Patent GB-564498-A (GB)
Title: Improvements in and relating to gas turbine power plants
Filed: 1943-07-01
Abstract: 564,498. Fluid-pressure servomotors. BRITISH THOMSON-HOUSTON CO., Ltd. July 1, 1943, No. 10672. Convention date, July 1, 1942. [Class 135] [Also in Group XXVI] The plant comprises turbines 1, 2, each driving a rotor of a double-rotation air compressor 3, 4, turbine 2 also driving an external load 33; speed governors 29, 32 for each turbine, and means for controlling the fuel supply valve 18 in accordance with the load on 33 which is, in the example shown, a three - phase generator. The compressor has inlets 10 and a single volute discharge pipe leading to a pipe 13 supplying compressed air through a heat exchanger 15 to a combustion chamber 14. Fuel is led to the latter by a pipe 17 controlled by the valve 18. Gas is supplied to the turbines by way of pipes 19, 20, and the exhausts pass through pipes 21, 22 to the exchanger 15 which may be of any suitable type. The governors 29, 32 act on servomotors 27, 30 to control the positions of valves 25, 26, to regulate the supply of gas to the turbines. Valve 26 may be fully open for normal conditions, the governor 32 preventing overspeeding of the turbine 2. The speed of turbine 1 is increased or decreased as the load on the generator increases or decreases, but not necessarily at the same rate. This is secured through a solenoid 37, opposed by a spring 40, connected with one phase of the generator. A lever 34 is pivoted at 35 and moves a second lever 28 which controls the servo piston supplying the cylinder 27. On increase in load of the generator, solenoid 37 moves the lower end of lever 34 to the right to effect an opening movement of the valve 25, thus increasing the pressure of the air delivered by the compressor. The setting of the fuel valve 18 is under control of a thermostat 41, e.g. a thermo-couple, having its lead wires 42 connected through an amplifier and relay 43 to the winding of a solenoid 44 acting on a lever 45. Rheostats 47, 48, in series, are in circuit with the solenoid 44, but may be cut out by closing a switch 60. The arm 49 of rheostat 47 is pivoted to a link 50, fixed to the lever 45. As lever 45 moves to open or close valve 18, it adjusts the arm 49 to vary the amount of the resistance of rheostat 47 in circuit with the winding of solenoid 44. Rheostat 48 is provided with a manually adjustable regulating arm 51 to vary the resistance of 48 in the solenoid winding circuit. When a switch arm 52 is in the position shown, movement of lever 45 in a direction to open valve 18 causes arm 49 to cut resistances out of the solenoid winding circuit. When switch arm 52 is moved to the left-hand contact 53, the opposite result is obtained. The other end of lever 45 is pivoted to a plunger of a solenoid 55, the winding of which is connected by conductors 56 to a load coil 561 on the generator. As the load on the generator increases, the current in solenoid 55 increases to open further the valve 18. The adjustment of valve 18 by the device 41 is comparatively small compared to the adjustment secured by the load coil 56<1>. The temperature in the combustion chamber may increase with load increase, or decrease. The alteration is secured by adjustment of the rheostat 47 and the switch arm 52. By setting arm 52 on an intermediate contact 53, any desired regulation of temperature with load may be obtained. When switch 60 is closed rheostats 47, 48 are short circuited and the temperature in the chamber 14 is maintained constant at all loads. Compressor rotors may be operated at different speeds, and that of the rotor 4 may be substantially constant.