Gas turbine rotor with retention sleeve for a thermal medium transfer tube

Abstract: Multiple tubes (50, 52) are connected to steam supply and spent cooling steam return manifolds (42, 40) for supplying cooling steam to buckets and returning spent cooling steam from the buckets to the manifolds, respectively. The tubes are prevented from axial movement in one direction by flanges (62, 76) engaging end faces of the spacer (20) between the first and second-stage wheels (12, 14). Retention sleeves (86, 94) are disposed about cantilevered ends of the tubes. One end of the retention sleeve engages an enlarged flange on the tube, while an opposite end (90, 96) is spaced axially from an end face (89, 97) of the adjoining wheel, forming a gap ( a , b ), enabling thermal expansion of the tubes and limiting axial displacement of the tube in the opposite direction.

Description: The present invention relates to cooling medium supply and return tubes for conveying cooling medium to and from the buckets of a gas turbine and particularly relates to retention sleeves for preventing unrestrained axial movement of the thermal medium supply and return tubes, e.g., due to thermal response. In an advanced gas turbine design for industrial power generation, the rotating buckets on the turbine rotor are preferably cooled by supplying a thermal medium, for example, steam, to the buckets. The steam is supplied generally through an axial bore tube assembly and radial tubes to a plurality of circumferentially spaced supply tubes extending axially adjacent the rim of the rotor. The supply tubes extend through openings in the stacked wheel and spacer arrangement of the rotor and communicate with a supply manifold adjacent a forward portion of the rotor. The manifold, in turn, includes a plurality of cross-tubes for supplying the steam to the forwardmost wheel and buckets carried thereby. Cooling steam is also supplied from the supply manifold to the buckets of the second-stage wheel. Spent cooling steam flows from the buckets of the first-stage wheel to a return manifold. Spent cooling steam also flows from the buckets of the second-stage wheel via a plurality of cross-tubes to the return manifold. The spent cooling steam is conveyed from the return manifold to the aft end of the rotor by way of return tubes circumferentially spaced about the rotor rim. The return tubes lie in communication with radially extending tubes whereby the spent cooling medium is returned axially through the bore tube assembly to a steam source or for use in steam turbines in a combined-cycle system. In GB-A-913,167 there is disclosed a multi-stage gas turbine in which axially extending tubes are used for blowing coolant onto the rotor discs. Supply and return cross-tubes have in the past been provided with self-locking threaded inserts to retain the tube against axial movement. However, such designs are not acceptable because they require machine threads in the spacer wheel and limit access to the removed threaded insert if it is damaged. The cross-tubes must, however, be restrained from axial movement, e.g., motion caused by thermal response. During turbine startup and shutdown, the cross-tubes can thermally bind and unbind, causing the tubes to move axially, e.g., due to such thermal ratcheting. This causes the steam seals to disengage with subsequent loss of cooling to the buckets. There has thus developed a need for a removable, easily maintained device which can withstand high operating temperatures and large accelerations, have high cycle fatigue endurance, will not buckle under loads caused by thermal ratcheting and does not adversely affect the design of the spacer wheel. Therefore, according to a first embodiment of the present invention, there is provided a gas turbine rotor in accordance with claim 1. There is provided a cross-tube retention sleeve for preventing axial movement of the thermal medium cross-tubes, e.g., due to thermal ratcheting and which does not adversely affect the performance of the spacer wheel. It will be appreciated that the cross-tubes extend through openings in the spacer and are cantilevered from axial end faces of the spacer. Spoolies interconnect the ends of the cross-tubes with additional passages in the wheels mounting the buckets. Spoolies comprise sleeves having spherical end portions for engaging within cylindrical ends of adjoining but spaced tubes. To prevent axial movement of the cross-tubes which might disengage or cause leakage in the spoolies, the present invention provides an axial retention sleeve for overlying the cantilevered end of each cross-tube between the spacer mounting the cross-tube and the end face of an adjoining wheel. Particularly, each cross-tube has a radial flange against which one end of a retention sleeve bears. The opposite end of the retention sleeve is spaced axially from the end face of the adjacent wheel, forming an axial gap accommodating limited axial movement of the retention sleeve. This limited axial movement accommodates movement, for example, resulting from thermal expansion of the cross-tubes but limits the movement to preclude binding of the tubes and disruption of the seals. In a preferred embodiment according to the present invention, there is provided in a gas turbine rotor having stacked wheels and spacers and tubes for conveying a thermal medium between buckets of one of the wheels and a manifold, the tubes extending generally in an axial direction in openings through a spacer adjacent a rim of the rotor and having radially outwardly directed flanges, retention sleeves for limiting axial movement of the tubes in a first axial direction, each retention sleeve having a first end in opposition to an end face of a rotor wheel forming an axial gap therebetween and a second end butting the flange, whereby axial movement of the tubes closes the gaps to prevent further axial movement of the tubes in the first axial direction. In a further preferred embodiment according to the present invention, there is provided in a gas turbine rotor having stacked wheels and spacers and first tubes for supplying cooling steam to buckets of a first rotor wheel and second tubes for returning spent cooling steam from the buckets of a second rotor wheel, the tubes extending in a generally axial direction in openings through a spacer between the first and second rotor wheels and adjacent a rim of the rotor, each of the tubes having radially outwardly directed flanges, first and second retention sleeves for preventing axial movement of the first and second tubes in respective first and second axial directions, the first retention sleeves having first ends in opposition to an end face of the first rotor wheel and forming axial gaps therewith, the second retention sleeves having first ends in opposition to an end face of the second rotor wheel and forming axial gaps therewith, each of the first and second sleeves having second ends butting respective flanges of the first and second tubes, whereby axial movement of the tubes responsive to thermal expansion thereof closes the gaps to prevent further axial movement of the first and second tubes in the first and second axial directions, respectively. An embodiment of the invention will now be described, by way of example; with reference to the accompanying drawings, in which: FIGURE 1 is a perspective view of a portion of a gas turbine rotor with parts broken out and in cross-section illustrating cooling medium supply and return tubes and cross-tubes; FIGURE 2 is an enlarged fragmentary cross-sectional view of portions of the first and second-stage wheels and 1-2 spacer illustrating the cross-tubes and retention sleeve constructed in accordance with the present invention; FIGURE 3 is a longitudinal cross-sectional view of a supply cross-tube illustrating a retention sleeve on an end thereof; and FIGURE 4 is a view similar to Figure 3 illustrating a return cross-tube with the retention sleeve on an end thereof. Referring to Figure 1, there is illustrated a portion of a rotor, generally designated 10, for a gas turbine. The illustrated rotor comprises a plurality of wheels 12, 14, 16 and 18, with spacers 20, 22 and 24 alternately between the wheels. The wheels 12, 14, 16 and 18 mount buckets, not shown, while nozzles, also not shown, are disposed between the arrays of buckets in the hot gas path of the gas turbine. The stacked wheels and spacers are held together by a plurality of axially extending, elongated bolts, not shown. Additionally, the rotor includes an aft bore tube assembly, generally designated 26, which extends through an aft bearing, not shown, and includes inner and outer sleeves 30 and 32 defining an annulus 34 therebetween. The annulus 34 communicates with a plenum for supplying a cooling medium, e.g., steam, for flow axially through the annulus 34, through a plurality of circumferentially spaced, radially extending tubes 36 in communication with respective supply tubes 38. Supply tubes 38 comprise an array of tubes spaced circumferentially one from the other and extending axially through aligned openings in the wheels and spacers of the rotor and adjacent the rotor rim. The supply tubes 38 supply the cooling medium to a first manifold 40 for distributing the cooling medium to the turbine buckets, preferably the buckets secured to the first and second-stage wheels 12 and 14, respectively. A return manifold 42 communicates with the first and second-stage buckets for receiving spent cooling medium and returning the spent cooling medium through a plurality of circumferentially spaced return tubes 44 extending axially through aligned openings in the stacked wheels and spacers likewise adjacent the rotor rim. The tubes 44 communicate with radially extending tubes 46 for returning the steam axially along the bore tube assembly 26 within inner sleeve 30 for return to a steam supply or for use in steam turbines forming part of a combined-cycle system. More particularly, and referring to Figure 2, there is illustrated supply and return cross-tubes 50 and 52, respectively, disposed in bores 54 and 56 in the spacer 20 between wheels 12 and 14. The cross tubes 50 and 52 lie in communication with the supply and return manifolds 40 and 42, respectively. Cross tubes 50 supply cooling steam from supply manifold 40 to buckets of the first-stage wheel and cross tube 52 returns spent cooling steam from the second-stage buckets to the return manifold 42. Cross-tube 50 comprises a cylindrical tube having a diametrically enlarged portion 58 adjacent an aft end thereof and a diametrically enlarged portion 60 intermediate its opposite ends. Additionally, cross tube 50 includes a radially enlarged flange 62 at the forward end of enlarged portion 60 and which flange 62 is chamfered and seats against a corresponding chamfer 64 at the forward end of the opening 54 through spacer 20. The cross tube 50 extends forwardly in a direction toward the first-stage wheel 12 and mounts a pair of axially spaced flanges 63 and 65 forming retention sleeve stand-offs on a cantilevered forward end portion of tube 50. As illustrated by the dashed lines in Figure 2, the forward end of cross tube 50 communicates with a spoolie 66, in turn, in communication with a shortened tube 68. Short tube 68 lies in communication with passages, not shown, opening into a certain bucket of the first-stage wheel 12. It will, be appreciated from a review of Figure 2 that the cross tube 50 is fixed against axial movement in the aft direction, i.e., from left to right in Figure 2, by the engagement of the flange 62 against the chamfered face 64 of the spacer 20. However, the tube 50 is otherwise free for axial movement in the opposite direction but for the retention sleeve described hereinafter. The cross tube 52 similarly includes a diametrically enlarged portion 70 adjacent one end, intermediate portion 72 and portion 74 adjacent the aft end of tube 52. The portions 70, 72 and 74 seat the tube 52 in the opening 56 of spacer 20. An enlarged diameter flange 76 carried by tube 52 adjacent its aft end engages a chamfered surface 78 about the opening 56 at the aft face of spacer 20. The tube 52 extends aft short of the forward face of the second-stage wheel 14 and lies in communication with a short tube 80 by way of a spoolie 82. Consequently, like the supply tube 50, return tube 52 is fixed against axial movement in one direction, in this case in a forward axial direction, by the engagement of flange 76 against the chamfer 78. Cross tube 52 is, however, free for axial movement in an opposite direction but for a retention sleeve, which will now be described. Referring to Figure 3, the cantilevered forward end of each cross tube 50 is provided with a cylindrical retention sleeve 86. Sleeve 86 is open at its opposite ends and has an inside diameter for telescopic engagement about the flanges 63 and 65 of cross tube 50. The aft end of retention sleeve 86 butts against the enlarged flange 62. The opposite end of the retention sleeve 86 is flared outwardly at 90 and is spaced axially from the aft end face 89 of the stage 1 wheel 12, defining an axial gap a therebetween. It will be appreciated from a review of Figures 2 and 3 that the cross-tube 50 is prevented from axial movement in an aft direction by engagement of flange 62 against the chamfered face 64 of spacer 20. Cross tube 50 is limited in its axial forward movement by the engagement between flange 62 and the aft end of retention sleeve 86 and engagement of the forward flared end 90 of retention sleeve 86 against the aft end face 89 of wheel 12. The axial gap a between the flared end 90 and end face 89 of wheel 12 accommodates axial thermal expansion of the tube 50. This axial gap a enables a very limited extent of axial movement which prevents unacceptably high thermal buckling stresses from developing and facilitates installation of the cross tube 50 and sleeve 86. The flared end 90 precludes wear on the wheel face 89 or binding of the retention sleeve 86 during start-up which would otherwise cause high bending stresses in the cross-tube. Also, the inside diameter of sleeve 86 is larger than the seal diameter of the spoolies with the sleeve 86 and tube 50 thereby preventing contact therewith which would otherwise damage the seal. As illustrated, the retention sleeve is cantilevered for support on the projecting and similarly cantilevered forward end of the cross tube 50. In similar fashion, the return tube 52 has an enlarged diameter cantilevered portion 88 at its aft end for receiving the forward end of a retention sleeve 94. As illustrated in Figures 2 and 4, the forward end of retention sleeve 94 butts the aft end of flange 76, while the aft end of sleeve 94 is flared at 96 and is spaced axially from the forward face 97 of second-stage wheel 14 to define an axial gap b therebetween. Consequently, the tube 52 is fixed against axial movement in a forward direction by engagement of its flange 76 against the aft face of spacer 20. Cross tube 52 is limited in its axial rearward movement by the engagement between the flared end 96 and the forward end face 97 of wheel 14, e.g., upon axial thermal expansion of the tube. The retention sleeve 94 thus serves similar purposes as the retention sleeve 86 but in an opposite orientation vis-a-vis the rotor. As can be best exemplified by reference to Figure 2, the cooling steam supplied through the supply tubes 38 enters the manifold 40 for distribution to the cross-tubes 50, there being preferably six cross-tubes supplied with thermal medium from each supply tube 38. Steam flows from the supply manifold 40 through the cross-tubes 50 and into the tubes 68 for distribution into the associated buckets of the first-stage wheel. The supply steam is also provided the buckets of the second-stage via spoolies 100 and sleeves 102 in communication with the supply manifold 40. Spent cooling steam is returned from the second-stage buckets via sleeve 80 and spoolie 82 into the cross-tube 52 for flow into the return manifold 42. Spent cooling steam from the first-stage buckets is provided manifold 42 by way of tubes 104 and spoolies 106, coupled to the first-stage wheel 12. Spent cooling steam is returned from manifold 42 via return tube 44, radial tubes 46, and along the axis of inner sleeve 30 to a steam supply or to steam turbines of a combined-cycle system.

Claims: A gas turbine rotor (10) having stacked wheels (12,14,16,18), spacers (20, 22, 24), tubes (50) for conveying a thermal medium between buckets (12) of one of said wheels and a manifold (42, 40), said tubes extending generally in an axial direction in openings (54) through a spacer (20) adjacent a rim of the rotor and each having a radially outwardly directed flange (62), and a retention sleeve (86) for limiting axial movement of a said tube (50) in the gas turbine rotor, the retention sleeve (86) having a first end (90) in opposition to an end face (89) of a rotor wheel (12) forming an axial gap (a) therebetween and a second end butting said flange (62), whereby axial movement of said tubes closes said gaps to prevent further axial movement of said tubes in a first axial direction. A gas turbine rotor according to Claim 1 wherein said first end (90) of said retention sleeve (86) is flared in a radially outward direction. A gas turbine rotor according to Claim 1 or claim 2 wherein said flange (62) bears against said spacer (20) to prevent axial movement of said tubes (50) in a second axial direction opposite said first axial direction. A gas turbine rotor according to any one of Claims 1 to 3 wherein each said tube (50) includes a plurality of flanges (63,65) spaced axially from one another forming stand-offs for said retention sleeve (86). A gas turbine rotor according to any one of Claims 1 to 4 wherein an end portion of each tube (50) is cantilevered from said spacer (20), said retention sleeve (86) lying concentrically about said cantilevered portion of said tube and being wholly supported by said cantilevered portion of the tube. A gas turbine rotor (10) according to any one of claims 1 to 5 further comprising second tubes (52) for returning spent thermal medium from the buckets of a second rotor wheel (14), said tubes extending in a generally axial direction in openings through a spacer (20) between said first (12) and second (14) rotor wheels and adjacent a rim of the rotor, each of said tubes (52) having radially outwardly directed flanges (76), and second retention sleeves (94) for preventing axial movement of said second tubes in respective first and second axial directions, said second retention sleeves (94) having first ends (96) in opposition to an end face (97) of said second rotor wheel (14) and forming axial gaps (b) therewith said second sleeves having second ends butting respective flanges (76) of said second tubes, whereby axial movement of said tubes responsive to thermal expansion thereof closes said gaps to prevent further axial movement of said second tubes (52) in said first and second axial directions, respectively.

Inventors: CZACHOR ROBERT PAUL, LATHROP NORMAN DOUGLAS, CZACHOR, ROBERT PAUL, LATHROP, NORMAN DOUGLAS
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 2000
Main classification: F01D5
IPC codes: F01D5, F02C7