Hot gas path component with impingement and pedestal cooling

The present application provides a hot gas path component for use in a hot gas path of a gas turbine engine. The hot gas path component may include an internal wall, an external wall facing the hot gas path, an impingement wall, a number of internal wall pedestals positioned between the internal wall and the impingement wall, and a number of external wall pedestals positioned between the external wall and the impingement wall.

TECHNICAL FIELD

The present application and the resultant patent relate generally to gas turbine engines and more particularly relate to a hot gas path component such as a turbine bucket platform with combined impingement cooling and pedestal cooling for improved efficiency and component lifetime.

BACKGROUND OF THE INVENTION

Known gas turbine engines generally include rows of circumferentially spaced nozzles and buckets. A turbine bucket includes an airfoil having a pressure side and a suction side and extending radially upward from a platform. A hollow shank portion may extend radially downward from the platform and may include a dovetail and the like so as to secure the turbine bucket to a turbine wheel. The platform generally defines an inner boundary for the hot combustion gases flowing through the hot gas path. As such, the platform may be an area of high stress concentrations due to the hot combustion gases and the mechanical loading thereon. In order to relieve a portion of the thermally induced stresses, a turbine bucket may include some type of platform cooling scheme or other arrangements so as to reduce the temperature differential between the top and the bottom of the platform.

Various types of platform cooling schemes are known. For example, impingement cooling is well-known in, for example, stage one nozzle cooling schemes. Due to the fact that most of the pressure drop across an impingement cooling circuit is taken across an impingement plate, however, either the impingement holes generally must be relatively small or the cooling circuit may require more flow to manage the pressure than may be required by the overall cooling requirements. Other types of platform cooling examples include the use of pedestal cooling. Pedestal cooling is known in, for example, stage one bucket trailing edges and the like. Other types of hot gas path components also may require similar types of cooling.

There is therefore a desire for an improved hot gas path component such as a turbine bucket and the like for use with a gas turbine engine. Preferably such a turbine bucket may provide cooling to the platform and other components thereof without excessive cooling medium losses for efficient operation and an extended component lifetime.

SUMMARY OF THE INVENTION

The present application and the resultant patent thus provide a hot gas path component for use in a hot gas path of a gas turbine engine. The hot gas path component may include an internal wall, an external wall facing the hot gas path, an impingement wall, a number of internal wall pedestals positioned between the internal wall and the impingement wall, and a number of external wall pedestals positioned between the external wall and the impingement wall for combined pedestal cooling and impingement cooling.

The present application and the resultant patent further provide a method of cooling a hot gas path component in a hot gas path of a gas turbine engine. The method may include the steps of flowing a cooling medium through an internal wall pedestal cooling zone having a number of internal wall pedestals, flowing the cooling medium though an impingement cooling zone having a number of impingement holes, and flowing the cooling medium through an external wall pedestal cooling zone having a number of external wall pedestals for combined pedestal cooling and impingement cooling.

The present application and the resultant patent further provide a bucket platform for use in a hot gas path of a gas turbine engine. The bucket platform may include an internal wall, an external wall facing the hot gas path, an impingement wall with a number of impingement holes therein, a number of internal wall pedestals positioned between the internal wall and the impingement wall, and a number of external wall pedestals positioned between the external wall and the impingement wall for combined pedestal cooling and impingement cooling.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to like elements throughout the several views,FIG. 1shows a schematic view of gas turbine engine10as may be used herein. The gas turbine engine10may include a compressor15. The compressor15compresses an incoming flow of air20. The compressor15delivers the compressed flow of air20to a combustor25. The combustor25mixes the compressed flow of air20with a pressurized flow of fuel30and ignites the mixture to create a flow of combustion gases35. Although only a single combustor25is shown, the gas turbine engine10may include any number of combustors25. The flow of combustion gases35is in turn delivered to a turbine40. The flow of combustion gases35drives the turbine40so as to produce mechanical work. The mechanical work produced in the turbine40drives the compressor15via a shaft45and an external load50such as an electrical generator and the like.

The gas turbine engine10may use natural gas, liquid fuel, various types of syngas, and/or other types of fuels and blends thereof. The gas turbine engine10may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y., including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine10may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together. Aviation application also may be used herein.

FIG. 2shows an example of a turbine bucket55that may be used with the turbine40. Generally described, the turbine bucket55includes an airfoil60, a shank portion65, and a platform70disposed between the airfoil60and the shank portion65. The airfoil60generally extends radially upward from the platform70and includes a leading edge72and a trailing edge74. The airfoil60also may include a concave wall defining a pressure side76and a convex wall defining a suction side78. The platform70may be substantially horizontal and planar. Likewise, the platform70may include a top surface80, a pressure face82, a suction face84, a forward face86, and an aft face88. The top surface80of the platform70may be exposed to the flow of the hot combustion gases35. The shank portion65may extend radially downward from the platform70such that the platform70generally defines an interface between the airfoil60and the shank portion65. The shank portion65may include a shank cavity90therein. The shank portion65also may include one or more angle wings92and a root structure94such as a dovetail and the like. The root structure94may be configured to secure the turbine bucket55to the shaft45.

The turbine bucket55may include one or more cooling circuits96extending therethrough for flowing a cooling medium98such as air from the compressor15or from another source. The cooling circuits96and the cooling medium98may circulate at least through portions of the airfoil60, the shank portion65, and the platform70in any order, direction, or route. Many different types of cooling circuits and cooling mediums may be used herein. The turbine bucket55described herein is for the purpose of example only, many other components and other configurations also may be used herein.

FIG. 3andFIG. 4show a portion of a hot gas path component100as may be described herein. In this example, the hot gas path component100may be a turbine bucket110. More specifically, the hot gas path component100may be a bucket platform120. The turbine bucket110and the platform120may be similar to that described above. The platform120may be cooled with a cooling medium130. Any type of cooling medium130may be used herein from any source. Other types of hot gas path components may be used herein. For example, the hot gas path component100may include a nozzle, a shroud, a liner, and/or a transition piece. The hot gas path component100may have any size, shape, or configuration. The hot gas path component100may be made out of any suitable type of heat resistant materials.

The platform120may include an internal wall140. The internal wall140may be on the cool side of the platform120. The platform120also may include an external wall150. The external wall150may be on the top surface or the hot side of the platform120in the hot gas path formed by the flow of combustion gases35. The platform120may further include a middle impingement wall160. The walls140,150,160may have any size, shape, or configuration.

The impingement wall160may include an array of impingement holes170therethrough. The impingement holes170may have any size, shape, or configuration. Any number of the impingement holes170may be used. The internal wall140may be connected to the impingement wall160by a number of internal wall pedestals180. Likewise, the external wall150may be connected to the impingement wall160via a number of external wall pedestals190. The pedestals180,190may have any size, shape, or configuration. Any number of pedestals180,190may be used. Other components and other configurations may be used herein.

In use, the cooling medium130may flow through the interior wall pedestals180between the internal wall140and the impingement wall160in an internal wall pedestal cooling zone200. The internal wall pedestals180may promote an even distribution of the cooling medium130therein so as to enhance the heat transfer rate, conduct heat from the impingement wall160to the internal wall149, and distribute stress from the impingement wall160to the internal wall140. The cooling medium130then may flow through the impingement holes170of the impingement wall160in the form of an impingement cooling zone210. The cooling medium130may flow through the impingement wall160in the form of a number of impingement jets so as to provide enhanced backside heat transfer with respect to the external wall150. The cooling medium130then may flow through the external wall pedestals190between the impingement wall160and the external wall150in the form of an external wall pedestal cooling zone220. The cooling medium130flowing through the external wall pedestals190may promote an even distribution of the cooling medium130therein so as to enhance the heat transfer rate, conduct heat from the external wall150to the impingement wall160, and distributes stress from the external wall150to the impingement wall160.

The platform120described herein thus may reduce the cooling medium requirements for improved gas turbine output and efficiency as well as overall service benefits. The platform120or other type of hot gas path component100provides high convective cooling with structural integrity through the combination of the pedestal cooling zones200,220and the impingement zone210. Specifically, the platform120combines the benefits of the thermal stress distribution of the pedestal cooling zones200,220with the higher heat transfer characteristics of the impingement cooling zone210. The overall pressure drop therein may be managed in that the platform120takes one-third of the pressure drop across the internal wall pedestal cooling zone200, one-third of the pressure drop across the impingement cooling zone210, and one-third of the pressure drop across the external wall pedestal cooling zone220. Likewise, the pedestal cooling zones200,220may redistribute the thermal stresses therein for an improved component life cycle. Although the hot gas path component100has been described in the context of the bucket110and the platform120, any type of hot gas component, including a nozzle, a shroud, a liner, a transition piece, and the like may be used herein.