Internal reaction steam turbine cooling arrangement

Abstract

A rotor of a turbomachine includes a rotor drum located at a central axis and a plurality of buckets secured to the rotor drum. A first reaction stage includes axial entry dovetailed buckets. An axial passage for cooling flow is provided along a mating surface between the bucket dovetail and the dovetail slot in the rotor drum. Cool steam at taken between a first stage bucket and a second stage nozzle and passed through the axial passage to a low pressure sink at an upstream end of the rotor.

1 . A rotor of a turbomachine comprising:
 a rotor drum disposed at a central axis;   a plurality of dovetailed buckets for a stage of the turbomachine, wherein the plurality of dovetailed buckets are secured to the rotor drum at mating surfaces within a corresponding plurality of dovetailed slots cut in the rotor drum;   at least one cooling passage formed within the rotor drum for the stage of the turbomachine; and   a low pressure sink disposed at an upstream end of the rotor drum receptive of a coolant flow through the cooling passage.   
     
     
         2 . The rotor of  claim 1 , wherein the stage if a first stage, reaction stage for a rotor of a steam turbine. 
     
     
         3 . The rotor of  claim 2 , wherein the coolant flow comprises steam routed into the cooling passage from a downstream portion of the steam turbine including a space immediately downstream from each of the plurality of dovetailed bucket in the stage. 
     
     
         4 . The rotor of  claim 3 , wherein the plurality of dovetailed slots are cut in the rotor drum for axial entry of the plurality of dovetailed buckets. 
     
     
         5 . The rotor of  claim 4 , wherein the at least one cooling passage formed within the rotor drum for the stage of the turbomachine comprises at least one space formed between a male dovetail of the dovetailed bucket and a complimentary male projection of the rotor drum. 
     
     
         6 . The rotor of  claim 3 , wherein the plurality of dovetailed slots are cut in the rotor drum for tangential entry of the plurality of dovetailed buckets and the at least one cooling passage formed within the rotor drum for the stage of the turbomachine comprises a hole bored axially through a root of the bucket above the dovetail. 
     
     
         7 . The rotor of  claim 1 , further comprising:
 an axial through-hole of the rotor drum at a base of each dovetail slot of the plurality of dovetail slots; and   a twist-lock device installed in the axial through-hole of the rotor drum and adapted for the axially retaining the dovetailed bucket, the twist lock device including a center pin, a retaining head at each end of the center pin wherein a forward head includes a rotatable half-head, being rotatable to an inward radial position allowing entry of the dovetailed bucket into the dovetailed slot and being rotatable to an outward radial position retaining the dovetailed bucket in the dovetailed slot.   
     
     
         8 . The rotor of  claim 7 , further comprising:
 an annular spacer adapted to mount around the rotor drum between a first stage and a second stage for temporary use during insertion of dovetailed buckets into axial dovetail slots of the rotor drum, wherein an axial length of the annular spacer is sized for axial positioning of the plurality of dovetailed buckets.   
     
     
         9 . The rotor of  claim 1 , comprising:
 at least one rotor drum through hole extending from the cooling passage to the low pressure sink, wherein the low pressure sink comprises at least a root spill of the a first stage.   
     
     
         10 . The rotor of  claim 9 , further comprising:
 sealing means between an upstream root of the plurality of buckets and the root spill of the first stage, wherein the sealing means include J-seals.   
     
     
         11 . A multi-stage steam turbine comprising:
 a stator disposed at a central axis; and   a rotor disposed radially inboard of the stator including:   a rotor drum;   a plurality of dovetailed buckets for a stage of the steam turbine, wherein the plurality of dovetailed buckets are secured to the rotor drum at mating surfaces within a corresponding plurality of dovetailed slots cut in the rotor;   at least one cooling passage formed within the rotor drum for the stage of the turbomachine; and   a low pressure sink disposed at an upstream end of the rotor receptive of a coolant flow through the cooling passage.   
     
     
         12 . The rotor of  claim 11  wherein the stage of the steam turbine is a first stage reaction stage. 
     
     
         13 . The steam turbine of  claim 12  wherein the coolant flow comprises steam routed into the cooling passage from a downstream portion of the steam turbine including a space immediately downstream from each of the plurality of dovetailed bucket in the stage. 
     
     
         14 . The rotor of  claim 13  wherein the plurality of dovetailed slots are cut in the rotor drum for axial entry of the plurality of dovetailed buckets. 
     
     
         15 . The rotor of  claim 14  wherein the at least one cooling passage formed within the rotor drum for the stage of the turbomachine comprises at least one space formed between a dovetail of the dovetailed bucket and a complimentary male projection of the rotor drum. 
     
     
         16 . The rotor of  claim 12  wherein the plurality of dovetailed slots are cut in the rotor drum for tangential entry of the plurality of dovetailed buckets. 
     
     
         17 . The rotor of  claim 16  wherein the at least one cooling passage formed within the rotor drum for the stage of the turbomachine comprises a hole bored axially through a root of the bucket above the dovetail. 
     
     
         18 . The rotor of  claim 1  comprising at least one rotor drum through hole extending from the cooling passage to the low pressure sink. 
     
     
         19 . The rotor of  claim 1 , further comprising:
 an axial through-hole of the rotor drum at a base of each dovetail slot of the plurality of dovetail slots; and   a twist-lock device installed in the axial through-hole of the rotor drum and adapted for the axially retaining the dovetailed bucket, the twist lock device including a center pin, a retaining head at each end of the center pin wherein a forward head includes a rotatable half-head, being rotatable to an inward radial position allowing entry of the dovetailed bucket into the dovetailed slot and being rotatable to an outward radial position retaining the dovetailed bucket in the dovetailed slot.   
     
     
         20 . A method for installing axial entry dovetailed buckets into dovetail slots of a stage of a drum rotor, the method comprising:
 inserting a twist lock device into an axial through-hole in a base of a dovetail slot of a stage of a drum rotor for each of a plurality of dovetailed buckets;   orienting a half-head of a front head of the twist lock device in an inward radial direction;   inserting a spacer in a space in the drum rotor between a stage and a succeeding stage;   fully inserting the dovetailed bucket into the dovetail slot of the stage of the rotor drum;   orienting the half-head of the front head of the twist-lock device in an outward radial direction; and   removing the spacer.