Improvements in and relating to Multi-Stage Pump Units and Pump Turbine Units of Radial Flow Construction in Pumped Storage Power Stations

1,184,824. Starting centrifugal pumps. SULZER BROS. Ltd. March 21, 1967 [March 24, 1966], No.13120/67. Heading F1C. A multi-stage pump or pump-turbine of radial flow type with fixed impeller blades in a pumped storage power plant includes means for admitting compressed air to the machine to drive out water, and at least one opening upstream of the first impeller relative to the direction of flow to the inlet of the machine for the release of air from the machine, the opening leading to flow control means including a throttle for controlling flow through the opening. Water is driven out of the machine shown in Fig. 3, prior to starting it as a pump, by admitting compressed air from a line 21 via a shut-off valve 23, a pipe 20, an annular manifold 19 and openings 18. The machine is then accelerated by an auxiliary machine to the synchronous speed of the main electrical machine, which is already connected to the mains. The valve 23 is then closed and a shut-off valve 25 is opened to allow the compressed air to escape via the openings 18, the pipe 20 and a line 22. The rate of escape is controlled by an adjustable throttling diaphragm 24 so that the rate of increase of power consumption as the air is replaced by water does not exceed 5% of the full output per second, whereby a sudden large increase of power consumption is avoided. It is found that the compressed air escapes not continuously but in surges, apparently due to the openings 18 being temporarily at least partially closed by the water flowing into the machine from the inlet line 17. When the machine has been filled with water, a shut-off valve 15 in the delivery line is opened and pumping commences. The time taken to fill the machine can be reduced by opening a shut-off valve 27 at the same time as the valve 25 so that water from a line 26 can also flow into the machine downstream of the first impeller 4 under the control of an adjustable throttling diaphragm 31. The valves 23, 25, 27 and 15 may be controlled automatically in accordance with a predetermined programme, and the automatic control means may receive an input signal from a device sensitive to the speed of the shaft 1 or to synchronization of the main electrical machine. The pump or pump-turbine may be of double-entry type and may have a vertical shaft. The manifold 19 and openings 18 may be located upstream of the inlet volute 29.