Patent Publication Number: US-2013236329-A1

Title: Rotor blade with one or more side wall cooling circuits

Description:
This invention was made with government support under Contract No. F33615-03-D-2354-0009 awarded by the United States Air Force. The government may have certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This disclosure relates generally to gas turbine engines and, more particularly, to a rotor blade for a gas turbine engine with one or more side wall cooling circuits. 
     2. Background Information 
     Turbine blades within a gas turbine engine are typically exposed to relatively high heat loads, which may cause oxidation, creep and/or thermal mechanical fatigue within material of the blades. Some turbine blades therefore include cooling passages to film cool exterior surfaces of the blade. The cooling passages typically extend from a main cavity, which is defined between a pressure side wall and a suction side wall, to an exterior surface of the blade. There is a need in the art, however, for improved blade cooling systems to mitigate ever increasing heat loads. 
     SUMMARY OF THE DISCLOSURE 
     According to a first aspect of the invention, a rotor blade for a gas turbine engine includes an airfoil and a cooling microcircuit. The airfoil includes a first (e.g., pressure or suction) side wall, a second (e.g., suction or pressure) side wall and a tip endwall, where the first side wall and the second side wall extend to and cooperate to form the tip endwall, defining a main cavity between the first side wall and the second side wall. The cooling microcircuit includes a microcircuit cavity, an inlet, a side wall outlet and a tip outlet. The microcircuit cavity is embedded within the first side wall, and the inlet extends from the main cavity to the microcircuit cavity. The side wall outlet extends from the microcircuit cavity to an exterior first side surface of the airfoil. The tip outlet extends from the microcircuit cavity to an exterior tip surface of the airfoil. 
     In an embodiment, the first side wall is a pressure side wall, and the second side wall is a suction side wall. In another embodiment, the first side wall is the suction side wall, and the second side wall is the pressure side wall. 
     In an embodiment, the tip surface is a tip shelf that is recessed into the tip endwall. In one embodiment, the tip surface is continuous with the first side surface. 
     In an embodiment, at least a portion of the tip outlet extends to the tip surface along an axis that is angled relative to the first side surface. 
     In an embodiment, the microcircuit cavity includes a cavity length that extends radially through the first side wall. In one embodiment, the inlet is one of a plurality of inlets that extend from the main cavity to the microcircuit cavity, and the inlets are arranged radially along the cavity length. In another embodiment, the side wall outlet is one of a plurality of side wall outlets that extend from the microcircuit cavity to the first side surface, and the side wall outlets are arranged radially along the cavity length. 
     In an embodiment, the rotor blade also includes a second microcircuit. The second microcircuit includes a second microcircuit cavity, a second inlet, a second side wall outlet, and a second tip outlet. The second microcircuit cavity is embedded within the first side wall. The second inlet extends from the main cavity to the second microcircuit cavity. The second side wall outlet extends from the second microcircuit cavity to the first side surface. The second tip outlet extends from the second microcircuit cavity to the tip surface. 
     In an embodiment, the rotor blade also includes a cooling passage that extends from the main cavity to one of the first side surface and the tip surface. 
     In an embodiment, the rotor blade also includes a protrusion that extends into the microcircuit cavity. 
     According to a second aspect of the invention, a turbine blade for a gas turbine engine includes an airfoil and a cooling microcircuit. The airfoil includes a first (e.g., pressure or suction) side wall, a second (e.g., suction or pressure) side wall and a tip endwall, where the first side wall and the second side wall extend to the tip endwall, forming a main cavity between first side wall and the second side wall. The cooling microcircuit includes a microcircuit cavity, an inlet, a side wall outlet and a tip outlet. The microcircuit cavity is configured within the first side wall. The inlet directs cooling fluid from the main cavity into the microcircuit cavity. The side wall outlet directs a portion of the cooling fluid in the microcircuit cavity out of the airfoil to film cool an exterior first side surface of the airfoil. The tip outlet directs a portion of the cooling fluid in the microcircuit cavity out of the airfoil to film cool an exterior tip surface of the airfoil. 
     In an embodiment, the first side wall is a pressure side wall, and the second side wall is a suction side wall. In another embodiment, the first side wall is the suction side wall, and the second side wall is the pressure side wall. 
     In an embodiment, the tip surface is a tip shelf that is recessed into the tip endwall. In one embodiment, the tip surface is continuous with the first side surface. 
     In an embodiment, the tip outlet directs the cooling fluid out of the airfoil along an axis that is angled relative to the first side surface. 
     In an embodiment, the microcircuit cavity includes a cavity length that extends radially through the first side wall. The side wall outlet is one of a plurality of side wall outlets that direct a portion of the cooling air in the microcircuit cavity out of the airfoil to film cool the first side surface, and the side wall outlets are arranged radially along the cavity length. 
     In an embodiment, the turbine blade also includes a cooling passage that directs cooling fluid in the main cavity out of the airfoil to film cool one of the first side surface and the tip surface. 
     In an embodiment, the turbine blade also includes a protrusion that extends into the microcircuit cavity. 
     The foregoing features and the operation of the invention will become more apparent in light of the following description and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional illustration of a gas turbine engine; 
         FIG. 2  is a perspective illustration of a rotor blade; 
         FIG. 3  is a cross-sectional illustration of an outer radial section of an airfoil; 
         FIG. 4  is a schematic flow diagram of a plurality of cooling circuits for a rotor blade airfoil; 
         FIG. 5  is a side-sectional illustration of an outer radial section of a cooling circuit; 
         FIG. 6  is a cross-sectional illustration of an outer radial section of an airfoil; 
         FIG. 7  is a cross-sectional illustration of an outer radial section of an airfoil; 
         FIG. 8  is a cross-sectional illustration of an outer radial section of an airfoil; and 
         FIG. 9  is a schematic flow diagram of a plurality of cooling circuits for a rotor blade airfoil. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is a cross-sectional illustration of a gas turbine engine  10 . The engine  10  includes a fan section  12 , a compressor section  14 , a combustor section  16  and a turbine section  18 , which are sequentially arranged between an engine airflow inlet  20  and an engine airflow exhaust  22 . The turbine section  18  includes one or more rotor stages  24 . Each rotor stage  24  includes a plurality of rotor blades  26  arranged circumferentially around a rotor disc  28 . 
       FIG. 2  is a perspective illustration of one of the rotor blades  26  (e.g., a high pressure turbine blade) included in the engine  10  illustrated in  FIG. 1 . The rotor blade  26  includes a platform  30  connected between a root  32  and a hollow airfoil  34 , and one or more side wall cooling circuits  36 ,  38  and  40 . The cooling circuits are known and often referred to in the art as “microcircuit cooling circuits”. 
     The airfoil  34  has an airfoil geometry that defines a concave pressure side surface  42 , a convex suction side surface  44 , a leading edge  46 , a trailing edge  48  and a tip  50 . The pressure side surface  42  and the suction side surface  44  extend axially between the leading edge  46  and the trailing edge  48 . The pressure side surface  42  and the suction side surface  44  extend radially from the platform  30  to the tip  50 . The tip  50  includes a first tip surface  52 , and a second tip surface  54  that is contiguous with the pressure side surface  42 . 
     Referring to  FIGS. 2 and 3 , the airfoil  34  includes a pressure side wall  56 , a suction side wall  58  and a tip endwall  60 . The pressure side wall  56  and the suction side wall  58  are connected together along the leading edge  46  and the trailing edge  48 . The pressure side wall  56  and the suction side wall  58  extend radially from the platform  30  to the tip endwall  60  defining a main cavity  62  between the pressure side wall  56  and the suction side wall  58  (see  FIG. 3 ). Referring to  FIG. 2 , the tip endwall  60  includes a leading edge segment  64 , a trailing edge segment  66 , an intermediate segment  68 , and a tip shelf  70  that defines the second tip surface  54 . The intermediate segment  68  extends axially between the leading edge segment  64  and the trailing edge segment  66 . The tip shelf  70  is recessed radially into the intermediate segment  68 , and extends axially between the leading edge segment  64  and the trailing edge segment  66 . 
     Referring to  FIGS. 3 and 4 , each of the cooling circuits  36 ,  38 ,  40  may include a microcircuit cavity  72 , one or more inlets  74 , one or more side wall outlets  76 , and at least one tip outlet  78 . The microcircuit cavity  72  may include a cavity length  80  that extends radially from a first cavity end  82  to a second cavity end  84 . The first cavity end  82  is located proximate a base  85  of the airfoil  34 . The second cavity end  84  is located proximate the tip  50 . The microcircuit cavity  72  may be configured (e.g., embedded) within the pressure side wall  56 . Each inlet  74  extends from the main cavity  62  to the microcircuit cavity  72 . 
     Referring to  FIGS. 3 and 4 , the inlets  74  may be arranged radially along the cavity length  80 . 
     Each side wall outlet  76  extends from the microcircuit cavity  72  to the pressure side surface  42 . Referring to  FIGS. 2 and 4 , the side wall outlets  76  may be arranged radially along the cavity length  80 . 
     Referring to  FIG. 3 , the tip outlet  78  extends from the second cavity end  84  to the second tip surface  54 . In alternate embodiments, the tip outlet may extend from the second cavity end to the first tip surface where, for example, the airfoil does not include the tip shelf. 
     During engine operation, the main cavity  62  receives cooling fluid from a source; e.g., compressor air bled from the compressor stage  14  illustrated in  FIG. 1 . The inlets  74  for each respective cooling circuit  36 ,  38 ,  40  direct at least a portion of the cooling fluid from the main cavity  62  into the microcircuit cavity  72 . The cooling fluid received from the inlets  74  flows through the microcircuit cavity  72  and convectively cools the pressure side wall  56 . The side wall outlets  76  direct a first portion of the cooling fluid in the microcircuit cavity  72  out of the airfoil  34  to film cool the pressure side surface  42 . The tip outlet  78  directs a second portion of the cooling fluid in the microcircuit cavity  72  out of the airfoil  34  to film cool the tip  50 . The expelled second portion of the cooling fluid may also create a fluidic barrier that reduces migration of relatively hot gas path air (e.g., air flowing through the turbine section) over the tip  50 . In addition, some of the expelled second portion of the cooling fluid may collect and provide a pocket of cooling fluid on the tip shelf  70  that protects the tip  50  from the hot gas path air. 
       FIG. 5  is a side-sectional illustration of a cooling circuit  88 . In contrast to the cooling circuit illustrated in  FIG. 3 , the cooling circuit  88  includes one or more protrusions  90  and  92  (e.g., pedestals, vanes, etc.) that extend into/through the microcircuit cavity  72 . The protrusions  90  and  92  may be configured to increase convective cooling within the pressure side wall  56 , reduce stresses on the pressure side wall  56 , or direct the cooling fluid through the microcircuit cavity  72  along one or more trajectories, etc. Additional examples of such protrusions are disclosed in U.S. Pat. No. 6,932,571, which is hereby incorporated by reference in its entirety, and is commonly assigned to the assignee of the present invention. 
       FIG. 6  is a cross-sectional illustration of an airfoil  94  including a tip outlet  96 . In contrast to the tip outlet  78  illustrated in  FIG. 3 , the tip outlet  96  includes a first tip outlet segment  98  and a second tip outlet segment  100 . The first tip outlet segment  98  extends from the microcircuit cavity  72  to the second tip outlet segment  100 . The second tip outlet segment  100  extends from the first tip outlet segment  98  along an axis  102  to the second tip surface  54 , where the axis  102  is angled (e.g., acute or obtuse) relative to the second tip surface  54  and/or the pressure side surface  42 . 
       FIG. 7  is a cross-sectional illustration of an airfoil  104 . In contrast to the airfoil  34  illustrated in  FIG. 3 , the airfoil  104  includes one or more cooling passages  106 ,  108  and  110  that provide additional film cooling to the tip  50 . The cooling passages may include a first cooling passage  106 , a second cooling passage  108  and a third cooling passage  110 . The first cooling passage  106  extends from the main cavity  62  to the second tip surface  54 . The second and the third cooling passages  108  and  110  extend from the main cavity  62  to the first tip surface  52 . The present invention, however, is of course not limited to the aforesaid cooling passage configurations. It is also contemplated that an airfoil may include a combination of the tip outlets illustrated in  FIGS. 3 ,  6  and/or  7 . 
       FIG. 8  is a cross-sectional illustration of an airfoil  112 . In contrast to the airfoil  34  illustrated in  FIG. 3 , the airfoil  112  includes at least one suction side wall cooling circuit  114 . The cooling circuit  114  may be configured in a similar manner as described above with respect to, for example, the cooling circuits  36 ,  38 ,  40  and/or  88 . In the embodiment illustrated in  FIG. 8 , for example, the cooling circuit  114  includes a microcircuit cavity  116 , at least one inlet  118 , at least one side wall outlet  120 , and at least one tip outlet  122 . The microcircuit cavity  116  is embedded within the suction side wall  58 . The inlet  118  extends from the main cavity  62  to the microcircuit cavity  116 . The side wall outlet  120  extends from the microcircuit cavity  116  to the suction side surface  44 . The tip outlet  122  extends from the microcircuit cavity  116  to the tip surface  52 . In alternative embodiments, however, the tip outlet may extend from the microcircuit cavity to, for example, a tip shelf surface contiguous with the suction side surface. 
       FIG. 9  is a schematic flow diagram of a plurality of cooling circuits for an airfoil  124 . In contrast to the airfoil  34  illustrated in  FIG. 4 , one or more of the cooling circuits  36 ,  38  and  40  may be interconnected within the side wall. 
     In some embodiments, one or more of the side wall outlets may have a rectangular cross-sectional geometry that flares outwards as the outlets extend from the main cavity to the pressure (and/or suction) side surface as illustrated, for example, in  FIGS. 2 and 5 . In some embodiments, the tip outlet may have a rectangular cross-sectional geometry that flares outwards as the outlet extends from the main cavity to the second tip surface as illustrated, for example, in  FIGS. 2 and 5 . One of ordinary skill will appreciate that the outlet geometry of the side wall outlets and/or the tip outlets may take various alternate shapes in order to provide the desired cooling. 
     In some embodiments, one of more of the cooling circuits may extend radially inwards from the airfoil into, for example, the blade root. 
     The cooling circuits, cooling passages and/or cavities described above may be formed utilizing, for example, one or more of the following methods: drilling, electrical discharge machining, electrical chemical machining, laser machining, water jet machining, and casting. The present invention, however, is of course not limited to any particular formation methods. 
     While various embodiments of the present invention have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. For example, the present invention as described herein includes several aspects and embodiments that include particular features. Although these features may be described individually, it is within the scope of the present invention that some or all of these features may be combined within any one of the aspects and remain within the scope of the invention. Accordingly, the present invention is not to be restricted except in light of the attached claims and their equivalents.