Abstract:
An example airfoil assembly includes a base having an airfoil projecting radially therefrom. The base extends laterally away from the airfoil. The airfoil extends axially from an airfoil leading edge portion to an airfoil trailing edge portion. The base has a humped area forward the airfoil leading edge portion.

Description:
BACKGROUND 
       [0001]    This application relates generally to gas turbine engine airfoil arrays. More particularly, this application relates to influencing fluid flow near the leading edge portions of the airfoils within the airfoil array. 
         [0002]    Gas turbine engines are known and typically include multiple sections, such as a fan section, a compression section, a combustor section, a turbine section, and an exhaust nozzle section. The fan section moves air into the engine. The air is compressed in the compression section. The compressed air is mixed with fuel and is combusted in the combustor section. Products of the combustion expand to rotatably drive the engine. 
         [0003]    Some sections of the engine include vane arrays, blade arrays, or both. Air within the engine moves through fluid flow passages in the arrays. The fluid flow passages are established by adjacent airfoils projecting from laterally extending endwalls. As known, air approaching the fluid flow passages can separate from portions of the arrays. The separation within the engine can disadvantageously increase aerodynamic losses and can contribute to locally increased convective heat loads. The separation often occurs in vane arrays or blade arrays having airfoils with low camber angles, such as some of the airfoils within the turbine section of the engine. 
       SUMMARY 
       [0004]    An example airfoil assembly includes a base having an airfoil projecting radially therefrom. The base extends laterally away from the airfoil. The airfoil extends axially from an airfoil leading edge portion to an airfoil trailing edge portion. The base has a humped area forward the airfoil leading edge portion. 
         [0005]    An example gas turbine engine assembly includes an endwall and an array of airfoils circumferentially distributed about an axis. The endwall and the airfoils establish a plurality of fluid flow passages. A plurality of convex features is circumferentially distributed about the axis. At least a portion of the convex features are positioned axially forward the fluid flow passages and is configured to influence flow through the fluid flow passages. 
         [0006]    An example method of influencing flow within a gas turbine engine includes moving a fluid axially toward a fluid flow passage established between adjacent airfoils in a gas turbine engine. The airfoils project radially from an endwall. The method also includes limiting flow separation of the fluid near at least one of the airfoils using a hump projecting from the endwall. 
         [0007]    These and other features of the example disclosure can be best understood from the following specification and drawings, the following of which is a brief description: 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  shows a schematic view of an example gas turbine engine. 
           [0009]      FIG. 2  shows a perspective view of an example airfoil array within the  FIG. 1  engine. 
           [0010]      FIG. 3  shows a prior art airfoil array. 
           [0011]      FIG. 4  shows a perspective view of an example airfoil assembly from the  FIG. 2  airfoil array. 
           [0012]      FIG. 5  shows a sectional view taken at line  5 - 5  of  FIG. 4 . 
           [0013]      FIG. 6  shows a sectional view taken at line  6 - 6  of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  schematically illustrates an example gas turbine engine  10  including (in serial flow communication) a fan section  14 , a low-pressure compressor  18 , a high-pressure compressor  22 , a combustor  26 , a high-pressure turbine  30 , and a low-pressure turbine  34 . The gas turbine engine  10  is circumferentially disposed about an engine centerline X. During operation, air is pulled into the gas turbine engine  10  by the fan section  14 , pressurized by the compressors  18  and  22 , mixed with fuel, and burned in the combustor  26 . The turbines  30  and  34  extract energy from the hot combustion gases flowing from the combustor  26 . 
         [0015]    In a two-spool design, the high-pressure turbine  30  utilizes the extracted energy from the hot combustion gases to power the high-pressure compressor  22  through a high speed shaft  38 . The low-pressure turbine  34  utilizes the extracted energy from the hot combustion gases to power the low-pressure compressor  18  and the fan section  14  through a low speed shaft  42 . The examples described in this disclosure are not limited to the two-spool architecture described and may be used in other architectures, such as a single-spool axial design, a three-spool axial design, and still other architectures. That is, there are various types of engines that could benefit from the examples disclosed herein, which are not limited to the design shown. 
         [0016]    Referring to  FIGS. 2 and 4  with continuing reference to  FIG. 1 , an example airfoil array  50  includes a plurality of airfoils  54  circumferentially arranged about the engine centerline X. The airfoils  54  project radially from an endwall  58  comprised of a plurality of airfoil bases  60 . The airfoil array  50  is mounted for rotation within the engine  10  about the engine centerline X. In this example, an airfoil assembly  61  includes one of the airfoils  54  and one of the bases  60 . In another example, such as when the airfoils  54  are vanes, the airfoils span between two bases and are not mounted for rotation within the engine  10 . 
         [0017]    The airfoils  54  extend axially from an airfoil leading edge portion  62  to an airfoil trailing edge portion  66 . Adjacent ones of the airfoils  54  establish a flow passage  70  with the endwall  58 . As known, fluid flow, such as airflow, moves toward the flow passage  70  from a position forward the leading edge portion  62  of the airfoils  54  as the engine  10  operates. 
         [0018]    In this example, the endwall  58  includes a hump  74  extending axially forward the leading edge portions  62  of the airfoils  54  within the airfoil array  50 . The example hump  74  extends radially away from the engine centerline X relative to a surface  76  of the endwall  58  adjacent the hump  74 . The example airfoils  54  project radially outward from the endwall  58  having the hump  74 . In another example, such as when the airfoils  54  comprise vanes, the airfoils  54  project radially inward from an endwall having the hump  74 , and the hump  74  extends radially inward toward the engine centerline X. An endwall  80  in a prior art airfoil array  78  ( FIG. 3 ) lacks the hump  74 . 
         [0019]    Referring now to  FIGS. 5 and 6  with continued reference to  FIGS. 2 and 4 , a surface  72  of the hump  74  is convex in this example relative to a surface  76  of the endwall adjacent the hump  74 . That is, the concavity of the surface  72  of the hump  74  projects radially inward. At least a portion of the example hump  74  is axially forward the leading edge portion  62  of the airfoil  54 , which enables the hump  74  to influence flow prior to the flow entering the flow passage  70 . 
         [0020]    The example hump  74  has a radial peak  82  at an interface  86  of the hump  74  and the airfoil  54 . In another example, the radial peak  82  of the hump  74  is axially forward the interface  86 . Although some portions of the hump  74  extend rearward into the flow passage  70 , the radial peak  82  of the hump  74  is forward the leading edge portion  62  and thus forward the flow passage  70 . In yet another example, the radial peak  82  of the hump  74  is axially rearward the interface  86 . 
         [0021]    A radial height h 1  of the hump  74  corresponds to the distance between the surface  76  of the endwall  58  and the radial peak  82 . In this example, the radial height h 1  of the hump  74  is between 5% and 25% the radial height h 2 , or span, of the airfoil  54 . 
         [0022]    The example airfoil  54  is a low camber airfoil, which typically corresponds to airfoil  54  having a camber angle θ of less than 60°. In this example, the camber angle θ of the airfoil  54  is about 30°. As known, low camber airfoils, such as the airfoil  54 , are particularly prone to separation of flow near the leading edge portions  62 . Higher camber airfoils, however, could also benefit from the hump  74 . 
         [0023]    The example airfoil array  50  the airfoil array  50  is a turbine exit guide vane assembly. In another example, the airfoil array  50  is a mid-turbine frame component that is positioned axially between the high-pressure turbine  30  and the low-pressure turbine  34  of the engine  10  ( FIG. 1 ). As known, mid-turbine frame components may include airfoils having 0 camber angle. In yet another example, the airfoil array  50  is a counter rotating vane assembly. 
         [0024]    Features of the disclosed embodiments include reducing convective heat loads and improving aerodynamic performance of airfoil arrays by positioning a hump near the leading edges of airfoils within the airfoil array, and particularly the leading edges of low camber airfoils. 
         [0025]    Although a preferred embodiment 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.