Patent Application
20100011769
The invention generally relates to a gas turbine engine, and more particularly to a Helmholtz resonator positioned in a particular upstream zone of a combustor of a gas turbine engine.
Combustion engines such as gas turbine engines are machines that convert chemical energy stored in fuel into mechanical energy useful for generating electricity, producing thrust, or otherwise doing work. These engines typically include several cooperative sections that contribute in some way to this energy conversion process. In gas turbine engines, air discharged from a compressor section and fuel introduced from a fuel supply are mixed together and burned in a combustion section. The products of combustion are harnessed and directed through a turbine section, where they expand and turn a central rotor.
A variety of combustor designs exist, with different designs being selected for suitability with a given engine and to achieve desired performance characteristics. One popular combustor design includes a centralized pilot burner (hereinafter referred to as a pilot burner or simply pilot) and several main fuel/air mixing apparatuses, generally referred to in the art as injector nozzles, swirlers, main swirlers or main swirler assemblies, arranged circumferentially around the pilot burner. With this design, a central pilot flame zone and a mixing region are formed. During operation, the pilot burner selectively produces a stable flame that is anchored in the pilot flame zone, while the fuel/air mixing apparatuses produce a mixed stream of fuel and air in the above-referenced mixing region. The stream of mixed fuel and air flows out of the mixing region, past the pilot flame zone, and into a main combustion zone of a combustion chamber, where additional combustion occurs. Energy released during combustion is captured by the downstream components to produce electricity or otherwise do work.
It is known that high frequency pressure oscillations may be generated from the coupling between heat release from the combustion process and the acoustics of the combustion chamber. If these pressure oscillations, which are sometimes referred to as combustion dynamics, or as high frequency dynamics (“HFD”), reach a certain amplitude they may cause nearby structures to vibrate and ultimately break. A particularly undesired situation is when a combustion-generated acoustic wave has a frequency at or near the natural frequency of a component of the gas turbine engine. Such adverse synchronicity may result in sympathetic vibration and ultimate breakage or other failure of such component.
Various resonator boxes for the combustion section of a gas turbine engine have been developed to damp such undesired acoustics and reduce the risk of the above-noted problems. For example, U.S. Pat. No. 5,373,695, issued Dec. 20, 1994 to Aigner et al., teaches a “scavenged” Helmholtz resonator, consisting of a supply tube, resonance volume and damping tube, in the region of the burners.
U.S. Pat. No. 5,644,918, issued Jul. 8, 1997 to Gulati et al. teaches forming one or more resonance cavities for Helmholtz resonators between first and second plates located in the head end of the combustor casing. These plates define a space that includes the main fuel/air mixing apparatuses, which are referred to as premixers. No pilot burner is included in this design. This patent also teaches providing a cavity between the casing and the liner, so as to form one or more Helmholtz resonators circumferentially about a portion of the combustor.
U.S. Pat. No. 7,089,741, issued Aug. 15, 2006 to Ikeda et al. teaches forming a resonance space about a wall of a combustion liner that defines a combustion region. The resonance space connects to the combustion region by a plurality of through-holes. Additionally, cooling holes are provided along the sides of housings that help define the resonance space, stated as desirable along an upstream side and also shown along a downstream side. Purge holes also are provided along a more radially outwardly disposed surface.
While the above approaches may provide one or more favorable features, to address undesired combustion-generated acoustic waves there still remains in the art a need for a more effective and efficient resonator.
The invention is explained in following description in view of the drawings that show:
It is generally appreciated that damping resonators, such as Helmholtz resonators, that are disposed relatively downstream of a primary region of combustion have a disadvantage: the compressed air passing through such resonators, into the hot gas path, represents an inefficient use of such air. This is because such air flowing through the resonator may not be fully used in the combustion process. More upstream resonators, including those described above, often present complex structural additions in a region that already has space demands for a number of components and functions.
The present inventors have appreciated a solution to providing an effective Helmholtz resonator arrangement by utilizing an annular region in the combustor not previously utilized for such purpose. In various embodiments this also improves performance in ways in addition to vibration damping.
In many gas turbine combustors there exists an annular region having a primary function of providing a residence time for greater mixing of the fuel/air mixture after it leaves a main swirler. The residence time of a mixture through this region allows the fuel/air mixture to achieve a greater uniformity. In a range of particular gas turbine combustors, this annular region, hereinafter referred to as a post-swirler homogenization zone, begins at the base plate, ends at a plane that includes the downstream edge of the pilot cone, and excludes the space within the pilot cone. This post-swirler homogenization zone is identified as 110 in
Various embodiments of the present invention share a common concept: they modify the conventional post-swirler homogenization zone 110 into a combination Helmholtz resonator-fuel/air mixing region, wherein the fuel/air mixing region is defined at least in part by a flow-directing structure. This not only provides for efficient space utilization to achieve a resonator function, but in at least some embodiments constrains the post-swirler homogenization zone. Such constraining allows for one or more Helmholtz resonators to comprise a portion of this zone that remains after provision of the fuel/air mixing region(s) defined by flow-directing structure(s), such as is described in the examples that follow.
In various embodiments the present invention is achieved by forming a plurality of flow-directing structures, each aligned with one of the main swirlers and a top plate at or near, and parallel with, the pilot cone plane. The area outside of the flow-directing structures, together with the base plate, the newly provided top plate and the outer pilot cone, define a complex-shaped volume that remains separated from the fuel/air flow paths from the main swirlers and from the pilot. This remaining volume is referred to below as the remainder. This complex-shaped remainder may be utilized for all or part of cavities of one or more Helmholtz resonators.
The figures discussed below depict non-limiting embodiments of the present invention.
Enclosing a space that includes a combustion zone 280 is a liner 232. A flow-directing structure 240 extends from the downstream end 219 of a respective main swirler assembly 218 to a top plate structure 241, thereby directing a fuel/air mixture (not shown) from the respective swirler assembly 218 into the combustion zone 280 that begins substantially adjacent the downstream edge 224 of the pilot cone 222.
Referring in part to
It is appreciated that in other embodiments the remainder 244 may be subdivided into one or more cavities for one or more Helmholtz resonators, and/or a particular Helmholtz resonator may include a cavity that includes a portion of the remainder and additional volume from space not in the post-swirler homogenization zone. As an example,
In contrast to more complex top plates, one example of which is described below, the top plate 342 in
In both
It is noted that in some embodiments there may be an outer pilot cone and an inner pilot cone. This is shown, for example, in
It is noted that in some embodiments one or more apertures that communicate with a cavity of a Helmholtz resonator of the present invention may be provided in the flow-directing structure. For example,
Furthermore,
Thus, distilling features from the various embodiments explicitly depicted herein, features of the present invention are directed to a gas turbine combustor Helmholtz resonator comprising a cavity at least partly between a combustor base plate transverse wall and a transverse wall of a top plate structure and at least one aperture defining a resonator throat and communicating with a combustion zone downstream of the top plate structure transverse wall. In some embodiments the indicated at least one aperture of the top plate structure is through the top plate structure transverse wall. In various embodiments a flow-directing structure between a main swirler assembly and the top plate structure transverse wall separates a flow path from the cavity. The flow-directing structure may be aligned with a passageway in the top plate transverse wall to provide for passage of the fuel/air mixture passing from the main swirler assembly through the flow-directing structure. The at least one aperture through the top plate structure and communicating with the cavity may be through the flow-directing structure or through the top plate structure transverse wall, or elsewhere on the top plate.
As is known to those skilled in the art, the frequency of the resonance for a Helmholtz resonator, fH, is as follows:
where v is the speed of sound in the resonator volume, VO, A is the cross-sectional area of the throat, and L is the length of the throat. The throat in some embodiments only comprises the aperture(s) communicating with the combustion zone and in other embodiments also includes a tubular extension thereto (this extending the overall length of the throat). The throat length L (also referred to by some as the neck length) appears in the denominator since the inertia of the air (or other fluid) is proportional to this length. The resonator volume, VO, also is in the denominator since the spring constant of the air (or other fluid) in the cavity is inversely proportional to its volume. It is noted that providing apertures in the base plate into the cavity of a Helmholtz resonator is viewed to affect the speed of sound therein and thus alter its resonance frequency.
Embodiments of the present invention are used in gas turbine engines such as are represented by
All patents, patent applications, patent publications, and other publications referenced herein are hereby incorporated by reference in this application in order to more fully describe the state of the art to which the present invention pertains, to provide such teachings as are generally known to those skilled in the art.
While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Moreover, when any range is described herein, unless clearly stated otherwise, that range includes all values therein and all subranges therein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
