Patent GB-1175058-A (GB)
Title: Means for controlling a plurality of gas turbine engines arranged to discharge into a common plenum chamber
Inventor: GASCOIGNE DENIS
IPC: F02C9/42
Filed: 1966-02-15
Abstract: 1,175,058. Gas turbine plant; power plant. JOSEPH LUCAS (INDUSTRIES) Ltd. Feb. 21, 1967 [Feb.15, 1966], No. 6515/66. Headings F1G and F1Q. The invention relates to an apparatus comprising a plurality of gas turbine type gas generators which discharge into a common plenum chamber, the gases discharging from the plenum chamber to a plurality of useful power turbines. Control means are provided for providing signals responsive to change in load on at least one of the power turbines, there being means for varying the inlet areas of the power turbines respectively, the means being responsive to said signals respectively, the arrangement being such that the total power gas consumption of the power turbines does not alter substantially from that prevailing before the change in load. Further means are provided responsive to change in the total load upon the power turbines for transmitting a further signal to the fuel systems of the plurality of gas generators so as to change their speeds whereby to provide pressure conditions in the plenum chamber which accord with the new total load conditions on the power turbines. The invention is described with reference to a plant which comprises fifteen gas turbine type gas generators and five useful power turbines. The control system comprises a pump 10 which supplies a constant flow of fluid to line 22, the fluid passing through five lines in parallel then back to the suction side of the pump through line 21. In each of the five lines is a spring- loaded flow responsive valve 11-15 and a valve 16- 20 each of which is responsive to the speed of a power turbine through a device such as 25 which is driven by the associated power turbine. Each of the flow responsive valves is connected to a device for controlling the angle of the inlet guide vanes of the associated power turbine-thus the valve 11 is connected to a spring-loaded piston 27, movement of the piston acting to adjust the position of the inlet nozzle guide vanes 29. A line 23 leads off from the line 22 to a device 24 whereby a signal may be transmitted to a passage common to the fuel supply systems of the gas turbine generators. In operation, should the load of one of the power turbines increase, the reduction of speed of the turbine will be communicated to the valve, say 16, which will move towards its closed postion. The pressure at the downstream side of the valve 11 will therefore increase and the piston 27 will actuate the guide vanes 29 so as to increase the flow area of the turbine inlet duct. The closing of the valve 16 will result in increased fluidpressure in the line 22 so that the pressure differentials across the valves 12, 13, 14, 15 will increase so that the pistons associated with the valves will move and actuate the guide vanes of the associated power turbines to reduce the flow areas of the turbine inlet ducts. It is arranged that the total area of the power turbine inlet ducts remains constant so that the gas consumption of the power turbines will not vary substantially until the speed of the gas generators has been changed to accord with the new load conditions. The increased pressure in the line 22 is transmitted through the line 23 to the device 24 which acts on the fuel systems of the gas generators to increase the speeds thereof so that the gas pressure in the common plenum chamber will increase. The speeds of the power turbines will thus increase and therefore the valves 16 to 20 will be operated and equilibrium conditions restored. An electrical control system is shown in Fig. 2, the system operating in a similar manner to the hydraulic system described. A constant current producing unit 30 is connected to five lines in parallel 31 to 32 each line having a fixed resistor 36 to 40 and a variable resistor 41 to 45 in series. The variable resistors are controlled by speed responsive devices such as 46 associated with the power turbine while each fixed resistor is associated with a voltage or current responsive servo-unit such as 47 which adjusts the inlet guide vanes 29 of the associated power turbine. Fuel supply to the gas generators is controlled by means of a solenoid operated valve 48.