Abstract:
A cooling system for a turbine blade of a turbine engine having multiple serpentine trailing edge cooling channels in parallel. The serpentine cooling channels are positioned proximate to a trailing edge of the turbine blade and facilitate increased heat removal with less cooling fluid flow, thereby resulting in increased cooling system efficiency.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention is directed generally to turbine blades, and more particularly to cooling systems in hollow turbine blades.  
       BACKGROUND  
       [0002]     Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine blade assemblies to these high temperatures. As a result, turbine blades must be made of materials capable of withstanding such high temperatures. In addition, turbine blades often contain cooling systems for prolonging the life of the blades and reducing the likelihood of failure as a result of excessive temperatures.  
         [0003]     Typically, turbine blades are formed from a root portion at one end and an elongated portion forming a blade that extends outwardly from a platform coupled to the root portion. The blade is ordinarily composed of a tip opposite the root section, a leading edge, and a trailing edge. The inner aspects of most turbine blades typically contain an intricate maze of cooling channels forming a cooling system. The cooling channels in the blades receive air from the compressor of the turbine engine and pass the air through the blade. The cooling channels often include multiple flow paths that are designed to maintain all aspects of the turbine blade at a relatively uniform temperature. However, centrifugal forces and air flow at boundary layers often prevent some areas of the turbine blade from being adequately cooled, which results in the formation of localized hot spots.  
         [0004]     Localized hot spots, depending on their location, can reduce the useful life of a turbine blade and can damage a turbine blade to an extent necessitating replacement of the blade. Often, conventional turbine blades develop hot spots in the trailing edge of the blade. While the trailing edge of the turbine blade is not exposed to as harsh of conditions as a leading edge of the blade, the trailing edge requires cooling nonetheless. Many conventional cooling systems in the trailing edge of a turbine blade consist of a plurality of pin fins for increasing the cooling capabilities of the cooling system. Most pin fin cooling systems lack control of the cooling fluid flow through the trailing edge. Instead, the cooling fluids flow with relatively little boundaries. The lack of control of cooling fluid flow necessitates increased cooling fluid flow to insure that all portions of a trailing edge be adequately cooled. Such increased cooling fluid flow negatively affects the efficiency of the turbine blade cooling system. Thus, a need exists for a more efficient trailing edge cooling system.  
       SUMMARY OF THE INVENTION  
       [0005]     This invention relates to a turbine blade cooling system formed from at least one cooling fluid cavity extending into an elongated blade and two or more serpentine trailing edge cooling channels in parallel with each other in the trailing edge of the turbine blade and in communication with the at least one cooling fluid cavity. The serpentine cooling channels in parallel increase heat reduction in the trailing edge region of the blade and reduce the amount of cooling fluid flow needed in the trailing edge region, thereby increasing the efficiency of the turbine blade cooling system.  
         [0006]     The turbine blade may be formed from a generally elongated blade having a leading edge, a trailing edge, a tip section at a first end, a root coupled to the blade at an end generally opposite the first end for supporting the blade and for coupling the blade to a disc, and at least one cavity forming a cooling system in the blade. Two or more serpentine trailing edge cooling channels may be positioned in parallel proximate to the trailing edge of the turbine blade. In at least one embodiment, the turbine blade may include at least one first serpentine trailing edge cooling channel and at least one second serpentine trailing edge cooling channel that are each formed by at least three pass channels positioned in parallel and proximate to the trailing edge of the generally elongated blade for receiving cooling fluids from a cooling fluid source, passing the cooling fluids through the at least one first and second serpentine trailing edge cooling channels, and exhausting the cooling fluids through the trailing edge of the blade. The cooling system is not limited to only having two serpentine trailing edge cooling channels. Rather, the cooling system may have two or more serpentine trailing edge cooling channels, and may include third or fourth serpentine trailing edge cooling channels, or both. The serpentine trailing edge cooling channels may be at least triple pass channels, and in at least one embodiment, may be five pass channels, or a combination of triple and five pass channels.  
         [0007]     The serpentine trailing edge cooling channels may include inlets that are generally orthogonal to a longitudinal axis of a cooling fluid supply channel. The inlets are aligned to facilitate flow of cooling fluids into the serpentine trailing edge cooling channels. The serpentine cooling channels may also include a plurality of trailing edge exhaust orifices for exhausting cooling fluids from the trailing edge of the turbine blade.  
         [0008]     During use, cooling fluids are passed from the root of the blade into one or more cooling fluid cavities in the turbine blade. At least a portion of the cooling fluids, which may be air, is passed into a cooling fluid supply channel. These cooling fluids flow into the serpentine trailing edge cooling channels, where the cooling fluids remove heat from the material forming the turbine blade. Having multiple serpentine cooling channels positioned in parallel and in close proximity to the trailing edge of the blade is beneficial for a number of reasons. For instance, the multiple serpentine cooling channels increase heat removal from the trailing edge of the blade relative to conventional configurations. In addition, the multiple serpentine cooling channels requires less cooling fluid flow than conventional cooling systems, thereby improving the efficiency of the turbine engine.  
         [0009]     An advantage of this invention is that each individual serpentine cooling channel is a modular formation enabling each to be customized. The modular formation provides flexibility in tailoring the airfoil trailing edge cooling scheme based on the airfoil gas side hot gas temperature and hot gas pressure distribution in both chordwise and spanwise directions.  
         [0010]     Another advantage of this invention is that the modular configuration of the trailing edge cooling channels provides flexibility to achieve a desirable blade sectional average metal temperature for a given blade material based on the allowable blade stress level.  
         [0011]     Yet another advantage of this invention is that the modular configuration of the trailing edge cooling channels provides a fail safe mechanism for trailing edge in the event of burn through or erosion at the airfoil trailing edge. The individual serpentine channels forming the modules may prevent trailing edge cooling air over flow, which minimizes the possibility for hot gas ingestion at the other trailing edge serpentine cooling channels. Additionally, if an individual serpentine cooling channel has eroded, the eroded channel will not affect the remaining serpentine trailing edge cooling channels, thereby yielding a robust cooling design.  
         [0012]     Another advantage of this invention is that the serpentine cooling channel configuration incurs higher cooling fluid pressure than conventional pin fin trailing edge cooling systems, thereby yielding a more efficient cooling system because the internal pressure across an airfoil is typically very high.  
         [0013]     These and other embodiments are described in more detail below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The accompanying drawings, which are incorporated in and form a part of the specification, illustrate embodiments of the presently disclosed invention and, together with the description, disclose the principles of the invention.  
         [0015]      FIG. 1  is a perspective view of a turbine blade having features according to the instant invention.  
         [0016]      FIG. 2  is cross-sectional view, referred to as a filleted view, of the turbine blade shown in  FIG. 1  taken along line  2 - 2 .  
         [0017]      FIG. 3  is cross-sectional view, of an alternative embodiment of the turbine blade shown in  FIG. 1  taken from the same perspective as line  2 - 2 .  
         [0018]      FIG. 4  is a cross-sectional view of an alternative embodiment of the turbine blade shown in  FIG. 1  taken from the same perspective as line  2 - 2 .  
         [0019]      FIG. 5  is a cross-sectional view of an alternative embodiment of the turbine blade shown in  FIG. 1  taken from the same perspective as line  2 - 2 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     As shown in  FIGS. 1-5 , this invention is directed to a turbine blade cooling system  10  for turbine blades  12  used in turbine engines. In particular, the turbine blade cooling system  10  is directed to a cooling system  10  located in a cavity  14 , as shown in  FIGS. 2 and 3 , positioned between two or more walls  28  forming a housing  16  of the turbine blade  12 . The cooling system  10  may include two or more serpentine trailing edge cooling channels  18  positioned in parallel with each other in the cooling system, as shown in  FIGS. 2-5 , and in close proximity to a trailing edge  20  of the blade  12  for increasing the heat removal from the blade  12  and reducing the required cooling fluid flow to achieve adequate cooling, thereby increasing the effectiveness of the cooling system  10 .  
         [0021]     As shown in  FIG. 1 , the turbine blade  12  may be formed from a generally elongated blade  22  coupled to a root  24  at a platform  26 . Blade  22  may have an outer wall  28  adapted for use, for example, in a first stage of an axial flow turbine engine. Outer wall  28  may form a generally concave shaped portion forming pressure side  30  and may form a generally convex shaped portion forming suction side  32 . The cavity  14 , as shown in  FIGS. 2 and 3 , may be positioned in inner aspects of the blade  22  for directing one or more gases, which may include air received from a compressor (not shown), through the blade  22  and out one or more orifices  34  in the blade  22  to reduce the temperature of the blade  22 . As shown in  FIG. 1 , the orifices  34  may be positioned in a leading edge  36 , tip  48 , or outer wall  28 , or any combination thereof, and have various configurations. The cavity  14  may be arranged in various configurations and is not limited to a particular flow path.  
         [0022]     The cooling system  10 , as shown in  FIGS. 2 and 3 , may also include serpentine trailing edge cooling channels  18  for removing heat from the blade  22  proximate to the trailing edge  20 . In at least one embodiment, the cooling system  10  may include two or more serpentine trailing edge cooling channels  18 . The serpentine cooling channels  18  may extend generally parallel to a longitudinal axis  37  of the elongated blade  22 . As shown in  FIG. 2 , the cooling system  10  may include a first serpentine trailing edge cooling channel  38 , a second serpentine trailing edge cooling channel  40 , and a third serpentine trailing edge cooling channel  42 . In another embodiment, as shown in  FIG. 3 , the cooling system  10  may include a fourth serpentine trailing edge cooling channel  43  in addition to channels  39 ,  40 , and  42 . The first and second serpentine trailing edge cooling channels  38 ,  40  may be separated from each other by a rib  44 . The second and third serpentine trailing edge cooling channels  40 ,  42  may be separated from each other by a rib  46 . The third and fourth serpentine trailing edge cooling channels  42 ,  43  may be separated from each other by a rib  47 . As shown in  FIG. 2 , the first serpentine trailing edge cooling channel  38  may be positioned proximate to a tip  48  of the blade  22 , and the third serpentine trailing edge cooling channel  42  may be positioned proximate to the root  24  of the blade  22 . The first, second, third and fourth serpentine trailing edge cooling channels  38 ,  40 ,  42  and  43  may be positioned in close proximity to the trailing edge  20  of the blade  22  so that cooling fluids flowing through the channels  38 ,  40 ,  42  and  43  may remove heat from the blade  22  proximate to the trailing edge  20 . The first, second, third, and fourth serpentine trailing edge cooling channels  38 ,  40 ,  42  and  43  may be positioned in parallel in the cooling fluid flow pattern.  
         [0023]     The first, second, third, and fourth serpentine trailing edge cooling channels  38 ,  40 ,  42  and  43  may be in communication with one or more trailing edge exhaust orifices  50  for exhausting cooling fluids from the cooling channels  38 ,  40 ,  42  and  43 . In one embodiment, the first, second, third, and fourth serpentine trailing edge cooling channels  38 ,  40 ,  42  and  43  may each share a single trailing edge exhaust orifice  50 , may each include an independent trailing edge exhaust orifice  50 , or may each be in communication with a plurality of trailing edge exhaust orifices  50 . The exhaust orifices  50  may be sized based on anticipated flow rate, heat load in the trailing edge  20 , cooling fluid pressure, and other factors.  
         [0024]     The first, second, and third serpentine trailing edge cooling channels  38 ,  40 ,  42 , and  43  may also each include inlets  52 ,  54 ,  56  and  57 , respectively, for passing cooling fluids into the channels  38 ,  40 ,  42  and  43 . The inlets  52 ,  54 ,  56  and  57  may have any size and configuration necessary to deliver an adequate cooling fluid supply to the channels  38 ,  40 ,  42  and  43 . In at least one embodiment, the inlets  52 ,  54 ,  56  and  57  may be generally orthogonal to a longitudinal axis  58  of a cooling fluid supply channel  60 .  
         [0025]     Each trailing edge cooling channel  38 ,  40 ,  42 , and  43  may be formed from three pass or five pass serpentine channels, or a combination of both. Other embodiments may use serpentine channels having other numbers of passes. In at least one embodiment with three serpentine channels, as shown in  FIG. 4 , cooling channels  38  and  42  may be formed from triple pass serpentine cooling channels to better match the lower gas temperature profile and cooling channel  40  may be formed from a five pass serpentine cooling channel to achieve higher local cooling effectiveness. Similarly, in another embodiment with four serpentine channels, as shown in  FIG. 5 , cooling channels  38  and  43  may be formed from triple pass serpentine cooling channels to better match the lower gas temperature profile and cooling channels  40  and  42  may be formed from a five pass serpentine cooling channel to achieve higher local cooling effectiveness.  
         [0026]     During operation, cooling fluids, which may be, but are not limited to, air, flow into the cooling system  10  from the root  24 . At least a portion of the cooling fluids flow into the cavity  14  and into the cooling fluid supply channel  60 . At least some of the cooling fluids flow through the inlets  52 ,  54 ,  56  and  57  and into the first, second, third and fourth serpentine trailing edge cooling channels  38 ,  40 ,  42  and  43 . The cooling fluids enter the channels  38 ,  40 ,  42  and  43  in parallel and remove heat from the material forming the blade  22  proximate to the trailing edge  20 . The cooling fluids flow through the serpentine trailing edge cooling channels  38 ,  40 ,  42  and  43  where the cooling fluids cool the material forming the blade  22 . The cooling fluids are then exhausted through the trailing edge exhaust orifices  50  and out of the blade  22 .  
         [0027]     The foregoing is provided for purposes of illustrating, explaining, and describing embodiments of this invention. Modifications and adaptations to these embodiments will be apparent to those skilled in the art and may be made without departing from the scope or spirit of this invention.