Abstract:
A combustor includes an end cover with a borehole through the end cover. The combustor further includes an insert in the borehole in the end cover and at least one continuous passage through the end cover and the insert. A ring is fixedly connected to the end cover with a seal between the ring and the insert. A method for repairing a combustor includes fixedly connecting a ring to an end cover and installing a replacement insert in the end cover. The method further includes installing a seal between the ring and the replacement insert.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally involves a combustor and a method for repairing a combustor. In particular, various embodiments of the present invention provide a system or method for modifying or repairing an end cover in the combustor. 
       BACKGROUND OF THE INVENTION 
       [0002]    Combustors are known in the art for igniting fuel with air to produce combustion gases having a high temperature and pressure. For example, gas turbine systems, aircraft engines, and numerous other combustion-based systems may include one or more combustors that mix a working fluid, such as air, with fuel and ignite the mixture to produce high temperature and pressure combustion gases. The combustion gases may then be used to rotate a turbine, provide thrust, or perform various other forms of work. 
         [0003]    Each combustor generally includes an end cover and a liner that surround and define a combustion chamber, and the working fluid may flow along the outside of the liner to remove heat from the liner before flowing into the combustion chamber through one or more nozzles. The nozzles may be radially arranged in or connected to the end cover, and fuel may be supplied to the nozzles through the end cover for injection into the combustion chamber. For example, passages through the end cover may connect to complementary passages in the nozzles to provide fluid communication through the end cover and nozzles to the combustion chamber. An insert between the end cover and each nozzle may enable a single end cover design to accommodate several different passages to supply air, fuel, and/or other fluids to the fuel nozzle. The insert may be attached to the end cover by bolts, brazing, or weld joints, and each nozzle may then be bolted or otherwise attached to the insert and/or the end cover to complete the fluid pathway through the end cover, insert, and each nozzle. 
         [0004]    Temperature changes associated with the combustor may produce uneven expansion between the end cover and the insert. Over time, the braze or weld joints between the end cover and the insert may crack or fail, possibly resulting in internal leakage between the various passages in the end cover and/or insert. For some end cover designs, the braze or weld joints may be removed and replaced by one or more seals between the end cover and the insert, as disclosed in U.S. Pat. No. 7,134,287, assigned to the same assignee as the present invention. However, geometric constraints preclude adequate seating surfaces for the replacement seals in some end cover designs. Therefore, a new combustor design that allows for replacement or repair of one or more braze or weld joints in the end cover would be useful. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0005]    Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
         [0006]    One embodiment of the present invention is a combustor that includes an end cover with a borehole through the end cover. The combustor further includes an insert in the borehole in the end cover and at least one continuous passage through the end cover and the insert. A ring is fixedly connected to the end cover with a seal between the ring and the insert. 
         [0007]    Another embodiment of the present invention is a combustor that includes an end cover and a nozzle connected to the end cover. The combustor further includes an insert between the end cover and the nozzle and at least one continuous passage through the end cover and the insert. A ring is fixedly connected to the end cover with a seal between the ring and the insert. 
         [0008]    The present invention also includes a method for repairing a combustor. The method includes fixedly connecting a ring to an end cover and installing a replacement insert in the end cover. The method further includes installing a seal between the ring and the replacement insert. 
         [0009]    Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
           [0011]      FIG. 1  is a simplified cross-section view of a combustor according to one embodiment of the present invention; 
           [0012]      FIG. 2  is an enlarged cross-section view of a portion of the end cover shown in  FIG. 1 ; 
           [0013]      FIG. 3  is an enlarged cross-section view of the end cover shown in  FIG. 2  with the insert substantially removed; 
           [0014]      FIG. 4  is an enlarged cross-section view of the end cover shown in  FIG. 3  with a replacement insert installed in the end cover according to one embodiment of the present invention; 
           [0015]      FIG. 5  is an enlarged cross-section view of the seal shown in  FIG. 4  according to one embodiment of the present invention; and 
           [0016]      FIG. 6  is an enlarged cross-section view of the seal shown in  FIG. 4  according to an alternate embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. 
         [0018]    Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
         [0019]      FIG. 1  shows a simplified cross-section view of a combustor  10  according to one embodiment of the present invention. A casing  12  may surround the combustor  10  to contain the air or working fluid flowing to the combustor  10 . As shown, the combustor  10  may include one or more nozzles  14  radially arranged in a top cap  16 . An end cover  18  and a liner  20  generally surround a combustion chamber  22  located downstream of the nozzles  14 . A flow sleeve  24  with flow holes  26  may surround the liner  20  to define an annular passage  28  between the flow sleeve  24  and the liner  20 . The air or working fluid may pass through the flow holes  26  in the flow sleeve  24  to flow along the outside of the liner  20  to provide film or convective cooling to the liner  20 . The air or working fluid then reverses direction to flow through the one or more nozzles  14  where it mixes with fuel before igniting in the combustion chamber  22  to produce combustion gases having a high temperature and pressure. 
         [0020]      FIG. 2  shows an enlarged cross-section view of a portion of the end cover  18  shown in  FIG. 1  before the improvements included in various embodiments of the present invention. As shown, the end cover  18  may include one or more boreholes  30  and continuous passages  32  that extend through the end cover  18 . The boreholes  30  and continuous passages  32  provide fluid communication through the end cover  18  to allow a fuel, a diluent, an inert gas, or other fluid to flow through the end cover  18  to the nozzle  14 . As shown in  FIG. 2 , in particular embodiments the borehole  30  may be stepped in the axial direction, resulting in varying diameters of the borehole  30  through the end cover  18  that provide convenient seating surfaces between the end cover  18  and an insert  34 . The insert  34  may be installed in the borehole  30  and connected to the end cover  18  by bolts or one or more braze  36  or weld joints, and the nozzle  14  may be connected to the end cover  18  and/or insert  34  downstream of the insert  34  so that the insert  34  is between the end cover  18  and the nozzle  14 . In this manner, fluids in the borehole  30  and/or passages  32  may flow through the insert  34  to the nozzle  14 , and the braze  36  or weld joints between the insert  34  and the end cover  18  may provide a suitable boundary to prevent co-mingling or mixing of the fluids in the borehole  30  and/or passages  32 . 
         [0021]    During transient or extended operations, temperature gradients between the end cover  18  and the insert  34  may weaken or damage the braze  36  or weld joints between the end cover  18  and the insert  34 . As a result, leaks may develop between the borehole  30  and the passages  32 , allowing co-mingling or mixing of the fluids in the borehole  30  and/or passages  32 . Although the combustor  10  may continue to operate with some amount of leakage between the borehole  30  and various passages  32 , any leakage may compromise the combustor operation by altering the designed fluid flow through the nozzle  14 . The weakened or damaged braze  36  or weld joints may be difficult to inspect and detect, and once detected, the spatial or geometric limitations inside the borehole  30  may make conventional repairs difficult or impractical without replacing the entire end cover  18 . Various embodiments of the present invention provide a system and method for modifying a new or existing end cover  18  that replaces or repairs one or more existing braze  36  or weld joints with a ring  40 . The ring  40  typically has a lower stiffness than the original insert  34 , resulting in lower tensile stresses between the ring  40  and the end cover  18 . In addition, due to the removal or repair of one or more braze  36  or weld joints, the ring  40  may be more accessible to subsequent inspection and repairs, if necessary. As a result, the end cover  18  may be modified or repaired to couple the end cover  18  to the nozzle  14  without requiring a redesigned or replacement end cover  18 , producing substantial savings in repair or replacement costs. 
         [0022]      FIG. 3  provides an enlarged cross-section of the end cover  18  shown in  FIG. 2  with the original insert  34  removed. The original insert  34  and any weakened or damaged braze  36  or weld joints may be substantially removed from the borehole  30 , for example by grinding or machining, leaving in place one or more rings  40  from the original insert  34  and associated braze  36  or weld joints that are still functioning. Alternately, as shown in  FIG. 3 , the original insert  34  and all associated braze  36  or weld joints may be completely removed and replaced with one or more rings  40  fixedly connected to the end cover  18 . Each ring  40 , whether a remnant from the original insert  34  or a new piece, may comprise a hoop that is brazed or welded to the end cover  18  as before. The reduced mass and open geometry of each ring  40  reduces the stiffness of each ring  40 , resulting in a corresponding reduction in the tensile stress between each ring  40  and the end cover  18 . In addition, each ring  40  provides a convenient surface to mate with a replacement insert  42  while still preserving the continuous passages  32  through the end cover  18  and replacement insert  42 . 
         [0023]      FIG. 4  provides an enlarged cross-section of the end cover  18  shown in  FIG. 3  with the replacement insert  42  installed in the end cover  18  according to one embodiment of the present invention. As shown in  FIG. 4 , the replacement insert  42 , costing far less than a replacement end cover  18 , may be inserted into the borehole  30 . A seal  44  between each ring  40  and the replacement insert  42  provides a suitable boundary to prevent co-mingling or mixing of the fluids in the borehole  30  and/or passages  32 . The seal  44  may comprise an annular metal ring having a generally W-shaped or C-shaped cross-section that allows the seal  44  to readily flex in response to relative movement between the replacement insert  42  and the associated ring  40 . The nozzle  14  may again be connected to the end cover  18  and/or replacement insert  42  downstream of the replacement insert  42  so that the replacement insert  42  is between the end cover  18  and the nozzle  14 . In this manner, fluids in the borehole  30  and/or passages  32  may flow through the replacement insert  42  to the nozzle  14  as before, and the combination of the rings  40  and seals  44  between the replacement insert  42  and the end cover  18  provide a suitable boundary to prevent co-mingling or mixing of the fluids in the borehole  30  and/or passages  32 . 
         [0024]      FIGS. 5 and 6  provide enlarged cross-sections of the seals  44  shown in  FIG. 4  according to various embodiments of the present invention. As shown in  FIGS. 5 and 6 , the seals  44  prevent fluid flow across the seals  44  during expansion or contraction of the adjacent surfaces. Specifically,  FIG. 5  shows that the W-shaped seal  44  between the ring  40  and the replacement insert  42  allows the ring  40  and the replacement insert  42  to expand or contract during operation without allowing fluid flow across the seal  44 . Similarly,  FIG. 6  shows that the C-shaped seal  44  may replace an existing braze or weld joint between the end cover  18  and the replacement insert  42 . 
         [0025]    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 the claims if they include 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 languages of the claims.