Combustor and a method for repairing a combustor   

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.

FIELD OF THE INVENTION

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

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.

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.

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.

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.

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.

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.

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.

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

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:

FIG. 1 is a simplified cross-section view of a combustor according to one embodiment of the present invention;

FIG. 2 is an enlarged cross-section view of a portion of the end cover shown in FIG. 1;

FIG. 3 is an enlarged cross-section view of the end cover shown in FIG. 2 with the insert substantially removed;

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;

FIG. 5 is an enlarged cross-section view of the seal shown in FIG. 4 according to one embodiment of the present invention; and

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

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.

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.

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.

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.

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.

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.

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.

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.

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.