Note: Within nine months of the publication of the mention of the grant of the European patent in the European PatentBulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with theImplementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has beenpaid. (Art. 99(1) European Patent Convention).

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TEPZZ_4885B_T(11) EP 2 143 885 B1

(12) EUROPEAN PATENT SPECIFICATION

(45) Date of publication and mention of the grant of the patent: 19.06.2013 Bulletin 2013/25

(21) Application number: 09164233.0

(22) Date of filing: 30.06.2009

(51) Int Cl.:F01D 5/30 (2006.01) F01D 11/00 (2006.01)

F01D 5/08 (2006.01) F16J 15/46 (2006.01)

(54) Gas assisted turbine seal

Gasuntersttzte Turbinendichtung

Joint de turbine assist par gaz

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK TR

(30) Priority: 08.07.2008 US 168927

(43) Date of publication of application: 13.01.2010 Bulletin 2010/02

(73) Proprietor: General Electric CompanySchenectady, NY 12345 (US)

(72) Inventors: Arness, Brian P.

Simpsonville, SC 29681 (US)

Ward, John D.Woodruff, SC 29388 (US)

(74) Representative: Cleary, Fidelma et alGE International Inc. Global Patent Operation-Europe 15 John Adam StreetLondon WC2N 6LU (GB)

(56) References cited: EP-A- 0 799 974 EP-A- 1 731 714WO-A-00/75491 GB-A- 2 224 082US-B1- 6 375 429

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Description

TECHNICAL FIELD

[0001] The present application relates generally to anytype of turbine and more particularly relates to systemsand methods for sealing a gap formed between a turbinebucket dovetail and a turbine rotor via gas pressure anda deformable seal material.

BACKGROUND OF THE INVENTION

[0002] Gas turbines generally include a turbine rotor(wheel) with a number of circumferentially spaced buck-ets (blades). The buckets generally may include an airfoil,a platform, a shank, a dovetail, and other elements. Thedovetail of each bucket is positioned within the turbinerotor and secured therein. The airfoils project into the hotgas path so as to convert the kinetic energy of the gasinto rotational mechanical energy. A number of coolingmedium passages may extend radially through the buck-et to direct an inward and/or an outward flow of the coolingmedium therethrough.[0003] Leaks may develop in the coolant supply circuitbased upon a gap between the tabs of the dovetails andthe surface of the rotor due to increases in thermal and/orcentrifugal loads. Air losses from the bucket supply circuitinto the wheel space may be significant with respect toblade cooling medium flow requirements. Moreover, theair may be extracted from later compressor stages suchthat the penalty on energy output and overall efficiencymay be significant during engine operation.[0004] Efforts have been made to limit this leak. Forexample, one method involves depositing aluminum ona dovetail tab so as to fill the gap at least partially. Spe-cifically, a circular ring may be pressed against the for-ward side of the dovetail face. Although this design sealswell and is durable, the design cannot be easily disas-sembled and replaced in the field. Rather, these ringsmay only be disassembled when the entire rotor is dis-assembled.[0005] United States Patent No.6375429 describes aturbomachine rotor blade having a dovetail-type basemember, a platform carried by the base member, and anairfoil extending longitudinally from the platform in a di-rection opposite to that of the base member. The platformincludes a forward seal wire groove and an aft seal wiregroove, each of which is on opposite sides of the bladelongitudinal axis and on the side of the platform facingthe base member. The blade platform has a pair of re-cesses that each include a concave portion and an ad-jacent inclined ramp portion for urging a seal wire intosurface-to-surface contact with the concave portions ofthe respective recesses. Wear of the blade platformcaused by seal wire movement relative to the blade plat-form is significantly reduced.[0006] United Kingdom Patent Application No.2224082 describes a blade and disc assembly wherein

blades are retained in grooves through the disc rim anda space exists between the radially inner end portions ofthe blades and the bottom portion of their respectivegrooves, and wherein a cooling air passage exit is in thebottom of each said groove and cooling air passagemeans in each blade has an inlet opposing a respectivesaid exit. The assembly includes rigid sealing meansstraddling opposing inlet and exit, in interfering engage-ment with the periphery of the said bottom portion of eachrespective groove, the material of the sealing means be-ing softer than the material from which the disc is made.[0007] European Patent Application No. 1731714 de-scribes a gas turbine with a channel wall that limits a flow,said channel wall comprising first and second wall sec-tions, one of the wall sections being part of a combustionchamber of the gas turbine and the other wall sectionbeing part of an annular hot gas channel of a turbine unit,and the two adjacent wall sections facing each other witha gap there between. In order to reduce the leakagequantities of blocking gas that protect the gap from theentry of hot gas, it is proposed that blocking elementprojects from the side of the first wall section into the gapand can be displaced transversely thereto, said blockingelement comprising a piston face disposed in the firstwall section and a sealing structure lying opposite thepiston face, it being possible to press said sealing meansagainst an end sealing section of the second wall sectionby means of a pressure medium that acts on the pistonface.[0008] There is thus a desire for improved dovetail tabsealing systems and methods. Such systems and meth-ods should adequately prevent leakage therethrough soas to increase overall system efficiency while being in-stallable and/or repairable in the field.

SUMMARY OF THE INVENTION

[0009] The present application thus provides a dovetailseal assembly for sealing a gap between a bucket dove-tail and a rotor, and a method of sealing a gap betweena bucket dovetail and a rotor as recited in the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] There follows a detailed description of embod-iments of the invention by way of example only with ref-erence to the accompanying drawings, in which:

Fig. 1A is a perspective view of a bucket with a shroudthat may be used with the sealing systems as aredescribed herein;Fig. 1B is a perspective view of a bucket without ashroud that may be used with the sealing systemsas are described herein;Fig. 2 is a perspective view of a rotor;Fig. 3 is a side plan view of a sealing slot of a sealingsystem as is described herein;

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Fig. 4 is a side cross-sectional view of the sealingslot and a high-pressure supply hole of the sealingsystem as is described herein; andFig. 5 is a side cross-sectional view of the sealingsystem as is described herein.

DETAILED DESCRIPTION

[0011] Referring now to the drawings, in which like nu-merals refer to like elements throughout the severalviews, Fig. 1A shows a bucket 10 as may be used herein.The bucket 10 may be a first or a second stage bucketas used in a 7FA+e gas turbine sold by General ElectricCompany of Schenectady, New York. Any other type ofbucket or stage also may be used herein. The bucket 10may be used with a rotor 20 as is shown in Fig. 2.[0012] As is known, the bucket 10 may include an airfoil30, a platform 40, a shank 50, a dovetail 60, and otherelements. It will be appreciated that the bucket 10 is oneof a number of circumferentially spaced buckets 10 se-cured to and about the rotor 20 of the turbine. The bucket10 of Fig. 1A has a shroud 65 on one end of the airfoil30. The bucket 11 of Fig. 1B lacks the shroud. Any othertype of bucket design may be used herein.[0013] As described above, the rotor 20 may have anumber of slots 25 for receiving the dovetails 60 of thebuckets 10. Likewise, the airfoils 30 of the buckets 10project into the hot gas stream so as to enable the kineticenergy of the stream to be converted into mechanicalenergy through the rotation of the rotor 20. The dovetail60 may include a first tang or tab 70 and a second tab80 extending therefrom. Similar designs may be usedherein. A gap 90 may be formed between the ends of thetabs 70, 80 of the dovetail 60 and the rotor 20. A highpressure cooling flow may escape via the gap 90 unlessa sealing system of some type is employed.[0014] Figs. 3-5 show a dovetail seal assembly 100 asis described herein. The dovetail seal assembly 100 maybe positioned about and within the first tab 70 of the dove-tail 60 of the bucket 10. The dovetail seal assembly 100may include a sealing slot 110. The sealing slot 110 mayextend about the perimeter of the first tab 70. The dimen-sions and shape of the sealing slot 110 may vary, in wholeor in part, about the tab 70. The sealing slot 110 may beformed with conventional machining techniques. Othertypes of manufacturing techniques also may be usedherein.[0015] The dovetail seal assembly 100 may include ahigh-pressure supply chamber 120 positioned about thefirst tab 70 directly above the sealing slot 110. Thehigh-pressure supply chamber 120 also may extendabout the perimeter of the first tab 70 and may have anydesired size or shape. The high-pressure supply cham-ber 120 also may be formed by conventional machiningor other types of manufacturing techniques. A deepersealing slot 110 may be used in place of a specific high-pressure supply chamber 120.[0016] The dovetail seal assembly 100 may include a

high-pressure supply hole 130 in communication with thehigh-pressure supply chamber 120. The high-pressuresupply hole 130 extends from the high-pressure supplychamber 120 to the exterior of the first tab 70 about ahigh-pressure side 140 thereof. The high-pressure sup-ply hole 130 may have any desired geometry or size. Thehigh-pressure supply hole 130 also may be formed byconventional machining or other types of manufacturingtechniques.[0017] The dovetail seal assembly 100 may include adeformable seal 150 positioned about the sealing slot110. The deformable seal 150 may have a substantiallysquare cross-section, a nearly circular cross-section, a"c"-shape, or any other desired design. Specifically, anaxial or a radial c-seal may be used. The deformable seal150 may be made out of a woven graphite, woven metal,woven intermetallic, woven ceramic, sintered metal/graphite, vapor deposited graphite on a metal backing,hybrids of metal/graphite/ceramics, and other types ofdeformable materials. The deformable seal 150 may fillthe sealing slot 110 as well as the gap 90 between thebucket 10 and rotor 20. Any number of seals 150 andsupply holes 130 may be used herein.[0018] In use, high-pressure air or other fluids from thehigh-pressure side 140 of the first tab 70 of the dovetail60 extends into the high-pressure supply hole 130 andthe high-pressure supply chamber 120. The high-pres-sure air presses or exerts a force against the deformableseal 150. The deformable seal 150 thus is forced againstthe rotor 20 such that the gap 90 is filled and high-pres-sure air is not allowed to leak therethrough. Specifically,the compressive force or other force on the deformableseal 150 counteracts the centrifugal loading force presentas the bucket 10 rotates. The deformable seal 150 sealsthe gap 90 in whole or in part. Other types of sealingforces may be used herein.[0019] The deformable seal 150 also may be used withother sealing systems and methods. The dovetail sealassembly 100 also may be used with the second tab 80and elsewhere.[0020] It should be apparent that the foregoing relatesonly to certain embodiments of the present applicationand that numerous changes and modifications may bemade herein by one of ordinary skill in the art withoutdeparting from the scope of the invention as defined bythe following claims.

Claims

1. A dovetail seal assembly (100) for sealing a gap (90)between a bucket dovetail (60) and a rotor (20), com-prising a bucket dovetail and a deformable seal:

a sealing slot (110) positioned about the dovetail(60);a high-pressure supply hole (130) in communi-cation with the sealing slot (110); and

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a deformable seal (150) positioned about thesealing slot (110) and into the gap (90), char-acterised in that high pressure air suppliedthrough the high-pressure supply hole (130) ex-erts a force against the deformable seal (150)whereby when the dovetail seal assembly ismounted in connection with the rotor the deform-able seal (15) is forced against the rotor (20)counter to a centrifugal load on the deformableseal (150).

2. The dovetail seal assembly (100) of claim 1, furthercomprising a high-pressure supply chamber (120)positioned between the sealing slot (110) and thehigh-pressure supply hole (130).

3. The dovetail seal assembly (100) of claim 1 or 2,wherein the sealing slot (110) extends about a pe-rimeter of a tab (70) of the dovetail (60) in whole orin part.

4. The dovetail seal assembly (100) of claim 3, whereinthe sealing slot (110) comprises a variable depthabout the perimeter of the tab (70) of the dovetail(60) in whole or in part.

5. The dovetail seal assembly (100) of any of the pre-ceding claims, wherein the high-pressure supplyhole (130) communicates with a high-pressure side(140) of the dovetail (60).

6. The dovetail seal assembly (100) of any of the pre-ceding claims, wherein the deformable seal (150)comprises a graphite or a braided metal seal.

7. The dovetail seal assembly (100) of any of the pre-ceding claims, wherein the deformable seal (150)comprises a substantially square cross-section.

8. The dovetail seal assembly (100) of any of the pre-ceding claims, wherein the deformable seal (150)comprises a substantially circular cross-section.

9. A method of sealing a gap (90) between a bucketdovetail (60) and a rotor (20), comprising:

positioning a deformable seal (150) within asealing slot (110) of the dovetail (60);forcing high-pressure fluid through the dovetail(60); andforcing the deformable seal (150) against therotor (20) with the high-pressure fluid, counterto a centrifugal loading on the deformable seal(150).

10. The method of claim 9, further comprising machiningthe sealing slot into the dovetail.

11. The method of claim 9 or 10, further comprising ma-chining a supply hole into the dovetail.

12. The method of any of claims 9 to 11, further com-prising sealing the gap (90) with the deformable seal(150) in whole or in part.

Patentansprche

1. Schwalbenschwanz-Dichtungsanordnung (100)zum Abdichten eines Spaltes (90) zwischen einemSchaufelschwalbenschwanz (60) und einem Rotor(20), aufweisend:

einen Schaufelschwalbenschwanz und eineverformbare Dichtung;einen um den Schwalbenschwanz (60) herumpositionierten Dichtungsschlitz (110);ein Hochdruckzufhrungsloch (130) in Verbin-dung mit dem Dichtungsschlitz (110);eine um den Dichtungsschlitz (110) herum undin den Spalt (90) positionierte verformbare Dich-tung (150), dadurch gekennzeichnet, dassdurch das Hochdruckzufhrungsloch (130) zu-gefhrte Hochdruckluft eine Kraft gegen die ver-formbare Dichtung (150) ausbt, wodurch,wenn die Schwalbenschwanz-Dichtungsanord-nung in Verbindung mit dem Rotor montiert ist,die verformbare Dichtung (150) an den Rotor(20) gegen eine Zentrifugalbelastung auf derverformbaren Dichtung (150) gedrckt wird.

2. Schwalbenschwanzanordnung (100) nach An-spruch 1, welche ferner eine Hochdruckzufhrungs-kammer (120) aufweist, die zwischen dem Dich-tungsschlitz (110) und dem Hochdruckzufhrungs-loch (130) positioniert ist.

3. Schwalbenschwanzanordnung (100) nach An-spruch 1 oder 2, wobei sich der Dichtungsschlitz(110) insgesamt oder teilweise um einen Umfangeines Ansatzes (70) des Schwalbenschwanzes (60)erstreckt.

4. Schwalbenschwanzanordnung (100) nach An-spruch 3, wobei der Dichtungsschlitz (110) insge-samt oder teilweise eine variable Tiefe um den Um-fang des Ansatzes (70) des Schwalbenschwanzes(60) aufweist.

5. Schwalbenschwanzanordnung (100) nach einemder vorstehenden Ansprche, wobei das Hoch-druckzufhrungsloch (130) mit einer Hochdrucksei-te (140) des Schwalbenschwanzes (60) in Verbin-dung steht.

6. Schwalbenschwanzanordnung (100) nach einem

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der vorstehenden Ansprche, wobei die verformba-re Dichtung (150) eine Graphit- oder Flechtmetall-dichtung aufweist.

7. Schwalbenschwanzanordnung (100) nach einemder vorstehenden Ansprche, wobei die verformba-re Dichtung (150) einen im Wesentlichen quadrati-schen Querschnitt aufweist.

8. Schwalbenschwanzanordnung (100) nach einemder vorstehenden Ansprche, wobei die verformba-re Dichtung (150) einen im Wesentlichen rundenQuerschnitt aufweist.

9. Verfahren zum Abdichten eines Spaltes (90) zwi-schen einem Schaufelschwalbenschwanz (90) undeinem Rotor (20), mit den Schritten:

Positionieren einer verformbaren Dichtung(150) in einem Dichtungsschlitz (110) desSchwalbenschwanzes (60);Drcken von Hochdruckfluid durch den Schwal-benschwanz (60); undAndrcken der verformbaren Dichtung (150) anden Rotor (20) mit dem Hochdruckfluid, gegeneine Zentrifugalbelastung auf der verformbarenDichtung (150).

10. Verfahren nach Anspruch 9, ferner mit dem Schrittder Einarbeitung des Dichtungsschlitzes in denSchwalbenschwanz.

11. Verfahren nach Anspruch 9 oder 10, ferner mit demSchritt der Einarbeitung eines Zufhrungsloches inden Schwalbenschwanz.

12. Verfahren nach einem der Ansprche 9 bis 11, fernermit dem Schritt der gesamten oder teilweisen Ab-dichtung des Spaltes (90) mit der verformbaren Dich-tung (150).

Revendications

1. Systme dtanchit (100) de queue daronde pourassurer ltanchit dun intervalle (90) entre unequeue daronde (60) dailette et un rotor (20), com-portant une queue daronde dailette et un jointdtanchit dformable, comprenant :

une rainure dtanchit (110) mnage autourde la queue daronde (60) ;un trou dalimentation haute pression (130)communiquant avec la rainure dtanchit(110) ; etun joint dtanchit dformable (150) disposautour de la rainure dtanchit (110) et pn-trant dans lintervalle (90), caractris en ce

que de lair haute pression fourni via le troudalimentation haute pression (130) exerceune force contre le joint dformable (150), lasuite de quoi, lorsque le systme dtanchitde queue daronde est mont par rapport au ro-tor, le joint dformable (15) est appuy contrele rotor (20) lencontre dune sollicitation cen-trifuge du joint dformable (150).

2. Systme dtanchit (100) de queue daronde se-lon la revendication 1, comportant en outre unechambre dalimentation haute pression (120) pla-ce entre la rainure dtanchit (110) et le trou dali-mentation haute pression (130).

3. Systme dtanchit (100) de queue daronde se-lon la revendication 1 ou 2, dans lequel la rainuredtanchit (110) stend entirement ou partielle-ment sur un pourtour dune patte (70) de la queuedaronde (60).

4. Systme dtanchit (100) de queue daronde se-lon la revendication 3, dans lequel la rainure dtan-chit (110) a une profondeur variable entirementou partiellement sur le pourtour de la patte (70) dela queue daronde (60).

5. Systme dtanchit (100) de queue daronde se-lon lune quelconque des revendications prcden-tes, dans lequel le trou dalimentation haute pres-sion (130) communique avec un ct haute pression(140) de la queue daronde (60).

6. Systme dtanchit (100) de queue daronde se-lon lune quelconque des revendications prcden-tes, dans lequel le joint dformable (150) a un jointen mtal tress ou en graphite.

7. Systme dtanchit (100) de queue daronde se-lon lune quelconque des revendications prcden-tes, dans lequel le joint dformable (100) a une sec-tion transversale sensiblement carre.

8. Systme dtanchit (100) de queue daronde se-lon lune quelconque des revendications prcden-tes, dans lequel le joint dformable (150) a une sec-tion transversale sensiblement circulaire.

9. Procd pour assurer ltanchit dun intervalle(90) entre une queue daronde (60) dailette et unrotor (20), comportant :

la mise en place dun joint dtanchit dfor-mable (150) dans une rainure dtanchit (110)de la queue daronde (60) ;linjection dun fluide haute pression traversla queue daronde (60) ; etlappui du joint dformable (150) contre le rotor

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(20) laide du fluide haute pression, len-contre dune sollicitation centrifuge du joint d-formable (150).

10. Procd selon la revendication 9, comportant enoutre lusinage de la rainure dtanchit dans laqueue daronde.

11. Procd selon la revendication 9 ou 10, comportantlusinage dun trou dalimentation dans la queuedaronde.

12. Procd selon lune quelconque des revendications9 11 ; comportant en outre lobturation tanche,complte ou partielle, de lintervalle (90) par le jointdtanchit dformable (150).

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REFERENCES CITED IN THE DESCRIPTION

This list of references cited by the applicant is for the readers convenience only. It does not form part of the Europeanpatent document. Even though great care has been taken in compiling the references, errors or omissions cannot beexcluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description

US 6375429 B [0005] US 2224082 A [0006]

EP 1731714 A [0007]

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