Patent GB-904967-A (GB)
Title: Turbine apparatus
IPC: F01D13/00
Filed: 1961-06-27
Abstract: 904,967. Fluid-pressure servomotor-control systems. WESTINGHOUSE ELECTRIC CORPORATION. June 27, 1961 [Aug. 11, 1960], No. 23223/61. Class 135. [Also in Group XXVI] The invention relates to a system for con-  trolling the acceleration of an elastic-fluid turbine power plant having a plurality of turbine units driving separate power output shafts. The plant shown comprises a first turbine group 11 driving an electric generator 15, and a second turbine group 17 driving an electric generator 20, the first turbine group comprising a highpressure steam turbine 12 and a low-pressure steam turbine 13 of the double-flow type mounted in tandem on a common shaft 14. The second turbine group comprises an intermediate pressure steam turbine 18 of the double-flow type and a low-pressure steam turbine 19 also of the double-flow type, mounted in tandem on a common shaft 22. High pressure steam from the steam boiler 35 flows through line 34 to the H.P. turbine 12, the steam discharging therefrom passing through line 36 to the inlet of the I.P. turbine 18. Steam discharging from the outlet 31 of the I.P. turbine passes through line 40 to the inlet of the L.P. turbine 13, the steam discharging therefrom through outlets 26. Steam discharging from the outlet 32 of the I.P. turbine passes through line 41 to the inlet of the L.P. turbine 19, the steam discharging therefrom through outlets 29. A control system is provided for effecting joint acceleration of the first and second turbine groups at the same rate during starting thereof, the control system comprising a second line 65 for conveying high pressure steam direct from the steam generator 35 to the inlet of the I.P. turbine 18, a valve member 67 being disposed in the line 65 which is movable to either the closed position as shown, or to the open position. A control device is connected to the valve 67 and comprises a piston 71 connected to the valve by means of a rod 70, the piston being disposed within a chamber which provides space 74 above the piston and space 75 below the piston. A spring 73 acts against the piston to move the valve 67 to the open position. High-pressure fluid is supplied through line 76 to the space 75 below the piston, also through line 77 to the space 74 above the piston, the line 77 also being connected by line 79 to an outlet 81 which is controlled by a cupshaped valve 82. The valve 82 is connected to the piston 87 of a differential pressure-regulator device 83. A pump device 48 is driven by the turbine group 11 so as to generate a fluidpressure which is proportional to the rotational speed of the turbine group, the pressure fluid passing through line 53 to a governor device 47, also through line 89 to the space 86 below the piston 87. A similar pump device 49 generates a fluid pressure proportional to the speed of the turbine group 17, the pressure fluid passing through line 55 to the governor 47, also through line 88 to the space 85 above the piston 87. At starting, the pressures developed by the pump devices 48, 49 will be substantially equal and of low value, so that high-pressure fluid in the line 79 will force the cup valve 82 downwardly and no pressure will be built up in the space 74 above the piston 71 and so high pressure fluid in the space 75 below the piston will move the piston upwardly against the loading of spring 73 and so move the valve 67 to close the high-pressure steam line 65 to the I.P. turbine. The turbine group 11 tends to accelerate at a greater rate than the group 17 at starting so that the pressure generated by the pump device 48 is greater than that generated by the device 49. The pressure transmitted to the space 86 below the piston 87 therefore exceeds that transmitted to the space above the piston, and therefore the piston moves upwardly and the cup valve 82 closes the outlet 81. The pressure in tne space 74 above the piston 71 accordingly increases, the piston moves downwardly and so opens the valve 67 whereby high-pressure steam passes through line 65 to the inlet of the I.P. turbine 18. The turbine group 17 therefore accelerates at a greater rate than it would otherwise have done. Increasing speed of the turbine group 17 causes the pump device 49 to generate a greater fluid pressure which acting through line 88 to the space 85 above the piston 87 acts to re-open the outlet 81 and so tends to re-close the valve 67. The exciters 16, 21 may be connected to their associated generators 15, 20 by an excitation control mechanism 92 when the speed of the generators is about 50% of the rated speed. A spring-loaded relief valve 93 is disposed in the pressure fluid line 89 from the pump device 48 so that as the speed of the turbine group 11 exceeds 50% of the rated speed, the fluid-pressure acts to open the valve 83. A cut-off valve 96 may be provided in the line 89 as well as the relief valve 83. The speeds of the two turbine groups is indicated on a device 97, the device being responsive to fluid-pressures generated by the pump devices 48, 49.