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.
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.
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.
As shown in
As can be seen in
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.
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.
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.