TECHNICAL FIELD
The application relates to a fuel injector, more particularly a fuel injector for multi-staged fuel injection in gas turbine assemblies.
BACKGROUND
A gas turbine (GT), in general, burns fuel with air, which contains a significant amount of nitrogen. Consequently, nitrogen oxides (NOx), which is known as air pollutant, is produced in fuel combustion and emitted into exhaust. Typically, higher flame temperature enhances production of NOx. Therefore, lowering emission of NOx in fuel combustion in a GT has been sought by burning fuel at multiple stages (i.e., in a prolonged time) rather than at a single stage.
When fuel is burned at multiple stages, combustion products of the first stage at relatively high temperature are mixed with pre-burned fuel/air mixture of later stages. Effective mixing of pre-burned fuel/air mixture in subsequent stages with the hot first-stage combustion products is necessary for reduced carbon mono-oxide (CO) production in the exhaust and for an improved temperature profile at an inlet of a subsequent turbine stage.
SUMMARY
A fuel injector according to one or more embodiments includes: a flat tube disposed over an aperture on a wall of a combustor that extends toward a turbine in a gas turbine system. The flat tube is configured such that air compressed by a compressor of the gas turbine system flows perpendicular to a thickness direction of the flat tube before flowing through the aperture. The flat tube has a fuel hole through which gaseous fuel that flows inside the flat tube exits to a passage of the air. An entire length of a downstream edge of the flat tube with respect to a flow of the air is disposed within the aperture when viewed perpendicular to the wall.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic overview of a gas turbine system according to one or more embodiments;
FIG. 2 shows a schematic cross-sectional view of a combustor according to one or more embodiments;
FIG. 3 shows a second-stage fuel injector according to one or more embodiments;
FIG. 4 shows a flat tube used in a second-stage fuel injector according to one or more embodiments;
FIG. 5 shows a cross-sectional view of a flat tube used in a second-stage fuel injector according to one or more embodiments;
FIG. 6 shows an expanded perspective view of a co-axial pipe attached to an edge of a flat tube according to one or more embodiments;
FIG. 7-12 show distributions of inner tube holes and outer tube holes along the longitudinal direction of a co-axial pipe according to one or more embodiments;
FIG. 13 shows a top view of a second-stage fuel injector according to one or more embodiments;
FIG. 14 shows a second-stage fuel injector according to one or more embodiments;
FIG. 15 shows a cross-sectional view of a second-stage fuel injector according to one or more embodiments;
FIGS. 16A and 16B show schematic side views of second-stage fuel injectors according to one or more embodiments;
FIG. 17 shows a schematic top view of a flat tube of a second-stage fuel injector according to one or more embodiments;
FIG. 18 shows a schematic view of an unwrapped flat tube according to one or more embodiments;
FIG. 19 shows a perspective view of a second-stage fuel injector according to one or more embodiments;
FIG. 20 shows a top view of a second-stage fuel injector according to one or more embodiments;
FIG. 21 shows a cross-sectional view of a second-stage fuel injector according to one or more embodiments;
FIG. 22 shows a schematic distribution of fuel holes of a second-stage fuel injector according to one or more embodiments, and
FIG. 23 shows a perspective view of a second-stage fuel injector according to one or more embodiments.
DETAILED DESCRIPTION
FIG. 1 shows a schematic overview of a gas turbine system according to one or more embodiments. As shown in FIG. 1, gas turbine system 1 includes: rotor 8 and casing 20. The rotor 8 rotates around an axis of the rotor 8 that is disposed along a longitudinal (axial) direction of the rotor 8. The casing 20 encloses the rotor 8.
When the gas turbine system 1 is considered in view of its function, the gas turbine system 1 includes: compressor 2; combustors 4; and turbine 6. The compressor 2 includes: rows of stator blades 16 fixed to the casing 20; and row of rotor blades 18 fixed to the rotor 8. The rows of the stator blades 16 and the rows of the rotor blades 18 are alternatingly disposed in the longitudinal direction of the rotor 8. Air is introduced from inlet 12 into the rows of the stator blades 16 and the rows of the rotor blades 18. The rows of the stator blades 16 and the rotor blades 18 compress the air as it flows from the upstream (left in FIG. 1) toward the downstream (right in FIG. 1).
In each of the combustors 4, fuel is injected and mixed with the air compressed by the compressor 2. Further, the mixture of the fuel and the compressed air is ignited in the combustors 4 and the enthalpy of the mixture (i.e., combustion products) of the fuel and the compressed air is increased.
The combustion products produced in the combustors 4 are then guided to the turbine 6, in which rows of stator blades fixed to the casing 20 and rows of rotor blades fixed to the rotor 8 are alternatingly disposed. While the combustion products of high enthalpy flow through the rows of the rotor blades and the rows of the stator blades in the turbine 6, the enthalpy of the combustion products is converted to a power of rotation of the rotor 8.
As shown in FIG. 1, the gas turbine system 1 can include two or more of the combustors 4. In the exemplified construction shown in FIG. 1, sixteen (only five are shown) of the combustors 4 are disposed circumferentially around a section of the rotor 8 between the compressor 2 and the turbine 6.
FIG. 2 shows a schematic cross-sectional view of the combustor 4 according to one or more embodiments. As shown in FIG. 2, the combustor 4 is attached to the casing 20 and includes: combustor liner 46; and burners 50 (first-stage fuel injectors). The combustor liner 46 includes: upstream piece 47 that surrounds the burners 50; and transition piece 48 that connects the upstream piece 47 and the inlet of the turbine 6. The upstream piece 47 and the transition piece 48 may be manufactured together as an integrated single piece.
The air (compressed air 10) compressed by the compressor 2 enters combustor plenum 40 via plenum inlet 40a. Thereafter, the compressed air 10 flows outside of the combustor liner 46 and is introduced around the burners 50 as shown in open arrows in FIG. 2. Around the burners 50, fuel introduced into the combustor 4 through fuel inlet ports 52 is injected and mixed with the compressed air 10. As the mixture of the compressed air 10 with the injected fuel flows inside the upstream piece 47, fuel in the mixture burns (i.e., is oxidized by oxygen in the compressed air 10). Burned mixture (i.e., combustion products) flows inside the transition piece 48 and is guided to the inlet of the turbine 6.
According to one or more embodiments, one or more second-stage fuel injectors 100 are disposed on a wall of the transition piece 48, as shown in FIG. 2. While a portion of the compressed air 10 guided to the combustor plenum 40 flows through the second-stage fuel injectors 100, additional fuel (of the same kind as injected at the burners 50 or of different kinds) is injected and mixed with the compressed air 10. The mixture of the additional fuel with the compressed air 10 mixes with the combustion products inside of the transition piece 48. The combustion products from the burners 50 are at high temperature in the transition piece 48 and the additional fuel burns inside the transition piece 48. Accordingly, the enthalpy of the combustion products is further increased with the additional fuel (and its combustion in the transition piece 48). The second-stage fuel injectors 100 may be disposed at any location of the transition piece 48 in the longitudinal direction of the combustor 40 as far as downstream of the burners 50 with respect to the flow of the combustion products. The second-stage fuel injectors 100 may even be disposed on a wall of the upper piece 47 downstream of the of the burners 50.
FIG. 3 shows a second-stage fuel injector according to one or more embodiments. Second-stage fuel injector 200 shown in FIG. 3 includes: hub 210; flat tubes 220; and circumferential wall 230. The circumferential wall 230 is fixed at the circumference of aperture 80 on the sidewall of the transition piece 48 via base flange 270 that protrudes outward from the sidewall of the transition piece 48. Ribs 272 are disposed on the inside surface of the base flange 270. The inside space of the transition piece 48 communicates with the outside space of the transition piece 48 through the aperture 80 on the sidewall to which the second-stage fuel injector 200 is fixed. Accordingly, the second-stage fuel injector 200 forms a passage of the compressed air along with the aperture 80. In other words, the compressed air 10 guided to the combustor plenum 40 outside the transition piece 48 can flow into the inside space of the transition piece 48 through the aperture 80. The shape of the aperture 80 shown in FIG. 3 is substantially circular although it is not limited thereto.
The hub 210 is disposed at a substantially center of the aperture 80 and one or more flat tubes 220 extend from the hub 210 to the inner surface of the circumferential wall 230. Because the circumferential wall 230 is fixed at the circumference of the aperture 80, the entire lengths of the flat tubes 220 are disposed within the aperture 80 when viewed perpendicular to the sidewall of the transition piece 48. The hub 210 has an interior space and fuel supply line 215 is connected to the hub 210. Accordingly, the fuel (mostly gaseous fuel) supplied through the fuel supply line 215 can be delivered to the inside of the flat tubes 220 via the interior space of the hub 210. In one or more embodiments, the flat tubes 220 are attached to the hub 210 at one end of the hub 210 and the fuel supply line 215 is attached to the other end of the hub 210.
Details of one of the flat tubes 220 according to one or more embodiments is shown in FIGS. 4 and 5. The flat tube 220 is a tube that extends in its longitudinal direction DL, as shown in FIG. 4. The cross-section of the flat tube 220 in a cut plane perpendicular to the longitudinal direction DL has a flat oblong shape, as shown in FIG. 5. The direction of the major axis in the cross-section of the flat tube 220 is referred as “transverse” direction (or “width” direction) DW as shown in FIGS. 4 and 5, and the direction of the minor axis in the cross-section is referred as “thickness” direction DT as shown in FIG. 5. As shown in FIG. 4, the longitudinal direction DL of the flat tube 220 is not necessarily straight. Accordingly, the longitudinal, transverse, and thickness directions DL, DW, DT at one location of the flat tube 220 may be different from the corresponding directions at another location.
As shown in FIG. 3, the transverse direction of the flat tube 220 is substantially perpendicular to the surface of the wall of the transition piece 48. In other words, the flat tubes 220 in the second-stage fuel injector 200 are oriented such that the flow of the compressed air 10 from the outside of the transition piece 48 to the inside of the transition piece 48 through the second-stage fuel injector 200 may not be blocked.
As shown in FIG. 4, the flat tube 220 includes fuel hole 240 that communicates the interior of the flat tube 220 with the exterior. With this fuel hole 240, fuel supplied to the interior of the flat tube 220 can be injected into the compressed air 10 that flows outside the flat tube 220. As shown in FIGS. 4 and 5, the fuel hole 240 may be disposed at the center of the flat tube 220 in the transverse direction DW. Additionally or alternatively, the fuel hole 240 may be disposed near the upstream edge and/or the downstream edge of the flat tube 220 with respect to the flow of the compressed air 10 in the transverse direction DW of the flat tube 220.
Furthermore, as shown in FIGS. 4 and 5, the flat tube 220 may include a co-axial tube 250 at the downstream edge of the flat tube 220 with respect to the flow of the compressed air 10 (in other words, at one edge of the flat tube 220 in the transverse direction). The co-axial tube 250 includes: inner tube 252; and outer tube 254 that encloses the inner tube 252, as shown in FIG. 5. This construction of the co-axial tube 250 allows a first fluid to be supplied inside the inner tube 252 and a second fluid to be supplied outside the inner tube 252 (and inside the outer tube 254). For example, the first fluid supplied inside the inner tube 252 may be a liquid fuel and the second fluid supplied outside the inner tube 252 may be water. Water supplied outside the inner tube 252 may cool the liquid fuel supplied inside the inner tube 252 and may protect the liquid fuel against heat from the outside of the flat tube 220, especially from the combustion products from the burners 50.
In one or more embodiments, the co-axial tube 250 includes fin plate 256 that extends along the longitudinal axis of the co-axial tube 250 and from the inside of the inner tube 252 to the outside of the outer tube 254, as shown in FIG. 5. The fin plate 256 may extend across the inner tube 252 and may divide the inside space of the inner tube 252 into two separate portions. The fin plate 256 may extend further out of the outer tube 254 toward downstream of the compressed air 10 that flows around the flat tube 220.
FIG. 6 shows an expanded perspective view of the co-axial tube 250 according to one or more embodiments. The inner tube 252 of the co-axial tube 250 may have inner tube hole 262 and the outer tube 254 may have outer tube hole 264. The first fluid supplied inside the inner tube 252 exits to the outside of the inner tube 252 through the inner tube hole 262 and may mix with the second fluid that is supplied outside the inner tube 252 (and inside the outer tube 254). Further, the mixture of the first fluid and the second fluid may exit the outer tube 254 through the outer tube hole 264 to the exterior of the co-axial tube 250.
In the embodiments shown in FIGS. 4-6, the portion of the fin plate 256 (pre-filming lip) that extends out of the outer tube 254 down in the flow direction of the compressed air 10 may serve as an atomizer for the mixture of the first fluid and the second fluid that exits the outer tube 254 through the outer tube hole 264 to the exterior of the co-axial tube 250. More specifically, the mixture of the first fluid and the second fluid from the co-axial tube 250 are spread out onto the surface of the fin plate 256 with the compressed air 10 flowing over the surface of the fin plate 256 so that a relatively thin film of mixture of the first fluid and the second fluid is produced on the surface of the fin plate 256. High velocity air flow of the compressed air 10 produces waves and instabilities of the mixture of the first fluid and the second fluid on the surface of the thin film that are sheared into clumps (ligaments) and droplets of the mixture of the first fluid and the second fluid as the compressed air 10 passes over the downstream edge of the fin plate 256 with respect to the flow of the compressed air 10. In one or more embodiments, the first fluid supplied inside the inner tube 252 may be oil and the second fluid supplied outside the inner tube 252 may be water. In that case, the hydrodynamic instability created by the immiscibility of the oil and the water also destabilizes the mixture of the first fluid and the second fluid on the fin plate 256, further enhancing the atomization process of the mixture of the first fluid and the second fluid.
FIG. 7 shows a schematic diagram describing exemplary distributions of the inner tube holes 262 and the outer tube holes 264 along the longitudinal direction of the co-axial tube 250 (i.e., the longitudinal direction DL of the flat tube 220) according to one or more embodiments. More specifically, in one or more embodiments, the inner tube 252 has two or more inner tube holes 262 which are disposed at respective longitudinal locations of the co-axial tube 250. Further, the outer tube 254 has two or more outer tube holes 264 which are disposed at respective longitudinal locations of the co-axial tube 250. The number of the inner tube holes 262 may be the same as or different from the number of the outer tube holes 264. Further, relative locations of the outer tube holes 264 with respect to the inner tube holes 262 in the longitudinal direction DL may be arbitrary and, in one or more embodiments, the outer tube holes 264 may be aligned with the inner tube holes 262. In one or more embodiments shown in FIG. 7, the inner tube holes 262 are offset from the outer tube holes 264 in the longitudinal direction of the co-axial tube 250. In other words, in one or more embodiments, none of the inner tube holes 262 and the outer tube holes 264 share their longitudinal locations in the co-axial tube 250. This construction of the inner tube holes 262 and the outer tube holes 264 enhances mixture of the first fluid supplied inside the inner tube 252 with the second fluid supplied outside the inner tube 252 before the mixture is expelled out of the co-axial tube 250.
The above construction of the inner tube holes 262 and the outer tube holes 264 is further described in reference of FIGS. 8-12 that show cross sections of the co-axial tube 250 at the various locations shown in FIG. 7.
Similar to FIG. 5, FIG. 8 shows a cross section of the co-axial tube 250 at a location where neither the inner tube hole 262 nor the outer tube hole 264 falls on. As shown in FIG. 8, neither the inner tube 252 nor the outer tube 254 has an opening at this location.
At one longitudinal location of the co-axial tube 250 (the location designated with the cut-line A-A in FIG. 7), the outer tube 254 has the outer tube hole 264, as shown in FIG. 9. The outer tube hole 264 at this longitudinal location is disposed close to the fin plate 256 (in other words, toward the downstream edge with respect to the flow of the compressed air 10) and on one side of the fin plate 256 (in this example, on the right side of the fin plate 256 in the view of FIG. 9). The inner tube 252 does not have the inner tube hole 262 at this longitudinal location.
At another longitudinal location of the co-axial tube 250 (the location designated with the cut-line B-B in FIG. 7), the outer tube 254 does not have the outer tube hole 264 and the inner tube 252 has the inner tube hole 262, as shown in FIG. 10. The inner tube hole 262 at this longitudinal location is disposed at a circumference that is farthest from the locations where the fin plate 256 intersects with the inner tube 252 and on one side of the fin plate 256 (in this example, on the right side of the fin plate 256 in the view of FIG. 10).
At a further different longitudinal location of the co-axial tube 250 (the location designated with the cut-line C-C in FIG. 7), the outer tube 254 has the outer tube hole 264 whereas the inner tube 252 does not have the inner tube hole 262, as shown in FIG. 11. The outer tube hole 264 at this longitudinal location is disposed close to the fin plate 256 (in other words, toward the downstream edge with respect to the flow of the compressed air 10) and on the side of the fin plate 256 opposite to the side of the outer tube hole 264 shown in FIG. 9 (i.e., in this example, on the left side of the fin plate 256 in the view of FIG. 11).
At a further different longitudinal location of the co-axial tube 250 (the location designated with the cut-line D-D in FIG. 7), the outer tube 254 does not have the outer tube hole 264 and the inner tube 252 has the inner tube hole 262, as shown in FIG. 12. The inner tube hole 262 at this longitudinal location is disposed at a circumference that is farthest from the locations where the fin plate 256 intersects with the inner tube 252 and on the side of the fin plate 256 opposite to the side of the inner tube hole 262 shown in FIG. 10 (i.e., in this example, on the left side of the fin plate 256 in the view of FIG. 12).
In the embodiments shown in FIG. 7, a sequence of the inner tube holes 262 and the outer tube holes 264 shown in FIGS. 9-12 iterate along the longitudinal direction of the co-axial tube 250. In other words, the cross section at the cut-line E-E is substantially the same as the cross section at the cut-line A-A. Further, the cross section at the cut-line F-F is substantially the same as the cross section at the cut-line B-B. However, the distribution of the inner tube holes 262 and the outer tube holes 264 is not limited to this sequence. In other words, in one or more embodiments, the cross sections shown in FIGS. 9-12 may show up in different sequences than the sequence of FIGS. 9-12 along the longitudinal direction of the co-axial tube 250. Further, the cross sections shown in FIGS. 9-12 may randomly show up along the longitudinal direction of the co-axial tube 250.
FIG. 13 shows a top view of the second-stage fuel injector 200 without the fuel supply line 215. In this view, the second-stage fuel injector 200 includes 8 flat tubes 220 that extend from the hub 210 to the inner surface of the circumferential wall 230. As shown in FIG. 13, the flat tubes 220 extend almost radially over the aperture 80 of the sidewall of the transition piece 48. However, in one or more embodiments, the flat tubes 220 may have one or more bends in the top view (as shown in FIG. 13) and may not extend straight (or extend nonlinearly) from one end attached to the hub 210 to the other end attached to the inner surface of the circumferential wall 230. When the flat tube 220 has one or more bends from one end attached to the hub 210 to the other end attached to the inner surface of the circumferential wall 230, the total length of the flat tube 220 along the longitudinal direction DL of the flat tube 220 becomes longer than the straight distance from the end attached to the hub 210 to the other end attached to the inner surface of the circumferential wall 230. Then, when the sidewall of the transition piece 48 vibrates or tends to elongate/shrink due to operation of the burners 50, the relative displacement/deformation of the circumferential wall 230 with respect to the hub 210 can be accommodated by elastic/plastic deformation of the flat tube 220 without fracture of the flat tube 220.
The shape of the flat tubes 220 is identical among the flat tubes 220 in the embodiments shown in FIG. 13. For example, as shown in FIG. 13, the profile of one of the flat tubes 220 viewed in the direction of the flow of the compressed air (i.e., the top view as shown in FIG. 13 or the transverse direction DW of the flat tubes 220) may be sinusoidal. However, the shape need not necessarily be sinusoidal and may be different among the flat tubes 220 in other embodiments.
Further shown in FIG. 13 with open arrows are approximate locations of the fuel holes 240 and directions of fuel flows that exit the flat tubes 220 into the flow of the compressed air 10 in one or more embodiments. In one or more embodiments, fuel may exit at substantially identical radial locations among the flat tubes 220 and all of the directions may be aligned in clockwise orientations when viewed along the direction of the flow of the compressed air 10, as shown in FIG. 13. However, the directions may be in counterclockwise orientations. Further, the directions may not be aligned in certain orientations and, for example, may alternate between the clockwise and counterclockwise orientations among the flat tubes 220. Furthermore, the locations of the fuel holes 240 and the directions of the fuel flows may appear random. Further, each of the flat tubes 220 may have two or more of the fuel holes 240 at different radial and transverse locations with same or different clockwise/counterclockwise directions.
FIG. 14 shows another construction of second-stage fuel injector 300 according to one or more embodiments.
In this construction, flat tube 320 has substantially the same fundamental construction as the flat tube 220 described in reference to FIGS. 4-12, including fuel holes 340. Although not shown in FIG. 14 (and subsequent figures), the flat tube 320 may include co-axial tubes like the co-axial tube 250 of the flat tube 220.
The longitudinal direction of the flat tube 320 is in a spiral shape over the aperture 80 of the sidewall of the transition piece 48 when viewed in the direction of the flow of the compressed air 10 through the aperture 80, as shown in FIG. 14. In one or more embodiments, the second-stage fuel injector 300 includes base flange 370 attached to the sidewall of the transition piece 48 at the aperture 80. The base flange 370 has an opening at the center and accommodates the spiral shape of the flat tube 320, as shown in FIG. 14. The inner surface of the opening of the base flange 370 includes ribs 372 that protrude toward the center of the aperture 80 and may barely touch the flat tube 320. In other words, the spiral shape of the flat tube 320 may fit inside the ribs 372. With this construction, the ribs 372 support the flat tube 320 at the center of the opening of the base flange 370 and aligns the spiral shape of the flat tube 320 with the aperture 80 of the sidewall of the transition piece 48. However, the flat tube 320 may not be fixed to the ribs 372 and, when the sidewall of the transition piece 48 vibrates or tends to elongate/shrink due to operation of the burners 50, the relative displacement/deformation of the base flange 370 with respect to the flat tube 320 can be accommodated by elastic/plastic deformation of the flat tube 320 without fracture of the flat tube 320.
The fuel is supplied to the flat tube 320 at outward end 330 of the spiral shape and flows toward inward end 310 of the spiral shape, as further described below in reference to FIG. 17.
FIG. 15 shows a cross section taken along a diameter of the aperture 80 of the sidewall of the transition piece 48. As shown in FIGS. 14 and 15, the flat tube 320 gradually changes its position toward the inside of the transition piece 48 and enters into the aperture 80 of the sidewall. Accordingly, the compressed air 10 that flows from the interior of the combustor plenum 40 is guided into the aperture 80 through the second-stage fuel injector 300 while being swirled without using vaned swirler. The swirl of the flow of the compressed air 10 may enhance mixture of the compressed air 10 and the fuel supplied through the flat tube 320. Further, as shown in FIGS. 14 and 15, the transverse direction DW of the flat tube 320 at the aperture 80 of the sidewall of the transition piece 48 is perpendicular to the sidewall of the transition piece 48. With this construction, the compressed air 10 with the fuel injected from the fuel hole 340 of the flat tube 320 may have a momentum perpendicular to the direction of the flow of the combustion products in the transition piece 48 and mixing of the compressed air 10 through the second-stage fuel injector 300 with the combustion products from the burners 50 may be enhanced.
As shown in FIG. 16A, in one or more embodiments, the second-stage fuel injector 300 may include cover 380 that covers the center portion of the spiral shape of the flat tube 320 and reduces backflow of the compressed air 10 and/or the combustion products from the inside space of the transition piece 48.
In one or more embodiments, as shown in FIG. 16B, the second-stage fuel injector 300 may include hood 385 that is attached to the base flange 370 and completely covers the flat tube 320 and the aperture 80 of the sidewall of the transition piece 48. The shape of the hood 385 may be configured such that the contour of the hood 385 is aligned with the flow of the compressed air 10 outside of the combustor 4. Accordingly, the flow of the compressed air 10 may not be disturbed by the hood 385 and pressure loss of the compressed air 10 at intake at the second-stage fuel injector 300 may be minimized.
FIG. 17 shows a schematic top view of the flat tube 320 of the second-stage fuel injector 300. As shown in FIG. 17, the flat tube 320 has a spiral shape when viewed in the direction of the flow of the compressed air 10 at the aperture 80 (or in the direction perpendicular to the sidewall of the transition piece 48). The spiral shape may be combinations of various circular arcs with different radii. Otherwise, the spiral shape may be an Archimedean spiral that can be described as a locus satisfying r=a+b×θ where r and θ are cylindrical coordinates of the locus and a and b are constants. It should be noted that the spiral shape described above may designate the center of the flat tube 320 in the thickness direction DT, or either side of the flat tube 320 (facing toward or away the center of the aperture 80).
As shown in FIG. 17, the direction of the spiral shape is oriented (i.e., spiraling out in the clockwise or counterclockwise direction) such that the spiral shape opens at the outward end 330 to receive the flow of the compressed air 10. With this construction, the compressed air is smoothly guided into a flow path of the spiral shape formed between adjacent turns of the flat tube 320.
Further shown in FIG. 17 with small open arrows are approximate locations of the fuel holes 340 and directions of the fuel flow that exits the flat tubes 320 into the flow of the compressed air 10. In one or more embodiments, the fuel holes 340 may be disposed on the side of the flat tube 320, similar to the fuel hole 240 shown in FIGS. 4 and 5. Further, one additional fuel hole 340 may be disposed at the inward end 310 of the spiral shape, as shown in FIG. 17. The fuel holes 340 may be equally spaced along the longitudinal direction DL of the flat tube 320, or may be distributed otherwise. Further, all of the directions of the exiting fuel from the flat tube 320 may be aligned toward the center of the aperture 80 when viewed along the direction of the flow of the compressed air 10 at the aperture 80, as shown in FIG. 17. However, the directions may be aligned away from the center of the aperture 80. Further, the directions may not be aligned in certain orientations and, for example, may alternate between toward and away from the center of the aperture 80. Furthermore, the locations of the fuel holes 340 and the directions in which the fuel exits may appear random.
FIG. 18 shows a schematic view of the flat tube 320 when unwrapped flat from the spiral shape. As shown in FIG. 18, in one or more embodiments, the thickness of the flat tube 320 may be constant over the longitudinal direction DL of the flat tube 320 from the outward end 330 to the inward end 310. On the other hand, width W in the transverse direction DW may change at different longitudinal locations of the flat tube 320. In one or more embodiments, the width W may linearly decrease from W1 at the outward end 330 to W2 at the inward end 310, as shown in FIG. 18. In the construction of the flat tube 320 shown in FIGS. 14 and 17, the fuel inside the flat tube 320 flows from the outward end 330 to the inward end 310 while portions of the fuel flow out into the compressed air 10 at the fuel holes 340 therebetween. Accordingly, with this construction of the linearly reducing the width W, pressure of the fuel inside the flat tube 320 may be adjusted substantially constant along the longitudinal direction DL of the flat tube 320 and the amounts of the fuel exiting at the respective fuel holes 340 may be properly regulated.
Further, as shown in FIG. 18, the flat tube 320 according to one or more embodiments may change its position D in the transverse direction DW along the longitudinal direction DL such that the flat tube 320 changes its position toward the inside of the transition piece 48, as shown in FIGS. 14 and 15. The position D may be linear along the longitudinal direction DL, as shown in FIG. 18.
The profile of the position D along the longitudinal direction DL changes how the flat tube 320 is disposed when the flat tube 320 is coiled into the spiral shape. In one or more embodiments, the profile of the position D may be determined such that the depth position (along the direction toward the inside of the transition piece 48) may be limited to yield the second-stage fuel injector 300 of a low aspect ratio (the ratio of the height of the second-stage fuel injector 300 in the direction perpendicular to the sidewall of the transition piece 48 to the length of the second-stage fuel injector 300 measured along the direction of the flow of the combustion products in the transition piece 48). The second-stage fuel injector 300 of a low aspect ratio may reduce the height of the second-stage fuel injector 300 that protrudes out in the direction perpendicular to the sidewall of the transition piece 48 and may yield a compact construction of the second-stage fuel injector 300, thereby alleviating implementation of the second-stage fuel injector 300 to existing gas turbine systems. Further, in one or more embodiments, the profile of the position D may be determined such that the flat tube 320 of adjacent curved sections when wrapped in the spiral shape may not overlap with each other and the second-stage fuel injector 300 may not block the flow of the compressed air 10 therethrough.
FIG. 19 shows another construction of second-stage fuel injector 400 according to one or more embodiments.
In this construction, flat tubes 420, 422, 424 have substantially the same fundamental construction as the flat tube 220 described in reference to FIGS. 4-12. However, in this construction, both ends in the longitudinal direction DL of each of the flat tubes 420, 422, 424 are connected with each other and the flat tubes 420, 422, 424 are in three different loops. Although the exemplary construction shown in FIG. 19 includes three loops of the flat tubes 420, 422, 424, the number of loops of the flat tubes is not limited to three.
Further, as shown in FIG. 19, the flat tubes 420, 422, 424 that are looped have curved profiles along the direction of the flow of the compressed air 10 and form conduits to the compressed air 10 through the second-stage fuel injector 400. More specifically, each of the flat tubes 420, 422, 424 forms a bell mouth such that flow paths between two adjacent ones of the flat tubes 420, 422, 424 have larger flow path areas at their upstream ends than at their downstream ends with respect to the flow of the compressed air 10.
Further, as shown in FIG. 19, the loop of the flat tube 422 is inside the loop of the flat tube 420 and the loop of the flat tube 424 is inside the loop of the flat tube 422 when viewed in the direction perpendicular to the sidewall of the transition piece 48. This construction may be more clearly viewed in FIG. 20 that shows a top view (the view in the direction perpendicular to the sidewall of the transition piece 48) of the second-stage fuel injector 400 according to one or more embodiments.
As shown in FIG. 19, the flat tubes 420, 422, 424 are connected with struts 490, 492, 494. The cross sections of the struts 490, 492, 494 are streamlined in the direction from a periphery of the bell mouth toward the center of the bell mouth (i.e., in the direction of the flow of the compressed air 10) and minimize pressure loss of the compressed air 10 that flows through the second-stage fuel injector 400. Although three struts 490, 492, 494 are shown in FIG. 19, the number of the struts are not limited to three. Further, although each of the three struts 490, 492, 494 connects the flat tube 424 to the flat tube 422 and connects the flat tube 422 to the flat tube 420 in the embodiments shown in FIG. 19, some struts may connect only the flat tube 420 and the flat tube 422 and other struts may connect only the flat tube 422 and the flat tube 424 at different locations along the longitudinal direction DL of the flat tubes 420, 422, 424.
In the embodiments shown in FIG. 19, at least one of the struts 490, 492, 494 is hollow and has space inside through which the interiors of the flat tubes 420, 422, 424 communicate with each other. Accordingly, whereas a fuel supply line (not shown in FIG. 19) may supply a fuel to the flat tube 420 that is disposed most outside among the loops, at least one of the struts 490, 492, 494 that has a hollow interior can provide a fuel from the flat tube 420 to the flat tube 422. Similarly, the flat tube 424 that is disposed most inside among the loops may be provided with the fuel from the flat tube 422 through a hollow interior of at least one of the struts 490, 492, 494.
As shown in FIGS. 19 and 20, each of the loops of the flat tubes 420, 422, 424 has a substantially wedge-like shape when viewed in the direction perpendicular to the sidewall of the transition piece 48. The wedge-like shape of each of the loops of the flat tubes 420, 422, 424 changes its size from the upstream end with respect to the flow of the compressed air 10 toward the downstream end to form the bell mouth described above. Further, the size of the wedge-like shape of the loop of the flat tube 422 is smaller than that of the loop of the flat tube 420 and larger than that of the loop of the flat tube 424 such that the flat tube 422 is disposed between the flat tube 420 and the flat tube 424.
As shown in FIGS. 19, the flat tube 420 disposed most outside may have a downstream edge directly attached to the sidewall of the transition piece 48. Accordingly, the compressed air flow only inside the bell mouth of the flat tube 420. In consequence, the flat tube 420 may have fuel holes (not shown in the drawings) only on an inner side of the flat tube 420 toward the center of the loop. To the contrary, because the compressed air 10 can flow on both inner and outer sides of the flat tubes 422, 424, the flat tubes 422, 424 may have fuel holes (not shown in the drawings) on either or both sides of the flat tubes 422, 424.
Further, as shown in FIG. 21 that shows a cross section of the second-stage fuel injector 400 taken along a longitudinal axis of the wedge-like shape (as designated cut-line G-G in FIG. 20), the downstream edge of the flat tube 420 may be attached to the circumference of aperture 480 on the sidewall of the transition piece 48. Accordingly, the aperture 480 on the sidewall of the transition piece 48 may also have a wedge-like shape. Apex (or rounded apex) 482 of the wedge-like shape of the aperture 480 is a rounded corner that forms an acute angle and may be aligned with apex (or rounded apex) 421 of the downstream edge of the flat tube 420. In other words, in one or more embodiments, the downstream edge of the flat tube 420 with respect to the flow of the compressed air 10 has a wedge-like shape elongated in a direction pointed by the apex 421 and the aperture 480 on the sidewall of the transition piece 48 has a wedge-like shape that matches the downstream edge of the flat tube 420. Further, the aperture 480 is oriented such that the apex 482 of the acute angle points toward upstream of the flow of the combustion products in the transition piece 48 (or approximately toward the burners 50).
Further, FIG. 21 shows the inside spaces of the flat tubes 420, 422, 424 communicate with each other via the inside space of the strut 490.
At the downstream edges of the flat tubes 420, 422, 424, the transverse directions DW of the flat tubes 420, 422, 424 are substantially perpendicular to the sidewall of the transition piece 48. This construction alleviates penetration of the flow of the compressed air 10 that exits the second-stage fuel injector 400 into the flow of the combustion products and improves mixture of the compressed air 10 through the second-stage fuel injector 400 with the combustion products from the burner 50. To the contrary, expanded shapes of the bell mouths of the upstream edges of the flat tubes 420, 422, 424 cause less disturbance of the flow of the compressed air 10 outside the transition piece 48 and guides the compressed air into the second-stage fuel injector 400. Accordingly, the expanded shapes of the bell mouths reduce pressure loss of the compressed air 10 caused by the second-stage fuel injector 400.
Further, the downstream edges of the flat tubes 420, 422, 424 may terminate at different distances from the aperture 480 of the sidewall of the transition piece 48, as in FIG. 21. Alternatively, the downstream edges of the flat tube 422, 424 may terminate at the same distance (that is, zero) from the aperture 480 similar to the downstream edge of the flat tube 420. Further, the downstream edges of the flat tubes 422, 424 may protrude into the inside space of the transition piece 48 through the aperture 480.
As shown in FIG. 21, the downstream edges of the flat tubes 422, 424 are not attached to the sidewall of the transition piece 48 and are disposed within the aperture 480 when viewed perpendicular to the sidewall of the transition piece 48. Accordingly, although not shown in FIG. 21, the flat tubes 422, 424 may be equipped with co-axial tubes that are similar to the co-axial tube 250 of the flat tube 220. When the flat tubes 422, 424 are equipped with respective co-axial tubes, at least one of the struts 490, 492, 494 may have a co-axial tube that supplies fluids to the co-axial tubes of the flat tubes 422, 424.
FIG. 22 shows an exemplary distribution of fuel holes of the flat tubes 420, 422, 424 in a schematic top view of the second-stage fuel injector 400 according to one or more embodiments. As shown in FIG. 22, the fuel holes may be distributed to have a uniform areal density of the fuel holes over the side surfaces of the flat tubes 420, 422, 424. Alternatively, locations of the fuel holes may be adjusted to yield a uniform fuel density in the compressed air 10 that flows through the second-stage fuel injector 400.
FIG. 23 shows another construction of second-stage fuel injector 500 according to one or more embodiments. Similar to the second-stage fuel injector 400 shown in FIG. 19, three flat tubes 520, 522, 524 are in the shapes of three different loops and four struts 590, 592, 594, 596 connect the three flat tubes 520, 522, 524.
However, in the second-stage fuel injector 500, the loops are in diamond-like shapes elongated in one direction. The downstream edge of the flat tube 520 that is disposed most outside among the loops is attached to the circumference of aperture 580 on the sidewall of the transition piece 48. Therefore, in the second-stage fuel injector 500, the aperture 580 is also in a diamond-like shape, as shown in FIG. 23, with apex (or rounded apex) 582 that has an acute angle. The aperture 580 is oriented such that the apex 582 of the acute angle points toward upstream of the flow of the combustion products in the transition piece 48 (or approximately toward the burners 50).
Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims.
Patent Application
20240288170
