Patent Publication Number: US-7581924-B2

Title: Turbine vanes with airfoil-proximate cooling seam

Description:
FIELD OF THE INVENTION 
   The invention relates in general to turbine engines and, more particularly, to turbine vanes. 
   BACKGROUND OF THE INVENTION 
     FIG. 1  shows an example of a known turbine vane  10 . The vane  10  includes an airfoil  12  bounded at each of its ends by a platform  14 . The airfoil  12  and the platforms  14  are commonly formed as a single piece. The airfoil  12  is usually centrally located on each of the platforms  14  such that each end of the airfoil  12  is completely surrounded by the platform  14 . Each platform  14  has opposite circumferential ends  16 . The region  18  in which the airfoil  12  transitions into each platform  14  is typically configured as a fillet  20 . The transition region  18  is an area that experiences high thermal stresses; however, the transition region  18  has historically proved to be a challenging area to adequately cool. 
   A plurality of vanes  10  are arranged in an annular array in the turbine section of the engine to form a row of vanes. When installed, the circumferential end  16  of each vane platform  14  abuts a circumferential end  16  of an adjacent vane platform  14 , as shown in  FIG. 2 . The abutting circumferential ends  16  form a seam  22 . The seam  22  is located midway between each pair of neighboring airfoils  12 . 
   During engine operation, high pressure coolant can be supplied to the platforms  14 . The seam  22  presents a potential leak path for the coolant. Despite efforts to seal the seam  22 , a portion of the coolant inevitably leaks through the seam  22  and enters the turbine gas path. While providing some cooling benefit to the abutting portions of the platforms  14 , such leakage flow through the seam  22  is not well controlled or optimized, resulting in excessive leakage in an area that requires relatively little cooling. Thus, there is a need for a turbine vane system that can make productive use of the leakage flow through the seam between adjacent vanes. 
   SUMMARY TO THE INVENTION 
   Aspects of the invention are directed to a turbine vane. The vane includes an airfoil that has a first end region and a second end region. The airfoil also has a pressure side and a suction side. Further, the airfoil has a leading edge, a trailing edge, and an airfoil mean line that extends from the leading edge to the trailing edge. 
   The vane includes a first platform that is unitary with the airfoil. The first platform transitions into the airfoil in the first end region. The first platform is located substantially entirely on either the pressure side or the suction side of the airfoil. The first platform extends substantially circumferentially from the airfoil to a circumferential side. The circumferential side is contoured to engage another airfoil. For example, the circumferential side can be contoured to substantially matingly engage the outer peripheral surface of another airfoil. 
   In one embodiment, the first platform can be located substantially entirely on the pressure side of the airfoil. In such case, the circumferential side can be contoured to engage the suction side of another airfoil. Alternatively, the first platform can be located substantially entirely on the suction side of the airfoil, and the circumferential side of the first platform can be contoured to engage the pressure side of another airfoil. 
   The turbine vane can further include a second platform unitary with the airfoil. The second platform can transition into the airfoil in the second end region. The second platform can be located substantially entirely on either the pressure side or the suction side of the airfoil. In one embodiment, the first and second platforms can be located on the same side of the airfoil. From the airfoil, the second platform can extend substantially circumferentially to a circumferential side that is contoured to engage another airfoil. 
   In one embodiment, the first platform does not substantially extend beyond a boundary defined by an imaginary extrapolation of the airfoil mean line beyond the airfoil. In another embodiment, the first platform does not substantially extend beyond a boundary defined by an imaginary axial line extending from the leading edge of the airfoil and an imaginary axial line extending from the trailing edge of the airfoil. 
   The outer peripheral surface of the airfoil on the opposite one of the pressure side and the suction side of the airfoil from the first platform can be exposed in the first end region. Alternatively, the first platform can further include a platform lip that extends in the first end region about the opposite one of the pressure side and the suction side of the airfoil from the first platform. 
   Aspects of the invention also concern a turbine vane system. The system includes a first turbine vane and a second turbine vane. The first turbine vane includes a first airfoil with a unitary first outer platform. The first airfoil has an outer region, an inner end region, an outer peripheral surface, a pressure side, a suction side, a leading edge, a trailing edge, and an airfoil mean line that extends from the leading edge to the trailing edge. The first outer platform transitions into the first airfoil in the outer end region. The first outer platform is located substantially entirely on either the pressure side or the suction side of the first airfoil. 
   The second turbine vane includes a second airfoil with a unitary second outer platform. The second airfoil has an outer end region, an inner end region, a pressure side, a suction side, a leading edge, a trailing edge, and an airfoil mean line that extends from the leading edge to the trailing edge. The second outer platform transitions into the second airfoil in the outer end region. The second outer platform is located substantially entirely on the same one of the pressure side and the suction side of the second airfoil as the first outer platform relative to the first airfoil of the first turbine vane. The second outer platform extends substantially circumferentially from the second airfoil to a circumferential side, which is contoured to engage at least a portion of the side of the first airfoil opposite the first outer platform. For instance, the circumferential side can be contoured to substantially matingly engage at least a portion of the outer peripheral surface of the first airfoil in the outer end region. 
   The first vane is positioned substantially adjacent the second vane such that the outer end region of the first airfoil is substantially cooperatively enclosed by the first outer platform and the circumferential end of the second outer platform. A seam is formed between the substantially adjacent portions of the first and second vanes. The system can further include a seal operatively positioned along at least a portion of the seam. The seam includes a cooling gap that extends proximate the side of the first airfoil that is opposite the first outer platform. The system also can include a coolant supplied to the outer platform. At least a portion of the coolant can flow through the cooling gap such that the interface between the circumferential end of the second outer platform and the first airfoil can be cooled. 
   The first outer platform can be located substantially entirely on the pressure side of the first airfoil, and the circumferential side of the second outer platform can be contoured to engage the suction side of the first airfoil. Alternatively, the first outer platform can be located substantially entirely on the suction side of the first airfoil, and the circumferential side of the second outer platform can be contoured to engage the pressure side of the first airfoil. 
   The first outer platform can include a platform lip, which can extend in the outer end region of the airfoil and about the opposite one of the pressure side and the suction side of the airfoil from the first platform. By providing such a lip, the cooling gap can be formed in part between the platform lip of the first outer platform and the circumferential end of the second outer platform. In one embodiment, the outer peripheral surface of the first airfoil on the opposite one of the pressure side and the suction side of the first airfoil from the first outer platform can be exposed in the outer end region. As a result, the cooling gap can be formed in part between the outer peripheral surface of the first airfoil and the circumferential end of the second outer platform. 
   In one embodiment, the first outer platform does not extend substantially beyond a boundary defined by an imaginary extrapolation of the mean line beyond the first airfoil. In another embodiment, the first outer platform does not extend substantially beyond a boundary defined by an imaginary axial line extending from the leading edge of the first airfoil and an imaginary axial line extending from the trailing edge of the first airfoil. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an isometric view of a known turbine vane. 
       FIG. 2  is a cross-sectional view of a pair of adjacent turbine vanes in a known turbine engine. 
       FIG. 3  is an isometric view of a turbine vane according to aspects of the invention. 
       FIG. 4  is a cross-sectional view of a turbine vane configured according to aspects of the invention, viewed from line  4 - 4  in  FIG. 3 , wherein the platform is formed on the suction side of the airfoil. 
       FIG. 5  is a cross-sectional view of an alternative turbine vane configured according to aspects of the invention, wherein the platform is formed on the pressure side of the airfoil. 
       FIG. 6  is a cross-sectional view of a pair of adjacent turbine vanes configured in accordance with aspects of the invention. 
       FIG. 7  is a cross-sectional view of an alternative turbine vane configuration according to aspects of the invention, wherein the platform is formed on the suction side of the airfoil and the pressure side of the airfoil includes a platform lip. 
       FIG. 8  is an isometric view of a pair of adjacent turbine vanes configured in accordance with aspects of the invention. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
   Aspects of the present invention are directed to a vane system that can take advantage of the platform seam coolant leakage flow, which would otherwise be wasted in prior turbine vane systems. Aspects of the present invention involve a relocation of the seam to a location proximate the airfoil so that leakage flow therethrough can be used to cool the transition region between the airfoil and the platforms. Embodiments of the invention will be explained in the context of several possible vane configurations, but the detailed description is intended only as exemplary. Embodiments of the invention are shown in  FIGS. 3-8 , but the present invention is not limited to the illustrated structure or application. 
     FIG. 3  shows a turbine vane  30  according to aspects of the invention. The turbine vane  30  includes an elongated airfoil  32 . The airfoil  32  has an outer peripheral surface  34  that is generally divided between a pressure side  36  and a suction side  38 . The airfoil  32  can have an outer end region  40  that includes an outer end  42 . Further, the airfoil  32  can have an inner end region  44  that includes an inner end  45  (see  FIG. 8 ). The terms “inner” and “outer,” as used herein, are intended to mean relative to the axis of the turbine when the vane  30  is installed in its operational position. The airfoil  32  can have a leading edge  46 , a trailing edge  48  and a mean line  50 . The mean line  50  is an imaginary line extending from the leading edge  46  to the trailing edge  48  and is equidistant from the pressure and suction sides  36 ,  38  of the airfoil  32 . 
   The turbine vane  10  can also include an inner platform  52  and an outer platform  54 . The inner and outer platforms  52 ,  54  are formed with the airfoil  32  so as to be a single piece, that is, as a unitary construction. The inner platform  52  can transition into the airfoil  32  at the inner end region  44  of the airfoil  32 . Similarly, the outer platform  54  can transition into the airfoil  32  at the outer end region  40 . 
   According to aspects of the invention, one or both of the inner and outer platforms  52 ,  54  can be located substantially entirely on one of the pressure side  36  or the suction side  38  of the airfoil  32 .  FIGS. 3 and 4  show an embodiment of a vane  10  in accordance with aspects of the invention in which the inner platform  52  and the outer platform  54  are formed substantially entirely on the suction side  38  of the airfoil  32 . Because there is no platform on the pressure side  36  of the airfoil  32 , the outer peripheral surface  34  of the airfoil  32  can be exposed on the pressure side  36  in each of the end regions  40 ,  44 . 
   From the suction side  38  the airfoil  32 , each platform  52 ,  54  can extend circumferentially to a circumferential side  56 . At least a portion of the circumferential side  56  can be contoured for engagement with a portion of a neighboring airfoil. In the embodiment shown in  FIGS. 3 and 4 , the circumferential side  56  can be contoured for engagement with at least a portion of the pressure side of a neighboring airfoil. Preferably, the circumferential side  56  is contoured for substantially mating engagement with at least a portion of the pressure side of a neighboring airfoil. 
   The platforms  52 ,  54  can also extend from the airfoil  32  to an axial forward side  58  and an axial rearward side  60 . The airfoil  32  can be located substantially centrally between the axial forward side  58  and the axial rearward side  60  of each platform. The terms “axial,” “circumferential” and variants thereof are intended to mean relative to the axis of the turbine when the vane  30  is installed in its operational position. The configuration of the inner platform  52  may or may not be substantially identical to the configuration of the outer platform  54 . 
   Generally, the inner and outer platforms  52 ,  54  are formed on the suction side  38  of the airfoil  32  so as not to extend beyond the leading edge  46  and the trailing edge  48  of the airfoil  32 . In one embodiment, the inner and outer platforms  52 ,  54  can be located substantially entirely on the suction side  38  of the airfoil  32  such that a substantial majority of each platform  52 ,  54  does not extend beyond a boundary defined by an imaginary extrapolation  62  of the airfoil mean line  50  beyond the outer peripheral surface  34  of the airfoil  32 . Alternatively, the inner and outer platforms  52 ,  54  can be located substantially entirely on the suction side  38  of the airfoil  32  such that a substantial majority of each platform does not substantially extend beyond a boundary defined by an imaginary axial line  64  extending from the leading edge  46  of the airfoil  32  and an imaginary axial line  66  extending from the trailing edge  48  of the airfoil  32 . However, as shown in  FIG. 4 , portions of one or both platforms  52 ,  54  can cross each of these boundaries. 
   Aspects of the invention are not limited to embodiments in which the platforms  52 ,  54  are formed on the suction side  38  of the airfoil  32 . For instance, as shown in  FIG. 5 , the platforms  52 ,  54  can be formed on the pressure side  36  of the airfoil  32  as well. In such case, the suction side  38  of the airfoil  32  can be exposed in each of the end regions  40 ,  44 . The above discussion with respect to embodiments of the invention shown in  FIGS. 3 and 4  can have equal application to the platform configuration shown in  FIG. 5 . It should be noted that the circumferential sides  56  of the platforms  52 ,  54  can be adapted to receive suction side of a neighboring airfoil. 
   Further, aspects of the invention are not limited to embodiments in which the side of the airfoil opposite the unitary platform is exposed in the end region. For instance,  FIG. 7  shows an embodiment in which the platform  52  is formed on the suction side  38  of the airfoil  32 . The platform  52  can continue as a small lip  68  extending along the pressure side  36  of the airfoil  32 . The platform lip  68  can generally follow the contour of the outer peripheral surface  34  of the airfoil  32 . The platform lip  68  remains sufficiently close to the airfoil  32  in order to gain any cooling benefit in accordance with aspects of the invention, as will be explained in more detail later. In one embodiment, the platform lip  68  extends about 0.25 inches from the airfoil  32 . However, aspects of the invention are not limited to any particular width of the platform lip  68 . 
   In any given row of vanes, one or more of the vanes can be constructed in accordance with aspects of the invention. The vanes can be connected to a vane carrier (not shown) or other stationary support structure (not shown) in the turbine section.  FIG. 6  shows two adjacent vanes configured in accordance with aspects of the invention. A first vane  70  and a second vane  72  can be brought together so that the unitary platform  52  of the first vane  70  and the unitary suction side platform  52  of the adjacent second vane  72  cooperatively enclose the airfoil  32  of the first vane  70 . As shown, a seam  78  is formed between the abutting portions of the first and second vanes  70 ,  72 . In contrast to prior vane systems, the seam  78  is not located in a central region between two neighboring airfoils. Rather, the seam  78  is extends about the pressure side  36  of the airfoil  32 . The seam  78  can extend away from the leading edge  46  of the airfoil  32  in a generally axially forward direction. Likewise, the seam  78  can extend away from the trailing edge  48  of the airfoil  32  in a generally axially rearward direction. As a result, a cooling gap  80  is formed about the pressure side  36  of the airfoil  32 . 
   It should be noted that the circumferential side  56  of the platform  52  associated with the second vane  72  can engage the airfoil  32  of the first vane  70  in any of a number of ways. For instance, the circumferential end  56  can engage the outer peripheral surface  34  of the airfoil  32  in the end region  40  of the pressure side  36  of the vane  32 . Alternatively or in addition, at least a portion of the circumferential end  56  can extend under the platform  52  associated with the first vane  70  so as to engage at least a portion of the inner end (not shown) of the first airfoil  32 . For a vane  10  configured as shown in  FIG. 7 , the circumferential end  56  can engage at least a portion of the platform lip  68 . It will be understood that these are just a few examples of the various ways in which the circumferential ends of the platform can engage the airfoil. Though the above discussion concerned the engagement between the inner platform  52  and the inner end region  44  of the airfoil  32 , it will be understood that the discussion is equally applicable to the interactions at the outer end regions  40  of the first and second vanes  70 ,  72 . Further, the engagement between the inner platform and the inner end region of the airfoil may or may not be substantially identical to the engagement between the outer platform and the outer end region of the airfoil. 
   During engine operation, a high pressure coolant  82 , such as air, can be supplied to the platforms  52 ,  54 . A portion of the coolant  82  can leak through the cooling gap  80  and enter the turbine gas path  84 . Because the seam  78  is located proximate the airfoil  32 , the coolant leakage can cool the transition region  86  between the airfoil  32  and the platforms  52 ,  54 , particularly when the cooling gap  80  is formed in part by the airfoil  32 . Such cooling benefits can also be enjoyed when the vane  10  includes a platform lip  68 , as shown in  FIG. 7 , so long as the platform lip  68  remains sufficiently close to the airfoil. 
   To further focus the leakage toward the airfoil, one or more seals  88  can be operatively positioned along those portions of the seam  78  formed by the abutting portions of the platforms  52 ,  54  of the first vane  70  and the platforms  52 ,  54  of the second vane  72 . The seals  88  can be any suitable seal, such as flat plate seals, riffle seals, etc. Thus, it will be appreciated that the seals  88  can be used to direct the leakage flow through those portions of the seam  78  that are proximate the airfoil  32 . 
   Aside from the cooling effect, aspects of the invention can result in a number of additional benefits. For example, aspects of the invention can result in a potential increase in engine efficiency as well as component life. Further, the unitary platform and airfoil can facilitate assembly and can reduce the number of unique pieces to install. Further, by providing the platform on one side, less sealing is needed and a more controlled leakage flow can be achieved. 
   The foregoing description is provided in the context of various embodiments of a turbine vane in accordance with aspects of the invention. It will be understood that aspects of the invention can be applied to any of a number of vane configurations. For instance, a vane can include multiple airfoils extending between the inner and outer platform. Aspects of the invention can be applied to such vanes, though not all of the airfoils will benefit from the leakage flow through the seam. Thus, it will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the following claims.