Patent GB-584479-A (GB)
Title: Improvements in or relating to gas-turbine plants
Filed: 1944-12-21
Abstract: 584,479. Gas-turbine plant. STRUB, R. Dec. 21, 1944, No. 25639. Convention date, Dec. 23, 1943. [Class 110 (iii)] [Also in Group XXIX] In a gas turbine plant of the type in which the working medium flows in a circuit from which some of the medium is continuously extracted and in its place a make-up quantity supplied, and in which there is at least one turbine operated by the medium flowing in the circuit and at least one turbine operated by the medium extracted from the circuit, the governor of the circuit turbine varies the rate of extraction of the working medium from the circuit. In one arrangement, the sleeve of the governor of the circuit turbine is connected through linkwork to the admission valve of the extraction turbine. In another arrangement, Fig. 3, the governor 26 of the circuit turbine operates the valve 34 which controls the amount of working medium flowing from the extraction turbine supply pipe 18 into the pipe 35 which bye-passes the first stage of this turbine. An alteration in speed of the circuit turbine causes the sleeve 57 of the governor 26 to alter the position of the control valve 51 of the servomotor 36 and allows pressure oil to be supplied to the upper or lower side of the piston 60 which moves the valve 34 through the linkwork 61, 62. More or less working medium flows to the extraction turbine and the circuit turbine speeds up or slows down and the sleeve 57 and control valve 51 return to the original positions. To allow this to be effected without altering the new position of the valve 34 and to prevent over regulation, the sleeve 57 is connected to the piston 60 by an isodromic device comprising a spring 53 and dashpot 52. This device can only come to rest when the lever 54 is in a position in which the control valve 51 is in a neutral position and the spring 53 unstressed, i.e., when the governor is at the normal speed required. During controlling movements, the piston 60 and the piston 63 of the dashpot 52 are moved. This causes a pressure to be built up on one side of the piston 63 and the outer casing of the dashpot moves and stresses the spring 53. As oil leaks through the hole 64 this pressure difference decreases until there is no stress in the spring. The speed at which the governor 26 controls can be pre-set by moving the position of the fulcrum 58, by means of the lever 65. The governor of the extraction turbine 45 is connected to a servomotor which, under normal conditions, allows pressure oil to flow from the supply pipe 69 through the pipe 70 to the upper side of the pistons 71, 72 controlling the valve 46 in the supply pipe 18 and the valve 42 in the pipe 40 which byepasses the whole of the extraction turbine. Normally, the valve 46 is fully open and the valve 42 fully shut. In the event of overspeeding of the extraction turbine, its governor 45 moves the servomotor piston 68 which connects the pressure oil supply to the pipe 74 and opens the pipe 70 to drain. The pressure oil is then supplied to the lower sides of the pistons 71, 72 which move and fully close the valve 46 and open the valve 42. The amount by which the valve 42 is opened is limited by a piston 75, the position of which is controlled by the governor of the circuit turbine so that the amount of working fluid flowing through the bye-pass 40 is equal to the amount previously flowing through the extraction turbine. Operation of the governor 45, therefore, does not affect the speed of the circuit turbine. The circuit turbine may be provided with an electric motor for starting purposes and the closed circuit may be provided with air preheaters to increase the efficiency of the plant. The circuit turbine or the extraction turbine may be used to provide the useful power.