Patent Publication Number: US-2016238252-A1

Title: Thermally expandable transition piece

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to gas turbine engines, and more particularly, to a gas turbine engine transition piece and its support assemblies. 
     BACKGROUND 
     Gas turbine engines operate to produce mechanical work or thrust. One type of gas turbine engine is a land based engine coupled to a generator for the purposes of generating electricity. Gas turbine engines have at least a compressor section, a combustor section, and a turbine section. The combustor section may include a plurality of combustors arranged in an annular array around a rotor. The turbine section includes alternating rows of stationary airfoils and rotating airfoils. In operation, air is drawn in through the compressor section, where it is compressed and the driven towards the combustor section. The air may then be mixed with fuel to form an air/fuel mixture. In the combustor, the mixture may be ignited to form a working gas. A transition duct may be provided for each combustor to route the working gas to the turbine section. Each transition duct includes an inlet (upstream) end, an exit (downstream) end. To support the transition duct in the gas turbine, fixed support assemblies including support brackets and various seals have been provided at both the downstream and upstream ends for attaching the same to structures in both the turbine and combustor sections, respectively. However, concerns arise as these support assemblies suffer from large thermal stresses at various locations during the gas turbines operation, thereby restricting thermal growth of hot transition ducts. Therefore, there remains a need for a means to support the transition duct that can minimize the above concerns, and allow for thermal growth. 
     SUMMARY 
     In one embodiment, a gas turbine engine with a thermally expandable transition piece is described, and which comprises at least a combustor section. The combustor section includes a combustor sleeve and a transition piece. The transition piece includes a transition duct having an upstream end, a downstream end, an outer surface and an end face. The transition piece further includes a strut extending radially outward from the outer surface at the upstream end for interfacing with at least a portion of the combustor sleeve. 
     In another embodiment, a thermally expandable transition piece assembly for a gas turbine engine is described. The transition piece includes a transition duct having an upstream end for operatively connecting to a combustor section of a turbine, and a downstream end for operatively connecting to a turbine cylinder section of a turbine. The transition piece further includes a strut selectively attached at the upstream end, and extending radially upward from an outer surface of the transition duct, and axially outward beyond an end face at the upstream end for operatively connecting the transition piece assembly to the combustor section of a turbine. 
     In yet a further embodiment, a method of manufacturing a thermally expandable transition piece is disclosed. The method includes the step of selectively attaching a strut to a surface of a transition duct at an upstream end of the transition duct, the strut extending radially upward from the surface and axially outward beyond an end face at the upstream end. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a transition duct mounted to a combustor section with a mounting assembly known in the prior art; 
         FIG. 2  illustrates a cutaway perspective view of a gas turbine engine including a thermally expandable transition piece in accordance with the disclosure provided herein; 
         FIG. 3  illustrates a perspective view of an embodiment of a thermally expandable transition piece in accordance with the disclosure provided herein; 
         FIG. 4  illustrates an embodiment of the thermally expandable transition piece engaged to a structure in the combustor section of the gas turbine engine in accordance with the disclosure provided herein; 
         FIG. 5  is a block diagram of a method for manufacturing a thermally expandable transition piece in accordance with the disclosure provided herein; and 
         FIG. 6  is a block diagram of a method for assembling a gas turbine engine in accordance with the disclosure provided herein. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the subject matter herein only and not for limiting the same,  FIG. 2  shows a perspective view of a gas turbine engine (GTE) depicted generally at  100  with a thermally expandable transition piece  200 . The GTE  100  generally may include at least an inlet casing section  120  operatively connected to a compressor casing section  130 ; the compressor casing section  130  may be operatively connected to a combustor section  140 ; the combustor section  140  may be operatively connected to a turbine cylinder section  150 ; the turbine cylinder section  150  may be operatively connected to an exhaust cylinder section  160 ; the exhaust cylinder section  160  may be operatively connected to a manifold section  170 . 
     With reference to  FIGS. 3 , a perspective view of the thermally expandable transition piece  200  is shown. In one embodiment, the transition piece  200  includes at least a transition duct  210  having a generally tubular body with a generally semi-circular shape at an upstream end  212 , to receive hot gases from an associated combustor of a gas turbine (e.g., a can-annular combustor), and a generally semi-rectangular shape at a downstream end  214 , to discharge the gases to an associated stage of the gas turbine. The transition duct  210  further includes an outer surface  216 , and a forward end face  218 . The thermally expandable transition piece  200  may further include one or more struts  300  selectively attached to an outer surface  216  of the transition duct  210  proximate to the upstream end  212 . In the embodiment of  FIG. 3 , three struts  300  are attached at the upstream end  212 ; however, it should be appreciated that more than three struts  300  may be attached to the thermally expandable transition piece  200 . When selectively attached to the transition duct  210 , the strut  300  may extend radially outward (protruding upwardly) from the outer surface  216  at the upstream end  212 . Additionally, at least a portion of the strut  300  may extend axially outward beyond the forward end face  218 . 
     With continued reference to  FIG. 3 , the struts  300  may be spaced apart in a uniform manner around the perimeter of the transition duct  210 . For example,  FIG. 3  illustrates the struts  300  being spaced an equidistance apart from one another. However, it should be appreciated that the struts  3000  may be spaced apart in any manner chosen with sound judgment. In yet a further embodiment, the struts  300  may be offset from one another around the perimeter of the transition duct  210  such that the length of the portions of the struts  300  extending beyond the forward end face  218  differs. The struts  300  may be selectively attached to the outer surface  216  by an attachment means (not shown), such as by bolts, fasteners, pins, and/or weld. Additional examples of the attachment means may include a nut-bolt combination, rivet, screw, nail, or other suitable mechanical fastening devices known to persons of ordinary skill in the art and capable of selectively attaching the strut  300  to the transition duct  210 . 
     In a further embodiment, the strut  300  may be integrally formed with the transition duct  210 . As used herein, integrally formed means to couple such that the pieces are relatively permanently joined. The strut  300  and the transition duct  210  may also be fabricated, molded or machined as a unitary structure, as compared to being separate components mounted together, through welding, fastening mechanical engagement or any means known to persons of ordinary skill in the art. In an embodiment where the struts  300  are not integrally formed with the transition duct  210 , the strut  300  may include a lower end face  310  adapted to selectively attach the strut  300  to the outer surface  216  of the transition duct  210 , and an upper end face  320  adapted to interface with a combustor sleeve  400  or wear pad  410  ( FIG. 4 ) of the combustor section  140 . The lower end face  310  may have a profile adapted to interface with the outer surface  216 , e.g., an arcuate profile. Additionally, the upper end face  320  may have a profile adapted to interface with the combustor sleeve  400  or wear pad  410 . The profile of the lower end face  310  and the upper end face  320  may be similar in one embodiment, or they may differ in a further embodiment such that the both profiles curve in opposed directions. 
     The strut  300  may have a thickness that provides for adequate strength to support the transition piece  200 , without restricting flow during operation of the GTE  100 . In one embodiment, the surface area for the lower end face  310  and the upper end face  320  may differ. For example, as illustrated in  FIG. 4 , the upper end face  320  surface area is less than the surface area of the lower end face  310 . The strut  300  may have a generally arcuate profile such that the surface area of the lower surface  330  and upper surface  340 , between the lower end face  310  and upper end face  320 , has no angles. In a further embodiment, the surface area of the strut  300  may have one or more angles between the lower end face  310  and upper end face  320 . Additionally, the strut  300  may also be symmetrical or asymmetrical. 
     With continued reference to  FIG. 3 , and now  FIG. 4 , the combustor sleeve  400 , also referred to as “top hat” in the art, includes an interior compartment  420  configured to house at least a portion of a combustor  500  therein, and an exterior  430  having one or more flanges  440  protruding therefrom. The flange  440  may be adapted for interfacing the combustor sleeve  400  with one more components of the GTE  100 , and for at least partially restricting movement of the combustor sleeve  400 . The interior compartment  420  may be sized such that at least a portion of the transition piece  200 , (e.g., strut  300 ) may be received therein. In the embodiment of  FIG. 4 , the strut  300  extending from the transition duct  210  is shown as being partially disposed within the interior compartment  420  and interfacing with an interior surface  425  of the interior compartment  420 . 
     The wear pad  410  may be an adaptable plate sized to fit within the interior compartment  420 , and be made from hard materials, such as a metallic or ceramic material, e.g., nickel or cobalt, or a softer material with hard facing, e.g., chromium carbide, flame sprayed, or any other material chosen with sound judgment and capable of interfacing with the interior compartment  420  and/or strut  300 , managing contact stress, and maintaining a form of structural integrity such that the wear pad  410  or portions thereof have little to no chance of separation during operation of the GTE  100 . The wear pad  410  may be constructed from a material different from that of the strut  300  and/or the interior compartment  420 . The wear pad  410  may also have a low profile and be adapted to conform to the shape of the interior compartment  420 , e.g., an arcuate shape. The wear pad  410  may be selectively attached to the interior surface  425  by an attachment means similar to the attachment means described herein. The attachment means should allow for no separation of the wear pad  410  from the interior compartment  420  during operation of the GTE  100 . Additionally, the attachment means may further assist in facilitating the replacement of the wear pad  410  when its surface area begins to wear down or simply needs to be replaced. In a further embodiment, multiple wear pads may be stacked within the interior compartment to provide additional interfacing support, or facilitate the replacement of a worn wear pad  410 . 
     In yet a further embodiment, the wear pad  410  may be integral with the interior compartment  420 . Additionally, the wear pad  410  may extend to cover the interior surface  425 , or may have a defined area thereby distinguishing the wear pad  410  surface from any other surface of the interior compartment  420 . In yet a further embodiment, at least a portion of the wear pad  410  surface may be grooved, textured, or have a configuration chosen with sound judgment to allow for interfacing the wear pad  410  with the strut  300 , while maintaining the integrity of the wear pad  410 . In yet a further embodiment, the wear pad  410  may be a substrate or formed from a substrate applied to the interior surface  425  by an additive manufacturing process, the result of which manages contact stress. The wear pad  410  may further allow for the transition piece  200  to be frictionally fitted within the interior compartment  420 , while allowing for thermal expansion. Additionally, the wear pad  410  may be lubricious to further facilitate interfacing and thermal expansion. 
     With continued reference to the figures, and now  FIG. 5 , a block diagram of a method  1000  for manufacturing a thermally expandable transition piece  200  in accordance with one embodiment is provided. In step  1010 , selectively attaching the strut  300  to the outer surface  216  of a transition duct  210  at an upstream end  212  of the transition duct  210  by the attachment means disclosed herein. In yet a further embodiment, prior to step  1010 , the method  1000  may include step  1020  for removing an assembly for mounting the transition duct  210 . In this step, removal of the prior art assembly ( FIG. 1 ), may be necessary when retrofitting the struts  300  to the transition duct  210 . In step  1030 , selectively attaching a plurality of struts  300  to the transition duct  210 . 
     With continued reference to the figures, and now  FIG. 6 , a block diagram of a method  2000  for assembling the GTE  100 , or more particularly, the combustor section  140  of the GTE  100  with the transition piece  200  in accordance with one embodiment is provided. In step  2010 , operatively interfacing the thermally expandable transition piece  200  to a structure (e.g., combustor sleeve  400  or wear pad  410 ) in the combustor section of the GTE  100 . In this step, an assembler may shift the transition piece  200  towards the combustor sleeve  400  such that at least a portion of the transition piece  200 , e.g., the strut  300 , may be received within the combustor sleeve  400 . At this point, the strut  300  may be interfacing with the interior surface  425  or wear pad  410 . 
     While specific embodiments have been described in detail, those with ordinary skill in the art will appreciate that various modifications and alternative to those details could be developed in light of the overall teachings of the disclosure. For example, elements described in association with different embodiments may be combined. Accordingly, the particular arrangements disclosed are meant to be illustrative only and should not be construed as limiting the scope of the claims or disclosure, which are to be given the full breadth of the appended claims, and any and all equivalents thereof. It should be noted that the term “comprising” does not exclude other elements or steps, and the use of articles “a” or “an” does not exclude a plurality.