AXIAL STAGE INJECTION DUAL FREQUENCY RESONATOR FOR A COMBUSTOR OF A GAS TURBINE ENGINE

Abstract

A gas turbine engine (202) including a secondary fuel stage (218) which also functions as a dual frequency resonator. The engine includes a combustor (210) and a casing (205) enclosing the combustor to define a volume (214). The secondary fuel stage includes a nozzle (217) sized to be effective as a transverse resonator at a high frequency. The nozzle and the volume (214) of the casing are sized to be effective as a longitudinal resonator at an intermediate frequency.

Description

STATEMENT REGARDING FEDERALLY SPONSORED DEVELOPMENT

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.

FIELD OF THE INVENTION

The invention relates to gas turbine engines, and more particularly to a resonator used to dampen resonance frequencies in a combustor of a gas turbine engine.

BACKGROUND OF THE INVENTION

A conventional combustible gas turbine engine includes a compressor section, a combustion section including a plurality of can-annular combustor apparatuses, and a turbine section. Ambient air is compressed in the compressor section and directed to the combustor apparatuses in the combustion section. FIG. 1 illustrates a conventional combustor 10. As illustrated in FIG. 1, it is known that injecting fuel at two axially spaced apart fuel injection locations, i.e., via an upstream fuel stage 16 associated with a main combustion zone and a secondary fuel stage 18 downstream from the main combustion zone, reduces the production of NO_x by the combustor 10. For example, if a significant portion of fuel is injected at the secondary fuel stage 18, the amount of time that secondary combustion products are at a high temperature is reduced as compared to first combustion products, created by the fuel injected by the upstream fuel stage 16.

FIG. 2 illustrates another conventional combustor 110. During engine operation, acoustic pressure oscillations at undesirable frequencies can develop in the combustor 110 due to, for example, burning rate fluctuations inside the combustor 110. Such pressure oscillations can damage components in the combustor 110. To avoid such damage, one or more damping devices, such as a resonator 124, can be formed by attaching a resonator box 126 to an outer peripheral surface 128 of the combustor liner 122. As illustrated in FIG. 2, a plurality of resonators 124 can be aligned circumferentially about the liner 122. The resonators 124 can be tuned to provide damping at a single transverse frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of the drawings that show:

FIG. 1 is a cross-sectional side view of a conventional combustor used in a gas turbine engine;

FIG. 2 is a side view of a conventional combustor used in a gas turbine engine;

FIG. 3 is a cross-sectional side view of a gas turbine engine;

FIG. 4 is a cross-sectional side view of a resonator located at a downstream secondary fuel injection location of a combustor;

FIG. 5 is a cross-sectional side view of a resonator located at a downstream secondary fuel injection location of a combustor;

FIG. 6 is a cross-sectional side view of a resonator located at a downstream secondary fuel injection location and a downstream third fuel injection location of a combustor;

FIG. 7 is a cross-sectional end view of the resonator of FIG. 4; and

FIG. 8 is a plot of a frequency response function versus frequency for the resonator of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have recognized several limitations of the conventional resonator that is used to dampen pressure oscillations within a combustor of a gas turbine engine. For example, the inventors recognized that conventional resonators in a combustor take the form of additional components beyond those that are needed to direct and combust fluid in the combustion chamber. Based on this recognition, the present inventors developed a resonator using the existing components that direct and combust fluid in the combustion chamber, and thus eliminated the need for additional components.

The present inventors also recognized that conventional resonators in a combustor are limited to dampening one resonant frequency mode, per resonator design. Based on this recognition, the present inventors developed a resonator for a combustor, which simultaneously dampens a high frequency transverse mode and an intermediate frequency longitudinal mode, thereby reducing the number of required resonator designs to dampen multiple resonant frequency modes.

FIG. 3 illustrates a gas turbine engine 202 including a compressor 204 that generates compressed air which is passed through a diffuser 207 and into a casing 205 with a volume 214. The compressed air then enters a can-annular combustor 210, where the compressed air is mixed with a fuel from a primary fuel stage and is ignited. As illustrated in FIG. 3, the casing volume 214 encloses the combustor 210. A secondary fuel line 234 is directed to a secondary fuel stage 218 of the combustor 210, to inject fuel into the air/fuel mixture within the combustor 210 at the secondary fuel stage 218. Additionally, compressed air is injected into the combustor 210 at the secondary fuel stage 218. The ignited air/fuel mixture is subsequently passed to a turbine 206, to perform work, such as rotating a shaft 208 connecting the compressor 204 and the turbine 206, for example. As illustrated in FIG. 3, the combustor 210 includes a resonator 200 at the secondary fuel stage 218, to dampen multiple frequencies corresponding to resonant frequency modes of the combustor 210, as described below.

FIG. 4 illustrates the resonator 200, which includes the combustor 210 and a flow sleeve 212 that encloses the combustor 210. As further illustrated in FIG. 4, the combustor 210 includes the secondary fuel stage 218 located at a downstream secondary fuel injection location 246. The secondary fuel line 234 is located at the secondary fuel stage 218 and includes an outlet 236 positioned to inject fuel into an inlet 238 of a nozzle 217 to deliver fuel to a combustion chamber 240 of the combustor 210 through the nozzle 217.

Each nozzle 217, by itself, is sized to be effective as a transverse resonator, to dampen a transverse frequency corresponding to a resonant transverse mode combustion-induced vibrations of the combustor 210. In an exemplary embodiment, as illustrated in FIG. 4, a length 220 of the nozzle 217 is sized such that the nozzle is effective as the transverse resonator. In an exemplary embodiment, a ratio of the nozzle length to nozzle diameter may be in a range of 0.5-5.0, for example. However, the ratio of nozzle length to nozzle diameter is not limited to any specific range. In an exemplary embodiment, the nozzle 217 acts as a half-wave resonator in a transverse dimension, such that the length 220 is sized in order for an integral number of half-wavelengths of a transverse frequency to fit along the length 220, where the transverse frequency corresponds to a resonant transverse mode of the combustor 210. In another exemplary embodiment, as illustrated in FIG. 4, the nozzle 217 defines an opening 222, and a cross-sectional width 221 of the opening 222 is sized such that the nozzle is effective as the transverse resonator. In an exemplary embodiment, a ratio of the nozzle diameter to combustor diameter may be in a range of 0.01-0.1, for example. However, the ratio of the nozzle diameter to combustor diameter is not limited to any specific range. In another exemplary embodiment, the cross-sectional width 221, in addition to the nozzle length 220 and a volume within the nozzle 217 are sized such that the nozzle is effective as the transverse resonator. FIG. 5 illustrates an alternate resonator 200′ with a nozzle 217′ that is located at the downstream secondary fuel injection location 246 of the combustor 210. As illustrated in FIG. 5, the nozzle 217′ defines a conical opening 222′ with a reduced cross-sectional width 221′ toward an outlet 226′ of the nozzle 217′. In an exemplary embodiment, the conical opening may be angled within a range of 75-90 degrees, for example. However, the angle of the conical opening is not limited to any specific range. Although FIGS. 4-5 illustrate nozzles with cylindrical (FIG. 4) and conical (FIG. 5) shaped cross-sectional areas, the embodiments of the present invention is not limited to these arrangements and the nozzles may have any cross-sectional area arrangement, provided that the cross-sectional area is such that the nozzle is effective as the transverse resonator. In an exemplary embodiment, the nozzle 217 is sized to dampen a transverse frequency in a range of 2900-2950 Hz, for example, which corresponds to a resonant transverse mode of the combustor 210. However, this transverse frequency range is merely exemplary and the resonator of the present invention is not limited to dampening any specific transverse frequency range, since the design parameters (i.e. length, cross-sectional area, shape, volume, number of nozzles, etc) of the resonator nozzle can be adjusted such that the resonator dampens any desired transverse frequency range. In an exemplary embodiment, the number of nozzles 217 at the secondary fuel stage 218 may be within a range of 8-12 nozzles, for example. However, this range is merely exemplary and any number of nozzles may be used at the secondary fuel stage 218, provided that the resonator is effective as a transverse resonator.

The combination of the nozzle 217 and the casing volume 214 (FIG. 3) are effective as a longitudinal resonator, and the nozzle 217 and the volume 214 are sized in order for the longitudinal resonator to dampen a longitudinal frequency corresponding to a resonant longitudinal mode of the combustor 210. In an exemplary embodiment, the longitudinal frequency dampened by the longitudinal resonator may depend on the casing volume and/or on a longitudinal dimension within the casing volume, depending on the geometry of the casing and the target resonant longitudinal mode to be dampened. In an exemplary embodiment, the longitudinal frequency dampened by the longitudinal resonator may depend on a combination of the casing volume and the sum of all of nozzles within each combustor. In an exemplary embodiment, the casing volume 214 acts as a cavity and the nozzles 217 act as a neck of a Helmholtz resonator, for example. In order to be effective as the longitudinal resonator, the quantity of the nozzles 217 may be adjusted. In an exemplary embodiment, the number of nozzles 217 at the secondary fuel stage 218 may be within a range of 8-12 nozzles, for example. However, this range is merely exemplary and any number of nozzles may be used at the secondary fuel stage 218, provided that the resonator is effective as a longitudinal resonator. In an exemplary embodiment, the nozzle 217 and the casing volume 214 are sized to dampen a longitudinal frequency in a range of 50-150 Hz, for example, which corresponds to a resonant longitudinal mode of the combustor 210. However, this longitudinal frequency range is merely exemplary and the resonator of the present invention is not limited to dampening any specific longitudinal frequency range, since the parameter (i.e. number of nozzles) of the resonator nozzle and the volume of the casing can be adjusted during a design phase such that the resonator dampens any desired longitudinal frequency range.

FIG. 6 illustrates an alternate combustor 200″ including the nozzle 217 positioned at the secondary fuel stage 218, as with the combustor 200 of FIG. 4 discussed above. As with the combustor 200 of FIG. 4, the nozzle 217 of the combustor 200″ is sized to be effective as a transverse resonator at a first frequency that corresponds to a first resonant transverse mode of the combustor 210. However, the combustor 200″ further includes a third fuel stage 254 at a downstream third fuel injection location 252 that is downstream of the second fuel stage 218 at the downstream secondary fuel injection location 246. The combustor 200″ includes a second nozzle 219″ at the third fuel stage 254 that is sized to be effective as a transverse resonator at a second frequency that corresponds to a second resonant transverse mode of the combustor 210, where the second frequency is different than the first frequency and the second resonant transverse mode is different than the first resonant transverse mode. The second nozzle 219″ does not extend beyond an inner diameter of the combustion liner wall 230 of the combustor 210. In contrast, the nozzle 217 extends beyond the inner diameter of the combustion liner wall 230. Although FIG. 6 depicts the first nozzle 217 positioned at the secondary fuel stage 218 and extending beyond the inner diameter of the combustion liner wall 230, and the second nozzle 219″ positioned at the third fuel stage 254 and not extending beyond the inner diameter of the combustion liner wall 230, this arrangement is merely exemplary, and the nozzles at each of the second and third stages may all extend beyond the inner diameter of the combustion liner wall or may all not extend beyond the inner diameter of the combustion liner wall, or some combination thereof, for example. Additionally, although FIG. 6 depicts that one nozzle may be arranged at a secondary fuel stage and one nozzle may be arranged at a third fuel stage downstream of the secondary fuel stage, this is merely exemplary, as more than one nozzle may be arranged at each of the secondary or third fuel stages, and one or more nozzle(s) may be arranged at additional fuel stages downstream of the third fuel stage, for example. In an exemplary embodiment, the number of nozzles that are arranged at each of the second and third fuel stages may be within the range of 8-12 nozzles, for example. However, this range is merely exemplary and any number of nozzles may be used at each of the second and third stages, provided that the resonator is effective as a transverse resonator.

FIG. 7 illustrates an end view of the resonator 200 of FIG. 4 at the downstream secondary fuel injection location 246 and a plurality of nozzles 217, 219 arranged at the secondary fuel stage 218. The nozzles 217, 219 are arranged at the downstream second fuel injection location 246 with an angle 228 between adjacent nozzles 217, 219 in a plane transverse to the combustor longitudinal axis. In an exemplary embodiment, the angle 228 is selected such that the nozzles 217, 219 are effective as transverse and longitudinal resonators. In an exemplary embodiment, the angle may be within a range of 15-90 degrees, for example. However, the angle is not limited to any specific range. In an exemplary embodiment, the angle may be determined based on the specific transverse mode that needs to be dampened, for example. Although FIG. 7 illustrates two nozzles 217, 219 arranged at the secondary fuel stage 218, the embodiment of the present invention is not limited to this number of nozzles and any plurality of nozzles may be arranged at the secondary fuel stage, provided that the angle between adjacent nozzles is sized such that the nozzles are effective transverse and longitudinal resonators.

In an exemplary embodiment, the nozzles 217, 219 at the secondary fuel stage 218 may be individually sized (i.e. length, cross-sectional area, etc.) such that a first nozzle 217 is effective as a transverse resonator at a first frequency and a second nozzle 219 is effective as a transverse resonator at a second frequency that is different than the first frequency. For example, the nozzles 217, 219 may have different lengths and/or different cross-sectional areas, such that the nozzle 217 and the nozzle 219 are sized to be effective as transverse resonators at a respective first and second frequency. Although the above example discusses that two nozzles at the secondary fuel stage may be sized differently to be effective transverse resonators at two distinct frequencies, the embodiment of the present invention is not limited to this arrangement, and includes any plurality of nozzles at the secondary fuel stage being sized differently, to be effective transverse resonators at a plurality of distinct frequencies, for example. Additionally, the length and cross-sectional areas of the nozzles 217, 219 may be sized, in addition to the casing volume 214, to ensure that the desired longitudinal frequency is dampened.

FIG. 8 depicts a plot of the frequency response function (FRF) of the resonator 200 for a range of frequencies during operation of the combustor 210. As illustrated in FIG. 8, the resonator 200 is effective to simultaneously dampen a transverse frequency 242 corresponding to a resonant transverse mode of the combustor 210 and to dampen a longitudinal frequency 244 corresponding to a resonant longitudinal mode of the combustor 210. The transverse frequency 242 dampened by the nozzle 217 corresponds to a high frequency mode with a range of approximately 2900-2950 Hz, and is based on the sizing characteristics (i.e. length, opening, cross-sectional area, etc) of the nozzle 217. The FRF 248 of the resonator 200 at the transverse frequency 242 is based on the combination of the individual dampening effects of each nozzle 217 at the secondary fuel stage 218. Although the transverse frequency 242 discussed above lies within a sample range of 2900-2950 Hz, this range is merely exemplary, may include a wider range of 1200-4500 Hz and the embodiments of the present invention is not limited to these ranges and may include any resonant transverse mode of the combustor, provided that the nozzles can be sized to dampen the transverse frequency corresponding to the resonant transverse mode.

As further illustrated in FIG. 8, the longitudinal frequency 244 is an intermediate frequency mode with a range of approximately 50-150 Hz. The FRF 250 of the resonator 200 at the longitudinal frequency 244, and the range of the longitudinal frequency mode 244, are based on the volume 214 of the casing 205 in combination with the characteristics of the nozzles 217, 219 in each combustor 210 of the engine 202. The number of nozzles 217 at the secondary fuel stage 218 may affect the longitudinal frequency 244, such as the center frequency within the range of the longitudinal frequency 244, for example. Although the longitudinal frequency mode 244 discussed above lies within a sample range of 50-150 Hz, this range is merely exemplary, may include a wider range of 50-400 Hz and the embodiments of the present invention is not limited to these ranges and may include any resonant longitudinal mode of the combustor, provided that the casing volume and the nozzles are sized to dampen the longitudinal frequency corresponding to the resonant longitudinal mode.

In the above embodiment, the resonator 200 dampens a wider range of the longitudinal frequency 244 (100 Hz) than the range of the transverse frequency 242 (50 Hz). Since the range of the dampened transverse frequency 242 for each nozzle design is relatively narrow, more than one nozzle design may be employed in the resonator, to increase the total range of dampened transverse frequencies. As previously discussed, multiple nozzle designs may be provided, where each nozzle design is configured to dampen a respective transverse frequency range.

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. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.

Claims

1. A gas turbine engine comprising:

a combustor;

a casing enclosing the combustor and defining a volume; and

a secondary fuel stage for delivering fuel to the combustor;

wherein the secondary fuel stage comprises a nozzle sized to be effective as a transverse resonator;

and wherein the nozzle and the volume of the casing are configured to be effective as a longitudinal resonator.

2. The gas turbine engine of claim 1, wherein a length of the nozzle is selected to damp vibrations of a selected frequency.

3. The gas turbine engine of claim 1, wherein the nozzle defines an opening, and wherein a cross-sectional width of the opening of the nozzle is selected to damp vibrations of a selected frequency.

4. The gas turbine engine of claim 3, wherein the nozzle is conical with a reduced cross-sectional width toward an outlet of the nozzle.

5. The gas turbine engine of claim 1, wherein a plurality of nozzles are arranged at the secondary fuel stage and wherein an angle between adjacent nozzles in a plane transverse to a longitudinal axis of the combustor is selected so that the secondary fuel stage is effective to damp a selected transverse vibration mode.

6. The gas turbine engine of claim 1, wherein the secondary fuel stage comprises a first nozzle sized to be effective as a transverse resonator at a first frequency and a second nozzle sized to be effective as a transverse resonator at a second frequency different than the first frequency.

7. The gas turbine engine of claim 1, wherein the secondary fuel stage comprises a first nozzle sized to be effective as a transverse resonator at a first frequency and wherein a third fuel stage downstream of the secondary fuel stage comprises a second nozzle sized to be effective as a transverse resonator at a second frequency different than the first frequency.

8. The gas turbine engine of claim 1, wherein the nozzle extends beyond an inner diameter of a combustion liner wall of the combustor.

9. The gas turbine engine of claim 1, wherein the nozzle does not extend beyond an inner diameter of a combustion liner wall of the combustor.

10. The gas turbine engine of claim 1, wherein a ratio of a length to a diameter of the nozzle is in a range of 0.5-5.0.

11. The gas turbine engine of claim 1, wherein a ratio of a diameter of the nozzle to a diameter of the combustor is in a range of 0.01-0.1.

12. In a gas turbine engine comprising a casing defining a volume enclosing a combustor, a resonator located at a downstream secondary fuel injection location of the combustor, said resonator comprising:

a fuel line outlet positioned to inject fuel into an inlet of a nozzle effective to deliver fuel to the combustor through the nozzle;

wherein the nozzle is configured to be effective as a transverse resonator for transverse vibrations in a range of 1200-4500 Hz;

and wherein the nozzle and the volume of the casing enclosing the combustor are configured to be effective as a longitudinal resonator for longitudinal vibrations in a range of 50-150 Hz.

13. The resonator of claim 12, wherein a ratio of a length to a diameter of the nozzle is in a range of 0.5-5.0.

14. The resonator of claim 12, wherein a ratio of a diameter of the nozzle to a diameter of the combustor is in a range of 0.01-0.1.

15. The resonator of claim 12, wherein a plurality of nozzles are arranged at the downstream secondary fuel injection location and wherein an angle between adjacent nozzles in a plane transverse to a longitudinal axis of the combustor is selected so to damp a selected transverse vibration mode.

16. The resonator of claim 12, wherein the nozzle extends beyond an inner diameter of a combustion liner wall of the combustor.

17. The resonator of claim 12, wherein the nozzle does not extend beyond an inner diameter of a combustion liner wall of the combustor.

18. In a gas turbine engine comprising a casing defining a volume and a can-annular combustor disposed within the casing volume, the improvement comprising:

a plurality of nozzles formed in a wall of the combustor to define a secondary fuel injection location;

a fuel outlet disposed proximate an inlet of each nozzle for delivering a secondary fuel into the combustor through the nozzles;

wherein the nozzles are configured to be effective as a resonator to dampen a transverse frequency mode of pressure oscillations developed within the combustor during operation of the engine; and

wherein the nozzle and the casing volume are jointly configured to be effective as a resonator to dampen a longitudinal frequency mode of the pressure oscillations.

19. The gas turbine engine of claim 18, further comprising a first of the nozzles configured differently than a second of the nozzles to be effective at different respective frequencies.

20. The gas turbine engine of claim 18, further comprising:

wherein the nozzles are configured to be effective to damp transverse vibrations in a range of 1200-4500 Hz;

and the nozzles and the casing volume are configured to be effective to damp longitudinal vibrations in a range of 50-150 Hz.