665,062. Gas turbine plant. AKT.-GES. FUR TECHNISCHE STUDIEN. Oct. 20, 1949 [Nov. 4, 1948], No. 26971/49. Class 110(iii) [Also in Group XXIX] In a power plant in which a gaseous medium describes a closed circuit including at least one compressor and at least one turbine and is heated from the outside in a heater, the fuel and air supplies to the heater are controlled in accordance with the relationship between the pressures at two or more points in the expansion part of the circuit. In the plant shown, the working fluid passes from the compressor 8 through the heat exchanger 6 and heater 1 to the turbine 4 which drives the compressor 8, a governor 69 and a generator 12. The exhaust from the turbine 4 passes through the heat exchanger 6 and cooler 7 back to the inlet of the compressor 8. The heater 1 is pressurized by a compressor 16 driven by a gas turbine 21 utilizing the hot gases from the heater. An electric machine 23 is provided to enable the output of the compressor 16 to be controlled. Part of the hot gases are recirculated through the heater by a fan 25 driven by a variable speed motor 27. The fuel supply to the heater is controlled by a throttle valve 58. The inlet and exhaust pipes of the turbine 4 are connected by pipes 28, 29 to spring loaded pistons 30, 31 which together operate a rod 35 carrying cams 36, 37, through a lever 34. When the load on the generator 12 increases, the governor 69 increases the pressure level in the circuit bv means known per se and this causes the pistons 30, 31 to move to the right and actuate the cams 36 and 37 to force the push rods 42, 43 upwards. The rod 42 operates a slide valve 49 which allows pressure oil to leak from the servo-motor 53 and open the fuel valve 58. This results in an increase in pressure in the pipe 62 which operates on a spring loaded piston 50 to return the valve 49 to its neutral position. The rod 43 operates a slide valve 51 which controls a servo-motor 54. The servo-motor decreases the value of the variable resistance 66 and this increases the speed of the motor 23 so that more air is supplied to the heater 1. The pressure drop across an orifice 15 is used to restore the valve 51 to its neutral position. In the event of a sudden decrease in load the regulator opens the byepass valve 13. This causes the pressure in the pipe 5 to increase and that in the pipe 10 to fall. The piston 30 then moves to the right and the piston 31 to the left and this causes the lever 34 to rotate clockwise and move the rod 35 and cams 36 and 37 to the left. This causes a decrease in the fuel and air supplies to the heater 1. A temperature regulator 46 responsive to the temperature at the inlet of the turbine 4 also ,acts on the governor valve 58 and variable resistance 66. As shown the fuel valve servo-motor 53 operates the resistance 61 of the motor of the circulating fan 27 but if desired, this resistance may be operated by the servo-motor 54 or by both servomotors conjointly: In a modification in which there are two turbines in the circuit with reheating between them, one of which drives the compressor and the other supplies useful power, the controlling pressures are taken from three points respectively located before the high pressure tubine, between the turbines, and after the low pressure turbine. The first two pressures are used conjointly to control the fuel supply to the heater and the second two to control the fuel supply to the reheater. In this arrangement, the exhaust gases from the reheater are used as combustion air in the heater so that it is only necessary to control one air supply. The variable resistance 61 in this case is controlled by two pistons responsive to the pressure at the inlet to the high pressure turbine and the pressure at the exhaust of the low pressure turbine. The fuel valves are also controlled by regulators responsive to the temperature at the inlet to the high pressure and low pressure turbines. In both arrangements the control may be used to regulate the quantity of combustion air only, the quantity of fuel being regulated in accordance with the variations of the quantities of combustion air. If desired, the temperature regulators may be influenced by the temperatures of the tubes in which the working medium is heated or temperatures of the combustion chamber walls. The plant is started by energizing the motor 23.