Patent GB-620748-A (GB)
Title: Improvements in or relating to gas turbine plants
Filed: 1945-06-11
Abstract: 620,748. Fluid-pressure servomotor-control systems. SULZER FRERES SOC. ANON. June 11, 1945, No. 14736. Convention date, June 17, 1944. [Class 135] [Also in Group XXVI] A gas-turbine plant of the type in which the working medium flows in a circuit from which circuit some of the working medium is continuously extracted and to which a make-up quantity is continuously introduced, at least one turbine driven by the working medium flowing in the circuit and at least one other turbine driven by the working medium extracted from the circuit, has a regulator influenced by the pressure at a point in the circuit which controls the extraction of the working medium from the circuit so that the pressure at said point is equal to the value at which the regulator is set. In a gas-turbine plant, Fig. 1, the working fluid flows around a circuit formed by low and high compressors 1, 3, a heat exchanger 5, an air heater 11 and a compressor turbine 13. Some of the working fluid is taken from the circuit at the point 8 and used as combustion air for the burner 19 in the combustion chamber 10, the gases from which pass through the heater 11 to the useful output turbine 22. The amount of working fluid taken from the circuit and thus the amount flowing to the two turbines 13 and 22 is controlled by a valve 30 in a pipe 29 byepassing some stages of the turbine 22. The setting of the valve 30 is adjusted by the regulating device 33 which is influenced by a load setting lever 35 and the pressure in the inlet pipe 12 to the compressor turbine. When running under steady conditions, the plant is controlled solely by the pressure in the pipe 12. This pressure may be pre-set, according to the output required, by the lever 35. When the operation of the valve 30 is not sufficient to control the pressure in the pipe 12 the regulating device 33 may open the valve 37 in the pipe 36 byepassing some stages of the compressor turbine 13 so altering the output of the compressors 1, 3. A regulating device which enables these operations to be effected is shown in Fig. 2. Movement of the bellows 40 due to variations of pressure in the pipe 12 moves the lever 42 which allows pressure oil to be supplied above or below the piston 53 which moves and compresses or tensions the spring 56. This causes the piston 57 to move and allow pressure oil to be supplied to or released from the pipe line 32 from the pipes 61, 62. This will continue until the oil pressure on the piston 57 balances the tension or compression in the spring 56 when the piston will move and cut out one or other of the ports. An increase in the pressure in the pipe line 32 will close the valve 30 and open the valve 37. The springs 66 and 69 are of such dimensions that the valve 37 is only opened when the valve 30 is fully closed. The movement of the piston 53 acting on the lever 42 through the dash-pot 55 cuts off the supply of pressure oil to its cylinder 52 and this prevents over-regulation. The regulator is only in a neutral position when the spring 46 is unstressed and the pilot valve 49 closes off the pipe lines 74, 75, so.that for each pressure in the pipe line 12, i.e. position of the bellows 40 there is a definite position for the lever 42. The dash-pot 55 allows this position to be taken up when the main regulating process has ceased. The position of the pivot 43 of the lever 42 when the spring 46 is unstressed can be pre-set by the lever 35 through the cam 44. Since for each position of the pivot 43, there is a position of the pivot 41 actuated by the bellows 40 which will maintain the valve 49 in the neutral position, alteration of the position of the pivot 43 will cause an increase or decrease in the pressure maintained in the pipe line 12 by the bellows 40. Specification 597,337 is referred to.