Patent Publication Number: US-2015063997-A1

Title: Airfoil trailing edge

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to airfoils, and more particularly to trailing edge regions of airfoils for use in gas turbine engines. 
     In gas turbine engines, such as industrial and aircraft systems, compressor blade failure is an important concern. One reason for blade failure relates to wake shed by upstream struts and stator vanes on the downstream blades. The wake creates unsteady pressure load on the blades and if the frequency of the wake matches with the natural frequency of the blades, the failure can be significant. Therefore, wake strength reduction is a common goal in gas turbine engine industries. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of the invention, an airfoil includes a radially inner edge extending in a radial direction of the airfoil to a radially outer edge. Also included is a leading edge extending in an axial direction of the airfoil to a trailing edge. Further included is a trailing edge geometry comprising at least one wave segment having simultaneous curvature in at least two directions. 
     According to another aspect of the invention, a compressor includes an airfoil. Also included is a trailing edge of the airfoil. Further included is a trailing edge geometry comprising a plurality of wave segments including a first wave segment having a degree of curvature in an axial direction and a second wave segment having a degree of curvature in a circumferential direction. 
     According to yet another aspect of the invention, a gas turbine engine includes a compressor section. Also included is a turbine section. Further included is an airfoil disposed in at least one of the compressor section and the turbine section, the airfoil having a trailing edge comprising a geometry having at least one wave segment including simultaneous curvature in an axial direction and in a circumferential direction. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic illustration of a gas turbine engine; 
         FIG. 2  is a partial perspective view of an inlet of a compressor section of the gas turbine engine; 
         FIG. 3  is a schematic illustration of the inlet of the compressor section; 
         FIG. 4  is a side, elevational view of the compressor section; 
         FIG. 5  is a perspective view of an airfoil according to a first embodiment; 
         FIG. 6  is a side, elevational view of the airfoil according to the embodiment of  FIG. 5 ; 
         FIG. 7  is a side, elevational view of the airfoil according to a second embodiment; and 
         FIG. 8  is a schematic illustration of various geometries of a portion of the airfoil. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The terms “axial” and “axially” as used in this application refer to directions and orientations extending substantially parallel to a center longitudinal axis of a turbine system. The terms “radial” and “radially” as used in this application refer to directions and orientations extending substantially orthogonally to the center longitudinal axis of the turbine system. The terms “upstream” and “downstream” as used in this application refer to directions and orientations relative to an axial flow direction with respect to the center longitudinal axis of the turbine system. 
     Referring to  FIG. 1 , a turbine system, such as a gas turbine engine  10 , constructed in accordance with an exemplary embodiment of the invention, is schematically illustrated. The gas turbine engine  10  includes a compressor section  12 , a combustor section  14 , a turbine section  16 , a shaft  18  and a fuel nozzle  20 . It is to be appreciated that one embodiment of the gas turbine system  10  may include a plurality of compressor sections  12 , combustor sections  14 , turbine sections  16 , shafts  18  and fuel nozzles  20 . The compressor section  12  and the turbine section  16  are coupled by the shaft  18 . The shaft  18  may be a single shaft or a plurality of shaft segments coupled together to form the shaft  18 . 
     Referring now to  FIG. 2 , a partial, cut-away view illustrates an inlet  22  of the compressor section  12 .  FIG. 3  schematically illustrates the inlet  22  of the compressor section  12 . The inlet  22  generally refers to a region configured to route an incoming airflow to the compressor section  12  and comprises a compressor bell mouth  24 . Half of the compressor bell mouth  24  has been removed in  FIG. 2  to illustrate various vanes and blades disposed at an interior region of the compressor section  12 , relative to a compressor section casing  26 . The compressor bell mouth  24  includes an outer surface  28  and an inner surface  30 , with the incoming airflow passing between these two surfaces. Typically, a plurality of support members  32  are operatively coupled to the outer surface  28  and the inner surface  30  for support. As shown in  FIG. 3 , the inlet  22  includes a strut  33  for supporting the structures and guiding the incoming airflow prior to passing over a plurality of inlet guide vanes (IGVs)  34 . 
     Referring to  FIG. 4 , the plurality of IGVs  34  is arranged in a circumferentially spaced manner in what is referred to as a stage. Downstream of one or more stages of the plurality of IGVs  34  are a plurality of rotor blades and a plurality of stator vanes. The stator vanes are generally fixed to a stator or a compressor section casing  26 , while the rotor blades are connected to the shaft  18 . The plurality of IGVs  34  is generally fixed as well, but may pitch around a radial axis to vary the direction or amount of incoming flow. The plurality of IGVs  34  is followed by a first stage of rotor blades  36 , which is in turn followed by a first stage of stator vanes  38 . Disposed downstream of the first stage of stator vanes  38  is a second stage of rotor blades  40 , which is followed by a second stage of stator vanes  42 . It can be appreciated that the compressor section  12  may include varying numbers of stages of rotor blades and stator vanes, depending on the particular application. 
     Referring to  FIGS. 5 and 6 , an airfoil  50  is shown and represents any of the above-described compressor section airfoils. In particular, the airfoil  50  may be the strut  33 , one of the plurality of IGVs  34 , and/or the stator vanes. Although illustrated and described in accordance with airfoils of the compressor section  12  and the inlet  22 , it is to be appreciated that airfoils in other parts of the gas turbine engine  10 , such as the turbine section  16 , may benefit from the embodiments of the airfoil  50  described below. 
     The airfoil  50  extends predominantly in an axial direction  52  from a leading edge  54  to a trailing edge  56 , although curvature of the airfoil  50  is common The airfoil  50  is defined in a radial direction  58  by a radially inner edge  60  and a radially outer edge  62 . In order to mitigate wake strength proximate regions downstream of the trailing edge  56 , a trailing edge geometry  64  is formed along the trailing edge  56 . The trailing edge geometry  64  comprises a multi-dimensional wave geometry that includes waves having curvature in multiple directions. In particular, the trailing edge geometry  64  is formed of at least one, but typically a plurality of wave segments  68  having simultaneous curvature in at least two directions. In the illustrated embodiment, the plurality of wave segments  68  includes simultaneous curvature in both the axial direction  52  and a circumferential direction  70 . In other words, as each of the plurality of wave segments  68  curve in one direction (i.e., axially or circumferentially), simultaneous curvature in another direction is made. 
     Varying degrees of curvature may be employed in different embodiments, depending on the particular flow characteristics of the particular application. As shown in  FIG. 8 , the axial angle of curvature θ or indentation of the plurality of wave segments  68  may vary. In one embodiment, the angle of curvature θ ranges from about 45° to about 80°. The plurality of wave segments  68  shown in the embodiment of  FIGS. 5 and 6  are radially oriented toward the radially outer edge  62 . However, in an alternative embodiment, a portion of the plurality of wave segments  68  are radially oriented toward the radially outer edge  62 , while a portion of the plurality of wave segments  68  are radially oriented toward the radially inner edge  60  ( FIG. 7 ). In yet another embodiment, all of the plurality of wave segments  68  are radially oriented toward the radially inner edge  60 . As shown, the number of wave segments may vary. Regardless of whether all or a portion of the plurality of wave segments  68  are radially oriented in a direction, the radial angle α of orientation may vary ( FIG. 8 ). In one embodiment, the radial angle α ranges from about 0° to about 35°. 
     In an alternative embodiment, the plurality of wave segments  68  comprises an alternating arrangement of wave segments. The alternating arrangement refers to a circumferentially curved wave segment followed by an axially curved wave segment, or vice versa. This arrangement is repeated along all or a portion of the trailing edge  56 . 
     Regardless of the precise configuration of the trailing edge geometry  64 , the plurality of wave segments  68  enhance flow mixing prior to routing of the airflow to regions downstream of the airfoil  50 . Efficient flow mixing reduces the effect of wake shed by the airfoil  50 , thereby reducing an unsteady pressure load on downstream blades. Exemplary airflow patterns facilitating flow mixing are illustrated in  FIGS. 6 and 7  and are referenced with numeral  80 . In addition to enhancing blade life, the wake strength reduction assists in having a reduced axial gap between various components, thereby reducing the overall axial length of the gas turbine engine  10 , and in particular the inlet  22  of the compressor section  12  for embodiments of airfoils disposed in the inlet  22  and/or the compressor section  12 . For example, as shown in  FIG. 3 , an inlet casing length  82 , an inlet outer diameter casing length  84 , a strut length  86 , a strut to IGV length  88 , and a flange to the first rotor stage  90  may all benefit from a reduction in axial length with the embodiments of the airfoil  50  describe above. 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.