Turbine bucket shroud arrangement and method of controlling turbine bucket interaction with an adjacent turbine bucket

Abstract

A turbine bucket shroud arrangement for a turbine system includes a contact region of a tip shroud, wherein the contact region is in close proximity to an adjacent tip shroud. Also included is a negative thermal expansion material disposed proximate the contact region, the contact region comprising a first volume during a startup condition and a shutdown condition of the turbine system and a second volume during a steady state condition of the turbine system, wherein the second volume is less than the first volume.

1 . A turbine bucket shroud arrangement for a turbine system comprising:
 a contact region of a tip shroud, wherein the contact region is in close proximity to an adjacent tip shroud; and   a negative thermal expansion material disposed proximate the contact region, the contact region comprising a first volume during a startup condition and a shutdown condition of the turbine system and a second volume during a steady state condition of the turbine system, wherein the second volume is less than the first volume.   
     
     
         2 . The turbine bucket shroud arrangement of  claim 1 , wherein the negative thermal expansion material comprises at least one of zircon, zirconium tungstate and an A 2 (MO 4 ) 3  compound. 
     
     
         3 . The turbine bucket shroud arrangement of  claim 1 , further comprising an adjacent contact region of the adjacent tip shroud. 
     
     
         4 . The turbine bucket shroud arrangement of  claim 3 , wherein the adjacent contact region comprises a negative thermal expansion material. 
     
     
         5 . The turbine bucket shroud arrangement of  claim 1 , wherein the contact region comprises a composition of the negative thermal expansion material and a wear resistant material. 
     
     
         6 . The turbine bucket shroud arrangement of  claim 5 , wherein the composition comprises a layer disposed on a base metal of the tip shroud. 
     
     
         7 . The turbine bucket shroud arrangement of  claim 5 , wherein the composition comprises a plurality of layers disposed on a base metal of the tip shroud. 
     
     
         8 . The turbine bucket shroud arrangement of  claim 7 , wherein each of the plurality of layers comprise a distinct volume fraction of the negative thermal expansion material. 
     
     
         9 . The turbine bucket shroud arrangement of  claim 5 , wherein the composition is brazed to the tip shroud. 
     
     
         10 . The turbine bucket shroud arrangement of  claim 5 , wherein the composition is welded to the tip shroud. 
     
     
         11 . A method of controlling turbine bucket interaction with an adjacent turbine bucket comprising:
 reducing a gap disposed between a contact region of a tip shroud and an adjacent tip shroud by depositing a negative thermal expansion material proximate the contact region;   engaging the contact region of the tip shroud with the adjacent tip shroud during a startup operating condition and a shutdown operating condition; and   decreasing a volume of the contact region during increased temperature operating conditions upon contraction of the negative thermal expansion material, wherein decreasing the volume reduces turbine bucket tip shroud contact forces and stresses during a steady state operating condition.   
     
     
         12 . The method of  claim 11 , further comprising depositing the negative thermal expansion material proximate an adjacent contact region of the adjacent tip shroud. 
     
     
         13 . The method of  claim 11 , further comprising forming a composition proximate the contact region, wherein the composition comprises the negative thermal expansion material and a wear resistant material. 
     
     
         14 . The method of  claim 13 , further comprising forming a plurality of layers of the composition proximate the contact region. 
     
     
         15 . The method of  claim 14 , wherein each of the plurality of layers comprises a distinct volume fraction of the negative thermal expansion material. 
     
     
         16 . The method of  claim 13 , wherein the composition is brazed to the tip shroud. 
     
     
         17 . The method of  claim 13 , wherein the composition is welded to the tip shroud. 
     
     
         18 . The method of  claim 13 , wherein the composition is laser cladded to the tip shroud. 
     
     
         19 . The method of  claim 13 , wherein the composition is cold sprayed onto the tip shroud. 
     
     
         20 . The method of  claim 13 , wherein the composition is deposited during a plasma transferred arc process.