System and method for adjusting clearance in a gas turbine

Abstract

A system for adjusting a clearance in a gas turbine including a turbine rotor and a plurality of buckets is disclosed. The system includes: a shroud assembly including at least one shroud segment, the at least one shroud segment being disposed in an interior of a turbine shell; and an elongated member extending from the turbine shell. The at least one shroud segment is attached to an end of the elongated member, the elongated member configured to move in response to a temperature change to move the shroud segment and change a clearance between the shroud segment and at least one of the plurality of buckets.

1 . A system for adjusting a clearance in a gas turbine including a turbine rotor and a plurality of buckets, the system comprising:
 a shroud assembly including at least one shroud segment, the at least one shroud segment being disposed in an interior of a turbine shell; and   an elongated member extending from the turbine shell;   wherein the at least one shroud segment is attached to an end of the elongated member, the elongated member configured to move in response to a temperature change to move the shroud segment and change a clearance between the shroud segment and at least one of the plurality of buckets.   
   
   
       2 . The system of  claim 1 , wherein a coefficient of thermal expansion (CTE) of the elongated member is different than the CTE of the turbine shell. 
   
   
       3 . The system of  claim 1 , wherein the elongated member extends through the turbine shell in a radial direction, the radial direction being normal to a major axis of the turbine rotor. 
   
   
       4 . The system of  claim 1 , further comprising a tube extending through at least a portion of the turbine shell, the elongated member extending through the tube. 
   
   
       5 . The system of  claim 4 , wherein a coefficient of thermal expansion (CTE) of the elongated member is different than the CTE of the tube. 
   
   
       6 . The system of  claim 1 , wherein the elongated member is selected from a hollow rod and a solid rod. 
   
   
       7 . The system of  claim 1 , further comprising a protrusion attached to an exterior of the turbine shell and attached to the elongated member, and an electric heat source in thermal communication with the protrusion for changing the temperature of at least one of the protrusion and the elongated member. 
   
   
       8 . The system of  claim 1 , wherein the at least one segment includes an outer shroud attached to the turbine shell, an intermediate shroud attached to the elongated member, and an inner shroud attached to the intermediate shroud. 
   
   
       9 . The system of  claim 1 , further comprising an inlet through at least one of the elongated member and the turbine shell for introducing a thermal source to the elongated member. 
   
   
       10 . The system of  claim 9 , wherein the thermal source is selected from at least one of steam, air and gas. 
   
   
       11 . The system of  claim 1 , wherein the shroud assembly includes a plurality of shroud segments configured to form a ring. 
   
   
       12 . The system of  claim 1 , further comprising an adjustment device at a connection point between the elongated member and the turbine shell, the adjustment device configured to be engaged to move the elongated member relative to the turbine shell. 
   
   
       13 . The system of  claim 1 , further comprising at least one additional elongated member extending from the turbine shell and attached to the at least one shroud segment, wherein both the elongated member and the at least one additional elongated member extend in an average direction parallel to a radial direction extending from a rotational axis of the gas turbine. 
   
   
       14 . A method of adjusting a clearance in a gas turbine including a turbine rotor and a plurality of buckets, the method comprising:
 disposing a shroud assembly on a turbine shell, the shroud assembly including a shroud segment attached to one end of an elongated member;   extending the elongated member from the turbine shell and disposing the shroud segment in an interior of a turbine shell; and   applying a thermal source to the shroud assembly to move the shroud segment and change a clearance between the shroud segment and at least one of the plurality of buckets.   
   
   
       15 . The method of  claim 14 , wherein applying the thermal source includes applying the thermal source to the elongated member to elevate a temperature of the elongated member to cause the shroud segment to move radially toward an interior of the turbine shell. 
   
   
       16 . The method of  claim 14 , wherein applying the thermal source includes applying the thermal source to the elongated member to reduce a temperature of the elongated member to cause the shroud segment to move radially away from an interior of the turbine shell. 
   
   
       17 . The method of  claim 14 , wherein the shroud assembly includes a protrusion attached to an exterior of the turbine shell and attached to the elongated member. 
   
   
       18 . The method of  claim 17 , wherein applying the thermal source includes applying the thermal source to the protrusion to cause the protrusion to thermally expand and move the elongated member radially away from the interior of the turbine shell. 
   
   
       19 . The method of  claim 14 , wherein disposing the shroud segment includes determining a maximum pinch between the bucket tip and the shroud segment, and disposing the shroud segment at an initial radial location based on the maximum pinch. 
   
   
       20 . The method of  claim 19 , further comprising retracting the shroud segment to the initial position upon a malfunction of the shroud assembly.