Abstract:
Systems and methods involving struts are provided. In this regard, a representative system includes a gas turbine engine defining a gas flow path. The gas turbine engine comprises a strut extending into the gas flow path. The strut has an interior operative to receive pressurized air, an outer surface, and ports communicating between the outer surface and the interior of the strut, the ports are operative to receive the pressurized air from the interior and emit the pressurized air into the gas flow path such that an effective aerodynamic length of the strut along the gas flow path is increased.

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 incorporate rotating components. For example, rotating disks that mount blades are used to compress air for combustion or expand gas for extraction of power. In this regard, struts may be used to mount bearings that support such rotating components. 
         [0005]    In some applications, bearings often require oil for lubrication and cooling. Thus, the required shape of a strut may be driven by the desire to pass oil through an inner cavity of the strut to the bearing that the strut supports. Typically, the required shape is not an aerodynamically desirable shape. 
       SUMMARY 
       [0006]    Systems and methods involving struts are provided. In this regard, an exemplary embodiment of such a system comprises a gas turbine engine defining a gas flow path. The gas turbine engine comprises a strut extending into the gas flow path. The strut has an interior cavity operative to receive pressurized air, an outer surface, and ports communicating between the outer surface and the interior of the strut, the ports are operative to receive the pressurized air from the interior and emit the pressurized air into the gas flow path such that an aerodynamic length of the strut along the gas flow path is increased. 
         [0007]    An exemplary embodiment of a strut for supporting a rotating body has an outer surface, an interior defining a first cavity this is operative to receive pressurized oil, and a second cavity that is operative to receive pressurized air. The strut also has ports communicating between the outer surface and the second cavity, the ports are operative to receive the pressurized air from the cavity and emit the pressurized air through the outer surface. 
         [0008]    An exemplary embodiment of a strut assembly comprises a bearing, oil, and a strut. The strut has an outer surface, an interior defining a first cavity that is operative to receive pressurized oil and a second cavity that is operative to receive pressurized air, and ports communicating between the outer surface and the second cavity. The ports are operative to receive the pressurized air from the cavity and emit the pressurized air through the outer surface. 
         [0009]    An embodiment of a method of effectively increasing the aerodynamic length of a strut disposed in a fluid stream comprises the steps of: providing a strut with an interior cavity fluidly coupled to an outer strut surface by one or more ports; introducing a second fluid into the interior cavity at a pressure that is greater than the fluid stream pressure; and expelling the second fluid through the outer surface and into the fluid stream via the one or more ports such that the aerodynamic length of the strut is effectively increased with respect to the fluid stream. 
         [0010]    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 
         [0011]      FIG. 1  is a side view illustrating exemplary embodiment of a gas turbine engine and aerodynamic struts. 
           [0012]      FIG. 2  is a perspective view of an exemplary embodiment of an aerodynamic strut. 
           [0013]      FIG. 3  is a perspective view of another exemplary embodiment of an aerodynamic strut. 
           [0014]      FIG. 4  is a top view of an exemplary embodiment of an aerodynamic strut in the gas flow path. 
           [0015]      FIG. 5  is a top view of an exemplary embodiment of an aerodynamic strut illustrating the impact of the fluid being expelled by the ports. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Systems involving aerodynamic struts are provided. In this regard, several exemplary embodiments will be described. Notably, some design constraints may require a component located along a gas flow path to be rather wide and, therefore, aerodynamically undesirable. For instance, a strut may be required to carry lubrication oil to bearings, hydraulic fluids or instrumentation cables. Often, this design constraint results in a strut having an aspect ratio (length to width) of less than 2:1. Such an aspect ratio can cause gas traveling along the gas flow path to separate from the strut thereby causing significant aerodynamic loss. Therefore, it may be desirable to effectively lengthen the aerodynamic length of the strut along the gas flow path such that the strut has an aspect ratio of 2:1 or greater, such as 4:1 or greater, for example. 
         [0017]    Referring now in detail to the drawings,  FIG. 1  is a simplified schematic side view illustrating an exemplary embodiment of a gas turbine engine  100  that incorporates struts  102 . In this embodiment, the struts support bearings  103 . As shown in  FIG. 1 , engine  100  includes a compression section  104  that is linked to a turbine section  108  by a central shaft  105 . The shaft  105  is supported by bearings  103  that are held by struts  102 . Bleed air paths  116  route pressurized air to struts  102  from the compression section  104 . 
         [0018]    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 a propulsive exhaust gas  112 . 
         [0019]    Pressurized air, such as bleed air, may be bled from the gas flow path forward of the combustion section  106  and routed to provide pressurized air to the struts  102  via bleed air paths  116 . The pressurized air is used to effectively lengthen the struts  102  aerodynamically along the gas flow path, thereby increasing the aerodynamic efficiency of the struts  102 . 
         [0020]      FIG. 2  is a perspective cutaway view of a strut  102  that may support components of a turbine engine such as bearings (not shown). Strut  102  comprises an outer surface  208  and an interior cavity  204 . Ports  206  are located on the outer surface  208 . The ports are in communication with the interior  204  and the outer surface  208  of the strut  102 . 
         [0021]    A pressurized air source provides pressurized air  202  that flows through the interior  204  of the strut  102 . The pressurized air  202  may then be emitted into and expelled from ports  206 . This is done to effectively lengthen the strut  102  aerodynamically along the gas flow path (not shown). Specifically, the pressurized air  102  urges gas travelling along the gas flow path to form a recirculation bubble that, in turn, causes the main flow to follow the shape created by the front of the strut and the extended shape created by the recirculation bubble. 
         [0022]    The shape of the strut  102  illustrated in  FIG. 2  is merely an illustration of but one possible embodiment. The shape of the strut  102  may vary depending on a variety of factors including, but not limited to, the component that the strut  102  is supporting, the location of the strut  102  in the gas turbine engine, the gas flow path around the strut  102  at particular gas flow velocities, desired design characteristics of the gas turbine engine, and materials used in the fabrication of the gas turbine engine. 
         [0023]      FIG. 3  depicts another embodiment of a strut. As shown in  FIG. 3 , strut  300  has a first interior cavity  302  and a second interior cavity  306 . The second interior cavity  306  is in communication with ports, such as ports  310 ,  312 ,  314 ,  316 , and  318 . The representative ports illustrated in  FIG. 3  are shown in a variety of shapes such as wedge-shaped ports  310 , round ports  312 , slot-shaped ports  314 , and chevron shaped ports  318 . Additionally, the ports may be skewed ports  316  that are skewed on an axis that is not parallel to the gas flow path. The shapes, locations and orientations of the ports shown are illustrative of possible embodiments. However, the ports are not limited to those shapes, locations, and orientations shown. 
         [0024]    The location of one or more of the ports  310 ,  312 ,  314 ,  316 , and  318  could be dependent upon the aerodynamic nature of the strut  300 . For example, the shape of the strut  300 , and the effects on the gas flow path at a variety of gas flow velocities may influence the locations, shapes, and orientations of the ports. Thus, the location of the ports could be anywhere on the outer surface  308  of the strut  300  to effect the gas flow path around the strut  300  and increase the aerodynamic efficiency of the strut along the gas flow path. 
         [0025]    A fillet may be located between the strut and the surface to which the strut is attached. Fillet  311  may also have an effect on the gas flow path around the strut  300 . Therefore, one or more of the ports may be orientated or positioned to adjust for aerodynamic inefficiencies caused by filet  311  as well. 
         [0026]    Cavity  306  may carry oil, or may be used as a conduit for oil carrying tubes (not shown). In some embodiments, these tubes may be insulated. Additionally, or alternatively, interior cavity  306  may be insulated. 
         [0027]    The size of cavity  306  may affect the design characteristics of strut  300  by causing the strut to have an aerodynamically undesirable width. Pressurized air  301  may enter space  302  and be emitted into the gas flow path of the engine, thereby increasing the effective aerodynamic length of the strut  300  along the gas flow path. 
         [0028]      FIG. 4  is a schematic top view of a strut  400  without ports for emitting pressurized air. In this embodiment, the gas flow path  410  flows around the outer surface  402  of the strut  400 . Note that the main flow separates from the outer surface in a vicinity of the location of maximum thickness of the strut. 
         [0029]      FIG. 5  is a top view of a strut  500  having ports for emitting pressurized air. This embodiment includes an interior  502  and ports  504 . Pressurized air is emitted from ports  504  and creates a recirculation bubble at location  506  along the outer surface  508  of the strut  500 . The recirculation bubble influences the gas flow path depicted by the arrows  510 . 
         [0030]    In the embodiment of  FIG. 5 , the downstream portion  512  of the strut  500  has a tapered shape formed by opposing concave surfaces. This shape can have the effect of trapping the recirculation bubbles along the outer surface  508  of the strut  500 , thereby urging gas travelling along the gas flow path  510  away from the outer surface  508  of the strut  500 . This effectively aerodynamically lengthens the strut  500  in a direction along the gas flow path  410 . This effectively causes the strut  500  to have less of an adverse impact on the gas flow path. The downstream portions  512  of the strut  500  are not limited to concave shapes, but may be one of a variety of shapes. 
         [0031]    In this regard, effectively increasing the aerodynamic length of a strut disposed in a fluid stream can incorporate the following. First, a strut with an interior cavity fluidly coupled to an outer strut surface by one or more ports is provided. Second, a fluid (which may be the same or different from the fluid that forms the fluid stream prior to reaching the strut) is provided into the interior cavity at a pressure that is greater than the fluid stream pressure. Thereafter, the fluid is expelled through the outer surface and into the fluid stream via the one or more ports such that the aerodynamic length of the strut is effectively increased with respect to the fluid stream. 
         [0032]    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 the ports are generally directed downstream with respect to the gas flow path, ports can be oriented in a generally upstream direction or perpendicular to the gas flow path in other embodiments. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.