the nozzle will move piston 45 inwardly to admit a pulse to line 95 to divert the output of switch B to AND gate E and close the valve as described above.