RESONATOR FOR DAMPING ACOUSTIC FREQUENCIES IN COMBUSTION SYSTEMS BY OPTIMIZING IMPINGEMENT HOLES AND SHELL VOLUME

Abstract

A resonator in a combustor of a gas turbine comprises a flow sleeve defining an air path to provide air flow to a combustion chamber of the combustor, and one or more impingement holes disposed on the flow sleeve tuned to a damping frequency.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser. No. 15/410,109, entitled “FLOW CONDITIONER TO REDUCE COMBUSTION DYNAMICS IN A COMBUSTION SYSTEM,” filed Jan. 19, 2017, and co-pending U.S. patent application Ser. No. ______, entitled “DEVICE TO CORRECT FLOW NON-UNIFORMITY WITHIN A COMBUSTION SYSTEM,” which are incorporated herein by reference.

BACKGROUND

Combustors, such as those used in industrial gas turbines, for example, mix compressed air with fuel and expel high temperature, high pressure gas downstream. The energy stored in the gas is then converted to work as the high temperature, high pressure gas expands in a turbine, for example, thereby turning a shaft to drive attached devices, such as an electric generator to generate electricity.

As the air/fuel mixture combusts, the hot gas that is generated creates fluctuations in pressure. These pressure fluctuations at certain frequencies (e.g., 1-1000 Hz) create acoustic pressures through the system. Accordingly, the combustion system is susceptible to High Cycle Fatigue (HCF) resulting from these combustion dynamics. The inability to account for the frequency of oscillation will jeopardize the structural integrity of the combustion system which may lead to a catastrophic failure.

There are known ways of preventing the excitation of natural frequency within the system. Acoustic pressure fluctuations that can generate natural frequencies may be reduced by redesigning the hardware, changing air splits, or adding external resonators to the system. However, in large applications such as an industrial gas turbine, for example, this can result in adding significant cost or reduction of the combustion system performance as extensive time for tests and modifications are needed. Additionally, external resonators for this purpose can reduce the combustor performance as the resonator will need air for damping. The air will be taken away from combustion, thereby decreasing the efficiency of the combustion. Such may result in increased emission levels, metal temperature, and thermal stresses, all of which will affect the life and performance of the structure of the system.

BRIEF SUMMARY

In one embodiment of the invention, a combustor of a gas turbine comprises a combustion chamber in which mixture of air and fuel is combusted, a flow sleeve defining an air path to provide air flow to the combustion chamber, and one or more impingement holes disposed on the flow sleeve tuned to a damping frequency.

In another embodiment of the invention, a resonator in a combustor of a gas turbine comprises a flow sleeve defining an air path to provide air flow to a combustion chamber of the combustor, and one or more impingement holes disposed on the flow sleeve tuned to a damping frequency.

In yet another embodiment, a method of damping acoustic frequencies in a combustor of a gas turbine comprises the steps of providing air flow to a combustion chamber through an air path defined by a flow sleeve to form an air and fuel mixture in the combustion chamber, combusting the air and fuel mixture in the combustion chamber, and generating at least one damping frequency via one or more impingement holes disposed on the flow sleeve tuned to the at least one damping frequency to damp acoustic frequencies generated by the combusting.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a combustion system in an exemplary gas turbine, according to an example embodiment.

FIG. 2 shows a sectional view of a combustor, according to an example embodiment.

FIG. 3, shows a sectional view of a resonator, according to an example embodiment.

FIG. 4 shows a schematic diagram of a resonator, according to an example embodiment.

FIGS. 5A and 5B show exemplary shapes and sizes of an impingement hole, according to example embodiments.

FIG. 6 is a schematic diagram of a resonator, according to another example embodiment.

DETAILED DESCRIPTION

Various embodiments of an acoustic resonator in a combustion system are described. It is to be understood, however, that the following explanation is merely exemplary in describing the devices and methods of the present disclosure. Accordingly, any number of reasonable and foreseeable modifications, changes, and/or substitutions are contemplated without departing from the spirit and scope of the present disclosure.

FIG. 1 shows combustor 10 according to an exemplary embodiment. For purposes of explanation only, the combustor 10 is shown in FIG. 1 as applied to an industrial gas turbine 20. However, combustors of other applications may be applied without departing from the scope of the present invention. For purposes of explanation and consistency, like reference numbers are directed to like components in the figures.

As shown in FIG. 1, air to be supplied to the combustor 10 is received through air intake section 30 of the gas turbine 20 and is compressed in compression section 40. The compressed air is then supplied to headend 50 through air path 60. The air is mixed with fuel and combusted at the tip of nozzles 70 and the resulting high temperature, high pressure gas is supplied downstream. In the exemplary embodiment shown in FIG. 1, the resulting gas is supplied to turbine section 80 where the energy of the gas is converted to work by turning shaft 90 connected to turbine blades 95.

As can be seen in FIG. 1, the entire structure is connected to the combustor 10 and therefore the acoustic frequencies caused by the generation of the gas resonates through the entire system. Therefore, controlling the generation of the acoustic frequencies will have a lasting effect on the operation, performance, and longevity of the entire system. Impact of the frequency is not only limited to frequencies that are resonating throughout the engine. The impact of the frequency on the combustion system, which takes place mainly in the combustor when high amplitude frequencies are generated, cause damage to the combustor system. This will result in the necessity to power down the engine to make repairs and thus loss of revenue. Another scenario is when an external damper is used on the combustor to reduce dynamics. In this case, the damper will most likely reduce the combustor performance as resonators will require air to operate. This air will be taken away from combustion resulting in higher emission and thus lower performance. Additionally, adding resonators will reduce the outage cycle due to high thermal stresses on the resonator.

FIG. 2 is a sectional view of an exemplary combustor 10. Combustor 10 includes one or more fuel nozzles 70 in the headend 50. It is to be understood that there may be one or more combustors 10 in any given gas turbine. Liner 150 and transition piece 160 channels the resulting high pressure, hot gas towards the turbine section 80.

FIG. 3 is a sectional view of a resonator according to an exemplary embodiment. As shown in FIG. 3, flow sleeve 100 is encased by shell 110 forming shell volume 120. Flow sleeve 100 is formed around liner 150 and transition piece 160 such that air flows in the space formed between the flow sleeve 100 and liner 150 and transition piece 160. Flow sleeve 100 has formed thereon one or more impingement holes 130 through which compressed, relatively hot air flows. Accordingly, impingement holes 130 and shell volume 120 forms a Helmholtz resonator (i.e., resonator 140). Utilizing the shell volume 120 and the impingement holes 130 as a Helmholtz resonator eliminates the need for designing an external resonator that reduce the combustor performance by siphoning air flow that would normally flow through the combustion system.

FIG. 4 is a schematic diagram of resonator 140 formed by the shell volume 120 and impingement holes 130 according to an exemplary embodiment. The shell volume 120 acts as a compliance or volume of a Helmholtz resonator whereas the impingement holes 130 simulate the neck of the Helmholtz resonator.

Resonator 140 can be optimized by adjusting the size, thickness, shape, and locations of the impingement holes 130. Impingement holes 130 on the flow sleeve 100 that forms resonator 140 can damp longitudinal waves with wavelength that stretches to the air path location between flow sleeve 100 and liner 150 and flow sleeve 100 and transition piece 160. In particular, mid-range frequencies (e.g., between 20-200 Hz) may be dampened by utilizing existing hardware in the combustor 10 according to the exemplary embodiment. However, other frequencies may be targeted without departing from the scope of the present invention. Further, multiple impingement holes 130 may be formed and designed to target several frequencies at once.

Air flow that passes through the impingement holes 130 can be controlled to improve damping. For example, different sizes and shapes of the impingement holes 130 may be used to target different frequencies with different damping capabilities. FIGS. 5A and 5B show exemplary shapes and sizes of impingement hole 130. The size of hole 110 may be varied by adjusting diameter (D) and/or thickness (T). For instance, a cylindrical shape in FIG. 5A produces higher damping than a trapezoidal shape in FIG. 5B as the neck effective length increases. Further, changes in the angle of the trapezoid in FIG. 5B causes further shifts in the acoustic frequency. While only two exemplary shapes are shown in FIGS. 5A and 5B, other shapes may be used without departing from the scope of the present invention.

FIG. 6 is a schematic diagram of an exemplary embodiment of resonator 140. Unstable frequencies can be damped by chaining impingement holes 130 and 130′ having different diameter, thickness and/or shape, for example. Additionally, impingement holes 130″ may be placed on or close to an anti-node of the mode-shape of the targeted wave and its frequency.

Some of the advantages of the exemplary embodiments include: reduction of the combustion dynamics or pressure waves amplitude so the life of hardware can be extended, reduced or eliminated combustion dynamics for frequencies between 20-200 Hz and thus extending the life of the hardware, and utilization of existing hardware within the combustion system, thus eliminating the need to add external resonators for low to mid range frequencies or the need to change the design of the hardware to minimize the effect of the combustion dynamics and to reduce the acoustic pressure fluctuation.

It will also be appreciated that this disclosure is not limited to combustion systems in industrial gas turbines. For example, combustion systems in aero gas turbines and gas turbines in general can also realize advantages of the present disclosure. Further, the shapes, sizes, and thicknesses of the impingement holes are not limited to those disclosed herein. For example, impingement holes in the shape of a square, rectangle, triangle, and other polygonal structures, such as pentagon, hexagon, and octagon to name a few examples can also realize the advantages of the present disclosure. Additionally, any combination of impingement holes having different size, thickness, and shape may be chained together to adjust the frequency of the resonator without departing from the scope of the present invention.

The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Moreover, the above advantages and features are provided in described embodiments, but shall not limit the application of the claims to processes and structures accomplishing any or all of the above advantages.

Additionally, the section headings herein are provided for consistency with the suggestions under 37 CFR 1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the invention(s) set out in any claims that may issue from this disclosure. Further, a description of a technology in the “Background” is not to be construed as an admission that technology is prior art to any invention(s) in this disclosure. Neither is the “Brief Summary” to be considered as a characterization of the invention(s) set forth in the claims found herein. Furthermore, any reference in this disclosure to “invention” in the singular should not be used to argue that there is only a single point of novelty claimed in this disclosure. Multiple inventions may be set forth according to the limitations of the multiple claims associated with this disclosure, and the claims accordingly define the invention(s), and their equivalents, that are protected thereby. In all instances, the scope of the claims shall be considered on their own merits in light of the specification, but should not be constrained by the headings set forth herein.

Claims

1. A combustor of a gas turbine, comprising:

a combustion chamber in which mixture of air and fuel is combusted;

a flow sleeve defining an air path to provide air flow to the combustion chamber; and

one or more impingement holes disposed on the flow sleeve tuned to a damping frequency.

2. The combustor of claim 1, wherein the one or more impingement holes and a shell volume of the combustor forms a Helmholtz resonator tuned to the damping frequency.

3. The combustor of claim 1, wherein at least one of the one or more impingement holes is disposed at an anti-node location within the combustor.

4. The combustor of claim 1, wherein the one or more impingement holes are cylindrical.

5. The combustor of claim 1, wherein the one or more impingement holes are polygonal.

6. The combustor of claim 1, wherein the one or more impingement holes have different shapes.

7. The combustor of claim 1, wherein the one or more impingement holes have different sizes.

8. A resonator in a combustor of a gas turbine, comprising:

a flow sleeve defining an air path to provide air flow to a combustion chamber of the combustor; and

one or more impingement holes disposed on the flow sleeve tuned to a damping frequency.

9. The resonator of claim 8, wherein the one or more impingement holes and a shell volume of the combustor forms a Helmholtz resonator tuned to the damping frequency.

10. The resonator of claim 8, wherein at least one of the one or more impingement holes is disposed at an anti-node location within the combustor.

11. The resonator of claim 8, wherein the one or more impingement holes are cylindrical.

12. The resonator of claim 8, wherein the one or more impingement holes are polygonal.

13. The resonator of claim 8, wherein the one or more impingement holes have different shapes.

14. The resonator of claim 8, wherein the one or more impingement holes have different sizes.

15. A method of damping acoustic frequencies in a combustor of a gas turbine, comprising the steps of:

providing air flow to a combustion chamber through an air path defined by a flow sleeve to form an air and fuel mixture in the combustion chamber;

combusting the air and fuel mixture in the combustion chamber; and

generating at least one damping frequency via one or more impingement holes disposed on the flow sleeve tuned to the at least one damping frequency to damp acoustic frequencies generated by the combusting.

16. The method of claim 15, wherein the one or more impingement holes and a shell volume of the combustor forms a Helmholtz resonator tuned to the damping frequency.

17. The method of claim 15, wherein at least one of the one or more impingement holes is disposed at an anti-node location within the combustor.

18. The method of claim 15, wherein the one or more impingement holes have different shapes.

19. The method of claim 15, wherein the one or more impingement holes have different sizes.

20. The method of claim 15, wherein the one or more impingement holes are cylindrical or polygonal.