Abstract:
A vane assembly used for controlling a turning gas flow includes multiple vanes, each of which is bowed toward a pressure side of the vane at the root of the vane.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates generally to airfoils for controlling a turning gas flow, and more particularly to a geometry for an airfoil shaped vane. 
       BACKGROUND OF THE INVENTION 
       [0002]    Power generation systems that incorporate a compressor, a combustor, and a turbine arranged in a flow series from an inlet to an exhaust are typically referred to as gas turbine engines. The compressor compresses air from the inlet, the air is mixed with fuel in a combustor and ignited to produce combustion gasses that drive the turbine and are expelled at the exhaust. The gas turbine engine often includes a duct portion, connecting a high pressure turbine to a low pressure turbine. The duct portion includes a vane assembly with multiple airfoil shaped vanes that are arranged circumferentially about the duct and impart desirable flow characteristics onto the gas flowing through the duct. Similar vane assemblies and airfoil shaped vanes are used in other gas flow control applications. 
         [0003]    In known configurations, the airfoil shaped vanes contact an interior end wall (referred to as an inner diameter wall) of the vane assembly at sharp, acute, angles on the pressure side of the vane. The sharpness of the junction between the vane and the inner diameter wall increases secondary flow losses within the system, thereby reducing the efficiency of the airfoil. 
       SUMMARY OF THE INVENTION 
       [0004]    A stationary vane according to an exemplary embodiment of this disclosure, among other possible things includes a suction side surface and a pressure side surface. Each of the surfaces extends from a leading edge of the vane to a trailing edge of the vane. A chord line extends from a midpoint of the leading edge to a midpoint of the trailing edge. A radial line extends from a tip of the vane to an axis defined by vane assembly, and a bowing region at a root portion of the vane operable reduces secondary flow losses. The bowing region defines a junction angle between the suction side surface and an inner diameter mounting surface. The angle is greater than 70 degrees. 
         [0005]    In a further embodiment of the foregoing stationary vane, the bowing region is a region of the root portion that diverges from the radial line. 
         [0006]    In a further embodiment of any of the foregoing stationary vanes, the bowing region extends from approximately 5% span to 0% span of the vane. 
         [0007]    In a further embodiment of any of the foregoing stationary vanes, the root portion diverges such that a 0% span of the root portion is the farthest diverged point of the root portion. 
         [0008]    In a further embodiment of any of the foregoing stationary vanes, the vane abuts an inner diameter end wall in an installed configuration such that a junction between the vane and the end wall is approximately continuous. 
         [0009]    In a further embodiment of any of the foregoing stationary vanes, the diverged root portion of the vane extends a full axial length of the chord line. 
         [0010]    In a further embodiment of any of the foregoing stationary vanes, the diverged root portion of the vane extends from a throat point of said vane to a trailing edge of said vane. 
         [0011]    In a further embodiment of any of the foregoing stationary vanes, further including a vane aspect ratio of less than or equal to 1.5. 
         [0012]    In a further embodiment of any of the foregoing stationary vanes, the stationary vane is configured for use in a duct having a duct angle of at least 10 degrees. 
         [0013]    A vane assembly for a gas flow duct according to an exemplary embodiment of this disclosure, among other possible things includes an inner diameter end wall defining an axis, an outer diameter end wall coaxial with the inner diameter end wall, a plurality of vanes arranged circumferentially between the inner diameter end wall and the outer diameter end wall. Each of said vanes further includes a suction side surface and a pressure side surface. Each of the surfaces extends from a leading edge of the vane to a trailing edge of the vane. A chord line extends from a midpoint of the leading edge to a midpoint of the trailing edge. A radial line extends from a tip of the vane to an axis defined by vane assembly, and a bowing region at a root portion of the vane operable reduces secondary flow losses. A junction angle between the suction side surface of the bowing region and the inner diameter endwall is greater than 70 degrees. 
         [0014]    In a further embodiment of the foregoing vane assembly, the bowing region is a region of the root portion that diverges from the radial line. 
         [0015]    In a further embodiment of any of the foregoing vane assemblies, the bowing region extends from approximately 5% span to 0% span of the vane. 
         [0016]    In a further embodiment of any of the foregoing vane assemblies, the root portion diverges such that a 0% span of the root portion is the farthest diverged point of the root portion. 
         [0017]    In a further embodiment of any of the foregoing vane assemblies, the vane abuts an inner diameter end wall in an installed configuration such that a junction between the vane and the end wall is approximately continuous. 
         [0018]    In a further embodiment of any of the foregoing vane assemblies, the diverged root portion of the vane extends a full axial length of the chord line. 
         [0019]    In a further embodiment of any of the foregoing vane assemblies, the diverged root portion of the vane extends from a throat point of the vane to a trailing edge of the vane. 
         [0020]    In a further embodiment of any of the foregoing vane assemblies, each of the plurality of vanes has a vane aspect ratio of less than or equal to 1.5. 
         [0021]    In a further embodiment of any of the foregoing vane assemblies, the inner diameter wall and the outer diameter wall define a duct having a duct angle of greater than 10 degrees. 
         [0022]    In a further embodiment of any of the foregoing vane assemblies, the plurality of vanes is less than or equal to 20 vanes. 
         [0023]    In a further embodiment of any of the foregoing vane assemblies, the plurality of vanes is a number of vanes selected from the set of 12, 18 and 20 vanes. 
         [0024]    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 
         [0025]      FIG. 1  schematically illustrates an example turbine engine. 
           [0026]      FIG. 2  illustrates a highly schematic duct side view of a vane assembly. 
           [0027]      FIG. 3  schematically illustrates a side view of a single airfoil shaped vane in a duct. 
           [0028]      FIG. 4   a  illustrates a sectional view of the isometric view of  FIG. 3 . 
           [0029]      FIG. 4   b  illustrates a top view of multiple vanes  410  in the vane assembly  100 . 
           [0030]      FIG. 5  illustrates a three dimensional view of the single airfoil of  FIG. 4 , in the context of a duct. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]      FIG. 1  schematically illustrates a gas turbine engine  20 . The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26  and a turbine section  28 . Alternative engines might include an augmentor section (not shown) among other systems or features. The fan section  22  drives air along a bypass flowpath while the compressor section  24  drives air along a core flowpath for compression and communication into the combustor section  26  then expansion through the turbine section  28 . Although depicted as a turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines including three-spool architectures. 
         [0032]    The engine  20  generally includes a low speed spool  30  and a high speed spool  32  mounted for rotation about an engine central longitudinal axis A relative to an engine static structure  36  via several bearing systems  38 . It should be understood that various bearing systems  38  at various locations may alternatively or additionally be provided. 
         [0033]    The low speed spool  30  generally includes an inner shaft  40  that interconnects a fan  42 , a low pressure compressor  44  and a low pressure turbine  46 . The inner shaft  40  is connected to the fan  42  through a geared architecture  48  to drive the fan  42  at a lower speed than the low speed spool  30 . The high speed spool  32  includes an outer shaft  50  that interconnects a high pressure compressor  52  and high pressure turbine  54 . A combustor  56  is arranged between the high pressure compressor  52  and the high pressure turbine  54 . duct  57  of the engine static structure  36  is arranged generally between the high pressure turbine  54  and the low pressure turbine  46 . The duct  57  further supports bearing systems  38  in the turbine section  28 . The inner shaft  40  and the outer shaft  50  are concentric and rotate via bearing systems  38  about the engine central longitudinal axis A which is collinear with their longitudinal axes. 
         [0034]    The core airflow is compressed by the low pressure compressor  44  then the high pressure compressor  52 , mixed and burned with fuel in the combustor  56 , then expanded over the high pressure turbine  54  and low pressure turbine  46 . The duct  57  includes airfoils  59  which are in the core airflow path. The turbines  46 ,  54  rotationally drive the respective low speed spool  30  and high speed spool  32  in response to the expansion. 
         [0035]      FIG. 2  illustrates a highly schematic duct side view (meridional) of a vane assembly  100  for use in a duct, such as the duct  57 . The vane assembly  100  defines a gas path  102  with an inner diameter wall  150  and an outer diameter wall  140 , between which turbine gasses flow. The vane assembly  100  includes multiple vanes  110  arranged circumferentially about the vane assembly  100  in the gas path  102 . In one example, the vane assembly includes less than twenty vanes. In alternate examples, there are twelve or eighteen vanes. 
         [0036]    Each vane  110  has a leading edge  112  that contacts incoming gas flow and a trailing edge  114  where the gas flow finishes passing over the vane  110 . The portion of the vane  110  contacting the outer diameter wall  140  is referred to as the vane tip  120 , and the portion of the vane  110  contacting the inner diameter wall  150  is referred to as the vane root  130 . Alternately, the portions are referred to as the tip portion  120  or the root portion  130 , respectively. The vane assembly  100  defines an axis A about which the vane assembly  100  encircles. The axis A defined by the vane assembly  100  is collinear with the engine central longitudinal axis A. The duct defined by the inner diameter wall  150  and the outer diameter wall  114  has a duct angle  104  of greater than or equal to 10 degrees, where the duct angle  104  is defined by an angle between a midspan line of the vane  110  and the axis A. 
         [0037]    The airfoil contouring of the vanes  110  causes a pressure differential in the gasses flowing through the vane assembly  100  over the vane  110 . The pressure differential creates a high pressure side and a low pressure side on each vane  110  with the pressure on the high pressure side being greater than the pressure on the low pressure side. As a consequence of the pressure differential between the high pressure side and the low pressure side, gas flow exiting the vane assembly  100  is swirled and mixed. Each of the vanes  110  is joined to the inner diameter wall  150  at an inner junction and to the outer diameter wall  140  at an outer junction. The presence of the inner junction and the outer junction increases secondary flow losses on the gas passing through the vane assembly  100  due to the acute angle of the junctions on the pressure side of the junctions. The increased secondary flow losses lead to undesirable flow characteristics. 
         [0038]      FIG. 3  illustrates a side view of a single vane  310  in the vane assembly  100  illustrated in  FIG. 2 . The vane  310  has a leading edge  312  and a trailing edge  314 . The radial height of the vane from an inner diameter wall to an outer diameter wall is referred to as a vane span  320 , with 0% span being at the root  316  of the vane  310 , and 100% span being at the tip  318  of the vane  310 . A vane chord line  330  is defined as a line connecting the midspan point of the leading edge  312  to the midspan point of the trailing edge  314 . The axial chord length  332  is the length of the vane  310  from leading edge  312  to trailing edge  314  along the engine central longitudinal axis A. In a typical example, the root  316  portion of the vane  310  refers to the 0-5% span region of the vane  310 , although it is understood that a larger range of spans could be incorporated into the root as well. Similarly, in a typical example the tip  318  portion of the vane  310  refers to the 95-100% span region of the vane  310 . A radial line  340  is shown from a point on the tip  318  of the vane  310  and normal to the axis A. The radial stacking line and the axis A define a stacking plane. The illustrated vane has an aspect ratio of less than 1.5, with the aspect ratio being defined as: ((leading edge vane span length+trailing edge vane span length)/2)/(Axial chord length  332 ). 
         [0039]      FIG. 4   a  illustrates a sectional view of the vane assembly  100  illustrated in  FIG. 2 .  FIG. 4   b  illustrates a top view of multiple vanes  410  in the vane assembly  100 . Each of the vanes  410  in the vane assembly  100  includes a root bowing feature  420  at the root portion of the vane  410 . As can be seen in the top view of  FIG. 4   b , each vane has a throat point  490  on the pressure side  430  of the vane  410 . The throat point  490  is the point on the pressure side  430  of the vane  410  defining the smallest distance between the pressure side  430  of the vane  410  and the suction side  440  of the adjacent vane  410 . The root bowing feature can be limited to an aft region of the root portion of the vane  410 . In one example, the root bowing feature is located between the throat point  490  and the trailing edge of the vane  410 . The root bowing feature  420  angles the root portion of the vane  410  toward a pressure side  430  of the vane and away from the suction side  440  of the vane. 
         [0040]    The root bowing feature  420  can further be described as the root portion of the vane  410  deviating from the plane defined by the radial line  340  and the axis A as the vane approaches 0% span. The gradual deviation of the root portion from a radial line  340  in the illustrated bowing feature  420  increases the junction angle of the junction between the vane  410  and the inner diameter end wall  450  on the pressure side  430  of the vane  410 . The angle of the root bowing feature  420  illustrated in the example of  FIG. 4  is shown via the angle lines  470 ,  480  which are exaggerated for illustrative effect. 
         [0041]    It is understood that the angle between the suction side  430  of the vane  410  and the inner diameter end wall  450  is related to, and causes, some of the secondary losses imparted on the gas flow passing through the vane assembly  100 . By bowing the root portion of the vane  410  toward the pressure side of the vane  410 , the angle defined by the junction between the root portion and the inner diameter end wall on the suction side is increased. Increasing the angle of the junction between the vane  410  and the inner diameter end wall  450  provides a more continuous transition between the vane  410  and the inner diameter end wall  450 . The more continuous transition, in turn, reduces secondary flow losses. The junction angle is defined as the angle between a line  470  tangent to the end wall at the junction point and a line parallel to the vane  410  at the junction point. 
         [0042]    In one example, the junction angle in a plane normal to axis A is 90 degrees (normal) relative to the tangent line  470  defined by the inner diameter end wall  450 . It is understood, that in some practical implementations the suction side junction angle will be an acute angle (less than 90 degrees) and the pressure side junction angle will be an obtuse angle (greater than 90 degrees). In another example, the angle defined by the junction between the root portion and the inner diameter end wall is greater than seventy degrees, but remains an acute angle. In these practical implementations, the inclusion of the root bowing feature allows the suction side junction angle to be increased to as close to 90 degrees (normal) as possible. It is further understood that, absent additional features of the inner diameter end wall, increasing the suction side junction angle via the inclusion of a root bowing feature  420  will be accompanied by a decrease in the pressure side junction angle. 
         [0043]      FIG. 5  provides a more detailed view of a single vane  510  and an inner diameter end wall  550  incorporating the above described root bow feature. As with the example of  FIG. 5 , the root bow feature  520  bows toward a pressure side  540  of the vane  510  and away from the suction side  530 . The root bowing features  520  is defined as a section of the vane  510  that bows away from the plane defined by the stacking line (illustrated in  FIG. 3 ) and the axis A, and toward the pressure side of the vane. 
         [0044]    As can be appreciated by one of ordinary skill in the art having the benefit of this disclosure, the root bowing feature can be incorporated into replacement vanes for a vane assembly without requiring any alterations to the inner diameter, the outer diameter, or any other portion of the duct module. Alternately, a new vane assembly or new duct module incorporating vanes having the root bowing feature can be incorporated into an existing gas turbine engine without requiring retrofitting of other modules. 
         [0045]    It can also be appreciated that the bowing feature can be incorporated at a tip portion of the vane and achieve similar benefits. The bowing feature can be incorporated at the tip portion either alone or in combination with the above described root bowing feature. 
         [0046]    Although an 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.