Abstract:
A cooled fluid flow component for a combustion engine which employs internal impingement and exterior surface film cooling is disclosed. The fluid flow component has improved tolerance to assembly and manufacturing variations. The fluid flow component includes at least one interior cavity having an associated impingement sleeve. An impingement annulus surrounding the impingement sleeve is divided into more than one region, with each region forced to have a pressure equal, pressure, with the pressure induced being sufficient to provide adequate backflow margin. The external cooling holes are shaped to address possible overflow tendencies, and the impingement holes are adapted to reduce or eliminate possible losses of impingement cooling effectiveness.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to the field of internal to combustion engines and, more particularly, to a flow guide component having improved tolerance to assembly and manufacturing variations.  
         BACKGROUND OF THE INVENTION  
         [0002]    Combustion engines are machines that convert chemical energy stored in fuel into mechanical energy useful for generating electricity, producing thrust, or otherwise doing work. These engines typically include several cooperative sections that contribute in some way to the energy conversion process. In gas turbine engines, air discharged from a compressor section and fuel introduced from a fuel supply are mixed together and burned in a combustion section. The products of combustion are harnessed and directed through a turbine section, where they expand and turn a central rotor shaft. The rotor shaft may, in turn, be linked to devices such as an electric generator to produce electricity.  
           [0003]    To increase efficiency, engines are typically operated near the limits of the engine components. For example, to maximize the amount of energy available for conversion into electricity, the products of combustion (also referred to as the working gas or working fluid) often exit the combustion section at high temperature. This elevated temperature generates a large amount of potential energy, but also places a great deal of stress on the downstream fluid guide components, such as the blades and vanes of the turbine section. In an effort to help these components withstand this temperature these blades and vanes are often cooled.  
           [0004]    In fluid guide components with an internal impingement and external surface (leading edge showerhead and side film) cooling design, a basic concern is the maintenance sufficient backflow margin. This means ensuring that the pressure supplying the showerhead surface holes is maintained above the external static pressure in the leading edge region during all operating ranges. This backflow requirement must be met while simultaneously ensuring that the fluid guide component side walls are also sufficiently cooled. Traditionally, a perforated impingement tube or insert in conjunction with dams or other sealing partitions or is used to accomplish this. The dams help isolate the leading edge cooling region and associated cooling holes from influences which might jeopardize the backflow margin, including manufacturing imperfections or assembly misalignment within the side wall cooling regions, fluctuations in external static pressure, and variation induced by permitted manufacturing tolerances, including cooling hole size and location. This isolation is beneficial because the cooling holes in the leading edge and side regions are typically fed from the same cooling cavity. The dams also create flow-wise separated regions so that the desired impingement pressure ratios can be generated to provide the necessary internal cooling along the fluid guide component sidewalls. The dams also provide a means of positioning the insert. Accordingly, sealing dams provide performance and assembly benefits, in some cases. Unfortunately, sealing dams often do not perform as expected.  
           [0005]    In practice, manufacturing tolerances often result in the dams being incorrectly positioned or improperly sized. Also, impingement inserts are often installed during a so-called “blind” assembly, which is difficult to observe directly. As a result, it is difficult to ensure that the impingement inserts are correctly positioned. If an impingement tube is installed or manufactured incorrectly, associated impingement holes may be blocked or leakage around the sealing dams may occur. Misalignment or other incorrect insert assembly can significantly reduce the available impingement cooling, with the further result of jeopardizing the backflow margin of the leading edge cooling region. Failures of this type may result in reduced life of the fluid guide component or even complete failure of the component.  
           [0006]    Therefore, there remains a need in this art for a fluid guide component that meets cooling requirements while remaining insensitive to the presence of sealing dams or positioning members and minimizing the necessary cooling flow requirements for a given engine performance. The component should include hollow portions or cavities having impingement hole arrays sized so that substantially-uniform pressure is obtained on the downstream side of the impingement insert on all sides of associated positioning members or sealing dams. This pressure obtained within each cavity should meet the minimum back flow requirements for the highest external pressure encountered by the given cavity. The component should also address possible losses in impingement cooling effectiveness, as well as issues related to overflowing of the external cooling holes.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is a flow guide component having improved tolerance to assembly and manufacturing variations. The guide component includes features that reduce or eliminate sensitivity to the presence of the insert seals, dams, or positioning members, while minimizing the necessary cooling flow requirements for a given engine performance.  
           [0008]    Accordingly, it is an object of the present invention to provide a fluid guide component for a combustion engine that ensures substantially-uniform pressure is obtained on the downstream side of an impingement insert on all sides of the associated positioning members or sealing dams.  
           [0009]    It is a further object of the present invention to provide a fluid guide component for a combustion engine that address possible losses in impingement cooling effectiveness.  
           [0010]    It is an additional object of the present invention to provide a fluid guide component for a combustion engine that addresses possible overflowing of the external cooling holes.  
           [0011]    Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0012]    [0012]FIG. 1 is an isometric view of the fluid guide component of the present invention;  
         [0013]    [0013]FIG. 2 is a cross-section end view of the fluid guide component shown in FIG. 1, taken along cutting plane II-II′ therein;  
         [0014]    [0014]FIG. 3 is an alternate isometric view of an impingement sleeve used in a forward hollow portion of the present invention; and  
         [0015]    [0015]FIG. 4 is an alternate isometric view of an impingement sleeve used in a middle hollow portion of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    Reference is made to the Figures, generally, in which a fluid guide component  10  according to the present invention is shown. By way of overview, the component  10  is internally cooled and includes a body member  12  having forward and middle hollow portions  14 , 16 ; an impingement sleeve  17 , 18  is mounted in each of the hollow portions. The impingement sleeves  17 , 18  are spaced apart from the inner surface  19 , 20  of the corresponding hollow portion  14 , 16 , each forming an impingement annulus  21 , 22  which surrounds the corresponding impingement sleeve. In each impingement annulus  21 , 22 , first and second pairs of partition elements  23 , 25  and  24 , 26  divide the annulus into two distinct regions  27 , 29  and  28 , 30 . Additionally, each impingement sleeve  17 , 18  includes two groups of impingement holes or ports  31 , 33  and  32 , 34  that fluidly connect the corresponding first and second impingement regions  27 , 29  and  28 , 30  with a flow channel  35 , 36  located within the corresponding impingement sleeve  17 , 18 . The flow channels  35 , 36  are, in turn, adapted for connection to a source of cooling fluid, such as air provided by an upstream source, such as a compressor (not shown) or combustor (not shown). Similarly, groups of surface cooling holes  37 , 39  and  38 , 40  are disposed within corresponding exterior cooling regions  41 , 43  and  42 , 44  associated with each hollow portion  14 , 16 . During operation, each of the forward exterior cooling regions  41 , 43  experience substantially-different pressures, with each of the middle exterior cooling regions  42 , 44  also encountering substantially-different pressures. In this application, the term “substantially-different pressures” refers to pressures which differ by about 10% or greater. The present invention is suited, for example for use in environments in which the pressure in the forward first exterior cooling regions  41 , 42  is about 115% of the pressure in the forward second exterior cooling regions  43 , 44 ; the present invention is also suited for pressure variations of about 50%, such as between middle first exterior cooling regions  42  and middle second exterior cooling regions  44 .  
         [0017]    In keeping with the objects of the invention, and as will be described more fully below, the groups of impingement holes  31 , 33  and  32 , 34  are adapted to ensure that substantially-equal pressure is obtained within each impingement region  27 , 29  and  28 , 30 , even though this means that each corresponding second impingement region  29 , 30  will receive more pressure than is typically required to provide surface cooling of those regions and that the impingement cooling effectiveness in each hollow portion  14 , 16  may be reduced. This arrangement ensures that a sufficient backflow margin is maintained, regardless of variations in the impingement sleeve  18  manufacture or misalignment of sleeve during insertion into the hollow portions  14 , 16 . Tendencies for overflow of the second groups of surface cooling holes  37 , 38 , as well as measures to improve impingement cooling are advantageously provided, as discussed below. The fluid guide component  10  according to the present invention will now be described in detail.  
         [0018]    With particular reference to FIGS. 1 and 2, the fluid guide component of the present invention  10  is a vane for use in an industrial combustion turbine engine (not shown). The body member  12  is elongated and substantially-airfoil shaped. The body member  12  includes a leading edge region  46 , a pressure side region  48 , and a suction side region  50 . The body member  12  includes forward and middle hollow portions  14 , 16  defined by cavity barriers or ribs  51 , 52  which extend across the interior of the body member, connecting the body member pressure side region  48  and suction side region  50 . It is noted that the body member  12  need not include two hollow portions  14 , 16 , and may include fewer, or more, hollow portions if desired.  
         [0019]    As seen with continued reference to FIGS. 1 and 2, the forward hollow portion  14  includes an impingement sleeve  17  spaced apart from the hollow portion inner surface  19 . A set of partition elements or dams  23 , 25 , extend between the hollow portion inner surface  19  and the impingement sleeve  18 . These partition elements  23 , 25  divide the forward impingement annulus, which is located between the forward impingement sleeve  17  and forward hollow portion inner surface  19 , into two impingement regions  27 , 29 .  
         [0020]    With particular reference to FIG. 2, the forward partition elements  23 , 25  are substantially aligned with the edges of the body portion leading edge region  46 . With this arrangement, the forward first impingement region  27  is substantially coextensive with the body portion leading edge region  46 . Accordingly, the forward second impingement region  29  extends around the forward impingement sleeve  17 , except for the region bounded by the forward partition elements  23 , 25 . With this arrangement, the forward first impingement region  27  accounts for about 5% to 10% of the total volume of the forward impingement annulus  21 . It is noted that several pairs of dams may be used if more than two impingement regions are desired. It is also noted that the partition elements  23 , 25  need not seal the impingement regions from each other; stand-offs, dimples or other suitable non-sealing members may also be used.  
         [0021]    With particular reference to FIG. 3, the forward impingement sleeve  17  includes two groups of impingement holes or ports  31 , 33 , with each group being associated with one of the forward impingement regions  27 , 29  described above. The forward first group of impingement ports  31  fluidly connects the forward first impingement  27  region with the forward flow channel  35 , while the forward second group of impingement ports  33  fluidly connects the forward second impingement  29  region with the forward flow channel. In keeping with the objects of the invention, the pressure within the forward first impingement region  27  is forced to be the same as the pressure within the forward second impingement region  29 . In one embodiment, this pressure equality is ensured by setting the flow per unit area within the forward first group of impingement ports  31  to be substantially equivalent to the flow per unit area within the forward second group of impingement ports  33 . The pressure produced in both impingement regions  27 , 29  is sufficient to maintain the backflow margin required for proper surface cooling of the leading edge region  46 . This arrangement advantageously ensures that gaps between the forward set of partition elements  23 , 25  and the forward impingement sleeve  17  do not interfere with surface cooling of the body member  12 . Although these pressures vary, one appropriate backflow margin range is between about 2% and 5%. An appropriate range for forward impingement annulus pressure ratio would be about 25% to 33% of the backflow-margin. In one embodiment, the pressure adjacent the forward first exterior cooling holes  37  is within the range of about 1585-1800 Kpa, the pressure adjacent the forward second exterior cooling holes  39  is within the range of about 1200-1485 Kpa, and the pressure within the forward flow channel is within the range of about 1585-1800 KPa.  
         [0022]    With reference again to FIG. 2, the forward first set of exterior cooling holes  37  are located within the body portion leading edge region  46  and are exposed to a pressure in the range of no more than about 98% of the pressure within the first flow channel  35 . The forward first set of exterior cooling holes  37  have a cylindrical cross section and have a diameter in the range of about 0.5 mm to about 1.0 mm. The forward second set of exterior cooling holes  39  are located within the body portion suction side region  50  and are exposed to pressures in a range that is about 10% to about 40% below the pressures experienced by the holes  37  in the first exterior cooling region  41 . The forward second set of exterior cooling holes  39  have a cylindrical region  53  and a flared portion  55 . The cylindrical  53  portions have a diameter in the range of about 0.5 mm to about 1 mm. The flared portion  55  is characterized as being stretched or extended in the flow-wise direction, the radially-upward direction, and the radially-downward direction. With this arrangement, the forward sets of exterior cooling holes  37 , 39  cooperatively provide adequate film cooling of the body member  12 , while the second set of holes is particularly suited for reducing the flow which exits those holes. In keeping with the objects of the present arrangement, this combination advantageously addresses the tendency for the higher-than-required pressure within the forward second impingement region  29  to introduce above-optimum flow rates and associated engine performance issues. It is noted that the forward second exterior cooling region  43  and the associated cooling holes  39  need not be in the suction side region  50 ; they may be located elsewhere, including the pressure side region  48 . The first and second groups of exterior cooling holes  37 , 39  need not be uniform and each group may include combinations of round and flared cross-sections.  
         [0023]    In order to maximize impingement cooling effectiveness within the forward impingement annulus  21 , the forward groups of impingement ports are adapted to induce a flow per unit area sufficient to produce effective impingement cooling. For example, each of the forward first group of impingement ports  31  would have a flow within the range of about 0.06-0.13 kg/s and an area within the range of about 100-250 mm 2  If the ports  31  were circular, each would have a diameter of approximately 0.8 mm to about 1.6 mm. The forward second group of impingement ports  33  would have a flow within the range of about 0.21-0.28 kg/s and an area within the range of about 350-500 mm 2 . If the ports  33  were circular, each would have a diameter of approximately 0.8 mm to about 1.6 mm.  
         [0024]    As seen with continued reference to FIGS. 1 and 2, the middle hollow portion  16  includes an impingement sleeve  18  spaced apart from the hollow portion inner surface  20 . A set of partition elements or dams  24 , 26 , extend between the hollow portion inner surface  20  and the impingement sleeve  18 . These partition elements  24 , 26  divide the middle impingement annulus  22 , which is located between the middle impingement sleeve  18  and middle hollow portion inner surface  20 , into two impingement regions  28 , 30 .  
         [0025]    With particular reference to FIG. 2, the middle partition elements  24 , 26  extend from the cavity barriers  51 , 52  to the impingement sleeve  18 . With this arrangement, the middle first impingement region  28  is associated with the body portion pressure side region  48 . The middle second impingement region  30  is, in turn, associated with the body portion suction side region  50 . With this arrangement, the middle first impingement region  28  accounts for approximately 50% of the total volume of the middle impingement annulus  22 . It is noted that several pairs of dams may be used if more than two impingement regions are desired. It is also noted that the partition elements  24 , 26  need not seal the impingement regions from each other; stand-offs, dimples or other suitable non-sealing members may also be used.  
         [0026]    With particular reference to FIG. 4, the middle impingement sleeve  18  includes two groups of impingement holes or ports  32 , 34 , with each group being associated with one of the middle impingement regions  28 , 30  described above. The middle first group of impingement ports  32  fluidly connects the middle first impingement  28  region with the middle flow channel  36 , while the middle second group of impingement ports  34  fluidly connects the middle second impingement  30  region with the middle flow channel. In keeping with the objects of the invention, the pressure within the middle first impingement region  28  is forced to be the same as the pressure within the middle second impingement region  30 . In one embodiment, this pressure equality is ensured by setting the flow per unit area within the middle first group of impingement ports  32  to be substantially equivalent to the flow per unit area within the middle first group of impingement ports  34 . The pressure produced in both impingement regions  28 , 30  is sufficient to maintain the backflow margin required for proper surface cooling of the body portion  12 . This arrangement advantageously ensures that gaps between the middle set of partition elements  24 , 26  and the middle impingement sleeve  18  do not interfere with surface cooling of the body member  12 . Although these pressures vary, appropriate associated backflow margins are within the range of about 3% to about 7% of the external pressure in this region. In one embodiment, the pressure adjacent the middle first exterior cooling holes  37  is within the range of about 1450-1650 KPa, the pressure adjacent the middle second exterior cooling holes  39  is within the range of about 860-1210 KPa, and the pressure within the middle flow channel is within the range of about 1585-1800 KPa.  
         [0027]    With reference again to FIG. 2, the middle first set of exterior cooling holes  38  are located within the body portion pressure side region  48  and are exposed to a pressure in the range of about 97% of the pressure within the middle first impingement region  28 . The middle first set of exterior cooling holes  38  have a cylindrical portion  58  and a flared portion  60 . The cylindrical portions  58  have a diameter in the range of about 0.5 mm to about 1.0 mm. The flared portion  60  is characterized as being stretched or extended in the flow-wise direction, the radially-upward direction, and the radially-downward direction. The middle second set of exterior cooling holes  40  are located within the body portion suction side region  50  and are exposed to pressures in a range that is about 40% to about 60% below the pressures experienced by the holes  38  in the first exterior cooling region  42 . The middle second set of exterior cooling holes  40  have a cylindrical region and a flared portion. The cylindrical portions have a diameter in the range of about 0.5 mm to about 1.0 mm. The flared portion is characterized as being stretched or extended in the flow-wise direction, the radially-upward direction, and the radially-downward direction. With this arrangement, the middle sets of exterior cooling holes  38 , 40  provide adequate film cooling of the body member  12 , while reducing the flow which exits those holes. In keeping with the objects of the present arrangement, this combination advantageously addresses the tendency for the higher-than-required pressure within the middle second impingement region  30  to introduce above-optimum flow rates and associated engine performance issues. It is noted that the middle first and second groups of exterior cooling holes  38 , 40  need not be uniform and each group may include combinations of round and flared cross-sections.  
         [0028]    In order to maximize impingement cooling effectiveness within the middle impingement annulus  22 , the middle groups of impingement ports are adapted to induce a flow per unit area sufficient to produce effective impingement cooling. For example, each of the middle first group of impingement ports  32  would have a flow of about 0.04-0.08 kg/s and an area in the range of 60-100 mm 2 . The middle second group of impingement ports  34  would have a flow of about 0.04-0.08 kg/s and an area in the range of about 60-100 mm 2 .  
         [0029]    It is to be understood that while certain forms of the invention have been illustrated and described, it is not to be limited to the specific forms or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various, including modifications, rearrangements and substitutions, may be made without departing from the scope of this invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification. The scope if the invention is defined by the claims appended hereto.