Rotor Assembly For Use In Gas Turbine Engines And Method For Assembling The Same

Abstract

A method of assembling a rotor assembly for use with a turbine engine. The method includes providing a rotor shaft and coupling at least one rotor disk to the rotor shaft such that a cooling path is defined between the rotor shaft and the rotor disk. The rotor disk includes a substantially cylindrical body that has upstream and downstream surfaces extending between a radially inner edge and a radially outer edge. A first cooling plate is coupled to the downstream surface of the rotor disk to define a cooling duct between the first cooling plate and the downstream surface. The cooling duct is configured to channel a cooling fluid from the cooling path to the towards the outer edge.

Description

BACKGROUND OF THE INVENTION

[0001] The embodiments described herein relate generally to gas turbine engines, and more particularly, to a rotor assembly used with gas turbine engines.

[0002] At least some known gas turbine engines include a combustor, a compressor coupled downstream from the combustor, a turbine, and a rotor assembly rotatably coupled between the compressor and the turbine. At least some known rotor assemblies include a rotor shaft, at least one rotor disk coupled to the rotor shaft, and a plurality of circumferentially-spaced rotor blades or buckets coupled to each rotor disk. Each rotor blade includes an airfoil that extends radially outward from a rotor blade platform. At least some known rotor blades also include a dovetail that extends radially inward from a shank that extends between the platform and the dovetail. The dovetail is used to mount the rotor blade within a rotor disk. The root segments of at least some known buckets are coupled to a rotor disk with the dovetail that is inserted within a dovetail slot formed in the rotor disk.

[0003] Known rotor blades are hollow and include an internal cooling cavity defined at least partially by the airfoil, platform, shank, and dovetail. The rotating turbine blades or buckets channel high-temperature fluids, such as combustion gases, through the turbine. Because turbine engines typically operate at relatively high temperatures, the airfoil portion of the rotor blades or buckets is generally exposed to higher temperatures than the root portion of the same airfoil. As a result, it is comment for thermal gradients to develop and over time, continued exposure to the high temperatures may cause the blade tips to prematurely fail. Such failures may require replacement of the damaged turbine bucket and require shut down of the turbine to enable repair or replacement of the damaged blade.

[0004] As such, a rotor assembly that provides enhanced cooling of a rotor disk and a turbine bucket could reduce maintenance costs and extend the operational life of the rotor assembly. By extending the operational life of the rotor assembly the operating costs of the gas turbine engine is facilitated to be reduced.

BRIEF DESCRIPTION OF THE INVENTION

[0005] In one aspect, a method of assembling a rotor assembly for use with a turbine engine is provided. The method includes providing a rotor shaft and coupling at least one rotor disk to the rotor shaft such that a cooling path is defined between the rotor shaft and the rotor disk. The rotor disk includes a substantially cylindrical body that has upstream and downstream surfaces extending between a radially inner edge and a radially outer edge. A first cooling plate is coupled to the downstream surface of the rotor disk to define a cooling duct between the first cooling plate and the downstream surface. The cooling duct is configured to channel a cooling fluid from the cooling path to the towards the outer edge.

[0006] In another aspect, a rotor assembly for use with a turbine is provided. The rotor assembly includes a rotor shaft and at least one rotor disk that is coupled to the rotor shaft such that a cooling path is defined between the rotor shaft and the rotor disk. The rotor disk includes a substantially cylindrical body that extends between a radially inner edge and a radially outer edge. The body extends generally axially between an upstream surface and a downstream surface. A cooling assembly is coupled to the rotor disk. The cooling assembly includes a first cooling plate that is coupled to the downstream surface such that a cooling duct is defined between the first cooling plate and the downstream surface. The cooling duct is configured to channel cooling fluid from the cooling path towards the outer edge.

[0007] In a further aspect, a gas turbine engine is provided. The gas turbine engine includes a compressor and a turbine that is coupled in flow communication with the compressor to receive at least some of the air discharged by the compressor. A rotor shaft is rotatably coupled to the turbine. At least one rotor disk is coupled to the rotor shaft such that a cooling path is defined between the rotor shaft and the rotor disk. The rotor disk includes a substantially cylindrical body that extends between a radially inner edge and a radially outer edge. The body extends generally axially between an upstream surface and a downstream surface. A cooling assembly is coupled to the rotor disk. The cooling assembly includes a first cooling plate that is coupled to the downstream surface such that a cooling duct is defined between the first cooling plate and the downstream surface. The cooling duct is configured to channel cooling fluid from the cooling path towards the outer edge.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a schematic view of an exemplary turbine engine.

[0009] FIG. 2 is a partial sectional view of a portion of an exemplary rotor assembly that may be used with the gas turbine engine shown in FIG. 1.

[0010] FIG. 3 is an enlarged partial sectional view of a portion of the rotor assembly shown in FIG. 2.

[0011] FIG. 4 is a partial cross-sectional view of the rotor assembly shown in FIG. 3 and taken along line 4-4.

DETAILED DESCRIPTION OF THE INVENTION

[0012] The exemplary methods and systems described herein overcome disadvantages of known rotor assemblies by providing a rotor disk that facilitates enhanced cooling across a surface of a rotor disk and of a row of turbine buckets. More specifically, the embodiments described herein provide a rotor disk that includes a cooling assembly that channels a cooling fluid from a cooling path defined along a rotor shaft towards the turbine buckets. In the exemplary embodiment, the cooling assembly includes a plurality of vanes that impart a centrifugal force to the cooling fluid to facilitate channeling the cooling fluid radially outwardly from the rotor shaft. The cooling fluid facilitates reducing a temperature of the rotor disk and the turbine buckets, thus increasing the useful life of the rotor assembly.

[0013] As used herein, the term "upstream" refers to a forward or inlet end of a gas turbine engine, and the term "downstream" refers to an aft or nozzle end of the gas turbine engine.

[0014] FIG. 1 is a schematic view of an exemplary turbine engine system 10. In the exemplary embodiment, turbine engine system 10 includes an intake section 12, a compressor section 14 coupled downstream from intake section 12, a combustor section 16 coupled downstream from compressor section 14, a turbine section 18 coupled downstream from combustor section 16, and an exhaust section 20. Turbine section 18 is coupled to compressor section 14 via a rotor shaft 22. In the exemplary embodiment, combustor section 16 includes a plurality of combustors 24. Combustor section 16 is coupled to compressor section 14 such that each combustor 24 is positioned in flow communication with the compressor section 14. A fuel nozzle assembly 26 is coupled to each combustor 24. Turbine section 18 is coupled to compressor section 14 and to a load 28 such as, but not limited to, an electrical generator and/or a mechanical drive application. In the exemplary embodiment, each compressor section 14 and turbine section 18 includes at least one rotor disk assembly 30 that is coupled to rotor shaft 22 to form a rotor assembly 32.

[0015] During operation, intake section 12 channels air towards compressor section 14 wherein the air is compressed to a higher pressure and temperature prior to being discharged towards combustor section 16. The compressed air is mixed with fuel and ignited to generate combustion gases that are channeled towards turbine section 18. More specifically, in combustors 24, fuel, for example, natural gas and/or fuel oil, is injected into the air flow, and the fuel-air mixture is ignited to generate high temperature combustion gases that are channeled towards turbine section 18. Turbine section 18 converts the thermal energy from the gas stream to mechanical rotational energy, as the combustion gases impart rotational energy to turbine section 18 and to rotor assembly 32.

[0016] FIG. 2 is a partial sectional view of a portion of an exemplary rotor assembly 32 that may be used with turbine engine system 10. FIG. 3 is an enlarged partial sectional view of rotor assembly 32. Identical components shown in FIG. 3 are labeled with the same reference numbers used in FIG. 2. In the exemplary embodiment, turbine section 18 includes a plurality of stages 34 that each include a rotating rotor disk assembly 30 and a stationary row of stator vanes 36. In the exemplary embodiment, each rotor disk assembly 30 includes a plurality of turbine buckets 38 coupled to a rotor disk 40. Each rotor disk 40 is coupled to a rotor shaft, such as rotor shaft 22. A turbine casing 42 extends circumferentially about turbine buckets 38 and stator vanes 36, such that stator vanes 36 are supported by casing 42.

[0017] In the exemplary embodiment, each rotor disk 40 is annular and includes a central bore 44 that extends substantially axially therethrough. More specifically, a disk body 46 extends radially outwardly from central bore 44, and central bore 44 is sized to receive rotor shaft 22 therethrough. Disk body 46 extends radially between a radially inner edge 48 and a radially outer edge 50, and axially from an upstream surface 52 to an opposite downstream surface 54. Each upstream surface 52 and downstream surface 54 extends between inner edge 48 and outer edge 50. An axial support arm 56 is coupled between adjacent rotor disks 40 to form rotor assembly 32.

[0018] Each turbine bucket 38 is coupled to outer edge 50 of rotor disk 40 and extends radially outwardly from disk body 46. Turbine buckets 38 are spaced circumferentially about rotor disk 40. Adjacent rotor disks 40 are oriented such that a gap 58 is defined between each row 59 of circumferentially-spaced turbine buckets 38. Gap 58 is sized to receive a row 60 of circumferentially-spaced stator vanes 36 that each extend inwardly from turbine casing 42 towards rotor shaft 22. More specifically, stator vanes 36 are spaced circumferentially about rotor shaft 22 and are oriented to channel combustion gases downstream towards turbine buckets 38. A hot gas path 61 is defined between turbine casing 42 and each rotor disk 40. Each row 59 and 60 of turbine buckets 38 and stator vanes 36 extends at least partially through a portion of hot gas path 61.

[0019] In the exemplary embodiment, each turbine bucket 38 extends radially outwardly from rotor disk 40 and includes an airfoil 62, a platform 64, a shank 66, and a dovetail 68. Platform 64 extends between airfoil 62 and shank 66 such that each airfoil 62 extends radially outwardly from platform 64 towards turbine casing 42. Shank 66 extends radially inwardly from platform 64 to dovetail 68. Dovetail 68 extends radially inwardly from shank 66 and enables turbine buckets 38 to be securely coupled to rotor disk 40. A shank sidewall 70 extends between a forward cover plate 72 and an aft cover plate 74. Shank sidewall 70 is recessed with respect to forward cover plate 72 and aft cover plate 74, such that when turbine buckets 38 are coupled to rotor disk 40, a shank cavity 76 is defined between circumferentially-adjacent shank sidewalls 70. In one embodiment, an annular passage 78 is defined through shank 66 and dovetail 68 and extends from rotor disk 40 to platform 64. Passage 78 enables a flow of cooling fluid to be channeled from rotor disk outer edge 50 towards platform 64. In the exemplary embodiment, a forward angel wing 80 extends outwardly from forward cover plate 72 to facilitate sealing a forward buffer cavity 82 defined between rotor disk upstream surface 52 and stator vane 36. An aft angel wing 84 extends outwardly from aft cover plate 74 to facilitate sealing an aft buffer cavity 86 defined between rotor disk downstream surface 54 and stator vane 36. In the exemplary embodiment, a forward lower angel wing 88 extends outwardly from forward cover plate 72 to facilitate sealing between turbine bucket 38 and rotor disk 40. More specifically, forward lower angel wing 88 is positioned between dovetail 68 and forward angel wing 80.

[0020] Rotor disk inner edge 48 is spaced at a distance radially outwardly from rotor shaft 22 such that a gap 90 is defined between an outer surface 92 of rotor shaft 22 and inner edge 48. Rotor disks 40 are coupled together such that a cooling flow path 94 is defined between rotor shaft 22 and each rotor disk 40. Cooling flow path 94 is configured to facilitate channeling a flow of cooling fluid 96 from compressor section 14 through turbine section 18. A cooling assembly 100 is coupled to at least one rotor disk 40 for use in channeling cooling fluid from cooling flow path 94 towards turbine buckets 38. More specifically, in the exemplary embodiment, cooling assembly 100 channels cooling fluid 96 from rotor disk inner edge 48 towards outer edge 50.

[0021] In the exemplary embodiment, cooling assembly 100 includes a first cooling plate 102 and a second cooling plate 104. First cooling plate 102 is coupled to rotor disk downstream surface 54, and second cooling plate is coupled to rotor disk upstream surface 52. First cooling plate 102 includes a first cooling disk 106 extending between an inner portion 108 and a radially outer portion 110. First cooling disk 106 includes a bore 111 defined by inner portion 108. Bore 111 is sized to receive rotor shaft 22. In the exemplary embodiment, first cooling disk 106 extends from inner edge 48 to outer edge 50 across downstream surface 54 and is spaced a distance d.sub.1 from rotor disk 40 such that a cooling duct 112 is defined between an inner surface 114 of first cooling disk 106 and rotor disk downstream surface 54. An inlet opening 116 is defined between rotor disk downstream surface 54 and inner portion 108, and an outlet opening 118 is defined between downstream surface 54 and outer portion 110. In the exemplary embodiment, cooling duct 112 extends between inlet openings 116 and 118 for use in channeling cooling fluid 96 from inlet opening 116 through outlet opening 118. Inlet opening 116 enables cooling fluid 96 to be channeled into cooling duct 112 from cooling flow path 94. First cooling disk 106 is oriented substantially parallel with rotor disk downstream surface 54 such that cooling duct 112 has a substantially uniform width w from inner portion 108 to outer portion 110. In the exemplary embodiment, inner portion 108 substantially circumscribes rotor shaft outer surface 92 and is spaced a distance d.sub.2 radially from outer surface 92 such that at least a portion of cooling flow path 94 is defined between first cooling plate 102 and rotor shaft 22. First cooling plate 102 channels at least a portion of cooling fluid 96 from cooling flow path 94 through cooling duct 112 towards rotor disk outer edge 50 to facilitate cooling of rotor disk 40 and each turbine buckets 38. In one embodiment, a flange 120 extends radially inwardly from inner portion 108 towards rotor shaft 22.

[0022] In the exemplary embodiment, a plurality of vanes 122 are coupled between rotor disk 40 and first cooling disk 106. Vanes 122 are circumferentially-spaced and each extends between disk inner portion 108 and outer portion 110. Vanes 122 impart a centrifugal force upon cooling fluid 96 entering inlet opening 116 of cooling duct 112. Cooling duct 112 channels cooling fluid 96 from inlet opening 116 to outlet opening 118. Inlet opening 116 is defined between a pair of circumferentially-adjacent vanes 122. More specifically, in the exemplary embodiment, inlet openings 116 are adjacent to inner portion 108. Outlet openings 118 are defined between adjacent vanes 122 such that each outlet opening 118 is adjacent to outer portion 110.

[0023] Cooling plate 104 is coupled to rotor disk 40 and is spaced at a distance d.sub.3 from upstream surface 52 such that a return air duct 124 is defined between cooling plate 104 and upstream surface 52. In the exemplary embodiment, cooling plate 104 includes a second cooling disk 126. Second cooling disk 126 includes an inner portion 128 and a radially outer portion 130. A bore 131 is defined by inner portion 128 that is sized to receive rotor shaft 22. Outer portion 130 is positioned adjacent to rotor disk outer edge 50. Inner portion 128 circumscribes rotor shaft 22. Rotor disk inner edge 48 is positioned closer to outer surface 92 than inner portion 128. Return air duct 124 extends between a return air inlet opening 132 and a return air outlet opening 134. Return air inlet opening 132 is defined between outer portion 130 and upstream surface 52. Return air outlet opening 134 is defined between inner portion 128 and upstream surface 52. Return air duct 124 enables cooling fluid 96 to be channeled from rotor disk outer edge 50 to cooling flow path 94.

[0024] In the exemplary embodiment, cooling assembly 100 includes an upper cooling flange 136 that extends between cooling plates 102 and 104 such that cooling duct 112 is coupled in flow communication with return air duct 124. A channel 138 is defined between cooling plate outer portion 110 and cooling plate outer portion 130. Channel 138 forms a portion of a cooling circuit 140 for use in channeling cooling fluid 96 from cooling duct 112 to return air duct 124.

[0025] During operation, compressor section 14 (shown in FIG. 1) compresses air and discharges compressed air into combustor section 16 (shown in FIG. 1) and towards turbine section 18. The majority of air discharged from compressor section 14 is channeled towards combustor section 16, and a smaller portion of air discharged from compressor section 14 is channeled downstream towards turbine section 18 for use in cooling rotor assembly 32. More specifically, a first flow leg 142 of pressurized compressed air is channeled to combustors 24 (shown in FIG. 1) wherein the air is mixed with fuel and ignited to generate high temperature combustion gases 142. The combustion gases 142 are channeled towards hot gas path 61, wherein the gases 142 impinge upon turbine buckets 38 and stator vanes 36 to facilitate imparting a rotational force on rotor assembly 32. Compressed air also enters a second flow leg 144 for use as cooling fluid 96. Air discharged from flow leg 144 is channeled into cooling flow path 94 between rotor shaft 22 and rotor disks 40. As rotor assembly 32 rotates, cooling assembly 100 directs at least a portion of air discharged from flow leg 144 outwardly from cooling flow path 94 through each cooling duct 112 towards rotor disk outer edge 50.

[0026] FIG. 4 is a partial cross-sectional view of rotor assembly 32 along sectional line 4-4. Identical components shown in FIG. 4 are labeled with the same reference numbers used in FIG. 2 and FIG. 3. In the exemplary embodiment, vanes 122 extend between inner portion 108 and outer portion 110 of first cooling plate 102. An inlet edge 150 of each vane 122 is spaced circumferentially about bore 111 defined by inner portion 108. Bore 111 is sized to receive rotor shaft 22 therein such that cooling flow path 94 is defined circumferentially between rotor shaft 22 and first cooling plate 102. Each vane 122 includes a pressure side 152 and an opposing suction side 154. Each pressure side 152 and suction side 154 extends between inlet edge 150 and an outlet edge 156. Each pair of circumferentially-spaced adjacent vanes 122 are spaced such that a cooling channel 158 is defined between inlet opening 116 and outlet opening 118. Each cooling channel 158 is further defined between first cooling disk 106 and downstream surface 54 (shown in FIG. 2). Each inlet opening 116 extends between a pressure side 152 and an adjacent suction side 154 of vane 122 at inlet edge 150. Each outlet opening 118 extends between pressure side 152 and an adjacent suction side 154 at outlet edge 156. Inlet opening 116 has a first width 160 that is smaller than a second width 162 of outlet opening 118. Each vane 122 is formed with an arcuate shape and is oriented such that cooling channel 158 is defined with a spiral shape that diverges outwardly from inner portion 108 towards outer portion 110. In one embodiment, a plurality of turbulators 164, such as fins and/or ribs, are coupled to downstream surface 54 and/or to first cooling disk 106 within cooling channel 158, to facilitate a heat transfer from rotor disk 40 to cooling fluid 96.

[0027] During operation, cooling fluid 96 is channeled into cooling channels 158 through each inlet opening 116. As cooling fluid 96 enters inlet openings 116, a rotation of rotor assembly 32 causes vanes 122 impart a centrifugal force to cooling fluid 96, such that a pressure of cooling fluid 96 within each cooling channel 158 is increased. As the centrifugal force acts upon cooling fluid 96, a differential pressure within cooling fluid 96 is created between inlet opening 116 and outlet opening 118. Cooling channels 158 discharge cooling fluid 96 outwardly from inlet opening 116 to outlet opening 118. Cooling fluid 96 facilitates convectively cooling rotor disk 40 as the fluid 96 is channeled across downstream surface 54. Cooling fluid 96 impinges against support arm 56 to facilitate cooling of rotor disk outer edge 50 and support arm 56. In one embodiment, at least a portion of cooling fluid 96 is channeled into each bucket passage 78 to facilitate cooling shanks 66 and platforms 64.

[0028] The above-described rotor assembly facilitates reducing an operating temperature of a gas turbine. More specifically, by providing a rotor assembly having a cooling assembly coupled to an outer surface of a rotor disk, a cooling fluid is channeled radially outwardly from a rotor shaft towards a turbine bucket to facilitate cooling the rotor assembly. In addition, by assembling a cooling assembly that includes a plurality of cooling channels, a centrifugal force generated by a rotation of the rotor assembly facilitates channeling cooling fluid through the cooling channels to reduce an operating temperature of the rotor assembly. Moreover, by providing a rotor assembly having a cooling assembly, the cooling of a rotor disk is increased over known rotor assemblies that do not channel cooling fluid from the rotor shaft towards the turbine buckets. As such, the cost of maintaining the gas turbine engine system is facilitated to be reduced.

[0029] Exemplary embodiments of a rotor assembly for use in a gas turbine engine and method for assembling the same are described above in detail. The methods and apparatus are not limited to the specific embodiments described herein, but rather, components of systems and/or steps of the method may be utilized independently and separately from other components and/or steps described herein. For example, the methods and apparatus may also be used in combination with other combustion systems and methods, and are not limited to practice with only the gas turbine engine assembly as described herein. Rather, the exemplary embodiment can be implemented and utilized in connection with many other combustion system applications.

[0030] Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. Moreover, references to "one embodiment" in the above description are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

[0031] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. A method of assembling a rotor assembly for use with a turbine engine, said method comprising: providing a rotor shaft; coupling at least one rotor disk to the rotor shaft such that a cooling path is defined between the rotor shaft and the at least one rotor disk, the at least one rotor disk including a substantially cylindrical body having upstream and downstream surfaces extending between a radially inner edge and a radially outer edge; and coupling a first cooling plate to the downstream surface of the at least one rotor disk to define a cooling duct between the first cooling plate and the downstream surface, the cooling duct configured to channel a cooling fluid from the cooling path to the towards the outer edge.

2. A method in accordance with claim 1, further comprising coupling a plurality of vanes between the downstream surface and the first cooling plate, each vane extends outwardly from the inner edge towards the outer edge, adjacent vanes are spaced a circumferential distance apart such that a cooling channel is defined between each pair of circumferentially-spaced vanes.

3. A method in accordance with claim 1, wherein coupling a plurality of vanes further comprises: providing each vane having an arcuate outer surface shaped to channel fluid through each cooling channel; and coupling each vane between the downstream surface and the first cooling plate.

4. A method in accordance with claim 1, further comprises coupling an inner flange to the first cooling plate, the inner flange extending inwardly from the first cooling plate towards the rotor shaft.

5. A method in accordance with claim 1, further comprising coupling a second cooling plate to the upstream surface of the at least one rotor disk such that a return air duct is defined between the second cooling plate and the upstream surface.

6. A method in accordance with claim 5, further comprising coupling a first rotor disk to an adjacent second rotor disk such that the first rotor disk cooling duct is in flow communication with the second rotor disk return air duct.

7. A rotor assembly for use with a turbine, said rotor assembly comprising: a rotor shaft; at least one rotor disk coupled to said rotor shaft such that a cooling path is defined between said rotor shaft and said at least one rotor disk, said at least one rotor disk comprises a substantially cylindrical body extending between a radially inner edge and a radially outer edge, said body extending generally axially between an upstream surface and a downstream surface; and a cooling assembly coupled to said at least one rotor disk, said cooling assembly comprising a first cooling plate coupled to said downstream surface such that a cooling duct is defined between said first cooling plate and said downstream surface, said cooling duct configured to channel cooling fluid from the cooling path towards said outer edge.

8. A rotor assembly in accordance with claim 7, wherein said cooling assembly further comprises a plurality of vanes coupled between said downstream surface and said first cooling plate, each said vane extends outwardly from said inner edge towards said outer edge, adjacent said vanes are spaced a circumferential distance apart such that a cooling channel is defined between each said pair of circumferentially-adjacent vanes.

9. A rotor assembly in accordance with claim 8, wherein each said vane comprises an arcuate outer surface shaped to channel cooling fluid through each said cooling channel.

10. A rotor assembly in accordance with claim 8, wherein each said pair of circumferentially-spaced vanes are spaced such that said cooling channel is defined with an inlet opening that is smaller than an outlet opening.

11. A rotor assembly in accordance with claim 8, wherein said first cooling plate comprises an inner flange that extends inwardly from said first cooling plate to define an inlet opening that extends into a cooling fluid path defined between said rotor disk inner edge and said shaft.

12. A rotor assembly in accordance with claim 8, wherein said cooling assembly further comprises a second cooling plate coupled to said upstream surface such that a return air duct is defined between said second cooling plate and said upstream surface.

13. A rotor assembly in accordance with claim 12, wherein said at least one rotor disk comprises at least a first rotor disk coupled to a second rotor disk, said first cooling plate is coupled to adjacent second cooling plate such that said cooling duct is coupled in flow communication with said return air duct.

14. A rotor assembly in accordance with claim 7, wherein said cooling assembly further comprises at least one turbulator coupled to said first cooling plate.

15. A turbine engine comprising: a compressor; a turbine coupled in flow communication with said compressor to receive at least some of the air discharged by said compressor; a rotor shaft rotatably coupled to said turbine; at least one rotor disk coupled to said rotor shaft such that a cooling path is defined between said rotor shaft and said at least one rotor disk, said at least one rotor disk comprises a substantially cylindrical body extending between a radially inner edge and a radially outer edge, said body extending generally axially between an upstream surface and a downstream surface; and a cooling assembly coupled to said at least one rotor disk, said cooling assembly comprising a first cooling plate coupled to said downstream surface such that a cooling duct is defined between said first cooling plate and said downstream surface, said cooling duct configured to channel cooling fluid from the cooling path towards said outer edge.

16. A turbine engine in accordance with claim 15, wherein said cooling assembly further comprises a plurality of vanes coupled between said downstream surface and said first cooling plate, each said vane extends outwardly from said inner edge towards said outer edge, adjacent said vanes are spaced a circumferential distance apart such that a cooling channel is defined between each said pair of circumferentially-adjacent vanes.

17. A turbine engine in accordance with claim 16, wherein each said vane comprises an arcuate outer surface shaped to channel cooling fluid through each said cooling channel.

18. A turbine engine in accordance with claim 15, wherein said first cooling plate comprises an inner flange that extends inwardly from said first cooling plate to define an inlet opening that extends into a cooling fluid path defined between said rotor disk inner edge and said shaft.

19. A turbine engine in accordance with claim 15, wherein said cooling assembly further comprises a second cooling plate coupled to said upstream surface such that a return air duct is defined between said second cooling plate and said upstream surface.

20. A turbine engine in accordance with claim 19, wherein said at least one rotor disk comprises a first rotor disk coupled to a second rotor disk, said first cooling plate is coupled to adjacent second cooling plate such that said cooling duct is coupled in flow communication with said return air duct.