Abstract:
A sealing system for a gas turbine engine includes a first surface and a second surface spaced a dimension away from the first surface defining a gap through which a fluid can flow. At least one recess is formed in one of the first surface and the second surface and is oriented such that the fluid flow through the gap crosses the at least one recess. The recess is configured to restrict the fluid flow through the gap in comparison to if the at least one recess were not present, all other things being equal.

Description:
BACKGROUND 
       [0001]    This disclosure relates to a gas turbine engine, and more particularly to gaspath leakage seals for gas turbine engines. 
         [0002]    Gas turbine engines, such as those used to power modern commercial and military aircrafts, generally include a compressor section to pressurize an airflow, a combustor section for burning hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases. The airflow flows along a gas path through the gas turbine engine. Along the gas path, there are many potential leakage paths, such as joints between mating components, that can reduce the efficiency of the system. 
         [0003]    Traditionally, the leakage paths are addressed by the inclusion of physical seals, such as rope seals or W seals between the mating parts. Such methods, however, suffer challenges due to durability, FOD (foreign object damage), sealing effectiveness, cost, and design space/size restrictions. Some leakage paths are only 0.010″ between mating surfaces with no extra design space to fit a physical seal. Other locations are very close to the gas path where FOD is a real concern, particularly for fragile hardware like rope, or W seals. These restrictions often lead to designs where attempting to minimize gaps has often been a selected design criteria. 
       SUMMARY 
       [0004]    In one embodiment, a sealing system for a gas turbine engine includes a first surface and a second surface spaced a dimension away from the first surface defining a gap through which a fluid can flow. At least one recess is formed in one of the first surface and the second surface and is oriented such that the fluid flow through the gap crosses the at least one recess. The recess is configured to restrict the fluid flow through the gap in comparison to if the at least one recess were not present, all other things being equal. 
         [0005]    Additionally or alternatively, in this or other embodiments the at least one recess forms sharp corners where the at least one recess intersects with the one of the first surface or the second surface in which the recess is formed. 
         [0006]    Additionally or alternatively, in this or other embodiments the at least one recess is at least two recesses, a first of the two recesses being formed in the first surface and a second of the two recesses being formed in the second surface. 
         [0007]    Additionally or alternatively, in this or other embodiments the first of the at least two recesses is positioned symmetrically across the gap from the second of the two recesses. 
         [0008]    Additionally or alternatively, in this or other embodiments the first of the at least two recesses is positioned asymmetrically across the gap from the second of the two recesses. 
         [0009]    Additionally or alternatively, in this or other embodiments the first of the two recesses is dimensionally identical to the second of the two recesses. 
         [0010]    Additionally or alternatively, in this or other embodiments the at least two recesses is at least four recesses, with at least two recesses located at the first surface and at least two recesses located at the second surface. 
         [0011]    Additionally or alternatively, in this or other embodiments the reduction in the fluid flow through the gap is restricted via rapid expansion and contraction of the fluid flow at the at least one recess. 
         [0012]    In another embodiment, a gas turbine engine includes a first gas turbine engine component having a first surface and a second gas turbine engine component having a second surface. The second gas turbine engine component positioned such that the second surface and the first surface define a gap therebetween. At least one recess is formed in one of the first surface and the second surface and is oriented such that a fluid flow through the gap crosses the at least one recess. The recess is configured to restrict the fluid flow through the gap in comparison to if the at least one recess were not present, all other things being equal. 
         [0013]    Additionally or alternatively, in this or other embodiments the at least one recess forms sharp corners where the at least one recess intersects with the one of the first surface or the second surface in which the recess is formed. 
         [0014]    Additionally or alternatively, in this or other embodiments the at least one recess is at least two recesses, a first of the two recesses being formed in the first surface and a second of the two recesses being formed in the second surface. 
         [0015]    Additionally or alternatively, in this or other embodiments the first of the at least two recesses is positioned symmetrically across the gap from the second of the two recesses. 
         [0016]    Additionally or alternatively, in this or other embodiments the first of the at least two recesses is positioned asymmetrically across the gap from the second of the two recesses. 
         [0017]    Additionally or alternatively, in this or other embodiments the first of the two recesses is dimensionally identical to the second of the two recesses. 
         [0018]    Additionally or alternatively, in this or other embodiments the at least two recesses is at least four recesses, with at least two recesses located at the first surface and at least two recesses located at the second surface. 
         [0019]    Additionally or alternatively, in this or other embodiments the reduction in the fluid flow through the gap is restricted via rapid expansion and contraction of the fluid flow at the at least one recess. 
         [0020]    In yet another embodiment, a method of sealing fluid flowing in a gas turbine engine includes abruptly enlarging and then closing a dimension between a first surface of a first gas turbine engine component and a second surface of a second gas turbine engine component along a length of a gap between the first surface and the second surface. A fluid flowing in the gap is expanded and contracted via the abrupt enlargement and closing of the dimension. The flow of fluid through the gap is restricted via the expansion and contraction of the fluid along the gap. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The subject matter which is regarded as the present disclosure 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 present disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0022]      FIG. 1  illustrates a schematic cross-sectional view of an embodiment of a gas turbine engine; 
           [0023]      FIG. 2  illustrates an example of a component interface in a gas turbine engine; 
           [0024]      FIG. 3  illustrates an embodiment of a sealing arrangement at a component interface of a gas turbine engine; 
           [0025]      FIG. 4  illustrates another embodiment of a sealing arrangement at a component interface of a gas turbine engine; 
           [0026]      FIG. 5  illustrates yet another embodiment of a sealing arrangement at a component interface of a gas turbine engine; 
           [0027]      FIG. 6  illustrates still another embodiment of a sealing arrangement at a component interface of a gas turbine engine. 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 1  is a schematic illustration of a gas turbine engine  10 . The gas turbine engine generally has a fan  12  through which ambient air is propelled in the direction of arrow  14 , a compressor  16  for pressurizing the air received from the fan  12  and a combustor  18  wherein the compressed air is mixed with fuel and ignited for generating combustion gases. 
         [0029]    The gas turbine engine  10  further comprises a turbine section  20  for extracting energy from the combustion gases. Fuel is injected into the combustor  18  of the gas turbine engine  10  for mixing with the compressed air from the compressor  16  and ignition of the resultant mixture. The fan  12 , compressor  16 , combustor  18 , and turbine  20  are typically all concentric about a common central longitudinal axis of the gas turbine engine  10 . In some embodiments, the turbine  20  includes one or more turbine stators  22  and one or more turbine rotors  24 . 
         [0030]    The gas turbine engine  10  may further comprise a low pressure compressor located upstream of a high pressure compressor and a high pressure turbine located upstream of a low pressure turbine. For example, the compressor  16  may be a multi-stage compressor  16  that has a low-pressure compressor and a high-pressure compressor and the turbine  20  may be a multistage turbine  20  that has a high-pressure turbine and a low-pressure turbine. In one embodiment, the low-pressure compressor is connected to the low-pressure turbine and the high pressure compressor is connected to the high-pressure turbine. 
         [0031]    The gas turbine engine  10  includes mating parts with gaps therebetween, either by design and/or as a result of manufacturing tolerances. Referring to  FIG. 2 , gaps may exist, for example, between a first component, such as a turbine stator segment  22 , and a second component, such as a turbine outer air seal  26 , or between circumferentially adjacent stator segments  22  and outer air seals  26 . While turbine stator and outer air seals are described herein, it is to be appreciated that the first component and second component may denote any one of many adjacent component arrangements in the gas turbine engine  10 , which may result in a leakage path between the first component and second component. These components may reside in the turbine  20 , the compressor  16 , combustor  18 , or other portion of the gas turbine engine  10 . 
         [0032]    Shown in  FIG. 3  is a nonlimiting embodiment of a sealing arrangement between the stator segment  22  and the outer air seal  26 . The stator segment  22  includes stator surface  28 , which is axially offset some dimension from an air seal surface  30  of the outer air seal  26 , defining a gap  32  between the stator surface  28  and the air seal surface  30 . In some embodiments, the gap is about 0.010″ or less. In other embodiments, the gap  32  is greater than 0.010″. 
         [0033]    A stator recess  34  is located along the stator surface  28  at the gap  32 , and extends inwardly into the stator segment  22  to a stator recess depth  36 . Similarly, an air seal recess  38  is located along the air seal surface  30  at the gap  32 , opposite to the stator recess  34 . The stator recess  34  and the air seal recess  38  define an expansion chamber  40  across the gap  32 , such that airflow  42  flowing through the gap  32  expands at the expansion chamber  40 . Downstream of the expansion chamber  40 , the airflow is then quickly contracted again at the gap  32 . This expansion and contraction of the airflow  42  in quick succession induces losses in the airflow  42  to restrict airflow  42  through the gap  32 . The airflow  42  is unable to follow the abrupt change in boundary at the stator recess  34 , leading to pockets of turbulent eddys at the stator recess  34 , which dissipates mechanical energy of the airflow  42 . When the mechanical energy of the airflow  42  is reduced, driving force, speed, pressure, total leakage and so forth are reduced. The stator recess  34  and the air seal recess  38  may be symmetrically located directly opposite each other across the gap  32 , or alternatively as shown in  FIG. 4  may be asymmetrically located, e.g., staggered relative to each other along the gap  32 . 
         [0034]    Referring again to  FIG. 3 , the stator recess  34  and the air seal recess  38  may have equal recess widths  44  and/or equal recess depths  36 , or may be differently shaped as selected. A stator transition  46  between the stator surface  28  and the stator recess  38  is defined by a sharp corner, as is an air seal transition  48 . The sharp transitions aid in achieving a quick expansion and contraction of the airflow  32 . The stator recess  34  and/or the air seal recess  38  may include a fillet  50  at the recess depth  36  to reduce stresses in the stator recess  34  and/or the air seal recess  38 . 
         [0035]    Examples of alternate embodiments of seal arrangements are illustrated in  FIG. 5  and  FIG. 6 . In  FIG. 5 , the seal arrangement includes only one recess, either the stator recess  34  or the air seal recess  38 . Referring now to  FIG. 6 , in another embodiment multiple pairs of stator recesses  34  and air seal recesses  38  are utilized to define two or more expansion chambers  40 . 
         [0036]    The sealing arrangements described and illustrated herein do not require additional hardware to implement, and may be applied to new engine configurations and are also able to be implemented in legacy engine configurations as refurbishment improvements. The seal arrangement reduces the risk of foreign object damage, and is able to be implemented in small design spaces, such as on small components of the gas turbine engine or across small gaps between components where traditional seal arrangements are impractical. The sealing arrangement does not require adherence to close tolerances and adds no loading or wear to the components. The sealing arrangement can easily be customized for specific locations and offer sealing possibilities to completely new locations in the gas turbine engine where traditional sealing arrangements are not utilized. Analysis shows leakage reductions of 14% to 36% compared to interfaces without a sealing arrangement. 
         [0037]    While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments. Accordingly, the present disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.