Abstract:
A cooling system according to an embodiment includes: a pin fin bank cooling circuit; and an air feed cavity for supplying cooling air to the pin fin bank cooling circuit; wherein the pin fin bank cooling circuit extends radially outward from and at least partially covers at least one central plenum of a multi-wall blade and a first set of near wall cooling channels of the multi-wall blade.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to co-pending US application numbers: ______, GE docket numbers 282168-1, 282171-1, 282174-1, 283464-1, 283467-1, 283463-1, 283462-1, and 284160-1, all filed on ______. 
       BACKGROUND OF THE INVENTION 
       [0002]    The disclosure relates generally to turbine systems, and more particularly, to a cooling circuit for a tip area of a multi-wall blade. 
         [0003]    Gas turbine systems are one example of turbomachines widely utilized in fields such as power generation. A conventional gas turbine system includes a compressor section, a combustor section, and a turbine section. During operation of a gas turbine system, various components in the system, such as turbine blades, are subjected to high temperature flows, which can cause the components to fail. Since higher temperature flows generally result in increased performance, efficiency, and power output of a gas turbine system, it is advantageous to cool the components that are subjected to high temperature flows to allow the gas turbine system to operate at increased temperatures. 
         [0004]    Turbine blades typically contain an intricate maze of internal cooling channels. Cooling air provided by, for example, a compressor of a gas turbine system may be passed through the internal cooling channels to cool the turbine blades. 
         [0005]    Multi-wall turbine blade cooling systems may include internal near wall cooling circuits. Such near wall cooling circuits may include, for example, near wall cooling channels adjacent the outside walls of a u all blade. The near wall cooling channels are typically small, requiring less cooling flow, still maintaining enough velocity for effective cooling to occur. Other, typically larger, low cooling effectiveness internal channels of a multi-wall blade may be used as a source of cooling air and may be used in one or more reuse circuits to collect and reroute “spent” cooling flow for redistribution to lower heat load regions of the multi-wall blade. At the tip of a multi-wall blade, the near wall cooling channels and low cooling effectiveness internal channels are exposed to very high heat loads. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    A first aspect of the disclosure provides a cooling system including: a pin fin bank cooling circuit, the pin fin bank circuit including a plurality of pins; and an air feed cavity for supplying cooling air to the pin fin bank cooling circuit; wherein the pin fin bank cooling circuit extends radially outward from and at least partially covers at least one central plenum of a multi-wall blade and a first set of near wall cooling channels of the multi-wall blade. 
         [0007]    A second aspect of the disclosure provides a method for forming a pin fin bank cooling circuit, including: separating first, second, and third cores using a plurality of support rods to provide a core assembly; producing a metal casting using the core assembly, the metal casting including: an opening formed between first and second metal faces; and a plurality of sets of opposing holes in the first and second metal faces; and inserting a plug into each set of opposing holes in the first and second metal faces. 
         [0008]    A third aspect of the disclosure provides a turbomachine, including: a gas turbine system including a compressor component, a combustor component, and a turbine component, the turbine component including a plurality of turbine buckets, and wherein at least one of the turbine buckets includes a multi-wall blade; and a cooling system disposed within the multi-wall blade, the cooling system including: a pin fin bank cooling circuit, the pin fin bank circuit including a plurality of pins; and an air feed cavity for supplying cooling air to the pin fin bank cooling circuit; wherein the pin fin bank cooling circuit extends radially outward from and at least partially covers at least one central plenum of the multi-wall blade and a first set of near wall cooling channels of the multi-wall blade. 
         [0009]    The illustrative aspects of the present disclosure solve the problems herein described and/or other problems not discussed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure. 
           [0011]      FIG. 1  shows a perspective view of a turbine bucket including a multi-wall blade according to embodiments. 
           [0012]      FIG. 2  is a cross-sectional view of the multi-wall blade of  FIG. 1 , taken along line A-A in  FIG. 1  according to various embodiments. 
           [0013]      FIG. 3  is a cross-sectional view of a tip area of the multi-wall blade of  FIG. 1 , taken along line B-B in  FIG. 1  according to various embodiments. 
           [0014]      FIG. 4  is a cross-sectional view of a tip area of the multi-wall blade of  FIG. 1 , taken along line B-B in  FIG. 1  according to various embodiments. 
           [0015]      FIG. 5  is a cross-sectional view of a tip area of the multi-wall blade of  FIG. 1 , taken along line B-B in  FIG. 1  according to various embodiments. 
           [0016]      FIGS. 6-8  depict an illustrative method for forming a portion of a pin fin bank cooling circuit according to various embodiments. 
           [0017]      FIG. 9  is a cross-sectional view of a tip area of the multi-wall blade of  FIG. 1 , taken along line B-B in  FIG. 1  according to various embodiments. 
           [0018]      FIG. 10  is a cross-sectional view of a tip area of the multi-wall blade of  FIG. 1 , taken along line B-B in  FIG. 1  according to various embodiments. 
           [0019]      FIG. 11  is a schematic diagram of a gas turbine system according to various embodiments. 
       
    
    
       [0020]    It is noted that the drawing of the disclosure is not to scale. The drawing is intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawing, like numbering represents like elements between the drawings. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    In the Figures, for example in  FIG. 11 , the “A” axis represents an axial orientation. As used herein, the terms “axial” and/or “axially” refer to the relative position/direction of objects along axis A, which is substantially parallel with the axis of rotation of the turbomachine (in particular, the rotor section). As further used herein, the terms “radial” and/or “radially” refer to the relative position/direction of objects along an axis (r), which is substantially perpendicular with axis A and intersects axis A at only one location. Additionally, the terms “circumferential” and/or “circumferentially” refer to the relative position/direction of objects along a circumference (c) which surrounds axis A but does not intersect the axis A at any location. 
         [0022]    As indicated above, the disclosure relates generally to turbine systems, and more particularly, to a cooling circuit for cooling a tip area of a multi-wall blade. 
         [0023]    According to embodiments, the cooling circuit is configured to cool the tip area of a multi-wall blade of a gas turbine engine, while providing shielding to low cooling effectiveness internal channels and providing cooling film. Shielding may also be provided to high cooling effectiveness near wall cooling channels. The cooling circuit may include a pin fin bank cooling circuit, which can be fed with cooling air from a low cooling effectiveness internal channel or a near wall cooling channel. Air passes through the cooling circuit, providing convention cooling, and is exhausted as cooling film to cool the tip area of the multi-wall blade. 
         [0024]    Turning to  FIG. 1 , a perspective view of a turbine bucket  2  is shown. The turbine bucket  2  includes a shank  4  and a multi-wall blade  6  coupled to and extending radially outward from the shank  4 . The multi-wall blade  6  includes a pressure side  8 , an opposed suction side  10 , and a tip area  12 . The multi-wall blade  6  further includes a leading edge  14  between the pressure side  8  and the suction side  10 , as well as a trailing edge  16  between the pressure side  8  and the suction side  10  on a side opposing the leading edge  14 . 
         [0025]    The shank  4  and multi-wall blade  6  may each be formed of one or more metals (e.g., steel, alloys of steel, etc.) and may be formed (e.g., cast, forged or otherwise machined) according to conventional approaches. The shank  4  and multi-wall blade  6  may be integrally formed (e.g., cast, forged, three-dimensionally printed, etc.), or may be formed as separate components which are subsequently joined (e.g., via welding, brazing, bonding or other coupling mechanism). 
         [0026]      FIG. 2  is a cross-sectional view of the multi-wall blade  6  taken along line A-A of  FIG. 1 . As shown, the multi-wall blade  6  may include, for example, an arrangement  30  of cooling channels including a plurality of high effectiveness near wall cooling channels  18  and one or more low cooling effectiveness internal channels  20 , hereafter referred to as “central plenums.” Various cooling circuits can be provided using different combinations of the near wall cooling channels  18  and central plenums  20 . 
         [0027]    An embodiment including a pin fin bank cooling circuit  40  is depicted in  FIG. 3 , which is a cross-sectional view of the multi-wall blade  6  taken along line B-B of  FIG. 1 . The pin fin bank cooling circuit  40  is located radially outward along the multi-wall blade  6  (e.g., closer to the tip area  12  of the multi-wall blade  6 ) relative to the arrangement  30  of cooling channels shown in  FIG. 2 . To this extent, comparing  FIGS. 2 and 3 , the pin fin bank cooling circuit  40  effectively “shields” the central plenums  20  and at least some of the near wall cooling channels  18  from the very high heat loads that typically occur at the tip area.  12  of the multi-wall blade  6  during rotation of the multi-wall blade  6  (e.g., in a gas turbine). 
         [0028]    The pin fin bank cooling circuit  40  includes a plurality of thermally conductive (e.g., metal) pins  42  disposed within an opening  44  formed in an area between the leading and trailing edges  14 ,  16  of the multi-wall blade  6 . In the embodiment depicted in  FIG. 3 , the opening  44  extends rearward from a forward air feed cavity  46  toward the trailing edge  16  of the multi-wall blade  6 . Comparing  FIGS. 2 and 3 , it can be seen that the opening  44  (and thus a set (e.g., one or more) of the pins  42  of the pin fin bank cooling circuit  40 ) extends over and at least partially covers at least one of the central plenums  20 . Further, again comparing  FIGS. 2 and 3 , it can be seen that the opening  44  (and thus another set of the pins  42  of the pin fin bank cooling circuit  40 ), extends over and at least partially covers a set of the near wall cooling channels  18  disposed adjacent the pressure side  8  of the multi-wall blade  6 . 
         [0029]    Cooling air is supplied to the opening  44  of the pin fin bank cooling circuit  40  via the forward air feed cavity  46 . The air feed cavity  44  may be fluidly coupled to, and receive cooling air from, at least one of the central plenums  20 . In other embodiments, the forward air feed cavity  46  may be fluidly coupled to, and receive cooling air from, at least one of the near wall cooling channels  18 . In either case, in this embodiment, the air feed cavity  46  is disposed near the leading edge  14  of the multi-wall blade  6 . 
         [0030]    In  FIG. 3 , viewed in conjunction with  FIGS. 1 and 2 , cooling air flows from the air feed cavity  46  (e.g., out of the page in  FIG. 3 ) into the opening  44 . The cooling air flows from the air feed cavity  46  toward the trailing edge  16  of the multi-wall blade  6 , through the opening  44  and past the pins  42 . The pins  42  of the pin fin bank cooling circuit  40  are oriented substantially perpendicular to the flow of cooling air through the opening  44  (e.g., into or out of the page in  FIG. 3 ). The pins  42  provide convective heat flow and promote turbulent air flow, enhancing cooling effectiveness. In the opening  44  of the pin fin bank cooling circuit  40 , the cooling air absorbs heat (e.g., via convention) from adjacent portions of the tip area  12  of the multi-wall blade  6 , shielding the underlying near wall cooling channels  18  and central plenums  20  from excessive heat. Possible locations of the pins  42  in the opening  44  of the pin fin bank cooling circuit  40  are shown in  FIG. 3  (and also in  FIG. 4 , as detailed below). The depicted locations of the pins  42  are for illustration only and are not meant to be limiting. 
         [0031]    The cooling air flows out of the opening  44  (e.g., out the page in  FIG. 3 ) via at least one tip film channel  48 . Cooling air is directed by the tip film channels  48  to the tip  22  of the multi-wall blade  6 . The cooling air is exhausted from the tip  22  of the multi-wall blade  6  as tip film  24  to provide tip film cooling. In addition, cooling air may be exhausted out of the opening  44  to the pressure side  8  of the multi-wall blade  6  through at least one pressure side film channel  50  to provide film  52  for pressure side film cooling. 
         [0032]    Cooling air may also be exhausted from at least one of the near wall cooling channels  18  to the tip  22  to provide tip film cooling. For example, as shown in  FIG. 3 , at least one of the near wall cooling channels  18  may be fluidly coupled to the tip  22  of the multi-wall blade  6  by at least one tip film channel  54 . Cooling air is exhausted (out of the page in  FIG. 3 ) from the tip film channels  54  to provide tip film  24  for tip film cooling. The depicted locations of the tip film channels  48 ,  50  are for illustration only and are not meant to be limiting. 
         [0033]    In an embodiment, as shown in  FIG. 3 , a set of the pins  42  may be removed from a section  56  of the opening  44 . This encourages, for example, a flow of cooling air (arrow X) from the forward air feed cavity  46  toward pins  42  in the aft portion of the opening  44  of the pin fin bank cooling circuit  40 . This helps to provide more uniform cooling across the opening  44 . 
         [0034]    In another embodiment, an aft air feed cavity  146  disposed adjacent the trailing edge  16  of the multi-wall blade  6  may be used to supply cooling air to the pin fin bank cooling circuit  140 . Such a configuration is depicted in  FIG. 4 , viewed in conjunction with  FIGS. 1 and 2 . 
         [0035]    The pin fin bank cooling circuit  140  illustrated in  FIG. 4  includes a plurality of thermally conductive (e.g., metal) pins  142  disposed within an opening  144  formed in an area between the leading and trailing edges  14 ,  16  of the multi-wall blade  6 . The opening  144  extends forward from an aft air feed cavity  146  toward the trailing edge  16  of the multi-wall blade  6 . The opening  44  (and thus a set (e.g., one or more) of the pins  142  of the pin fin bank cooling circuit  140 ) extends over and at least partially covers at least one of the central plenums  20 . Further, the opening  144  (and thus another set of the pins  142  of the pin fin bank cooling circuit  140 ), extends over and at least partially covers a set of the near wall cooling channels  18  disposed adjacent the pressure side  8  of the multi-wall blade  6 . 
         [0036]    The air feed cavity  146  may be fluidly coupled to, and receive cooling air from, at least one of the central plenums  20  or at least one of the near wall cooling channels  18 . As with the embodiment shown in  FIG. 3 , the pin fin bank cooling circuit  140  depicted in  FIG. 4  is configured to shield the central plenums  20  and at least some of the pressure side near wall cooling channels  18  from the very high heat loads that typically occur at the tip area  12  of the multi-wall blade  6 . Further, the pin fin bank cooling circuit  140  depicted in  FIG. 4  is configured to provide tip film  24  and pressure side film  52  for tip film cooling and pressure side film cooling, respectively. 
         [0037]    A set of the pins  142  may be removed from a section  156  of the opening  144 . This encourages, for example, a flow of cooling air (arrow Y) from the aft air feed cavity  146  toward pins  142  in the forward portion of the opening  144  of the pin fin bank cooling circuit  140 . This helps to provide more uniform cooling across the opening  144 . 
         [0038]    In yet another embodiment, as depicted in  FIG. 5 , viewed in conjunction with  FIGS. 1 and 2 , the opening  244  of a pin fin bank cooling circuit  240  may be enlarged to extend over and at least partially cover not only the central plenums  20  (e.g., as in  FIG. 3 ), but also a set of the near wall cooling channels  18  disposed adjacent the suction side  10  of the multi-wall blade  6 . As in the embodiment depicted in  FIG. 3 , the opening  244  of the pin fin bank cooling circuit  240  extends over and at least partially covers a set of the near wall cooling channels  18  disposed adjacent the pressure side  8  of the multi-wall blade  6 . A set of the pins  242  may be removed from a section  256  of the opening  244  to enhance the flow of cooling air from a forward air feed cavity  246  to an aft region of the opening  244 . 
         [0039]    A forward air feed cavity  246  may be fluidly coupled to, and receive cooling air from, at least one of near wall cooling channels  18  or at least one of the central plenums  20 . The pin fin bank cooling circuit  240  depicted in  FIG. 5  is configured to shield the central plenums  20 , at least some of the suction side near wall cooling channels  18 , and at least some of the pressure side near wall cooling channels  18  from the very high heat loads that typically occur at the tip area  12  of the multi-wall blade  6 . Further, similar to the embodiment shown in  FIG. 3 , the pin fin bank cooling circuit  240  depicted in  FIG. 5  is configured to provide tip film  24  and pressure side film  52  for tip film cooling and pressure side film cooling, respectively. 
         [0040]    In  FIG. 5 , the forward air feed cavity  246  is disposed near the leading edge  14  of the multi-wall blade  6 . However, similar to the embodiment shown in  FIG. 4 , the air feed cavity  246  may be disposed near the trailing edge  16  of the multi-wall blade  6 . 
         [0041]      FIGS. 6-8  depict an illustrative method for forming a portion  60  of the pin fin bank cooling circuit  40  according to an embodiment. A cross-sectional view of a core  62  (e.g., a ceramic core) for use in a process for casting the portion  60  of the pin fin bank cooling circuit  40  is shown in  FIG. 6 . 
         [0042]    The core  62  includes a squealer core section  64 , a tip core section  66 , and at least one body core section  68 . Support rods  70  secure and separate the various core sections  64 ,  66 ,  68 . The squealer core section  64  will form, after casting, a cavity at the tip  22  of the multi-wall blade  6  that is radially open to the outside. The tip core section  66  will form, after casting, the opening  44  of the pin fin bank cooling circuit  40 . The body core section  68  will form, after casting at least one of the near wall cooling channels  18  or central plenums  20 . 
         [0043]    An example of a metal casting  80  produced using the core  62  (e.g., using known casting techniques) is depicted in  FIG. 7 . The casting  80  includes a plurality of openings  82  corresponding to the locations of the support rods  70  in the core  62 . According to an embodiment, as shown in  FIG. 8 , each opening  82  may be sealed using a metal (e.g., braze material) plug  84 . The plug  84  can, for example, be inserted into an opening  82 , press-fit or otherwise inserted into an intra-cavity rib  86  of the casting  80 , and secured (e.g., via brazing) to the floor  88  of the squealer cavity  90  and the intra-cavity rib  86 . To this extent, the plugs  84  extend completely through the opening  92  between the intra-cavity rib  86  and the floor  88  of the squealer cavity  90 , preventing cooling air from leaking out of the opening  92  through the openings  82 . 
         [0044]    The opening  92  between the intra-cavity rib  86  and the floor  88  of the squealer cavity  90  may be used, for example, to provide the opening  44  of the pin fin bank cooling circuit  40 , with the plugs  84  oriented substantially perpendicular to the flow of cooling air (e.g., into or out of the page in  FIG. 8 ) through the opening  92 . In this position, the plugs  84  not only seal the openings  82  on opposing sides of the opening  92 , but also serve as cooling pins, increasing the cooling effectiveness of the pin fin bank cooling circuit  40  by improving convective heat flow and promoting turbulent air flow. Possible locations of the plugs  84  in the opening  44  of the pin fin bank cooling circuit  40  are shown in  FIG. 9 . The depicted locations of the plugs  84  in  FIG. 9  are for illustration only and are not meant to be limiting. The plugs  84  may be used in any of the embodiments disclosed herein. 
         [0045]    According to another embodiment, as depicted in  FIG. 10 , a rib  100  may be provided in the opening  44 . Such a rib  100  encourages (e.g., by redirection) a flow of cooling air from the forward air feed cavity  46 , into the opening  44 , and toward pins  42  in the aft portion of the opening  44  of the pin fin bank cooling circuit  40 . 
         [0046]      FIG. 11  shows a schematic view of gas turbomachine  102  as may be used herein. The gas turbomachine  102  may include a compressor  104 . The compressor  104  compresses an incoming flow of air  106 . The compressor  104  delivers a flow of compressed air  108  to a combustor  110 . The combustor  110  mixes the flow of compressed air  108  with a pressurized flow of fuel  112  and ignites the mixture to create a flow of combustion gases  114 . Although only a single combustor  110  is shown, the gas turbomachine  102  may include any number of combustors  110 . The flow of combustion gases  114  is in turn delivered to a turbine  116 , which typically includes a plurality of turbine buckets  2  ( FIG. 1 ). The flow of combustion gases  114  drives the turbine  116  to produce mechanical work. The mechanical work produced in the turbine  116  drives the compressor  104  via a shaft  118 , and may be used to drive an external load  120 , such as an electrical generator and/or the like. 
         [0047]    In various embodiments, components described as being “coupled” to one another can be joined along one or more interfaces. In some embodiments, these interfaces can include junctions between distinct components, and in other cases, these interfaces can include a solidly and/or integrally formed interconnection. That is, in some cases, components that are “coupled” to one another can be simultaneously formed to define a single continuous member. However, in other embodiments, these coupled components can be formed as separate members and be subsequently joined through known processes (e.g., fastening, ultrasonic welding, bonding). 
         [0048]    When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element, it may be directly on, engaged, connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0049]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0050]    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.