Patent GB-1057945-A (GB)
Title: Air breathing starters for gas turbine engines
IPC: F02C7/26
Filed: 1963-10-10
Abstract: 1,057,945. Gas turbine plant; engine stop-gear. BENDIX CORPORATION. Oct.10, 1963 [Oct. 22, 1962], No. 39976/63. Headings F1G and F1K. A starting system for a turbine engine comprises a hot gas generator having a compressor driven by a first turbine and supplying compressed air to a combustion chamber, a second turbine for starting the turbine engine and connected to the latter through speed reducing means and an overrunning clutch, the two turbines being supplied with hot gases from the combustion chamber, and electric means and control means for supplying electricity to rotate the compressor and to provide self-sustaining combustion, the control means having speed sensing means arranged to shut down the starting system when the second turbine rotates at a predetermined speed. The compressor 13 of the starting system supplies air to a combustion chamber 17, the combustion gases passing successively through a turbine 27 driving the compressor and integral therewith and through a turbine 31. The shaft 29 of the compressor is hollow, and the shaft 33 of the turbine 31 passes through it and is connected through planetary reduction gearing 47 and an overrunning clutch 49 to a jet-propulsion aircraft engine (not shown) which is to be started. When a manual starter button switch 103 is closed, current flows from a bus-bar 101 to energize an electric motor 41, 43 for turning the compressor 13 through an overrunning clutch 39 and reduction gearing 37. In addition, a solenoid 67 is energized to open a fuel valve 65 to admit fuel from a fuel pump 87 to the combustion chamber 17, and a spark plug 23 is energized via an ignition coil 123. When the pressure of the resultant self-sustaining combustion in combustion chamber 17 reaches a predetermined value, pressure-responsive devices 75, 77 close switches 81, 83. Switch 81 energizes the coil 115 of a relay 109 which changes over from the position shown to break the circuit to the ignition coil 123 and to energize the coil 143 of a relay 129, the latter changing over from the position shown to de-energize the motor 41, 43. Energization of the solenoid 67 is continued through the switch 83 independently of the manual switch 103, which can now be released. Switch 83 also energizes a solenoid 63 to open a further fuel valve 61 to increase the fuel supply to the combustion chamber 17. When the turbine 31 has accelerated the aircraft engine to the starting speed of the latter, a centrifugally-operated switch 57 opens to de-energize the solenoids 63, 67 and thereby close the fuel valves 61, 65. As the pressure in the combustion chamber 17 decreases, switches 81, 83 return to the open position and relays 109, 129 are de-energized. The system is now ready for the next start. If, before the switch 57 opens, the shaft 29 overspeeds or the temperature in the combustion chamber 17 exceeds a predetermined value, a centrifugally-operated switch 59 or a thermallyoperated switch 161 opens to terminate the starting sequence. In further embodiments, Figs. 3 and 4 (not shown), the bus-bar supplies current to the motor 41, 43 only, current for other purposes being supplied by a generator driven from the shaft 29. In addition (Fig.4 only), the centrifugally-operated switches 57 and 59 are replaced by resonant reed switches (321, 319) which are energized to their respective resonant frequencies through pick-ups (317, 315) and magnetic projections (325, 323) on the shafts 33, 29 when the shafts reach their respective predetermined speeds, thereby triggering a thyristor (331) to energize a relay (305) which shuts down the starting system.