Abstract:
Systems and methods for altering airflow to gas turbine engines are provided. In this regard, a representative system includes a gas turbine engine inlet having a slat, the slat being movable between a retracted position and an extended position. In the extended position, the slat increases an effective diameter of the inlet compared to the diameter of the inlet when in the retracted position.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    This disclosure generally relates to gas turbine engines. 
         [0003]    2. Description of the Related Art 
         [0004]    Aircraft engine nacelle inlets are designed to meet many diverse flight conditions such as take-off, crosswind, climb, cruise and windmill. These disparate flight conditions result in competing design considerations often times resulting in a nacelle configuration that is designed for less than optimal performance at cruise conditions. By way of example, the inlet diameter of a typical nacelle typically is 10% to 20% larger than is generally considered optimal at cruise conditions. 
       SUMMARY 
       [0005]    Systems and methods for altering airflow to gas turbine engines are provided. In this regard, an exemplary embodiment of a method comprises selectively increasing an effective diameter of a nacelle inlet while a gas turbine engine mounted within the nacelle is operating. 
         [0006]    An exemplary embodiment of a system comprises: a gas turbine engine inlet having a slat, the slat being movable between a retracted position and an extended position; in the extended position, the slat increasing an effective diameter of the inlet compared to the diameter of the inlet when in the retracted position. 
         [0007]    Another exemplary embodiment of a system comprises: a slat configured as an annular segment; and a slat actuator operative to move the slat between a retracted position and an extended position. 
         [0008]    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 
         [0009]    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. 
           [0010]      FIG. 1  is a schematic diagram depicting an embodiment of a system for altering inlet airflow to a gas turbine engine. 
           [0011]      FIG. 2  is a schematic diagram of the embodiment of  FIG. 1 , with inlet slats shown in extended positions. 
           [0012]      FIG. 3  is a schematic view of another embodiment of a system for altering inlet airflow to a gas turbine engine. 
           [0013]      FIG. 4  is a schematic diagram of another embodiment of a system for altering inlet airflow to a gas turbine engine, showing detail of the pneumatic slat actuator and anti-icing components located in the inlet plenum. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Systems and methods for altering inlet airflow to gas turbine engines are provided. In this regard, several exemplary embodiments will be described. Specifically, some embodiments involve the use of slats located about the inlet of a nacelle. In some embodiments, the slats are pneumatically actuated by bleed air that also can be used to provide anti-icing for the inlet. The slats can be extended, such as during take-off and landing configurations that typically involve an increased need for inlet airflow. However, the slats can be fully retracted, such as during cruise, thereby reducing drag of the nacelle. Notably, the use of such slats can enable an overall smaller nacelle to be used, e.g., a nacelle that is optimally designed for cruise conditions. 
         [0015]      FIG. 1  is a schematic diagram depicting an embodiment of a system for altering inlet airflow to a gas turbine engine. As shown in  FIG. 1 , system  100  includes a power plant that incorporates a nacelle  102  and a gas turbine engine  104 . It should be noted that although the gas turbine engine is configured as a turbofan in this embodiment, other types of gas turbine engines can be used. 
         [0016]    Nacelle  102  is attached to a pylon  106  that mounts the power plant to a wing of an aircraft (not shown). Nacelle  102  includes an inlet  108  that includes a leading edge  112 . The inlet is configured to direct a flow of air toward an intake of the engine  104 , which includes a fan  110 . Aft of the leading edge on an exterior of the nacelle is an inlet nose cowl  114 . Other portions of the nacelle are not relevant to this discussion and will not be described in greater detail. 
         [0017]    The embodiment of  FIG. 1  also includes inlet slats, e.g., slat  120 , that are shown in their retracted positions in  FIG. 1 . The inlet slats are generally located at the lip of the nacelle and generally conform to the shape of the lip and inlet. Thus, in this embodiment, each slat is configured as a compound annular segment, i.e., each slat is annular along its length as well as in cross-section. In other embodiments, various other shapes can be used. 
         [0018]    In  FIG. 2 , the inlet slats are shown in their respective extended positions. In the extended positions, the slats generally increase an outer diameter of the inlet, thereby enabling an increase in airflow to the gas turbine engine. In operation, the slats are typically deployed to their extended positions when an increase in airflow is desired, such as during takeoff and/or landing. During cruise conditions, however, the increase in surface area and corresponding profile drag attributable to the extended slats may be undesirable. Therefore, during cruise conditions, for example, the slats typically can be retracted, thereby accommodating an inlet design that is more optimal for cruise conditions. 
         [0019]    It should be noted that although the slats in the embodiment of  FIGS. 1 and 2  are configured as segments that separate from each other when extended, various other configurations can be used. By way of example, slats that overlap each other even when extended could be used. Additionally or alternatively, various other techniques can be used that alter the thickness of the nacelle lip. Notably, selective altering of the inner diameter and/or outer diameter of the nacelle lip can affect airflow into the engine. In this regard, geometric changes that avoid flow separation are typically preferred. 
         [0020]      FIG. 3  schematically depicts another embodiment of a system for altering inlet airflow to a gas turbine engine. As shown in  FIG. 3 , system  300  incorporates a gas turbine engine  302  about which a nacelle  304  is positioned. A lip  306  of the nacelle incorporates extendable slats, e.g., slat  310 , that can be moved from retracted positions (shown in  FIG. 3 ) to extended positions (shown in  FIG. 4 ). It should be noted that the lip of the nacelle defines an interior annular plenum  312  through which bleed air can be routed for providing inlet anti-icing, for example. In this regard, reference is made to the schematic diagram of  FIG. 4 , which depicts a portion of plenum  312  and an inlet slat in greater detail. 
         [0021]    As shown in  FIG. 4 , plenum  312  is defined by spaced inner and outer surfaces  314 ,  316  of the nacelle that interconnect at the leading edge  320 . In this embodiment, various components are located within the plenum, including a pneumatic actuator  322  that is operative to alter a position of slat  310 . Specifically, the pneumatic actuator is operative to move the slat between a retracted position (indicated by phantom lines in  FIG. 4 ) and an extended position  324 . Notably, in some embodiments, various intermediate positions between the extended and retracted positions can be provided. 
         [0022]    In the embodiment of  FIG. 4 , engine bleed air is provided to the pneumatic actuator  322  via a bleed air regulator  326 . The bleed air regulator also provides bleed air to inlet anti-icing components  328 , such as valves and manifolds, which are configured to heat the inlet in order to prevent ice build-up. Notably, the bleed air regulator receives a supply of bleed air and regulates that bleed air for use by the pneumatic actuator and anti-icing components. Clearly, various allocations of bleed air supply among the components that use that supply can be accommodated by the regulator. 
         [0023]    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.