Method of repairing tube in tube bundle fuel injector

Abstract

A method of repairing a fuel injector (100) including a plurality of pre-mix tubes (118) each extending from a fuel plenum (120) to an outlet portion (144), the method including: removing the outlet portion from at least one pre-mix tube to define an exposed tip portion (204); machining an inner surface (158) of the at least one premix tube at the exposed end portion to form an increased inner diameter (D2) relative to an inner diameter (D1) of the premix tube upstream of the exposed end portion; and coupling a tube tip (156) to the exposed tip portion.

Description

Background Art

[0001] The field of the invention relates generally to tube bundle fuel injectors used in rotating machines and, more particularly, to a method of repairing one or more premixing tubes of a tube bundle fuel injector.

[0002] Gas turbine engines are widely used in industrial and power generation operations. Conventional gas turbine engines include a compressor section, a combustor section downstream of the compressor section, and a turbine section downstream of the combustor section. A working fluid, such as ambient air, flows into the compressor section where it is compressed before flowing into the combustor section. The compressed working fluid is mixed with fuel and combusted within the combustor section to produce combustion gases that expand through the turbine section to rotate a shaft, thereby generating electricity.

[0003] In at least some known gas turbine engines, the combustion section includes one or more burners annularly spaced apart between the compressor section and the turbine section. At least some known burner designs include one or more axially extending tube-bundle fuel injectors located upstream of the combustion chamber. The fuel injectors facilitate mixing the fuel and the compressed working fluid before the mixture is directed toward the combustion chamber. The tube-bundle fuel injectors typically include a plurality of premixing tubes that are radially and circumferentially arranged across the fuel injectors. The premixing tubes extend generally parallel to each other between the fuel distribution module of the tube-bundle fuel injector and the combustion chamber.

[0004] In operation, the compressed working fluid is delivered from the compressor section through the inlet of each premixing tube in the premixing tube upstream of the fuel distribution module. The fuel is supplied to the fuel distribution module and is injected into the premixing tube through one or more fuel ports. The fuel and the compressed working fluid are mixed in the premixing tube before being directed into the combustion chamber. Because the downstream ends of the premixing tubes are exposed to extreme temperatures due to their proximity to the combustion chamber and / or the combustion flame, the downstream ends of the premixing tubes may be damaged over time. Typically, damage is the result of thermal stress and oxidation, and requires regular inspection and, in some cases, repair of the bundle fuel injector.

[0005] However, existing methods for repairing tube-bundle fuel injectors are limited. For example, in some cases, the damaged downstream end is typically removed and replaced by a tube tip connected to the retained portion of the premixing tube via known techniques (including brazing, welding, adhesive coating, etc.). However, the material used to connect the tube tip to the retained portion of the premixing tube (e.g., brazing filler material or welding filler material) may accumulate in the premixing tube. Additionally or alternatively, due to manufacturing tolerances, there may be some axial offset between the premixing tip and the corresponding tube tip. The accumulated material within the axial offset between the premixing tube and the corresponding tube tip may prevent or restrict the flow of the fuel-working fluid mixture through it. This in turn may create the opportunity for combustion flame interruption, which reduces the performance, efficiency and / or life of the burner.

[0006] Therefore, there is a need for improved methods of repairing damaged tubes in a tube bundle fuel injector. In particular, it is desirable to repair a tube bundle fuel injector without substantially reconfiguring or redesigning the existing premixer tubes, while also repairing the tube bundle fuel injector in a manner that helps reduce or eliminate any chance of the tube tip connection interrupting the combustion flame stability within the combustor. Summary of the invention

[0007] In one aspect, a method of repairing a fuel injector including a plurality of premixer tubes, each of which extends from a fuel plenum to an outlet portion, is provided. The method includes: removing the outlet portion from at least one premixer tube to define an exposed end portion; machining an inner surface of the at least one premixer tube at the exposed end portion to form an increased inner diameter relative to an inner diameter of the premixer tube upstream of the exposed end portion; and coupling a tube tip to the exposed end portion.

[0008] In another aspect, a method of repairing a fuel injector having a plurality of premixer tubes is provided, each premixer tube extending downstream from a fuel plenum to an outlet portion. The method includes: removing the outlet portion from the premixer tube to define an exposed end portion; machining an inner surface of the premixer tube at the exposed end portion to produce an inwardly tapered machined surface, the machined surface having an inner diameter at the exposed end portion that is greater than an inner diameter upstream of the exposed end portion; and coupling the tube tip to the exposed end portion to form a joint between the tube tip and the exposed end portion, wherein the tube tip has an inwardly tapered surface extending between the joint and the inner surface of the tube tip, and wherein the inwardly tapered surface of the tube tip is complementary to the inwardly tapered machined surface to define a larger inner diameter at the joint.

[0009] In another aspect, a method of repairing a fuel injector including a plurality of premixer tubes, each of which extends from a fuel plenum to an outlet portion, is provided. The method includes: removing the outlet portion from the plurality of premixer tubes along a cut line to define an exposed end portion of the plurality of premixer tubes; machining an inner surface of each premixer tube at the exposed end portion to form an increased inner diameter relative to an inner diameter of the premixer tube upstream of the exposed end portion; and coupling a tube tip to each exposed end portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] These and other features, aspects and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters refer to like parts throughout the several views, and in which:

[0011] Figure 1 is a schematic diagram of an exemplary gas turbine system;

[0012] Figure 2 To be included Figure 1 A simplified cross-sectional side view of an exemplary combustor in a gas turbine engine of;

[0013] Figure 3 To be included Figure 2 A perspective view of an exemplary tube bundle fuel injector in a combustor of

[0014] Figure 4 for Figure 2 a rear perspective view of a fuel injector shown;

[0015] Figure 5 for Figure 2 A side view of a fuel injector is shown;

[0016] Figure 6 for Figure 2 A schematic cross-sectional side view of a fuel injector is shown;

[0017] Figure 7 is an enlarged cross-sectional side view of an exemplary tube tip of a remaining portion of a premixer tube fixedly coupled to a fuel injector after removal and machining operations;

[0018] Figure 8 is an enlarged cross-sectional side view of yet another exemplary tube tip fixedly coupled to a remaining portion of a premixer tube after removal and machining operations;

[0019] Fig. 9 is an enlarged cross-sectional side view of another exemplary tube tip fixedly coupled to a retained portion of a premixer tube after removal and machining operations;

[0020] Fig.10 for Fig. 9 An enlarged view of the section C1 indicated by a dotted line in FIG.

[0021] Fig.11 is an enlarged cross-sectional side view of yet another exemplary tube tip fixedly coupled to a remaining portion of a premixer tube after removal and machining operations; and

[0022] Fig.12 An exemplary method 600 is provided for repairing a fuel injector including a plurality of premixer tubes.

[0023] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings.

[0024] Unless otherwise indicated, the drawings provided herein are intended to illustrate features of the embodiments of the present disclosure. It is believed that these features are applicable to a variety of systems including one or more embodiments of the present disclosure. Therefore, the drawings are not intended to include all conventional features required for practicing the embodiments disclosed herein known to those of ordinary skill in the art. DETAILED DESCRIPTION

[0025] Embodiments described herein relate to methods for repairing a tube-bundle fuel injector used in a combustor of a rotary machine (e.g., a gas turbine engine). An exemplary fuel injector includes a plurality of premixing tubes extending between a fuel plenum and an outlet portion. Fuel is injected into each premixing tube in the fuel plenum, and the fuel is mixed with a compressed working fluid in the premixing tube to form a flammable mixture. The outlet portion of the premixing tube defines an outlet through which the flammable mixture is directed toward the combustion chamber. The outlet portion of the premixing tube is exposed to extreme temperatures and high mechanical loads during combustion, which may cause the outlet portion to be damaged over time due to, for example, thermal stress and oxidation. The method described herein includes removing a damaged outlet portion of one or more premixing tubes in the premixing tube, and replacing each removed outlet portion with a tube tip to repair or refurbish the premixing tube.

[0026] The connection created between the tube tip and the premixing tube can promote the obstruction or restriction of the flow of the flammable mixture through it, which can interrupt the combustion flame in the combustion chamber and / or reduce the flame stability in the burner. For example, the tube tip can be connected to the premixing tube via brazing, welding, adhesive coating, etc., and any filler material used to join the components may unexpectedly accumulate in the premixing tube and / or the tube tip. The accumulated material may hinder or restrict the flow, or may otherwise produce flow disturbances of the flammable mixture. In addition, due to manufacturing tolerances, the premixing tube and the tube tip may operate with some offset in the axial alignment between the two, which may hinder or restrict the flow, or otherwise produce flow disturbances of the flammable mixture.

[0027] Exemplary methods described herein include machining the exposed end portion of the premixing tube after removing the damaged outlet portion, to produce a suitable configuration of the premixing tube, which is conducive to reducing or eliminating the connection between the premixing tube and the tube tip that hinders or limits the chance of the flammable mixture passing through its flow. For example, at the exposed end where the tube tip is attached, the premixing tube can be machined into an increased diameter, and the increased diameter provides additional internal space for the filling material for connecting the tube tip and the premixing tube to accumulate, and the accumulation will not cause obstacles to the flammable mixture flowing through the premixing tube and the tube tip. The increased diameter is also conducive to reducing or eliminating any negative effects that the axial alignment offset between the premixing tube and the tube tip may otherwise produce on the flammable mixture passing through it. Therefore, the premixing tube can be repaired or renovated with the corresponding tube tip in a manner to maintain the performance, efficiency and / or life of the burner.

[0028] When introducing the elements of the various embodiments disclosed herein, the articles "one", "a", "the" and "said" are intended to mean one or more elements present in the elements and include plural references unless the context clearly indicates otherwise. "Optional" or "optionally" means that the event or situation described subsequently may or may not occur, and the description includes instances where the event occurs and instances where the event does not occur. In addition, reference to "an embodiment" is not intended to be interpreted as excluding the existence of additional embodiments that also include the listed features. In addition, unless there is a clear statement to the contrary, the terms "including", "comprising" and "having" are intended to be inclusive and mean that there may be additional elements in addition to the listed elements.

[0029] Unless otherwise indicated, approximate language as used herein, such as "substantially," "substantially," "approximately," and "about" indicate that, as one of ordinary skill in the art will recognize, the term so modified may apply only to an approximate degree, rather than an absolute or perfect degree. Thus, a value modified by one or more terms, such as "about," "approximately," and "substantially," is not limited to the precise value specified. In at least some cases, the approximate language may correspond to the precision of an instrument used to measure the value.

[0030] Unless otherwise indicated, the terms "first," "second," and the like are used herein merely as labels and are not intended to impose order, position, or hierarchical requirements on the items to which these terms refer. Furthermore, for example, reference to a "second" item does not require or preclude the existence of, for example, a "first" or lower numbered item or a "third" or higher numbered item.

[0031] The terms "upstream" and "downstream" refer to relative directions with respect to the flow of a fluid in a fluid pathway. For example, "upstream" refers to the direction from which the fluid is flowing, and "downstream" refers to the direction toward which the fluid is flowing. Directional terms such as "radially," "axially," "circumferentially," "forwardly," and "rearwardly" are used merely for ease of description and are not limited to any particular orientation unless the context clearly indicates otherwise.

[0032] Now referring to the accompanying drawings, Figure 1 is a schematic cross-sectional view of an exemplary gas turbine engine 10. The gas turbine engine 10 includes a compressor section 12 including an inlet 14 defined at an upstream end 15 of the gas turbine engine 10, and a casing 16 at least partially surrounding the compressor section 12. The gas turbine engine 10 also includes a combustion section 18 including a combustor 20 downstream of the compressor section 12, and a turbine section 22 downstream of the combustion section 18. An outer casing 17 at least partially surrounds the turbine section 22. A rotor shaft 24 extends axially through the gas turbine engine 10. The combustion section 18 may include a plurality of combustors 20.

[0033] In operation of the gas turbine engine 10, a working fluid (e.g., air) 26 is drawn into the inlet 14 of the compressor section 12 and is progressively compressed to provide a compressed working fluid 28 to the combustion section 18. The compressed working fluid 28 flows into the combustion section 18 and mixes with a fuel 29 in the combustor 20 to form a combustible mixture. The combustible mixture is combusted in the combustor 20, thereby generating hot gases 30, which flow from the combustor 20 into the turbine section 22, flow through a turbine nozzle 34 and a first stage 32 of turbine blades 36. The hot gases 30 flow through the turbine nozzle 34 along the axial centerline C of the shaft 24. L The shaft 24 is coupled to the turbine blades 36 and the alternating stages of the turbine nozzles 34 within the turbine section 22 (e.g., the first stage 32 and the second stage 33 downstream of the first stage 32) when expanding rapidly. Thermal energy and / or kinetic energy is transferred from the hot gases to each stage of the turbine blades 36, thereby causing the shaft 24 to rotate and produce mechanical work. The shaft 24 may be coupled to a load such as a generator (not shown) to produce electricity. In addition, or alternatively, the shaft 24 may be used to drive the compressor section 12 of the gas turbine engine 10.

[0034] Figure 2 For a gas turbine engine 10 ( Figure 1 ) is a simplified cross-sectional side view of a combustor 20 in a compressor section 12. The combustor 20 includes an exemplary tube bundle fuel injector 100. The combustor 20 is at least partially surrounded by an outer casing 38. The outer casing 38 at least partially forms a high pressure plenum 40 surrounding the combustor 20. The high pressure plenum 40 may be connected to the compressor section 12 ( Figure 1) or other source for supplying compressed working fluid 28 to the combustion section 18. An end cover 42 is coupled to the outer casing 38. The end cover 42 may be in fluid communication with a fuel supply 44 that directs the fuel 29 toward the combustion section 18.

[0035] The tube bundle fuel injector 100 extends downstream from the end cover 42 and may be fluidly connected to the end cover 42. The fuel injector 100 receives the fuel 29 from the fuel supply 44, and the fluid conduit 46 may fluidly couple the end cover 42 and / or the fuel supply 44 with the tube bundle fuel injector 100. An annular liner 48, such as a combustion liner and / or a transition duct, surrounds one end of the downstream end 102 of the tube bundle fuel injector 100 and at least partially defines the combustion chamber 50 within the combustor 20. The liner 48 at least partially defines a hot gas path 52 that directs the hot gases 30 from the combustion chamber 50 through the combustor 20. The hot gas path 52 may direct the hot gases 30 toward the turbine section 22.

[0036] In operation of the combustor 20, the compressed working fluid 28 is directed toward the end cover 42 where it reverses direction and flows through one or more of the tube bundle fuel injectors 100. Fuel 29 is supplied to the tube bundle fuel injectors 100 where the fuel 29 and the compressed working fluid 28 are premixed or combined into a combustible mixture within the tube bundle fuel injectors 100 before the mixture is injected into the combustion chamber 50 for combustion.

[0037] See also Figures 3 to 6 , various views of an exemplary tube bundle fuel injector 100 are shown. For ease of illustration and description, the fuel injector 100 is Figures 3 to 6 is shown simplified. Figure 3 is a perspective view of fuel injector 100 shown coupled to fluid conduit 46 . Figure 4 is a rear perspective view of the fuel injector 100 . Figure 5 is a side view of the fuel injector 100, and Figure 6 is a schematic cross-sectional side view of a fuel injector 100 .

[0038] In the exemplary embodiment, the fuel injector 100 extends axially between an upstream end 104 and a downstream end 102 and defines an axial centerline 106. The fuel injector 100 includes a fuel inlet 108 located at the upstream end 104, which is connected to the fuel supply 44 ( Figure 2 ) provides fluid communication with the fuel dispensing module 110. The fuel dispensing module 110 includes a fuel filling chamber 120 (such as Figure 6The fluid conduit 46 and the fuel inlet 108 are located in the fuel supply device 44 ( Figure 2 ) provides fluid communication with the fuel filling chamber 120. The fuel injector 100 also includes a support plate 114 located upstream of the shroud 112. For simplicity, Figure 4 and Figure 5 The support plate 114 is omitted. The support plate 114 provides a plurality of inlet tubes 116 that extend axially outwardly from the support plate 114 opposite the shroud 112. Each inlet tube 116 is substantially axially aligned with one of a bundle of premixer tubes 118 that extend axially through the shroud 112 opposite the support plate 114 and extend outwardly from the shroud.

[0039] like Figure 6 As shown, the shroud 112 includes a pair of axially spaced first and second plates 122 and 124 that extend generally radially outward and circumferentially relative to the axial centerline 106 of the fuel injector 100. The first and second plates 122 and 124 define a fuel plenum 120 therebetween. An outer band 126 extends axially between the first and second plates 122 and 124 and circumferentially surrounds the fuel plenum 120. Each of the first and second plates 122 and 124 includes tube passages 128 and 130 defined therein, respectively. Each tube passage 128 defined in the first plate 122 is axially aligned with a tube passage 130 defined in the second plate 124 so that a portion of one of the bundle of premixer tubes 118 can extend therethrough. The fuel inlet 108 extends axially outward from the first plate 122. The second plate 124 includes a central nozzle passage 132 extending axially therethrough. Fuel inlet 108 and central nozzle passage 132 are axially aligned along axial centerline 106 of fuel injector 100. Fuel inlet 108 provides access to fuel plenum 120 through first plate 122 and central nozzle passage 132 provides access to fuel plenum 120 through second plate 124.

[0040] The support plate 114 extends radially outward and circumferentially relative to the axial centerline 106 of the fuel injector 100 and is adjacent to the first support plate 122 of the shroud 112 at the upstream end 104 of the fuel injector 100. For ease of illustration, the support plate 114 is Figure 6 1 is shown as being axially spaced apart from the first plate 122 of the shroud 112. When the fuel injector 100 is assembled (eg Figure 3), the support plate 114 is adjacent to the first plate 122 and may abut and / or may be connected to the first plate. The support plate 114 may be coupled to the shield first plate 122 via any suitable means (e.g., welding, brazing, mechanical fasteners, etc.). In certain embodiments, the support plate 114 is removably coupled (e.g., using fasteners) to the first plate 122.

[0041] The support plate 114 includes inlet tubes 116 extending from corresponding tube channels 134 defined in the support plate 114. The inlet tubes 116 each include an open inlet end 117 that communicates with the corresponding tube channel 134. Each tube channel 134 defined in the support plate 114 is substantially axially aligned with the tube channel 128 defined in the first plate 122 to provide fluid communication between the inlet tubes 116 and the corresponding premixing tubes 118. The support plate 114 also includes a central fuel inlet channel 136 extending axially therethrough. The central fuel inlet channel 136 is substantially axially aligned with the fuel inlet 108 and receives the fuel inlet. The fluid conduit 46 ( Figure 3 ) may be coupled to the fuel inlet 108 and / or the central nozzle passage 132 to provide the end cover 42 and / or the fuel supply 44 ( Figure 2 ) and the fuel plenum 120. The fuel inlet 108, the central nozzle passage 132 of the second plate 124, and the central nozzle passage 136 of the support plate 114 are each substantially axially aligned along the axial centerline 106 of the fuel injector 100. A fluid cartridge or fuel nozzle 138 may be coupled to the central nozzle passage 132 and extend axially outward from the shroud 112 toward the combustion chamber 50 ( Figure 2 ).

[0042] The premixer tubes 118 extend generally parallel to each other along or substantially parallel to the axial centerline 106 of the fuel injector 100. The premixer tubes 118 extend axially from the first plate 122 of the shroud 112, through the second plate 124 and toward the combustion chamber 50 ( Figure 2). In particular, a first or inlet portion 140 of each premixing tube 118 extends through the fuel plenum 120 between the first plate 122 and the second plate 124. Similarly, a second or intermediate portion 142 of each premixing tube 118 extends axially outward from the second plate 124, and a third or outlet portion 144 of each premixing tube 118 extends axially outward from the intermediate portion 142 toward the combustion chamber 50. Each premixing tube 118 is disposed or positioned within the axially aligned tube passages 128 and 130 of the shroud 112. The intermediate portion 142 and the outlet portion 144 of the premixing tube 118 may "float," i.e., the tube 118 may extend from the shroud 112 without any additional support fixtures downstream of the shroud 112. In other embodiments, a downstream support plate (not shown) may support tube channels that each receive the intermediate portion 142 and / or outlet portion 144 of a corresponding premixer tube 118 and limit movement thereof in response to vibrations and / or mechanical loads during operation of the combustor 20 .

[0043] The premixer tube 118 may be formed from a single continuous tube, or may be formed from two or more coaxially aligned tubes that are securely coupled together (e.g., by brazing, welding, or another suitable means). Although generally shown as cylindrical, the premixer tube 118 may be any other geometric configuration, and the premixer tube 118 is not limited to having any particular cross-sectional shape unless the context clearly indicates otherwise. In addition, the premixer tubes 118 may be grouped or arranged in a circular, triangular, square, or other geometric configuration, and may be arranged in various numbers and geometries.

[0044] Any number of premixing tubes 118 may be included in the fuel injector 100, and the premixing tubes 118 may be arranged in any suitable arrangement. Figure 4 As shown, the premixing tubes 118 are arranged in a plurality of rows 146. Each row 146 may include one or more of the premixing tubes 118. In one embodiment, each row 146 is radially spaced apart from an adjacent row 146 relative to the axial centerline 106. The premixing tubes 118 of at least some of the rows 146 may be arranged annularly or in an arcuate manner relative to the axial centerline 106. Additionally and / or alternatively, the premixing tubes 118 of at least some of the rows 146 may be arranged linearly and generally perpendicular to the axial centerline 106 of the fuel injector 100.

[0045] Each premixer tube 118 includes an inlet 148 defined in the inlet portion 140 and located upstream of the fuel plenum 120. The inlet is substantially axially aligned with the tube passage 128 in the first shroud plate 122, and thus axially aligned with the corresponding tube passage 134 of the support plate 114 and the inlet tube 116. The inlet 117 of the inlet tube 116 is aligned with the high pressure plenum 40 ( Figure 2 ) and / or compressor section 12 ( Figure 1 ) provide fluid communication between the premixing tubes 118. Each premixing tube 118 also includes an inlet 150 defined in the outlet portion 144 and located downstream of the fuel plenum 120. The outlet 150 of each premixing tube 118 is connected to the combustion chamber 50 ( Figure 2 ) fluid communication. The tube passage 152 extends a distance between the inlet 148 and the outlet 150 of each premixing tube 118. Each premixing tube 118 includes an inner diameter (e.g., Figures 7 to 9 as well as Fig.11 The inner surface 158 of the inner diameter D1 (shown) and the outer diameter (eg, Figures 7 to 9 as well as Fig.11 The outer surface 160 of the premixing tube 118 has an outer diameter D3 as shown. The opposing end surfaces 162, 164 of the premixing tube 118 extend radially between and join the inner surface 158 and the outer surface 160 adjacent the inlet 148 and the outlet 150, respectively.

[0046] In the exemplary fuel injector 100, the premixer tubes 118 are substantially axially coextensive with one another such that the end faces 164 are substantially flush aligned with one another at the downstream end 102 of the fuel injector 100. In other embodiments, the premixer tubes 118 may have different axial lengths, and some of the end faces 164 may extend beyond other end faces 164 at the downstream end 102. The inner diameter D1 and the outer diameter D3 may be substantially constant along the entire axial length of the premixer tubes 118 such that the end faces 162 and 164 have approximately the same radial distance between the inner surface 158 and the outer surface 160, respectively. Alternatively, the inner diameter D1 and / or the outer diameter D3 may vary along the axial length of the premixer tubes 118 such that the respective end faces 162 and 164 define different radial distances between the inner surface 158 and the outer surface 160, respectively. One or more fuel ports 154 are defined in the inlet portion 140 of each premixer tube 118 downstream of the inlet 148. The fuel ports 154 extend radially through an inner surface 158 and an outer surface 160 of the premixer tubes 118 . The fuel ports 154 provide fluid communication between the fuel plenum 120 and corresponding premixer tube passages 152 within the premixer tubes 118 .

[0047] During operation, the compressed working fluid 28 flows through the high pressure plenum 40 and is directed toward the upstream end 104 of the fuel injector 100 and into the inlet 117 of the inlet tube 116. The compressed working fluid 28 is directed through the inlet tube 116 toward the inlet 148 of the premixing tube 118. The fuel 29 is directed into the fuel plenum 120 via the fuel inlet 108. The fuel 29 in the fuel plenum 120 is injected into the premixing tube 118 via the corresponding fuel port 154. The compressed working fluid 28 and the fuel 29 are mixed within the tube passage 152, and the resulting combustible mixture exits each premixing tube 118 via the outlet 150. The combustible mixture is then injected into the combustion chamber 50 for combustion. Some of the fuel 29 entering the fuel plenum 120 may be delivered toward the combustion chamber 50 via the fuel nozzle 138 extending from the central nozzle passage 132. That is, by design, some of the fuel 29 supplied to the fuel injector 100 may bypass the premixing tubes 118 and mix directly with the combustible mixture exiting the fuel injector 100 within the combustion chamber 50 .

[0048] The outlet portions 144 of the premixer tubes 118 are typically exposed to higher temperatures and higher mechanical loads than other portions of the premixer tubes 118 due to their proximity to the combustion chamber 50 and / or the combustion flame. For example, this may increase the likelihood that the outlet portions 144 will become damaged over time due to prolonged exposure to thermal stress and oxidation. In order to repair or refurbish the damaged outlet portions 144 of the premixer tubes 118, the damaged outlet portions 144 may be at least partially removed using any suitable means that enables cutting or otherwise removing tubing. For example, the damaged outlet portions 144 of the premixer tubes 118 may be (at least partially) removed using scoring, electrical discharge machining (EDM), torch cutting, cutting blades, and the like. In some embodiments, the outlet portions 144 of each of the premixer tubes 118 may be at least partially removed in a single cutting operation, wherein the outlet portions 144 of the premixer tubes 118 are cut along a cutting line 166 (e.g., Figure 5 1 ), the cut line being substantially perpendicular to the axial length of the premixer tube 118 and the axial centerline 106 of the fuel injector 100. In other embodiments, the outlet portions 144 of one or some of the premixer tubes 118 may each be at least partially removed while the outlet portions 144 of other premixer tubes 118 are not removed.

[0049] Removing the damaged outlet portion 144 and further machining the premixer tube 118 during and / or after removing the damaged outlet portion 144 (described further below) may increase the risk of additional damage to the premixer tube 118 due to vibration and mechanical loads caused by the cutting and / or machining operations. As described above, in some embodiments, the middle portion 142 and the outlet portion 144 of the premixer tube 118 may float and may not be supported by any additional support fixtures disposed downstream of the shroud 112. A temporary support plate (not shown) may be provided with a tube channel sized to receive some or all of the premixer tubes 118 to provide temporary support to the middle portion 142 and / or the outlet portion 144 of the premixer tube 118, respectively, and to facilitate inhibiting movement of the tube 118 in response to vibration and / or mechanical loads during cutting and / or machining operations when repairing or refurbishing the premixer tube 118. In a single cutting operation, the premixer tube 118 may be cut along the cutting line 166 ( Figure 5 ) in an embodiment where the outlet portion 144 of each of the premixing tubes 118 is at least partially removed, the temporary support plate may suitably include tube channels to receive and support all of the premixing tubes 118. In an embodiment where the outlet portion 144 of one or some (and less than all) of the premixing tubes 118 is each at least partially removed while the outlet portions 144 of other premixing tubes 118 are not removed, the temporary support plate may suitably include a limited number of tube channels that receive and support the premixing tubes 118 within a predetermined or preselected vicinity of the premixing tubes 118 that were individually cut and / or machined.

[0050] The removed outlet portion 144 of one or more of the premixing tubes 118 may then be removed by a tube tip 156 (eg, Figure 4 and Figure 5144) to complete the repair or refurbishment of the premixer tube 118. The tube tip 156 can be securely fixed or coupled to the remaining portion of the premixer tube 118 using any suitable means for joining tubulars. For example, the tube tip 156 can be fixedly coupled to the remaining portion of the premixer tube 118 via furnace brazing, induction brazing, orbital welding, laser welding, friction welding, electron beam welding, diffusion bonding, plasma spraying, heat-resistant adhesives, adhesive coatings, high-velocity oxygen-fuel coating spraying, and / or any combination thereof and / or any other coupling technology that enables the tube 118 to be repaired as described herein. The premixer tube 118, including the tube tip 156, suitably extends the same axial length after repair, such as before removing the damaged outlet portion 144. In embodiments where the premixer tubes 118 are substantially coextensively aligned with each other, as described above, the tube tip 156 suitably maintains a degree of coextension such that the tube tip 156 defining an end face is substantially flush with the end face 164 of the other (i.e., unrepaired) premixer tube 118. In an embodiment where outlet portions 144 are removed collectively along cut line 166 ( Figure 5 ), the tube tips 156 replacing the removed outlet portions 144 can be aligned substantially coextensively and define end surfaces that are substantially flush with each other.

[0051] The tube tip 156 may be made of a different material (e.g., a different metal or metal alloy) than the retained portion of the repaired or refurbished premixer tube 118. In some examples, the tube tip 156 may include at least one of nickel, cobalt, chromium, molybdenum, stainless steel, aluminum, and / or a titanium-based alloy. The tube tip 156 may be suitably made of a high temperature resistant metal or metal alloy. Because the tube tip 156 forms only a portion of the repaired or refurbished premixer tube 118, the tube tip 156 may be made of a relatively expensive material suitable for high or extreme temperatures and may not be practical and / or cost-effective for use in forming the entire premixer tube 118. In some embodiments, the tube tip 156 may include a metal or metal alloy similar to that used to manufacture the retained portion of the repaired or refurbished premixer tube 118. For example, each of the tube tip 156 and the premixer tube 118 may be made of at least one of nickel, cobalt, chromium, or a tungsten-based alloy. In some embodiments, each of the tube tip 156 and the premixer tube 118 includes a cobalt-nickel-chromium-tungsten alloy, such as 188 alloy.

[0052] The tube tip 156 may include a wear resistant coating (not shown) that may provide or enhance oxidation and corrosion performance of the tube tip 156. The wear resistant coating may be applied to the tube tip 156 via electroplating, coating, or the like. In some embodiments, the wear resistant coating may be one of chromium, nickel, gel aluminide coating, aluminide coating, TBC, L605, and / or Stellite 6, but is not limited thereto. The wear resistant coating may be applied using any method and / or in any manner known to one of ordinary skill in the art, including but not limited to electron beam physical vapor deposition (EBPVD), air plasma spray (APS), high velocity oxygen fuel (HVOF), electrostatic spray assisted vapor deposition (ESAVD), and / or direct vapor deposition (DVD).

[0053] The tube tip 156 can be formed using any suitable manufacturing technique. For example, the tube tip 156 can be formed using casting, molding, cold forming (e.g., cold rolling), extrusion machining, powder metal manufacturing, additive manufacturing or 3D printing and / or computer machining (e.g., computer numerical control machining). In a specific embodiment, the tube tip 156 can be additively manufactured as a single component. As used herein, the term "additively manufactured" or "additive manufacturing method" corresponds to, but is not limited to, various known 3D printing manufacturing methods, injection extrusion deposition, wire, granular material bonding, powder bed and inkjet head 3D printing, lamination, and photopolymerization. Various technologies related to various 3D printing methods include, but are not limited to (unless stated in the claims) fused deposition modeling (FDM), electron beam freeform fabrication (EBF), direct metal laser sintering (DMLS), electron beam melting (EBM), selective laser melting (SLM), selective heat sintering (SHS), selective laser sintering (SLS), plaster-based 3D printing (PP), laminated object manufacturing (LOM), stereolithography (SLA) and digital light processing (DLP).

[0054] Figure 7 FIG. 2 is an enlarged cross-sectional side view of an exemplary tube tip 200 fixedly coupled to a retaining portion 202 of a premixer tube 118. The tube tip may be used as Figure 4 and Figure 5One or more of the tube tips 156 shown are joined. The remaining portion 202 is the portion of the premixer tube 118 that remains within the combustor 20 after the damaged outlet portion 144 has been at least partially removed to begin repair or refurbishment of the premixer tube 118. For ease of description, the remaining portion 202 of the premixer tube 202 may also be referred to as the premixer tube 118. The premixer tube 202 includes an exposed end portion 204 to which the tube tip 200 is securely fixed or coupled. The end portion 204 extends substantially axially from the middle portion 142 to an open end 206 of the premixer tube 202. The tube passage 152 of the premixer tube 202 extends between the inlet 148 and the open end 206 of the exposed end portion 204. In other words, the premixer tube 202 extends substantially axially between the inlet portion 140, the middle portion 142, and the exposed end portion 204.

[0055] like Figure 7 As shown, the premixer tube 202 includes an inner surface 158 and an opposing outer surface 160 that define an inner diameter D1 of the tube passage 152. Before the outlet portion 144 is damaged and / or removed, the inner diameter D1 can be substantially constant along the axial length of the premixer tube 118, i.e., between the inlet 148 and the outlet 150. In the premixer tube 202, the exposed end portion 204 defines a radially extending repair end face 208 that is adjacent to the open end 206 and opposite to the radially extending end face 162 adjacent to the inlet 148. The end face 208 extends radially inward from the outer surface 160 and extends from the inner surface 158 at an angled surface 210 that tapers inwardly toward the inner surface 158. The angled surface 210 is oriented at an oblique angle α1 relative to the inner surface 158 so that the inner diameter D1 of the tube passage 152 increases to an inner diameter D2 at the open end 206. The angle α1 can be any suitable angle of inclination that enables the inner diameter D1 at the inner surface 158 to increase to the inner diameter D2 at the open end 206. For example, in one embodiment, the angle α1 can be between about 5° to about 60°, about 5° to about 30°, about 5° to about 20°, about 5° to about 10°, about 10° to about 30°, about 10° to about 20°, about 20° to about 60°, about 20° to about 45°, about 20° to about 30°, about 30° to about 60°, about 30° to about 45°, or about 45° to about 60°. The outer surface 160 defines an outer diameter D3 at the open end 206. The diameter D3 can be substantially constant over the axial length of the premixer tube 202, or the diameter D3 can vary along the axial length of the premixer tube 202.

[0056] The angled surface 210 can be formed by machining the inner surface 158 of the premixer tube 202 at the open end 206. Suitable techniques for machining the inner surface 158 to form the angled surface 210 include, for example, electrical discharge machining (EDM), milling, hand grinding, and / or any other suitable machining technique. The inner surface 158 can be machined to form the angled surface 210 during and / or after removing the damaged outlet portion 144 to form the exposed end portion 204.

[0057] The tube tip 200 includes a mating end 212 and an opposing outlet end 214. The tube tip 200 is open at both ends 212 and 214 and defines a tube tip passage 216 extending therebetween. Similar to the removed outlet portion 144 of the premixer tube 202, when the fuel injector 100 is assembled with the tube tip 200 fixedly coupled or fixed to the premixer tube 118, the tube tip 200 can be directed from the intermediate portion 142 toward the combustion chamber 50 ( Figure 2 ) extends. In an exemplary embodiment, the mating end 212 of the tube tip 200 defines a socket 218 that is sized and shaped to receive the exposed end portion 204 of the corresponding premixing tube 202. For example, the socket 218 defines an inner diameter D4 that is approximately equal to or slightly wider than the outer diameter D3 so that the end portion 204 of the premixing tube 202 can be received in the socket 218. The socket 218 extends axially through the end portion 204 relative to an axial centerline 220 of the premixing tube 202 and / or the tube tip 200. When the end portion 204 of the premixing tube 202 is received by the socket 218, the tube passage 152 is axially aligned with the tube tip passage 216 along the axial centerline 220. The inlet 140 of the premixing tube 202 is configured to be in fluid communication with the open outlet end 214 of the tube tip 200.

[0058] The tube tip passage 216 is defined by an inner surface 222 that extends substantially axially between the outlet end 214 and a collar 224 of the tube tip 200. An inner diameter D5 of the tube tip passage 216 extends across the inner surface 222. The inner diameter D5 of the tube tip passage 216 may be approximately equal to the diameter D1 of the tube passage 152. The collar 224 provides an angled surface 226 that extends between the inner surface 222 and a collar surface 228 and tapers inwardly from the collar surface 228 to the inner surface 222. The collar surface 228 extends radially between the angled surface 226 and the socket inner surface 230. When the end portion 204 of the premixer tube 202 is received by the socket 218, the radially extending end face 208 is located adjacent to and may abut the collar surface 228. The inner diameter D4 of the socket 218 may be approximately equal to or slightly wider than the outer diameter D3 of the tip portion 204 such that the outer surface 160 of the tip portion 204 is adjacent to and / or abuts the socket inner surface 230 when the socket 218 receives the tip portion 204 .

[0059] The angled surface 226 of the collar 228 is oriented at an angle of inclination α2 relative to the inner surface 222, which increases the inner diameter D5 of the tube tip 200 to the inner diameter D2 at the radially inward edge of the collar surface 224. The angle α2 can be any suitable angle of inclination that increases from the inner diameter D5 at the inner surface 222 of the tube tip channel 216 to the inner diameter D2. For example, the angle α2 can be between about 5° and about 60°, between about 5° and about 30°, between about 5° and about 20°, between about 5° and about 10°, between about 10° and about 30°, between about 10° and about 20°, between about 20° and about 60°, between about 20° and about 45°, between about 20° and about 30°, between about 30° and about 60°, between about 30° and about 45°, or between about 45° and about 60°. In some examples where the inner diameter D5 is approximately equal to the inner diameter D1 of the tube passage 152 , the angles α1 and α2 of the angled surfaces 210 and 226 relative to the respective inner surfaces 158 and 222 are approximately the same.

[0060] like Figure 7 As shown, when the end portion 204 of the premixer tube 202 is received by the socket 218, the angled surfaces 210 and 226 complement each other and produce a substantially mirrored taper at the junction 232 of the end face 208 and the collar surface 228. In particular, at the junction 232, the inner diameter D2 of the fixedly coupled or fixed premixer tube 202 and the tube tip 200 increases from the inner diameter D1 within the tube passage 152 and then decreases to the inner diameter D5 within the tip tube passage 216. In other words, the tapered surfaces 210 and 226 provide an increased inner diameter D2 of the fixedly coupled premixer tube 202 and the tube tip 200 at the junction 232 of the end face 208 and the collar surface 228.

[0061] Increasing the inner diameter D2 of the fixedly coupled or fixed premixer tube 202 and tube tip 200 at the joint 232 facilitates reducing or eliminating the possibility that the connection between the premixer tube 202 and the tube tip 200 will impede or restrict the flow of the combustible mixture therethrough, which may otherwise interrupt the combustion chamber 50 ( Figure 2) and / or reduce flame stability within the combustor 20. For example, techniques for securely securing the tube tip 200 to the premixer tube 202 (e.g., furnace brazing, induction brazing, orbital welding, laser welding, friction welding, electron beam welding, diffusion bonding, plasma spraying, heat resistant adhesives, adhesive coatings, high velocity oxygen fuel coating spraying, and / or any other known techniques that enable the premixer tube 202 to function as described herein) may introduce and undesirably cause filler material used to join these components to accumulate within the tube passage 152 and / or the tube tip passage 216. The accumulated material may otherwise impede or restrict flow, or otherwise create flow disturbances of the flammable mixture. However, the increased diameter D2 at the junction 232 provides additional space within the tube passage 152 and / or the tube tip passage 216 for such material to accumulate, so as to facilitate reducing or eliminating the negative effects of the accumulated material on the flow of the flammable mixture through the tube 218.

[0062] In addition, due to manufacturing tolerances, the geometry of the end portion 204 of the premixing tube 202 and the collar 224 adjacent to the end portion 204 of the tube tip 200 when received by the socket 218 may not be completely aligned, which may cause an offset in the axial alignment between the premixing tube 202 and the tube tip 200. The offset in the axial alignment between the premixing tube 202 and the tube tip 200 may otherwise hinder or restrict flow or otherwise generate flow disturbances of the combustible mixture. However, the increased diameter D2 at the joint 232 is conducive to reducing or eliminating the negative effects that the offset in the axial alignment between the premixing tube 202 and the tube tip 200 may otherwise cause to the flow of the combustible mixture passing therethrough. In this way, one or more premixing tubes 202 can be repaired or refurbished with the corresponding tube tip 200 while maintaining the performance, efficiency and / or life of the combustor 20.

[0063] Figure 8 FIG. 2 is an enlarged cross-sectional side view of another exemplary tube tip 300 fixedly coupled or secured to a retaining portion 302 of a premixing tube 118. The retaining portion 302 of the premixing tube 302 is also referred to as the premixing tube 118. The tube tip 300 includes similar features and components as the tube tip 200, and the premixing tube 302 includes the same features and components as those of the above referenced embodiments. Figure 7 Similar features and components are described for the premixer tube 202. Figure 7 and Figure 8In the embodiment, the inner surface 158 of the premixing tube 302 is machined to include a concave surface 310 extending between the end face 208 and the inner surface 158 and engaging the end face and the inner surface. Similar to the angled surface 210 of the premixing tube 202, the concave surface 310 increases the inner diameter D1 of the tube passage 152 to the inner diameter D2 at the open end 206. The concave surface 310 can be formed by machining the inner surface 158 of the premixing tube 302 at the open end 206. Suitable techniques for machining the inner surface 158 to form the concave surface 310 include, for example, electrical discharge machining (EDM), milling, manual grinding and / or any other suitable machining technology. During and / or after removing the damaged outlet portion 144 to form the exposed end portion 204, the inner surface 158 can be machined to form the concave surface 310.

[0064] The collar 224 of the tube tip 300 provides a concave surface 326 that joins the inner surface 222 and the collar surface 228. Similar to the angled surface 226 of the tube tip 300, the concave surface 326 increases the inner diameter D5 of the tube tip 200 to the inner diameter D2 at the radially inward edge of the collar surface 228. When the end portion 204 of the premixer tube 302 is received by the socket 218 of the tube tip 300, the concave surfaces 310 and 326 complement each other and produce a generally semicircular shape with a radius R1 at the junction 332 of the end surface 208 and the collar surface 228. In particular, at the junction 332, the inner diameter D2 of the fixedly coupled or fixed premixer tube 302 and the tube tip 300 increases from the inner diameter D1 within the tube passage 152 and then decreases to the inner diameter D5 within the tip tube passage 216. In other words, the concave surfaces 310 and 316 provide an increased inner diameter D2 of the fixedly coupled premixer tube 302 and tube tip 300 at the joint 332. As described above, the increased diameter D2 at the joint 332 facilitates reducing or eliminating the chance that the connection between the premixer tube 302 and the tube tip 300 will impede or restrict the flow of the combustible mixture therethrough, and enables repair or refurbishment of one or more premixer tubes 302 with the corresponding tube tip 300 while maintaining the combustor 20 ( Figure 2 )’s performance, efficiency and / or life.

[0065] Fig. 9 FIG. 4 is an enlarged cross-sectional side view of another exemplary tube tip 400 that is securely secured or coupled to a retaining portion 402 of a premixing tube 118. The retaining portion 402 of the premixing tube 402 is also referred to as the premixing tube 118. The tube tip 400 includes similar features and components as the tube tip 200, and the premixing tube 402 includes the same features and components as those of the above referenced embodiments. Figure 7 Similar features and components are described for the premixer tube 202. Figure 7 and Fig. 9In the embodiment, the inner surface 158 of the premixing tube 402 is machined to include an angled surface 410, which extends between the inner surface 158 and a second inner surface 434 of the radially extending end face 408 adjacent to the open end 206 and engages the inner surface and the second inner surface. The second inner surface 434 is substantially flat. Similar to the angled surface 210 of the premixing tube 202, the angled surface 410 provides an increased inner diameter D2 at the open end 206. The angled surface 410 and the second inner surface 434 can be formed by machining the inner surface 158 of the premixing tube 402 at the open end 206. Suitable techniques for machining the inner surface 158 to form the angled surface 410 and the second inner surface 434 include, for example, electrical discharge machining (EDM), milling, manual grinding and / or any other suitable machining technology. During and / or after removing the damaged outlet portion 144 to form the exposed tip portion 204 , the inner surface 158 may be machined to form the angled surface 410 and the second inner surface 434 .

[0066] The collar 224 of the tube tip 400 provides an angled surface 426 that joins the inner surface 222 and a second inner surface 436 adjacent to the radially extending collar surface 428. The second inner surface 436 is substantially flat. Similar to the angled surface 226 of the tube tip 200, the angled surface 426 provides an increased inner diameter D2 at the radially inward edge of the collar surface 428.

[0067] When the end portion 204 of the premixer tube 402 is received by the socket 218 of the tube tip 400, the angled surfaces 410 and 426 and the corresponding second inner surfaces 434 and 436 complement each other and produce a substantially mirrored taper at the junction 432 of the end surface 408 and the collar surface 428. In particular, at the junction 432, the inner diameter D2 of the fixedly coupled premixer tube 402 and the tube tip 400 increases from the inner diameter D1 and then decreases to the inner diameter D5. In other words, the angled surfaces 410 and 426 provide an increased inner diameter D2 of the fixedly coupled premixer tube 402 and the tube tip 400 at the junction 432. As described above, the increased diameter at the junction 432 facilitates reducing or eliminating the chance that the connection between the premixer tube 402 and the tube tip 400 impedes or restricts the flow of the combustible mixture therethrough, and enables the repair or refurbishment of one or more premixer tubes 402 with the corresponding tube tip 400 while maintaining the combustor 20 ( Figure 2 )’s performance, efficiency and / or life.

[0068] Fig.10 for Fig. 9 An enlarged view of the segment C1 indicated by the dashed line in FIG. Fig.10The junction 432 is depicted in greater detail, as well as corresponding features of the end face 408 of the premixer tube 402 and the collar surface 428 of the tube tip 400. The angled surface 410 of the premixer tube 402 is oriented at an angle of inclination α3 relative to the inner surface 158, and the angled surface 426 of the tube tip 400 is oriented at an angle of inclination α4 relative to the inner surface 222. Angles α3 and α4 may be any suitable angles of inclination that increase from the inner diameter D1 at the inner surface 158 and from the inner diameter D5 at the inner surface 222 to the inner diameter D2 at the junction 432, respectively. For example, the angles α3 and α4 may each be between about 5° and about 60°, about 5° and about 30°, about 5° and about 20°, about 5° and about 10°, about 10° and about 30°, about 10° and about 20°, about 20° and about 60°, about 20° and about 45°, about 20° and about 30°, about 30° and about 60°, about 30° and about 45°, or about 45° and about 60°. In some examples where the inner diameter D5 is approximately equal to the inner diameter D1 of the tube passage 152, the angles α3 and α4 of the angled surfaces 410 and 426 relative to the respective inner surfaces 158 and 222 are approximately the same.

[0069] like Fig.10 As shown, the end face 408 and the collar surface 428 include corresponding centering features to facilitate centering the end portion 204 of the premixer tube 402 within the socket 218. Fig. 9 and Fig.10 The centering features described in the embodiments of the present invention may be included in any embodiment, such as in reference Figure 7 and Figure 8 In the described embodiment. The centering feature of the premixer tube 402 is formed in the end face 408 and includes a substantially flat stepped surface 438 extending radially from the surface 438 and a bevel 440 joining the outer surface 160 and the stepped surface 434. The stepped surface 438 can be appropriately formed when the damaged end portion 144 is removed from the premixer tube 118. The bevel 440 can be formed by machining the outer surface 160 of the premixer tube 402 at the open end 206. Suitable techniques for machining the outer surface 160 to form the bevel 440 include, for example, electrical discharge machining (EDM), milling, hand grinding, and / or any other suitable machining technique. During and / or after removing the damaged outlet portion 144 to form the exposed end portion 204, the outer surface 160 can be machined to form the bevel 440.

[0070] A corresponding centering feature of the tube tip 400 is formed in the collar surface 428 and includes a substantially flat step surface 442 extending radially from the surface 442 and a chamfer 444 engaging the hub inner surface 230 and the step surface 436. The chamfers 440 and 444 suitably extend between the respective surfaces at approximately the same angle relative to the outer surface 160 and the hub inner surface 230. For example, the chamfers 440 may each extend at approximately the same angle in the range of about 20° to about 75°, about 20° to about 45°, about 20° to about 30°, about 30° to about 75°, about 30° to about 60°, about 30° to about 45°, about 45° to about 75°, about 45° to about 60°, or about 60° to about 75°.

[0071] As described above, when the socket 218 receives the tip portion 204, the inner diameter D4 of the socket 218 and the outer diameter D3 of the tip portion 204 can cause the outer surface 160 of the tip portion 204 to be adjacent to and / or abut the socket inner surface 230. The centering features formed in the end surface 408 and the collar surface 428 facilitate aligning the tip portion 204 within the socket 218 at the junction 432. In particular, when the socket 218 receives the tip portion 204, the step surfaces 438 and 442 are adjacent to and / or abut each other, and the chamfers 440 and 444 are adjacent to and / or abut each other to facilitate radial and axial alignment of the tip portion 204 within the socket 218. In this manner, the tip portion 204 of the premixer tube 402 can be centered within the socket 218, and the tube passage 152 and the tip tube passage 216 can be substantially axially aligned along the axial centerline 220.

[0072] Fig.11 FIG. 5 is an enlarged cross-sectional side view of another exemplary tube tip 500 that is securely secured or coupled to a retaining portion 502 of a premixing tube 118. The retaining portion 502 of the premixing tube 502 is also referred to as the premixing tube 118. The tube tip 500 includes similar features and components as the tube tip 200, and the premixing tube 502 includes the same features and components as those of the above referenced embodiments. Figure 7 Similar features and components are described for the premixer tube 202. Figure 7 and Fig.11 2 and 3. Corresponding reference numerals are used to indicate corresponding components. In this embodiment, the open mating end 512 of the tube tip 500 does not include the socket 218. Instead, the mating end 512 defines a radially extending end face 528 that is complementary to and abuts the end face 208 of the premixing tube 502. The coupling sleeve 506 circumferentially surrounds the junction 532 of the end faces 208 and 528. The coupling sleeve 506 can be fixedly coupled or fixed to the premixing tube 502 and / or the tube tip 500 at the junction 532 via brazing, welding, adhesive plating, or by any means and / or method suitable for joining the two components.

[0073] like Fig.11 As shown, the end face 528 of the mating end 512 is connected to the inner surface 222 of the tube tip 500 by the angled surface 226, which is oriented at an angle α2 relative to the inner surface 222 as described above. The angled surface 226 provides an increased inner diameter D2 at the end face 528 of the mating end 212. The angled surfaces 210 and 226 are complementary to each other and form a substantially mirrored taper at the junction 532 of the end faces 208 and 528. In particular, at the junction 532, the inner diameter D2 of the fixedly coupled premixer tube 502 and the tube tip 500 increases from the inner diameter D1 and then decreases to the inner diameter D5. In other words, the angled surfaces 210 and 226 provide for increasing the inner diameter of the fixedly coupled premixer tube 502 and the tube tip 500 at the junction 532. As described above, the increased diameter at the joint 532 facilitates reducing or eliminating the chance that the connection between the premixer tube 502 and the tube tip 500 will impede or restrict the flow of the combustible mixture therethrough, and enables repair or refurbishment of one or more premixer tubes 502 with the corresponding tube tip 500 while maintaining the combustor 20 ( Figure 2 )’s performance, efficiency and / or life.

[0074] The tube tip 156 that may be incorporated into the fuel injector 100 for repairing and / or refurbishing the premixer tube 118 may include any or each of the features illustrated and described herein as the exemplary embodiments of the tube tips 200, 300, 400, and 500. In addition, the tube tip 156 may include various other tube tip shapes or configurations, and the tube tip 156 should not be limited to the exemplary embodiments described herein. In addition, the exemplary features described herein for the tube tip 156 and corresponding end portion 204 of the premixer tube 118 (e.g., for the tube tips 200, 300, 400, and 500 and the corresponding premixer tubes 202, 302, 402, and 502) are applicable to any of the embodiments described herein and any of the various other shapes or configurations of the tube tip 156 and corresponding end portion 204 of the premixer tube 118 that are not shown. The exemplary embodiments are not limiting with respect to shapes, geometries, or other configurations that may be suitably incorporated into the tube tip 156 and corresponding end portion 204 to replace the damaged exit portion 144 of the premixer tube 118 with the tube tip 156 and facilitate the advantages described herein.

[0075] Fig.12 An exemplary method 600 is provided for repairing a fuel injector (eg, fuel injector 100) including a plurality of premixer tubes (eg, premixer tubes 118). Figures 3 to 11The method 600 is described with reference to the components shown in FIG. The premixer tubes 118 extend substantially parallel to each other along or parallel to the axial centerline 106 of the fuel injector 100. Each premixer tube 118 includes an inlet portion 140 extending through the fuel plenum 120, a middle portion 142 extending axially outward from the fuel plenum, and an outlet portion 144 extending axially outward from the middle portion 142 toward the combustion chamber 50 ( Figure 2 In operation of the fuel injector 100, the outlet portions 144 of the premixer tubes 118 are exposed to extreme temperatures and high mechanical loads due to their proximity to the combustion chamber 50 and / or the combustion flame, and may fail over time due to, for example, thermal stress and oxidation.

[0076] The method 600 includes removing 602 the outlet portion 144 from at least one premixer tube 118 to define an exposed end portion 204. Removing 602 the outlet portion 144 may be performed using any suitable means for cutting or otherwise removing tubing. For example, removing 602 the outlet portion 144 may be performed using scoring, electrical discharge machining (EDM), torch cutting, a cutting blade, etc. Additionally, removing 602 the outlet portion 144 may include removing 602 the entire outlet portion 144 of the premixer tube 118 or only removing a portion of the outlet portion 144. For example, only a damaged area of ​​the outlet portion 144 may be removed 602. In some implementations of the method 600, the outlet portion 144 of each of the premixer tubes 118 of the fuel injector 100 may be removed 602 in a single cutting operation, wherein the outlet portion 144 of the premixer tube 118 is removed along the cutting line 166 ( Figure 5 ) is removed, the cut line extending generally perpendicular to the axial length of the premixer tube 118 and the axial centerline 106 of the fuel injector 100. In such implementations, after removal 602, the exposed end portions 204 defined in the premixer tubes 118 are substantially coextensive and have end surfaces 208 that are generally flush with one another. In other implementations, the outlet portions 144 of one or some of the premixer tubes 118 are each removed, while the outlet portions 144 of other premixer tubes 118 are not removed. In some implementations of the method 600, removing 602 the outlet portions 144 may be performed without having to remove a support plate or other fixture from the fuel injector 100. For example, the intermediate portion 142 and the outlet portion 144 of the premixer tube 118 may float or may freely extend outward from the fuel plenum 120 without any additional support plates or fixtures disposed downstream of the shroud 112, thereby eliminating the need to remove such fixtures prior to removing 602 the outlet portions 144.

[0077] The method 600 also includes machining 604 the inner surface 158 of at least one premixer tube 118 at the exposed end portion 204 to an increased inner diameter D2 relative to the inner diameter D1 of the premixer tube 118 upstream of the exposed end portion 204. The machining 604 can be performed using any suitable machining technique, such as, for example, electrical discharge machining (EDM), milling, hand grinding, etc. The machining 604 can produce any suitable geometry of the end portion 204 that defines the increased inner diameter D2 at the exposed end portion 204. In some implementations of the method 600, the machining 604 can produce an inwardly tapered machined surface (e.g., Figure 7 and Fig.11 The angled surface 210 shown, Figure 8 The concave surface 310 or Fig. 9 and Fig.10 The machined surface defines an increased inner diameter D2 at the exposed end portion 204. For example, the exposed end portion 204 may include the angled surface 210 ( Figure 7 and Fig.11 ), the angled surface extending obliquely between the end surface 208 and the inner surface 158 and tapering inwardly toward the inner surface 158. The exposed end portion 204 may alternatively include a concave surface 310 ( Figure 8 ), the concave surface extending between and joining the end face 208 and the inner surface 158. The exposed end portion 204 may alternatively include an angled surface 410 ( Fig. 9 and Fig.10 ), the angled surface extending obliquely between the inner surface 158 and the second inner surface 434 adjacent to the end surface 408. During machining 604, a support plate may be temporarily mounted to at least one premixer tube 118 and at least one other premixer tube 118. For example, in a specific implementation of the method 600 in which the intermediate portion 142 and the outlet portion 144 of the premixer tube 118 freely float or extend outward from the fuel plenum 120 without any additional support plates or fixtures disposed downstream of the shroud 112, a support plate may be temporarily mounted to the premixer tube 118 being machined 604 along with at least one other premixer tube 118 (e.g., at least one adjacent premixer tube 118) to facilitate limiting movement of the at least one premixer tube 118 during machining 604.

[0078] The method 600 also includes securely coupling 606 the tube tip 156 to the exposed end portion 204. Coupling 606 the tube tip 156 to the exposed end portion 204 may be performed by inserting the exposed end portion 204 into the socket 218 of the tube tip 156 and coupling the outer surface 160 of the exposed end portion 204 to the inner surface 230 of the socket 218. Coupling the tube tip 156 to the exposed end portion 204 may alternatively be performed by surrounding the joint between the tube tip 156 and the exposed end portion 204 with a coupling sleeve 506 and securely coupling or securing the coupling sleeve 506 to the tube tip 156 and / or the exposed end portion 204. The tube tip 156 may be securely coupled 606 to the exposed end portion 204 using any suitable means for coupling tubing. For example, the tube tip 156 may be coupled 606 to the exposed end portion 204 by furnace brazing, induction brazing, orbital welding, laser welding, friction welding, electron beam welding, diffusion bonding, plasma spraying, heat resistant adhesives, adhesive coatings, high velocity oxygen fuel coating spraying, etc. In some implementations, the coupling 606 may include molten filler material (e.g., a brazing filler material or a welding filler material) to securely couple the tube tip 156 to the exposed end portion 204. The molten filler material may accumulate along the machined surface of the exposed end portion 204 defining the increased inner diameter D2, thereby facilitating the reduction or elimination of the risk of the accumulated material obstructing or restricting the flow of the flammable mixture therethrough while maintaining the burner 20 ( Figure 2 )’s performance, efficiency and / or life.

[0079] After coupling 606 the tube tips 156 to the exposed end portions 204, the premixer tubes 118 including the tube tips 156 suitably extend the same axial length as before the damaged outlet portions 144 were removed 602. In implementations of the method 600 in which the premixer tubes 118 are coextensive with one another and their outlet portions 144 are removed 602 along the cut line 166 in a single cutting operation, the tube tips 156 coupled 606 to the exposed end portions 204 suitably maintain a degree of coextensivity such that the tube tips 156 define end surfaces that are substantially flush with one another at the outlet end 214. In implementations of the method 600 in which the outlet portions 144 of one or some of the premixer tubes 118 are each removed 602, the tube tips 156 that replace the removed outlet portions 214 may be coextensive with the remaining outlet portions 144 and define end surfaces at the outlet end 144 that are substantially flush with the remaining end surfaces 164.

[0080] Coupling 606 tube tip 156 to exposed end portion 204 forms a bond between tube tip 156 and exposed end portion 204 (eg, Figure 7 The joint 232, Figure 8 The joint 332, Fig. 9 and Fig.10 The joint 432 or Fig.11 532 in the junction). The inner diameter D2 of the tube tip 156 at the junction is greater than the inner diameter downstream of the junction. That is, the tube tip 156 includes an inner surface 222 that defines a tube tip channel 216 having an inner diameter D5, and the inner diameter D2 of the tube tip 156 at the junction is greater than the inner diameter D5. In the exemplary method, the tube tip 156 and the exposed end portion 204 have approximately equal inner diameters D2 at the junction. In some specific implementations of method 600, the tube tip 156 has an inner surface configuration at the junction that is complementary to the inner surface configuration of the exposed end portion 204. The tube tip may have an inwardly tapered surface (e.g., Figure 7 and Fig.11 The angled surface 226 shown, Figure 8 The concave surface 326 or Fig. 9 and Fig.10 The inwardly tapered surface 426 (shown) extends between the junction and the inner surface 222 of the tube tip 156 to define a larger inner diameter of the tube tip 156 at the junction and is complementary to the inwardly tapered machined surface of the exposed end portion 204 produced by machining 604. For example, the tube tip 156 may include the angled surface 226 ( Figure 7 and Fig.11 ), the angled surface is located between the inner surface 222 and the radially extending surface (e.g., Figure 7 The collar surface 228 or Fig.11 The tube tip 156 may extend obliquely between the end surface 528 in the inner surface 222 and taper inwardly toward the inner surface 222. The tube tip 156 may alternatively include a radially extending surface (e.g., Figure 8 The collar surface 228 or Fig.11 The concave surface 326 ( Figure 8 The tube tip 156 may alternatively include an angled surface 426 ( Fig. 9 and Fig.10 ), which angled surface extends obliquely between the inner surface 222 and a second inner surface 436 adjacent to the radially extending surface 442. In some implementations, the inner surface configurations of the tube tip 156 and the exposed end portion 204 are mirror images and increase the inner diameter from D1 in the tube channel 152 and D5 in the tube tip channel 216 (which can be approximately the same) to approximately the same inner diameter D2 at the junction.

[0081] In some implementations of method 600, exposed end portion 204 and tube tip 156 may be provided with corresponding centering features to facilitate radial and / or axial alignment of exposed end portion 204 and tube tip 156. Centering features may be formed in exposed end portion 204 during machining 604. For example, in implementations of method 600 where exposed end portion 204 is inserted into socket 218 of tube tip 156 during coupling 606, machining 604 may include machining 604 chamfer 440 ( Fig.10 ), the chamfer extending between and engaging the outer surface 160 of the exposed end portion 204 and the radially extending stepped surface 438. The corresponding centering feature of the tube tip 156 may include a chamfer 444 extending between and engaging the socket inner surface 230 and the stepped surface 442. When the socket 218 receives the end portion 204 during the coupling 606, the stepped surfaces 438 and 442 are adjacent and / or abutting each other, and the chamfers 440 and 444 are adjacent and / or abutting each other to facilitate radial and axial alignment of the end portion 204 within the socket 218.

[0082] Exemplary methods described herein include machining the exposed end portion of the premixing tube after removing the damaged outlet portion, to produce a suitable configuration of the premixing tube, which is helpful to reduce or eliminate the possibility and risk that the connection between the premixing tube and the tube tip hinders or limits the flammable mixture to flow through it. For example, the premixing tube can be machined into an increased diameter at the exposed end portion attached to the tube tip, and the increased diameter provides additional internal space for material accumulation without causing obstacles to the flammable mixture flowing through the premixing tube and the tube tip. The increased diameter is also conducive to reducing or eliminating the negative effects that the axial alignment offset between the premixing tube and the tube tip may otherwise cause to the flow of the flammable mixture through it. In this way, one or more premixing tubes can be repaired or renovated with corresponding tube tips while maintaining the performance, efficiency and / or life of the burner.

[0083] Other aspects of the disclosure are provided by the subject matter of the following clauses:

[0084] Item 1. A method for repairing a fuel injector comprising a plurality of premixer tubes, each of which extends from a fuel filling chamber to an outlet portion, the method comprising: removing the outlet portion from at least one premixer tube to define an exposed end portion; machining an inner surface of the at least one premixer tube at the exposed end portion to form an increased inner diameter relative to an inner diameter of the premixer tube upstream of the exposed end portion; and connecting a tube tip to the exposed end portion.

[0085] Clause 2. The method of clause 1, wherein coupling the tube tip to the exposed end portion forms a joint between the tube tip and the exposed end portion, wherein the tube tip has a larger inner diameter at the joint than downstream of the joint.

[0086] Clause 3. The method of Clause 2, wherein the increased inner diameter at the exposed end portion is approximately equal to the inner diameter of the tube tip at the junction.

[0087] Clause 4. A method according to any of the preceding clauses, wherein coupling the tube tip to the exposed end portion comprises melting filler material to securely couple the tube tip to the exposed end portion, wherein the molten filler material accumulates at the increased inner diameter along the inner surface of the joint.

[0088] Clause 5. The method of Clause 4, wherein coupling the tube tip to the exposed end portion comprises one of brazing and welding the tube tip to the exposed end portion using the filler material.

[0089] Clause 6. The method of any preceding clause, wherein machining the inner surface to the increased inner diameter comprises at least one of electrical discharge machining and milling.

[0090] Clause 7. The method of any preceding clause, wherein coupling the tube tip to the exposed end portion comprises inserting the exposed end portion into a socket of the tube tip and coupling an outer surface of the exposed end portion to an inner surface of the socket.

[0091] Clause 8. A method according to any of the preceding clauses, wherein connecting the tube tip to the exposed end portion forms a joint between the tube tip and the exposed end portion, and also includes surrounding the joint with a coupling sleeve and securely fixing the coupling sleeve to at least one of the tube tip and the exposed end portion, thereby securely connecting the tube tip to the exposed end portion.

[0092] Clause 9. The method of any preceding clause, further comprising temporarily mounting a support plate to the at least one premixer tube and at least one other premixer tube to facilitate limiting movement of the at least one premixer tube during the machining.

[0093] Item 10. A method for repairing a fuel injector having a plurality of premixer tubes, each premixer tube extending downstream from a fuel filling chamber to an outlet portion, the method comprising: removing the outlet portion from the premixer tube to define an exposed end portion; machining the inner surface of the premixer tube at the exposed end portion to produce an inwardly tapered machined surface, the inner diameter of the machined surface at the exposed end portion being greater than the inner diameter upstream of the exposed end portion; and connecting the tube tip to the exposed end portion to form a joint between the tube tip and the exposed end portion, wherein the tube tip has an inwardly tapered surface extending between the joint and the inner surface of the tube tip, and wherein the inwardly tapered surface of the tube tip is complementary to the inwardly tapered machined surface to define a larger inner diameter at the joint.

[0094] Item 11. A method according to Item 10, wherein the inwardly tapered machined surface includes a first angled surface oriented at a first inclination angle relative to the inner surface of the premixer tube, and the inwardly tapered surface of the tube tip includes a second angled surface oriented at a second inclination angle relative to the inner surface of the tube tip.

[0095] Item 12. A method according to Item 11, wherein the inner surface of the premixing tube and the inner surface of the tube tip define approximately the same diameter, and the inner diameter at the exposed end portion defined by the inwardly tapered machined surface is approximately the same as the inner diameter of the tube tip at the junction defined by the inwardly tapered surface.

[0096] Clause 13. The method of clause 10, wherein the inwardly tapered machined surface comprises a first concave surface, the inwardly tapered surface of the tube tip comprises a second concave surface, and the first and second concave surfaces are complementary to each other and form a generally semicircular shape at the junction.

[0097] Clause 14. A method according to any one of clauses 10 to 13, wherein the machining also includes machining the exposed end portion to produce a centering feature, which is complementary to a corresponding centering feature formed in the tube tip and facilitates alignment of the exposed end portion and the tube tip at the joint.

[0098] Item 15. A method according to Item 14, wherein coupling the tube tip to the exposed end portion includes inserting the exposed end portion into a socket of the tube tip, and wherein the centering feature machined into the exposed end portion includes a first bevel that abuts a second bevel formed in the socket of the tube tip at the joint and facilitates alignment of the exposed end portion within the socket.

[0099] Item 16. A method for repairing a fuel injector comprising a plurality of premixer tubes, each of which extends from a fuel filling chamber to an outlet portion, the method comprising: removing the outlet portion from the plurality of premixer tubes along a cutting line to define exposed end portions of the plurality of premixer tubes; machining the inner surface of each premixer tube at the exposed end portion to form an increased inner diameter relative to the inner diameter of the premixer tube upstream of the exposed end portion; and connecting a tube tip to each exposed end portion.

[0100] Clause 17. The method of Clause 16, wherein removing the outlet portions from the plurality of premixer tubes defines the exposed end portions that are coextensive and have end surfaces that are substantially flush with one another.

[0101] Clause 18. The method of Clause 17, wherein the tube tips coupled to the exposed end portions are coextensive and have end surfaces that are substantially flush with each other.

[0102] Clause 19. The method of any one of clauses 16 to 18, wherein the plurality of premixer tubes extend freely from the fuel plenum such that removing the outlet portion from the plurality of premixer tubes is performed without removing a support plate from the fuel injector.

[0103] Clause 20. The method of any one of clauses 16 to 19, wherein removing the outlet portions from the plurality of premixer tubes is performed using a single cutting operation.

[0104] The methods and systems described herein are not limited to the specific embodiments described herein. For example, the components of each system and / or the steps of each method may be used independently and separately from other components and / or steps described herein. For example, the methods and systems may also be used in conjunction with other turbine systems and are not limited to practice with only gas turbine engines as described herein. Instead, the exemplary embodiments may be implemented and used in conjunction with many other turbine applications.

[0105] Although specific features of various embodiments of the present disclosure may be shown in some drawings and not in other drawings, this is for convenience only. According to the principles of the present disclosure, any feature of a drawing may be referenced and / or claimed in combination with any feature of any other drawing.

[0106] 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 device or system and performing any combined method. 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 have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A method of repairing a fuel injector (100) comprising a plurality of premixing tubes (118), each of the premixing tubes extending from a fuel plenum (120) to an outlet portion (144), the method comprising: removing the outlet portion (144) from at least one premixer tube (118) to define an exposed end portion (204); machining an inner surface (158) of the at least one premixer tube (118) at the exposed end portion (204) to form an increased inner diameter (D2) relative to an inner diameter (D1) of the premixer tube upstream of the exposed end portion; and A tube tip (156) is coupled to the exposed end portion (204).

2. The method of claim 1 , wherein coupling the tube tip (156) to the exposed end portion (204) forms a joint (232) between the tube tip and the exposed end portion, wherein the tube tip has a larger inner diameter (D2) at the joint than downstream of the joint.

3. The method of claim 2, wherein the increased inner diameter (D2) at the exposed end portion (204) is approximately equal to the inner diameter (D2) of the tube tip (156) at the junction (232).

4. A method according to any of the preceding claims, wherein coupling the tube tip (156) to the exposed end portion (204) includes melting a filler material to securely couple the tube tip to the exposed end portion, wherein the molten filler material accumulates at the increased inner diameter (D2) along the inner surface (210, 226) of the joint (232), preferably wherein coupling the tube tip to the exposed end portion includes one of brazing and welding the tube tip to the exposed end portion using the filler material.

5. The method of any of the preceding claims, wherein machining the inner surface (158) to the increased inner diameter (D2) comprises at least one of electrical discharge machining and milling.

6. A method according to any of the preceding claims, wherein coupling the tube tip (156) to the exposed end portion (204) includes inserting the exposed end portion into a socket (218) of the tube tip and coupling an outer surface (160) of the exposed end portion to an inner surface (230) of the socket.

7. The method according to any one of claims 1 to 5, wherein coupling the tube tip (156) to the exposed end portion (204) forms a joint (232) between the tube tip and the exposed end portion, and further comprises surrounding the joint with a coupling sleeve (506) and securely fixing the coupling sleeve to at least one of the tube tip and the exposed end portion, thereby securely coupling the tube tip to the exposed end portion.

8. The method according to any of the preceding claims, further comprising temporarily mounting a support plate to the at least one premixer tube (118) and at least one other premixer tube (118) to facilitate limiting movement of the at least one premixer tube during the machining.

9. A method according to any one of the preceding claims, wherein: machining the inner surface (158) of the premixer tube (118) at the exposed end portion (204) to produce an inwardly tapered machined surface (210) having the increased inner diameter (D2); as well as The tube tip (156) is coupled to the exposed end portion (204) to form a joint (232) between the tube tip and the exposed end portion, wherein the tube tip has an inwardly tapered surface (226) extending between the joint and an inner surface (222) of the tube tip, and the inwardly tapered surface of the tube tip is complementary to the inwardly tapered machined surface to define an increased inner diameter (D2) at the joint.

10. The method of claim 9, wherein the inwardly tapered machined surface comprises a first angled surface (210) oriented at a first inclination angle (α1) relative to the inner surface (158) of the premixer tube (118), and the inwardly tapered surface (226) of the tube tip (156) comprises a second angled surface (222) oriented at a second inclination angle (α2) relative to the inner surface (222) of the tube tip.

11. The method of claim 9, wherein the inwardly tapered machined surface comprises a first concave surface (310), the inwardly tapered surface of the tube tip comprises a second concave surface (326), and the first concave surface and the second concave surface are complementary to each other and form a generally semicircular shape at the joint (332).

12. A method according to any of the preceding claims, wherein the machining further comprises machining the exposed end portion (204) to produce a centering feature (438, 440) that is complementary to a corresponding centering feature (442, 440) formed in the tube tip (156) and facilitates alignment of the exposed end portion and the tube tip at the joint.

13. The method of claim 12, wherein coupling the tube tip (156) to the exposed end portion (204) comprises inserting the exposed end portion into a socket (218) of the tube tip, and wherein the centering feature machined into the exposed end portion comprises a first bevel (440) abutting a second bevel (444) formed in the socket of the tube tip at the joint (232) and facilitating alignment of the exposed end portion within the socket.

14. A method according to any one of the preceding claims, comprising: removing the outlet portion (144) from each of the plurality of premixer tubes (118) along a cut line (166) to define exposed end portions (204) of the plurality of premixer tubes; machining the inner surface (158) of each premixer tube at the exposed end portion to form the increased inner diameter (D2); and A tube tip (156) is coupled to each exposed end portion.

15. The method of claim 14, wherein the plurality of premixer tubes (118) extend freely from the fuel plenum (120) such that removing the outlet portion (144) from the plurality of premixer tubes is performed without removing a support plate from the fuel injector, and preferably wherein removing the outlet portion (144) from the plurality of premixer tubes is performed using a single cutting operation.

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