Patent Application
20130330198
The present application and the resultant patent relate generally to turbo-machinery and more particularly relate to a turbine rotor and blade assembly for use with a steam turbine having redundant locking blade retention screw holes for reduced tangential stress.
Steam turbine airfoils or buckets generally are positioned about a rotor at regular intervals in a bucket assembly. The bucket assembly may be created by inserting the buckets one at a time tangentially into an opening on the rotor and then sliding the buckets circumferentially about the rotor. The buckets may be attached to the rotor by complementary male and female dovetails and other configurations. In order to close the bucket assembly, however, the last bucket must be restrained by a feature other than a dovetail. This last bucket, generally called the locking blade or the closure bucket, may be affixed to the rotor via one or more blade retention screws and the like tapped or screwed into the rotor. Other types of connection means and other types of bucket assemblies also may be used.
Large centrifugal loads may be placed on the buckets and the rotor during operation. Such centrifugal loads and coincident thermally induced loads associated with loading transients may induce stresses in the dovetails and adjacent areas that attach the buckets to the rotor. These stresses may be of sufficient magnitude to impact adversely rotor cycle fatigue life. Of particular concern may be rotor stress concentrations associated with blade retention screws that may be tapped or otherwise inserted directly into the rotor.
There is thus a desire for an improved turbine rotor and blade assembly for a steam turbine and the like. Preferably such an improved turbine rotor and blade assembly may reduce tangential thermal stresses therein for an improved overall rotor fatigue life.
The present application and the resultant patent thus provide a turbine rotor and blade assembly for a steam turbine. The turbine rotor and blade assembly may include a rotor, a number of buckets positioned about the rotor, a locking blade positioned about the rotor, and a blind hole positioned about the rotor adjacent to the locking blade.
The present application and the resultant patent further provide a turbine rotor and blade assembly for a steam turbine. The turbine rotor and blade assembly described herein may include a rotor, a number of buckets positioned about the rotor, a locking blade positioned about the rotor, a locking blade retention screw securing the locking blade to the rotor, and a blind hole positioned about the rotor adjacent to the locking blade.
The present application and the resultant patent further provide a steam turbine. The steam turbine described herein may include a rotor, a number of buckets positioned about the rotor, a locking blade positioned about the rotor, a locking blade retention hole positioned about the locking blade, a locking blade retention screw positioned in the locking blade retention hole so as to secure the locking blade to the rotor, and one or more blind holes positioned about the rotor adjacent to the locking blade.
These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
In use, a flow of steam 70 passes through the steam inlets 60 and into the sections 15, 20 such that mechanical work may be extracted from the steam by the stages therein so as to rotate the rotor shaft 40. The flow of steam 70 then may exit the sections 15, 20 for further processing and the like. The steam turbine 10 described herein is for the purpose of example only. Steam turbines and/or other types of turbo-machinery in many other configurations and with many other or different components also may be used herein.
The turbine rotor and blade assembly 110 also may include a locking blade 170. As described above, the locking blade 170 lacks the dovetail 160. Rather, a base 180 of the locking blade 170 may be retained within the rotor 120 via a number of blade retention screws 190 and the like. The blade retention screws 190 may be grub screws or other types of set screws and the like with or without a head on one end. Each blade retention screw 190 may be positioned in a blade retention hole 200. The blade retention hole 200 may extend into the rotor 120 adjacent to the locking blade 170 as well as into the base 180 of the locking blade 170 so as to retain the locking blade 170 therein. Any number of the blade retention screws 190 may be used. The respective components described herein may have any size, shape, or configuration. Other components and other configurations also may be used herein.
As was described above, tangential thermal stresses may tend to develop about the blade retention holes 200 during operation. The turbine rotor and blade assembly 110 therefore may have a number of blind holes 210 formed therein. The blind holes 210 may be positioned in the rotor 120 on either or both sides of the blade retention hole 200. The blind holes 210 may be placed about the locking blade 170 on both axial and radial sides thereof. The blind holes 210 may have a similar size, shape, and configuration as compared to the blade retention holes 200. The blind holes 210, however, also may have any size, shape, or configuration. Blind holes 210 of differing sizes, shapes, or configurations also may be used herein together. Any number of the blind holes 210 may be used herein.
The blind holes 210 thus may improve the fatigue life of the turbine rotor and blade assembly 110 by “shielding” the blade retention holes 200 from local stress fields and the like. The blind holes 210 may straddle the blade retention holes 200 tangentially so as to protect the blade retention holes 200 from potentially damaging tangential stresses. The blind holes 200 thus may improve the fatigue life of the rotor 120 and related components for an extended component lifetime.
It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
