Rotor shaft cooling

A gas turbine casing with an internal heat exchange system. The gas turbine extends between an inlet section and an exhaust section and defines a downstream direction from the inlet section to the exhaust section. The casing includes a forward end, an aft end downstream of the forward end, a first exterior surface facing radially outward, a second exterior surface facing radially inward, and an internal body at least partially defined between the first exterior surface and the second exterior surface. The heat exchange system includes an inlet and an outlet formed in an exterior surface of the casing proximate the aft end, a supply bore extending upstream from the inlet through the interior body of the casing, and a return bore extending downstream to the outlet through the interior body of the casing.

FIELD

The present subject matter relates generally to a gas turbine engine. More particularly, the present disclosure relates to a system and method for cooling a rotor shaft of a gas turbine engine.

BACKGROUND

A gas turbine engine generally includes a compressor section, a combustion section, a turbine section, and an exhaust section. The compressor section progressively increases the pressure of a working fluid entering the gas turbine engine and supplies this compressed working fluid to the combustion section. The compressed working fluid and a fuel (e.g., natural gas) mix within the combustion section and burn in a combustion chamber to generate high pressure and high temperature combustion gases. The combustion gases flow from the combustion section into the turbine section where they expand to produce work. For example, expansion of the combustion gases in the turbine section may rotate a rotor shaft connected, e.g., to a generator to produce electricity. The combustion gases then exit the gas turbine via the exhaust section.

During operation of the gas turbine, various components in the system are subjected to high temperatures. For example, high temperature combustion gases are produced in the combustion section such that various parts of the gas turbine downstream of the combustion section are subjected to high temperatures. Such parts of the gas turbine include the portion(s) of the rotor shaft that are adjacent to and downstream of the combustion section.

BRIEF DESCRIPTION

Aspects and advantages are set forth below in the following description, or may be obvious from the description, or may be learned through practice. Additional aspects and advantages will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice.

In a first exemplary embodiment, a casing for a gas turbine is provided. The gas turbine extends between an inlet section and an exhaust section and defines a downstream direction from the inlet section to the exhaust section. The casing includes a forward end, an aft end downstream of the forward end, a first exterior surface facing radially outward, a second exterior surface opposing the first exterior surface, the second exterior surface facing radially inward, an internal body at least partially defined between the first exterior surface and the second exterior surface, and a heat exchange system comprising an inlet formed in one of the first exterior surface and the second exterior surface proximate the aft end of the casing, an outlet formed in one of the first exterior surface and the second exterior surface proximate the aft end of the inner casing, a supply bore extending upstream from the inlet through the interior body of the casing, and a return bore extending downstream to the outlet through the interior body of the casing.

In a second exemplary embodiment, a gas turbine extending between an inlet section and an exhaust section and defining a downstream direction from the inlet section to the exhaust section is provided. The gas turbine also includes a compressor, a turbine section, the exhaust section downstream of the turbine section, a plurality of combustors disposed downstream from the compressor and upstream from the turbine, a rotor shaft extending between the turbine section and the compressor, a casing between the rotor shaft and the plurality of combustors, a high pressure packing seal between the rotor shaft and the inner casing, a heat exchange system defined in the casing, the heat exchange system comprising an inlet formed in the casing proximate an aft end of the casing, an outlet formed in the casing proximate the aft end of the casing, a supply conduit extending through the casing upstream from the inlet, and a return conduit extending through the casing downstream to the outlet, and a cooling fluid source in fluid communication with at least one of the inlet and the outlet, wherein the rotor shaft is in thermal communication with the heat exchange system of the casing.

In a third exemplary embodiment, a method of cooling a rotor shaft of a gas turbine is provided. The gas turbine also includes a compressor, a turbine section, a plurality of combustors disposed downstream from the compressor and upstream from the turbine, the rotor shaft extending between the turbine and the compressor, a casing between the rotor shaft and the plurality of combustors and a high pressure packing seal disposed in a high pressure packing seal cavity between the rotor shaft and the casing. The method includes directing a supply stream of a cooling fluid within the casing in an upstream direction from an inlet proximate to an aft end of the casing and directing a return stream of the cooling fluid within the casing in a downstream direction to an outlet proximate the aft end of the casing, whereby heat is transferred from the rotor shaft to the cooling fluid.

DETAILED DESCRIPTION

As used herein, the terms “first,” “second,” and “third” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. The terms “upstream” and “downstream” refer to the relative direction with respect to fluid flow in a fluid pathway. For example, “upstream” refers to the direction from which the fluid flows, and “downstream” refers to the direction to which the fluid flows. The term “radially” refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component, the term “axially” refers to the relative direction that is substantially parallel and/or coaxially aligned to an axial centerline of a particular component, and the term “circumferentially” refers to the relative direction that extends around the axial centerline of a particular component.

Each example is provided by way of explanation, not limitation. In fact, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Although exemplary embodiments of the present disclosure will be described generally in the context of a land-based power generating gas turbine combustor for purposes of illustration, one of ordinary skill in the art will readily appreciate that embodiments of the present disclosure may be applied to any style or type of turbomachine and are not limited to land-based power generating gas turbines unless specifically recited.

Referring now to the drawings,FIG. 1illustrates a schematic diagram of an exemplary gas turbine10. The gas turbine10generally includes an inlet section12, a compressor14disposed downstream of the inlet section12, at least one combustor16disposed downstream of the compressor14, a turbine18disposed downstream of the combustor16and an exhaust section20disposed downstream of the turbine18. Additionally, the gas turbine10may include one or more shafts22that couple the compressor14to the turbine18.

During operation, air24flows through the inlet section12and into the compressor14where the air24is progressively compressed, thus providing compressed air26to the combustor16. At least a portion of the compressed air26is mixed with a fuel28within the combustor16and burned to produce combustion gases30. Another portion of the compressed air26may be used as a cooling medium for cooling the various components of the turbine section18. The combustion gases30flow from the combustor16into the turbine section18, wherein energy (kinetic and/or thermal) is transferred from the combustion gases30to rotor blades (not shown), thus causing shaft22to rotate. The mechanical rotational energy may then be used for various purposes such as to power the compressor14and/or to generate electricity. The combustion gases30exiting the turbine18may then be exhausted from the gas turbine10via the exhaust section20. In some embodiments, e.g., wherein the gas turbine10forms part of a combined cycle power generation plant, the exhaust section20may include or be in fluid communication with a heat recovery steam generator (HRSG)400. Exhaust gases may be directed through the HRSG400. In such embodiments, the exhaust gases supplied to the HRSG400may, in turn, be used as a heat source for generating high-pressure, high-temperature steam. The steam may then be at least partially recirculated through turbine10for cooling various components thereof and/or at least partially passed through a steam turbine (not shown) in order to generate power.

As may be seen inFIG. 2, gas turbine10includes multiple casings which may enclose and/or separate various components of the gas turbine10. Such casings may include an inner casing100which generally surrounds a portion of rotor shaft22. In particular, the illustration inFIG. 2includes a portion of rotor shaft22proximate to the downstream end of compressor14and the upstream end of turbine section18. As may be seen inFIG. 2, the illustrated portion of rotor shaft22abuts a high-pressure packing seal (HPPS)34between the shaft22and inner casing100. In some embodiments, the HPPS34may be disposed in an HPPS cavity of the inner casing100, as illustrated inFIG. 2.

As shown inFIG. 2, a casing100having a heat exchange system200therein may, in some exemplary embodiments, be inner casing100. Inner casing100may extend between a forward end102and an aft end104downstream of the forward end102. Inner casing100may also include a first exterior surface106facing radially outward and a second exterior surface108opposing the first exterior surface, i.e., the second exterior surface108may face radially inward, with an internal body110of casing100at least partially defined between the first exterior surface106and the second exterior surface108.

Heat exchange system200may include an inlet202formed in one of the first exterior surface106and the second exterior surface108proximate the aft end104of the casing100, with a supply bore204extending upstream (with respect to the overall flow direction of working fluid/combustion gases through the gas turbine) from the inlet202through the interior body110of the casing100. In other words, because inlet202is positioned in or near aft end104and supply bore204extends from the inlet202through internal body110of casing100, the supply bore204extends upstream from the inlet202. Thus, cooling fluid310flowing from inlet202into supply bore204will flow upstream, that is, against the prevailing flow direction of compressed air26and/or combustion gases30through the gas turbine10.

Heat exchange system200may further include an outlet210formed in one of the first exterior surface106and the second exterior surface108proximate the aft end104of the casing100, with a return bore208extending downstream (with respect to the overall flow direction of working fluid/combustion gases through the gas turbine) to the outlet210through the interior body110of the casing100.

As illustratedFIG. 2, in some exemplary embodiments, the internal body110of inner casing100may be partially hollow while supply bore204and return bore208extend through a solid portion of the internal body110. In other exemplary embodiments, the internal body110of inner casing100may be entirely solid.

In the exemplary embodiment illustrated inFIG. 2, the supply bore204and the return bore208are shown with some separation between them in the radial (i.e., vertical on the page as illustrated inFIG. 2) direction, with supply bore204radially outward (above, as illustrated inFIG. 2) return bore208. In some exemplary embodiments, such as the embodiment illustrated inFIG. 3, the supply bore204and the return bore208may have some radial separation with the return bore208radially outward of the supply bore204. In other embodiments, the supply bore204and the return bore208may be radially aligned.

In some embodiments, heat exchange system200may further include a plenum206defined within the internal body110of the casing100proximate to the forward end102of the casing100. In some embodiments wherein the heat exchange system200includes a plenum206, the supply bore204may extend from the inlet202to the plenum206. In some embodiments wherein the heat exchange system200includes a plenum206, the return bore208may extend from the plenum206to the outlet210.

Heat exchange system200, and in particular inlet202and/or outlet210thereof, may be in fluid communication with a cooling fluid source300. Accordingly, a cooling fluid310may be provided to and/or circulated through casing100and heat exchange system200. As may be seen inFIG. 2, casing100is disposed proximate to rotor shaft22, such that the rotor shaft22is in thermal communication with the heat exchange system200of the casing100. Accordingly, heat may be transferred from the rotor shaft22to the cooling fluid310and the heat exchange system200may help cool the rotor shaft22.

In various embodiments, several different cooling fluids310and/or cooling fluid sources300are possible. For example, in various embodiments, the cooling fluid310may be air, steam, liquid water, or combinations thereof, among other possibilities.

The compressor section14includes a plurality of stages that progressively increase the pressure of the working fluid26. As the pressure of the working fluid26increases, the temperature of the working fluid26increases as well. Nonetheless, compressed working fluid26from the compressor14is cooler than the high temperature combustion gases30. A such, compressed working fluid26may still be useful for reducing the temperature of gas turbine components which are subjected to high temperatures. In some embodiments, compressed working fluid26may be drawn from an intermediate stage of the compressor14for use as cooling fluid310, e.g., as illustrated inFIG. 2, the cooling fluid source300may be a cooling air system300which provides cooling air from an intermediate stage of the compressor14to at least one nozzle of the turbine section18. In such embodiments, the cooling air system300may be in fluid communication with the inlet202of the heat exchange system200to supply cooling fluid310to heat exchange system200. Further in some such embodiments, the cooling air system300may be in fluid communication with the outlet210of the heat exchange system200to return cooling fluid310to cooling air system300for cooling the at least one nozzle of the turbine section18. In such embodiments, the compressed working fluid26from the intermediate stage may have a lower pressure and lower temperature than compressed working fluid26at an outlet of the compressor14.

Further illustrated inFIG. 2, in some embodiments, the cooling air system300may include a first conduit302extending between the intermediate stage of the compressor14and the turbine section18, a second conduit304extending between the first conduit302and the inlet202of the heat exchange system200and a third conduit306extending between the outlet210of the heat exchange system200and the first conduit302.

As illustratedFIG. 3, in some exemplary embodiments, the cooling fluid source300may be the HRSG400. In such embodiments, the cooling fluid310may be at least a portion of the steam generated by the HRSG400.

As illustratedFIG. 4, in some exemplary embodiments, the cooling fluid source300may be an external blower500. In such embodiments, the cooling fluid310may be air.

Some exemplary embodiments may include a method of cooling a rotor shaft22of a gas turbine10. An exemplary gas turbine10with which such methods may be employed may include a compressor14, a turbine section18, a plurality of combustors16disposed downstream from the compressor14and upstream from the turbine18, a rotor shaft22extending between the turbine18and the compressor14, a casing100between the rotor shaft22and the plurality of combustors16and a high pressure packing seal34disposed in a high pressure packing seal cavity between the rotor shaft22and the casing100. One or more exemplary embodiments of such method may include directing a supply stream of a cooling fluid310within the casing100in an upstream direction from an inlet202proximate to an aft end104of the casing100and directing a return stream of the cooling fluid310within the casing100in a downstream direction to an outlet210proximate the aft end104of the casing100, whereby heat is transferred from the rotor shaft22to the cooling fluid310.

In some exemplary embodiments, the cooling fluid310may be a first cooling fluid, and the method also include a step of injecting a stream of a second cooling fluid, e.g., steam, into the high pressure packing seal cavity. In some exemplary embodiments, the step of directing a supply stream may also include directing the cooling fluid310to an internal plenum206defined within the casing100proximate a forward end102of the casing100. In some exemplary embodiments, the step of directing a return stream may also include directing the cooling fluid310from the internal plenum206defined within the casing100proximate the forward end102of the casing100. In some exemplary embodiments, such method may include directing a stream of cooling fluid310from an intermediate stage of the compressor14to the inlet202so as to form the supply stream of cooling fluid310and/or directing a stream of cooling fluid310from the outlet210to at least one nozzle of the turbine section18.