GB740090A - Improvements relating to starting and ignition systems for gas turbine engines - Google Patents

Abstract

740,090. Gas turbine plant. ROLLSROYCE, Ltd. Dec. 11, 1953 [Dec. 12, 1952], No. 31616/52. Class 110(3) A starter system for 'a gas turbine engine started by an auxiliary turbine supplied with combustion products from an independent combustion chamber, comprising electrical igniter means in both the main and auxiliary combustion chambers and a source of electrical energy for supplying both igniter means, has switching means for transferring said source from the igniter in the auxiliary combustion chamber to the igniter in the main combustion chamber at an appropriate point in the course of starting the gas turbine engine. To start the engine, a manual push-button 30 is closed. This energizes a relay coil 31 of a rotary time control mechanism having cams which close the contacts 32, 33 and 34 and allow the push-button 30 to be released. The closure of contacts 32 energizes a relay 35 which closes contacts 36 and thereby energizes the solenoids 37, 38. These solenoids open valves controlling the air and fuel supply to an auxiliary combustion chamber supplying combustion gases to a starter turbine. These valves are spring-loaded to the closed position. The closure of contacts 33 energizes the high tension supply apparatus 39 which is connected through the lead 40 to a switching relay 42. The armature 44 is biased by a spring 43 to make contact on a lead 26A feeding the igniter means in the main combustion chamber. The closure of contacts 34 energizes relay coil 45 causing the armature 44 to connect the lead 40 with the lead 25A feeding the igniter means in the auxiliary combustion chamber. After a predetermined time, the time control mechanism opens the contacts 32, 33, which causes the relay 35 and high tension supply apparatus 39 to be de-energized. The fuel and air supply to the auxiliary combustion chamber is then shut off. When the auxiliary turbine drives a compressor supplying combustion air to the auxiliary combustion chamber the solenoid 38 and the valve operated'by it may be dispensed with. In a mcdification of this arrangement the solenoid 38 may be replaced by an electric starting motor for the auxiliary turbine. The time control mechanism may be replaced by a centrifugally operated switch responsive to the speed of the auxiliary turbine, or by a temperature responsive switch responsive to the temperature of the exhaust gases of the auxiliary turbine. In a preferred arrangement, the time control mechanism is retained and the centrifugally operated switch or temperature responsive switch is arranged in series with the contacts 34 to de-energize the relay coil 45 and so connect the lead 40 with the lead 26A. An overspeed centrifugally operated switch driven by the auxiliary turbine may be placed in the lead between the battery and contacts 33 to shut down the auxiliary turbine when it reaches a preselected speed.