GB873651A - Improvements relating to sealing devices - Google Patents

Abstract

873,651. Stuffing-box substitutes; engine stop-gear; gas-turbine plant. ROLLS-ROYCE Ltd. March 18, 1960 [March 25, 1959], No. 10353/59. Classes 110 (3), 122 (4) and 122 (5). The failure of seals 17, 18, Fig. 3, which allow a restricted flow from a high-pressure region 14, forming part of a duct communicating with a supply means, to a low-pressure region is detected by a control device 20, Fig. 2, comprising a pressure-responsive member 23 opposite faces of which are respectively subjected to the pressure in the high pressure region (which is dependent upon the effectiveness of the seals) and the pressure at the supply means or to pressures functionally related thereto and which is adapted to operate a device to indicate failure of the seal and/or control operation of the apparatus. The invention is shown incorporated in a gas-turbine comprising a high-pressure stage 16, 19, and two low-pressure stages 51, 64 and 53, 65. Cooling air from a compressor is supplied through the duct 14 to cool the turbine disc 16 and passes through seals 17, 18 to seal the hot gas stream passing the turbine blade 19. The seals may be of the labyrinth type or of the self-clearing type in which, when its stator and rotor components touch, clearing occurs by expansion caused by frictional heating. Failure of either or both of these seals would cause a drop in pressure of the cooling gas and allow the hot gases from the turbine to overheat the turbine disc. The control device 20 has chambers 21, 22 separated by a diaphragm 23 and supplied through pipes 26, 24 with gas from, respectively, the delivery side of the compressor and the part of the duct 14 adjacent the seals. The pipe 26 incorporates a restriction 27 to reduce the pressure in chambers 25, 21 to one suitable for operation of the diaphragm 23. The chamber 25 communicates by way of a restriction 30, closable by a solenoid-operated member 33 for testing purposes, with a chamber 31 connected by a pipe 32 to the jet pipe of the gas-turbine or a vent. Upon failure of a seal, the pressure in the chamber 22 drops and the diaphragm urges contacts 42, 43 to make and so close the circuit 45 which may incorporate a warning lamp 46 and/or equipment adapted to operate a pneumatic servomotor to shut down the engine; the device 20 is arranged to give warning of seal failure before such failure results in the in-flow of hot gases. The cooling stream to the discs 51, 53 is provided with seals 50, 52 which are similar to the seal 17 and are arranged. upon failure to light the lamp 46, or a number of control devices may be provided, each connected by a pipe 24 to aposition adjacent the respective seal. Cooling air which has passed through the seals 50, 52 passes via seals 60, 63 into the hot gas stream. The seals 17, 18 instead of controlling the flow of cooling air on to the turbine blades may also or alternatively be used on the front and centre bearings of a gas-turbine engine.