Patent Application
20130305734
The present application and the resultant patent relate generally to gas turbine engines and more particularly relate to a fuel plenum premixing tube with surface treatment thereon for use in a micro-mixer and the like for improved and uniformed temperature distribution.
Operational efficiency and output of a gas turbine engine generally increases as the temperature of the hot combustion gas stream increases. High combustion gas stream temperatures, however, may produce high levels of nitrogen oxides (NOx) and other types of regulated emissions. A balancing act thus exists between operating a gas turbine engine in an efficient temperature range while also ensuring that the output of nitrogen oxides and other types of regulated emissions remain below mandated levels.
Lower emission levels of nitrogen oxides and the like may be promoted by providing for good mixing of the fuel stream and the air stream before combustion. Such premixing tends to reduce combustion temperatures and the output of nitrogen oxides. One method of providing such good mixing is through the use of micro-mixers where the fuel and the air are mixed in a number of micro-mixing tubes within a plenum. In order to promote such good mixing, the same amount of fuel should be delivered to each mixing tube. This objective, however, may be challenging because fuel density is in part a function of temperature. Given such, ensuring that the fuel delivered to each tube has a uniform heat pickup may be difficult. Moreover, a significant temperature difference may develop between the mixing tubes and the outer barrel of the plenum. This temperature differential may lead to component distortion over time as well as a reduced component life.
There is thus a desire for a combustor with an improved micro-mixer design. Such an improved micro-mixer design may promote good fuel-air mixing while providing a more uniform thermal distribution across the mixing tubes and the outer barrel.
The present application and the resultant patent thus provide a micro-mixer fuel plenum for mixing a flow of fuel and a flow of air in a combustor. The micro-mixing fuel plenum may include an outer barrel and a number of mixing tubes positioned within the outer barrel. The mixing tubes may include one or more heat transfer features thereon.
The present application and the resultant patent further provide a method of promoting a uniform temperature distribution across a micro-mixer fuel plenum with a number of mixing tubes. The method may include the steps of flowing air at a first temperature through the mixing tubes in a first direction, flowing fuel at a second temperature across one or more heat transfer features on the mixing tubes in a second direction, exchanging heat between the flowing air and the flowing fuel across the heat transfer features, and flowing the fuel into the mixing tubes through a number of post orifices.
The present application and the resultant patent further provide a micro-mixer fuel plenum for mixing a flow of fuel and a flow of air in a combustor. The micro-mixer fuel plenum may include an outer barrel for introducing the flow of fuel and a number of mixing tubes positioned within the outer barrel for introducing the flow of air. The mixing tubes may include a number of post orifices and one or more heat transfer features thereon to exchange heat between the flow of fuel and the flow of air before the flow of fuel enters the post orifices.
These and other advantages and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
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, New York, 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.
In use, the flow of fuel 30 enters the micro-mixer fuel plenum 70 from the second end 82 through the fuel distribution plate 80 and flows along the outer surface 86 of the mixing tubes 74 in the fuel space 90. The flow of fuel 30 may be at a temperature TFUEL in the range of about 80 degrees to about 400 degrees Fahrenheit (about 26.7 degrees to about 204.4 degrees Celsius). The flow of air 20 enters the mixing tubes 74 at the first end 78. The flow of air 20 from the compressor 15 may be at a compressor discharge temperature, TCD, on the order of about 700 degrees to about 900 degrees Fahrenheit (about 371.1 degrees to about 782.2 degrees Celsius). The flow of fuel 30 flows through the post orifices 88 and mixes with the flow of air 20 to form a fuel/air mixture 92. The fuel/air mixture 92 then exits the mixing tube 74 about the second end 82.
The flow of air 20 also surrounds the outer barrel 72 of the micro-mixer fuel plenum 70 at about temperature TCD. As described above, the outer barrel 72 thus is exposed to both temperatures TCD and TFUEL. As such, the outer barrel 72 may be on the order of about 500 degrees to about 600 degrees Fahrenheit (about 260 degrees to about 315.6 degrees Celsius) such that the mixing tube 74 may be relatively hot while the outer barrel 72 may be relatively cooler. Other temperatures and other types of temperature differentials also may be accommodated herein.
The flow paths required for the flows of fuel 30 to reach each post orifice 88 thus may be unique such that the amount of heat pickup may vary about each mixing tube 74. Because density is a function of temperature, this non-uniformity may cause the amount of fuel delivered to each mixing tube 74 to vary accordingly. As described above, this variability may negatively impact emissions, flame holding, and overall performance and output. Likewise, the temperature differences between the mixing tubes 74 and the outer barrel 72 may result in a thermal mismatch therebetween such that the mixing tubes 74 may be in compression and may be plastically deformed. Such a temperature differential thus may result in component distortion and possibly damage over an extended period of time and use.
The outer surfaces 200 of some or all of the mixing tubes 130 thus may have one or more heat transfer features 220 formed therein. In this example, the heat transfer features 220 may be one or more recessed heat transfer features 230. The recessed heat transfer features 230 may be in the form of one or more threads 240 and the like. The recessed heat transfer features 230 may be formed by machining the threads 240 therein or by otherwise forming such recesses heat transfer features 230 into the outer surface 200 of the mixing tubes 130. Any number of the recessed heat transfer features 230 and the threads 240 may be used in any size, shape, or configuration. Other components and other configurations may be used herein.
The use of the heat transfer features 220 thus increases the surface area of the mixing tubes 130 so as to increase the amount of heat transferred to the flows of fuel 30 before the flows enter the post orifices 210. Specifically, the heat transfer features 220 promote uniformity in temperature distribution at the post orifices 210. By increasing the amount of heat pickup across the heat transfer features 220, the temperature of the flow of fuel 30 may approach a maximum value such that the fuel temperature TFUEL at the post orifices 210 may be substantially uniform. Likewise, increasing the amount of heat pulled out of the flow of air 20 in the mixing tubes 130 may result in a more favorable temperature distribution between the mixing tubes 130 and the outer barrel 120. By adding the heat transfer features 220 to the outer surface 200 of the mixing tube 130, the mixing tubes 130 also may become more compliant in addition to becoming cooler. Both of these outcomes improve the durability of the mixing tubes 130 and also unloads the joint between the mixing tubes 130 and the barrel 120.
The configuration of the heat transfer features 220 may vary and may be based upon the amount of heat pickup targeted and the allowable stresses herein. Given such, the heat transfer features 220 may be any number and type of the recessed heat transfer features 230 and/or the protruding heat transfer features 250 and/or combinations thereof. Other types of heat transfer features 220 also may be used herein. Specifically, any structure that increases the overall surface area of the mixing tubes 130 and the like so as to increase the amount of heat transferred may be used herein in any orientation or configuration. The use of the heat transfer features 220 herein thus promotes fuel uniformity across the components herein without adding additional complexity or operational costs.
It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
