Patent GB-250548-A (GB)
Title: Improvements relating to elastic fluid turbines
IPC: F01D17/00
Filed: 1926-03-05
Abstract: 250,548. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Bryant, O. N.). April 11, 1925, [Convention date]. Fluid governors; fluid relays.-A turbine 10 having an extraction or bleeder connection 13, Fig. 1, which may alternatively serve as an inlet pipe in a mixed-pressure turbine, is provided with responsive devices 24, 26 for controlling the main inlet valve 11 and the interstage valve 12, the control devices being supplied with fluid from a centrifugal pump 27, which is driven by the turbine and has a delivery pressure depending on the speed thereof, further control being imposed by a device 68 responsive to changes in the extraction pipe pressure. The control device 24 for the valve 11 comprises a piston 39 with stem portions 43, 44. ports 53, 54, and a pilot valve 41 with ports 56 adapted at times to register with the ports 53 and admit pressure fluid, which is supplied by a pump 27 and a pipe 29, to the upper side of the piston, thereby forcing it downwards. The pilot valve 41 has also a reduced portion 57 adapted at times to pass fluid from the upper side of the piston to the exhaust pipe 33, thereby causing the piston to move upwards. A shoulder 58 when registering with the ports 53 traps fluid above the piston, which is thus held stationary. A spring 52 has its tension adjusted to hold the valve 41 stationary at normal pump speed, that is, at normal turbine speed. The action of the governor 24 is modified by a variable back pressure imposed upon the pilot valve 41. Fluid escaping through an orifice 51 in this valve passes into a chamber 63 which communicates with the device 68 through a pipe 64. The device 68 comprises a valve 71 controlling the fluid escape to a drain 72, and the amount of fluid passing this valve 71 is determined by the pressure in the extraction pipe acting through a diaphragm 79 on a lever 76 having a fulcrum 78. The vertical position of the fulcrum 78 determines the spring pressure on the relief valves 71, 112, and may be adjusted by a motor 122 actuating a lever 116 through screw members. The valve 112 provides a similar but rerversely-acting control for the back-pressure on the piston valve 88 controlling the piston 86 which actuates the inter-stage valve 12. This valve 88 is subjected on its underside to the variable fluid pressure developed by the pump 27 and supplied by a conduit 29, and adjustable tensioning and positioning devices 124, 126 are applied as shown. With the described control, should the pressure in the extraction pipe fall below that normally required, the steam supply to the turbine is increased and the flow of steam to the low-pressure sections is decreased, thus increasing the supply to the extraction pipe. An increase in turbine speed results in the throttling of the inter-etage valve 12 simultaneously with the throttling of the admission valve 11 and no decrease in the extraction pipe pressure. Fig. 4 shows a turbine 128 of the extraction pipe fitted with the described controls 24, 26, and supplied with steam from a pipe 137 in parallel with two other turbines 129, 131 fitted with controls 24, all three turbines driving generators and exhausting into a. pipe 138. If desired, exhaust steam from turbines 144, 146 driving auxiliary mechines may be led through pipes 148, 151, and the extraction pipe 152 to the turbine 128, which then acts as a mixed-pressure turbine.