GB885643A - Dynamic steam cycle - Google Patents

Abstract

885,643. Steam power plants. AMERICAN MACHINE & FOUNDRY CO. Feb. 11, 1958 [March 15, 1957], No. 4451/58. Class 122 (3). A steam power plant comprises means for dynamically compressing wet steam, means for superheating the compressed steam and expanding it to do work including that required for the dynamic compression, and means for increasing the weight flow of the wet steam by injecting therein during its compression a mixture of water and partially expanded superheated steam in the form of wet steam. In the variable speed plant shown in Fig. 6, two compressors C 1 and C 2 arranged in series are driven by turbines Tu 2 and Tu 1 respectively and a power turbine Tu 3 drives a load 619. Wet steam G 1 , of the order of 0.65-0.75, is compressed in compressor C 1 and discharged to a steam regulator F 1 and heat exchanger M 1 where it is mixed with part G 6 of the exhaust from turbine Tu 1 and with preheated water G 7 to produce a flow G 2 of steam having the same wetness quality as the steam G 1 entering compressor C 1 . The steam G 2 is compressed in compressor C 2 , superheated in heater H 1 , expanded in turbine Tu 1 and then divided into two streams G 3 , G 6 ; the latter passing to the regulator F 1 and the former being further divided into two streams G 4 and G 5 respectively superheated in heaters H 2 and H 3 and then expanded in turbines Tu 2 and Tu 3 . The exhaust from these turbines is mixed with water G 8 in a mixer M 2 under the control of regulator F 2 to produce steam G 11 of the same quality as G 1 , part G 1 of the steam G 11 being drawn into the compressor C 1 and the remainder G 10 being condensed in condenser 622 and passed to the hot well W. Water G 7 and G 8 is pumped from the hot well W to the regulators F 1 and F 2 respectively by a pump P, G 7 being preheated in heater 637 by exhaust from the turbine Tu 2 . Fig. 7 illustrates a manually operated hydraulically actuated control system for the plant of Fig. 6 and includes a manually operated valve 700 that is supplied through a duct 715 with oil under pressure by a pump 716 and controls the supply of pressurized oil to valves 724, 751, 759 and 755 and actuators 728 and 750 through ducts 720, 721, 722, 723 and 740. Valves 724 and 751 control the fuel to heaters H 1 and H 2 respectively and comprise needles 727, controlled through actuators 728 and 750 by devices 729 and 752 sensitive to the inlet temperatures T 5 and T 7 of turbines Tu 1 and Tu 2 respectively, and spring-loaded seats 726 movable away from the needles by oil pressure. As the load decreases from full load the inlet temperature T 11 of turbine Tu 3 decreases, T 7 increases until it equals T 11 and then decreases, and T 5 remains constant until the exhaust temperature T 6 of turbine Tu 1 equal T 11 after which it decreases with decrease in load. Valves 751, 755 and 759 are closed by their springs at no load. Valves 770 and 771 are safety valves operated to close by the turbine governors 780 and 781 in the event of overspeeding. Many modified plant arrangements designed for constant or variable speed are shown and described. Such modifications include (a) bleeding the steam flow G 6 from a stage of the turbine Tu 2 ; (b) driving the load and either compressor C 1 or compressor C 2 by the turbine Tu 2 ; (c) four turbines and three reheat stages; (d) three stages of compression with the steam returned to its original wetness between the first and second and between the second and third stages. Control systems for the modified plants are described and Mollier diagrams are given for the cycles involved when operating at full load, part load or no load. Types of steam compression and expansion are discussed with the aid of Mollier diagrams. The invention is stated to be particularly suitable for atomic energy steam power plants and preferably centripetal flow compressors and centrifugal turbines should be used.