DAMPING

TECHNICAL FIELD

The present application and the resultant patent relate generally to a gas turbine engine and more particularly relate to a combustor for a gas turbine engine with a bidirectional manifold used as a Helmholtz-type resonator for damping dynamics therein.

BACKGROUND OF THE INVENTION

Generally described, gas turbine engines combust a mixture of compressed air and compressed fuel to produce hot combustion gases. The hot combustion gases may be used to provide useful mechanical work. Combustion may occur in multiple combustors positioned radially around a longitudinal axis of the gas turbine engine. Because of the turbulent nature of the combustion process and the large volumetric energy released in closed cavities, such combustors may be susceptible to a wide range of modes and frequencies of combustion-induced unsteady pressure oscillations of large magnitudes. If one of the frequency bands corresponds to a natural frequency of a part or a subsystem within the gas turbine engine, damage to that part or to the entire engine may result.

Known methods to suppress these pressure oscillations, referred to herein as "dynamics", have traditionally focused on decoupling the excitation source from the feedback mechanism. Such suppression means generally are effective only over a limited operational range of the combustor.

There is thus a desire for improved combustor designs and methods of operations. Preferably, these designs and methods may limit combustor dynamics and the frequency ranges thereof so as to prevent damage thereto and ensure adequate component lifetime. SUMMARY OF THE INVENTION

The present application and the resultant patent thus provide a combustor for combusting a flow of air and a flow of fuel. The combustor may include a number of fuel nozzles, an air path with the flow of air therein leading to the fuel nozzles, and a manifold positioned in the air path upstream of the fuel nozzles. The manifold may include a number of resonator tubes.

The present application and the resultant patent further provide a method of operating a combustor of a gas turbine engine. The method may include the steps of combusting an ambient air flow, a low oxygen flow, and a fuel flow, producing combustion dynamics, positioning a bi-directional manifold in communication with the ambient air flow and the low oxygen flow, positioning a number of resonator tubes about the bi-directional manifold, and sizing the resonator tubes to dampen the combustion dynamics.

The present application and the resultant patent further provide a stoichiometric exhaust gas recirculation combustor for combusting an ambient air flow, a low oxygen flow, and a flow of fuel. The combustor may include a number of fuel nozzles, an ambient air path with the ambient air flow therein leading to the fuel nozzles, a low oxygen recirculation inlet with the low oxygen flow therein, and a bidirectional manifold in communication with the ambient air flow and/or the low oxygen flow. The bi-directional manifold may include a number of resonator tubes.

These and other features and advantages 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. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic view of a gas turbine engine. Fig. 2 is a side cross-sectional view of a compressor with a bi-directional manifold and a number of resonator tubes as may be described herein.

Fig. 3 is an expanded side cross-sectional view of a portion of the combustor of Fig. 2 showing the bi-directional manifold and the resonator tubes. Fig. 4 is a schematic view of an example of a Helmholtz resonator.

DETAILED DESCRIPTION

Referring now to the drawings, in which like numerals refer to like elements throughout the several views, Fig. 1 shows a schematic view of gas turbine engine 10 as may be used herein. The gas turbine engine 10 may include a compressor 15. The compressor 15 compresses an incoming flow of air 20. The compressor 15 delivers the compressed flow of air 20 to a combustor 25. The combustor 25 mixes the compressed flow of air 20 with a compressed flow of fuel 30 and ignites the mixture to create a flow of combustion gases 35. Although only a single combustor 25 is shown, the gas turbine engine 10 may include any number of combustors 25. The flow of combustion gases 35 is in turn delivered to a turbine 40. The flow of combustion gases 35 drives the turbine 40 so as to produce mechanical work. The mechanical work produced in the turbine 40 drives the compressor 15 via a shaft 45 and an external load 50 such as an electrical generator and the like.

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 anyone of a number of different gas turbine engines offered by General Electric Company of Schenectady, New York 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.

Fig. 2 shows an example of the combustor 25. In this example, a stoichiometric exhaust gas recirculation ("SEGR") combustor 100 is shown. Other types of combustors may be used herein. The stoichiometric exhaust gas recirculation combustor 100 may include a number of fuel nozzles 110 positioned within an end cap 120. Although five (5) fuel nozzles 110 are shown, any number of the fuel nozzles 110 may be used herein. The fuel nozzles 1 10 may be in communication with the flow of fuel 30 via one or more fuel inlets 130. A low oxygen recirculation inlet 140 also may be positioned about the end cap 120 to provide a low oxygen flow 150 to the fuel nozzles 110. The low oxygen flow 150 may be sent from the turbine 40 via a stoichiometric exhaust gas recovery compressor (not shown) and the like.

The stoichiometric exhaust gas recirculation combustor 100 also may include a combustion liner 160. The combustion liner 160 may define a combustion zone 170 therein. A flow sleeve 180 may surround the combustion liner 160 and may define an ambient air path 190 therein for the flow of ambient air 20 from the compressor 15. A casing 200 may surround the flow sleeve 180 and the combustion liner 160. A transition piece 210 may be positioned downstream of the combustion zone 170.

An extraction port 220 may be positioned about the casing 200 and in communication with the ambient air path 190 of the flow sleeve 180 in one direction and the fuel nozzles 110 and the low oxygen recirculation inlet 140 in the other. The extraction port 220 may be in communication with the turbine 40 and otherwise. In an injection mode, the incoming air flow 20 extends along the ambient air path 190 where it mixes with the low oxygen flow 150 and the flow of fuel 130 downstream of the fuel nozzle 1 10 and is combusted within the combustion zone 170. Alternatively, a portion of the incoming air flow 20 may be extracted via the extraction port 220 while the remaining flow continues to the fuel nozzles 1 10. In an extraction mode, a portion of the low oxygen flow 150 also may be extracted via the extraction port 220. Other configuration and other components may be used herein. The end cap 120 also may include a bi-directional manifold 230 to accommodate the injection mode and the extraction mode, i.e., for an injection flow into the combustor 100 or for an extraction flow. The bi-directional manifold 230 may be largely circular in shape and may include a circular cavity 240. The bi-directional manifold 230 also may include a number of resonator tubes 250 extending between the cavity 240 and towards the flow sleeve 180 within the ambient air path 190. As is shown in Fig. 4, the bi-directional manifold 230 largely acts as a Helmholtz resonator 260. The Helmholtz resonator 260 thus includes the cavity 240 acting as a body 270 and the resonator tubes 250 acting as a throat 280. Generally defined, the Helmholtz resonator 260 is an acoustical chamber that induces a pressurized fluid to oscillate at a particular frequency. The geometric configuration of the Helmholtz resonator 260 directly determines the frequency of oscillation. If the fluid pressure is fluctuating due to the influence of an external force, the resonator 260 may dampen the magnitude of the fluctuations if tuned to the frequency of those fluctuations. The Helmholtz resonator 260 includes the body 270 and the throat 280 with a smaller diameter than the body 270. Pressurized fluid entering the throat 280 is collected in the body 270 until the pressure within the body 270 becomes greater than the external fluid pressure. At that point, the fluid within the body 270 exits via the throat 280, thereby reducing the pressure within the body 270. The lower body pressure induces the fluid to re-enter the body 270, such that the process repeats. The cyclical movement of air established a resonant frequency of the Helmholtz resonator 260.

As above, the resonate frequency of the Helmholtz resonator 260 is determined mainly by its geometric configuration. Specifically, a cylindrical Helmholtz resonator 60 produces a resonant frequency based in part upon the following equation: /= c/2/7 * i ⁷ ILHD ² . In this equation, "c" is the speed of sound through the fluid {e.g., air, fuel, diluent, etc.), "<f is the diameter of the throat 280, "Z" is the length of the throat 280, "H" is the length of the body 270, and "£>" is the diameter of the body 270. In this example, the configuration of the body 270, i.e. , the circular cavity 240, is fixed such that the resonant frequency may be varied by varying the length and diameter of the throat 280, i.e., the resonator tubes 250. As such, the resonator tubes 250 may be sized to dampen certain frequency ranges such as those most severe for the combustion hardware and the manifold 230 itself. Any number of resonator tubes 250 may be used herein in any desired size, shape, or configuration. Resonator tubes 250 of different configurations also may be used herein together so as to dampen different frequency ranges. The Helmholtz resonator 260 formed by the bi-directional manifold 130 thus prevents high cycle fatigue herein by damping certain frequency ranges. Moreover, the Helmholtz resonator 260 provides such protection whether the bi-directional manifold 230 is operating in the injection mode or the extraction mode. Although a stoichiometric exhaust gas recirculation combustor 100 has been described herein, the Helmholtz resonator 260 may be applicable to other types of combustors and to other types of devices subject to frequency oscillations and the like. Uni-directional, bidirectional, or multi-directional flows may be used herein.

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.