Raw air conditioning system

Abstract

exhibiting system features: a multi-tube fuel nozzle (12), comprising: several mixing tubes (26), each mixing tube (26) having: an annular wall (108) arranged around a central passage (110) of the mixing tube (26), wherein the central passage (110) of the mixing tube (26) extends from an upstream end (94) to a downstream end (96) of the annular wall (108) with respect to a flow direction through the central passage (110) of the mixing tube (26); and an air inlet area arranged around a fuel injector (24) extending into the central passage (110) of the mixing tube (26), wherein the air inlet area has an air inlet area of ​​the annular wall (108) having a bell-shaped section; wherein, starting at the upstream end (94) of the annular wall (108), an outer diameter (126) of each mixing tube (26) first increases before the bell-shaped section and then decreases continuously through the bell-shaped section in the flow direction through the central passage (110) of the mixing tube (26) to the downstream end (96), and an inner diameter (128) of each mixing tube (26) first decreases from the upstream end (94) before the bell-shaped section and then remains constant in the flow direction through the central passage (110) of the mixing tube (26) to the downstream end (96) of the annular wall (108); wherein the cross-sectional area (144, 146, 148) of the annular wall (108) of each mixing tube (26) initially increases starting at the upstream end (94) and axially in the downstream direction towards the downstream end (96), then gradually decreases until it remains constant in a downstream section of the annular wall (108) of the mixing tube (26), the decrease in cross-sectional area (146) defining the bell-shaped section of the air inlet area of ​​the annular wall (108).

Description

BACKGROUND OF THE INVENTION

[0001] The subject matter of the invention described herein relates to raw level airflow conditioning for turbine systems.

[0002] Gas turbine systems generally include one or more combustors that combust a mixture of compressed air and fuel to produce hot combustion gases. Unfortunately, existing combustors may receive fuel and air at pressures and / or flow rates that can fluctuate due to various limitations of the combustors, fuel nozzles, and associated equipment. These fluctuations in air and fuel can promote or cause fluctuations in the fuel / air ratio, thereby increasing the possibility of flame holding, backfire, and / or increased emissions (e.g., of nitrogen oxides). Conventional systems may also be slower in achieving mixing, thereby reducing overall system efficiency. Therefore, there is a need for a system that can achieve faster and more uniform fuel / air mixing that is also consistent and easily maintained.

[0003] EP 2 436 983 A1 discloses a system with a multi-tube fuel nozzle having a plurality of mixing tubes, each having an annular wall arranged around a central passage and an air inlet region arranged around a fuel injector extending into the central passage of the mixing tube. The central passage of the mixing tube extends from an upstream end to a downstream end of the annular wall with respect to a flow direction through the central passage of the mixing tube.

[0004] The air inlet region includes an air inlet region of the annular wall, which includes an outer surface and an inner surface of the annular wall. Starting at the upstream end of the annular wall and viewed in the downstream direction, the outer surface of the annular wall initially has a first constant outer diameter and then transitions via a step into a wall section with a second constant outer diameter that is smaller than the first outer diameter. An inner diameter of each mixing tube initially decreases from the upstream end of the annular wall in the downstream direction and then remains constant.

[0005] US 2012 / 0 181 354 A1 and US 2013 / 0 104 554 A1 disclose further multi-tube fuel nozzle systems with a plurality of mixing tubes and fuel injectors projecting into them, wherein the mixing tubes have an annular wall with an inlet region at the upstream end, the outer and inner surfaces of which are curved inwards in the downstream direction and continuously decrease in diameter, wherein the cross-sectional area of ​​the annular wall in the inlet region is substantially constant. BRIEF DESCRIPTION OF THE INVENTION

[0006] Certain embodiments within the scope of the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention; instead, these embodiments are intended to provide only a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments described below.

[0007] According to the invention, a system includes a multi-tube fuel nozzle. The multi-tube fuel nozzle includes a plurality of mixing tubes. Each mixing tube includes an annular wall disposed around a central passage and an air inlet region configured for placement around a fuel injector extending into the central passage of the mixing tube. The central passage of the mixing tube extends from an upstream end to a downstream end of the annular wall with respect to a flow direction through the central passage of the mixing tube. The air inlet region includes an annular wall air inlet region having a bell-shaped portion.Starting at the upstream end of the annular wall, an outer diameter of each mixing tube first increases in front of the bell-shaped section and then continuously decreases through the bell-shaped section in the flow direction through the central passage of the mixing tube to the downstream end, while an inner diameter of each mixing tube first decreases from the upstream end in front of the bell-shaped section and then remains constant in the flow direction through the central passage of the mixing tube to the downstream end of the annular wall. The cross-sectional area of ​​the annular wall of each mixing tube initially increases, starting at the upstream end and axially in the downstream direction toward the downstream end, then gradually decreases until it remains constant in a downstream section of the annular wall of the mixing tube.The decrease in the cross-sectional area defines the bell-shaped section of the air inlet area of ​​the ring wall.

[0008] The air inlet region of the annular wall of any of the above-mentioned systems may have a contoured surface at the upstream end of the annular wall.

[0009] The contoured surface of each of the aforementioned systems may include a contoured outer surface and a contoured inner surface, and a contoured turnaround portion may be disposed between the contoured outer surface and the contoured inner surface.

[0010] Each mixing tube of each of the above-mentioned systems may include a plurality of support structures in the form of radial arms extending from the annular wall to an inner support ring, the inner support ring being adapted to support the fuel injector.

[0011] Each system mentioned above may include a plurality of fuel injectors, each mixing tube including one of the fuel injectors disposed in the upstream end of the mixing tube.

[0012] Each system mentioned above may include a gas turbine engine or a combustor with the multi-tube fuel nozzle.

[0013] Each system mentioned above may include an end cover assembly and a retainer plate, and the plurality of mixing tubes may be disposed between the end cover assembly and the retainer plate.

[0014] Each mixing tube of the plurality of mixing tubes of each aforementioned system may be configured for individual removal from or installation between the end cover assembly and the retainer plate.

[0015] The retainer plate of any of the above-mentioned systems may be adapted for removal from the multi-tube fuel nozzle by sliding the retainer plate along the plurality of mixing tubes from the upstream end to the downstream end. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] These and other features, aspects and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, in which like reference numerals designate like parts throughout the drawings, in which: Fig. 1 is a block diagram of one embodiment of a gas turbine system having a multi-tube fuel nozzle in a combustor, the tubes being configured to distribute air evenly; Fig. 2 is a side sectional view of the embodiment of the gas turbine system of Fig. 1 is; Fig. 3 is a side sectional view of an embodiment of a portion of the burner of Fig. 2 is taken along line 3-3 with a multi-tube fuel nozzle connected to an end cover assembly of the burner; Fig. 4 is an exploded perspective view of a portion of the multi-tube fuel nozzle and end cover assembly of Fig. 3 is along a line 4-4; Fig. 5 a partial cross-sectional view of the burner of Fig. 3 along line 5-5 from Fig. 3 is; Fig. 6 is a front view of a cover side assembly of an embodiment of the multi-tube fuel nozzle of Fig. 3 illustrating multiple fuel tubes and fuel injectors of the multi-tube fuel nozzle; Fig. 7 is a perspective view of an upstream end of a single tube of the multi-tube fuel nozzle incorporating an airflow conditioning device taken along line 7-7 of Fig. 4 represents; Fig. 8 is a sectional view of the upstream end of a single tube of the multi-tube fuel nozzle of Fig. 7 illustrates the details of an airflow conditioner; Fig. 9 is a cross-sectional side view of one embodiment of the mixing tube and cover side assembly taken along line 9-9 of Fig. 6 is; Fig. 10 is a cross-sectional side view of an embodiment of the mixing tube and fuel injector including an airflow conditioner taken along line 10-10 of Fig. 6 illustrates; Fig. 11 is a partial view of the embodiment of the mixing tube and the fuel injector of Fig. 10, which illustrates details of the air flow entering the tube; and Fig. 12-15 are a series of views of one embodiment of a multi-tube fuel nozzle and burner end cover illustrating a method for removing tubes from the multi-tube fuel nozzle. DETAILED DESCRIPTION OF THE INVENTION

[0017] One or more specific embodiments of the present invention are described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation can be described in the specification. It should be appreciated that in developing each such actual implementation, as with any engineering or design project, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business constraints, which may vary from one implementation to another. Further, it should be appreciated that such a development effort may be complex and time-consuming, but would nevertheless be within the scope of design, manufacture, and fabrication of one of ordinary skill in the art having the benefit of this disclosure.

[0018] When introducing elements of various embodiments of the present invention, the terms "a," "an," "the," and "said" are intended to mean that one or more of the elements may be present. The terms "comprising," "including," and "having" are intended to be inclusive and to mean that additional elements besides the listed elements may be present. The present disclosure is directed to systems for conditioning airflow within a multi-tube fuel nozzle of a turbine system. The turbine system may include one or more multi-tube fuel nozzles. Each multi-tube fuel nozzle includes a plurality of mixing tubes (e.g., premixing tubes). Each tube includes an annular wall disposed around a central passage and an air inlet region configured for placement around a fuel injector extending into the central passage.The central passage extends from an upstream end of the tube's annular wall to a downstream end of the annular wall with respect to a flow direction through the central passage. The air inlet region includes an outer surface of the annular wall that gradually decreases in diameter in the flow direction. In the multi-tube fuel nozzle, pressurized air can enter mixing tubes through the air inlet regions, while the fuel injectors distribute fuel into the central passage, creating an air / fuel mixture. The air inlet surface conditions the air entering the mixing tubes and allows for substantially uniform mixing with the air before the mixture is subsequently directed to the combustion region. The air inlet surface can be configured to target specific air-side pressure drops and provide the best uniform airflow.Accordingly, the air inlet surface may include a bell-shaped configuration. The air inlet surface may include an inner surface that decreases in diameter along a portion of the air inlet region from the upstream end to the downstream end. A cross-sectional area in the inner surface of the air inlet surface may decrease in the flow direction. The air inlet region may include a contoured end configured to reduce pressure drop as air flows into the central passage through the air inlet region. The contoured end may include a contoured outer surface, a contoured inner surface, and a contoured turnaround portion disposed between the contoured outer surface and the contoured inner surface. The multi-tube fuel nozzle may include a plurality of premix tubes, each premix tube containing the air inlet region.In the multi-tube fuel nozzle including the plurality of premixing tubes, gaps may be established between the air inlet surfaces of adjacent premixing tubes for accelerating an air flow into each of the premixing tubes.

[0019] In the drawings and initially in Fig. 1 illustrates a block diagram of one embodiment of a gas turbine system 10. The gas turbine system 10 includes one or more fuel nozzles 12 (e.g., multi-tube fuel nozzles), a fuel supply 14, and a combustor 16. The fuel nozzle 12 receives compressed air 18 from an air compressor 20 and fuel 22 from a fuel supply 14. Although the present embodiments are discussed in the context of air as an oxidizer, the present embodiments may utilize air, oxygen or oxygen-enriched air, oxygen-depleted air, oxygen mixtures, or any combination thereof. As discussed in more detail below, the fuel nozzle 12 includes a plurality of fuel injectors 24 (e.g., 10 to 1000) and associated mixing tubes 26 (e.g.,10 to 1000), wherein each mixing tube 26 has an airflow conditioner 27 with an air inlet surface 28 for directing and conditioning an airflow into the corresponding tube 26, and each mixing tube 26 has a corresponding fuel injector 24 (e.g., in a coaxial or concentric arrangement) for injecting fuel into the corresponding tube 26. Each mixing tube 26, in turn, mixes the air and fuel along its length and then discharges an air / fuel mixture 30 into the combustor 16. In certain embodiments, the mixing tubes 26 may be described as micromixing tubes, which may have diameters between approximately 0.5 to 2, 0.75 to 1.75, or 1 to 1.5 cm. The mixing tubes 26 may be arranged in one or more bundles (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) of closely spaced tubes in a substantially parallel arrangement with respect to one another. In this embodiment, each mixing tube 26 is configured for mixing (e.g.,B. Micromixing) is established on a relatively small scale within each mixing tube 24, which then outputs a fuel / air mixture 30 into the combustion chamber. The airflow conditioner 27 (e.g., with the air inlet surface 28) of the disclosed embodiments provides raw-level air conditioning (ie, for each individual mixing tube 26) such that the flow and / or or the pressure of air into each tube 26 and between the plurality of tubes 26 can be controlled to provide better mixing of fuel and air.

[0020] The combustor 16 ignites the fuel / air mixture 30 to produce pressurized exhaust gases 32, which flow into a turbine 34. The pressurized exhaust gases 32 flow against and between blades of the turbine 34, thereby causing the turbine 34 to rotate. The turbine blades are connected to a shaft 36, which also rotates as the exhaust gases 32 exit the combustor 16. Finally, the exhaust gas 32 from the combustion process exits the turbine system 10 via an exhaust outlet 38. Blades in the compressor 20 are also connected to the shaft 36 and rotate as the shaft 36 is rotated by the turbine 34. The rotation of the blades in the compressor 20 compresses air 40 that has been drawn into the compressor 20 through an air inlet 42.The resulting compressed air 18 is then fed into the multi-tube fuel nozzle 12 of the combustor 16 as described above, where it is mixed with fuel and ignited, creating a substantially self-sustaining process. Further, the shaft 36 may be connected to a load 44. As will be appreciated, the load 44 may be any suitable device capable of generating power via the rotational output of a turbine system 10, such as a power generation plant, or an external mechanical load. The relationship between the consistency of the fuel / air mixture 30 and the efficient operation of the gas turbine system 10 can therefore be appreciated. The implementation of the multiple mixing tubes 26, each having an air inlet surface 28 for conditioning the compressed air 18, is described in more detail below.

[0021] Fig. Figure 2 is a side sectional view of the embodiment of the gas turbine system 10 of Fig. 1. As shown, the embodiment includes a compressor 20 connected to an annular array of burners 16. Each burner 16 includes at least one fuel nozzle 12 (e.g., a multi-tube fuel nozzle) that delivers the fuel / air mixture 30 to a combustion chamber 46 disposed within each burner 16. As discussed in detail below, certain embodiments of the mixing tubes 26 of the fuel nozzle 12 include specific features to more evenly distribute the compressed air 18 to produce a more uniform fuel / air mixture 30. The uniformity of the fuel / air mixture 30 provides for more efficient combustion, thereby increasing power and reducing emissions. The combustion of the fuel / air mixture 30 in the burners 16, as discussed above with respect to Fig. 1, causes the rotor blades in the turbine 34 to rotate as exhaust gases 32 (e.g., combustion gases) pass toward the exhaust outlet 38. Throughout this discussion, reference will be made to a set of axes. These axes are based on a cylindrical coordinate system and point in an axial direction 48, a radial direction 50, and a circumferential direction 52. For example, the axial direction 48 extends along a path or longitudinal axis 54 of the fuel nozzle 12, the radial direction 50 extends away from the longitudinal axis 54, and the circumferential direction 52 extends around the longitudinal axis 54.

[0022] Fig. 3 is a side sectional view of the burner 16 of the gas turbine system 10 of Fig. 2 and along line 3-3 from Fig. 2. As shown, the combustor 16 includes a head end 56 and a combustion chamber 46. The fuel nozzle 12 is positioned within the head end 56 of the combustor 16. Suspended within the fuel nozzle 12 are a plurality of mixing tubes 26 (e.g., air / fuel premix tubes). One embodiment of the mixing tubes 26 is shown including airflow conditioners 27 with air inlet surfaces 28 that allow compressed air 18 to enter and mix with fuel 22. The mixing tubes 26 extend substantially axially between an end cover assembly 58 of the combustor 16 and a cap side assembly 60 of the fuel nozzle 12. The mixing tubes 26 may be connected to the end cover assembly 58 and to the cap side assembly 60, as further described below. The end cover assembly 58 may provide a fuel inlet 62 and a fuel plenum 64 for providing fuel 22 to the plurality of fuel injectors 24.As discussed above, each individual fuel injector 24 is connected to only one mixing tube 26. During the combustion process, fuel 22 moves axially through each of the mixing tubes 26 from the end cover assembly 58 (via the fuel injectors 24), through the cap side assembly 60, and toward the combustion chamber 46. The direction of this movement along the longitudinal axis 54 of the fuel nozzle 12 is referred to as the downstream direction 66. The opposite direction is referred to as the upstream direction 68.

[0023] As described above, the compressor 20 compresses air 40 received from the air inlet 42. The resulting flow of pressurized compressed air 18 is delivered to the fuel nozzles 12 located in the head end 56 of the combustor 16. The air enters the fuel nozzles 12 for consumption in the combustion process through air inlets 70. More specifically, the pressurized air 18 from the compressor 20 flows in an upstream direction 68 through an annular space 72 formed between an insert 74 (e.g., an annular insert) and a flow sleeve 76 (e.g., an annular flow sleeve) of the combustor 16. At the end of this annular space 72, the compressed air 18 is forced into the air inlets 70 of the fuel nozzle 12 and fills an air plenum 78 in the fuel nozzle 12. The compressed air 18 in the air plenum 78 then enters the plurality of mixing tubes 26 through the air inlet surfaces 28 of the air flow conditioner 27.In addition to allowing the air 18 to enter the mixing tubes 26, the air inlet surface 28 of the airflow conditioner 27 can condition the air 18 in various ways as discussed below. Within the mixing tubes 26, the air 18 is then mixed with the fuel provided by the fuel injectors 24. The fuel / air mixture 30 flows in a downstream direction 66 from the mixing tubes 26 into the combustion chamber 46, where it is ignited and burned to produce the combustion gases 32 (e.g., exhaust gases). The combustion gases 32 flow from the combustion chamber 46 in the downstream direction 66 to a transition piece 80. The combustion gases 22 then pass through the transition piece 80 to the turbine 34, where the combustion gases 22 cause the blades in the turbine 34 to rotate.

[0024] Fig. Figure 4 illustrates an exploded perspective view of the multi-tube fuel nozzle 12 taken along line 4-4 of Fig. 3. This figure illustrates the arrangement, according to some embodiments, of the plurality of fuel injectors 24 on the end cover 58 and their relationship to the plurality of mixing tubes 26. As discussed above, the mixing tubes 26 are arranged to be axially disposed 48 between the end cover assembly 58 and the cap side assembly 60. The individual mixing tubes 26 are each paired with an individual fuel injector 24 and are configured to be disposed around that fuel injector 24 (e.g., in a coaxial or concentric arrangement). The air inlet surfaces 28 are located at a first end (e.g., the upstream 68 end) of the mixing tubes 26 proximate the fuel injectors 24. In certain embodiments, the fuel injectors 24 may be removably coupled to the end cover assembly 58.

[0025] Additionally illustrated Fig. 4 illustrates a support structure 82 (e.g., an annular cylinder, fuel nozzle cap) of the fuel nozzle 12 surrounding the mixing tubes 26 and other structures within the fuel nozzle 12. The support structure 82 extends from the end cover assembly 58 to the cap side assembly 60, generally protects and supports the structures positioned within the fuel nozzle 12, and defines the air plenum 78 within the fuel nozzle 12. Air inlets 70 are disposed on the support structure 82 and direct the compressed air 18 radially into the air plenum 78 on the inside of the fuel nozzle 12. A retainer plate 84 is located upstream 68 and proximate to the detachable cap side assembly 60. In certain embodiments, the nozzle 12 includes an annular airflow conditioning diffuser 86 surrounding the air inlets 70.

[0026] Fig. Figure 5 is a partial cross-sectional side view of the burner 16 taken along line 5-5 of Fig. 3. The head end 56 of the combustor 16 includes a portion of the multi-tube fuel nozzle 12. The support structure 82 surrounds the multi-tube fuel nozzle 12 and the plurality of mixing tubes 26. As discussed above, in some embodiments, each mixing tube 26 may extend axially between the end cover assembly 58 and the cap side assembly 60. The mixing tubes 26 may further extend through the cap side assembly 60 to feed the fuel / air mixture 30 directly into the combustion chamber 46. Each mixing tube 26 is positioned to surround a fuel injector 24 (e.g., in a coaxial or concentric arrangement) such that the injector 24 receives fuel 22 from the fuel plenum 64 and directs the fuel into the tube 26. The fuel plenum 64 is fed with fuel 22, which enters the fuel inlet 62 located on the end cover assembly 58.

[0027] As described above, compressed air 18 enters the fuel nozzle 12 through air inlets 70, which may be surrounded by a diffuser 86. The diffuser 86 may be annular and configured to precondition and distribute the pressurized air into the fuel nozzle 12 across the mixing tubes 26 in a variety of directions. The direction of airflow within the fuel nozzle 12 is substantially radially inward 88, but may have an upstream component 68 or a downstream component 66. The airflow varies across the mixing tubes 26, which are located at radially outward locations 90 within the fuel nozzle 12 closer to the air inlets 70. After entering the fuel nozzle 12 through the air inlet 70 and moving over the mixing tubes 26, the compressed air 18 enters each mixing tube 26 through an air inlet surface 28 of an air flow conditioner 27.In certain embodiments, the configuration of the air inlet surfaces 28 of the airflow conditioners 27 is varied between individual mixing tubes 26 based on their radial 50 locations within the fuel nozzle plenum 78. This specific adaptation may compensate for variations in air pressure and movement across the mixing tubes 26, namely the pressure drop that occurs in the radial inward direction 88. In certain embodiments, the axial 48 position of the air inlet surfaces 28 along the mixing tubes 26 may be varied to compensate for the axial 48 variations in air pressure. For additional control of the flow of the pressurized air 18, the air inlet surfaces 28 of the airflow conditioner 27 located at an upstream end 94 (e.g., a first end) of the mixing tube 26 may be configured to have any of a variety of shapes, sizes, and arrangements, as discussed further below.As also in . Fig. 5, in some embodiments, the retainer plate 84 and / or a baffle plate 92 may be positioned within the fuel nozzle 12, surrounding the downstream end 96 of the mixing tubes 26 substantially proximate the cap side assembly 60. The baffle plate 92 may include a plurality of impingement cooling apertures that may direct air jets for impingement against a rear side of the cap side assembly 60 to create impingement cooling.

[0028] Fig. 6 is a front view of one embodiment of the multi-tube fuel nozzle 12 illustrating the radial arrangement of the plurality of mixing tubes 26. The illustrated nozzle 12 includes a plurality of sectors 98 arranged circumferentially, 52, on the cap side assembly 60. The arrangement of the mixing tubes 26 affects the spacing between the tubes 26 and also the spacing between the air inlet surfaces 28 between adjacent tubes 26. The illustrated nozzle 12 includes a single liquid fuel cartridge 100 placed between each sector 98 and an additional liquid fuel cartridge 100 in the center of the cap side assembly 60. The liquid fuel cartridges 100 supply the fuel nozzle 12 with liquid fuel 22. In the present embodiment, each sector 98 includes a plurality of rows 102 of mixing tubes 26, with each row 102 having two or more tubes 26. The circumferential spacing 104 between each tube 26 in each row 102 is substantially the same.The radial spacing 106 between each row 102 in each sector 98 is also substantially the same. This results in substantially equal spacings between the tubes 26 and equal spacings between the air inlet surfaces 28 of the tubes 26. In other embodiments, other numbers of sectors 98 may be present. For example, there may be 1 to 20 sectors 98 (e.g., 2, 3, 4, 5, 6, 7, 8, 9, or 10). Each sector 98 may have different numbers of mixing tubes 26. For example, each sector may have 50, 100, 150, 200, or any other number of tubes 26. Additionally, it is contemplated that the tubes 26 may be non-uniformly spaced (e.g., with a varying circumferential spacing 104 and / or radial spacing 106) to control air pressure drops within the fuel nozzle 12. For example, the circumferential spacing 104 between adjacent tubes 26 may vary based on their proximity to the air inlets 70.In certain embodiments, the circumferential spacing 104 between the tubes 26 may be greater at locations closer to the air inlets 70 (e.g., where air pressure is greater) and reduced at locations within the fuel nozzle 12 (e.g., where air pressure has dropped). This arrangement may more evenly distribute air pressure around the periphery 52 of the fuel nozzle. Further, different arrangements of tubes 26 may maintain flow conditions of the compressed air 18 prior to entering the mixing tubes 26 such that the conditions (e.g., pressure, velocity) may be substantially matched to flow conditions of the compressed air entering the tubes 26. Additionally, the radial spacing 106 between rows of tubes 26 may be similarly varied based on their proximity to the air inlets 70 to control air pressure and velocity radially within the fuel nozzle 12.The arrangement of the individual tubes 26 may be determined to compensate for pressure drops that occur within the fuel nozzle 12 due to other structures, such as the liquid fuel cartridges 100. For example, a structure may cause a disturbance in the fuel pressure, and such a disturbance may be reduced or avoided by the placement of mixing tubes 26.

[0029] Fig. 7 is a perspective view of an upstream end 94 of a single tube 26 of the multi-tube fuel nozzle 12 defined by an annular wall 108. The tube 26 includes a central passage 110 defined in the annular wall 108, with support structures 112 extending radially from an inner surface 114 of the tube 26 to a support ring 116. The support structures 112 and the support ring 116 support the fuel injector 24 within the mixing tube 26, thereby limiting radial movement of the fuel injector 24 relative to the tube 26. The individual support structures 112 may be of any shape or size that provides adequate support for the support ring 116 while still allowing airflow past the support structures 112. The edges 118 of the support structures 112 may be square or contoured or have a combination of square or contoured surfaces.For example, the support structures 112 may have a vane-shaped cross-section to reduce flow resistance. The depth 120 of the support structures 112 may vary, and each individual support structure 112 may be arranged at positions further upstream 68 or downstream 66 in the mixing tube 26 to better control any disturbance to the compressed air 18. Only one or more support structures 112 may be connected to the support ring 116. The support ring 116 may also have different shapes and dimensions. For example, the edges 122 of the support ring 116 may be square, contoured, or have a combination of square and contoured surfaces. As shown, the outer surface 124 of the annular wall 108 of the mixing tube 26 initially increases and then decreases in diameter 126 from the upstream end 94 to the downstream end 96 of the annular wall 108.This design may enable smooth movement of the air flow in an axial direction 48 over the outer surface 124 of the annular wall 108 of the mixing tube 26. Furthermore, the diameter 126 of the outer surface 114 may be constant. These designs may enable variable control of the flow of the air 18. For example, for mixing tubes 26 located at more radially inner locations 50 within the fuel nozzle 12, the air pressure of the air entering the fuel nozzle 12 may be lower than in areas near the air inlets 70 of the fuel nozzle 12. This decrease in air pressure may be compensated for by an increased diameter 126 of the outer surfaces 124 of the mixing tubes 26, which reduces the available volume outside of and between the mixing tubes 26. This reduction in available volume contributes to accelerating the air flow into the air inlets 28.

[0030] Fig. Figure 8 is a perspective sectional view of the same upstream end 88 of the mixing tube 26. Shown are the support structures 112 and the support ring 116 disposed within the inner surface 114 of the mixing tube 26. The inner surface 114 has a diameter 128 that is constant from the upstream end 94 to the downstream end 96 of the annular wall 108. Thus, while the variation in diameter 126 of the outer surface 124 allows control of the airflow surrounding the mixing tube 26, the constant diameter 128 of the inner surface 114 of the mixing tube 26 allows selective control of the airflow into the central passage 110 of the mixing tube 26. The constant inner diameter 128 allows smooth movement of the airflow, avoiding swirls, separation, and losses that may occur due to fuel flow blockage.The reduction in diameter 128 changes the internal volume of the internal passage 110, allowing control of the air pressure within the mixing tube 26. The mixing tubes 26 can be configured to have a larger or smaller outer diameter 126, and larger or smaller changes in the outer diameter 126 in the axial direction to specifically adjust the airflow depending on the location of the tube 26 within the fuel nozzle 12.

[0031] Fig. 9 is a cross-sectional side view of one embodiment of the downstream end 96 of the mixing tube 26 assembled with the cap side assembly 60. Illustrated is one embodiment of the spatial relationship between the mixing tubes 26, the cap side assembly 60, and / or the end cover assembly 58. In some embodiments, the mixing tubes 26 may be attached to components in the head end 56 of the combustor 16, such as the cap side assembly 60, the retainer plate 84, and / or the baffle plate 92, by various fasteners and connections, such as welds, brazed joints, clamps, threaded fasteners, snap-fit ​​members, hinges, or other connections. In other embodiments, the mixing tubes 26 are held in a floating arrangement and supported only by one or more of the cap side assembly 60, the retainer plate 84, the baffle plate 92, various springs, or other support structures.Such floating assemblies can advantageously accommodate thermal expansion of the mixing tubes 18 and other components of the burner 14. Floating assemblies also allow for easier customization and design of mixing tubes 26 with various air port 28 configurations. If fuel / air mixtures 20 are found to be uneven, individual tubes 28 can be easily removed and replaced with tubes 26 having a different air port 28 (e.g., air flow conditioner 27) that better compensates for air pressure variations in the fuel nozzle 12. The floating assemblies can additionally be implemented by including an axial spring 130 to provide resilient axial support and limitation for the movement of the mixing tubes 26. According to the illustrated embodiment, the axial spring 130 can be positioned between a retainer plate 84 and baffle plate 92.Further, devices such as additional springs, channels and / or guides may be implemented to block movement of the mixing tubes 26 in the radial direction 50 or circumferential direction 52.

[0032] Fig. 10 is a cross-sectional side view of one embodiment of the mixing tube 26 installed around the fuel injector 24. As discussed above, the fuel injector 24 is positioned on the head end 56 of the fuel nozzle 12 and receives fuel from the fuel plenum 64. Fully assembled, the fuel injector 24 may be positioned substantially within the central passage 110 in the first end 94 of each mixing tube 26. This first end 94 is located on the upstream 68 side of the multi-tube fuel nozzle 12, adjacent the end cover assembly 58. The air inlet surfaces 28 are located on this first end 94 substantially close to or adjacent to the head end 56. In some embodiments, the fuel injector 24 may extend further downstream, and the air inlets 28 may accordingly be located at locations further downstream 66 from the head end 56.The design of the air inlets 28 can further be configured to control the flow of air 18 into the central passage 110 of the mixing tube 26. As discussed above, the outer surface 124 of the annular wall 108 of an individual mixing tube 26 can have a diameter 126 that decreases along the axial 48 downstream direction 66, which improves the air flow on the outside of the mixing tubes 26. Furthermore, the inner surface 114 of the annular wall 108 of the mixing tube 26 can have a diameter 128 that is constant along the axial 48 downstream direction 66, which avoids disturbances in the flow of compressed air 18 into the central passage 110 of the mixing tube 26. The tube 26 also includes a turnaround section 134 between the outer surface 124 of the annular wall 108 and the inner surface 114 of the annular wall 108, the turnaround section 134 (e.g., the contoured turnaround section) connecting the inner 114 and outer surfaces 124 of the annular wall 108 of the mixing tube 26.This turnaround section 134 of the tube may be angular (e.g., a conical surface) or contoured (e.g., a curved annular surface) to minimize and control airflow disturbances once pressurized air 18 enters the central passage 110. The turnaround section 134 may help gradually redirect the airflow into the tube 26 while helping to eliminate any low-velocity areas, a source of turbulence. If the inner surface 114, outer surface 124, and turnaround section 134 consist of contoured surfaces, the upstream end 94 of the mixing tube may form a bell-shaped configuration, e.g., a curved annular surface, that gradually decreases in diameter 126 in a curved manner. Fuel is supplied to a central passage 136 of the fuel injector 24 and distributed through the fuel ports 138 into the central passage 110 of the mixing tube 26.In the illustrated embodiment, the fuel ports 138 are located on the tapered portion 140, which may have a straight or curved taper in the downstream direction 66. For example, the tapered portion 140 may be formed as a conical wall, an inwardly curved annular wall (e.g., curved inward toward the axis of the injector 24), an outwardly curved annular wall (e.g., curved outward away from the axis of the injector 24), or a combination thereof. In the illustrated embodiment, a tapered portion 140 extends from a first position upstream 68 of the air ports 28 to a second position downstream 66 of the air ports 26 of the mixing tube 26. As illustrated, the tapered portion 140 of the fuel injector 24 gradually decreases in diameter in the downstream direction 66 (i.e.,, it converges) to thereby gradually increase the cross-sectional area between the fuel injector 24 and the mixing tube 22 in the downstream direction 66. In this way, the illustrated embodiment provides a gradual pressure drop between the fuel injector 24 and the mixing tube 26 to thereby help improve the flow and mixing of fuel and air. In the illustrated embodiment, the airflow conditioner 27 (e.g., the air inlet 28) along the mixing tube 26 and the fuel ports 138 along the fuel injector 24 (e.g., the tapered portion 140) are both disposed upstream of a tip 142 of the fuel injector 24 such that the air and fuel mix at least partially along the decreasing cross-sectional area between the fuel injector 24 and the mixing tube 26.Furthermore, the illustrated air inlet 28 is arranged upstream of the fuel ports 138 to increase the pressure upstream of the fuel ports 138.

[0033] Fig. Figure 11 illustrates a portion of the embodiment of the mixing tube and fuel injector of Fig. 10, illustrating details of the flow of compressed air 18 as it enters the mixing tube 26 and is conditioned by the airflow conditioner 27. As discussed above, the contouring of the outer surface 124 of the tube 26 enables accelerated movement 150 of the compressed air along the outer surface 124 of the tubes 26. Gaps between adjacent tubes are designed to adjust flow conditions before and after entering the tube and to accelerate the incoming airflow 152 into the tubes. The contouring along the turnaround section 134 of the annular wall defining the mixing tube 26 serves to gradually increase the cross-sectional area 144 of the tube 26 at the turnaround section and reduce pressure losses during the turnaround.Because the inner diameter 128 of the tube 26 is constant in the flow direction while the outer diameter 126 decreases, the cross-sectional area 146 also gradually decreases until it is constant 148 in downstream sections of the tube. This decrease in the cross-sectional area 148 defines the bell-shaped section of the tube 26. The decreasing contour of the turnaround section 134 is located at the upstream end of the bell-shaped section and minimizes flow separation and provides a preferred pressure and velocity profile for the incoming air 152. Once the pressurized air 18 has entered the mixing tube 26 via the air inlet 28, the contoured inner surface 114 provides additional axial acceleration 154 of the air 18 along the center passage 110 of the mixing tube.The increased axial movement 154 of the air 18 upstream of the fuel ports 138 of the fuel injector 24 serves to minimize blockage of the fuel 22 entering the mixing tube 26 and to improve the mixing of the fuel 22 and the air 18. Overall pressure drops are reduced and flame holding risks are mitigated by the contoured surfaces 124, 134 and 114.

[0034] Fig. 12-15 are corresponding views of the fuel nozzle 12 illustrating a series of steps of a method for removing at least one mixing tube 26 according to certain embodiments. As shown in Fig. 12, the multi-tube fuel nozzle 12 is removed from the head end 56 of the burner 16 and connected to the end cover assembly 58. The end cover assembly 58 is shown with the fuel inlet 62 connected to the support structure 82 and the cover side assembly 60. To access the mixing tubes 26, as shown in Fig. 13 the end cover assembly 58 is separated from the support structure 82 and the lid side assembly 60, 158. Fig. 13 discloses the fuel injectors 24 connected to the end cover assembly 58 of the fuel nozzle 12. Then, as shown in Fig. 14, the retainer plate 84 is removed from the cover side assembly 60 by sliding the retainer plate 84 along the mixing tubes 26 in an upstream 68 direction from the second end 96 to the first end 94 of the mixing tubes 26. As shown in Fig. 15, the mixing tubes 26 can then be removed from their position on the cover side assembly 60. Removal of one or more mixing tubes 26 can be for inspection, replacement, repair, or any other purpose found during the course of manufacture, installation, and operation of the fuel nozzle 12. Installation of the mixing tubes 26 is achieved by removing the Fig. 12-15 in reverse order. Namely, the one or more mixing tubes 26 can be inserted into position on the cover side assembly 60 (50), then the holder plate 84 can be installed by sliding it over the mixing tubes 26 from the first end to the second end 96 until the tubes 26 are engaged with the cover side assembly 60 and / or the baffle plate 92 ( Fig. 14). The support structure 82 is then connected to the end cover assembly 58 by connecting the mixing tubes 26 to their respective fuel injectors 24 ( Fig. 13). The assembled fuel nozzle 12 ( Fig. 12) can then be installed in the head end 56 of the burner 12.

[0035] Technical implications of the disclosed embodiments include systems for improving the mixing of air 40 and fuel 14 in multi-tube fuel nozzles 12 of a gas turbine system 10. In particular, the fuel nozzle 12 is equipped with a plurality of mixing tubes 26 having air inlets 28 through which pressurized compressed air entering the fuel nozzle 12 is directed and mixed with fuel 22 injected into the plurality of fuel injectors 24. The air inlets 28 can be configured with various shapes, dimensions, spatial arrangements, and can be configured to direct the air at various angles. This specific adaptation improves mixing and uniformity by compensating for the varying pressures of air 18 and fuel 22 between the plurality of fuel injectors 24 in the multi-tube fuel nozzle 12.The enhanced mixing of air 18 and fuel 22 increases flame stability in burner 16 and reduces the amount of undesirable combustion byproducts. The system according to the invention enables removal and replacement of individual mixing tubes 26 and allows for cost-effective and efficient repair of fuel nozzle 12.

[0036] Although some typical sizes and dimensions have been provided above in the present disclosure, it should be understood that the various components of the described burner can be scaled up or down, as well as customized for different types of burners and different applications. This description uses examples to disclose the invention, including its best mode, and also to enable any person skilled in the art to practice the invention, including making and using all elements and systems and performing all incorporated methods. The patentable scope of the invention is defined by the claims and may include other examples apparent to those skilled in the art.Such further examples are intended to be included within the scope of the invention if they contain structural elements that do not differ from the literal language of the claims, or if they contain equivalent structural elements with insubstantial changes from the literal language of the claims.

[0037] A system includes a multi-tube fuel nozzle. The multi-tube fuel nozzle includes a plurality of mixing tubes. Each mixing tube includes an annular wall disposed around a central passage and an air inlet region configured for placement around a fuel injector extending into the central passage. The central passage extends from an upstream end to a downstream end of the annular wall with respect to a flow direction through the central passage. The air inlet region includes an air inlet surface of the annular wall that gradually decreases in diameter in the flow direction. LIST OF REFERENCE SYMBOLS 10 Gas turbine system 12 fuel nozzles 14 Fuel supply 16 burners 18 Compressed air 20 air compressors 22 Fuel 24 fuel injectors 26 assigned mixing tubes 27 airflow conditioners 28 Air inlet surface 30 air / fuel mixture 32 pressurized exhaust gases 34 turbines 36 Wave 38 Exhaust outlet 40 air 42 Air intake 44 Last 46 Combustion chamber 48 axial direction 50 radial direction 52 Circumferential direction 54 Longitudinal axis 56 headboard 58 End cover assembly 60 Cover side assembly 62 Fuel inlet 64 Fuel collection chamber 66 Downstream direction 68 Upstream direction 70 air intakes 72 annular space 74 deployment 76 Flow sleeve 78 Air collection chamber 80 transition piece 82 Support structure 84 Holder plate 86 Power conditioning diffuser 88 radially inward 90 radial outward 92 baffle plate 94 upstream end 96 downstream end 98 several sectors 100 fuel cartridges 102 multiple rows 104 Circumferential distance 106 radial distance 108 Ring wall 110 Central passage of the mixing tube 112 Fuel injector support structures 114 Interior surface 116 support ring 118 edges 120 depth 122 edges 124 Exterior surface 126 diameter 128 diameter 130 axial spring 134 Turning section 136 Central passage of the 138 fuel connections 140 tapered section 142 lace 144 pipe 146 cross-sectional area 148 cross-sectional area 150 Movement 152 Airflow 154 axial acceleration 156 incoming fuel 158 replaced

Claims

[1] System comprising: a multi-tube fuel nozzle (12) comprising: a plurality of mixing tubes (26), each mixing tube (26) comprising: an annular wall (108) arranged around a central passage (110) of the mixing tube (26), the central passage (110) of the mixing tube (26) extending from an upstream end (94) to a downstream end (96) of the annular wall (108) with respect to a flow direction through the central passage (110) of the mixing tube (26); and an air inlet region adapted to be arranged around a fuel injector (24) extending into the central passage (110) of the mixing tube (26), the air inlet region comprising an air inlet region of the annular wall (108) having a bell-shaped section; wherein, starting at the upstream end (94) of the annular wall (108), an outer diameter (126) of each mixing tube (26) first increases in front of the bell-shaped section and then continuously decreases through the bell-shaped section in the flow direction through the central passage (110) of the mixing tube (26) to the downstream end (96), and an inner diameter (128) of each mixing tube (26) first decreases from the upstream end (94) in front of the bell-shaped section and then remains constant in the flow direction through the central passage (110) of the mixing tube (26) to the downstream end (96) of the annular wall (108); wherein the cross-sectional area (144, 146, 148) of the annular wall (108) of each mixing tube (26) initially increases, starting at the upstream end (94) and axially in the downstream direction toward the downstream end (96), then gradually decreases until it remains constant in a downstream section of the annular wall (108) of the mixing tube (26), the decrease in the cross-sectional area (146) defining the bell-shaped section of the air inlet region of the annular wall (108). [2] The system of claim 1, wherein the air inlet region of the annular wall (108) has a contoured surface at the upstream end of the annular wall (108). [3] The system of claim 2, wherein the contoured surface comprises a contoured outer surface (124), a contoured inner surface (114), and a contoured turnaround portion (134) disposed between the contoured outer surface (124) and the contoured inner surface (114). [4] The system of claim 1, wherein each mixing tube (26) includes a plurality of support structures (112) in the form of radial arms extending from the annular wall (108) to an inner support ring (116), the inner support ring (116) being configured to support the fuel injector (24). [5] The system of claim 1, comprising a plurality of fuel injectors (24), each mixing tube (26) comprising one of the fuel injectors (24) disposed in the upstream end (94) of the mixing tube (26). [6] The system of claim 1, comprising a gas turbine engine or combustor (16) having the multi-tube fuel nozzle (12).

7. The system of claim 1, further comprising: an end cover assembly (58); and a holder plate (84); wherein the plurality of mixing tubes (26) are disposed between the end cover assembly (58) and the holder plate (84).

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