Pattern-abradable/abrasive coatings for steam turbine stationary component surfaces

Abstract

A pattern-abradable seal assembly is provided for a stationary steam turbine component. The seal assembly, in use, is oriented in opposition to at least one seal tooth on a rotatable turbine component so as to inhibit leakage flow across the seal assembly in one direction, the seal assembly may include an annular seal carrier having at least one axially-oriented surface; a pattern-abradable/abrasive seal coating or insert at least partially covering the at least one axially-oriented surface, the pattern-abradable/abrasive seal coating having a pattern formed thereon adapted to face and be at least partially penetrated by the at least one seal tooth. A plurality of anti-swirl elements project radially beyond the pattern and are arranged to provide at least an axial component of flow across the abradable seal assembly. The coating or insert may also be used on other stationary turbine component surfaces to direct flow in a predetermined direction.

1 . A pattern-abradable/abrasive seal assembly for a stationary steam turbine component, the seal assembly, in use, oriented in opposition to at least one seal tooth on a rotatable steam turbine component so as to inhibit leakage flow across the seal assembly and/or guide the leakage flow in a first direction, the seal assembly comprising:
 an annular seal carrier having at least one axially-oriented, annular seal surface;   a pattern-abradable/abrasive seal coating at least partially covering said at least one axially-oriented, annular seal surface, said pattern-abradable/abrasive seal coating having a pattern formed therein, adapted, in use, to face and be at least partially penetrated by the at least one opposed seal tooth; and   a plurality of anti-swirl elements projecting radially beyond said pattern and arranged circumferentially about said at least one axially-oriented, annular seal surface.   
     
     
         2 . The pattern-abradable/abrasive seal assembly of  claim 1  wherein the abradable seal coating comprises a ceramic material or a metal alloy. 
     
     
         3 . The pattern-abradable/abrasive seal assembly of  claim 1  wherein said pattern has a depth of from about 50 to 100% of a total thickness of said abradable seal coating. 
     
     
         4 . The pattern-abradable/abrasive seal assembly of  claim 1  wherein said plurality of anti-swirl elements comprise a first plurality of substantially rectangular blocks, aligned and spaced about one circumferential edge of the said annular seal carrier, axially spaced from said at least one seal tooth, said rectangular blocks arranged at an acute angle relative to an axial centerline passing through said annular seal carrier. 
     
     
         5 . The pattern-abradable/abrasive seal assembly of  claim 4  wherein said plurality of anti-swirl elements further comprise a second plurality of substantially rectangular blocks, aligned and spaced about an opposite circumferential edge of said annular seal carrier, said second plurality of said rectangular blocks arranged at substantially the same acute angle as said first plurality of substantially rectangular blocks. 
     
     
         6 . The pattern-abradable/abrasive seal assembly of  claim 1  wherein said plurality of anti-swirl elements comprise three or more axially-spaced, circumferential rows of substantially rectangular blocks. 
     
     
         7 . The pattern-abradable/abrasive seal assembly of  claim 1  wherein said plurality of anti-swirl elements comprise plural, circumferentially-staggered rows of substantially rectangular blocks. 
     
     
         8 . The pattern-abradable/abrasive seal assembly of  claim 1  wherein said pattern comprises a criss-cross mesh pattern. 
     
     
         9 . The pattern-abradable/abrasive seal assembly of  claim 1  wherein said pattern comprises a plurality of substantially rectangular brick-shapes. 
     
     
         10 . The pattern-abradable/abrasive seal assembly of  claim 7  wherein said rectangular blocks are oriented in an axial direction. 
     
     
         11 . A stationary steam turbine component located along a gas path comprising: a first surface facing an adjacent rotating steam turbine component; and a first pattern-abradable/abrasive coating or insert having a pattern formed therein applied to said surface wherein said pattern is designed to direct leakage flow in a predetermined direction relative to said stationary steam turbine component. 
     
     
         12 . The stationary steam turbine component of  claim 11  wherein said stationary steam turbine component comprises a turbine vane or nozzle and said rotatable steam turbine component comprises a turbine bucket. 
     
     
         13 . The stationary steam turbine component of  claim 12  wherein said turbine vane nozzle is located axially upstream of said turbine bucket. 
     
     
         14 . The stationary steam turbine component of  claim 12  wherein said turbine vane or nozzle is located axially downstream of said turbine bucket. 
     
     
         15 . The stationary steam turbine component of  claim 12  wherein said turbine bucket is formed with a tip shroud supporting on or more radially-outwardly directed seal teeth, and a stationary stator surface surrounding said tip shroud is provided with a second pattern-abradable/abrasive coating or insert facing said one or more radially outwardly directed seal teeth. 
     
     
         16 . The stationary steam turbine component of  claim 15  and wherein said second pattern-abradable/abrasive coating includes one or more anti-swirl features projecting radially beyond said pattern abradable/abrasive coating or insert. 
     
     
         17 . A turbine bucket and abradable seal assembly comprising:
 a bucket having a tip shroud formed with plural radially-directed seal teeth;   a stationary stator component surrounding said bucket and having plural abradable seals opposing respective ones of said plural radially-directed seal teeth; wherein each of said plural abradable seals includes an abradable seal coating having a pattern formed on a surface thereof facing a respective one of said plural, radially-directed seal teeth, and at least one an anti-swirl element projecting radially beyond said pattern and arranged to provide at least an axial component of flow across the seal assembly, said at least one anti-swirl element opposed to one of said plural radially-directed seal teeth, and adapted to be at least partially penetrated thereby.   
     
     
         18 . The turbine bucket and abradable seal assembly of  claim 17  wherein said at least one anti-swirl element comprises plural circumferentially-arranged rows of anti-swirl elements. 
     
     
         19 . The turbine bucket and abradable seal assembly of  claim 18  wherein said plural circumferentially-arranged rows of anti-swirl elements are axially-spaced and staggered in the circumferential direction. 
     
     
         20 . The turbine bucket and abradable seal assembly of  claim 18  wherein each anti-swirl element of said plural circumferentially-arranged rows of anti-swirl elements is arranged at an acute angle to an axis of rotation of said bucket.