Patent Application
20130241089
Embodiments of the present application relate generally to gas turbine engines and more particularly to micromixers.
Gas turbine efficiency generally increases with the temperature of the combustion gas stream. Higher combustion gas stream temperatures, however, may produce higher levels of undesirable emissions such as nitrogen oxides (NOx) and the like. NOx emissions generally are subject to governmental regulations. Improved gas turbine efficiency therefore must be balanced with compliance with emissions regulations.
Lower NOx emission levels may be achieved by providing for good mixing of the fuel stream and the air stream. For example, the fuel stream and the air stream may be premixed in a Dry Low NOx (DLN) combustor before being admitted to a reaction or a combustion zone. Such premixing tends to reduce combustion temperatures and NOx emissions output.
In current micromixer designs, there may be multiple fuel feeds and/or liquid cartridge or blank feeds that obstruct air flow and decrease the mixing of fuel and air. Also, current micromixers are generally supported by external walls that inhibit air flow to the head end of the micromixer. Accordingly, there is a need for a micromixer that better facilitates fuel and air mixing.
Some or all of the above needs and/or problems may be addressed by certain embodiments of the present application. According to one embodiment, there is disclosed a micromixer. The micromixer may include one or more base nozzle structures. The base nozzle structures may include coaxial tubes. The coaxial tubes may include an inner tube and an outer tube. The micromixer may also include one or more segmented mixing tube bundles at least partially supported by a respective base nozzle structure. Moreover, the micromixer may include an end cap assembly disposed about the one or more segmented mixing tube bundles.
According to another embodiment, there is disclosed a micromixer. The micromixer may include a base nozzle structure. The base nozzle structures may include coaxial tubes. The coaxial tubes may include an inner tube and an outer tube. The micromixer may also include a plurality of mixing tubes forming a segmented mixing tube bundle that is at least partially supported by a respective base nozzle structure. Moreover, the micromixer may include a removable end cap assembly disposed about the the segmented mixing tube bundle.
Further, according to another embodiment, there is disclosed a micromixer. The micromixer may include one or more base nozzle structures. The micromixer may also include one or more segmented mixing tube bundles at least partially supported by a respective base nozzle structure. Moreover, the micromixer may include an end cap assembly disposed about the one or more segmented mixing tube bundles.
Other embodiments, aspects, and features of the invention will become apparent to those skilled in the art from the following detailed description, the accompanying drawings, and the appended claims.
Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:
Illustrative embodiments will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments are shown. The present application may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Like numbers refer to like elements throughout.
Illustrative embodiments are directed to, among other things, micromixers for a combustor.
The gas turbine engine 10 may use natural gas, various types of syngas, and/or other types of fuels. The gas turbine engine 10 may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y., including, but not limited to, those such as a 7 or a 9 series heavy duty gas turbine engine and the like. The gas turbine engine 10 may have different configurations and may use other types of components.
Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together.
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An air inlet 114 is disposed upstream of the mixing tubes 108 and supplies air to the mixing tubes 108. In certain embodiments, an air conditioner plate 116 may be disposed upstream of the mixing tubes 108.
The fuel supplied by the outer tube 112 of the coaxial tubes enters the fuel plenum 104 before entering the mixing tubes 108. In certain embodiments, the fuel entering the fuel plenum 104 is redirected 180 degrees (as indicated by the dashed arrows at the end of outer tube 112) before entering the mixing tubes 108 through one or more holes 118 in the mixing tubes 108. In other embodiments, the fuel enters the fuel plenum 104 directly without being redirected.
In certain embodiments, a fuel conditioning plate 120 is disposed within the fuel plenum 104. In other embodiments, the fuel plenum 104 does not include the fuel conditioning plate 120. The air/fuel mixture exits the mixing tubes 108 (as indicated by the solid arrow within the mixing tubes 108) into the combustion chamber.
The base nozzle structure 102 of the micromixer 100 provides both structural support and an outer tube 112 for the fuel to enter the fuel plenum 104. As stated above, the fuel can be gas. The inner tube 110 may include a liquid cartridge (for dual fuel), a blank cartridge (for gas only), an igniter, a flame detector, or any other combustor component. The base nozzle structure 102 is attached to the inlet plate 116 of the micromixer assembly. The fuel is injected from the end cover 109 into the base nozzle structure 102 and flows through the annulus formed between inner tube 110 and the outer tube 112 into the fuel plenum 104. The fuel then enters the mixing tube holes 118 where it is mixed with head end air. The head end air flows through the flow conditioning plate 116 and into the mixing tube 108.
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For each segmented portion of the micromixer, there is only one air side flow obstruction—the nozzle base structure. Accordingly, the present micromixer reduces the number of protrusions into the air flow path so as to facilitate a more uniform air feed in the mixing tubes.
A technical advantage of the present micromixer includes a more uniform air feed to the mixing tubes. Another advantage of the present micromixer is that it facilitates fuel feed distribution to the mixing tubes and does not require a complex base nozzle structure to support the micromixer assembly. This results in a micromixer assembly that has lower NOx emissions because the air and fuel distribution are more uniform. The overall cost of the micromixer may be less and it may be more reliable because the number of welds is reduced, the number of parts is decreased, and the analytical assessment is more straightforward.
Although embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the disclosure is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the embodiments.
