Patent GB-620234-A (GB)
Title: Improvements in or relating to control systems for gas turbine electric generator power plant
IPC: B61C5/00
Filed: 1947-01-10
Abstract: 620,234. Fluid-pressure servomotor-control systems; regulating pressure of fluids. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Jan. 10, 1947, No. 914. Convention date, Jan. 12, 1946. [Class 135] [Also in Group XXVI] A gas-turbine plant, including turbine 18, compressor 19, economiser 26 and combustion chamber 23, drives an electric generator 27 which provides power for traction motors 28. The field windings of the generator 27 are energized by an exciter 30, the field coils 31 of which are in series with controlling resistances 36, 37. The gas-turbine plant is run at a desirable speed, whatever the load, by varying by means of the rheostat 36, the voltage at which the generator operates. The fuel valve 24 and the rheostat 36 are operated by one control through fluid-pressure devices and that of the rheostat includes a delay device so that the compressor-turbine speeds up more rapidly than the load is applied. Similar controls, for alternative use, are provided in two cabs of the locomotive. Each comprises a first control 16 which includes a reversing switch 34 and a stop valve 56 in the control pressure-fluid system. A second control 17 operates the resistor 37 and the spring- loading 57 on a leak valve 58, which controls the fluid pressure in the control line 42 leading to the fuel-valve actuator 78 and the device 55 operating the rheostat 36. The fuel valve 24 is closed, in opposition to a spring 77, by upward movement of a piston 80 which is subject to pressure-fluid from the line 42. This fluid passes a non-return valve 88 and through a screw-thread passage cut on an axially-adjustable rod 85 to a port 84. The lower end of the screw-thread passage is open to atmosphere and the pressure in port 84 is, accordingly, a fraction of the pressure in the line 42 determined by the axial position of the rod 85. The arm 39 of the rheostat 36 is operated by a fluid-pressure relay which includes a piston valve 95 loaded above by a spring 96 and pressed upwards by pressurefluid from the control line 42 under a pressure determined by the pressure divider 100. A follow-up action is provided by a lever 97 and a cam 98 which alters the spring loading of the piston 95. Operating fluid for the cylinder 93 is throttled by a needle valve 101 so that the action of the relay in varying the voltage of the generator is slower than the control of the fuel valve 24. The speed-governor 66 operates a leak valve 67 which controls the fluid pressure in a pipe line 43 beyond a restriction 51. Increase of turbine-speed closes the leak valve, whereupon the pressure in the pipe line 43 rises above that in the control pipe line 42 and the governor takes over the control of the fuel-valve actuator 78. The speed for which the governor is set is determined by the axial position of the valve-seating piston and that is varied by means of a cam 71. The cam 71 is controlled by a piston 75 which moves to balance the pressure of a spring 76 and the pressure-fluid has passed a pressure divider 74. In emergency, a trip governor 105 opens, at 102, a pipe line 44 which is supplied through a restriction 53. On the failure of the pressure in this line, a spring 109 drives down a pistonrod 111 to close the fuel valve 24 and a spring 113 opens a valve 108 by which the compressor discharges to atmosphere. Fluid for the control system is provided by a separately driven pump 45.