Abstract:
Systems and methods involving vanes are provided. In this regard, a representative method for modifying the throat area between vanes of a gas turbine engine includes: directing a gas flow path of the gas turbine engine between a first vane and a second vane, wherein each of the first vane and the second vane has an outer surface and an interior; and emitting pressurized air from outlet ports communicating between the outer surface and the interior of the first vane, wherein the emitted pressurized air from the first vane modifies a throat area between the first vane and the second vane.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The invention relates to gas turbine engines. 
         [0003]    2. Description of the Related Art 
         [0004]    Gas turbine engines use compressors to compress gas for combustion. In particular, a compressor typically uses alternating sets of rotating blades and stationary vanes to compress gas. Gas flowing through such a compressor is forced between the sets and between adjacent blades and vanes of a given set. Similarly, after combustion, hot expanding gas drives a turbine that has sets of rotating blades and stationary vanes. 
       SUMMARY 
       [0005]    Systems and methods involving vanes are provided. In this regard, an exemplary embodiment of a gas turbine engine defining a gas flow path comprises: a first vane extending into the gas flow path and having: an interior operative to receive pressurized air; an outer surface; and outlet ports communicating between the outer surface and the interior of the first vane, the outlet ports being operative to receive the pressurized air from the interior and emit the pressurized air into the gas flow path such that a throat area defined, at least in part, by the first vane is modified. 
         [0006]    An exemplary embodiment of a vane assembly comprises: a first vane having: an outer surface; an interior defining a cavity operative to receive pressurized air; and outlet ports communicating between the outer surface and the cavity, the outlet ports being operative to receive the pressurized air from the cavity and emit the pressurized air through the outer surface a valve assembly operative to regulate the pressurized air emitted by the first vane. 
         [0007]    An exemplary embodiment of a method for modifying the throat area between vanes of a gas turbine engine comprises: directing a gas flow path of the gas turbine engine between a first vane and a second vane, wherein each of the first vane and the second vane has an outer surface and an interior; and emitting pressurized air from outlet ports communicating between the outer surface and the interior of the first vane, wherein the emitted pressurized air from the first vane modifies a throat area between the first vane and the second vane. 
         [0008]    Other systems, features, and/or advantages will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, features, and/or advantages be included within this description and protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic side cutaway view illustrating an exemplary embodiment of a turbine section of a gas turbine engine. 
           [0010]      FIG. 2  is a side cutaway view of an exemplary embodiment of a vane. 
           [0011]      FIG. 3  is a top cutaway view of an exemplary embodiment of vanes in a gas flow path. 
           [0012]      FIG. 4  is a top cutaway view of another exemplary embodiment of vanes in a gas flow path. 
           [0013]      FIG. 5  is a top cutaway view of another exemplary embodiment of vanes in a gas flow path. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Systems and methods involving vanes of gas turbine engines are provided. In this regard, several exemplary embodiments will be described. Notably, gas passing through a gas turbine engine enters a turbine that includes rotating blades and stationary vanes. The gas, following the gas flow path, is forced between adjacent vanes. The vanes are often shaped like airfoils and, therefore, have aerodynamic properties similar to airfoils. The flow of gas between adjacent vanes results in a throat area determined by, for example, the shape and relative position of the vanes. Often, the angle of the vanes relative to the gas flow path may be mechanically changed to vary the location and/or size of the throat area and alter the efficiency of the engine. However, it may be desirable, either additionally or alternatively, to alter the location and/or size of the throat area aerodynamically. In some embodiments, the gas turbine engine is configured as a turbofan. 
         [0015]    Referring now in detail to the drawings,  FIG. 1  is a schematic side view illustrating an exemplary embodiment of a turbine section  100  of a gas turbine engine. In turbine section  100 , rotating blades  104  are attached to a disk that is rotated by a shaft  106 . Stationary vanes  108  are attached to the casing of the engine between the blades  104 . In operation, gas enters the turbine section along gas flow path  102  and drives the blades  104 . The gas exits the turbine section  100  along gas flow path  102 . 
         [0016]      FIG. 2  is a simplified, side cutaway view of vane assembly  200  that includes a vane airfoil  202  and a valve assembly  208 . Note that vane airfoil  202  typically is mounted to and spans between an outer diameter vane platform and an inner diameter vane platform, neither of which is depicted in  FIG. 2 . 
         [0017]    In the embodiment of  FIG. 2 , valve assembly  208  includes a piston  204  and solenoid  220 , which is used to actuate the piston. Inlet ports  218  provide gas to the valve assembly so that actuation of the piston pressurizes the received gas. 
         [0018]    Vane airfoil  202  includes an interior cavity  214  that receives pressurized air from the inlet ports via the piston, and outlet ports  216  that are used to emit the pressurized air into the gas flow path. In particular, the gas emitted by the outlet ports  216  affects the throat area formed between vane airfoil  202  and an adjacent vane airfoil. This is in contrast to emission of pressurized gas from ports of a vane airfoil for performing film cooling. Notably, the pressure of the pressurized gas emitted from the outlet ports  216  is greater than that used for performing film cooling. As such, the pressurized gas from the outlet ports  216  urges the gas flow path, which flows about the vane airfoil during operation of the gas turbine engine, away from the exterior surface of the vane airfoil to a greater extent than that caused by pressurized gas involved in film cooling. In fact, in those embodiments that additionally include film cooling, the boundary layer formed by the film-cooling air also is urged away from the exterior of the vane airfoil. Typically, the pressure of the gas required to alter the throat is not available from the compressor alone. Thus, piston  204  is used in the embodiment of  FIG. 2  to increase the pressure of the gas provided to the outlet ports. In other embodiments, various other mechanisms could be used to increase the gas pressure. 
         [0019]    The shape of the vane assembly  200  illustrated in  FIG. 2  is merely an illustration of but one possible embodiment. The shape of the vane assembly  200  may vary depending on a variety of factors including, but not limited to, the component to which the vane assembly  200  is attached, the location of the vane assembly  200  in the gas turbine engine, the gas flow path around the vane assembly  200  at particular gas flow velocities, desired design characteristics of the gas turbine engine, and materials used in the fabrication of the gas turbine engine. 
         [0020]    In  FIG. 2 , a controller  212  also is provided. The controller  212  is used to open and close the valve assembly  208 . In one mode of operation, the valve assembly  208  is left open such that the outlet ports  216  emit a constant flow of pressurized air. Additionally, or alternatively, the valve assembly  208  may be opened and closed intermittently. In this mode of operation, the pressurized air may be emitted from the outlet ports  216  in pulses. Notably, operation in a pulsed mode allows the pressure of the pressurized air to increase prior to being emitted into a gas flow path. In some of these embodiments, the controller  212  may be set to control the frequency of the pulses of emitted pressurized air. Controlling the frequency of the pulses may be desirable because a change in the throat area based on a frequency of pulses may allow the aerodynamic characteristics of the engine to be adjusted. 
         [0021]    Specifically, the frequencies of the pulses may be controlled to modify one or more throat areas in a specific region of an engine to control local pressure ratios and/or local temperatures. The pulse frequencies may also be timed to adjust for resonance in the engine that may result in vane and blade vibrations. These pulses may be used to add a canceling frequency that may effectively cancel engine resonance, for example. 
         [0022]      FIG. 3  is a top cutaway view of a pair of vanes in an embodiment of a gas turbine engine. As shown in  FIG. 3 , gas is forced between the vanes  300  along gas flow path  302 , forming a throat area  304 . The shape of the adjacent vanes  300 , their proximity to each other, and the angle of incidence to the gas flow path  302  are possible factors that can influence the location and size of the throat area  304 . 
         [0023]      FIG. 4  depicts a top cutaway view of another embodiment of a vane assembly. In this embodiment, vanes  406  and  412  are adjacent vanes. Vane  406  has an interior cavity  404  that is connected to a pressurized air source (not shown). Outlet ports  410  are located on the surface of vane  406  and are in communication with interior cavity  404 . 
         [0024]    Pressurized air emitted from the outlet ports  410  in vane  406  defines a boundary layer  408  that has an aerodynamic effect on the gas flow path  402 . Notably, the boundary layer  408  associated with the pressurized air from the outlet ports modifies the location and/or size of the throat area  416 . Also note that the outlet ports of this embodiment are oriented such that the flow from the outlet ports is generally in a direction of the gas flow path. In other embodiments, however, the orientation can be different, such as by providing a perpendicular (see  FIG. 5 ) or counter flow (not shown). 
         [0025]    Modifying the throat area of an engine may affect the flow of gasses through the engine. For instance, such modifying can affect the pressure ratio of the compressor and change the relationship between the flow and the pressure ratio. For example, a lower flow rate can increase the pressure ratio. 
         [0026]      FIG. 5  depicts a top cutaway view of another embodiment of a vane assembly. In the illustrated embodiment, vane assembly  500  incorporates two adjacent vanes, a first vane  501  and a second vane  503 . The first vane  501  and the second vane  503  are spaced from each other to define a gas flow path  502 . The first vane  501  includes three chambers—a film-cooling chamber  504 , a suction side chamber  505  and a pressure side chamber  507 . The film-cooling chamber  504 , suction side chamber  505  and the pressure side chamber  507  include ports, such as ports  506 ,  509  and  511 , respectively. 
         [0027]    In operation, the film-cooling chamber  504  receives cooling pressurized air that is emitted from the associated ports, e.g., port  506 . This air creates a relatively thin boundary layer  530  that is located adjacent to the exterior of the vane  501  to serve as a barrier against the hot gas flowpath  502 . The suction side chamber  505  and the pressure side chamber  507  also receive pressurized air, which is at a higher pressure than that provided to chamber  504 , that is emitted from associated ports, e.g., ports  509  and  511 . The pressurized air emitted from chamber  507  creates a boundary layer  513  along the pressure surface  515  of the first vane  501  that affects the throat area  550 . Notably, the boundary layer  513  tends to urge the boundary layer  530  away from the pressure surface  515 , thereby causing the boundary layer  530  to dissipate and mix with the gas of the gas flow path  502 . 
         [0028]    The second vane  503  also includes three chambers—a film-cooling chamber  532 , a suction side chamber  510  and a pressure side chamber  512 . The film-cooling chamber  532 , suction side chamber  510  and the pressure side chamber  512  include ports, such as ports  534 ,  522  and  514 , respectively. 
         [0029]    In operation, the film-cooling chamber  532  receives cooling pressurized air that is emitted from the associated ports, e.g., port  534 . This air creates a relatively thin boundary layer  536  that is located adjacent to the exterior of the vane  503 . The suction side chamber  510  and the pressure side chamber  512  also receive pressurized air, which is at a higher pressure than that provided to chamber  534 , that is emitted from associated ports, e.g., ports  522  and  514 . The pressurized air emitted from chamber  510  creates a boundary layer  525  along the suction surface  506  of the vane  503  that affects the throat area  550 . Notably, the boundary layer  525  tends to urge the boundary layer  536  away from the suction surface  506 , thereby causing the boundary layer  536  to dissipate and mix with the gas of the gas flow path  502 . 
         [0030]    The suction side chambers  505  and  510  and the pressure side chambers  507  and  512  may be separate and unconnected to each other so that the air emitted from each of the chambers may be controlled independently. Alternatively, the suction side chambers  505  and  510  and the pressure side chambers  507  and  512  may be in communication, and therefore, dependently controlled. 
         [0031]    It should be emphasized that the above-described embodiments are merely possible examples of implementations. Many variations and modifications may be made to the above-described embodiments. By way of example, although a solenoid is described with respect to the embodiment of  FIG. 2 , other types of actuation could be used. As another example, a pressurized line could be used to provide gas to a valve assembly. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.