Sealing arrangement in turbine machinery

Abstract

A sealing arrangement in a steam turbine is deployed in a position where it can restrict flow of steam along a flowpath in a gap between two bodies of the turbine rotatable relative each other, the flowpath proving communication between a space of relatively high pressure and another of relatively low pressure. The sealing arrangement comprises a leaf seal mounted on one of the bodies and sealingly engaged with the other. Two or more leaf seals can be juxtaposed with each other, without need for labyrinth seals, in a steam turbine application, without deleterious effects experienced in use of brush seals in similar circumstances. The sealing arrangement can include segments displaceable from a sealing position to increase clearance during start-up of a turbomachine, thereby taking account of potential vibration problems as the turbine rotor passes through natural frequencies.

1 . A steam turbo machine comprising a stator and a rotor rotatable with respect to the stator, for receiving an inlet flow of steam for driving the rotor, wherein opposing circumferential surfaces of the stator and rotor define between them a gap capable of enabling fluid communication between a space of said machine of relatively high pressure in use to a space of relatively low pressure in use, the gap being sealed by a sealing arrangement, wherein the sealing arrangement is a leaf seal.  
   
   
       2 . A machine according to  claim 1  wherein said rotor includes a balance piston, for maintaining a compensating force with respect to the reaction of the rotor against the inlet steam in operation, said balance piston having a circumferential surface which defines, with an opposing circumferential surface of the stator, said gap between a space which, on operation of the turbine, is at a relatively high pressure and a space which, on operation of the turbine is at a relatively low pressure, a sealing arrangement being interposed in said gap and wherein said sealing arrangement is a leaf seal.  
   
   
       3 . A machine according to  claim 1  wherein said relatively high pressure is a steam inlet pressure at a steam inlet of the steam turbine machine.  
   
   
       4 . A machine according to  claim 1  wherein said relatively low pressure is an exhaust pressure at a steam exhaust of said steam turbine machine.  
   
   
       5 . A machine according to  claim 1  wherein said rotor has an external circumferential surface, and said stator has an internal circumferential surface, developed around the axis of rotation of said rotor, and a turbine chamber is defined between said surfaces, said rotor having a plurality of substantially radially extending turbine blades, configured to present a surface against which said inlet flow of steam reacts in use to generate a torque acting on said rotor relative said stator, each of said turbine blades extending radially to adjacent said inner surface of said stator, so as to define a gap in which a sealing arrangement is interposed, said sealing arrangement being a leaf seal.  
   
   
       6 . A machine according to  claim 5  wherein said stator has a plurality of inwardly substantially radially extending turbine blades configured to direct, in operation of said turbine, said inlet flow onto said turbine blades of said rotor to cause said torque to be developed in use, wherein each of said stator turbine blades extend radially to adjacent said external surface of said rotor and thereby defining a gap in which a sealing arrangement is interposed, said sealing arrangement comprising a leaf seal.  
   
   
       7 . A machine according to  claim 1  wherein the rotor comprises opposing and coaxial mounting means for cooperation with corresponding formations of said stator, said mounting means and formations each having opposing adjacent circumferential surfaces defining a gap in which a sealing arrangement is interposed, wherein said sealing arrangement is a leaf seal.  
   
   
       8 . A machine according to  claim 1  wherein said sealing arrangement comprises two leaf seals, interposed in said gap.  
   
   
       9 . A machine according to  claim 1  wherein the or each leaf seal comprises a plurality of leaves extending from one of the rotor and stator across said gap towards the other of the rotor and stator.  
   
   
       10 . A machine according to  claim 1  wherein said sealing arrangement comprises a plurality of support segments, circumferentially arranged about the gap, each support segment presenting a leaf seal in said gap, each segment being radially displaceable in said gap, wherein said sealing arrangement further comprises resilient means for urging said segments into an initial position displaced away from a sealing position, said segments are arranged to be urged into said sealing position by a reaction force developed in use through high pressure in said high pressure region of said turbine machine.  
   
   
       11 . A method of sealing a gap in a steam turbomachine between a region of relatively high pressure and an area of relatively low pressure, between relatively rotatable members of said turbomachine, said method comprising interposing a leaf seal in said gap, mounting said seal on one of said members and directed sealingly at a surface defined on the other of said members.  
   
   
       12 . A steam turbine machine substantially as described herein with reference to FIGS.  1  to  3  of the accompanying drawings.  
   
   
       13 . A steam turbine machine substantially as described herein with reference to  FIG. 4  of the accompanying drawings.  
   
   
       14 . A method of sealing a gap in a steam turbomachine substantially as described herein with reference to FIGS.  1  to  3  of the accompanying drawings.  
   
   
       15 . A method of sealing a gap in a steam turbomachine substantially as described herein with reference to  FIG. 4  of the accompanying drawings.