GB831670A - Improvements in or relating to aviation turbojet engines having exhaust reheaters - Google Patents

Abstract

831,670. Gas-turbine jet-propulsion plant. SHEPHERD, G. R. (Westinghouse Electric International Co.). Nov. 18, 1957, No. 35812/57. Class 110 (3). [Also in Group XXIX] The fuel supply to the afterburner of a gasturbine jet propulsion engine comprises a fuel pump delivering fuel to an afterburner fuel metering control which energizes the pump to initiate an afterburning period and vice versa, a shut-off valve disposed in the supply conduit to the afterburner and a return conduit between the supply conduit and the afterburner control containing a check valve, the whole being so arranged that when the afterburner control is in the afterburning condition, the shut-off valve is opened and the check valve closed and vice versa. Fuel is injected into the jet pipe 20 by spray nozzles 24a, 24b attached to manifolds 23a, 23b and injecting fuel upstream and downstream respectively. Fuel is supplied to the nozzles from a reservoir 16 by a booster pump 19, an afterburner fuel pump 26, an afterburner fuel metering control 27, a multiple valve structure 28 and a servovalve 29. When the afterburner is out of operation with the lever 30 in the position shown, Fig. 1, the afterburner fuel pump 26 is de-energized but both the booster pump 19 and primary fuel pump 18 are in operation. Under these conditions, the port A on the control 27 is closed, the ports B, C, D are at the boost pump pressure obtained from the conduit 73 and the port E is at the primary pump discharge pressure obtained from conduit 74. The valve 29 is moved to the left by a spring 66 so that fuel from the port E flows through the valve 29, relief valve 72 and restriction 71 to the chamber 39 of the multiple valve 28, Fig. 2. Since the port B is at boost pump pressure the piston 37 is subject to a differential fuel pressure which forces the shut-off valve 42 into engagement with the seat 43a thereby stopping fuel flow to the afterburner. At the same time, the pressure differential causes the valve member 50 to lift and allow fuel to flow from the supply line to the recirculation conduit 58 back to the afterburner control 27. The restriction 71 limits the fuel flow and the relief valve 72 prevents fuel flow when the primary pump discharge pressure is below normal values, i.e. during starting. When it is desired to initiate afterburning the lever 30 is moved to the position 30a. Afterburner fuel pump 26 is then started. Under these conditions, ports A and B are at the discharge pressure of pump 26 the port C is at boost pressure and the ports D and E at the discharge pressure of pump 18 which is less than that of pump 26. The pressures at ports D and C move the valve member 60 to the right and cut-off the fuel supply to the conduit 70. Port A supplies fuel at the afterburner pump discharge pressure to the chamber 39 through conduit 32. The chamber 38 is also subjected to the afterburner pump discharge pressure. Under these conditions, the spring 56 closes the check valve member 50 thus stopping the flow through the recirculation conduit 58. Since part of the pressure on the lower face of the piston 37 is balanced by the pressure on the upper surface of the valve 42, the pressure in the chamber 38 will cause the piston 37 to move downwards against the action of the spring 40 and move the valve 42 to the open position in which fuel flows to the afterburner nozzles 24a, 24b.