Patent GB-1045722-A (GB)
Title: Improvements relating to the starting and operation of power units incorporating gasturbines
IPC: F02C7/26
Filed: 1964-01-21
Abstract: 1,045,722. Gas turbine plant. G. BAYARD. Jan. 21, 1964 [Nov. 27, 1963], No. 2641/64. Heading F1G. A gas turbine engine for starting a main engine (not shown) comprises a first-stage turbine 2, Fig. 1, driving the air compressor 1, and a second-stage turbine 4 which turns the main engine through reduction gearing 5 and a freewheel 6. The gas turbine engine is itself started by an electric motor 7 through step-up gearing 8. When a starting button 62, Fig. 3, is depressed, a relay 58 is energized to start an electrically-driven fuel pump 11 and open a solenoid-actuated fuel valve 13; a delayedaction relay 56 is energized; and a relay 55 is energized to hold the circuit after release of the button 62. Fuel injectors 15 are supplied by the fuel pump 11 through the valve 13 and a regulator 14. The fuel pressure at the injectors 15 and the pressure in the combustion chamber 3 are applied through pipes 26, 29 respectively to respective diaphragms 19, 20 in the regulator 14 to control a needle valve 18 which by-passes fuel to a drain line 16, whereby the fuel injection pressure is regulated to increase as the combustion pressure increases, the diaphragm 19 being smaller in area than the diaphragm 20 so that the fuel injection pressure increases more rapidly than the combustion pressure. When the fuel injection pressure has risen sufficiently, it actuates a pressure-operated switch 46 to energize a delayed-action relay 57 and a relay 59, and de-energize the delayedaction relay 56. If, however, a fault prevents the fuel injection pressure from rising to the required value during the delay in operation of the relay 56, the latter operates to terminate the starting sequence. Relay 59 energizes sparking plugs 10 through an ignition coil 9 and energizes the starter motor 7 through a resistance 53 to run at reduced speed. After the resistance 53 has heated a thermostat 52 sufficiently, the thermostat energizes a relay 60 which shorts out the resistance to allow the motor 7 to run at full speed. When the combustion pressure has risen sufficiently, it actuates a pressure-operated switch 50 to de-energize the relay 59 to switch off the starter motor 7 and ignition coil 9; de-energize the delayed-action relay 57 ; re-energize the delayed-action relay 56; and energize a relay 61 which feeds electrical circuits for the starting of the main engine. If, however, a fault prevents the combustion pressure from rising to the required value during the delay in operation of the relay 57, the latter operates to terminate the starting sequence. When the speed of turbine 4 (and therefore of the main engine) reaches a predetermined value, a speed-operated switch 54 opens to de-energize the relay 55 whereby the starting circuits are de-energized. The relay 56 limits the duration of this final stage. If, when the starting sequence was initiated by pressing the button 62, the gas turbine engine was still hot from a previous operation, a thermostat 51 operated by the hot exhaust gases remains closed, the initial part of the starting sequence is obviated, and the relay 59 is energized through the thermostat 51 as soon as the button 62 is pressed. The fuel injectors 15 are of the type incorporating a valve which is opened against the action of an adjustable spring force when the fuel injection pressure reaches a predetermined value, this value being different for each injector so that the injectors open one after the other as the fuel injection pressure rises.