Patent GB-1338766-A (GB)
Title: Gas turbine engines
IPC: F02C9/54
Filed: 1970-12-18
Abstract: 1338766 Gas turbine engines: jet propulsion engines MOTOREN-UND TURBINEN-UNION MUNCHEN GmbH 18 Dec 1970 [18 Dec 1969] 60349/70 Headings F1G F1J and FIT In a gas turbine engine, Fig. 2, a control unit 12 for adjusting, via a servomotor 29, the inlet guide vanes 17 of the power turbine 18 (or the jet nozzle area where the engine is used for jet propulsion) is fed with inputs representing the total pressure P 01  static pressure P 1  and absolute temperature T 01  immediately upstream of the compressor, 3 and the total pressure P 03  downstream of the compressor, the control being such that the engine operates below the surge limit. A further input representing the absolute temperature T 04  at the outlet of the gas generator turbine 14 enables the working line to be adjusted upon variation of other engine variables. The control unit 12 is also fed with inputs representing the gas generator speed n 1 , the power turbine speed n 2 , and inputs representing the positions of the accelerator pedal 55 and brake pedal 97. The control unit 12 controls the fuel supply to the fuel nozzle 11 in accordance with the speed n, and the accelerator pedal position, and also acts to reduce the speed n, in the event of the speed n 2  exceeding a certain value. The brake pedal 55 adjusts the guide vanes 17 to a reverse position in which they exert a braking effect. A regenerative heat exchanger 8 is driven by the gas generator turbine 14. The control circuit is shown in detail in Figs. 4a, 4b, 4c. A fuel flow supplied by a pump 61 is split into separate flows through measuring conduits 63, 64 containing variable orifices 67, 71, a fixed orifice 66 and a adjustible orifice 70. Orifice 67 is valued in accordance with the pressure P 01  and the compressor inlet ram pressure q, (which is the difference between the pressures P 01  and P 1 ) to provide an orifice area F 1  which, for example, is proportional to the product P 01 , q 1 . Orifice 71 is raised in accordance with P 03  and T 01  to provide an orifice area F 2  proportional to f (T 01 ) P 03 , where α is a constant. An additional input 93 provides a desired value of the gas generator inlet temperature T 03 . The pressures downstream of the orifices 67, 71 are sensed at 68, 72 and applied to opposite ends of a control piston 73a, 73b to control the position of a servomotor piston 79 which adjusts the angularity of the guide vanes 17. Fuel for energizing the servomotor is supplied from the pump 61 through a solenoid valve 85 which is closed when the accelerator pedal 55 is in the idling position. Operation of the brake pedal 97 opens a solenoid valve 95 to move the piston 79 towards its extreme right-hand position to bring the guide vanes 17 into the reverse position for braking. A pump 101 supplies fuel to the fuel nozzle 120 via a governor valve 54 which is controlled in accordance with the speed n, by flyweights 107 in opposition to the force of a spring 108 which is adjusted by the accelerator pedal 55, minimum and maximum values of fuel flow being set by stops 114, 115. If speed n 2  becomes excessive, an overspeed governor 116 operates the governor valve 54 towards reduced fuel flow. If speed n 1  becomes excessive, an overspeed device 110 is tripped to open a fuel by-pass valve 111. Another by-pass valve 112 is opened when the engine is stopped. A further by-pass valve 123 is closed only when the electrical system is energized. During acceleration, the fuel supply to the fuel nozzle 120 may tend to produce an excessive operating temperature, this being indicated by an excessive pressure differential between the measuring points 68, 72. A piston valve 130a, 130h subjected to the pressure differential then diverts some of the fuel flow from the line 135 leading to the fuel nozzle and directs it instead to a line 133 to act on a piston 137 to cause partial or complete closure of a valve 138 in the line 140 connecting the measuring point 68 to one side of the piston 130a, 130b. This causes the guide vanes 17 to be moved towards the fully open position.