Patent Publication Number: US-2015064019-A1

Title: Gas Turbine Components with Porous Cooling Features

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with U.S. government support under contract number DE-FC26-05NT42643 awarded by the Department of Energy. The government has certain rights in this invention. 
    
    
     TECHNICAL FIELD 
     The present application and the resultant patent relate generally to gas turbine engines and more specifically relate to gas turbine components with porous cooling sections created by direct metal laser melting manufacturing techniques and the like. 
     BACKGROUND OF THE INVENTION 
     Gas turbine systems are widely utilized in fields such as power generation. Overall gas turbine performance and efficiency generally may be increased by increasing internal combustion temperatures. The components that are subject to the high temperatures in the hot gas path, however, must be cooled. For example, an airfoil and other components of a nozzle and the like may be disposed in the hot gas path and exposed to the relatively high combustion temperatures. A cooling flow therefore may be routed from the compressor or elsewhere and provided to the various components in the hot gas path. 
     A variety of methods may be used for cooling the airfoils and the other components. These methods may include running a cooling flow on the interior side of the component, running the cooling flow through an impingement sleeve that impinges the flow on the backside of the component so as to increase the heat transfer coefficient therein, running the coolant through cooling holes to the exterior of the component to convectively cool, and exhausting the coolant from the cooling holes as film to provide a layer of cool air over the exterior so as to reduce exterior temperatures. Although the use these methods may provide adequate cooling for the airfoils, a further increase in cooling efficiency is desired. Such an increase in efficiency would allow a reduction in the cooling flows required to cool the airfoils and other components and also may provide a reduction in emissions and/or an increase in firing temperatures. 
     SUMMARY OF THE INVENTION 
     The present application and the resultant patent thus provide a hot gas path component for use with a gas turbine engine. The hot gas path component may include an airfoil, an internal cooling cavity, and a porous section created by a direct metal laser melting technique. The porous section may be built into the airfoil or the airfoil may be built separately and attached to the airfoil. 
     The present application and the resultant patent further provide a method of cooling a hot gas path component for use with a gas turbine engine. The method may include the steps of providing the hot gas path component with an internal cooling cavity, creating a porous section via a direct metal laser melting technique, flowing a cooling medium to the internal cooling cavity, and flowing the cooling medium through the porous section to provide transpiration cooling. The creating step may include building up the porous section on the hot gas path component or building the porous section separately and attaching the porous section to the hot gas path component. 
     The present application and the resultant patent further provide an airfoil for use with a gas turbine engine. The airfoil may include a pressure side, a suction side, an internal cooling cavity, and a porous section with a porous media created by a direct metal laser melting technique. 
     These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a gas turbine engine showing a compressor, a combustor, and a turbine. 
         FIG. 2  is a sectional view of a portion of an airfoil. 
         FIG. 3  is a sectional view of a portion of an airfoil as may be described herein. 
         FIG. 4  is an expanded view of a portion of the airfoil of  FIG. 3 . 
         FIG. 5  is a sectional view of an alternative embodiment of an airfoil as may be described herein. 
         FIG. 6  is an expanded view of a portion of the airfoil of  FIG. 5 . 
         FIG. 7  is a sectional view of an alternative embodiment of an airfoil as may be described herein. 
         FIG. 8  is an expanded view of a portion of the airfoil of  FIG. 7 . 
         FIG. 9  is an expanded view of an alternative embodiment of a portion of the airfoil of  FIG. 7 . 
         FIG. 10  is a sectional view of an alternative embodiment of an airfoil as may be described herein. 
         FIG. 11  is an expanded view of a portion of the airfoil of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, in which like numerals refer to like elements throughout the several views,  FIG. 1  shows a schematic view of gas turbine engine  10  as may be used herein. The gas turbine engine  10  may include a compressor  15 . The compressor  15  compresses an incoming flow of air  20 . The compressor  15  delivers the compressed flow of air  20  to a combustor  25 . The combustor  25  mixes the compressed flow of air  20  with a pressurized flow of fuel  30  and ignites the mixture to create a flow of combustion gases  35 . Although only a single combustor  25  is shown, the gas turbine engine  10  may include any number of combustors  25 . The flow of combustion gases  35  is in turn delivered to a turbine  40 . The flow of combustion gases  35  drives the turbine  40  so as to produce mechanical work. The mechanical work produced in the turbine  40  drives the compressor  15  via a shaft  45  and an external load  50  such as an electrical generator and the like. 
     The gas turbine engine  10  may use natural gas, liquid fuels, various types of syngas, and/or other types of fuels and combinations thereof. The gas turbine engine  10  may 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 engine  10  may 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. 
       FIG. 2  shows a sectional view of an example of a hot gas path component  55 . In this example, the hot gas path component  55  may be an airfoil  60 . The airfoil  60  may be part of a nozzle, a bucket, or any other type of hot gas path component  55  such as a shroud and the like. The airfoil  60  may include an outer shell  65 . The airfoil  60  may extend from a pressure side  70  to a suction side  75 . The airfoil  60  also may extend from a leading edge  80  to a trailing edge  85 . The airfoil  60  may have an overall aerodynamic shape. The shell  65  may define a number of internal cooling cavities  90  in communication with a number of film cooling holes  92  extending through the shell  65 . A number of pin banks  94  also may extend into the internal cooling cavities  90 . A portion of the flow of air  20  may be diverted from the compressor  15  so as to cool the airfoil  60 . The flow of air  20  may extend through the internal cooling cavities  90  and may exit about the film cooling holes  92  or elsewhere. The pin banks  94  may provide turbulence to the flow of air  20 . Many other types of hot gas path components  55  and airfoils  60  may be used. Likewise many different types of cooling schemes and components also may be used. 
       FIGS. 3 and 4  show a hot gas path component  100  as may be described herein. In this example, the hot gas path component  100  may be an airfoil  110 . The airfoil  110  may be part of a nozzle or a bucket. Other types of hot gas path components  100 , such as a shroud and the like, also may be used herein. The airfoil  110  may include a shell  120 . The shell  120  may have an interior surface  130  and an exterior surface  140 . The interior surface  130  may have an impingement sleeve  135 , an impingement plate, or a similar type of structure adjacent thereto. The shell  130  may extend from a pressure side  150  to a suction side  160 . Likewise, the airfoil  110  may extend from a leading edge  170  to a trailing edge  180  and may define a substantially aerodynamic shape. The shell  120  may define a number of internal cooling cavities  190  about the inner surface  130  thereof. A number of film cooling holes  200  may extend through the shell  120 . A number of pin banks  210  also may be positioned within the internal cavities  190 . Other components and other configurations also may be used herein. 
     The airfoil  110  also may have a porous trailing edge section  220 . The porous trailing edge section  220  may be filled with a porous media  230 . The porous media  230  may be formed from any suitable porous material or materials having a matrix with a number of voids therein. The porous media  230  may be formed from a metal foam, a metal alloy foam, a ceramic foam, such as a ceramic matrix composite foam, a carbon fiber foam, and similar types of porous materials. Non-limiting examples of specific materials may include Rene 142, Rene 195, MarM247, GTD111, GTD444, IN738, H282, H230, IN625 and the like. The foam typically may be formed by mixing a material, such as a metal, a ceramic, a carbon fiber, and the like with another substance and then melting the substance so as to leave the porous foam. The porous media  230  may be “printed” or built up via a direct metal laser melting (“DMLM”) process and the like. Different types of sintering techniques and other types of manufacturing techniques also may be used herein to create the components herein. The porous media may vary in porosity/permeability throughout based on optimizing the cooling flow therethrough. For example, permeability may be lowest in regions of highest heat load so that more coolant flows through these regions as compared to regions where the heat load and the coolant demand may be lower. A cooling medium  240  may flow through the voids in the porous media  230  so as to facilitate cooling in a highly efficient manner. 
     The porous trailing edge section  220  may be built directly onto the airfoil  110  or the porous trailing edge section  220  may be built separately and attached by any number of different techniques. These techniques may include including brazing, arc welding, high energy density welding such as laser welding and electron beam welding, TLP bonding, diffusion bonding, or different types of mechanical attachment. The buildup of the porous media  230  may be made over an existing component or as part of building a component as a whole. The use of the DMLM process enables high heat transfer through the porous media  230  while providing a high quality joint between the airfoil  110  and the porous trailing edge section  220 . The porous trailing edge section  220  may have an external sleeve  250  extending in whole or in part to direct the flow to exit over only a certain section or sections of the trailing edge. The external sleeve  250  may be a metallic component, a thermal barrier coating, and the like. The coating may be an aluminide and the like sprayed thereon. The cooling medium  240  thus flows through the airfoil  110  and exits via the porous trailing edge section  220  so as to cool the trailing edge  180 . Other components and other configurations may be used herein. 
       FIGS. 5 and 6  show a further example of a hot gas path component  100 . In this example, the hot gas path component  100  may be an airfoil  260 . The airfoil  260  may include a porous side section  270  positioned on the suction side  160 . The porous side section  270  may include the porous media  230 . Specifically the porous media  230  may be built or attached into the shell  120  of the airfoil  260  along the impingement sleeve  135  or about a grid on the underlying structure. The porous media  230  may be aligned with the shell so as to provide transpiration cooling and the like. The cooling flow  240  thus may leak through the voids in the porous side section  270 . Any number of the porous side sections  270  may be used herein in any size or shape. As above, the porosity and the permeability may be varied throughout the porous piece so as to optimize cooling usage. Other components and other configurations may be used herein. 
       FIGS. 7-9  show a further example of a hot gas path component  100 . In this example, the hot gas path component  100  may be an airfoil  280 . The airfoil  280  may include a porous external section  290  positioned on the suction side  160  or elsewhere along the airfoil  280 . Specifically, the porous external section  290  may include a buildup of the porous media  230  on the shell  120 . Alternatively, the porous section may be built up separately and attached by any number of different techniques including those mentioned above. The shell  120  and the porous external section  290  may be in communication with the film cooling holes  200  extending through the shell  120 . As is shown in  FIG. 8 , an external sleeve  300  may be used over the porous media  230 . A number of external film cooling holes  310  may be positioned on the external sleeve  300 . The external sleeve  300  may be metallic, a thermal barrier coating, and the like. As is shown in  FIG. 9 , the external sleeve  300  may be optional such that the porous media  230  may not need any type of covering. The external sleeve  300  may cover all, part, or none of the porous media  230 . The cooling flow  240  thus may flow through the film cooling holes  200 , the porous media  230  and/or the external film cooling holes  310 . The film cooling holes may be partially formed in the porous media to improve flow distribution into the porous media. Other components and other configurations also may be used herein. 
       FIGS. 10 and 11  show a further embodiment of a hot gas path component  100 . In this example, the hot gas path component  100  may be an airfoil  320 . The airfoil  320  may include a porous internal section  330 . The porous internal section  330  may include a buildup of the porous media  230  about the optional impingement sleeve  135  along the film cooling holes  200  or elsewhere within the shell  120  in whole or in part. Alternatively, the porous media may be built separately and attached by a variety of methods such as those described above. The permeability and porosity of the porous media may vary as needed to optimize coolant usage. The cooling flow  240  thus may flow through the impingement sleeve  135 , the porous media  230 , and the film cooling holes  200 . The film cooling holes may be partially formed in the porous media to ensure an optimal film hole shape for maximized film effectiveness. Other components and other configurations may be used herein. 
     A number of alternative hot gas path components  100  also may be used herein. Specifically, DMLM techniques may be used to build both porous and solid features of the hot gas path component  100 . These DMLM techniques may be used to vary the porosities and/or the permeability at different locations within the porous media  230 . The DMLM techniques thus can be used to build multiple different discrete porous structures inside or outside thereof. Other methods of making and attaching the porous material may be used as well. 
     The hot gas path component  100  provides these integral porous features so as to enable better heat transfer as well as providing transpiration cooling. The use of the porous media  230  thus should reduce overall cooling load requirements. Specifically, the porous media has been shown to have a significantly higher heat transfer coefficient as compared to known airfoil materials as well as provides superior control over the distribution of coolant over the part. Using such a process on the hot gas path components in multiple locations may increase heat transfer capability while reducing cooling flow requirements. Moreover, the use of the DMLM process provides the porous foam with an integral joint to the base metal when built directly onto the part or as a whole with the part. The DMLM process also provides control over the porosity and the permeability throughout the part. 
     It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.