Patent Application
20140033717
The invention relates to gas turbine combustion technology and, more specifically, to a simplified design for combustor cap assembly.
In certain, can-annular combustor arrangements in land-based electrical power generation gas turbines, combustor cap assemblies are provided at the forward or upstream end of the combustor and serve to support fuel nozzles projecting into the combustion chamber. Typically, the combustor cap assemblies support plural fuel nozzles at two locations including the forward ends at the nozzles and the aft ends of the nozzles and/or burner tubes that surround the nozzles. In some configurations, only a center fuel nozzle is surrounded by a burner tube whereas in other configurations, all of the combustor nozzles are surrounded by respective burner tubes.
In certain known arrangements, the combustor cap assembly at the aft end where the cap assembly (i.e., the end closest to the combustion chamber) interfaces with the aft ends of the fuel nozzles and/or burner tubes, there is an effusion plate provided with plural apertures, each surrounded by piston ring sleeve that telescopically receives the aft end of the burner tube. Typically, the piston ring sleeve is butt-welded to the effusion plate as part of the cap assembly, and the burner tube is received over the piston sleeve, with a hula seal radially therebetween. A support structure which has inner and outer rings connected by plural spokes or struts, is positioned around the end piston ring sleeve adjacent the effusion plate and welded into place. The burner tube sleeve is fillet-welded to a backing plate at the opposite or upstream end of the cap assembly.
The current design is complex and requires multiple parts which can result in inefficiencies in assembly, repairs, etc. There remains a need, therefore, for a simplified combustor cap assembly design that reduces the number of parts and facilitates assembly/disassembly but without any degradation of structural integrity.
In accordance with an exemplary but nonlimiting embodiment, there is provided a support structure for a burner tube in a combustor cap assembly for a gas turbine combustor comprising an outer annular ring; an inner annular hub; and a plurality of struts extending radially between the outer annular ring and the inner hub; wherein the inner hub is provided with a piston ring groove and a piston ring adapted to receive and seal an inner end of the burner tube.
In another aspect, there is provided combustor cap assembly comprising a support structure cap assembly at forward and aft ends thereof for supporting a plurality of fuel nozzles and surrounding burner tubes, including a center nozzle and a center burner tube; the support structure at the aft end including a diffuser plate having a center opening defined in part by a sleeve facing the forward end and a wagon-wheel structure having an outer annular ring; and a plurality of struts extending radially between the outer annular ring and the inner hub; wherein the inner hub is provided with a piston ring groove and a piston ring adapted to receive and seal an inner end of the burner tube.
In still another aspect, there is provided a combustor cap assembly comprising support structure cap assembly at forward and aft ends thereof for supporting a plurality of fuel nozzles and surrounding burner tubes, including a center nozzle and a center burner tube; the support structure at the aft end including a diffuser plate having a center opening defined in part by a sleeve facing the forward end and a wagon-wheel structure having an outer annular ring; a plurality of struts extending radially between the outer annular ring and the inner hub; wherein the inner hub is provided with a piston ring groove and a piston ring adapted to receive and seal an inner end of the center burner tube; and an effusion plate having a circular center opening defined by an upstanding edge, and wherein said aft end of said inner hub is attached to said upstanding edge.
The invention will now be described in detail in connection with the drawings identified below.
At their inner or forward ends (the ends facing or adjacent the combustion chamber), the various burner tubes are supported by sleeves 20 welded to a diffuser plate 22. The center sleeve (also referred to herein as a “piston sleeve”) 20 is also laterally supported by a “wagon-wheel” structure 24 (best seen in
With continued reference to
The aft end of the fuel nozzle burner tube is sealed at the piston ring 60 but is otherwise unsecured where the burner tube is engaged by the effusion plate 58. This arrangement allows the fuel nozzle burner tube to grow thermally in at least an axial direction relative to the inner hub 46 and the effusion plate while the seal at the piston ring 60 is maintained.
This arrangement provides effective support for the inner end of the center burner tube with fewer parts and with simplicity of design at no sacrifice to structural integrity. While described herein in connection with a center nozzle burner tube, the invention has applicability in any nozzle burner tube, even without the “wagon-wheel” support structure. In other words, a support similar to the inner ring or hub 46, could be welded to the diffusion plate at any location where a nozzle burner tube is to be supported.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
