Claims:1. A rotor comprising:
an airfoil;
a shank coupled to the airfoil, wherein the shank comprises a cover plate; and
an angel wing coupled to the cover plate, wherein the angel wing comprises an outer peripheral surface and a plurality of projections coupled to the outer peripheral surface.

2. The rotor of claim 1, wherein the projections are spaced apart from each other and disposed along a circumferential direction of the angel wing.

3. The rotor of claim 1, wherein at least one projection of the plurality of projections comprises an airfoil-shaped projection.

4. The rotor of claim 1, wherein the angel wing comprises an arm portion protruding from the cover plate and an up-turn portion coupled to the arm portion, wherein the up-turn portion is oriented along a radial direction of the rotor or inclined at a pre-defined angle relative to a radial axis of the rotor.

5. The rotor of claim 4, wherein the outer peripheral surface comprises an outer peripheral surface of at least one of the arm portion and the up-turn portion.

6. A turbine comprising:
a stator comprising a rub strip; and
a rotor comprising:
an airfoil;
a shank coupled to the airfoil, wherein the shank comprises a cover plate; and
an angel wing coupled to the cover plate and disposed facing the rub strip to form a seal, wherein the angel wing comprises an outer peripheral surface and a plurality of projections coupled to the outer peripheral surface and wherein the plurality of projections is disposed facing a cavity defined between the stator and the rotor.

7. The turbine of claim 6, wherein the stator comprises a plurality of stators and the rotor comprises a plurality of rotors, wherein each of the stators and rotors are disposed alternately and wherein each pair of mutually adjacent rotor and stator defines a stage from a plurality of stages of the turbine.

8. The turbine of claim 7, wherein one stator from the plurality of stators, further comprises a support ring.
9. The turbine of claim 8, wherein the seal comprises an intra-stage seal formed between the support ring and one rotor from the plurality of rotors.

10. The turbine of claim 7, wherein one stator from the plurality of stators, further comprises a stator diaphragm.

11. The turbine of claim 10, wherein the seal comprises an inter-stage seal formed between the stator diaphragm and one rotor from the plurality of rotors.

12. The turbine of claim 6, wherein the cavity comprises at least one of a wheel space cavity, a trench cavity, and a buffer cavity, wherein the wheel space cavity is formed between the rotor and a support ring of the stator, wherein the trench cavity and the buffer cavity are defined between a peripheral side portion of the stator, a peripheral side portion of the rotor, and a spacer wheel of the rotor.

13. The turbine of claim 6, wherein the projections are spaced apart from each other and disposed along a circumferential direction of the angel wing.

14. The turbine of claim 6, wherein at least one projection of the plurality of projections, comprises an airfoil-shaped projection.

15. The turbine of claim 6, wherein the angel wing comprises an arm portion protruding from the cover plate and an up-turn portion coupled to the arm portion, wherein the up-turn portion is oriented along a radial direction of the rotor or inclined at a pre-defined angle relative to a radial axis of the rotor.

16. The turbine of claim 15, wherein the outer peripheral surface comprises an outer peripheral surface of at least one of the arm portion and the up-turn portion.

17. A method comprising:
directing an exhaust gas stream from a combustor to a turbine; wherein the turbine comprises a stator and a rotor, wherein the rotor comprises an airfoil, a shank coupled to the airfoil, and an angel wing, wherein the shank comprises a cover plate and an angel wing coupled to the cover plate, wherein the angel wing comprises an outer peripheral surface and a plurality of projections coupled to the outer peripheral surface, and wherein directing an exhaust gas stream comprises:
directing a first portion of the exhaust gas stream along the stator and the rotor, wherein the stator comprises a rub strip; and
leaking a second portion of the exhaust gas stream from a cavity to the rotor through a seal, wherein the cavity is defined between the stator and the rotor, and wherein the angel wing is disposed facing the rub strip to form the seal;
directing a compressed fluid from a compressor to the turbine, bypassing the combustor, through the seal; and
regulating the second portion of the exhaust gas stream and the compressed fluid through the seal, using the plurality of projections disposed facing the cavity.

18. The method of claim 17, wherein regulating the second portion of the exhaust gas stream and the compressed fluid through the seal, comprises directing the second portion and the compressed fluid along a radial direction of the rotor, against the rub strip.

19. The method of claim 17, wherein the seal comprises an intra-stage seal.

20. The method of claim 17, wherein the seal comprises an inter-stage seal.
, Description:BACKGROUND
[0001] Embodiments of the present invention relate to turbines, and more specifically to a seal defined by an angel wing of a rotor and a rub strip of a stator of a turbine.
[0002] Machines such as gas turbines and steam turbines typically include rotors and stators. Tips of the rotors are generally surrounded by a casing. A shank of each rotor is flanked on upstream and downstream ends by shrouds of the stators. In such a configuration, the shank includes an angel wing and the shroud includes a rub strip. The angel wing is disposed facing the rub strip to form a seal there-between.
[0003] Efficiency of the turbine may depend in part on a clearance defined between the angel wing and the rub strip. If the clearance is too large, excessive compressed air or exhaust gas stream may leak through the clearance, thereby decreasing the turbine efficiency. If the clearance is too small, the angel wing may contact the adjacent rub strip during certain transient turbine operating conditions, thereby damaging the angel wing and the rib strip.
[0004] Accordingly, there is a need for an enhanced seal and an associated method.
BRIEF DESCRIPTION
[0005] In accordance with one exemplary embodiment, a rotor is disclosed. The rotor includes an airfoil, a shank including a cover plate, and an angel wing. The shank is coupled to the airfoil and the angel wing is coupled to the cover plate. The angel wing includes an outer peripheral surface and a plurality of projections coupled to the outer peripheral surface.
[0006] In accordance with another exemplary embodiment, a turbine is disclosed. The turbine includes a stator having a rub strip and a rotor having an airfoil, a shank, and an angel wing. The shank includes a cover plate and is coupled to the airfoil. The angel wing is coupled to the cover plate and is disposed facing the rub strip to form a seal. The angel wing includes an outer peripheral surface and a plurality of projections coupled to the outer peripheral surface. The plurality of projections is disposed facing a cavity defined between the stator and the rotor.
[0007] In accordance with another exemplary embodiment, a method is disclosed. The method involves directing an exhaust gas stream from a combustor to a turbine having a stator and a rotor. The stator includes a rub strip and the rotor includes an airfoil, a shank coupled to the airfoil, and an angel wing. The shank includes a cover plate and the angel wing is coupled to the cover plate. The angel wing includes an outer peripheral surface and a plurality of projections coupled to the outer peripheral surface. The method further involves directing a first portion of the exhaust gas stream along the stator and the rotor and leaking a second portion of the exhaust gas stream from a cavity to the rotor through a seal. The cavity is defined between the stator and the rotor. The angel wing is disposed facing the rub strip to form the seal. The method further involves directing a compressed fluid from a compressor to the turbine, bypassing the combustor through the seal. Further, the method involves regulating the second portion of the exhaust gas stream and the compressed fluid through the seal, using the plurality of projections disposed facing the cavity.
DRAWINGS
[0008] These and other features and aspects of embodiments of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
[0009] FIG. 1 is a cross-sectional view of a portion of a turbomachine in accordance with one exemplary embodiment;
[0010] FIG. 2 is a perspective view of a rotor of a turbine, having a plurality of projections in accordance with the exemplary embodiment of FIG.1;
[0011] FIG. 3 is a schematic cross-sectional view of an inter-stage seal in accordance with the exemplary embodiment of FIG. 1;
[0012] FIG. 4 is a schematic cross-sectional view of an intra-stage seal in accordance with the exemplary embodiment of FIG. 1;
[0013] FIG. 5 is a perspective view of an angel wing having an angled projection in accordance with another exemplary embodiment;
[0014] FIG. 6 is a perspective view of an angel wing having a radial projection in accordance with another exemplary embodiment;
[0015] FIG. 7 is a perspective view of an inclined angel wing having a projection in accordance with another exemplary embodiment;
[0016] FIG. 8 is a perspective view of an angel wing having an airfoil-shaped projection in accordance with another exemplary embodiment;
[0017] FIG. 9 is a schematic diagram of an aft seal portion of an inter-stage seal in accordance with another exemplary embodiment;
[0018] FIG. 10 is a schematic diagram depicting a fluid flow pattern of a seal in accordance with one exemplary embodiment; and
[0019] FIG. 11 is a flow diagram of an exemplary method for controlling flow of a fluid through a seal in accordance with one exemplary embodiment.
DETAILED DESCRIPTION
[0020] Embodiments discussed herein disclose a seal, such as an inter-stage seal or an intra-stage seal of a turbine. The turbine includes a stator having a rub strip and a rotor having an angel wing. The angel wing is disposed facing the rub strip to form a seal there-between. Such a seal is configured to control leakage of at least one of an exhaust gas stream and a compressed fluid through a clearance defined between the angel wing and the rub strip. The angel wing includes an outer peripheral surface and a plurality of projections coupled to the outer peripheral surface. The projections may be spaced apart from each other along a circumferential direction of the angel wing. Further, the plurality of projections is disposed facing a cavity defined between the stator and the rotor. The cavity may include at least one of a wheel space cavity, a trench cavity, and a buffer cavity. In one embodiment, at least one projection may be an airfoil-shaped projection. The plurality of projections is configured to deflect flow of at least one of the exhaust gas stream and the compressed fluid along a radial direction of the rotor, against the rub strip. In certain embodiments, the exemplary turbine includes a stator having a rub strip and a rotor having an airfoil, a shank, and an angel wing. The shank includes a cover plate and is coupled to the airfoil. The angel wing is disposed facing the rub strip to form a seal.
[0021] FIG. 1 illustrates a cross-sectional view of a portion of a turbomachine 10 in accordance with one exemplary embodiment. The turbomachine 10 includes a compressor 12, a combustor 14, and a turbine 16. The compressor 12 is coupled to the combustor 14. The turbine 16 is coupled to the combustor 14. Further, the turbine 16 is also coupled to the compressor 12, bypassing the combustor 14. In one embodiment, the turbine 16 drives the compressor 12 via a mid-shaft 24.
[0022] The turbine 16 includes a plurality of rotors 38, 40, 42, 44 connected to the mid-shaft 24 for rotation therewith. The turbine 16 further includes a plurality of stators 54, 56, 58, 60 (also referred to as stator blades) coupled to a casing 70. Each of the plurality of stators 54, 56, 58, 60 and each of the plurality of rotors 38, 40, 42, 44 are disposed alternately. Each pair of mutually adjacent rotors 38, 40, 42, 44 and stators 54, 56, 58, 60 defines a stage to form a plurality of stages of the turbine 16. In the illustrated embodiment, the turbine 16 includes four-stages, where a first stage is represented by the stator 54 and the rotor 38, a second stage is represented by the stator 56 and the rotor 40, a third stage is represented by the stator 58 and the rotor 42, and a last stage is represented by the stator 60 and the rotor 44. The turbine 16 further includes a plurality of spacer wheels 62, 64, 66 which is coupled to and disposed alternately between adjacent rotors 38, 40, 42, 44.
[0023] The plurality of rotors 38, 40, 42, 44 includes a plurality of rotor blades 46, 48, 50, 52 (also referred to herein as airfoils) respectively. Further, the plurality of rotors 38, 40, 42, 44 includes a plurality of shanks 72, 74, 76, 78 respectively. Each shank 72, 74, 76, 78 is coupled to a corresponding rotor disk of a plurality of rotor disks (not labeled in FIG. 1). Each of the plurality of rotors 38, 40, 42, 44 further includes at least two angel wings. The rotor 38 includes angel wings 80, 82 and the rotor 40 includes angel wings 84, 86. For ease of illustration, the angel wings of rotors 42, 44 are not labeled. The angel wings 80, 82 are coupled to the shank 72 and the angel wings 84, 86 are coupled to the shank 74. Similarly, angel wings of the rotor 42 are coupled to the shank 76 and the angel wings of the rotor 44 are coupled to the shank 78. Further, each of the angel wings 80, 82, 84, 86 includes an outer peripheral surface and a plurality of projections (not shown in FIG. 1) coupled to the outer peripheral surface.
[0024] The stator 54 includes a support ring 94 which defines a cavity 96 between the stator 54 and the rotor 38. The plurality of stators 56, 58, 60 includes stator diaphragms 98, 100, 102 respectively. The stator diaphragms 98, 100, 102 define respective cavities 104, 106, 108 between the respective stators 56, 58, 60 and rotors 40, 42, 44. Each of the plurality of stators 54, 56, 58, 60 includes at least one rub strip. The stator 54 includes the rub strip 88 and the stator 56 includes rub strips 90, 92. For ease of illustration, the rub strips of the stators 58, 60 are not labeled. The rub strip 88 is coupled to support ring 94 and the rub strips 90, 92 are coupled to the stator diaphragm 98. Similarly, the rub strips of the stator 58 are coupled to the stator diaphragm 100 and the rub strips of the stator 60 are coupled to the stator diaphragm 102.
[0025] The angel wings 80, 82, 84 are disposed facing rub strips 88, 90, 92 to form seals 110, 112. Specifically, the angel wing 80 is disposed facing the rub strip 88 to form the seal 110 (also referred to herein as an intra-stage seal) there-between the support ring 94 and the rotor 38. In other words, the intra-stage seal 110 is formed between the support ring 94 and the rotor 38. The angel wings 82, 84 are disposed facing the respective rub strips 90, 92 to form the seal 112 (also referred to herein as an inter-stage seal) there-between the stator diaphragm 98 and the rotor 40. In other words, the inter-stage seal 112 is formed between the stator diaphragm 98 and the rotor 40. In certain embodiments, the inter-stage seal 112 may include a forward seal portion, an intermediate seal portion, and an aft seal portion which are discussed in greater detail below.
[0026] During operation, the compressor 12 is configured to receive a fluid, such as air and compress the received fluid to generate a compressed fluid 36. The combustor 14 is configured to receive the compressed fluid 36 from the compressor 12 and a fuel 18 such as a natural gas from fuel injectors (not shown in FIG. 1). The combustor 14 is further configured to burn a mixture of the fuel 18 and the compressed fluid 36 within a combustion zone (not labeled in FIG. 1) to generate an exhaust gas stream 28. The turbine 16 is configured to receive the exhaust gas stream 28 from the combustor 14 along a first flow path 26. The turbine 16 is further configured to expand the exhaust gas stream 28 through multiple stages of the turbine 16 so as to convert energy in the exhaust gas stream 28 to work.
[0027] In one embodiment, a first portion 28a of the exhaust gas stream 28 is directed along the first flow path 26 (i.e. along the plurality of stators blades 54, 56, 58, 60 and the plurality of rotors blades 46, 48, 50, 52). In such embodiments, a second portion 28b of the exhaust gas stream 28 leaks through the inter-stage seal 112. Specifically, the second portion 28b is directed from the cavity 104 to the rotor blade 48 through the inter-stage seal 112. In one embodiment, a portion 36a of the compressed fluid 36 flows along a second flow path 34 extending from the compressor 12 to the turbine 16, bypassing the combustor 14. Specifically, the portion 36a of the compressed fluid 36 is directed from the cavity 96 to the rotor blade 46 through the intra-stage seal 110. In one or more embodiments, each of the cavities 104, 106, 108 is a trench cavity or a buffer cavity. The cavities 104, 106, 108 are fluidly coupled to the first flow path 26 for receiving the leaked second portion 28b of the exhaust gas stream 28. The cavity 96 is a wheel space cavity fluidly coupled to the second flow path 34 for receiving the portion 36a of the compressed fluid 36 from the compressor 12.
[0028] The turbomachine 10 further includes a labyrinth seal system 68 disposed in at least one pre-defined location of the turbine 16. In one embodiment, the pre-defined location is in the second flow path 34 extending from the compressor 12 to the turbine 16. In another embodiment, the pre-defined location may be in a flow path extending between a tip of the respective rotor blades 46, 48, 50, 52 and the casing 70. In yet another embodiment, the pre-defined location may be in a flow path extending between a tip of the respective stator 56, 58, 60 and the respective spacer wheels 62, 64, 66.
[0029] FIG. 2 is a perspective view of the rotor 40 in accordance with the exemplary embodiment of FIG.1.
[0030] The rotor 40 includes the airfoil 48 (also referred as rotor blade), the shank 74, and the angel wings 84, 86. The airfoil 48 is mounted on the shank 74 having a platform 120 and a shank pocket 122. The shank 74 further includes cover plates 124, 126 and a dovetail 128 for coupling the rotor 40 to a rotor disk (as shown in FIG. 1). In the illustrated embodiment, the rotor 40 includes two angel wings 84 coupled to the cover plate 124 (also referred herein as a forward cover plate) and two angel wings 86 coupled to the cover plate 126 (also referred herein as an aft cover plate). In certain embodiments, the rotor 40 may include only one angel wing 84 coupled to the forward cover plate 124 and only one angel wing 86 coupled to the aft cover plate 126. The number of angel wings 84, 86 may vary depending on the application and design criteria.
[0031] The airfoil 48 includes a leading edge 130 facing a flow of the exhaust gas stream 28 directed along the first flow path 26 and a trailing edge 132 for directing the exhaust gas stream to the adjacent stator 58 (as shown in FIG. 1). The angel wing 84 (also referred to as “forward angel wing”) includes an outer peripheral surface 134 and a plurality of projections 136 coupled to the outer peripheral surface 134. The projections 136 are spaced apart from each other and disposed along a circumferential direction 180 of the angel wing 84. In one embodiment, the angel wing 86 (also referred to as “aft angel wing”) may not include the plurality of projections 136. The outer peripheral surface 134 extends along a radial direction 138 of the rotor 40. The forward angel wing 84 includes an arm portion 140 protruding from the cover plate 124 and an up-turn portion 144 coupled to the arm portion 140. The aft angel wing 86 includes an arm portion 142 protruding from the cover plate 126 and an up-turn portion 146 coupled to the arm portion 142. In the illustrated embodiment, the arm portions 140, 142 are oriented along an axial direction 150 of the rotor 40 and the up-turn portions 144, 146 are oriented along the radial direction 138 of the rotor 40. Specifically, the plurality of projections 136 of FIG. 2 is disposed along the up-turn portion 144 of the forward angel wing 84. In the illustrated embodiment, the outer peripheral surface 134 is an outer peripheral surface of the up-turn portion 144 of the angel wing 84. In certain embodiments, a plurality of rotors 40 is disposed adjacent to each other along the circumferential direction 180 of the engine. In such embodiments, the outer peripheral surface 134 is an axisymmetric surface.
[0032] FIG. 3 is a schematic cross-sectional view of inter-stage seal 112 in accordance with the exemplary embodiment of FIG. 1. The inter-stage seal 112 is defined by interacting components, such as the rotors 38, 40, the stator 56, and the spacer wheel 62. The spacer wheel 62 includes teeth 148 spaced apart from other and disposed along an axial direction 150 of the inter-stage seal 112. The inter-stage seal 112 includes a forward seal portion 112a, an intermediate seal portion 112b, and an aft seal portion 112c. The forward seal portion 112a is defined between a peripheral side portion 56a of the stator 56 and a peripheral side portion 38a of the rotor 38. Specifically, the rub strip 90 of the stator 56 is disposed facing the angel wing 82 of the rotor 38 to form the forward seal portion 112a there-between. The intermediate seal portion 112b (also referred as “labyrinth seal” or “near flow path seal”) is defined between a stepped end portion 56b of the stator 56 and the teeth 148 of the spacer wheel 62. The aft seal portion 112c is defined between a peripheral side portion 56c of the stator 56 and a peripheral side portion 40a of the rotor 40. Specifically, the rub strip 92 of the stator 56 is disposed facing the angel wing 84 on the forward side of the rotor 40 to form the aft seal portion 112c there-between.
[0033] The inter-stage seal 112 further includes a cavity 104 defined between the peripheral side portion 56c of the stator 56, the peripheral side portion 40a located below the angel wing 84 of the rotor 40, and the spacer wheel 62. The cavity 104 is a buffer cavity. In some other embodiments, the cavity 104 may be a trench cavity defined between the peripheral side portion 56c of the stator 56 and the peripheral side portion 40a of the rotor 40. As discussed previously, the angel wing 84 includes the outer peripheral surface 134 and the plurality of projections 136 coupled to the outer peripheral surface 134. For ease of illustration, only one projection 136 is shown in FIG. 3 and should not be construed as a limitation of the present technique. In the illustrated embodiment, the outer peripheral surface 134 is an outer peripheral surface of an up-turn portion 144 of the angel wing 84. The outer peripheral surface 134 extends along a radial direction 138 of the rotor 40 and the plurality of projections 136 is disposed along the radial direction 138 of the rotor 40. Specifically, the plurality of projections 136 is coupled to and disposed on the up-turn portion 144 of the angel wing 84. In the embodiment of FIG. 3, the angel wing 82 does not include the plurality of projections 136.
[0034] During operation, the exhaust gas stream 28 is directed along the first flow path 26 from the combustor 14 to the turbine 16. In such embodiments, the first portion 28a of the exhaust gas stream 28 is directed along the rotor blades 46, 48 and the stator 56. The second portion 28b of the exhaust gas stream 28 leaks from the rotor blade 46 towards the rotor blade 48 through the inter-stage seal 112, bypassing the stator 56. The forward seal portion 112a is configured to regulate a flow of the second portion 28b by recirculating the second portion 28b between the angel wing 82 and the rub strip 90. Further, the intermediate seal portion 112b is configured to regulate the flow of the second portion 28b by further recirculating the second portion 28b between the teeth 148 and the stepped end portion 56b. Similarly, the aft seal portion 112c is configured to regulate the flow of the second portion 28b by recirculating the second portion 28b between the angel wing 84 and the rub strip 92. In such embodiments, the projection 136 is configured to direct the second portion 28b along the radial direction 138 against the rub strip 92 so as to regulate the flow of the second portion 28b to the rotor blade 48.
[0035] FIG. 4 is a schematic cross-sectional view of the intra-stage seal 110 in accordance with the exemplary embodiment of FIG. 1. The intra-stage seal 110 is defined by interacting components, such as the support ring 94 of the stator 54, and the rotor 38. The support ring 94 is coupled to a tip 152 of the stator 54. The support ring 94 includes the rub strip 88 and the rotor 38 includes the angel wing 80. Specifically, the rub strip 88 is disposed facing the angel wing 80 to form the intra-stage seal 110 there-between.
[0036] The intra-stage seal 110 further includes the cavity 96 defined between a peripheral side portion 94a of the support ring 94 and a peripheral side portion 38b of the rotor 38. In one embodiment, the cavity 96 is a wheel space cavity. The angel wing 80 includes an outer peripheral surface 154 and a plurality of projections 156 coupled to the outer peripheral surface 154. For ease of illustration, only one projection 156 is shown in FIG. 4 and should not be construed as a limitation of the present technique. In the illustrated embodiment, the outer peripheral surface 154 is an outer peripheral surface of an up-turn portion 141 of the angel wing 80. The outer peripheral surface 154 extends along a radial direction 138 of the rotor 38 and the plurality of projections 156 is disposed along the radial direction 138 of the rotor 38. Specifically, the plurality of projections 156 is coupled to and disposed on the up-turn portion 141 of the angel wing 80.
[0037] During operation, the compressed fluid 36 is directed from the compressor to the combustor. In such embodiments, a portion 36a of the compressed fluid 36 is directed along the second flow path 34 from the compressor to the rotor blade 46 of the turbine through the intra-stage seal 110. The intra-stage seal 110 is configured to regulate a flow of the portion 36a by recirculating the portion 36a between the angel wing 80 and the rub strip 88. In such embodiments, the plurality of projections 156 is configured to direct the portion 36a along the radial direction 138 against the rub strip 88 so as to regulate the flow of the portion 36a to the rotor blade 46. Further, the rub strip 88 and the angel wing 80 are configured to regulate a flow of the second portion 28b of the exhaust gas stream 28 into the cavity 96.
[0038] FIG. 5 is a perspective view of an angel wing 200 in accordance with another exemplary embodiment. The angel wing 200 includes an arm portion 202 protruding from a cover plate of a shank (not shown in FIG. 5) and an up-turn portion 204 coupled to the arm portion 202. The up-turn portion 204 is oriented along a radial direction 138. The angel wing 200 includes an outer peripheral surface 206 and a projection 208 coupled to the outer peripheral surface 206. For ease of illustration, although only one projection 208 is shown in FIG. 5, the angel wing 200 typically includes the plurality of projections 208. Specifically, the plurality of projections 208 is disposed on the up-turn portion 204. In the illustrated embodiment, the outer peripheral surface 206 is an outer peripheral surface of the up-turn portion 204 of the angel wing 200. The outer peripheral surface 206 extends along the radial direction 138 of a rotor and the plurality of projections 208 is oriented at a pre-defined angle 214 with respect to a radial axis 139 of the rotor. In one embodiment, the pre-defined angle is in a range from about 10 degrees to about 45 degrees. During operation, the plurality of projections 208 is configured to direct a portion of an exhaust gas stream or a portion of a compressed fluid, along the radial direction 138 against a rub strip 210, thereby regulating fluid flow through a clearance 212 defined between the angel wing 200 and the rub strip 210.
[0039] FIG. 6 is a perspective view of an angel wing 300 in accordance with another exemplary embodiment. The angel wing 300 includes an outer peripheral surface 306 and a plurality of projections 308 coupled to the outer peripheral surface 306. For ease of illustration, although only one projection 308 is shown in FIG. 6, the angel wing 300 typically includes the plurality of projections 308. Specifically, the plurality of projections 308 is disposed on an up-turn portion 304 of the angel wing 300. The up-turn portion 304 is oriented along a radial direction 138 of a rotor. In the illustrated embodiment, the outer peripheral surface 306 is an outer peripheral surface of the up-turn portion 304. The outer peripheral surface 306 extends along the radial direction 138 and the plurality of projections 308 is oriented along the radial direction 138. During operation, the plurality of projections 308 is configured to direct a portion of an exhaust gas stream or a portion of a compressed fluid, along the radial direction 138 against a rub strip 310. Thereby, fluid flow is regulated through a clearance 312 defined between the angel wing 300 and the rub strip 310.
[0040] FIG. 7 is a perspective view of an angel wing 400 in accordance with another exemplary embodiment. The angel wing 400 includes an arm portion 402 protruding from a cover plate of a shank (not shown in FIG. 7) and an up-turn portion 404 coupled to the arm portion 402. In the illustrated embodiment, the up-turn portion 404 is inclined at a pre-defined angle 414 relative to a radial axis 139 of the rotor. In one embodiment, the pre-defined angle 414 is in a range from about 10 degrees to about 40 degrees. The angel wing 400 includes an outer peripheral surface 406 and a plurality of projections 408 coupled to the outer peripheral surface 406. For ease of illustration, although only one projection 408 is shown in FIG. 7, the angel wing 400 typically includes the plurality of projections 408. Specifically, the plurality of projections 408 is disposed on the up-turn portion 404 and the arm portion 402 of the angel wing 400. In the illustrated embodiment, the outer peripheral surface 406 is an outer peripheral surface of the arm portion 402 and the up-turn portion 404. The plurality of projections 408 is inclined at the pre-defined angle 414 relative to the radial axis 139 of the rotor. In some other embodiments, the plurality of projections 408 may be disposed only along the up-turn portion 404. During operation, the plurality of projections 408 is configured to direct a portion of an exhaust gas stream or a portion of a compressed fluid, along a radial direction 138 against a rub strip 410. Thereby, fluid flow is regulated through a clearance 412 defined between the angel wing 400 and the rub strip 410.
[0041] FIG. 8 is a perspective view of an angel wing 500 in accordance with another exemplary embodiment. The angel wing 500 includes an outer peripheral surface 506 and a plurality of projections 508 coupled to the outer peripheral surface 506. For ease of illustration, although only one projection 508 is shown in FIG. 8, the angel wing 500 typically includes the plurality of projections 508. Specifically, the plurality of projections 508 is disposed on an up-turn portion 504 of the angel wing 500. In the illustrated embodiment, the outer peripheral surface 506 is an outer peripheral surface of the up-turn portion 504. In the illustrated embodiment, the projection 508 is an airfoil-shaped projection including a leading edge 516 and a trailing edge 518. In certain other embodiments, a plurality of airfoil-shaped projections 508 may be disposed along a circumferential direction 180 of the angel wing 500. During operation, the plurality of projections 508 is configured to direct a portion of an exhaust gas stream or a portion of a compressed fluid, along a radial direction 138 against a rub strip 510. Thereby, fluid flow is regulated through a clearance 512 defined between the angel wing 500 and the rub strip 510.
[0042] FIG. 9 is a schematic diagram of an aft seal portion 600 of an inter-stage seal in accordance with another exemplary embodiment. The aft seal portion 600 is defined by interacting components such as a rotor 601, a stator 603, and a spacer wheel 605. The rotor 601 includes a set of angel wings 602 and the stator 603 includes rub strips 604. In the illustrated embodiment, the set of angel wings 602 include a first angel wing 602a and a second angel wing 602b. The rub strips 604 include a first rub strip 604a and a second rub strip 604b.
[0043] The second angel wing 602b is disposed downstream relative to the first angel wing 602a. The first angel wing 602a includes a first outer peripheral surface 606a and a first projection 608a coupled to the first outer peripheral surface 606a. Similarly, the second angel wing 602b includes a second outer peripheral surface 606b and a second projection 608b coupled to the second outer peripheral surface 606b. The first projection 608a is disposed on a first up-turn portion 610a of the first angel wing 602a and the second projection 608b is disposed on a second up-turn portion 610b of the second angel wing 602b. Specifically, the first outer peripheral surface 606a is an outer peripheral surface of the first up-turn portion 610a and the second peripheral surface 610b is an outer peripheral surface of the second up-turn portion 610b. The first rub strip 604a is disposed facing the first angel wing 602a to define a first seal portion 600a of the aft seal portion 600. The second rub strip 604b is disposed facing the second angel wing 602b to define a second seal portion 600b of the aft seal portion 600. The aft seal portion 600 further includes a buffer cavity 612 and a trench cavity 614. The buffer cavity 612 is defined between the rotor 601, the stator 603, and the spacer wheel 605. The trench cavity 614 is defined between the rotor 601, the stator 603, and the first angel wing 602a.
[0044] During operation, the first projection 608a is configured to receive a portion of a fluid 616 from the buffer cavity 612 and direct the portion of the fluid 616, along a radial direction 138 against the first rub strip 604a. Thereby, the fluid flow is regulated through a first clearance 618a defined between the first angel wing 602a and the first rub strip 604a. Further, the second projection 608b is configured to receive the portion of the fluid 616 from the trench cavity 614 and direct the portion of the fluid 616, along the radial direction 138 against the second rub strip 604b. Thereby, fluid flow is regulated through a second clearance 618b defined between the second angel wing 602b and the second rub strip 604b.
[0045] In certain other embodiments, the outer peripheral surface may relate to only an outer peripheral surface of an arm portion. In such embodiments, the plurality of projections may be coupled to and disposed on the arm portion.
[0046] FIG. 10 is a schematic diagram depicting a fluid flow pattern 700 in an aft seal portion 707 of an inter-stage seal 760 in accordance with one exemplary embodiment. The aft seal portion 707 is defined by interacting components, such as a rotor 701, a stator 703, and a spacer wheel 705. The rotor 701 includes an angel wing 772 and the stator 703 includes a rub strip 770. Further, the angel wing 772 includes an outer peripheral surface 776 and a plurality of projections 774 coupled to the outer peripheral surface 776. For ease of illustration, although only one projection 774 is shown in FIG. 10, the angel wing 772 typically includes the plurality of projections 774. Specifically, the plurality of projections 774 is disposed on an up-turn portion 778 and an arm portion 780 of the angel wing 772. In such embodiments, the outer peripheral surface 776 is an outer peripheral surface of the up-turn portion 778 and the arm portion 780. In such embodiments, the up-turn portion 778 is inclined at a pre-defined angle 714 relative to a radial axis 139 of the rotor 701 and the rub strip 770 is disposed facing the angel wing 772. The aft seal portion 707 further includes a cavity 764 defined between the rotor 701, the stator 703, and the spacer wheel 705.
[0047] During operation, the aft seal portion 707 is configured to receive a flow of a fluid 762 leaked from an intermediate seal portion 709 of the inter-stage seal 760. In one embodiment, the fluid 762 is an exhaust gas stream. The cavity 764 receives the fluid 762 from the intermediate seal portion 709. The fluid 762 is directed from the cavity 764 to a rotor blade 766 of the rotor 701 through a clearance 768 defined between the rub strip 770 and the angel wing 772. In such embodiments, the flow of the fluid 762 is regulated using the cavity 764, the plurality of projections 774, and the up-turn portion 778. In one embodiment, regulating the fluid 762 involves recirculating a portion 762a of the fluid 762 within the cavity 764. The plurality of projections 774 is configured to divert another portion 762b of the fluid 762 along the radial direction 138, causing a curtaining effect just upstream of the clearance 768, which results in deflection of the fluid 762 from the clearance 768. The up-turn portion 778 is configured to recirculate yet another portion 762c of the fluid 762. As a result, leakage of the fluid 762 through the clearance 768 is reduced. The aft seal portion 707 may be configured to reduce leakage of the fluid 762 in a range from about 10 percent to about 25 percent compared to a conventional seal.
[0048] FIG. 11 is a flow diagram of a method 800 for controlling flow of a fluid through a seal in accordance with one exemplary embodiment. In one embodiment, the fluid is at least one of a compressed fluid received from a compressor and an exhaust gas stream received from a combustor. The seal is at least one of an intra-stage seal and an inter-stage seal.
[0049] The method 800 includes a step 802 of directing the exhaust gas stream from the combustor to a turbine. The combustor is configured to burn a mixture of a fuel and the compressed fluid to generate the exhaust gas stream. The turbine includes a stator and a rotor. The stator includes a rub strip and the rotor includes an airfoil and a shank coupled to the airfoil. The shank includes a cover plate and an angel wing coupled to the cover plate. The angel wing includes an outer peripheral surface and a plurality of projections coupled to the outer peripheral surface. In some embodiments, at least one projection of the plurality of projections includes an airfoil-shaped projection. In one or more embodiments, the angel wing includes an arm portion protruding from the cover plate and an up-turn portion coupled to the arm portion. In such embodiments, the outer peripheral surface includes an outer peripheral surface of at least one of the arm portion and the up-turn portion.
[0050] The method 800 further includes a step 804 of directing a first portion of the exhaust gas stream along the stator, along the rotor and along a first flow path. In one embodiment, the first portion of the exhaust gas stream is configured to expand through a plurality of stages of the turbine so as to convert energy in the exhaust gas stream to work. Further, the method 800 includes a step 806 of leaking a second portion of the exhaust gas stream from a cavity to the rotor through the seal. The cavity is in fluid communication with the first flow path. In such embodiments, the cavity is defined between the stator and the rotor. The angel wing is disposed facing the rub strip to form the seal there-between. The method 800 further includes a step 808 of directing the compressed fluid from the compressor to the turbine along a second flow path, bypassing the combustor.
[0051] The method 800 further includes a step 810 of regulating the second portion of the exhaust gas stream and the compressed fluid through the seal, using the plurality of projections disposed facing the cavity. In such embodiments, the step 810 includes directing the second portion of the exhaust gas stream and the compressed fluid along a radial direction of the rotor, against the rub strip so as to control a leakage of the fluid through the clearance.
[0052] In accordance with one or more embodiments discussed herein, an exemplary seal is configured to control a fluid flow through a clearance defined between an angel wing and a rub strip. As a result, turbine efficiency is enhanced. The provision of plurality of projections of the angel wing facilitates the seal to operate with tighter clearance without damaging the angel wing or the rub strip during certain transient turbine operating conditions of the turbine.
[0053] While only certain features of embodiments have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended embodiments are intended to cover all such modifications and changes as falling within the spirit of the invention.