Low pressure turbine exhaust diffuser with turbulators

Abstract

A turbine exhaust diffuser for use adjacent a last stage row of buckets fixed to a turbine rotor includes an annular inner diffuser ring and an annular outer diffuser ring defining a flow path for steam exiting a last stage row of buckets in a first substantially axial direction at a diffuser inlet, and turning substantially ninety degrees to a diffuser outlet. The outer diffuser ring has a curved steam guide surface extending between the diffuser inlet and the diffuser outlet including a first portion extending away from the diffuser inlet and a second portion extending to said diffuser outlet, the second portion shaped to extend beyond vertical and back toward the diffuser inlet so as to establish a flow component in a second opposite axial direction. The second portion is also provided with a plurality of turbulators to minimize flow separation along the steam guide surface.

1 . A turbine exhaust diffuser for use adjacent a last stage row of buckets fixed to a turbine rotor, the diffuser comprising:
 an annular inner diffuser ring and an annular outer diffuser ring defining a flow path for steam exiting a last stage row of buckets in a first substantially axial direction at a diffuser inlet, and turning substantially ninety degrees to a diffuser outlet; the outer diffuser ring having a curved steam guide surface extending between the diffuser inlet and the diffuser outlet and having a first portion extending away from the diffuser inlet and a second portion, extending to said diffuser outlet, said second portion shaped to extend beyond vertical and back toward said diffuser inlet so as to establish a flow component in a second opposite axial direction; wherein said second portion is provided with a plurality of turbulators.   
     
     
         2 . The low pressure turbine diffuser of  claim 1  wherein said turbulators are arranged in radially-spaced, circumferential rows. 
     
     
         3 . The turbine exhaust diffuser of  claim 2  wherein turbulators in adjacent radially-spaced, circumferential rows are circumferentially aligned. 
     
     
         4 . The turbine exhaust diffuser of  claim 2  wherein turbulators in adjacent radially-spaced circumferential rows are circumferentially staggered. 
     
     
         5 . The turbine exhaust diffuser of  claim 2  wherein said radially-spaced circumferential rows comprise at least two rows. 
     
     
         6 . The turbine exhaust diffuser of  claim 1  wherein said turbulators comprise hemispherical protrusions. 
     
     
         7 . The turbine exhaust diffuser of  claim 1  wherein said turbulators comprise hemispherical depressions. 
     
     
         8 . The turbine exhaust diffuser of  claim 1  wherein said turbulators have non-round shapes. 
     
     
         9 . The turbine exhaust diffuser of  claim 8  wherein said turbulators are arranged in radially-spaced, circumferential rows. 
     
     
         10 . A turbine exhaust diffuser adjacent a last stage row of buckets fixed to a turbine rotor comprising:
 an annular inner diffuser ring and an annular diffuser outer ring defining a flow path for steam exiting a last stage row of buckets in a first substantially axial direction at a diffuser inlet, and turning substantially ninety degrees to a diffuser outlet;   the outer diffuser ring having a curved steam guide surface extending between the diffuser inlet and the diffuser outlet and having a first portion extending away from the diffuser inlet and a second portion extending to said diffuser outlet, said second portion shaped to extend beyond vertical and back toward said diffuser inlet so as to establish a flow component in a second opposite axial direction; wherein said second portion is provided with a plurality of turbulators arranged in at least two radially-spaced, circumferential rows.   
     
     
         11 . The turbine exhaust diffuser of  claim 10  the turbine exhaust diffuser of  claim 2  wherein turbulators in adjacent radially-spaced, circumferential rows are circumferentially staggered. 
     
     
         12 . The turbine exhaust diffuser of  claim 10  wherein said turbulators comprise hemispherical dimples. 
     
     
         13 . The turbine exhaust diffuser of  claim 11  wherein said turbulators comprise hemispherical protrusions. 
     
     
         14 . The turbine exhaust diffuser of  claim 10  said turbulators have non-round shapes. 
     
     
         15 . A method of increasing an outlet area of a turbine exhaust diffuser and minimizing flow separation along an outer wall portion of said turbine exhaust diffuser comprising:
 (a) shaping the outer wall portion extending between an axially-oriented diffuser inlet to a substantially radially oriented diffuser outlet to extend beyond vertical and back toward the diffuser inlet so as to establish a flow component in an upstream axial direction; and   (b) providing plural turbulators on said outer wall portion to generate localized vortices to minimize flow separation along said outer wall portion.   
     
     
         16 . The turbine exhaust diffuser of  claim 15  wherein wherein said plural turbulators are arranged in radially-spaced, circumferential rows. 
     
     
         17 . The turbine exhaust diffuser of  claim 15  wherein said plural turbulators have round shapes. 
     
     
         18 . The turbine exhaust diffuser of  claim 15  wherein said plural turbulators have non-round shapes. 
     
     
         19 . The turbine exhaust diffuser of  claim 15  wherein said turbulators comprise projections or dimples. 
     
     
         20 . The method of  claim 16  wherein said plural turbulators in adjacent radially-spaced, circumferential rows are circumferentially aligned or staggered.