Patent Publication Number: US-9416969-B2

Title: Gas turbine transition inlet ring adapter

Description:
FIELD OF THE INVENTION 
     The present invention relates to a combustor device and transition duct assembly in a gas turbine engine and, more particularly, to such an assembly having a transition duct comprising an inlet ring adapter for cooperating with a spring clip seal on the combustor device. 
     BACKGROUND OF THE INVENTION 
     A modern gas turbine engine, such as is used for generation of electricity at power plants, is a multi-part assembly of sub-components, many of which are subjected to vibrational and thermal stresses over long periods of operation. To the extent that various sub-components and their respective parts are designed, manufactured, shipped and installed to reduce undesired stresses, this may result in longer operation and less downtime. 
     In common configurations of gas turbine engines, a plurality of combustors is arranged circumferentially about a longitudinal axis of the engine. Compressed air from a compressor is mixed with fuel in each combustor and flows to a combustion zone where the fuel/air mixture is ignited to form a hot working gas. The combustion zone begins downstream from a base plate within the combustor that demarcates an upstream end of the combustion zone. The combustion zone may terminate before or may extend into what is referred to as a transition duct. The transition duct is a conduit that carries hot gases into a turbine section of the engine where the hot working gases pass through a series of alternating rows of turbine vanes and turbine blades to extract work. 
     A common approach to assembly of a transition duct with a combustor in a gas turbine engine is to attach an assembly of spring clips at a downstream end of the combustor. For example, a spring clip ring assembly may be provided at a downstream end of a combustor that provides sliding support that accommodates thermal growth of the combustor and transition duct. Spring clip ring assemblies may comprise a plurality of spring fingers that are resiliently biased radially outwardly from the end of the combustor into engagement with an inner surface of an inlet ring located at an upstream end of the transition duct. A known spring clip seal assembly incorporated in a gas turbine engine is disclosed in U.S. Pat. No. 7,093,837, which patent is incorporated herein in its entirety. 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of the invention, a combustion system is provided for a gas turbine engine. The combustion system comprises a combustor assembly comprising a combustor basket having a downstream terminal end, and a transition duct extending downstream from the combustor basket and having an upstream end located adjacent to the downstream terminal end of the combustor basket. An inlet ring adapter is affixed to the upstream end of the transition duct. The inlet ring adapter extends downstream of the upstream end of the transition duct in overlapping relation to an inner surface of the transition duct. A spring clip assembly is mounted to the terminal end of the combustor basket and is resiliently biased into engagement with an inwardly facing surface of the inlet ring adapter to form a coupling between the combustor basket and the transition duct. 
     The inlet ring adapter may comprise a cylindrical sleeve extending generally parallel to the transition duct, and a flange portion extending perpendicular to the sleeve and attached to the upstream end of the transition duct. 
     The flange portion may be formed with apertures for receiving removable fasteners, and the upstream end of the transition duct may include threaded holes for receiving bolts received through the apertures in the flange portion. 
     A bolt ring may be affixed to the upstream end of the transition duct and may include the threaded holes. The bolt ring may define a radial thickness that is greater than a radial thickness of the upstream end of the transition duct. The bolt ring may be welded to the upstream end of the transition duct. Alternatively, the bolt ring may be formed integral with the upstream end of the transition duct. 
     The transition duct may include a radial step at the upstream end to define a first larger diameter adjacent to the sleeve of the inlet ring adapter and a second smaller diameter extending in a direction distal from the inlet ring adapter. 
     The inwardly facing surface of the inlet ring adapter may define an inner diameter that is greater than the second smaller diameter of the transition duct. 
     The sleeve of the inlet ring adapter may include a distal downstream end that is located adjacent to the radial step of the transition duct that may effect a reduction in recirculation flow at the radial step. 
     In accordance with another aspect of the invention, a combustion system is provided for a gas turbine engine. The combustion system comprises a combustor assembly comprising a combustor basket having a downstream terminal end, and a transition duct extending downstream from the combustor basket and having an upstream end located adjacent to the downstream terminal end of the combustor basket. A coupling is provided comprising an inlet ring adapter including a cylindrical sleeve extending downstream of the upstream end of the transition duct in overlapping relation to an inner surface of the transition duct. A spring clip assembly is mounted to the terminal end of the combustor basket. The spring clip assembly extends into engagement with and forms a seal on the cylindrical sleeve. 
     The cylindrical sleeve may be spaced radially inwardly from the inner surface of the transition duct. 
     The cylindrical sleeve may be mounted on the transition duct with removable fasteners. A flange portion may extend radially outwardly from the cylindrical sleeve, and apertures may be formed through the flange portion for receiving the removable fasteners. 
     A bolt ring may be welded to the upstream end of the transition duct, and may include threaded holes for receiving the removable fasteners. 
     At least a portion of the spring clip assembly may be resiliently biased into engagement with an inwardly facing surface of the cylindrical sleeve. 
     The transition duct may include a radial step at the upstream end to define a first larger diameter adjacent to the cylindrical sleeve and a second smaller diameter extending in a direction distal from the cylindrical sleeve. 
     An inwardly facing surface of the cylindrical sleeve may define an inner diameter that is greater than the second smaller diameter of the transition duct. 
     The cylindrical sleeve may include a distal downstream end that is located adjacent to the radial step of the transition duct that may effect a reduction in recirculation flow at the radial step. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein: 
         FIG. 1  is a cross-sectional view of a combustor assembly incorporating an inlet ring adapter in accordance with aspects of the present invention; 
         FIG. 2  is an enlarged view of an area  2  identified in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a transition duct for the combustor assembly of  FIG. 1 ; 
         FIG. 4  is an enlarged view of a transition inlet end in accordance with an aspect of the invention; 
         FIG. 5  is a perspective view of the inlet ring adapter; 
         FIG. 6  is a cross-sectional view of the inlet ring adapter taken along line  6 - 6  in  FIG. 5 ; and 
         FIG. 7  is an enlarged cross-sectional view of the inlet ring adapter assembled to the inlet end of the transition duct. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of the preferred embodiment, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, a specific preferred embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention. 
     Referring to  FIG. 1 , a portion of a can-annular combustion system of a gas turbine engine is shown and includes a combustor assembly  10  comprising a combustor basket  12  and a transition duct  14 . The combustor basket  12  comprises a cylindrical liner  16  and a burner assembly  18  located at an upstream end of the liner  16 . The combustor basket  12  is configured to be supported in a combustor casing (not shown) in a known manner to receive air and fuel which are combusted downstream of the burner assembly  18  to form a hot working gas passing through the liner  16 . 
     The transition duct  14  includes an upstream end  20 , defining a transition inlet ring, that is adjacent and coupled to a terminal downstream end  22  of the combustor basket  12  at a circumferentially extending coupling  24  between the liner  16  and the transition duct  14 . The upstream end  20  of the transition duct  14  receives the hot working gases from the downstream end  22  of the combustor basket  12 , and the transition duct  14  defines a gas path to a downstream end  26  ( FIG. 3 ) at an inlet to a turbine section of the engine. The downstream end  22  of the combustor basket  12 , as defined by the liner  16 , extends in overlapping relation to an inner surface  28  of the transition duct  14 , and the coupling  24  forms a seal for preventing or limiting leakage of combustor shell air at the interface between the combustor basket  12  and the transition duct  14 . 
     As best seen in  FIGS. 2 and 7 , at the location of the coupling  24 , the inner surface  28  of the transition duct  14  is formed with a stepped area  29 . The stepped area is formed by an upstream first larger diameter  31  ( FIG. 3 ) defined by a first inner surface  31   a , and a downstream second smaller diameter  33  ( FIG. 3 ) defined by a second inner surface  33   a  extending in an axial direction distal from the first inner surface  31   a . The first and second inner surfaces  31   a ,  33   a  are connected by a radial step wall  35 . 
     In accordance with an aspect of the invention, the coupling  24  comprises structure on the transition duct  14  for cooperating with a conventional spring clip assembly or seal  30  mounted to a radially outer surface  32  of the liner  16 , as seen in  FIG. 2 . The spring clip seal  30  may comprise a structure having a plurality of spring clip leaves or fingers  34  resiliently biased outwardly, such as is described in U.S. Pat. No. 7,093,837. The spring clip seal  30  includes a radially inner section  36  that may be attached to the outer surface  32  of the liner  16  by a weld or similar connection. It should be understood that although specific reference is made to the spring clip seal of U.S. Pat. No. 7,093,837 for exemplary purposes, the present invention is not limited to assemblies specific to the spring clip seal disclosed in the referenced patent. 
     Referring to  FIGS. 2, 5 and 6 , the coupling  24  includes an inlet ring adapter  38  that is affixed to the inlet opening or upstream end  20  of the transition duct  14 . In a preferred embodiment, the inlet ring adapter  58  is configured to be detachably mounted to the upstream end  20  of the transition duct  14 , and thereby become a structure of the upstream end  20  for cooperating with the spring clip seal  30 . The inlet ring adapter  38  has a top-hat configuration comprising a cylindrical sleeve  40  for extending parallel a longitudinal axis  42  ( FIG. 3 ) of the transition duct  42 , and a flange portion  44  extending radially outwardly perpendicular to the sleeve  40  and configured for attachment to the upstream end  20  of the transition duct  14 . 
     As seen in  FIGS. 5 and 6 , the flange portion  44  of the inlet ring adapter  38  is formed with a plurality of apertures  46  for receiving removable fasteners ( FIG. 7 ), such as bolts  48 . In accordance with an aspect of the invention, a bolt ring  50  is affixed to the upstream end  20  of the transition duct  14 , wherein the bolt ring  50  defines threaded holes  52  ( FIG. 4 ) at the upstream end  20  of the transition duct  14  for receiving the bolts  48  to rigidly affix the inlet ring adapter  38  to the transition duct  14 . Further, Nord-Lock® washers  49  ( FIG. 7 ) may be provided to facilitate retention of the bolts  48  in position. 
     In the configuration illustrated in  FIGS. 1-4 , the bolt ring  50  may be welded to a forward facing edge of the transition duct  14 . It may be understood that the bolt ring  50  is formed with a radial thickness dimension that is greater than the radial thickness dimension of the upstream end  20  of the transition duct  14  so as to provide sufficient material thickness for formation of the threaded holes  52 . In particular, the bolt ring  50  provides additional material thickness extending radially inwardly from the first inner surface  31   a  of the upstream end  20 . 
     The present coupling  24  may comprise a retrofit installation on an engine, and it may be necessary to grind down a portion of the forward facing (upstream) edge of the transition duct  14  to accommodate the additional axial dimensions provided by the bolt ring  50  and/or the inlet ring adapter  38 . Alternatively, if the transition duct  14  is formed as a new component for installation in the engine, the structure of the bolt ring  50  and associated bolt holes  52  may be formed, such as by casting, integrally with the transition duct  14 , as is illustrated by the bolt ring  50  in  FIG. 7 . 
     Referring to  FIG. 7 , the sleeve  40  of the inlet ring adapter  38  is formed with a radial thickness that is less than a radial dimension of the radial step wall  35 , from the first inner surface  31   a  to the second inner surface  33   a . Further, an outwardly facing surface  54  of the inlet ring adapter sleeve  40  is spaced inwardly from the first inner surface  31   a  a radial distance d 1 , and the distance d 1  is approximately equal to or slightly greater than the inward extension of the bolt ring  50  from the first inner surface  31   a . Also, in the illustrated embodiment, a radial inward surface  56  of the inlet ring adapter sleeve  40  is located at a diameter that is greater than the second diameter  33  defined by the second inner surface  33   a , and a distal end  41  of the sleeve  40  extends to a location closely adjacent to the radial step wall  35 , as denoted by axial distance d 2 . The distance d 2  is preferably sufficient to avoid contact between the distal end  41  of the sleeve  40  and the step wall  35  in view of thermal movement and vibrations occurring during operation of the engine, and is also preferably small to minimize flow of gases into the space between the first inner surface  31   a  and the sleeve  40 . 
     In accordance with an aspect of the invention, the radial inward surface  56  of the inlet ring adapter sleeve  40  forms an engagement surface for contact with the spring clip seal  30  to define the seal at the coupling  24 . It may be noted that there is typically relative movement between the spring clip seal  30  and the sleeve  40  as a result of variations in thermal movement between the combustor basket  12  and the transition duct  14 , as well as due to relative vibratory movement between the combustor basket  12  and the transition duct  14 . Hence, the inward surface  56  of the sleeve  40  may experience wear during continued operation of the engine. In prior or known constructions comprising a seal formed at an interface between a spring clip seal and a transition duct, the spring clip seal would engage and cause wear or deterioration of the interior surface of the transition duct. Such wear typically has required a costly repair operation of the inlet end, i.e., repair of the transition inlet ring, or replacement of the transition duct. Further, such repairs may introduce tolerance variations, leading to non-uniform contact with the spring clip seal with increased stress on the spring clip seal, potentially causing premature failure of the spring clip seal during subsequent operation of the engine. 
     The present inlet ring adapter  38  provides a detachably replaceable component, i.e., an expendable component, that can be formed with relatively high precision for uniform engagement with the spring clip seal  30 , facilitating a longer operating life for the spring clip seal  30 . Additionally, prior to installation, the inlet ring adapter  38  can be provided with a wear coating, such as by electroplating or an alternative coating process to provide desired extended wear characteristics for cooperating with the spring clip seal  30 . 
     Additionally, the sleeve  40  of the inlet ring adapter  38  effectively reduces the size of the inlet diameter and of the step from the second inner wall  33   a , that may effect a reduction in recirculating flow at the end of the combustor basket  12 . For example, the reduced step dimension along the step wall  35  may reduce recirculating flow in a space  58  ( FIG. 2 ) between the radial inward surface  56  and the spring clip fingers  34 . The reduction in the diameter that can be provided by the inlet ring adapter  38  also permits the transition duct  14  to be used with spring clip ring structures having smaller diameters than an original spring clip structure designed for the transition duct  14 . That is, the combustor basket  12  may be retrofit with a new or different spring clip seal  30  that has a different diameter, e.g., a smaller diameter, than the spring clip seal being replaced, and the inlet ring adapter  38  may be used to facilitate matching the inlet diameter of the transition duct  14  to the new spring clip seal  30 . 
     While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.