Abstract:
A turbine blade airfoil assembly includes a cooling air passage. The cooling air passage includes a plurality of impingement openings that are isolated from at least one adjacent impingement opening. The cooling air passage is formed and cast within a turbine blade assembly through the use of a single core. The single core forms the features required to fabricate the various separate and isolated impingement openings. The isolation and combination of impingement openings provides for the augmentation of convection and film cooling and provide the flexibility to tailor airflow on an airfoil to optimize thermal performance of an airfoil.

Description:
[0001]     This application is a divisional of U.S. Ser. No. 10/984,216 filed Nov. 9, 2004. 
     
    
       [0002]     The U.S. Government may have certain rights in this invention in accordance with Contract Number N00019-02-C-3003 awarded by the United States Navy. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     This invention relates generally to a cooling passage for an airfoil. More particularly, this invention relates to a core assembly for the formation of cooling passages for an airfoil.  
         [0004]     A gas turbine engine typically includes a plurality of turbine blades that transform energy from a mainstream of combustion gasses into mechanical energy that rotates and drives a compressor. Each of the turbine blades includes an airfoil section that generates the rotational energy desired to drive the compressor from the flow of main combustion gasses.  
         [0005]     The turbine blade assembly is exposed to the hot combustion gasses exhausted from the combustor of the gas turbine engine. The temperature of the combustion gasses exhausted through and over the turbine blade assemblies can decrease the useful life of a turbine blade assembly. It is for this reason that each turbine blade is provided with a plurality of cooling air passages. Cooling air is fed through each of the turbine blades and exhausted out film holes on the surface of the turbine blade. The position of the film holes on the turbine blade creates a layer of cooling air over the surfaces of the turbine blade. The cooling air insulates the turbine blade from the hot combustion gasses. By insulating the turbine blade from exposure to the hot combustion gasses the turbine blade reliability and useful life is greatly extended.  
         [0006]     Typically, the cooling passages within a turbine blade are formed by a ceramic core that is provided with and surrounded with molted material that is used to form the turbine blade. Once the molten material utilized to form the turbine blade is solidified the core material is removed. Removing the core material leaves the desired cooling air passages along with the desired configuration of film cooling holes.  
         [0007]     As appreciated, each turbine blade assembly represents a dead end or an end of a cooling airflow path. This is so because cooling air flowing from an inner side or platform of the turbine blade flow radially outward to a tip of the turbine blade. The tip of the turbine blade is closed off forming the end of the cooling air passage. Accordingly, the only exit for cooling air through the turbine blade is through the plurality of the film cooling holes disposed about and on the surface of the turbine blade. The configuration and quantity of the film holes for cooling the turbine blade is determined to produce a desired flow rate of cooling air.  
         [0008]     The shape of the turbine blade varies throughout the cross section from a leading edge of the turbine blade to a trailing edge. The leading edge is most often much thicker than the trailing edge. However, the cooling needs in the trailing edge are often greater than those in the leading edge and therefore require cooling passages arranged within a close proximity to the trailing edge. As appreciated, cooling passages within the thinner edge section are much smaller. The smaller cooling passages require smaller core assemblies to form those cooling passages. As the size of the core assemblies are reduced the susceptibility to damage during the molding operation increases. The smaller core assemblies required the desired cooling passage in the thinner sections of the turbine blade and are more susceptible to damage during manufacturing.  
         [0009]     Accordingly, it is desirable to develop a core assembly that is robust enough to provide for reliable manufacturing process results while still providing for the formation of the smaller cooling air passages in the thinner sections of the turbine blade assembly.  
         [0010]     Another concern in the design and configuration of cooling air passages is the direction of cooling air on an inner side of the cooling passage. The cooling passage typically receives air from a main core section. The main core section of the turbine blade is in turn in communication with a cooling air source. The cooling air passage therefore includes an inner surface that is adjacent the main core and an outer surface that is adjacent an exterior surface of the turbine blade. Impingement holes within the cooling air passages communicate air from the main core into the cooling air passage and against the outer surface.  
         [0011]     Accordingly, it is desirable to develop a core assembly to form a cooling air passage within a turbine blade assembly that is both reliable during manufacturing processes and that provides the desirable cooling air flow properties to maximize to heat transfer capabilities applications.  
       SUMMARY OF THE INVENTION  
       [0012]     A sample embodiment of this invention includes a turbine blade assembly having cooling passages where each of the impingement holes is isolated from at least some of the other impingement holes. The isolation of the impingement holes within the cooling passages provides for the direction of cooling airflow to specific desired areas. Further, the core assembly utilized for forming the cooling air passages provides a series of structures that strengthen and improve manufacturability.  
         [0013]     An example turbine blade assembly of this invention is formed with a cooling air passage that is in communication with a main core. The main core is in turn in communication with cooling air from other systems. The cooling passage is formed through the use of a unique core assembly that includes a plurality of impingement holes that are isolated from each other. Isolating each of the impingement holes from at least some of the other impingement holes prevents cross flow between impingement holes to improve cooling air flow against an outer surface of the cooling passage.  
         [0014]     The core assembly provides the configuration of the cooling passages and includes impingement structures for forming the impingement openings. Each of the impingement structures is isolated from at least some of the other impingement structures by separation structures. The separation structures form the channels within the cooling passages that isolate the impingement openings. Each of the channels formed by the core assembly is in communication with expanded chambers at a side of the cooling passage. Within the expanded chamber are film structures that are provided for creating the film openings between the cooling air passage and an exterior surface of the turbine blade assembly.  
         [0015]     Accordingly, the turbine blade assembly of this invention includes cooling air passages that provide desirable cooling characteristics for the turbine blade.  
         [0016]     These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1A  is a side view of a turbine blade assembly according to this invention.  
         [0018]      FIG. 1B  is a cross-section view of a portion of the turbine blade assembly.  
         [0019]      FIG. 2  is a prospective view of an airfoil assembly.  
         [0020]      FIG. 3  is a prospective view of a portion of a core assembly according to this invention.  
         [0021]      FIG. 4  is a prospective view of an airfoil assembly according to this invention with a portion broken away to illustrate the cooling air passage.  
         [0022]      FIG. 5  is a prospective view of a core assembly according to this invention.  
         [0023]      FIG. 6  is a view of an exterior surface of a cooling passage.  
         [0024]      FIG. 7  is a plan view of a side of a core assembly according to this invention.  
         [0025]      FIG. 8  is a plan view of the other side of a core assembly as shown in  FIG. 7 .  
         [0026]      FIG. 9  is a view of one side of a core assembly according to this invention.  
         [0027]      FIG. 10  is a view of an opposite side of a core assembly illustrated in  FIG. 9 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]     Referring to  FIGS. 1A and 1B , turbine blade assembly  10  includes an airfoil section  12 , a root section  14 , and a platform section  16 . The root section  14  extends into a hub portion (not shown) as is known in the art. The root section  14  extends to the platform section  16 . The airfoil  12  extends upwardly from the platform section  16 . Turbine airfoil section  12  extends from the platform section  16  to a tip  18 . The turbine blade assembly  10  includes a leading edge  20  and a trailing edge  22 . Between the leading edge  20  and the trailing edge  22  is the exterior surface  24 . The exterior surface  24  is shaped to provide the desired transition or conversion of gas stream flow to rotational mechanical energy. As should be understood, the turbine blade assembly  10  as is shown in  FIG. 1A  is as is known to a worker skilled in the art. A worker skilled in the art with the benefit of this disclosure would understand that other airfoil configurations utilized in different applications would benefit from the disclosures and cooling passages of this invention.  
         [0029]     The turbine blade assembly  10  includes a cooling passage  30 . The cooling passage  30  is disposed within the turbine blade assembly  10 . Cooling air enters the turbine blade assembly  10  through passages  26  within the root section  14 . Cooling air enters through the passages  26  into a main core  28  ( FIG. 1B ). Main core  28  is a hollow portion within the interior of the turbine blade assembly  10 . Cooling air communicated through the passages  26  and into the main core  28  enters cooling passages  30  disposed within the turbine blade assembly  10 . Cooling air enters the cooling passages  30  from the main core  28  through a plurality of impingement opening  32 .  
         [0030]     Cooling airflow from the impingement openings  32  flows toward expansion chambers  42  disposed opposite the impingement opening  32 . Cooling airflow then proceeds through the walls of the turbine blade assembly  10  through film openings  34 . Cooling air exiting the cooling passage  30  through the film openings  34  flows over the exterior surface  24  of the turbine blade assembly  10  to provide a cooling and insulating layer of air.  
         [0031]     The turbine blade assembly  10  of this invention includes the cooling passage  30 . Each of the cooling passages  30  includes the impingement openings  32 . The impingement openings  32  are isolated from each other by channels  36 . The channels  36  are formed by a series of separating structures  38 . Separation and isolation of each of the impingement openings  32  provides for the separation of cooling flow that is impinged upon an outer surface of the cooling passage  30 . Further, isolation of adjacent impingement opening  32  prevents and reduces cross flow problems encountered with typical conventional prior art impingement opening designs. The flow from the impingement openings  32  passes through the channel  36  to the plurality of film holes  34 . Film holes  34  are in communication with the expanded chamber  42 . The expanded chamber  42  provides a portion of the cooling passage for the accumulation of cooling air that is to be communicated to the film openings  34 . The accumulation of cooling air within the expanded chamber  42  reduces problems associated with back wall strikes corresponding with impingement openings  32 .  
         [0032]     Referring to  FIG. 2 , a prospective view of the airfoil  12  is shown to illustrate the configuration of the main core  28 . The main core  28  provides for communication of cooling air up through the central portion of the turbine blade assembly  10  and to communicate with cooling passages  30 . The specific shape and configuration of the turbine blade assembly and the airfoil  12  illustrated in  FIG. 2  is as known. A worker with the benefit of the disclosure would understand that many different types of airfoil configurations will benefit from this the cooling passage configuration illustrated and described within this disclosure.  
         [0033]     Referring to  FIG. 3 , the cooling passage  30  is formed within the turbine blade assembly  10  through the use of core assembly  44 . The core assembly  44  provides for the formation of the various structures and configuration including openings, channels of the cooling passage during fabrication of the turbine blade assembly  10 . Conventionally, the turbine blade assembly  10  is fabricated through the use of a conventional molding process. The core assembly  44  can be fabricated from known core materials such as specially formulated ceramic and refractory metals. The core assembly  44  is placed within a mold and then surrounded by molten material that will comprise the turbine blade assembly  10 . Upon solidification of the material forming the turbine blade assembly  10 , the core assembly  44  is removed. Removal of the core assembly  44  is as known and can comprise various processes including leeching or oxidation process where a chemical are used to destroy and leech out the core assembly  44 . As appreciated, a worker versed in the art with the benefit of this disclosure would understand that the use of other molding process and materials as are known are within the contemplation and scope of this invention. The type of removal process that is utilized to remove the core  44  from the turbine blade assembly  10  will depend on various factors. These factors include the type of turbine blade material, the type of core material used and the specific configuration of the cooling air passage.  
         [0034]     The core assembly  44  utilized to form intricate cooling air passages required to provide the desired cooling properties within the turbine blade assembly  10 . The core assembly  44  includes impingement structures  46  that extend and provide formation of the impingement openings  32  within a completed turbine assembly  10 . Core assembly  44  also includes separation structures  48  that form the channels and walls that are required for isolating each of the impingement openings  32  from at least another of the impingement openings  32 .  
         [0035]     Referring to  FIG. 4 , an airfoil  12  is shown with a portion of the surface removed to illustrate the specific features of the cooling air passage formed therein. The cooling air passage  30  includes the expanded chambers  42  on each side of the cooling air passage  30 . The cooling air passage  30  includes a lead edge side  50  and a trailing edge side  52 . Each side of the cooling air passage  30  includes an expansion chamber  42 . Adjacent impingement openings  32  communicate with an expansion chamber  42  disposed on an opposite side of the cooling air passage  30 . No two adjacent impingement openings communicate cooling air to a common expansion chamber  42 . In this way the specific cooling flow can be controlled and tailored to provide cooling to specific areas and features of the airfoil  12 .  
         [0036]     Referring to  FIG. 5 , an example core assembly  44  is shown and includes the impingement structures  46  utilized to form the impingement openings  32  within the airfoil  12 . The impingement openings  32  communicate cooling air from the main core  28  into the cooling passage  30 . The core assembly  44  also includes the separation structures  48  that utilize and provide for the separation of cooling air through each adjacent impingement opening  32 . The core assembly  44  includes a reverse structure from that which will be formed within the completed turbine blade airfoil  12 . The impingement structures  46  therefore are extensions that will extend through and provide the openings through the airfoil  12  to the main core  28 . The structure and space of the core assembly  44  provides for the open spaces within the completed airfoil  12 .  
         [0037]     The core assembly  44  also includes a plurality of heat transfer enhancement features  60 . These heat transfer enhancement features  60  are formed in the core assembly  44  as openings such that within the completed cooling air passage  30  the heat transfer enhancement features  60  will form a plurality of ridges that extend upward within the various of the cooling air passage  30 . A worker with the benefit of this disclosure would understand that different shapes of the heat transfer enhancement features  60  other than the examples illustrated that disrupt or direct airflow are within the contemplation of this invention.  
         [0038]     Referring to  FIG. 6 , an outer side  56  is illustrated. The outer side  56  is cut away from the airfoil  12  illustrated in  FIG. 4 . The outer side  56  is not typically sectioned as is shown in  FIG. 6  but is an integral portion of the airfoil  12 . The outer side  56  is adjacent the exterior surface of the airfoil  12 .  FIG. 4  illustrates an inner side  54  of the cooling passage  30 . The inner side is adjacent the main core  28 . It is for this reason that the ridges  62  are provided on the outer side  56  illustrated in  FIG. 6 . As appreciated, thermal energy radiates along the exterior surface  24 .  
         [0039]     The outer side  56  that is adjacent the exterior portion of the airfoil  12  is provided on which cooling air flow can most affect desired heat absorption and transfer. Airflow through the impingement openings  32  strikes the outer sides  56  immediately across from the impingement openings  32 . Airflow will then proceed as directed by the channels  36  towards the trailing edge or leading edge side towards the expansion chamber  42 . Through the channels  36  air will be controlled and tailored to create turbulent effects that increase heat transfer and absorption properties. Once air has reached the expansion chambers  42  it is accumulated and exhausted out the film holes  34 . Through the film holes  34  the air will then be exhausted into the main combustion gas stream. The example core assembly  44  is substantially straight. However, the core assembly  44  may include a curved shape to conform to an application specific airfoil shape.  
         [0040]     Referring to  FIG. 7 , a portion of the core assembly  44  is shown that provides for the formation of the outer side  56  of the cooling air passage  30 . The core assembly  44  includes the structures that form the channels  36 , film holes  34 , and separating structures  38 . The impingement structures  46  are illustrated in dashed lines to indicate that they do not extend outwardly from this side of the core  44 . Instead the impingement openings are formed from extensions or structures  46  that extend from an opposite side of the core. This side of the core assembly  44  produces these features within the outer side  56  of the cooling air passage  30  of the completed airfoil  12 . In this example core assembly  44 , each impingement structure  46  it opens into a separate channel  36 . Therefore each of the impingement openings  32  are isolated from any of the adjacent the impingement openings  32 . Within each of the channels are a plurality of the heat transfer enhancement structures  60  that will form the desired ridges and heat transfer ridges  62  within the completed channels  36 . The heat transfer structures  60  illustrated in  FIG. 7  are cavities that receive material during the molding process to form the outwardly extended ridges.  
         [0041]     Referring to  FIG. 8 , an inner side of the core assembly  44  is shown and includes the impingement structures  46 . The separation structures  48  are shown in dashed lines to indicate that they would not extend from this side but would extend from the opposite side. Further, the other structures that would be formed on the outer side  56  from the inner side  54  are not shown for clarity purposes. However, as appreciated those features would extend outwardly from the opposite side and may also be represented by dashed lines in this view.  
         [0042]     Referring to  FIGS. 9 and 10 , another example core assembly  70  according to this invention, includes a plurality of impingement structures  46  disposed within separate channels  36 . In this core assembly  70 , three impingement structures  46  are disposed within each of the separation channel  36 . By providing several impingement openings within each chamber the specific air flow requirements and cooling airflow impingement on a specific area can be tailored to accommodate area specific heat transfer and absorption requirements. Although there are several impingement openings  46  disposed within each channel  36 . These are still isolated from at least one impingement opening is isolated from at least another impingement opening. Further, the impingement openings are all disposed about a centerline  40 .  
         [0043]     Although each of the impingement openings  32  are disposed about a common centerline  40  they are still isolated from at least one other impingement opening. Although it is shown in the example core assembly  70  that the impingement openings and impingement structures  46  are disposed about a centerline  40 , other configurations and locations of impingement openings are within the contemplation of this invention. A worker versed in the art will understand that isolation of at least one impingement opening relative to another impingement opening provides the desired benefits of tailoring cooling in a cooling passage.  
         [0044]     Referring to  FIG. 10 , the core assembly  70  is shown on the side opposite that shown in  FIG. 9  and illustrates the side of the core assembly  70  that would form the outer side  56  of the cooling air passage  30 . This side of the core assembly  70  illustrates the film structures  58  that would form the film holes  34  in the completed airfoil  12 . Further, heat transfer structures  60  are illustrated that would form the heat transfer ridges  64  in the completed cooling passage  30 . Further, as is shown, the impingement structures  46  are shown in dashed lines indicate their location relative to the features formed on the outer side  56 . As can be seen by  FIG. 10  the separation structures  48  and the heat transfer structures  60  provide for the creation of a tailored cooling airflow from the impingement openings to the film openings.  
         [0045]     Accordingly, the core assembly  44  and airfoil  12  of this invention provides for the tailoring and improvement of cooling air properties within a turbine blade assembly  10 . Further, the core assembly  44  includes a single core that can provide a plurality of individual channels desirable for separating airflow through each of the impingement hole openings. The isolation of the impingement openings provides improved airflow and tailoring capabilities for implementing and optimizing local cooling and flow characteristics within an airfoil.  
         [0046]     Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.