GB724004A - Improvements in or relating to fuel supply arrangements for gas-turbine engines - Google Patents

Abstract

724,004. Gas-turbine jetpropulsion plant. ROLLSROYCE, Ltd. April 9, 1953 [April 29, 1952], No. 10812/52. Class 110 (3). A gas-turbine jet-propulsion engine' has a reheat chamber before the propulsion nozzle to which fuel is fed by an air turbine-driven fuel pump, the turbine of which is fed with air tapped off from the compressor and which exhausts to atmosphere through a restriction whereby the pressure ratio across the air turbine is less than the ratio of the inlet pressure of the air turbine to atmospheric pressure. Air from the compressor 10 is fed to the combustion equipment 11 which supplies combustion gas to the turbine 14 driving the compressor. The turbine 14 exhausts to the atmosphere through a jet pipe 18 and variable area propelling nozzle 19a. Under normal conditions fuel is supplied to the combustion equipment 11 from a tank 12 by pumps 12a, 15 and is controlled by a throttle 13. When additional thrust is required fuel is supplied to the main burners 20 in the jet pipe 18 by a fuel pump 26 driven by an air turbine 27. The main burners are ignited by a pilot burner 21 supplied with fuel by the pump 15. The air turbine 27 is supplied with air by the compressor 10 through a conduit 28 and throttle valve 29. To avoid an excessive run-away speed of the air turbine 27 the pressure ratio across the turbine is limited. In the arrangement shown, the air turbine exhaust conduit 30 is connected to the jet pipe 18 so that the exhaust air passes through the propelling nozzle 19. When the reheat system is in operation, the propelling nozzle 19 is usually choked so that the pressure drop across the air turbine is less than if the turbine exhausted to atmosphere so that the run-away speed is limited. In another arrangement, the conduit 30 is connected to a manifold encircling the jet pipe having nozzles which induce cooling air from the atmosphere into a casing surrounding the jet pipe and then through hollow variable area nozzle segments. To cool the jet pipe when the reheat is out of operation, a bypass pipe containing a restrictor may be provided around the turbine. The flow may be diverted through either the turbine or bypass pipe by a two-way valve. The air turbine 27 is preferably a two-stage pressure-compounded impulse turbine, that is, one in which part of the expansion takes place in the first stage stationary nozzles and the remainder in the second stage stationary nozzles. Specifications 608,963 and 667,394 are referred to.