Abstract:
A retractable exhaust liner segment according to an example of the present disclosure includes, among other things, at least one liner segment extending between a forward end and an aft end. The forward end of the at least one liner segment is configured to overlap an aft end of an engine structure and the aft end of the at least one liner segment is configured to overlap a forward end of an exhaust liner when in an assembled position. The at least one liner is configured such that a gap exists between the at least one liner segment and one of the engine structure and the exhaust liner when the at least one liner segment is moved along an axis in a first direction to a disassembled position. The gap closes as the at least one liner segment is moved along the axis in a second, different direction to the assembled position.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present disclosure is a continuation of U.S. patent application No. 13/301,737, filed Nov. 21, 2011. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to gas turbine engines, and more particularly to an exhaust liner therefor. 
         [0003]    Some environments require a propulsion system in which an engine or exhaust system may be dropped or raised from an airframe for maintenance within the shadow of the airframe. 
       SUMMARY 
       [0004]    A retractable exhaust liner segment according to an example of the present disclosure includes at least one liner segment extending between a forward end and an aft end. The forward end of the at least one liner segment is configured to overlap an aft end of an engine structure and the aft end of the at least one liner segment is configured to overlap a forward end of an exhaust liner when in an assembled position. The at least one liner is configured such that a gap exists between the at least one liner segment and one of the engine structure and the exhaust liner when the at least one liner segment is moved along an axis in a first direction to a disassembled position. The gap closes as the at least one liner segment is moved along the axis in a second, different direction to the assembled position. 
         [0005]    In a further embodiment of any of the forgoing embodiments, the at least one liner segment includes a first retractable exhaust liner segment and a second retractable exhaust liner segment arranged circumferentially about the axis. 
         [0006]    A further embodiment of any of the foregoing embodiments includes a fastener assembly configured to mount a first flange of the first retractable exhaust liner segment to a second flange of the second retractable exhaust liner segment, wherein the fastener assembly includes a T-bolt. 
         [0007]    A further embodiment of any of the foregoing embodiments includes a retainer to retain the T-bolt within the first flange. 
         [0008]    In a further embodiment of any of the forgoing embodiments, the second flange includes a slot configured to receive the T-bolt pivotable through the slot. 
         [0009]    In a further embodiment of any of the forgoing embodiments, the at least one liner segment includes a locating feature configured to axially index the at least one liner segment with respect to at least one of the engine structure and the exhaust liner when in the assembled position. 
         [0010]    In a further embodiment of any of the forgoing embodiments, the locating feature defines a step surface configured to abut surfaces of at least one of the engine structure and the exhaust liner. 
         [0011]    A propulsion system according to an example of the present disclosure includes a gas turbine engine along an axis, an exhaust liner along the axis, and a retractable exhaust liner segment configured to span between a portion of the gas turbine engine and the exhaust liner. The retractable exhaust liner segment is configured such that a gap exists between the retractable exhaust liner segment and one of the gas turbine engine and the exhaust liner when the retractable exhaust liner segment is moved along the axis in one direction to a disassembled position. The gap closes when the retractable exhaust liner segment is moved along the axis in another direction to an assembled position. 
         [0012]    In a further embodiment of any of the forgoing embodiments, a forward end of the retractable exhaust liner segment is configured to overlap an aft end of the gas turbine engine and an aft end of the retractable exhaust liner segment is configured to overlap a forward end of the exhaust liner when the retractable exhaust liner segment is located in the assembled position. 
         [0013]    In a further embodiment of any of the forgoing embodiments, the retractable exhaust liner segment includes a first segment and a second segment arranged circumferentially about the axis. 
         [0014]    In a further embodiment of any of the forgoing embodiments, the retractable exhaust liner segment and the exhaust liner are mounted within an outer exhaust duct when in the assembled position. The outer exhaust duct is mountable to the gas turbine engine through an exhaust duct segment. 
         [0015]    In a further embodiment of any of the forgoing embodiments, the retractable exhaust liner segment is configured to oppose relative movement between the portion of the gas turbine engine and the exhaust liner when the retractable exhaust liner segment is located in the assembled position. 
         [0016]    In a further embodiment of any of the forgoing embodiments, the portion of the gas turbine engine is an engine tail cone configured to direct engine core flow to the exhaust liner. 
         [0017]    In a further embodiment of any of the forgoing embodiments, the exhaust liner and the gas turbine engine are selectively received in an airframe configured to oppose axial movement of the exhaust liner and the gas turbine engine along the axis in a direction away from the retractable exhaust liner segment. 
         [0018]    In a further embodiment of any of the forgoing embodiments, the gas turbine engine includes a compressor section, a combustor section and a turbine section. 
         [0019]    In a further embodiment of any of the forgoing embodiments, the retractable exhaust liner segment includes a step surface configured to axially index the retractable exhaust liner segment with respect to at least one of the portion of the gas turbine engine and the exhaust liner when in the assembled position. 
         [0020]    A method of maintaining a gas turbine engine according to an example of the present disclosure includes telescoping an exhaust liner segment along an axis over one of a gas turbine engine and an exhaust liner such that the exhaust liner segment defines a clearance gap between the other one of the gas turbine engine and the exhaust liner, and moving one of the gas turbine engine and the exhaust liner transverse to the axis and a distance through the clearance gap. 
         [0021]    A further embodiment of any of the foregoing embodiments includes translating a forward end of the exhaust liner segment along the axis such that the forward end of the exhaust liner segment overlaps an aft end of the gas turbine engine. 
         [0022]    A further embodiment of any of the foregoing embodiments includes translating an aft end of the exhaust liner segment along the axis such that the aft end of the exhaust liner segment overlaps a forward end of the exhaust liner. 
         [0023]    In a further embodiment of any of the forgoing embodiments, the exhaust liner is selectively received within an outer exhaust duct, and moving one of the gas turbine engine and the exhaust liner transverse to the axis is performed vertically with respect to an airframe configured to receive the gas turbine engine, the exhaust liner, and the exhaust liner segment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows: 
           [0025]      FIG. 1  is a general top perspective of an exemplary aircraft with a propulsion system for use with the present disclosure; 
           [0026]      FIG. 2  is a general side sectional view of the propulsion system; 
           [0027]      FIG. 3  is a general side sectional view of the propulsion system with a retractable exhaust liner segment in a closed position; 
           [0028]      FIG. 4  is a general side sectional view of the propulsion system with a retractable exhaust liner segment in an open position; 
           [0029]      FIG. 5  is a side view of the retractable exhaust liner segment; 
           [0030]      FIG. 6  is a plan view of a flange of the retractable exhaust liner segment; 
           [0031]      FIG. 7  is a side view of a flange of the retractable exhaust liner segment showing a fastener assembly according to one non-limiting embodiment; 
           [0032]      FIG. 8  is a side view of a flange of the retractable exhaust liner segment according to another non-limiting embodiment; 
           [0033]      FIG. 9  is a side view of a locating feature of the retractable exhaust liner segment according to one non-limiting embodiment; 
           [0034]      FIG. 10  is a side view of a locating feature of the retractable exhaust liner segment according to another non-limiting embodiment; 
           [0035]      FIG. 11  is a side view of a flange of the retractable exhaust liner segment showing a fastener assembly according to another non-limiting embodiment; 
           [0036]      FIG. 12  is a plan view of a flange of one segment of the retractable exhaust liner segment of  FIGS. 11 ; and 
           [0037]      FIG. 13  is a plan view of a flange of one segment of the retractable exhaust liner segment of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION 
       [0038]      FIG. 1  schematically illustrates an aircraft  10 . Some aircraft embed the engines within the vehicle planform to provide an effective balance of aero-performance, packaging, payload integration and survivability. The aircraft  10  in the disclosed non-limiting embodiment is schematically illustrated as a common air vehicle planform, however, it should be appreciated that any aircraft or vehicle will benefit herefrom and that the planform should not be considered limiting. 
         [0039]    The aircraft  10  generally includes an airframe  12  and a propulsion system  14 . The propulsion system  14  may be embedded within the airframe  12  and include an exhaust liner  16  and a gas turbine engine  20  along a central longitudinal engine axis A. The exhaust liner  16  and engine  20  are separately mounted within the airframe  12  and each is separately removable within the “shadow” of the airframe  12  via a retractable exhaust liner segment  18 . That is, each may be removed and replaced vertically from the airframe  12  with respect to the ground rather than axially along the engine axis A. The retractable exhaust liner segment  18  selectively provides axial installation clearances to avoid damage to engine flanges yet assures a desired backpressure seal when installed. 
         [0040]      FIG. 2  schematically illustrates the exhaust liner  16  and the gas turbine engine  20 . The exhaust liner  16  may be non-linear and/or transition to non-circular to suit airframe requirements. That is, the exhaust liner  16  may be contoured to at least partially extend off the axis A. The exhaust liner  16  may be of a linear or non-linear shape within an outer exhaust duct  32 D and may include a nozzle section  16 N. The nozzle section  16 N may include various fixed, variable, convergent/divergent, two-dimensional and three-dimensional nozzle systems. 
         [0041]    The gas turbine engine  20  is disclosed herein as a two-spool turbofan that generally incorporates a fan section  22 , a compressor section  24 , a combustor section  26 , a turbine section  28 , and an augmenter section  30 . The sections are defined along the central longitudinal engine axis A. Although depicted as an augmented low bypass gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are applicable to other gas turbine engines including non-augmented engines, geared architecture engines, direct drive turbofans, turboshaft engines, three-spool architecture engines and others. 
         [0042]    The compressor section  24 , the combustor section  26  and the turbine section  28  are generally referred to as the engine core. The fan section  22  and a low pressure turbine  34  of the turbine section  28  are coupled by a first shaft  36  to define a low spool. The compressor section  24  and a high pressure turbine  38  of the turbine section  28  are coupled by a second shaft  40  to define a high spool. 
         [0043]    An outer engine case structure  42  and an inner engine structure  44  define a generally annular secondary flow path  46  around a core flow path  48  of the engine core. It should be understood that various structure within the engine may define the outer engine case structure  42  and the inner engine structure  44  which essentially define an exoskeleton to support the core engine therein. It should be appreciated that the inner engine structure  44  as defined herein may include a turbine exhaust case, a stub liner, an augmenter liner, or any structure generally adjacent to an engine tail cone  50  and within the outer engine case structure  42  to direct the engine core flow. 
         [0044]    Air which enters the fan section  22  is divided between a core flow through the core flow path  48  and a secondary flow through the secondary flow path  46 . The core flow passes through the combustor section  26 , the turbine section  28 , then the augmentor section  30  where fuel may be selectively injected and burned to generate additional thrust through the exhaust liner section  32  and the exhaust liner  16 . The secondary flow may be utilized for a multiple of purposes to include, for example, cooling and pressurization. The secondary flow as defined herein is any flow different from the primary combustion gas exhaust core flow. 
         [0045]    The outer engine case structure  42  is mounted to the outer exhaust duct  32 D via a removable or retractable exhaust duct segment  32 Ds via, for example, V-band clamps  33  due to delta pressures an order of magnitude higher than the inner engine structure  44  and the exhaust liner  16 . The exhaust duct segment  32 Ds may be a split circumferentially in one or more places. That is, the duct segment  32 Ds, in one disclosed non-limiting embodiment, includes a cylindrical member defined by a multiple of segments. It should be appreciated that rubber reinforced bellows or other seals may be utilized to permit some relative motion, yet still seal the exhaust duct segment  32 Ds between the outer engine case structure  42  and the outer exhaust duct  32 D. Once unclamped the bellows may be readily forced away for interior access to the exhaust liner segment  18 . That is, the duct segment  32 D provides a seal for the secondary flow and generally axially extends along a travel range of the retractable exhaust liner segment  18  ( FIG. 3 ). 
         [0046]    The inner engine structure  44  is mounted to the exhaust liner  16  through the retractable exhaust liner segment  18  which may be loosened and then axially telescoped over either the inner engine structure  44  or the exhaust liner  16  along the axis A after removal or retraction of the duct segment  32 D ( FIG. 3 ). The retractable exhaust liner segment  18 , in one disclosed non-limiting embodiment, provides clearance for the tail cone  50  for a straight vertical engine installation/removal movement transverse to the axis A ( FIG. 4 ). 
         [0047]    With reference to  FIG. 5 , the retractable exhaust liner segment  18  may be a split ring that is split circumferentially in one or more places (two segments  18 A,  18 B shown). That is, the retractable exhaust liner section  18  is essentially a cylindrical member defined by a multiple of segments. 
         [0048]    A flange  52  is located at the interface of each segment  18 A,  18 B to define one or more fastener apertures  54  ( FIG. 6 ). Each flange  52  may be further supported by a gusset  56  to receive a fastener assembly  58  such as a nut and bolt through the apertures  54 . It should be appreciated that although two flanges  52  are illustrated for each segment  18 A,  18 B at a  180  degree displacement, it should be appreciate that only a single flange  52  may be utilized with radial flexing of the retractable exhaust liner segment  18  permitting movement thereof. 
         [0049]    The retractable exhaust liner segment  18  may be manufactured of a nickel alloy base structure and a liner surface  60  coated with a high temperature ceramic material. It should be understood that any type of liner system such as a dual wall, single wall, cooled or uncooled will benefit herefrom. In another disclosed, non-limiting embodiment, the liner surface  60  defines a lap joint  62  adjacent to the interface between the segments  18 A′,  18 B′ ( FIG. 8 ). The lap joint  62  further insulates the interface. 
         [0050]    The retractable exhaust liner segment  18  includes a locating feature  64 . The locating feature  64  may be an indentation or other undulation to axially index the retractable exhaust liner segment  18  with respect to the inner engine structure  44  and the exhaust liner  16 . In another disclosed, non-limiting embodiment, the locating feature  64 ′ defines a step surface  66  which provides an inner surface  68  which is generally parallel to the inner surfaces of the inner engine structure  44  and the exhaust liner  16  ( FIG. 10 ). 
         [0051]    With reference to  FIG. 11 , another disclosed, non-limiting embodiment, includes a flange  70  that supports one or more captured fastener assemblies  72 . Each captured fastener assembly  72  includes a T-Bolt  74  which is retained within one segment  18 A′ by a retainer  76 . That is, the T-bolt  74  is pivotally retained within segment  18 A′. Segment  18 A′ includes a slot  78  ( FIG. 12 ) such that a nut  80  need only be loosened along the T-Bolt  74  then the T-bolt  74  pivoted along a bolt axis B through an open slot  82  in segment  18 W′ ( FIG. 13 ) to assemble/disassemble segment  18 B″ from segment  18 A″ without any other separate components. This facilitates the reduction of Foreign Objet Damage (FOD). 
         [0052]    With the best mode for carrying out the invention and the operation thereof having been described, certain additional features and benefits of the invention can now be more readily appreciated. For example, the retractable exhaust liner segment  18  facilitates tail cone clearance; provides a relatively uncomplicated design; eliminates seals and facilitates a selectively tight interface to provide backpressure and avoid wear from random vibrations. 
         [0053]    It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting. 
         [0054]    It should also be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. 
         [0055]    Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure. 
         [0056]    Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
         [0057]    The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.