Sleeve for turbine bearing stack

Abstract

A support bearing arrangement comprises a gas turbine rotor shaft, a bearing stack, a bearing sleeve, and a support bearing. The bearing stack comprises a fore seal plate, and aft seal plate, and a bearing mount situated axially between the fore and aft seal plates. The bearing sleeve surrounds at least a portion of the rotor shaft, and is configured to form an insulating air gap between the rotor shaft and the bearing stack. The support bearing is mounted on the bearing mount to couple the gas turbine rotor shaft to a stationary structure, thereby centering and retaining the gas turbine rotor shaft.

1 . A support bearing arrangement comprising:
 a gas turbine rotor shaft;   a bearing stack comprised of a fore seal plate, an aft seal plate, and a bearing mount situated axially between the fore and aft seal plates;   a bearing sleeve surrounding at least a portion of the rotor shaft, and configured to form an insulating air gap between the rotor shaft and the bearing stack; and   a support bearing mounted on the bearing mount to couple the gas turbine rotor shaft to a stationary structure, thereby centering and retaining the gas turbine rotor shaft.   
     
     
         2 . The support bearing arrangement of  claim 1 , further comprising a rotor disk affixed to the rotor shaft, wherein the bearing sleeve and an axially-extending cylindrical portion of the rotor disk surrounding the rotor shaft define the insulating air gap. 
     
     
         3 . The support bearing arrangement of  claim 2 , further comprising a blade retention minidisk disposed axially between the rotor disk and the bearing sleeve, and an axial load nut configured to attach to the gas turbine rotor shaft and bear axial load from the minidisk through the bearing sleeve. 
     
     
         4 . The support bearing arrangement of  claim 1 , wherein the fore seal plate and the aft seal plate mate with adjacent fore and aft seals, respectively, to form oil seals. 
     
     
         5 . The support bearing arrangement of  claim 4 , wherein the bearing mount is lubricated with oil collected by an oil scoop situated axially between the fore and aft seal plates. 
     
     
         6 . The support bearing arrangement of  claim 1 , wherein the bearing sleeve is formed of a material selected to closely match the thermal expansion coefficients of surrounding components. 
     
     
         7 . The support bearing arrangement of  claim 6 , wherein the bearing sleeve is formed of Waspalloy. 
     
     
         8 . The support bearing arrangement of  claim 1 , wherein the stationary structure is a mid-turbine frame situated between a high pressure turbine and a low pressure turbine of a two-stage gas turbine engine. 
     
     
         9 . A gas turbine shaft assembly comprising:
 a gas turbine rotor disk mounted on a rotatable shaft, the gas turbine rotor disk having an axially aft-extending cylindrical portion;   a bearing sleeve sheathing the aft-extending cylindrical portion of the rotor disk so as to define an insulating radial air gap between the bearing sleeve and the aft-extending cylindrical portion of the rotor disk; and   a bearing stack comprising a bearing mount axially between fore and aft face seals situated radially atop the bearing sleeve, and thermally shielded from the gas turbine rotor disk and the rotatable shaft by the insulating radial air gap.   
     
     
         10 . The gas turbine shaft assembly of  claim 9 , further comprising a minidisk mounted on the aft-extending cylindrical portion of the rotor disk to retain blades of the gas turbine rotor disk. 
     
     
         11 . The gas turbine shaft assembly of  claim 10 , further comprising a first nut configured to axially retain the gas turbine rotor disk on the rotatable shaft, and a second nut configured to axially retain the minidisk against the gas turbine rotor disk by means of axial load transferred through the bearing stack and the bearing sleeve. 
     
     
         12 . The gas turbine shaft assembly of  claim 9 , wherein the gas turbine rotor shaft is a high pressure shaft of a two-stage gas turbine engine. 
     
     
         13 . The gas turbine shaft assembly of  claim 9 , wherein the bearing mount accepts a support bearing configured to transfer radial load from the gas turbine rotor shaft to a stationary structure, thereby retaining and centering the gas turbine rotor shaft. 
     
     
         14 . The gas turbine shaft assembly of  claim 15 , wherein the support bearing is a roller bearing. 
     
     
         15 . The gas turbine shaft assembly of  claim 15 , wherein the stationary structure is a mid-turbine frame comprising a plurality of stationary vanes disposed between a high pressure turbine and a low pressure turbine of a two-stage gas turbine engine. 
     
     
         16 . The gas turbine shaft assembly of  claim 9 , wherein the bearing mount is lubricated with oil collected by an oil scoop also mounted axially between the fore and aft seal plates.