Patent GB-700098-A (GB)
Title: Improvements in and relating to control systems for air compressor plants
IPC: F04D27/02
Filed: 1950-07-24
Abstract: 700,098. Axial-flow compressors; gas turbines. BRITISH THOMSON-HOUSTON CO., Ltd. July 24, 1950 [July 29, 1949], No. 18434/50. Classes 110 (1) and 110 (3) [Also in Group XXIX] A plant, including a gas turbine driving an axial-flow air compressor, has regulating means to maintain substantially constant speed which include an air turbine 2; supplied through a byepass 14 with excess air delivered by the compressor. The turbine 2. assists in driving the compressor shaft. A throttle valve 15a, for the supply to the turbine' 2, is controlled by the pressure in the air delivery pipe 39, acting through a pipe 16 on a spring-pressed diaphragm 17. " Useful output" air from the compressor passes up a pipe 5, past a check valve 7, venturi 9 to the pipe 39 and control valve 8. A byepass 10 has a valve 11 under control of a spring 12 and a solenoid 13. A variable quantity of air flows through the pipe 14 to the turbine 2 in accordance with the demand from the pipe 39, which affects the valve 15a, the byepassed air through 14 being utilized instead of exhausting the atmosphere. Electric contacts 28, 29 are closed when the valve 15a is closed, and through the circuit 30, the valve 11 is also closed. When the pressure at valve 8 falls, the pressure in chamber 19 drops causing a lever 25 to move clockwise to move the valve 15a in a closing direction to decrease the amount of air bled through the byepass 14 so that the pressure in pipe 39 rises. The diaphragm 17 then moves slightly to the right. A handwheel 23 may adjust the pressure of the spring 20. The valve 8 may be left open when the plant is stopped as the check valve 7 prevents backflow of compressed air. A starting motor 4 is used to bring up the gas turbine to " firing-speed " at which the ignition system is energized to start combustion. The fuel supply is controlled by a handle 1a, or equivalent automatic devices. When the byepass valve 11 is. closed, the venturi 9 serves to limit the quantity of "useful air" passing to the consumer. An over-speed governor and other safety devices may be incorporated in the fuel regulator. A manual lever 27 is provided for holding the valve 15a open during. starting-up operations. The position of the valve 15a indicates when the maximum load condition of the plant has been reached..Other signals may be used, e.g. contacts on the lever 1a. The gas turbine discharges to atmosphere, no heatexchangers being used. The turbine 2 may be a standard steam-turbine type and operate through a reduction gear 3. The power plant is described in Specification 15817/48 as open to inspection under Sect. 91, and the fuel regulator in Specifications 700.092, [Group XXXV], and 638,494, [Group XXIX]. Fig; 2 shows an alternative arrangement for controlling the air-turbine inlet valve. The movement of the diaphragm 17 acts through a rod 24 and lever 31 to operate a valve 34 which admits fluid to one side of a piston in a servomotor 33. Contacts 28, 29 function as before. Other equivalent mechanical, hydraulic or electrical systems may be used for moving the valve 15a. Quantities of air delivered, and their pressures, are given in the Specification.