Combustion chamber cap arrangement

Abstract

Support structure of a burner tube (66) in a combustion chamber cap assembly (62) of a gas turbine combustion chamber, comprising: an outer circular ring (44); an inner annular hub (46); a plurality of struts (48) extending radially between the outer annular ring (44) and the inner annular hub (46), one end of each strut (48) being attached directly to an outer surface of the inner annular hub (46) and an inner surface of the inner annular hub (46) being adapted to receive the burner tube (66); an annular piston ring groove (54) formed in the inner surface of the inner annular hub (46); and a piston ring (60) received in the piston ring groove (54) and adapted to receive and seal an inner end of the burner tube (66), the piston ring (60) being disposed radially immediately between the inner annular hub (46) and the burner tube (66).

Description

BACKGROUND TO THE INVENTION

[0001] The invention relates to the field of gas turbine combustion technology and more particularly to a simplified design for a combustor cap assembly.

[0002] In certain annular tube combustors of ground-based electric power gas turbines, combustor cap assemblies are provided at the forward or upstream end of the combustor assembly to support fuel nozzles extending into the combustion chamber. Typically, the combustor cap assemblies support multiple fuel nozzles at two locations: the forward ends at the nozzles and the rear ends of the nozzles and / or the burner tubes surrounding the nozzles. In some designs, only a central fuel nozzle is surrounded by a burner tube, whereas in other designs, all of the combustor nozzles are surrounded by corresponding burner tubes.

[0003] In certain known combustor cap assembly arrangements, at the aft end where the cap assembly (i.e., the end closest to the combustion chamber) abuts aft ends of the fuel nozzles and / or burner tubes, there is an effusion plate formed with a plurality of openings, each surrounded by a piston ring sleeve that telescopically receives the aft end of the burner tube. Usually, the piston ring sleeve, as a component of the cap assembly, is butt-welded to the effusion plate, and the burner tube is received over the piston sleeve with a sealing hoop radially therebetween. A support structure, comprising inner and outer rings connected by a plurality of spokes or struts, is disposed adjacent the effusion plate around the end piston ring sleeve and welded in place.The burner tube sleeve is welded to a support plate at the opposite or upstream end of the cap assembly by means of a fillet weld.

[0004] The conventional design is complicated and requires multiple parts, making assembly, repairs, and the like difficult.

[0005] US 5,274,991 A discloses a support structure for premix burner tubes in a combustor cap assembly of a gas turbine combustor, which support structure comprises an inner and an outer ring connected by a plurality of spokes or struts, and which is arranged adjacent to an impingement plate. The impingement plate has a central opening and a plurality of openings surrounding the central opening. Each of the surrounding openings is formed by an axial ring welded to the impingement plate and is provided for receiving premix burner tubes. The central opening of the impingement plate has an annular sleeve welded thereto, which receives a center cup that closes the central opening.

[0006] US 2006 / 0 242 965 A1 discloses a combustion system with an outer metal casing, a fuel-air premixer within the outer metal casing, and a ceramic combustion chamber flame tube arranged radially between the fuel-air premixer and the outer metal casing. A metal support ring holds the ceramic combustion chamber flame tube radially and axially to the outer metal casing. A lower tube section of the fuel-air premixer, which passes through a central opening of the metal support ring and is received within an upper neck section of the ceramic combustion chamber flame tube, has a C-shaped channel on its outer surface into which a piston ring is inserted, sealing against an inner surface of the metal support ring.

[0007] US 2006 / 0 230 763 A1 discloses a combustion chamber with a cap assembly that accommodates a plurality of burner tubes in an annular arrangement, each of which surrounds a fuel nozzle and is housed in a sleeve. The sleeves have annular grooves formed in their inner surfaces that receive piston rings that seal around the burner tubes.

[0008] US 2009 / 0 188 255 A1 discloses a combustor cap assembly with a support structure including an outer annular ring, an inner annular hub, and a plurality of support struts extending radially between and integrally formed with the outer annular ring and the inner annular hub. An effusion plate is positioned adjacent to the support structure and includes an integral inner sleeve disposed within the inner annular hub of the support structure and receiving one end of a central burner tube.

[0009] There remains a need for a simplified design of a combustor cap assembly with a burner tube support structure that requires fewer parts and simplifies assembly or disassembly without compromising structural strength. SUMMARY OF THE INVENTION

[0010] According to a first aspect of the invention, there is provided a support structure for a combustor tube in a combustor cap assembly of a gas turbine combustor, comprising: an outer annular ring; an inner annular hub; a plurality of struts extending radially between the outer annular ring and the inner annular hub, one end of each strut being attached proximate an outer surface of the inner annular hub, and an inner surface of the inner annular hub being configured to receive the combustor tube; an annular piston ring groove formed in the inner surface of the inner annular hub; and a piston ring received in the piston ring groove and configured to receive and seal an inner end of the combustor tube, the piston ring being radially disposed proximate the inner annular hub and the combustor tube.

[0011] In another aspect, a combustor cap assembly is provided, including: a support structure for the combustor cap assembly at its forward and rear ends to support a plurality of fuel nozzles and surrounding combustor tubes, including a central fuel nozzle and a central combustor tube, the support structure including at the rear end an effusion plate having a central opening formed in part by a sleeve facing the forward end and a wagon wheel structure having an outer annular ring and an inner annular hub; a plurality of struts extending radially between the outer annular ring and the inner annular hub, the plurality of struts being attached proximate to the inner annular hub; a piston ring groove in a radially inner surface of the inner annular hub;and a piston ring received in the piston ring groove and configured to receive and seal an inner end of the burner tube, the piston ring being radially disposed immediately between the inner annular hub and the burner tube;

[0012] In yet another aspect, a combustor cap assembly is disclosed, including: a support structure for the combustor cap assembly at its forward and rear ends to support a plurality of fuel nozzles and surrounding combustor tubes, including a central fuel nozzle and a central combustor tube; the support structure including, at the rear end, an effusion plate having at least one circular opening formed in part by a sleeve facing the forward end and including a wagon wheel structure having an outer annular ring and an inner annular hub; and a plurality of struts extending radially between the outer annular ring and the inner annular hub; a piston ring groove in a radially inner surface of the inner annular hub;and a piston ring received in the piston ring groove and configured to receive and seal an inner end of the central burner tube, the piston ring being radially disposed immediately between the inner annular hub and the central burner tube; and wherein the at least one circular opening includes a central circular opening defined by an upstanding rim, and wherein the rear end of the inner annular hub is attached to the upstanding tapered rim.

[0013] The invention will now be described in detail in conjunction with the drawings shown below. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a cross-section through a combustion chamber cap assembly according to a known construction; Fig. Figure 2 shows a nozzle burner tube support structure used by the cap assembly of Fig. 1 has been removed; Fig. 3 shows a cut-off partial view of the Fig. 2 shown support structure; Fig. 4 shows a nozzle burner support structure according to an exemplary but non-limiting embodiment of the invention; Fig. Figure 5 shows a section of a nozzle burner tube support structure according to the invention and illustrates additional supports for surrounding nozzles; Fig. Figure 6 shows a partially cross-sectional view of a combustor cap assembly supporting the nozzle burner tube support structure of Fig. 4 used; and Fig. 7 shows a similar view to Fig. 6, which additionally illustrates a central nozzle incorporated in the jet burner tube. DETAILED DESCRIPTION OF THE INVENTION

[0014] Fig. Figure 1 illustrates a known combustor cap assembly 10 used to support a plurality of fuel nozzles (not shown) in an arrangement in which five outer nozzles surround a central nozzle. In this particular example, all of the nozzles are provided with surrounding or outer burner tubes supported on a rear end of the combustor cap assembly. Fig. 1, two outer nozzle burner tubes 12 and 14 are shown together with a central burner tube 16. The invention here relates in particular to the support for the central burner tube 16 at the inner or rear end 18 of the cap assembly 10. Accordingly, in the description of the Fig. 1, in particular the central burner tube 16 and its interaction with the inner or rear end 18 of the combustion chamber cap assembly.

[0015] At their inner or front ends (the ends facing or adjacent to the combustion chamber), the various burner tubes are supported by sleeves 20 welded to an effusion plate 22. The central sleeve 20 (also referred to here as the “piston sleeve”) is (as best shown in Fig. 2 and Fig. 3) is further supported laterally by a "wagon-wheel" structure 24 formed by an outer ring 26 and an inner ring or hub 28 connected by a plurality of (five in the illustrated example) radially extending spokes or struts 30. It will be understood that in this arrangement, the five surrounding nozzles / combustor tubes are each disposed within the space defined by a pair of adjacent struts 30.

[0016] With further reference to Fig. 2 and Fig. 3, the inner hub 28 fits over the piston sleeve 20, and the central burner tube 16 is telescoped over the piston sleeve such that the inner end 32 of the burner tube 16 is in close proximity to the outer rim 34 of the inner hub 28, with an axial gap therebetween. It should also be noted that a similar axial gap exists between the inner rim 36 of the inner hub 28 and the flanged base 38 of the piston sleeve 20. These gaps allow for thermal expansion during operation. In this known arrangement, an annular conventional spring or "sealing hoop" 40 is disposed radially between the inner end of the burner tube 16 and the piston sleeve 20 to minimize air leakage across the effusion plate.

[0017] Fig. 4 and Fig. 5 illustrate a simplified arrangement used to secure the inner end of a central burner tube 66 to the fuel nozzle assembly (see Fig. 7) according to an exemplary but non-limiting embodiment of the invention. An inner wagon wheel construction 42 of a central burner is based on an outer circular ring 44 and an inner ring or hub 46 with a plurality of spokes or struts 48 extending radially therebetween. In this case, however, the inner hub 46 is constructed in such a way that a separate piston sleeve and sealing ring can be omitted. In addition, the central burner tube 66 is attached to the front end of the nozzle assembly ( Fig. 7) and sealed only to the carriage wheel structure 42. In particular, the inner hub 46 has tapered front and rear ends 50, 52, respectively, and an inner periphery formed axially between the ends 50, 52 with an annular piston ring groove 54. As best shown in Fig. 5 and Fig. 6, a downwardly extending annular rim portion 53 of the rearward tapered end 52 may be butt-welded to a complementary rim 56 in the effusion plate 58. The forwardly tapered end 50 facilitates telescoping of the central fuel nozzle burner tube 66 into the inner hub 46, and a piston ring 60 inserted into the groove 54 seals the space between the fuel nozzle burner tube 66 and the inner hub 46.

[0018] Fig. 5 also shows surrounding burner tube support sleeves 61 of a different arrangement than in Fig. 1, but is not intended to limit in any way the burner tube support structure described above.

[0019] Fig. 6 and Fig. 7 show the carriage wheel support structure 42 incorporated into a combustion chamber cap assembly 62, and Fig. Figure 7 shows the same cap assembly 62 with a central nozzle 64 incorporated into and extending into the fuel nozzle burner tube 66.

[0020] The rear end of the fuel nozzle burner tube 66 is sealed to the piston ring 60, but is otherwise unattached where the burner tube is engaged by the effusion plate 58. This arrangement allows the fuel nozzle burner tube 66 to thermally expand at least axially relative to the inner hub 46 and the effusion plate while maintaining the seal to the piston ring 60.

[0021] This arrangement provides effective support for the inner end of the central burner tube using a fewer number of parts and a simple construction, without compromising structural integrity. While the invention is described herein in connection with a central burner tube nozzle, it may be used in any nozzle burner tube. For example, a support similar to the inner ring or hub 46 could be welded to the effusion plate at any location where a nozzle burner tube is to be supported.

[0022] While the invention has been described with reference to a preferred embodiment which is presently believed to be best carried out, it is to be understood that the invention is not to be limited to the embodiment described, but rather is intended to cover various modifications and equivalent arrangements which fall within the scope of the appended claims.

Claims

[1] Support structure of a burner tube (66) in a combustion chamber cap assembly (62) of a gas turbine combustion chamber, comprising: an outer circular ring (44); an inner annular hub (46); a plurality of struts (48) extending radially between the outer annular ring (44) and the inner annular hub (46), one end of each strut (48) being attached directly to an outer surface of the inner annular hub (46) and an inner surface of the inner annular hub (46) being adapted to receive the burner tube (66); an annular piston ring groove (54) formed in the inner surface of the inner annular hub (46); and a piston ring (60) received in the piston ring groove (54) and adapted to receive and seal an inner end of the burner tube (66), the piston ring (60) being disposed radially immediately between the inner annular hub (46) and the burner tube (66). [2] A support structure according to claim 1, wherein the inner annular hub (46) is formed with inverted tapered portions at its opposite front and rear ends (50, 52). [3] Support structure according to claim 2, wherein the piston ring groove (54) is formed axially between the opposite front and rear ends (50, 52). [4] A support structure according to claim 2 in conjunction with an effusion plate (58), wherein the effusion plate (58) has a circular opening defined by an upright tapered rim (56), and wherein the rear end of the inner annular hub (46) is welded to the upright tapered rim (56) on the effusion plate (58). [5] The support structure of claim 1, wherein the plurality of struts (48) includes five struts (48) and wherein the burner tube (66) includes a central nozzle burner tube (66). [6] The support structure of claim 4, wherein the circular opening in the effusion plate (58) is formed in a central portion of the effusion plate (58), with a plurality of openings surrounding the circular opening. [7] The support structure of claim 6, wherein each of the plurality of openings is formed with an upright ring retainer configured to receive a burner tube (66), each upright ring retainer having an inner piston ring groove (54) into which a piston ring (60) configured to engage the burner tube (66) is inserted. [8] Combustion chamber cap assembly (62), which includes: a support structure for the combustor cap assembly (62) at its forward and rear ends to support a plurality of fuel nozzles (64) and surrounding burner tubes (66), including a central fuel nozzle (64) and a central burner tube (66); wherein the support structure at the rear end includes an effusion plate (58) having a central opening formed in part by a sleeve facing the front end and by a wagon wheel structure having an outer annular ring (44) and an inner annular hub (46); a plurality of struts (48) extending radially between the outer annular ring (44) and the inner annular hub (46), the plurality of struts (48) being attached directly to the inner annular hub (46); a piston ring groove (54) in a radial inner surface of the inner annular hub (46); and a piston ring (60) received in the piston ring groove (54) and adapted to receive and seal an inner end of the burner tube (66), the piston ring (60) being disposed radially immediately between the inner annular hub (46) and the burner tube (66). [9] The combustion chamber cap assembly (62) of claim 8, wherein the inner annular hub (46) is formed with reversely tapered edges at its opposite front and rear ends (50, 52). [10] The combustion chamber cap assembly (62) of claim 9, wherein the piston ring groove (54) is formed axially between the opposite front and rear ends (50, 52). [11] The combustion chamber cap assembly (62) of claim 8, wherein the effusion plate (58) has a circular opening defined by an upright tapered rim (56), and wherein the rear end of the inner annular hub (46) is welded to the upright tapered rim (56) on the effusion plate (58). [12] The combustor cap assembly (62) of claim 8, wherein the plurality of struts (48) includes five struts and wherein the burner tube (66) includes a central nozzle burner tube (66). [13] The combustor cap assembly (62) of claim 11, wherein the circular opening in the effusion plate (58) is formed in a central portion of the effusion plate (58), the circular opening being surrounded by a plurality of openings. [14] Combustion chamber cap assembly (62) according to claim 8, wherein inner ends of the burner tubes (66) are supported and sealed in the inner annular hub (46) to allow thermal expansion in the axial direction. [15] Combustion chamber cap assembly (62) comprising: a support structure for the combustor cap assembly (62) at its forward and rear ends to support a plurality of fuel nozzles (64) and surrounding burner tubes (66), including a central fuel nozzle (64) and a central burner tube (66); wherein the support structure at the rear end includes: an effusion plate (58) having at least one circular opening formed in part by a sleeve facing the front end; and a wagon wheel structure (42) having an outer circular ring (44) and an inner annular hub (46); and with a plurality of struts (48) extending radially between the outer annular ring (44) and the inner annular hub (46); a piston ring groove (54) in a radial inner surface of the inner annular hub (46); and a piston ring (60) received in the piston ring groove (54) and adapted to receive and seal an inner end of the central burner tube (66), the piston ring (60) being disposed radially immediately between the inner annular hub (46) and the central burner tube (66); and wherein the at least one circular opening has a central circular opening defined by an upright tapered rim (56), and wherein the rear end of the inner annular hub (46) is attached to the upright tapered rim (56). [16] The combustor cap assembly (62) of claim 15, wherein the central circular opening is surrounded by a plurality of openings configured to receive other ones of the burner tubes (66) associated with other ones of the plurality of fuel nozzles (64). [17] The combustion chamber cap assembly of claim 16, wherein each of said plurality of circular openings is formed with an upright ring retainer configured to receive a corresponding one of said burner tubes (66), each upright ring retainer having an inner piston ring groove (54) into which a piston ring (60) configured to engage said corresponding one of said burner tubes (66) is seated. [18] The combustion chamber cap assembly (62) of claim 15, wherein the rear end of the inner annular hub (46) is welded to the upright tapered rim. [19] The combustor cap assembly (62) of claim 15, wherein a rear end of the central burner tube (66) is allowed to thermally expand relative to the inner hub (46) and the effusion plate (58). [20] The combustor cap assembly (62) of claim 15, wherein the rear ends of each of the burner tubes (66) are allowed to thermally expand relative to the effusion plate (58).

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