Abstract:
A combustion cap plate is disclosed. The combustion cap plate includes: a plate having a planar surface and configured to be affixed to an assembly connected to a turbine combustion chamber, the plate defining a central axis perpendicular to the planar surface; a plurality of openings through the plate; and a plurality of raised portions formed by the plate. The raised portions each extend away from the planar surface in a direction of the central axis and having a shape conforming to a thermal gradient incident on the plate during a combustion process.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to gas turbines and, more particularly, to combustion cap assemblies used in gas turbines. 
         [0002]    Combustion cap assemblies are utilized in gas turbines to deliver fuel and air from fuel nozzles to a combustion chamber in the turbines. Combustion cap assemblies typically include a cap plate through which fuel nozzles deliver fuel and air. 
         [0003]    Current cap plates have low cycle and high cycle life limitations. The life limitations are in the form of cracks in the cap plate. Some of the cracking experienced is initiated from low cycle fatigue due to severe thermal gradients caused by proximity to flames in the combustion chamber. Some of the cracking is also due to high cycle fatigue because the relatively low stiffness of the cap plate allows it to be deflected by combustion pressure pulsations. 
         [0004]    Some designs attempting to extend the life limitations include thickening the plate to make it have higher life and greater stiffness. This increased thickness makes it harder to manufacture and increases cost. The increased thickness may also lead to a discontinuity where a thicker plate is attached to a thinner plate. Other designs use a covering plate or a shield that is attached to the cap. In these designs, the hotter shield can grow independent of the colder cap structure. Devices including such shields require more parts, complexity and cost than systems with a single cap plate. Accordingly, there is a need for cap assemblies that have improved durability and lifetimes without significant additional cost or complexity. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    A combustion cap plate constructed in accordance with exemplary embodiments of the invention includes: a plate having a planar surface and configured to be affixed to an assembly connected to a turbine combustion chamber, the plate defining a central axis perpendicular to the planar surface; a plurality of openings through the plate; and a plurality of raised portions formed by the plate, the raised portions each extending away from the planar surface in a direction of the central axis and having a shape conforming to a thermal gradient incident on the plate during a combustion process. 
         [0006]    Other exemplary embodiments of the invention include a system for supplying combustible material to a gas turbine. The system includes: an outer sleeve connectable to a combustion chamber in the gas turbine; a plate having a planar surface and defining a central axis perpendicular to the planar surface, the plate including a plurality of fuel nozzle openings through the plate; and a plurality of fuel nozzle cups affixed in alignment with the plurality of openings. The plate has a plurality of raised portions, the raised portions each extending away from the planar surface in a direction of the central axis and having a shape conforming to a thermal gradient incident on the plate during a combustion process. 
         [0007]    Additional features and advantages are realized through the techniques of exemplary embodiments of the invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features thereof, refer to the description and to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a side cross-sectional view of a gas turbine in accordance with an exemplary embodiment of the invention; 
           [0009]      FIG. 2  is an enlarged cross-sectional view of an exemplary combustor assembly of the gas turbine assembly of  FIG. 1 ; 
           [0010]      FIG. 3  is a front perspective view of an exemplary embodiment of a combustion cap; 
           [0011]      FIG. 4  is a close-up front perspective view of the combustion cap of  FIG. 3 ; 
           [0012]      FIG. 5  is a close-up rear perspective view of the combustion cap of  FIG. 3 ; 
           [0013]      FIG. 6  is a front perspective view of another exemplary embodiment of a combustion cap; 
           [0014]      FIG. 7  is a close-up front perspective view of the combustion cap of  FIG. 6 ; 
           [0015]      FIG. 8  is a close-up rear perspective view of the combustion cap of  FIG. 6 ; 
           [0016]      FIG. 9  is a front perspective view of another exemplary embodiment of a combustion cap; 
           [0017]      FIG. 10  is a close-up front perspective view of the combustion cap of  FIG. 9 ; and 
           [0018]      FIG. 11  is a close-up rear perspective view of the combustion cap of  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    With reference to  FIG. 1 , a gas turbine assembly constructed in accordance with an exemplary embodiment of the invention is indicated generally at  10 . The gas turbine  10  includes a compressor assembly  12 , a combustor assembly  14 , a turbine assembly  16  in fluid communication with the combustor assembly  14  and the compressor assembly  12 , and a rotor shaft  18  attached to the compressor assembly  12  and the turbine assembly  16 . In operation, air flows through the compressor assembly  12  and is discharged to the combustor assembly  14  that injects fuel into the air flow and ignites the fuel/air mixture to generate a high temperature combustion gas stream. The combustion gas stream is discharged toward the turbine assembly  16 , which is rotated by the combustion gas stream. 
         [0020]    Referring to  FIG. 2 , an exemplary embodiment of the combustor assembly  14  is shown that includes a substantially circular cover assembly  38  that provides at least partial support to a plurality of fuel nozzles  22 . The cover assembly  38  is coupled to a combustor casing  24  with retention hardware (not shown). A substantially cylindrical combustor liner  26  is positioned within the casing  24  and is supported via the casing  24 . The liner  26  defines a combustion chamber  28 . A substantially circular cap assembly  20  defines one end of the combustion chamber  28  and provides entry openings for the fuel nozzles  22 . 
         [0021]    A transition portion  30 , also referred to as a transition piece  30 , is coupled to the combustor casing  24  and facilitates channeling combustion gases generated in the chamber  28  to a turbine nozzle  32 . Fuel and air are mixed and ignited within the combustion chamber  28 . The resultant combustion gases  34  are channeled from the chamber  28  toward and through a combustion gas stream guide cavity  36  that channels the combustion gas stream towards the turbine nozzle  32 . 
         [0022]    The cap assembly  20  includes a combustion cap plate  40 , which includes a plurality of openings for accommodating the fuel nozzles  22 . The cap plate  40  includes a plurality of fuel nozzle openings  42 ,  44 . A plurality of fuel nozzle cups or tubes are affixed in alignment with the fuel nozzle openings  42 ,  44 . 
         [0023]    Referring to  FIGS. 3-5 , the combustion cap assembly  20  includes the cap plate  40  having multiple openings through which fuel nozzles deliver fuel and air. The cap plate  40  includes a flat circular body  46  and a plurality of openings  42 ,  44 . 
         [0024]    Referring to  FIGS. 6-8 , an embodiment of the cap plate  40  is shown. In this embodiment, the cap plate  40  is a flat plate including a planar surface  46  having thereon a plurality of the fuel nozzle openings  42 ,  44 . In this embodiment, the fuel nozzle openings  42 ,  44  include five primary or outer fuel nozzle openings  44 , also referred to as “peripheral openings”, and a center fuel nozzle opening  42 , also referred to as a “central opening”. The numbers and positions of the fuel nozzle openings  42 ,  44  described in the embodiments herein are exemplary and not limited. Also in this embodiment, the fuel nozzle openings  42 ,  44  have a circular shape, although any suitable shape may be utilized as needed. The cap plate  40 , in one embodiment, is made from any metallic material suitable for use in the conditions created by the turbine  10 . 
         [0025]    The planar surface  46  defines a plane that is perpendicular to a central axis  48 . In one embodiment, the central opening  42  is symmetrical about the central axis  48 . In one embodiment, the peripheral openings  44  are circumferentially positioned on the surface  46 , that is, the center of each peripheral opening is located on a circumference formed symmetrically around the central axis  48 . 
         [0026]    In one embodiment, the surface  46  includes a plurality of raised portions  50  extending away from the surface  46  in a direction offset from a radial line eminating from the central axis  48 . In one embodiment, the raised portions  50  maintain substantially the same thickness as the thickness of at least the flat portion of the plate  40 . 
         [0027]    The raised portions  50  decrease stresses from thermal conditions introduced by combustion processes, by changing the shape of the cap plate  40  into a shape that is more compliant to the directions of thermal deflections caused by the combustion process. This design also causes the plate  40  to stiffen to make it less sensitive to resonances from driving forces caused by the combustion. The shapes of the raised portions  50  are configured to absorb the thermal loads by allowing for out-of-plane thermal growth, i.e., growth away from the planar surface  46 . The shapes are constructed based on the thermal loading patterns that exist, however they can be adapted to suit other thermal patterns. In one example, the shapes of the raised portions  50  conform to the thermal deflections. 
         [0028]    The cap plate  40  is exposed to severe thermal gradients due to its proximity to flame in the turbine combustion chamber, as well as to cyclic thermal loading from turning the flame on and off. Thermally hot regions of the metallic plate  40  form adjacent to thermally cold regions. In prior plates, the thermally hot regions strain against the thermally cold regions, referred to as “thermal fight”. The cap plates  40  including the raised portions  50  reduce or eliminate thermal flight. 
         [0029]    For example, during combustion, the plate  40  develops “hot” portions and “cool” portions. Hot portions are any area of the surface  46  having a significantly higher temperature than other portions, i.e., cool portions, of the surface  46 . The hot portions are subject to a higher thermal load than the cool portions. The raised portions  50  are shaped to at least partially conform to the shape of a corresponding hot portion, which allows the material in the hot portion to expand away from the surface  46  and prevent thermal fight between hot and cold portions. By preventing thermal fight, the risk and incidence of cracks is significantly reduced or eliminated. 
         [0030]    In one exemplary embodiment, the plurality of raised portions  50  form a plurality of elongated protrusions  50 , such as the elongated troughs shown in  FIGS. 6-8 . In another embodiment, the elongated protrusions  50  form pairs resulting in a “V” shape that is symmetrical about a radial direction extending perpendicularly from the central axis  48  on the planar surface  46 . In one embodiment, a pair of elongated protrusions  50  is disposed between each pair of peripheral openings  44 . 
         [0031]    In one exemplary embodiment, the elongated protrusions  50  are raised inwardly, i.e., in a direction toward the combustion chamber  28  and toward the rear of the plate  40  when the plate  40  is assembled on the turbine  10 . This is shown in the front view of  FIG. 7  and the rear view of  FIG. 8 . In other embodiments, the elongated protrusions  50  are raised outwardly, i.e., in a direction away from the combustion chamber  28  and toward the front of the plate  40  when the plate  40  is assembled on the turbine  10 . 
         [0032]    Referring to  FIGS. 9-11 , another exemplary embodiment of the plate  40  is shown. In this embodiment, the raised portions  50  are a plurality of pyramidal protrusions  50  extending from the surface  46 . The shape of each pyramidal protrusion  50  generally conforms to all or part of each corresponding hot portion. In one embodiment, the pyramidal protrusions  50  are each symmetrical about a radial direction extending perpendicularly from the central axis  48  on the planar surface  46 . In one embodiment, a pyramidal protrusion  50  is disposed between each pair of peripheral openings  44 . 
         [0033]    In one embodiment, the pyramidal protrusions  50  are raised inwardly, i.e., in a direction toward the combustion chamber  28  and toward the rear of the plate  40  when the plate  40  is assembled on the turbine  10 . This is shown in the front view of  FIG. 9  and the rear view of  FIG. 10 . In other embodiments, the pyramidal protrusions  50  are raised outwardly, i.e., in a direction away from the combustion chamber  28  and toward the front of the plate  40  when the plate  40  is assembled on the turbine  10 . 
         [0034]    Although the exemplary embodiments herein describe elongated shapes and pyramidal shapes, the shape of the raised portions  50  are not limited to these embodiments. The raised portions may take any desired shape that encompasses all or part of a hot portion of the surface  46 . 
         [0035]    The devices and systems described herein provide numerous advantages over prior art systems. For example, the devices and systems provide the technical effect of improving the robustness and durability, and correspondingly the lifetime, of a cap assembly plate without requiring changes in thickness or additional components. The devices and systems reduce stress on the cap plate due to thermal fight between portions subject to different loads. Furthermore, the increased stiffness of the plate cap provides for increased resistance to pressure fluctuations produced during the combustion process. Accordingly, the devices and systems described herein provide for increased lifetimes without the introduction of significant complexity or cost. 
         [0036]    The capabilities of the embodiments disclosed herein can be implemented in software, firmware, hardware or some combination thereof. As one example, one or more aspects of the embodiments disclosed can be included in an article of manufacture (e.g., one or more computer program products) having, for instance, computer usable media. The media has embodied therein, for instance, computer readable program code means for providing and facilitating the capabilities of the present invention. The article of manufacture can be included as a part of a computer system or sold separately. Additionally, at least one program storage device readable by a machine, tangibly embodying at least one program of instructions executable by the machine to perform the capabilities of the disclosed embodiments can be provided. 
         [0037]    In general, this written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of exemplary embodiments of the invention if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.