GB970660A - Improvements in or relating to gas turbine power plants - Google Patents

Abstract

970,660. Gas turbine plant. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. Nov. 20, 1962 [Dec. 6, 1961], No. 43717/61. Heading F1G. [Also in Division G3] A control system for a gas turbine power plant comprises means providing an indication of the temperature of the gases flowing through the turbine, means sensitive to that indication and upon occurrence of an excessive temperature acting to reduce the supply of fuel to the combustion chamber, there being also means providing an indication of the speed of the gas turbine and means arranged in accordance with that indication to effect suitable adjustment of the means acting to reduce the supply of fuel to the combustion chamber so that during starting up of the gas turbine plant, a rate of fuel supply to the combustion chamber is allowed which would be excessive for normal full speed operation. The plant shown comprises an air compressor 1, combustion equipment 11 and a turbine 5, an electrical tachometer 7 being mounted on the compressor-turbine shaft 3. Fuel is supplied to the combustion equipment through line 17 through control valve 19, the valve being connected at 39 to an E.M.F. comparison unit 35. Thermocouples or groups thereof are disposed at 21 at the outlet of the combustion equipment and at 23, 25, 27 at spaced locations along the gas flow path through the turbine. Signals from the thermocouples are passed through lines to the electronic scanner 31 which selects each of its inputs in sequence and applies the selected input to the unit 35 through lead 33. A signal indicating turbine speed is also passed to the unit 35 from the tachometer 7 through line 37. The comparison unit 35 repeatedly compares the selected signal applied through lead 33 with a reference signal and if the signal applied through lead 33 indicates an excessively high temperature the unit acts to adjust the valve 19 to reduce the flow of fuel. During starting, it is permissible to operate at temperatures which would be excessive for continued operation and the reference signal therefore has a high value. As the turbine approaches its normal speed, the signal from the tachometer acts to change the reference signal to a lower value. The unit 35 will thereafter act to reduce the rate of fuel flow at lower temperatures at the points monitored by the thermocouples. In place of thermocouples, there may be means which sense the air and fuel flows and provide an indication of the air/fuel ratio and thus the temperature attained in the combustion chamber. Again in place of a tachometer the means providing an indication of the speed of the gas turbine may comprise a device sensitive to the pressure of the gas stream through the power plant at a suitable point; alternatively, it may comprise a device sensitive to the fuel pressure at a point in the fuel supply system at which the pressure varies in a suitable manner with the turbine speed.