Abstract:
A cooled cast part has an exterior surface. A cooling passageway system extends from at least one inlet port to a plurality of outlet ports. The passageway system includes a first passageway to at least a first of the outlets and surrounding at least one post. The system includes a second passageway to at least a second of the outlets passing through the at least one post.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates to cooling of high temperature components. More particularly, the invention relates to film cooling of gas turbine engine components.  
         [0002]     In the aerospace industry, a well-developed art exists regarding the cooling of components such as gas turbine engine components. Exemplary components are gas turbine engine blades and vanes. Exemplary blades and vanes are cooled by airflow directed through the blade or vane airfoil to be discharged from cooling holes in the airfoil surface. The cooling mechanisms may include both direct cooling as the airflow passes through the airfoil and film cooling after the airflow has been discharged from the airfoil but passes downstream close to the airfoil surface.  
       SUMMARY OF THE INVENTION  
       [0003]     To provide effective film cooling, it is desirable to minimize the pre-discharged heating of the film cooling air. This may involve using a first airflow to cool a passageway passing a second airflow so that the second airflow exits at a lower temperature than it would in the absence of the first airflow.  
         [0004]     Accordingly, one aspect of the invention involves a cooled cast part having an exterior surface. A cooling passageway system extends from at least one inlet port to a plurality of outlet ports. The passageway system includes a first passageway to at least a first of the outlets and surrounding at least one post. The system includes a second passageway to at least a second of the outlets passing through the at least one post.  
         [0005]     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]      FIG. 1  is a view of a gas turbine engine vane.  
         [0007]      FIG. 2  is a sectional view of the vane of  FIG. 1 , taken along line  2 - 2 .  
         [0008]      FIG. 3  is a sectional view of a core assembly and pattern-forming die for forming a pattern for casting the vane of  FIG. 1 .  
         [0009]      FIG. 4  is a leading view of a refractory metal core (RMC) of the core assembly of  FIG. 3 .  
         [0010]      FIG. 5  is a trailing view of the RMC of  FIG. 4 .  
         [0011]      FIG. 6  is a spanwise end view of the RMC of  FIG. 4 .  
         [0012]      FIG. 7  is a plan view of the RMC of  FIG. 4 .  
         [0013]      FIG. 8  is a sectional view of an intermediate casting of the vane of  FIG. 1 .  
         [0014]      FIG. 9  is a plan view of an alternate core assembly.  
         [0015]      FIG. 10  is a sectional view of the core assembly of  FIG. 9  in a pattern-forming die. 
     
    
       [0016]     Like reference numbers and designations in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0017]      FIG. 1  shows a simplified gas turbine engine vane  20 . The exemplary vane is formed from a single casting and includes an airfoil  22  extending spanwise between an inboard platform  24  and an outboard shroud  26 . The exemplary platform and shroud are annular segments such that a circumferential array of the vanes may be formed with the respective platforms and shrouds mounted/sealed edge-to-edge. The airfoil  22  has a leading edge  30  and a trailing edge  32 . A pressure side  34  and suction side  36  extend streamwise between the leading and trailing edges.  
         [0018]     The exemplary airfoil is cooled by air flowing in through one or more ports  38  in one or both of the platform and shroud and exiting an array of holes along the airfoil. The exemplary airfoil of  FIG. 1  includes a spanwise series of first holes/outlets  40  along or near the leading edge  30  and second holes/outlets  42  along the pressure side  34  just downstream of the leading edge  30 . The airfoil may have other holes such as additional film cooling holes (not shown) along the pressure and suction sides and trailing edge outlets (not shown).  
         [0019]      FIG. 2  shows a region of the airfoil near the leading edge  30 . The airfoil is shown having a wall  50  locally having an interior surface  52  bounding a spanwise leading edge feed passageway  54 . A cooling plenum  55  is positioned within the wall, spanning the leading edge and having a main portion  56 . The outlets  42  are the outlets of the plenum  55  at ends of associated pressure outlet passageways  57 . A corresponding spanwise series of inlets  58  feed the plenum through corresponding inlet passageways  59 . Accordingly, a first airflow  60  passes through the plenum  55  from the inlets  58  and is discharged from the outlets  42  to flow downstream along the pressure side  34 . The flow  60  thus provides direct cooling of the wall  50  adjacent the plenum and may also provide film cooling of the wall  50  along the pressure side  34  downstream of the outlets  42 .  
         [0020]     Cooling near the leading edge  30  may be particularly important. To provide additional cooling, a series of outlet passageways  62  extend directly to the outlets  40  from associated inlets  64  along the feed passageway  54 . The passageways  62  pass an airflow  61  which exits the outlets  40 . The passageways  62  pass through posts  66  within the plenum main portion  56 . The posts  66  span between inboard and outboard portions of the wall  50 . The perimeter surface  70  of each post is cooled by the airflow  60 . This cooling limits the heating of the second airflow  61  as the second airflow passes between the inlets  64  and outlets  40 . Accordingly, the airflow  61  may be relatively cool upon discharge from the outlets  40  and thus provides a particularly enhanced film cooling effect.  
         [0021]     The vane  20  or other cooled component may be formed by an investment casting process. An exemplary process uses a refractory metal core (RMC)  100  ( FIG. 3 ) to cast the plenum  55  and a ceramic feedcore  102  to cast the feed passageway  54 .  FIG. 3  shows the RMC  100  assembled to the feedcore  102  within a pattern die  104 . The exemplary die  104  has a pair of die halves or pulls  106  and  108  having interior surfaces  110  positioned to define a cavity  112  for molding sacrificial pattern material (e.g., natural or synthetic wax) over the core assembly. After molding, the pattern may be removed from the die and shelled (e.g., in a multi-stage stuccoing process). The shell may be dewaxed and fired to form a mold in which molten metal is cast. After casting, the shell and core assembly may be removed (e.g., by mechanical breaking of the shell and chemical removal of the core assembly). The casting may be subject to machining and additional treatment including the application of a protective coating.  
         [0022]      FIGS. 4-7  show further details of the exemplary RMC  100 . The RMC  100  has a main body  120  extending from a first spanwise end  122  to a second spanwise end  124 . The body  120  is shaped to cast the plenum main portion  56 . Accordingly, the body  120  has a spanwise array of apertures  126  positioned and shaped to cast the posts  66 . The posts  126  extend between an inner core surface  128  and an outer core surface  130 . The body  120  has a first edge  140  from which a spanwise array of tabs  142  extend. The body has a second edge  144  from which a spanwise array of tabs  146  extend. Proximal portions of the tabs  142  are positioned and configured to cast the plenum outlet passageways  57 . Distal portions of the tabs  142  may be received in corresponding compartments in the die to register the RMC relative to the die. The distal portions of the tabs  142  may, subsequently, become embedded in the shell to retain/position the RMC during casting. Proximal portions of the tabs  146  are positioned and configured to cast the inlet passageways  59 . Distal portions of the tabs  146  are configured to be received in one or more corresponding compartments in the feed core  102  to secure and register the RMC relative to the feed core.  
         [0023]      FIG. 8  shows the as-cast part prior to drilling the passageways  62  and their outlet holes  40 . Exemplary drilling may be by mechanical drilling, laser drilling, or electro-discharge machining (EDM). Alternatively, the passageways  62  could be cast. In one example,  FIGS. 9 and 10  show a second RMC  150  for forming the passageways  62  and outlets  40 . The exemplary RMC  150  is comb-like, having a spine  152  and a spanwise array of tines  154  extending from the spine. Proximal portions of the tines  154  are configured and positioned to pass through the apertures  126  in the first RMC  100 . Distal portions are positioned and configured to be received by a ceramic feedcore  160  ( FIG. 10 ) which may be otherwise similar to the feedcore  102 . In an exemplary core assembly sequence, the first RMC  100  is assembled to the feedcore  160 . Then, the second RMC  150  is assembled to the feedcore by inserting its tines  154  through the apertures  126  and into one or more slots or other blind compartments in the feedcore  160 . The core assembly may then be placed in a pattern-forming die  170 .  
         [0024]     One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, when implemented in the reengineering of a baseline component, details of the baseline component may influence details of any particular implementation. Although the exemplary posts are of circular cross-section and spaced apart from the adjacent plenum wall around entireties of their peripheries, other configurations are possible. Similarly, various shapes and distributions of the holes through the posts are possible. Accordingly, other embodiments are within the scope of the following claims.