GB845013A - Regulation of thermal power plants - Google Patents

Abstract

845,013. Fluid-pressure servomotor control systems. SULZER FRERES S.A. Feb. 5, 1957 [Feb. 15, 1956], No. 3993/57. Class 135. A thermal power plant, such as a steam generator or a gas turbine plant, has devices for regulating operating variables of the plant whereby during steady state operation the variables are maintained at values corresponding to the load on the plant, means for adjusting the datums of the regulating devices individually or in groups in response to variations of load on the plant, and means for controlling the rate of datum adjustment whereby such adjustment commences gradually and does not reach its final value before the dying away of the oscillations in the value of an operating variable consequent upon a change of load. Fig. 3b illustrates the oscillations in the value of an operating variable consequent upon both a small change of load (full line) and a large change (dotted line), and Fig. 3c shows the corresponding datum adjustment curves. In the plant shown in Fig. 4 a steam generator 1 supplied by a feed-water pump 22 and having economizer, evaporator and superheater coils supplies a turbine 19 through a conduit 96 provided with a bypass valve 59 having an outlet leading to a condenser, a pressure-regulating valve 60, and a turbine inlet valve 15 controlled by a governor 7 driven by the turbine. The feed pump 22 is driven by an electric motor 36 having a controller 38 which is adjusted by a servomotor 39 under the control of an hydraulic amplifier 41 and of a datum adjuster 17 to which it is connected by a conduit 44. The hydraulic amplifier 41 is controlled by a device 43 which is sensitive to the temperature at the outlet of the evaporator section of the generator. An attemperator, which injects water into the superheater section, consists of a pump 45 driven by an electric motor 47 having a controller 49 which is actuated by a servomotor 50 under the joint control of a device 51 sensitive to the temperature at the outlet 94 of the superheater and of the datum adjuster 17. Fuel and air controls 57, 58 are adjusted by a servomotor 55 controlled by a device 56 sensitive to steam pressure and also by the datum adjuster 17. The device 56 and the datum adjuster 17 also act on the control valve 84, Fig. 5, of a servo-piston 81 which adjusts the by-pass valve 59. The pressure-regulating valve 60 is actuated by a servo-piston 87 under the control of valves 86, 90 which are responsive, respectively, to the datum adjuster 17 and to the temperature-sensitive device 51. In a modification, the valve 60, instead of being temperature responsive, is subject to the same controls as the valve 59, and the fuel and air controls are governed by the pressure downstream, rather than that upstream, of the valves 59, 60. The datum adjuster 17 consists of a cam shaft 67 controlling valves 73 connected to the parts of the apparatus whose datums are to be adjusted and having a connection 66 either directly or through an electrical transmission with an output member 34 of a load-measuring device 5 connected to the steam pipe before the turbine 19. Between the member 34 and the device 5 are a pair of dashpots 30, 32 interconnected by springs which cause the datum adjustment consequent upon a change of load to be initiated gradually. It is stated that the datum adjustment may be effected manually.