Abstract:
Systems and methods involving variable throat area vanes are provided. In this regard, a representative gas turbine engine includes: a vane extending into a gas flow path and having: an interior operative to receive pressurized air; a pressure surface portion; and a first port communicating between the interior and pressure surface portion, the first port being operative to receive the pressurized air from the interior and emit the pressurized air, wherein the emitted pressurized air displaces the gas flow path such that a throat area defined, at least in part, by the vane is modified.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The disclosure 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 stages, each of which incorporates a row of rotating blades and a row of stationary vanes to compress gas. Gas flowing through such a compressor is forced between the rows and between adjacent blades and vanes of a given row. Similarly, after combustion, hot expanding gas drives a turbine that uses stages, each of which incorporates a row of stationary vanes and a row of rotating blades. 
         [0005]    The flow rate through the turbine is set by adjusting the throat areas of the vanes and/or blades. Modifying the throat areas has the effect of changing the relationship between flow rate and pressure ratio of the engine. Changing the pressure ratio tends to have an effect on the operating temperatures of the engine and, therefore, affects engine performance. Therefore, manipulation of the throat areas may be desirable to adjust the aerodynamic characteristics of the gas turbine engine under certain operating conditions. 
       SUMMARY 
       [0006]    Systems and methods involving variable throat area vanes are provided. In this regard, an exemplary embodiment of a gas turbine engine comprises: a vane extending into a gas flow path and having: an interior operative to receive pressurized air; a pressure surface portion; and a first port communicating between the interior and pressure surface portion, the first port being operative to receive the pressurized air from the interior and emit the pressurized air, wherein the emitted pressurized air displaces the gas flow path such that a throat area defined, at least in part, by the vane is modified. 
         [0007]    An exemplary embodiment of a vane assembly comprises: a vane having: a pressure surface portion; a suction surface portion; an interior defining a cavity operative to receive pressurized air; and a port communicating between the interior and the pressure surface portion, the port being operative to receive pressurized air from the interior and emit the pressurized air through the pressure surface portion; and an adjacent vane such that relative placement of the vane and the adjacent vane define a throat area; wherein the pressurized air emitted from the port of the vane displaces the gas flow path such that the throat area is modified. 
         [0008]    An exemplary embodiment of a method for displacing the gas flow path between turbine vanes comprises: directing a gas flow path of a gas turbine engine between a vane and an adjacent vane of a turbine stage, each of the vane and the adjacent vane having an outer surface and an interior; and receiving pressurized air from a port communicating between the outer surface and the interior of the vane such that the emitted pressurized air from the vane displaces the gas flow path and modifies a throat area between the vane and the adjacent vane. 
         [0009]    Other systems, methods, features and/or advantages of this disclosure 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, methods, features and/or advantages be included within this description and be within the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0011]      FIG. 1  is a side cut-away view of an exemplary embodiment of a gas turbine engine. 
           [0012]      FIG. 2  is a top cut-away view of an exemplary embodiment of a vane assembly. 
           [0013]      FIG. 3  is a top cut-away view of an alternative exemplary embodiment of a vane assembly. 
           [0014]      FIG. 4  is a partially cut-away, isometric view of an alternative exemplary embodiment of a vane and platform assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    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 shaped like airfoils and, therefore, have aerodynamic properties similar to airfoils. The flow of gas between adjacent vanes results in a minimum throat area determined by, for example, the shape and relative proximity of the vanes, and the velocity and volume of gases passing between the vanes. Often, the shape of the vanes and/or 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 operating characteristics of the engine. However, it may be desirable, either additionally or alternatively, to alter the location and/or size of the throat area aerodynamically. For the purposes of this disclosure, throat area is defined as the minimum flow area, corresponding to the limiting streamlines, established by the shape and placement of the vanes and associated platform surfaces. 
         [0016]    Referring now in detail to the drawings,  FIG. 1  is a schematic side view illustrating an exemplary embodiment of a gas turbine engine  100  that incorporates variable turbine vanes  118 . As shown in  FIG. 1 , engine  100  includes a compression section  104  that is linked to a power turbine section  108  by a shaft  105 . Bleed air path  116  routes pressurized air to variable vanes  118 . 
         [0017]    In operation, gas  110  enters the compression section  104  and is compressed. The compressed gas then travels along gas flow path  114  and is mixed with fuel and combusted in the combustion section  106 . The gas then enters the turbine section  108  and exits the engine as exhaust gas  112 . 
         [0018]    Pressurized air, such as bleed air, may be bled from the gas flow path and routed around the combustion section  106  to provide pressurized air to the variable vanes  118  via bleed air path  116 . The pressurized air is used to displace the gas aerodynamically along the gas flow path, thereby changing the throat area between adjacent vanes. 
         [0019]      FIG. 2  is a top view cutaway of an exemplary embodiment of adjacent vanes  200  in a row that includes a vane  202  and a vane  204 . Vanes  202  and  204  are attached to a stationary portion of the engine such as a case structure (not shown). Vane  202  has a suction surface portion  206  and a pressure surface portion  208 . Vane  204  has a suction surface portion  210  and a pressure surface portion  212 . In operation, gasses flow along gas flow path  214  between the vane  202  and the vane  204  and in very close proximity to the suction  210  and pressure  208  surfaces. The vane  202  and the vane  204  define a throat area  216 , which is the minimal area between the vanes  202 ,  204 . The shape of the vane  202  and the vane  204 , their proximity to each other, and the stagger angle of the vane to the gas flow path  214  are possible factors that can influence the location and size of the throat area  216 . Although the gas flow path  214  is shown flowing from right to left in the figures, it is understood that vanes  202  and  204  could be mirrored with the gas flow path  214  flowing from left to right. 
         [0020]      FIG. 3  is a top cutaway view of an exemplary embodiment of vanes  300 . A vane  302  has a suction surface portion  306  and a pressure surface portion  308 . The vane  302  has an interior cavity  320  and a port  322 , which communicates between the interior cavity  320  and the pressure surface portion  308 . A vane  304  has a suction surface portion  310  and a pressure surface portion  312 . The vane  304  has an interior cavity  324  and a port  326 , which communicates between the interior cavity  324  and the suction portion  310 . The ports  322  and  326  may be located near the minimal throat area  316 . 
         [0021]    In operation, the vane  302  and the vane  304  have inner cavities  320  and  324  that receive pressurized air, and emit the pressurized air through ports  322  and  326  in a direction substantially counter to the gas flow path  314 . The emitted pressurized air forms regions of recirculating air  328  and  330  that displace the gasses in the gas flow path  314  away from the pressure surface portion  308  of vane  302  and away from the suction surface portion  310  of the vane  304  near the throat area  316 . This displacement causes the throat area to be made effectively smaller resulting in a modified gas flow path  332 . 
         [0022]    Additionally, it may be desirable to emit the pressurized air in a direction substantially perpendicular to the gas flow path  314  or in a direction down stream of the gas flow path  314 . Another alternative embodiment of the vanes  300  may include vanes  302  and  304  that have ports on both the pressure surface portions and suction surface portions of the vanes. 
         [0023]    The shape of the vanes  302  and  304  illustrated in  FIG. 3  is merely an illustration of but one possible embodiment. The shape of the vanes  302  and  304  may vary depending on a variety of factors including, but not limited to, the component to which the vanes  302  and  304  are attached, the location of the vanes  302  and  304  in the gas turbine engine, the gas flow path around the vanes  302  and  304  at particular gas flow velocities, desired design characteristics of the gas turbine engine, and materials used in the fabrication of the gas turbine engine. 
         [0024]      FIG. 4  illustrates a partially cut-away, isometric view of an assembly  400  of vanes that includes a platform. In this alternative embodiment, a vane  402  and a vane  404  are depicted attached to a platform  410 . Notably, platform  410  is an outer diameter platform that is attached to the radially outermost ends of the vanes. Platform  410  includes a cavity  412  and a plurality of ports (e.g., port  416 ) located in a vicinity of the throat that communicate with the cavity and the inner flow path of the outer diameter platform. An inner diameter platform that is attached to the radially innermost terminating ends of the vanes is not depicted. 
         [0025]    In operation, the cavity  412  may receive pressurized air  420  and emit the pressurized air from the plurality of platform ports. The emitted pressurized air provided through the ports displaces the gas flow path by forming a recirculation region (not shown), thereby modifying the throat area (not shown) defined by vanes  402  and  404 . Specifically, the throat area is modified in the radial dimension defined by the lengths of adjacent vanes between the inner and outer platforms. This is in contrast to modification of a throat area, such as depicted in  FIG. 3 , which occurs with respect to the width of an annular segment extending between adjacent vanes. 
         [0026]    Additionally or alternatively, some embodiments can include inner diameter platforms that are configured to modify throat areas. 
         [0027]    It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.