Patent Application
20120174589
The invention relates to gas turbines and, more particularly, to an end cover assembly for capping a back end of a combustion chamber.
Existing end covers for capping the back end of a combustion chamber have durability issues due to the complexity of the end cover construction. The end cover is typically formed of a thick plate that commutes multiple fuel gas passages to fuel nozzles of the combustor with internal passages. In a typical construction, the end cover includes welded plates that create an internal pocket for fuel passages and/or brazed inserts such as fuel flow adapters to channel fuel gas to multiple passages on the nozzles. In addition to the long-term durability issues, the complex design is expensive to manufacture.
It would be desirable to design an end cover assembly that eliminates welding and/or brazing to reduce the durability issues and to simplify the construction.
In an exemplary embodiment, an end cover assembly caps a back end of a combustion chamber. The end cover assembly includes an end cover plate securable to the back end of the combustion chamber, and a monolith block secured to the end cover plate. The end cover plate is a one piece member with fuel channels therethrough, where the fuel channels are sized and positioned to interact with fuel nozzle inlet ports. The monolith block includes internal fuel gas passages positioned relative to the fuel channels in the end cover plate to commute fuel gas to the fuel channels of the end cover plate.
In another exemplary embodiment, a gas turbine combustor includes a casing with a combustion chamber, a plurality of fuel nozzles disposed in the casing adjacent the combustion chamber, and the end cover assembly of the described embodiments secured to the casing and capping a back end of the combustion chamber.
In yet another exemplary embodiment, an end cover assembly is provided in combination with a gas turbine combustor for capping a back end of a combustion chamber. The end cover assembly includes an end cover plate securable to the back end of the combustion chamber, and a monolith block secured to the end cover plate. The end cover plate is constructed without welded gas passage plates and without brazed flow passage inserts and includes fuel channels therethrough, where the fuel channels are sized and positioned to interact with fuel nozzle inlet ports. The monolith block includes internal fuel gas passages positioned relative to the fuel channels in the end cover plate to commute fuel gas to the fuel channels of the end cover plate.
The combustion system of a gas turbine generates hot gases to drive a turbine. The turbine, in turn, drives a compressor that provides compressed air for combustion in the combustion system. The turbine also produces usable output power. A combustion system for a gas turbine may be configured as a circular array of combustion chambers arranged to receive compressed air from the compressor, inject fuel into the compressed air to create a combustion reaction, and generate hot combustion gases for the turbine.
As noted, in a typical construction, an end cover plate assembly bolts to the forward casing and contains the pressure and flow on the forwardmost end of the combustor assembly. The end cover assembly of the described embodiments is modified from the conventional welded and/or brazed assembly into a two component bolted assembly.
With reference to
A monolith block 36 is secured to the end cover plate 32. The monolith block 36 is bolted to a center of the end cover plate 32 on the cold side (outward side) of the cover. The monolith block 36 uses internal flow passages 38 to transfer multiple gas inlet connections to the respective fuel nozzle connections. That is, the fuel gas passages 38 are positioned relative to the fuel channels 34 in the end cover plate 32 to commute fuel gas to the fuel channels 34 of the end cover plate 32, which in turn connect to the fuel nozzles.
In a preferred construction, the monolith block includes three fuel gas inlets 40, 42, 44 fluidly connected to respective ones of fuel nozzle inlet ports. With the combustion chamber including five outer fuel nozzles surrounding a center fuel nozzle, a first one 40 of the three fuel gas inlets may be connected to the center nozzle, a second one 42 of the three fuel gas inlets may be connected to two of the five outer nozzles, and a third one 44 of the three fuel gas inlets may be connected to the remaining three of the five outer nozzles. As shown, the three fuel gas inlets 40, 42, 44 may be staggered to enable an application of fuel gas at different load conditions. That is, the three premix fuel inlet ports 40, 42, 44 allow the gas fuel to be metered for differing modes of operation.
The first inlet 40 is generally used at start up when the engine is cold. The second inlet 42 is used for a 40-60% load condition and during start up. The fuel nozzles of the second inlet 42 are aligned radially and the second inlet 42 combustion zones are commuted from can-to-can using cross fire tubes to ensure all combustion cans are fired. The third inlet 44 is used for roughly 50-80% load conditions. Running the second and third inlets 42, 44 combined is used for roughly 80% to full load with the option to add the first inlet 40 for additional power.
Differing fuel mixtures and fuel rates with the three inlet connections 40, 42, 44 are used to adjust operating conditions to account for partial load, cold or hot day inlet air conditions, etc. Note that alternately additional premix connections could be added to the monolith block 36 and/or the monolith block 36 could be used in conjunction with conventional end cover assemblies to add fuel connection flexibility. The invention should not be limited to only three premix fuel connections as additional premix connections are possible.
As shown in
By using the end cover plate 32 and monolith block 36 to define the end cover assembly 10, the end cover plate 32 can be constructed without welded gas passage plates and/or without brazed flow passage inserts. The resulting simplified construction reduces manufacturing costs and improves long-term durability.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
