Patent Application
20110252803
The present invention relates generally to a fuel nozzle in a combustor and a method for making such a fuel nozzle.
Combustors are widely used in commercial operations. For example, a typical gas turbine includes at least one combustor that injects fuel into the flow of a compressed working fluid and ignites the mixture to produce combustion gases having a high temperature and pressure. The combustion gases exit the combustor and flow to a turbine where they expand to produce work.
During full speed base load operations, the flow rate of the fuel and compressed working fluid mixture through the nozzles 18, 20 is sufficiently high so that combustion occurs only in the downstream chamber 26. During reduced power operations, however, the primary nozzles 18 operate in a diffusion mode in which the flow rate of the fuel and compressed working fluid mixture from the primary nozzles 18 is reduced so that combustion of the fuel and the compressed working fluid mixture from the primary nozzles 18 occurs in the upstream chamber 24. During all operations, the secondary nozzle 20 operates as a combined diffusion and premix nozzle that provides the flame source for the operation of the combustor. In this manner, fuel flow through the primary and secondary nozzles 18, 20 can be adjusted, depending on the operational load of the combustor, to optimize NOx emissions throughout the entire operating range of the combustor.
Various efforts have been made to design and manufacture fuel nozzles with improved premixing and diffusion capabilities, especially for higher reactivity fuels. For example, direct metal laser sintering, braising, and casting are manufacturing techniques previously used to fabricate fuel nozzles that premix the fuel and compressed working fluid prior to combustion. However, these manufacturing techniques are relatively expensive, time-consuming, and otherwise less than optimum for large-scale production. Therefore, an improved fuel nozzle that can pre-mix the fuel and compressed working fluid prior to combustion would be desirable. In addition, an improved method for making such a nozzle that utilizes less expensive machining techniques rather than other more costly techniques would be desirable.
Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.
One embodiment of the present invention is a fuel nozzle that includes a fuel plenum and an outer body surrounding the fuel plenum. The outer body includes a plurality of bore holes that extend longitudinally through the outer body. The fuel nozzle further includes means for fixedly attaching the fuel plenum to the outer body and a plurality of passages in the outer body between at least some of the plurality of bore holes and the fuel plenum, wherein the plurality of passages provide fluid communication between the fuel plenum and at least some of the plurality of bore holes.
Another embodiment of the present invention is a fuel nozzle that includes an outer body, wherein the outer body includes a plurality of bore holes that extend longitudinally through the outer body. A fuel plenum is inserted into the outer body, and a connection is between the outer body and the fuel plenum, wherein the outer body is fixed to and removable from the fuel plenum. A plurality of passages is in the outer body between at least some of the plurality of bore holes and the fuel plenum, wherein the plurality of passages provide fluid communication between the fuel plenum and at least some of the plurality of bore holes.
A still further embodiment of the present invention is a method for manufacturing a fuel nozzle. The method includes drilling a plurality of bore holes longitudinally through an outer body and drilling a plurality of passages in the outer body to at least some of the plurality of bore holes. The method further includes inserting a fuel plenum into the outer body, wherein the plurality of passages in the outer body provide a fluid communication between at least some of the plurality of bore holes and the fuel plenum, and attaching the fuel plenum to the outer body.
Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.
A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:
Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention.
Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Embodiments of the present invention may be machined and assembled to create a premixed direct injection (PDI) fuel nozzle design. In general, the fuel nozzle design comprises two components which may be separately machined or fabricated for subsequent assembly. One piece may be referred to as the tip or outer body, and the other piece may be referred to as the fuel cartridge or fuel plenum. The fuel plenum directs fuel downstream against a front wall of the outer body to provide impingement cooling to the front wall. After impinging against the front wall, the fuel then flows through passages to bore holes in the outer body where the fuel mixes with a fluid flowing through the bore holes before exiting the fuel nozzle and flowing into the combustion chamber. The fuel plenum and outer body, with their various bore holes and other passages, may be readily manufactured by machining instead of requiring more costly processes such as direct metal laser sintering. As a result, fuel nozzles according to various embodiments of the present invention may be less expensive to manufacture, while still providing improved cooling to the fuel nozzle and premixing the fuel prior to combustion.
The outer body 34 includes a front wall 42 downstream of the fuel plenum 32 and proximate to the plurality of apertures 40 in the fuel plenum 32. The front wall 42 is generally the closest portion of the fuel nozzle 30 to the combustion flame and therefore is subjected to higher temperatures than the remainder of the fuel nozzle 30. Fuel flowing through the plurality of apertures 40 exits the fuel plenum 32 and impinges on the front wall 42 to provide impingement cooling to the front wall 42.
The outer body 34 generally surrounds the fuel plenum 32, creating a space or annular plenum 44 between the fuel plenum 32 and the outer body 34. The outer body 34 further includes a plurality of bore holes 46 that extend longitudinally through the outer body 34. The bore holes 46 may be arranged in any desired pattern. For example, as shown in
The outer body 34 further includes a plurality of passages 50 between at least some of the bore holes 46 and the fuel plenum 32. The plurality of passages 50 provide fluid communication between the fuel plenum 32 and at least some of the plurality of bore holes 46. Specifically, fuel exiting the fuel plenum 32 through the plurality of apertures 40 impinges on the front wall 42 to provide impingement cooling to the front wall 42. The fuel then flows through the annular plenum 44 until it reaches one of the plurality of passages 50 where it flows into the associated bore hole 46. In this manner, the fuel mixes with the fluid (e.g., compressed working fluid from a compressor) flowing through the bore hole 46 before exiting the bore hole 46 and entering the combustion chamber.
The fuel plenum 32 and outer body 34 may be separately machined and manufactured for subsequent assembly. For example, the fuel plenum 32 and/or outer body 34 may be cast from a molten metal. The various bore holes 46 and passages 50 in the outer body 34 may then be drilled to accurately and inexpensively position, size, and orient the various elements in the outer body 34. If desired, the inlet 48 to various bore holes 46 may be further machined to include a beveled surface or otherwise increase the surface area of the inlet 48 for specific boreholes 46, depending on particular design considerations. The fuel plenum 32 may then be inserted into the annular plenum 44 defined by the outer body 34 and attached to the outer body 34.
Various methods and means are known in the art for attaching or connecting the fuel plenum 32 to the outer body 34. For example, brazing, welding, complementary threads, seal rings, and other equivalent techniques and connections are known in the art for attaching or connecting the fuel plenum 32 to the outer body 34. Depending on the particular design needs, the connection between the fuel plenum 32 and the outer body 34 may be permanent or temporary to allow for removal of the fuel plenum 32 during maintenance or repair. The particular embodiment shown in
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
