688,492. Gas turbine plant. SULZER FRERES SOC. ANON. June 29, 1950 [June 30, 1949], No. 16244/50. Class 110(iii) [Also in Group XXIX] A gas turbine plant comprising at least one useful output power turbine and at least one turbine for driving a compressor is controlled in the case of rapid load variations, by influencing the heat supply to the working medium entering the power turbine or turbines and in the case of prolonged variations by subsequently influencing the pressure level in the plant. The plant shown, Fig. 1, comprises a compressor 1 which delivers air through two heat exchangers 5, 6 to a pipe 7 where it is divided. Part of this air flows through a gas heater 10 located in a combustion chamber 12 to a turbine 14 driving the compressor 1 and the remainder is used as combustion air in the chamber 12. The exhaust gas from the turbine 14 passes through the heat exchanger 5 and cooler 17 back to the inlet of the compressor 1. The combustion gases from the combustion chamber 12, pass through a turbine 22 driving a charging compressor 35, a reheating combustion chamber 24, the useful output turbine 30 and the heat exchanger 6 to atmosphere. The supply of fuel to the combustion chamber 12 is controlled by the pressure in conduit 13 through which working medium is supplied to the turbine 14. The fuel supply to the reheating combustion chamber 24 is controlled by a valve 27 influenced by a speec responsive unit III and the pressure in the chamber Changes of load on the power turbine cause the centrifugal governor to operate the control valve 63 regulating the pressure of oil in the system beneath it. This at once influences the valve 27 which increases or decreases the fuel supply to the reheat chamber 24. For a persistent load change, this pressure will also act on the piston 68 of a servomotor 69 of a pressure level adjusting device I. A throttle valve 66 is provided to delay the action of this pressure. This servo-motor determines by means of a cam and follower 71, 72 the loading of a spring 73 which is connected to a control valve 74 which allows oil under pressure to pass into or from the left hand side of a piston 78 of a servomotor 75. The right hand-side of the piston is connected through a pipe 79 to the inlet of the turbine 22. Movement of the piston 78 actuates a servo-motor valve 82 which allows pressure fluid to one side or the other of a piston 83 which then moves and alters the loading of a spring 92. The movement of the piston 83 returns the valve 82 to the shut off position and stresses the spring 88 through yielding follow up mechanism 84. The mechanism can only come to rest in the neutral position, that is when the fulcrum of the lever 86 is in its central position and the spring 88 unloaded. This occurs when the pressure at the inlet to the turbine 22 equals the pressure of the pressure fluid on the piston 78. The spring 92 is connected to a further control valve 93 which controls the pressure in the impulse pipe 50 according to the loading of the spring 92. The pipe 50 is connected to a servo-motor 49 which actuates a valve 48 in a pipe 47 by-passing the first stage or stages of the turbine 14. Persistent changes of load will therefore affect the speed of the turbine 14 and compressor 1 and, as a result, the pressure level in the plant. The change of pressure at the inlet to the turbine 22 will return the piston 78 to the central position and decrease the fuel supply to the reheat chamber 24 by its action on a piston 121. The decrease of fuel will be in part compensated by an increase due to the action of the pressure in the chamber 24 on a piston 122. The change of pressure at the inlet to the turbine 22 also operates on a piston 98 of a secondary pressure level adjustive device II which actuates the piston 100 of a servo-motor having an isodromic control similar to that described with reference to the piston 83. The piston 100 alters the loading on a spring 109 controlling the pressure in an impulse pipe 42 leading to servo-motors 40, 41 controlling a throttle valve 39 and by-pass valve 38. The springs 45, 46 of these servo-motors are so chosen that, as the pressure in the pipe 42 increases, the valve 39 is first fully opened and then the valve 38 is opened. The operation of the valves 39, 38, varies the back pressure on the charging turbine 22 which results in a change in the delivery pressure, of the compressor 35. This pressure is transmitted through the pipe 44 to the piston 113 of a servomotor 114 which actuates a cam 117 controlling the loading on a spring 119. This spring controls the pressure on the left hand side of the piston 98 which is returned thereby to the central position. Where large load increases have to be catered for, additional air may be supplied to the circuit from a container 123. On a sudden decrease of speed of the turbine 30 the pressure in the pipe 54 rises and first opens fully the valve, 27; any further increase in pressure actuates the piston 126 and opens the valve 124 to allow compressed air to enter the circuit from the container 123. To prevent overspeeding of the turbine 30 when the load is suddenly reduced, two servo-motors 129 and 130 are connected by a pipe 127 to the governor control valve 63. These servo-motors control a blow-off valve 131 and a throttle valve 132 respectively. If, the pressure in the pipe 127 falls quickly, the blowoff valve 131 is opened and the valve 132 closed simultaneously. An open-circuit gas turbine plant, Fig. 2, comprises a compressor 140 supplying air to a combustion chamber 144 through a heat exchanger 142. The combustion gases flow to a useful power turbine 148 and a turbine 151 driving the compressor 140. Attached to the shafts of these turbines are machines 157, 162 which may operate either as a motor or generator according to the position of the brushes as determined by the rod 158. The fuel supply to the combustion chamber is controlled by a valve 178 controlled by a servomotor 154. The pressure of the supply of pressure fluid to the servo-motor 154 is controlled by a valve 175 in accordance with the loading of a spring 174. The loading of this spring is varied in accordance with the load on the generator 149 by a solenoid 170, the energising coil of which is placed across a resistance 168 in one of the phase lines. Changes of pressure of the pressure fluid are also transmitted through an impulse line 163 to the servo-motor 159 controlling the position of the brushes. So that only sustained changes of pressure are transmitted a throttle valve 164 and a pressure vessel 165 are inserted in the impulse line 163.