Fuel lance cooling for a gas turbine with sequential combustion

Abstract

A fuel lance is disclosed for injecting a gaseous and/or liquid fuel mixed with air into an axial hot gas flow flowing through a sequential combustor of a gas turbine, the fuel lance having at least one finger extending in a longitudinal direction into the axial hot gas flow of the gas turbine essentially perpendicular to the hot gas flow. The finger is configured as a streamlined body which has a streamlined cross-sectional profile. The body has two lateral surfaces essentially parallel to the axial hot gas flow. The body includes an enclosing outer wall having a longitudinally extending air plenum for the distributed introduction of air into the at least one finger. The air plenum is provided with a plurality of distributed impingement cooling holes, such that air exiting through the impingement cooling holes impinges on the inner side of the leading edge region of the body.

Claims

1. A fuel lance for injecting a gaseous and/or a liquid fuel and air into an axial hot gas flow flowing through a sequential combustor of a gas turbine, said fuel lance comprising: at least one finger extending into said axial hot gas flow in a longitudinal direction that is perpendicular to said axial hot gas flow, wherein said at least one finger is configured as a streamlined body which has a streamlined cross-sectional profile, wherein said streamlined body has two lateral surfaces arranged to be parallel to said axial hot gas flow, joined at their upstream side by a leading edge and joined at their downstream side forming a trailing edge, wherein a plurality of nozzles are distributed along said trailing edge, wherein means for impacting a mixing quality and reducing pressure loss in said sequential combustor are provided at a region around the trailing edge of said streamlined body, wherein said streamlined body includes an enclosing outer wall defining said streamlined cross-sectional profile, wherein within said enclosing outer wall there is provided a longitudinally extending air plenum for a distributed introduction of the air into said at least one finger, said longitudinally extending air plenum having a first distance from said enclosing outer wall, defining a first interspace, wherein said longitudinally extending air plenum is provided with a plurality of distributed impingement cooling holes, such that the air exiting through said plurality of distributed impingement cooling holes impinges on an inner side of the enclosing outer wall at a region around the leading edge of said streamlined body, wherein the air is mixed with the gaseous and/or the liquid fuel after exiting through the plurality of distributed impingement cooling holes, wherein said plurality of distributed impingement cooling holes each have a hole diameter between 1.2 mm and 1.8 mm, and said plurality of distributed impingement cooling holes are arranged at said longitudinally extending air plenum with a first pitch ratio, the first pitch ratio being a distance between two holes of said plurality of distributed impingement cooling holes and the hole diameter of any one of the two holes and being between 3 and 10, wherein a height of the first interspace between said longitudinally extending air plenum and said enclosing outer wall perpendicular to said enclosing outer wall increases beginning from said leading edge towards said trailing edge of said streamlined body, wherein within said enclosing outer wall there is provided a longitudinally extending gas plenum for a distributed introduction of the gaseous fuel into said at least one finger, said longitudinally extending gas plenum being arranged in a middle between said leading edge and said trailing edge with a second distance from said enclosing outer wall, defining a second interspace, wherein a plurality of distributed pin fins are arranged on the inner side of said enclosing outer wall of said streamlined body at a region around said longitudinally extending gas plenum for convective cooling of said enclosing outer wall by the air flowing from said longitudinally extending air plenum to said region around the trailing edge through said second interspace between said longitudinally extending gas plenum and said enclosing outer wall, wherein the plurality of distributed pin fins are entirely downstream of said first interspace with respect to the air flowing from said longitudinally extending air plenum to said region around the trailing edge.

2. The fuel lance according to claim 1, wherein said plurality of distributed pin fins have a height perpendicular to said enclosing outer wall between 1.5 mm and 2.5 mm, and said plurality of distributed pin fins have a second pitch ratio, the second pitch ratio being a ratio of distance between two pin fins of the plurality of distributed pin fins and a diameter of one of the two pin fins, and being between 3 and 5.

3. The fuel lance according to claim 2, wherein said plurality of distributed pin fins are cylindrical or tapered or hoof-shaped or teardrop shaped.

4. The fuel lance according to claim 2, wherein a plurality of distributed effusion cooling holes are provided in said enclosing outer wall at the region around the trailing edge, through which the air from said longitudinally extending air plenum exits said streamlined body after having convectively cooled said enclosing outer wall in said second interspace.

5. The fuel lance according to claim 1, wherein said means for impacting the mixing quality and reducing the pressure loss in said sequential combustor comprises: a plurality of vortex generators arranged on said streamlined body on both sides at the region around the trailing edge.

6. Fuel lance according to claim 1, wherein said means for impacting the mixing quality and reducing the pressure loss in said sequential combustor comprises: lobes being arranged between said nozzles at the trailing edge of said streamlined body.

7. The fuel lance according to claim 1, wherein said fuel lance is configured for a rectangular burner.

8. Fuel lance according to claim 1, wherein said fuel lance is configured for a center-body burner.

9. The fuel lance according to claim 1, wherein increasing the height of the first interspace allows a reduction of cross flow velocity and an enhancement of impingement cooling efficiency downstream.

10. The fuel lance according to claim 5, wherein each vortex generator of said plurality of vortex generators comprises: a leading panel, and guiding ribs to guide an air flow closer to said leading panel.

11. The fuel lance according to claim 10, comprising: a flow separator in a longitudinal middle of said longitudinally extending air plenum to separate said air flowing from both ends of the longitudinally extending air plenum and to avoid instabilities.

12. The fuel lance according to claim 1, wherein a bypass is provided at said longitudinally extending air plenum through which bypass air flows from said longitudinally extending air plenum into said second interspace.

13. The fuel lance according to claim 1, wherein release holes are provided in the enclosing outer wall at a downstream end of said longitudinally extending gas plenum to avoid a dead air flow corner behind said longitudinally extending gas plenum.

14. The fuel lance according to claim 5, wherein said vortex generators are made of a ceramic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is now to be explained more closely by means of different embodiments and with reference to the attached drawings.

(2) FIG. 1 shows in a perspective view an exemplary gas turbine with sequential combustion of the type GT26;

(3) FIG. 2 shows in a perspective view a vortex generator (VG) lance for a rectangular burner according to an embodiment of the invention;

(4) FIG. 3 shows in an axial view a VG lance for a center-body burner according to an embodiment of the invention;

(5) FIG. 4 shows in a perspective view similar to FIG. 2 a lobe lance for a rectangular burner according to an embodiment of the invention;

(6) FIG. 5 shows in an axial view similar to FIG. 3 a lobe lance for a center-body burner according to an embodiment of the invention;

(7) FIG. 6 shows a vertical section through a finger of a center-body lobe lance according to an embodiment of the invention;

(8) FIG. 7 shows a horizontal section through the finger of FIG. 6;

(9) FIG. 8 shows in a perspective view the rectangular VG lance of FIG. 2 with one finger being vertically sectioned;

(10) FIG. 9 shows in detail the sectioned finger of FIG. 8;

(11) FIG. 10 shows a detail of a vortex generator of the VG lance with additional ribs according to another embodiment of the invention;

(12) FIG. 11a, FIG. 11b show the possibility of feeding air to the air plenum from both sides (FIG. 11a) and separating the flows be means of a flow separator according to another embodiment of the invention (FIG. 11b);

(13) FIG. 12 shows additional oblique ribs for enhanced convection cooling in the gas plenum region of the lance according to another embodiment of the invention;

(14) FIG. 13 shows additional lateral ribs for enhanced convection cooling in the gas plenum region of the lance according to another embodiment of the invention;

(15) FIG. 14 shows in a horizontal section of a VG lance the possibility of bypassing air from the air plenum according to another embodiment of the invention; and

(16) FIG. 15 shows the provision of additional release holes at the downstream corner of the gas plenum according to another embodiment of the invention.

DETAILED DESCRIPTION OF DIFFERENT EMBODIMENTS OF THE INVENTION

(17) The constant pressure sequential combustion consists of two combustors (see FIG. 1 of the gas turbine GT26). Implementation of the sequential combustors improves combustion performance and operation flexibility.

(18) However, there are still problems to improve series cooling systems in sequential burners with impingement cooling, convective cooling and effusion cooling for a complicated structure with fuel gas and fuel oil plenum included. It is thus a desire to achieve optimized cooling, good mixing with hot gas flow and a required lifetime with minimal cooling air for lances used in these burners.

(19) A VG lance concept was already developed to improve the mixing quality and reduce the SEV pressure loss and further adapted to a VG lance development for a rectangular burner and for a center-body burner. The same was done for a lobe lance for a rectangular burner and for a center-body burner.

(20) According to the present invention the internal structure and cooling system of these lances are improved as explained below.

(21) FIG. 2 and FIG. 3 show VG lances 21 and 32 for rectangular burner (FIG. 2) and a center-body burner (FIG. 3). VG lance 21 of FIG. 2 comprises four separate fingers 22 extending in parallel between an upper plate 25 and a lower plate 26. Each finger 22 is configured as a streamlined body which has a streamlined cross-sectional profile (like an airfoil). The body has two lateral surfaces essentially parallel to an axial hot gas flow, which passes through the lance between upper and lower plates 25, 26. The lateral surfaces are joined at their upstream side by a leading edge 23 and joined at their downstream side forming a trailing edge 24.

(22) A plurality of fuel nozzles 27 for injecting a gaseous and/or liquid fuel and air is distributed along the trailing edge 24. Means for improving the mixing quality and reducing pressure loss in said sequential combustor are provided in the trailing edge region of said body in form of a plurality of vortex generators 28 arranged on the streamlined body on both sides at the trailing edge region.

(23) The streamlined body comprises an enclosing outer wall 75 defining its streamlined cross-sectional profile. Within the outer wall 75 a longitudinally extending air plenum 31 is provided having a distance from outer wall 75, defining a first interspace, for the distributed introduction of air into each finger 22 (see FIG. 8). There is also provided a longitudinally extending gas plenum 30 for the distributed introduction of gaseous fuel into each finger 22. Gas plenum 30 is arranged in the middle between leading edge 23 and trailing edge 24 with a distance from outer wall 75, defining a second interspace for the delivery of air from air plenum 31 to leading edge 23. Liquid fuel (oil) can be introduced by liquid fuel supply 29.

(24) A similar internal structure exists for center-body VG lance 32 of FIG. 3 with its radial fingers 35 extending between an outer ring 33 and a center-body 34, each finger being equipped with nozzles 36 and vortex generators 37.

(25) The cooling air introduced through the air plenum 31 is guided through the lances 21, 32, first cools the leading edge 23 of the VG lances 21, 32 with impingement cooling and reduces heat load with TBC coating (or without TBC coating), and then cools the trailing edge 24 of the VG lances 21, 32 by using convective cooling with internal pins (67 in FIG. 7), and finally is discharged into the hot gas flow through slots between the fuel nozzles 36 and fuel nozzles 27 (as carrier air) and locally discharged to establish effusion cooling.

(26) A similar situation is given for the lobe lances 38 and 49 of FIG. 4 and FIG. 5 to be used with a rectangular burner (FIG. 4) and a center-body burner (FIG. 5). Lobe lance 38 of FIG. 4 comprises four separate fingers 39 extending in parallel between an upper plate 42 and a lower plate 43. Each finger 39 is configured as a streamlined body which has a streamlined cross-sectional profile (like an airfoil).

(27) The body has two lateral surfaces essentially parallel to an axial hot gas flow, which passes through the lance between upper and lower plates 42, 43. The lateral surfaces are joined at their upstream side by a leading edge 40 and joined at their downstream side forming a trailing edge 41.

(28) A plurality of fuel nozzles 44 for injecting a gaseous and/or liquid fuel and air are distributed along the trailing edge 41. Means for improving the mixing quality and reducing pressure loss in said sequential combustor are provided in the trailing edge region of said body in form of lobes 45 running between the fuel nozzles 44 at the trailing edge 41.

(29) The streamlined body comprises an enclosing outer wall defining its streamlined cross-sectional profile. Within the outer wall a longitudinally extending air plenum 48 is provided having a distance from outer wall, defining a first interspace, for the distributed introduction of air into each finger 39 (see finger 52 in FIGS. 6 and 7).

(30) There is also provided a longitudinally extending gas plenum 47 for the distributed introduction of gaseous fuel into each finger 39. Gas plenum 47 is arranged in the middle between leading edge 40 and trailing edge 41 with a distance from outer wall, defining a second interspace for the delivery of air from air plenum 48 to leading edge 40. Liquid fuel (oil) can be introduced by liquid fuel supply 46.

(31) A similar internal structure exists for center-body lobe lance 49 of FIG. 5 with its radial fingers 52 extending between an outer ring 50 and a center-body 51, each finger being equipped with nozzles 53 and lobes 54 between nozzles 53.

(32) Details of a lobe lance finger 52 for a center-body burner are shown in FIGS. 6 and 7. Finger 52 extends between an inner plate 64 and an outer plate 65 an comprises an air plenum 55 and a gas plenum 56, which are enclosed by outer wall 75 with leading edge 61 and trailing edge 61.

(33) The cooling air introduced through the air plenum 55 is guided in longitudinal direction through finger 52, first cools the leading edge 61 of the body by means of impingement cooling 58 and reduces heat load with TBC coating (or without TBC coating), and then cools the downstream parts of the body by means of convective cooling 59 with internal pins 67 arranged on the inner side of outer wall 75, and finally is discharged into the hot gas flow through slots between the fuel nozzles 53 and between the fuel nozzles 44 (as carrier air).

(34) Characteristic features of the new and improved cooling scheme of the VG lances shown in FIG. 2, FIG. 3 and FIG. 8, FIG. 9 are the following: A series cooling system for a fuel injection lance (including fuel gas plenum 30 and fuel oil plenum 29). Leading edge 23 is impingement cooled with impingement cooling holes 66 (FIG. 9): The impingement cooling hole diameter is in the range 1.2 to 1.8 mm, the pitch ratio (ratio of distance between hoes/hole diameter) is in the range 3 to 10. The mid body and trailing edge 24 is convectively cooled with pin fins 67 (FIG. 14): pin fin height is in the range 1.5 to 2.5 mm, pitch ratio is in the range 3 to 5 (ratio of distance between pin fins/pin fin diameter). Pin fins 67 can be cylindrical, tapered, hoof shaped, or tear dropped. The region, where the vortex generators 28 are arranged, is effusion cooled. Effusion cooling hole diameter is in the region 0.7 to 1.2 mm, pattern of effusion cooling holes 68 (FIG. 8) has a ratio of distance to hole diameter in the range 4 to 15. The cooling flows are finally discharged through slots between fuel nozzles 36, and fuel nozzles 27 (function as carrier air) and the effusion cooling.

(35) The VG lance cooling can be further improved by: The impingement cooling channel height (height of interspace between air plenum 31 and outer wall 75) can vary axially (not necessarily constant height) and especially in downstream direction to optimize the cross cooling flows As shown in FIGS. 12 and 13 vortex generators, straight ribs, V-shaped or W-shaped ribs 71 (FIG. 12) can be applied on the mid body and the trailing edge of the cooling channels to improve the cooling situation there instead of pins Axially directional ribs or flow splitter 72 (FIG. 13) can be applied on mid body and trailing edge to optimize cooling flows Film cooling holes or effusion cooling holes can additionally be applied on some hot spots As shown in FIG. 14, the cooling air can be bypassed as bypass air 74 from air plenum 31 to the mid body without passing through the impingement cooling holes 66. This helps to optimize the cooling between leading edge 23 and trailing edge 24 and optimize the back flow margin which is required by the effusion cooling flows Vortex generators 28 can be replaced with ceramics, and therefore the cooling of vortex generators 28 is not required anymore

(36) For the lobe lances shown in FIG. 4, 5 and FIG. 6, 7 the situation is similar: A series cooling system for a fuel injection lance (including fuel gas plenum 47 and fuel oil plenum 46) Leading edge 40 is impingement cooled: impingement cooling hole diameter is in rage 1.2 to 1.8 mm, pitch ratio (ratio of distance between holes/hole diameter) is in range 3 to 10 The mid body and trailing edge 41 is convectively cooled with pin fins 67: pin fin height is in range 1.5 to 2.5 mm, pitch ratio is in range 3 to 5 (ratio of distance between pin fins/pin fin diameter) Pin fins 67 can be cylindrical, tapered, hoof shaped, or tear dropped The cooling flows are finally discharged through slot between fuel nozzles 53, and between fuel nozzles 44 (function as carrier air) and locally effusion cooling if needed for hot spot.

(37) The lobe lance cooling can be further improved: The impingement cooling channel height can vary axially (not necessarily constant height), especially increase in downstream direction, to optimize the cross cooling flows Vortex generators, Straight ribs, V shaped or W shaped ribs (71 in FIG. 12) can be applied on the mid body and the trailing edge 41 of the cooling channels to improve the cooling situation there instead of pins Axially directional ribs or flow splitters (72 in FIG. 13) can be applied on mid body and trailing edge 41 to optimize cooling flows Film cooling holes or effusion cooling holes can be applied on some hot spots As shown in FIG. 14, the cooling air can be bypassed as bypass air 74 from air plenum 48 to the mid body without passing through the impingement cooling holes 66. This helps to optimize the cooling between leading edge 40 and trailing edge 41 and optimize the back flow margin which is required by the effusion cooling flows

(38) Other possible improvements are the following: As shown in FIG. 10, guiding ribs 70a, 70b may be provided at each vortex generator 28 to guide air flow closer to the leading panel 69 of vortex generator 28, as the leading panel can not be well cooled due to very low hot gas back flow margin (BfM) without such guiding ribs 70a, 70b As shown in FIG. 11, the air plenum 31 is fed with air form both ends (see also FIG. 9). As collision of two counter air flows can cause an instability, a flow separator 76 may be provided at the longitudinal middle of the air plenum to avoid these counterflows As shown in FIG. 15, additional release holes 73 are provided between vortex generators 28 and nozzles 27 to destroy the dead air flow corner behind the fuel gas plenum 30 and increase the cooling velocity of this area for better cooling; these release holes 73 work as film cooling holes as well

LIST OF REFERENCE NUMERALS

(39) 10 gas turbine (GT, e.g. GT26) 11 rotor 12 casing 13 air inlet 14 compressor 15 combustor (annular, e.g. EV) 16 high pressure (HT) turbine 17 combustor (annular, sequential, e.g. SEV) 18 low pressure (LP) turbine 19 exhaust gas outlet 20 machine axis 21 lance (vortex generator VG; rectangular burner) 22,39 finger 23,40 leading edge 24,41 trailing edge 25,42 upper plate 26,43 lower plate 27,44 nozzle 28,37 vortex generator (VG) 29,46 liquid fuel supply (fuel oil plenum) 30,47,56 gas plenum 31,48,55 air plenum 32 lance (VG; center-body burner) 33,50 outer ring 34,51 center-body 35,52 finger 36,53 nozzle 38 lance (lobe) 45,54 lobe 49 lance (lobe; center-body burner) 57 liquid fuel supply 58 impingement cooling 59 convective cooling 60 effusion cooling 61 leading edge 62 trailing edge 64 inner plate 65 outer plate 66 impingement cooling hole 67 pin fin 68 effusion cooling hole 69 leading panel (VG) 70a, 70b guiding rib 71,72 rib 73 release hole 74 bypass air 75 outer wall 76 flow separator