Patent Application
20170363291
Disclosed embodiments are generally related to fuel injectors for a gas turbine, and, more particularly, to fuel injectors including a lobed mixer and vanes for injecting alternate fuels in the turbine.
Economic considerations have pushed the development of gas turbines capable of using alternate fuels, such as may involve synthetic gases (e.g., syngas) in addition to using fuels, such as natural gas and liquid fuels, e.g., oil. These synthetic gases typically result from gasification processes of solid feedstock such as coal, pet coke or biomass. These processes may result in fuels having substantially different fuel properties, such as composition, heating value and density, including relatively high hydrogen content and gas streams with a significant variation in Wobbe index (WI). The Wobbe index is generally used to compare the combustion energy output of fuels comprising different compositions. For example, if two fuels have identical Wobbe indices, under approximately identical operational conditions, such as pressure and valve settings, the energy output will be practically identical.
Use of fuels having different fuel properties can pose various challenges. For example, as the heating value of the fuel drops, a larger flow area would be required to deliver and inject the fuel into the turbine and provide the same heating value. Thus, it is known to construct different passages for the injector flow to accommodate the Wobbe index variation in the fuels. Another challenge is that fuels having a high hydrogen content can result in a relatively high flame speed compared to natural gas and the resulting high flame speed can lead to flashback in the combustor of the turbine engine. See U.S. Pat. Nos. 8,661,779 and 8,511,087 as examples of prior art fuel injectors involving vanes using a traditional jet in cross-flow for injection of alternate fuels in a gas turbine.
The inventors of the present invention have recognized certain issues that can arise in the context of certain prior art fuel injectors that may involve a lobed mixer and vanes for injecting alternate fuels in a gas turbine. For example, some known fuel injector designs involve vanes using a jet in cross-flow injection to obtain a well-mixed fuel/air stream into the combustor of the turbine engine. However, such designs may exhibit a tendency to flashback, particularly in the context of fuels with high hydrogen content. In view of such recognition, the present inventors propose a novel fuel injector arrangement where fuel is injected without jet in cross-flow injection, such as in the direction of the air flow in lieu of the traditional jet in cross-flow injection. Additionally, the present inventors have further recognized that one known fuel injector design including a lobe mixer may result in certain mixing zones not conducive to a relatively uniform mixture of air and fuel, such as in zones where air flow may be somewhat diminished compared to other mixing zones. Accordingly, the present inventors further propose a fuel-routing structure conducive to an improved mixing of air and fuel.
In the following detailed description, various specific details are set forth in order to provide a thorough understanding of such embodiments. However, those skilled in the art will understand that embodiments of the present invention may be practiced without these specific details, that the present invention is not limited to the depicted embodiments, and that the present invention may be practiced in a variety of alternative embodiments. In other instances, methods, procedures, and components, which would be well-understood by one skilled in the art have not been described in detail to avoid unnecessary and burdensome explanation.
Furthermore, various operations may be described as multiple discrete steps performed in a manner that is helpful for understanding embodiments of the present invention. However, the order of description should not be construed as to imply that these operations need be performed in the order they are presented, nor that they are even order dependent, unless otherwise indicated. Moreover, repeated usage of the phrase “in one embodiment” does not necessarily refer to the same embodiment, although it may. It is noted that disclosed embodiments need not be construed as mutually exclusive embodiments, since aspects of such disclosed embodiments may be appropriately combined by one skilled in the art depending on the needs of a given application.
The terms “comprising”, “including”, “having”, and the like, as used in the present application, are intended to be synonymous unless otherwise indicated. Lastly, as used herein, the phrases “configured to” or “arranged to” embrace the concept that the feature preceding the phrases “configured to” or “arranged to” is intentionally and specifically designed or made to act or function in a specific way and should not be construed to mean that the feature just has a capability or suitability to act or function in the specified way, unless so indicated.
A plurality of vanes 20 may be circumferentially disposed about fuel delivery tube structure 12, such as arranged between fuel delivery tube structure 12 and shroud 16. A radial passage 22 may be constructed in each vane 20. Radial passage 22 is in fluid communication with first fuel supply channel 18 to receive a first fuel. In one non-limiting embodiment, radial passage 22 may be configured to branch into a set of passages 24 (e.g., axial passages) each having an aperture 26 arranged to inject the first fuel not in a jet in cross-flow mode, such as in a direction of air flow, schematically represented by arrows 25. This arrangement (without jet in cross-flow injection) is believed to substantially reduce the flashback tendencies generally encountered in the context of fuels with high hydrogen content. As may be appreciated in
A second fuel supply channel 27 is arranged in fuel delivery tube structure 12. Second fuel supply channel 27 may extend to a downstream end 28 of fuel delivery tube structure 12, where a mixer 30 with a plurality of lobes 32 (e.g., radially elongated folded edges) is disposed for fuel injection of a second fuel.
In one non-limiting embodiment, delivery tube structure 12 may comprise coaxially disposed inner 34 and outer tubes 36, wherein inner tube 34 comprises the second fuel supply channel 27, and where the first fuel supply channel 18 is annularly disposed between inner and outer tubes 34, 36. In one non-limiting embodiment the first fuel and the second fuel may comprise fuels having a different energy density. For example, without limitation, the first fuel that flows in first fuel supply channel 18 may comprise syngas, and the second fuel that flows in second fuel supply channel 27 may comprise natural gas.
In one non-limiting embodiment, mixer 30 comprises a means for routing the second fuel within a respective lobe, such as a fuel-routing structure 38 configured to route the second fuel within a respective lobe so that fuel injection of the second fuel takes place radially outwardly relative to a central region of the mixer, such as between a radially intermediate portion of the respective lobe and a radially outermost portion of the respective lobe. This is conceptually represented in
In one non-limiting embodiment, depending on the needs of a given application, the radially intermediate portion of the respective lobe may be disposed in a range from approximately 25% of the respective lobe height to approximately 75% of the respective lobe height. As may be appreciated in
In one non-limiting embodiment, as may be appreciated in
It will be appreciated that depending on the needs of a given application, one can optionally tailor aspects of the present invention based on the needs of the given application. For example, although aspects of the present invention are described in the context of a combination comprising vanes configured to inject a first fuel without jet in cross-flow injection, and a lobe mixer including a fuel-routing structure conducive to an improved mixing of air with a second fuel, broad aspects of the present invention need not be limited to such a combination. For example, in certain applications, one could optionally use the disclosed lobe mixer in combination with traditional vanes, such as may be configured to inject the first fuel with a jet in cross-flow injection. Alternatively, in certain other applications, one could optionally use the disclosed vanes, such as may be configured to inject the first fuel without jet in cross-flow injection with a traditional lobe mixer, such as may constructed without the disclosed fuel-routing structure. Thus, the disclosed embodiments need not be implemented in a combination, although they may be so implemented, since aspects of such disclosed embodiments may be individually tailored depending on the needs of a given application.
While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.
Development for this invention was supported in part by Contract No. DE-FC26-05NT42644, awarded by the United States Department of Energy. Accordingly, the United States Government may have certain rights in this invention.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/013486 | 1/29/2015 | WO | 00 |
