Abstract:
A turbine blade for a turbine engine having a cooling system in the turbine blade formed from at least one cooling channel. The cooling system may include one or more protrusions positioned in the cooling channel and including one or more vortex breakers along the length of the protrusion. The vortex breakers disrupt vortices formed downstream of the protrusions to increase heat transfer enhancement effect of the protrusions. The cooling channels of the cooling system may include a plurality of protrusions whose configuration is based upon the cooling requirements of the blade in which the cooling system is installed.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention is directed generally to turbine blades, and more particularly to the components of cooling systems located 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 at an opposite end of the turbine blade. 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. 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.  
         [0004]     Cooling channels forming a cooling system in a turbine blade often include a plurality of trip strips protruding from the walls of the channels. As cooling air flows through the cooling channel, a boundary layer is formed. The trip strips create vortices in cooling air flowing through the channel thereby increasing the effectiveness of the cooling channels. The trip strips are generally aligned orthogonal to the air flow through the cooling channel. However, in some conventional cooling systems, the trip strips may be aligned at an angle to the flow of cooling air. As cooling air passes over the angled trip strips, vortices are created immediately downstream of the trip strip and move along the trip strip from an end furthest upstream toward the downstream end of the trip strip. As the vortices propagate along the length of the trip strip, the boundary layer becomes progressively more disturbed or thickened, and consequently the tripping of the boundary layer becomes progressively less effective. The net result of the thickening or growth of the boundary layer in significantly reduced heat transfer enhancement that is typically associated with thin vortices formed by trip strips. Thus, a need exists for a cooling channels capable of increasing the heat transfer enhancement action of the trip strips.  
       SUMMARY OF THE INVENTION  
       [0005]     This invention relates to a turbine blade cooling system formed from at least one cooling channel containing a protrusion, otherwise referred to as a trip strip or turbulator, having a vortex breaker positioned on the protrusion for increasing the cooling capacity of the cooling channel. The cooling channel may be positioned in a generally elongated turbine blade having a leading edge, a trailing edge, a tip at a first end, and 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. The turbine blade may include at least one cavity forming the cooling system in the turbine blade. Interior aspects of the cooling channel may include a protrusion positioned at an angle greater than zero relative to a general direction of cooling fluid flow through the cooling system. The vortex breaker may have a width and a height that is greater than a width of the protrusion. In at least one embodiment, the vortex breaker may be generally oval shaped.  
         [0006]     The cooling channels forming the cooling system may include one or a plurality of protrusions along the length of the channels. The protrusions may be placed generally parallel to each other and nonparallel to the flow of cooling fluids through the cooling channels. In other embodiments, the protrusions may be nonparallel relative to each other. At least some, if not all, of the protrusions include one or more vortex breakers for disrupting the vortices formed downstream of the protrusions as the vortices flow from an intersection between the protrusion and a side wall forming the cooling channel along the protrusion. The vortex breakers extend higher than the protrusion but, in at least one embodiment, do not contact an inner surface of the cooling channel opposite the inner surface so as to not increase the resistance to cooling fluid flow.  
         [0007]     During operation of a turbine engine, cooling fluids are passed through a cooling system. More specifically, cooling fluids are passed into cooling channels forming the cooling system. As the cooling fluids flow through the channels, the cooling fluids encounter at least one protrusion. As the cooling fluids encounter a protrusion, a vortex is formed proximate to a downstream side of the protrusion. The vortex moves generally along the protrusion from an intersection between the protrusion and a side wall forming the cooling channel. As the cooling air flows over a vortex beaker, a new boundary layer of cooling fluids is formed. The newly formed boundary layer created by the vortex breaker shears the vortices developed by the upstream portion of the protrusion. The shearing action caused by the vortex breaker causes the formation of an undisturbed boundary layer for the trailing edge portion of the protrusion. In this fashion, the vortex breaker has essentially created a second leading edge to the protrusion. The leading edge created by the vortex breaker generates a high heat transfer coefficient and corresponding improvement in overall cooling performance.  
         [0008]     An advantage of this invention is that the vortex breaker increases the efficiency of the cooling system without significantly increasing the pressure or reducing the flow rate of cooling fluids through the system. Instead, the internal heat transfer enhancement level is increased due to the formation of a second leading edge and new boundary layer caused by the vortex breakers.  
         [0009]     Another advantage of this invention is that multiple vortex breakers at variable angles of protrusions enable the cooling pattern of a cooling channel to be tailored to specific heat loads encountered in a different turbine blades.  
         [0010]     Still another advantage of this invention is that this invention provides higher overall airfoil internal convective cooling enhancement with a reduction in cooling flow demand, which results in improved turbine engine performance.  
         [0011]     These and other embodiments are described in more detail below. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     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.  
         [0013]      FIG. 1  is a perspective view of a turbine blade having features according to the instant invention.  
         [0014]      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 .  
         [0015]      FIG. 3  is a partial cross-sectional view of the turbine blade shown in  FIG. 2  taken along line  3 - 3 .  
         [0016]      FIG. 4  is a cross-sectional view of the turbine blade shown in  FIG. 3  taken along line  4 - 4 .  
         [0017]      FIG. 5  is a cross-sectional view of an alternative embodiment of the invention.  
         [0018]      FIG. 6  is a cross-sectional view of another alternative embodiment of the invention.  
         [0019]      FIG. 7  is a cross-sectional view of still another alternative embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     As shown in  FIGS. 1-7 , 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  FIG. 2 , positioned between two or more walls forming a housing  24  of the turbine blade  12 . As shown in  FIG. 1 , the turbine blade  12  may be formed from a generally elongated blade  20  coupled to the root  16  at the platform  18 . Blade  20  may have an outer wall  22  adapted for use, for example, in a first stage of an axial flow turbine engine. Outer wall  22  may be formed from a housing  24  having a generally concave shaped portion forming pressure side  26  and may have a generally convex shaped portion forming suction side  28 .  
         [0021]     The cavity  14 , as shown in  FIG. 2 , may be positioned in inner aspects of the blade  20  for directing one or more gases, which may include air received from a compressor (not shown), through the blade  20  and out one or more orifices  30  in the blade  20  to reduce the temperature of the blade  20 . As shown in  FIG. 1 , the orifices  30  may be positioned in a tip  32 , a leading edge  34 , or a trailing edge  36 , or any combination thereof, and have various configurations. The cavity  14  may be arranged in various configurations, and the cooling system  10  is not limited to a particular flow path.  
         [0022]     The cooling system  10 , as shown in  FIG. 2 , may be formed from one or more cooling channels  38  for directing cooling fluids the turbine blade  12  to remove excess heat to prevent premature failure. The cooling channels  38  may include one or a plurality of protrusions  40 , otherwise referred to as trip strips or turbulators, as shown in  FIG. 2  and more specifically in  FIGS. 3 and 5 - 7 . The protrusions  40  may extend out from an inner surface  42  forming the cooling channel  38 . During operation, the protrusions  40  disrupt the flow of cooling fluids through the turbine blade  12  and thereby enhance heat transfer in the cooling channels  38 .  
         [0023]     In at least one embodiment, the protrusions  40  may include a vortex breaker  44  positioned along the protrusion  40  for disrupting the flow of a vortex formed along the length of the protrusion  40 . By disrupting the vortex of cooling fluids along the protrusion  40 , the amount of heat transfer increases as the vortex created along the protrusion  40  and flowing from one channel wall  46  to another wall  48  is broken. By breaking the vortex, the thickened boundary layer is dissipated and a new boundary layer is formed in a newly formed vortex that forms downstream of the vortex breaker. Thus, the vortices forming downstream of the vortex breaker  44  along the protrusion  40  to which a vortex breaker  44  is attached have a thinner boundary layer than the vortex upstream of the vortex breaker  44  and thereby, have increased heat transfer enhancement relative to the vortex breaker  44  protrusions  40  without vortex breakers  44 .  
         [0024]     As shown in  FIG. 3 , the vortex breaker  44  may divide a protrusion  40  into an upstream section  50  and a downstream section  52 . The upstream and downstream sections  50 ,  52  may extend generally along a longitudinal axis  54 . The vortex breaker  44  may be positioned at a midpoint  56  along the protrusion  40 . In other embodiments, the vortex breaker  44  may be positioned at other locations along a protrusion  40 . In another embodiment, the downstream section  52  may form an angle α between a longitudinal axis  54  by extending in an upstream direction, as shown in  FIG. 5 , or extending downstream, as shown in  FIG. 6 . Angle α may be any amount between about five degrees and about 90 degrees. Thus, the downstream section  52  is nonparallel with the upstream section  50 .  
         [0025]     The vortex breaker  44  may have any shape capable of disrupting the cooling fluid vortex flowing along the protrusion  40 . In at least one embodiment, as shown in  FIGS. 3-7 , the vortex breaker  44  may have a generally oval shape. The vortex breaker  44  may also be sized such that the width of the vortex breaker  44  is greater than a width of the at least one first protrusion  40  and a height of the vortex breaker  44  is greater than a width of the at least one first protrusion  40 . In at least one embodiment, the width of the vortex breaker  44  may be about three times the width of the protrusion  40 . The vortex breaker  44  may also have a height that is about three times the width of the protrusion  40 , as shown in  FIG. 4 . The height of the cooling channel  38  in which the vortex breaker  44  is positioned may greater than a height of the vortex breaker  44  such that the vortex breaker  44  does not contact the opposing surface forming the cooling channel  38 .  
         [0026]     In some embodiments, more than one vortex breaker  44  may be included on a single protrusion  40 , as shown in  FIG. 7 . For instance, two vortex breakers  44  may be positioned on a protrusion  40 . The vortex breakers  44  may divide a protrusion  40  into an upstream section  58 , a midsection  60 , and downstream section  62 . The embodiment may be configured such that the midsection  60  is positioned relative to the upstream section  58  at a first angle  64 , and the downstream section  62  is positioned at a second angle  66 . The first angle  64  and second angles  66  may be between about five degrees and about 60 degrees. As shown in  FIG. 7 , the first angle  64  may extend from a longitudinal axis  68  of the upstream section  58  upstream. Likewise, the second angle  66  may extend from a longitudinal axis  70  of the midsection  60  upstream. First and second angles  64 ,  66  may or may not have equal values. In at least one embodiment, the downstream section  62  and the upstream section  58  may be substantially mirror images of each other, and the midsection  60  may be substantially orthogonal to the walls forming the cooling channel  38 . The midsection  60  may also be positioned generally orthogonal to the flow of cooling fluids through the cooling channels  38 .  
         [0027]     During operation of the turbine engine, cooling fluids, which are often formed from air, flow through the cooling channels  38  forming the cooling system  10 . The cooling fluids increase in temperature, thereby reducing the temperature of the turbine blade through which the cooling fluids flow. As cooling fluids flow through the cooling channel  38  and strike an upstream section  50  of the protrusion  40 , the cooling fluid forms a vortex that flows along the downstream side of the protrusion  40 , as shown in  FIG. 3 . The vortex thickens, or grows, as it moves along the protrusion  40  toward the vortex breaker  44 . As the vortex grows, the heat transfer enhancement due to the vortex is reduced. The vortex dissipates when the vortex contacts the vortex breaker  44 . Cooling fluids passing over the downstream section  52  of the protrusion  40  just downstream of the vortex break  44  create another vortex that moves along the protrusion  40  toward a wall  48  forming the cooling channel  38  where the vortex dissipates, and the cooling fluids forming the vortex flow downstream. By placing the vortex breaker  44  on the protrusion  40 , the thickened vortex is dissipated and another vortex having a larger heat transfer enhancement relative to the upstream vortex is formed.  
         [0028]     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.