Abstract:
An annular seal for use between coupled combustor components includes a segmented annular solid edge portion and a plurality of alternating spring fingers and slots extending from the solid edge portion and arranged about a circumference of the solid edge portion, wherein one or more of the plurality of spring fingers or one or more of the plurality of straight and angled slots have non-uniform width dimensions.

Description:
BACKGROUND 
     The present invention relates to internal cooling within a gas turbine engine, and more particularly, to seals used between combustor components that also enhance cooling within the region of the seal. 
     Air management is an important consideration in combustor design. Air streams provide an oxidizer for the combustion process and also provide cooling to hot gas path components of the combustor. Seals are typically provided between various components of the combustor to prevent hot combustion gas from leaking from the combustor. Seal configurations and functions of those seals are unique in the combustor. For example, a seal providing complete sealing of flow from one area to another may not be desired but rather, a seal resulting in a small amount of cooling air “leak” may be preferred. Within combustion zones, cooling must be properly designed to provide adequate cooling for hot gas path components while only minimally disturbing combustion ignition and stability. 
     Seals are typically used between, for example, gas turbine combustor liners and transition pieces or ducts that carry hot combustion gases to the first stage of the gas turbine. They typically include C-rings, spring-finger or “hula” rings, cloth seals and the like, all of which are subjected to high temperature and pressure as well as high gradients of pressure and temperature across the seals. 
     There remains need for enhanced levels of active cooling with minimal pressure losses at high-firing temperatures by, for example, targeting hot streaks along the hot side of the combustor liner and transition piece or duct for preferential cooling. 
     BRIEF SUMMARY OF THE INVENTION 
     Accordingly, in one exemplary but nonlimiting embodiment, the invention provides an annular seal for use between coupled combustor components, the annular seal comprising a segmented annular solid edge portion and a plurality of alternating spring fingers and slots extending from said solid edge portion and arranged about a circumference of said solid edge portion, wherein one or more of said plurality of spring fingers, or one or more of said plurality of slots, have non-uniform width dimensions. 
     In another exemplary but nonlimiting embodiment, the invention provides gas turbine combustor assembly comprising a substantially cylindrical combustor liner secured at a forward end to an end cap supporting one or more nozzles; a transition piece having a forward end telescopically received over an aft end of said combustor liner, an aft end of said transition piece adapted for attachment to a turbine first stage; and an annular seal disposed radially between said aft end of said combustor liner and said forward end of said transition piece, said annular seal comprising a segmented annular solid edge portion and a plurality of spring fingers extending from said solid edge portion and arranged about a circumference of said solid edge portion, said spring fingers separated by adjacent slots, and wherein at least some of said plurality of spring fingers are arranged angularly relative to a centerline axis through the annular seal. 
     In still another exemplary but nonlimiting embodiment, the invention provides method of preferentially cooling a region in a turbine combustor where a combustor liner is joined to a transition piece, and an annular spring finger seal is located radially between an aft end of said combustor liner and a forward end of said transition piece, and wherein said annular spring finger seal comprises a plurality of spring fingers extending from a segmented annular solid edge, the method comprising diverting a portion of air flowing in one direction to the combustor to flow in an opposite direction through said annular seal; and arranging said plurality of spring fingers by width or angular orientation to direct air flowing through said annular seal one or more targeted regions of the combustor liner or the transition piece where differentially higher temperatures have been identified as compared to other regions of the combustor liner or transition piece. 
     The invention will now be described in detail in connection with the drawings identified below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified schematic cross-sectional view of a gas turbine combustor; 
         FIG. 2  is an enlarged partial cross-sectional view of the interface between the combustor liner and transition piece components removed from  FIG. 1 ; 
         FIG. 3  is a perspective view of a conventional spring-finger or hula seal used at the interface between the combustor liner and the transition piece; 
         FIG. 4  is a perspective view of a spring-finger or hula seal used at the interface between the combustor liner and the transition piece in accordance with an exemplary but nonlimiting embodiment; and 
         FIG. 5  is a perspective view of a spring-finger or hula seal used at the interface between the combustor liner and the transition piece in accordance with another exemplary but nonlimiting embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Shown in  FIG. 1  is a gas turbine  10 . The gas turbine  10  includes a compressor  12  which provides compressed fluid to a combustor  14 . Fuel is injected into the combustor  14 , mixes with the compressed air and is ignited. The hot gas products of the combustion flow to a turbine  16  which extracts work from the hot gas to drive a rotor shaft  18  which in turn drives the compressor  12 . A transition piece  20  is coupled at an upstream end  22  to the combustor  14  at a combustor liner  24  and at a downstream end  26  to an aft frame  28  of the turbine  16 . The transition piece  20  carries hot gas flow from the combustor liner  24  to the turbine  16 . The combustor  14  includes a combustor sleeve  30  spaced radially outward from the combustor liner  24  defining a combustor flow channel  32  therebetween. A combustor cap  34  is coupled to an upstream end  36  of the combustor liner  24  and includes at least one nozzle  38  disposed therein an extending into a combustion chamber  40  defined by the combustor cap  34  and the combustor liner  24 . An impingement sleeve  42  is coupled to the combustor sleeve  30  and is radially spaced from the transition piece  20  defining a transition flow channel  44  therebetween. 
     During operation, discharge flow  46  flows from the compressor  12  through a diffuser  48  to the impingement sleeve  42 . The discharge flow  46  proceeds through a plurality of impingement holes  50  in the impingement sleeve  42  and toward the combustor  14  in the transition flow channel  44 . The discharge flow  46  proceeds from the transition flow channel  44  and through the combustor flow channel  32  until it is finally introduced to the combustor liner  24  through the at least one nozzle  38 . In addition to providing air to the combustor  14  for the combustion process, the relatively cool discharge flow  46  further provides much needed cooling to the components exposed to hot combustion gas, for example, the combustor liner  24  and the transition piece  20 . 
     At the interface between the transition piece and the combustor liner, there is a telescoping fit, where the aft end of the combustor liner is received within the forward end of the transition piece. With reference to  FIG. 2 , an annular spring-finger seal  52 , also known as a hula seal, is located radially between the aft end  54  of the liner  24  and the forward end  22  of the transition piece  20 . Typically, the spring fingers  56  have uniform widths and extend from a solid end or edge  58  of the seal in an axial direction, uniformly spaced about the circumference of the seal edge, separated by slots  60  as best seen in  FIG. 3 . It will be appreciated that the solid edge  58  may be on the upstream or downstream ends of the spring fingers. As in well understood in the art, the seal comprises two or more arcuate segments which, when assembled, form a complete 360° annular seal. 
     In exemplary but nonlimiting embodiments of the invention, the hula seal is reconfigured to direct cooling air to specific high-temperature regions of the liner and/or transition piece identified as having “hot streaks” related to fuel/air ratio (FAR) and combustion swirling angles. In  FIG. 4 , for example, an annular hula seal  62  is formed with discrete groups  64  of two axially-oriented spring fingers  66 ,  68  each, at spaced locations about the circumference of the seal. While the spacing between the groups is shown to be substantially uniform, it will be appreciated that the spacing may vary in asymmetric fashion, based on the location of identified hot streaks. In other words, the groups  64  of spring fingers, and just as importantly, the groups of slots  70  between the spring fingers, may be located and arranged so as to preferentially cool any desired region of the aft end of the liner and/or the forward end of the transition piece. Seal portions  72  between the groups  64  in fact comprise spring fingers of substantially greater width than fingers  66 ,  68 . As such, the larger-width spring fingers may also be used/arranged to divert cooling air away from identified cooler regions of the liner or transition piece toward the hot regions so as to promote cooling uniformity without the need for additional cooling air. 
       FIG. 5  illustrates a further example embodiment of an annular hula seal  74  where the spring fingers  76  and slots  78  are uniformly spaced about the circumference of the seal, but angled relative to a centerline axis CL through the seal to swirl the cooling air passing through the seal. It will be appreciated that the embodiments shown in  FIGS. 4 and 5  can be combined so that discrete groups of spring fingers and associated slots are angled in the same or different directions to not only swirl the cooling air but to also preferentially cool certain liner and or transition piece regions. Here again, spring fingers and slots between the spring fingers can have the same or differential width dimensions. 
     By preferentially targeting specific regions of the adjacent components, (whether hot or cold) through unique seal design, more efficient cooling is provided with minimum air flow. Minimizing cooling flow, in turn, reduces emissions and increases the service life of the components. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.