Patent Application
20100058767
This invention relates to turbomachines. More particularly, this invention relates to a secondary fuel nozzle of a dry low NOx (“DLN”) combustor for a turbomachine having an improved swirl angle.
A conventional dry low NOx DLN combustor includes a fuel injection system having primary nozzles and a secondary fuel nozzle, a liner, a venturi and a cap/centerbody assembly. In the system, a fuel and air mixture travels through an annular passage bound by the secondary fuel nozzle and an outer burner tube attached to the liner. A bulk component of flow velocity, (i.e., swirl) is imparted on the mixture prior to being burned in a downstream combustion chamber of the annular passage. In the conventional low NOx DLN combustor, the reduction of NOx emission is sensitive to bulk swirl characteristics of the secondary fuel nozzle. That is, the swirl angle of reacting combustion gases is a significant parameter in the stability and emissions of the combustor. In the conventional combustor, the swirl angle is typically less than or equal to approximately 45°.
An exemplary embodiment of the present invention provides a combustor includes a primary combustion chamber and a secondary combustion chamber, one or more primary nozzles disposed in the primary combustion chamber and providing fuel to the primary combustion chamber, a centerbody assembly, a venturi disposed downstream of the centerbody assembly, and a secondary fuel nozzle housed within the centerbody assembly and extending towards the venturi and providing fuel to the secondary combustion chamber. The secondary fuel nozzle includes a fuel passage and an air passage, and a swirler positioned around the fuel passage and having one or more vanes projecting radially within the air passage, each vane having a trailing edge arranged at a swirl angle relative to a longitudinal axis of the secondary fuel nozzle, wherein the swirl angle is greater than 45°.
Another exemplary embodiment of the present invention provides a nozzle for a combustor. The nozzle includes a nozzle body housed within a centerbody assembly of the combustor, the nozzle body including a fuel passage, and an air passage surrounding the nozzle body, and a swirler located radially between the fuel passage and the air passage, the swirler including one or more vanes circumferentially spaced about the fuel passage, each vane having a trailing edge arranged at an angle of greater than 45° relative to a longitudinal axis of the nozzle body.
Another exemplary embodiment of the present invention provides a method for reducing NOx in a combustor. The method includes providing a nozzle in a centerbody assembly of the combustor having a fuel passage and a air passage, and a swirler in the nozzle supporting the fuel passage and having one or more vanes shaped to create a swirl angle relative to a longitudinal axis of the nozzle, delivering discharge air from a compressor to the air passage and fuel to the fuel passage, and mixing, via the swirler, the discharge air with fuel, and swirling the mixture at a swirl angle greater than 45°.
Another exemplary embodiment of the present invention provides a turbomachine that includes a compressor and at least one combustor configured to receiving incoming fuel and discharge air from the compressor. The combustor includes a primary combustion chamber and a secondary combustion chamber, one or more primary nozzles disposed in the primary combustion chamber and providing fuel to the primary combustion chamber, a centerbody assembly, a venturi disposed downstream of the centerbody assembly, a secondary fuel nozzle housed within the centerbody assembly and extending towards the venturi and providing fuel to the secondary combustion chamber. The secondary fuel nozzle includes a fuel passage and an air passage, and a swirler positioned around the fuel passage and having one or more vanes projecting radially within the air passage, each vane having a trailing edge arranged at a swirl angle relative to a longitudinal axis of the secondary fuel nozzle, the swirler configured to swirl a mixture of the discharge air in the air passage and fuel in the fuel passage at a swirl angle greater than 45°. The turbomachine further includes at least one turbine operatively connected to the combustor.
Additional features and advantages are realized through the techniques of exemplary embodiments of the invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features thereof, refer to the description and to the drawings.
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According to an embodiment of the present invention, by increasing the angle of the swirler of the secondary fuel nozzle to greater than 45°, the present invention provides the advantage of reducing NOx emissions while operating the combustor.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, the use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.
