Abstract:
Aspects of the disclosure are directed to a system for maintaining a seal about an engine centerline, comprising: a first component, a second component, and a dog-bone seal coupled to the first component and the second component, wherein the first component is configured with at least one spline that is configured to engage a slot in the dog-bone seal to radially center the dog-bone seal relative to the first component and the second component.

Description:
[0001]    This application claims priority to U.S. Patent Appin. No. 62/091,260 filed Dec. 12, 2014, which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    A loss of a secondary flow of air into a gas-path of a turbine has a negative effect on engine fuel bum, performance/efficiency, and component life. Metal w-seals or dog-bone seals are commonly used to limit leakage of secondary flow between segmented or full-hoop turbine components. 
         [0003]    Exposure to significant relative axial/radial deflections, intermittent loading points, and/or elevated temperatures can preclude the use of w-seals or cause w-seals to deteriorate and be ineffective over time. 
         [0004]    Dog-bone seals, unlike—most w-seals, are full-hoop (i.e. not split in one circumferential location) and therefor require significant radial clearance to mating hardware that form the seal cavity. As a result, dog-bone seals cannot be kept concentric with an engine centerline and therefore cannot be kept in alignment with sealing features on mating hardware, such as feather seal slots. 
       BRIEF SUMMARY 
       [0005]    The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosure. The summary is not an extensive overview of the disclosure. It is neither intended to identify key or critical elements of the disclosure nor to delineate the scope of the disclosure. The following summary merely presents some concepts of the disclosure in a simplified form as a prelude to the description below. 
         [0006]    Aspects of the disclosure are directed to a system for maintaining a seal about an engine centerline, comprising: a first component, a second component, and a dog-bone seal coupled to the first component and the second component, wherein the first component is configured with at least one spline that is configured to engage a slot in the dog-bone seal to radially center the dog-bone seal relative to the first component and the second component. In some embodiments, the at least one spline comprises at least one pin attached to at least one pin slot in the first component. In some embodiments, the at least one pin is brazed to or attached to the at least one pin slot in the first component. In some embodiments, the at least one spline is formed by at least three pins. In some embodiments, the first component comprises a feather seal slot for coupling the first component and the dog-bone seal. In some embodiments, the second component comprises a second feather seal slot for coupling the second component and the dog-bone seal. In some embodiments, the system is associated with an aircraft. In some embodiments, the first component comprises a full-hoop component. In some embodiments, the second component comprises a segmented component. In some embodiments, the first component comprises a flow path component. In some embodiments, the dog-bone seal is configured to move relative to at least one of the first component and the second component within a range of approximately four-tenths of an inch. 
         [0007]    Aspects of the disclosure are directed to a system comprising: a dog-bone seal comprising a slot, and at least one spline configured to couple to the slot to maintain a positional relationship between the dog-bone seal and a component. In some embodiments, the at least one spline comprises at least one pin attached to at least one pin slot in the component. In some embodiments, the at least one spline is formed by at least three pins. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present disclosure is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements. 
           [0009]      FIG. 1  illustrates a gas turbine engine. 
           [0010]      FIG. 2A  illustrates an exemplary system incorporating a splined dog-bone seal maintained in a positional relationship to an engine centerline about a forward component and an aft component. 
           [0011]      FIG. 2B  illustrates a cross-sectional view ‘A’ of a portion of the splined dog-bone seal of  FIG. 2A . 
           [0012]      FIG. 3  illustrates an embodiment incorporating three equally spaced spline pins. 
           [0013]      FIG. 4A  illustrates a splined dog-bone seal in a steady-state condition. 
           [0014]      FIGS. 4B-4C  illustrate a splined dog-bone seal during transient conditions. 
           [0015]      FIGS. 5A-5B  illustrate a dog-bone seal that lacks a spline in accordance with the prior art. 
           [0016]      FIG. 6  illustrates an embodiment incorporated one or more radially-oriented spline pins. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    It is noted that various connections are set forth between elements in the following description and in the drawings (the contents of which are included in this disclosure by way of reference). It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. 
         [0018]    In accordance with various aspects of the disclosure, apparatuses, systems and methods are described for providing a seal, such as a splined dog-bone seal. Relative to the use of a w-seal, the use of a dog-bone seal may provide for a more robust/durable seal. Relative to a conventional dog-bone seal, a dog-bone seal in accordance with this disclosure may provide for a reduction/minimization in terms of leakage at forward and aft sealing interfaces by remaining concentric/centered relative to forward and aft mating parts/devices/components. A dog-bone seal in accordance with this disclosure may fit within a shorter seal cavity relative to a conventional dog-bone seal cavity that does not have inner diameter (ID) and outer diameter (OD) radial bumper/stop features (which add weight, complexity/cost, and require additional radial space). 
         [0019]    Aspects of the disclosure may be applied in connection with a gas turbine engine. For example,  FIG. 1  is a side-sectional illustration of a gas turbine engine  10 . The engine  10  includes a compressor section  12 , a turbine section  14  and one or more engine hot sections. The engine hot sections may include, for example, a first engine hot section  16  configured as a combustor section and a second engine hot section  18  configured as an augmentor section. The compressor section  12 , the first engine hot section  16 , the turbine section  14  and the second engine hot section  18  may be sequentially aligned along an axial centerline  20  between a forward engine airflow inlet  22  and an aft engine airflow exhaust  24 . 
         [0020]      FIG. 1  represents one possible configuration for an engine  10 . Aspects of the disclosure may be applied in connection with other environments, including additional configurations for an engine of an aircraft. 
         [0021]    Referring now to  FIGS. 2A-2B  (collectively referred to herein as  FIG. 2 ), a system  200  incorporating a splined dog-bone seal  1  is shown. Radial splines are occasionally used to keep parts centered (e.g., turbine inner air seals) relative to an engine centerline C L  (e.g., centerline  20  of  FIG. 1 ) and surrounding/mating parts, while allowing the splined part to move freely in the radial direction relative to its mating parts. The embodiment of  FIG. 2  includes one or more radially-oriented pins  4  and associated radially-oriented slots  9  in the dog-bone seal  1  to center the seal  1  relative to a forward mating component  2  and an aft mating component  3 . 
         [0022]    In some embodiments, one or both of the forward mating component  2  and the aft mating component  3  may include one or more full-hoop components or segmented components. In some embodiments, one or both of the components  2  and  3  may include a flow path component, e.g., turbine blade outer air seal (BOAS), turbine vanes, or mid turbine frames, that may be subject to higher/elevated temperatures relative to a non-flow path component (e.g., an outer casing, BOAS/vane/seal supports or a transition duct). In this respect, a difference in temperature, coefficient of thermal expansion, and/or thermal response rate may exist between the forward mating component  2  and the aft mating component  3  which the dog-bone seal  1  may have to accommodate. 
         [0023]      FIG. 2  shows a spline created by a combination of pins  4  coupled (e.g., brazed, welded, etc.) to pin slots  8  in the forward mating component  2  that are engaged with slots in the dog-bone seal  1 . Briefly referring to  FIG. 3 , an embodiment is shown that includes three pins  4  positioned one-hundred twenty degrees apart from one another. More than three pins  4  may be used in some embodiments. The pins  4  may be equally spaced. In some embodiments, the pins  4  may be asymmetrically spaced. 
         [0024]    Referring to  FIG. 6 , an embodiment incorporating a radially-oriented spline pin is shown. In  FIG. 6 , three or more equally spaced pins (reflected by reference character  4  in  FIG. 6 ) are straddled by one or more local devises  60  in the dog-bone seal  1 . The embodiment of  FIG. 6  may be used to eliminate leakage at the spline features and simplify the protruding spline features. 
         [0025]    Referring back to  FIG. 2 , as the forward component  2  and the aft component  3  move radially in and out relative to each other, as well as to the dog-bone seal  1 , slots in the seal  1  remain engaged with the radially-oriented pins  4  and only a small leakage gap  7  is maintained. Unlike other radially-based spline applications (e.g., turbine inner air seals, etc.), the embodiment of  FIG. 2  may maintain a constant and small gap  7  so that leakage at the spline feature is minimized/small. 
         [0026]    As shown in  FIG. 2 , one or more feather seal slots, such as feather seal slots  5  and  6 , may be included in the forward component  2  and/or the aft component  3 , respectively. The feather seal slots  5  and  6  may include a thin piece of sheet metal that may be used for coupling or interfacing to the dog-bone seal  1 . Mechanical tolerances may dictate the existence or size of the gap  7  using such a coupling between the dog-bone seal  1  and the feather seal slots  5  and  6 . In some embodiments, the feather seal slot  5  may be integral with the forward mating component  2 . In some embodiments, the feather seal slot  6  may be integral with the aft mating component  3 . 
         [0027]    As a result of the configuration in  FIG. 2 , the dog-bone seal  1  maintains alignment with the sealing features in the components  2  and  3  (e.g., feather seals between a turbine vane and a blade outer air seal (BOAS)) at a given steady-state flight condition. Conversely, a conventional or non-splined dog-bone seal can float anywhere within the radial design space, causing misalignment and associated leakage at forward/aft sealing interfaces. 
         [0028]    Due to thermal growth/expansion, the dog-bone seal  1  may move relative to one or more of the spline pin  4 , the forward component  2 , or the feather seal slot  5 . The movement may occur within a first range denoted by the inner forward (I FWD ) and outer forward (O FWD ) reference points of  FIG. 2 . Similarly, the dog-bone seal  1  may move relative to one or more of the aft component  3  or the feather seal slot  6 . The movement may occur within a second range denoted by the inner aft (I AFT ) and outer aft (O AFT ) reference points of  FIG. 2 . In some embodiments, the first range and/or the second range may be approximately four-tenths of an inch (0.4″), or approximately one centimeter (1 cm) of movement relative to I FWD  and O FWD  or I AFT  and O AFT . 
         [0029]      FIGS. 4A-4C  illustrate the dynamic range that may be experienced by the dog-bone seal  1  relative to the forward component  2 , the aft component  3 , and the pin slot  8 .  FIG. 4A  may be indicative of a steady-state condition, such as aircraft take-off or cruise.  FIGS. 4B  and  4 C may be indicative of two extreme transient conditions; for example,  FIG. 4B  may be indicative of an acceleration of the aircraft and  FIG. 4C  may be indicative of a deceleration of the aircraft. In  FIG. 4C , a stopper  40  is shown. The stopper  40  may be integral with one or more components, such as the aft mating component  3  as shown. The stopper  40  may not be included in some embodiments, given that a splined dog-bone seal in accordance with this disclosure stays significantly centered about the engine centerline C L  (e.g., centerline  20 ) during all steady-state and transient conditions. 
         [0030]    While not explicitly shown in  FIGS. 4A-4C , the dog-bone seal  1  may line up with one or both of the feather seal slot  5 ,  6  at a bottom dead center (BDC) circumferential location as well. 
         [0031]    In contrast to  FIGS. 4A-4C ,  FIGS. 5A-5B  illustrate a conventional dog-bone seal  501  that lacks a spline about a forward component  502  an aft component  503 . 
         [0032]    The environmental contexts/conditions in  FIGS. 5A-5B  may be the same as, or analogous to, the environmental contexts/conditions described above in connection with  FIGS. 4B-4C . Regardless of the flight condition, there is nothing in  FIGS. 5A-5B  keeping the dog-bone seal  501  centered about the engine centerline, so the dog-bone seal  501  will move off-center in a radial direction until it bumps into a stopper (e.g., as shown in  FIGS. 5A-5B ) on the forward component  502  and/or the aft component  503 . As such, at all flight conditions a leak path (as reflected via the arrows  560 ) is introduced between the dog-bone seal  501  and all, or nearly all, feather seals located at the gap between adjacent segmented components. 
         [0033]    Aspects of the disclosure have been described in terms of illustrative embodiments thereof. Numerous other embodiments, modifications, and variations within the scope and spirit of the appended claims will occur to persons of ordinary skill in the art from a review of this disclosure. For example, one of ordinary skill in the art will appreciate that the steps described in conjunction with the illustrative figures may be performed in other than the recited order, and that one or more steps illustrated may be optional in accordance with aspects of the disclosure.