SYSTEM AND METHOD FOR REDUCING COMBUSTION DYNAMICS IN A TURBOMACHINE
A turbomachine includes a combustion chamber, and at least one pre-mixer mounted to the combustion chamber. The at least one pre-mixer includes a main body having a first end portion that extends to a second end portion. The first end portion is configured to receive an amount of fuel and an amount of air and the second end portion defines an exit plane from which a fuel-air mixture discharges into the combustion chamber. The turbomachine also includes a combustion dynamics reduction system operatively coupled to the at least one pre-mixer. The combustion dynamics reduction system includes at least one of a boundary layer perturbation mechanism and an acoustic wave introduction system which disrupt a flow pattern of the fuel-air mixture within the at least one pre-mixer.
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The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a system and method for reducing combustion dynamics in a turbomachine.
Combustion dynamics are a phenomenon in gas turbomachines utilizing lean pre-mixed combustion. Combustion dynamics include low-frequency, longitudinal dynamics and high-frequency screech caused by the excitation of radial and azimuthal modes of the combustion chambers by the swirling flames. Both the low and high frequencies include a combustion field component and an acoustic component, that pass along the combustor during combustion. Under certain operating conditions, the combustion component and the acoustic component couple to create both low and high frequency dynamic fields. The low and high frequency dynamic fields have a negative impact on various turbomachine components. More specifically, dynamic fields passing from the combustor may lead to high cycle fatigue (HCF) for downstream turbomachine components.
To address this problem, turbomachines are operated at less than optimum levels, i.e., certain operating conditions are avoided in order to avoid circumstances that are conducive to combustion screech. While effective at reducing combustion dynamics, avoiding these operating levels restricts an overall operating envelope of the turbomachine.
Another approach to the problem of combustion dynamics is to modify combustor input conditions. More specifically, fluctuations in fuel-air ratio are known to cause combustion dynamics that lead to combustion screech. Creating perturbations in the fuel-air mixture by changing fuel flow rate can disengage the combustion field from the acoustic field to suppress combustion screech. While both of the above approaches are effective at reducing combustion dynamics, avoiding various operating levels restricts an overall operating envelope of the turbomachine while manipulating the fuel-air ratio requires a coupled control scheme and may also lead to less than efficient combustion.
BRIEF DESCRIPTION OF THE INVENTIONAccording to one aspect of the invention, a turbomachine includes a combustion chamber, and at least one pre-mixer mounted to the combustion chamber. The at least one pre-mixer includes a main body having a first end portion that extends to a second end portion. The first end portion is configured to receive an amount of fuel and an amount of air and the second end portion defines an exit plane from which a fuel-air mixture discharges into the combustion chamber. The turbomachine also includes a combustion dynamics reduction system operatively coupled to the at least one pre-mixer. The combustion dynamics reduction system includes at least one of a boundary layer perturbation mechanism and an acoustic wave introduction system which disrupt a flow pattern of the fuel-air mixture within the at least one pre-mixer.
According to another aspect of the invention, a method of reducing combustion dynamics in a turbomachine includes directing a fuel-air mixture through a pre-mixer into a combustion chamber, and reducing combustion dynamics by disrupting a flow pattern of the fuel-air mixture within the at least one pre-mixer.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTIONThe terms “axial” and “axially” as used in this application refer to directions and orientations extending substantially parallel to a center longitudinal axis of a centerbody of a burner tube assembly. The terms “radial” and “radially” as used in this application refer to directions and orientations extending substantially orthogonally to the center longitudinal axis of the centerbody. The terms “upstream” and “downstream” as used in this application refer to directions and orientations relative to an axial flow direction with respect to the center longitudinal axis of the centerbody.
With initial reference to
As best shown in
During operation, air flows through compressor 4, is compressed, and passed to combustor 6 and, more specifically, to injector assemblies 38 and 39. At the same time, fuel is passed to injector assemblies 38 and 39 to mix with the compressed air to form a combustible mixture. The combustible mixture is channeled to combustion chamber 48 and ignited to form combustion gases. The combustion gases are then channeled to turbine 10. Thermal energy from the combustion gases is converted to mechanical rotational energy that is employed to drive compressor/turbine shaft 12.
More specifically, turbine 10 drives compressor 4 via compressor/turbine shaft 12 (shown in
As best shown in
Reference will now be made to
Reference will now be made to
As further shown in
At this point it should be understood that the present invention provides a system for suppressing combustion screech in a turbomachine by creating a boundary layer disruption within injection nozzles associated with a particular combustor or providing a system to disrupt a base portion of the flame directly at an exit of a particular injection nozzle. By creating time varying changes within the injection nozzle assemblies, combustion screech can be significantly reduced if not eliminated. Furthermore, eliminating combustion screech in this manner allows operators to take advantage of all turbomachine operating ranges. In addition, by suppressing combustion screech at the source, i.e. within the nozzle assembly and/or combustion chamber, and development of a high frequency dynamic field is eliminated before having a chance to propagate through turbomachine components.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
Claims
1. A turbomachine comprising:
- a combustion chamber;
- at least one pre-mixer mounted to the combustion chamber, the at least one pre-mixer including a main body including a first end portion that extends to a second end portion, the first end portion being configured to receive an amount of fuel and an amount of air and the second end portion defining an exit plane from which a fuel-air mixture discharges into the combustion chamber; and
- a combustion dynamics reduction system operatively coupled to the at least one pre-mixer, the combustion dynamics reduction system including at least one of a boundary layer perturbation mechanism and an acoustic wave introduction system that disrupt a flow pattern of the fuel-air mixture within the at least one pre-mixer.
2. The turbomachine according to claim 1, wherein the combustion dynamics reduction system includes a boundary layer perturbation mechanism, the boundary layer perturbation mechanism including one of an air/inert injection system operatively coupled to the pre-mixer and mechanical member mounted in the at least one pre-mixer.
3. The turbomachine according to claim 2, wherein the boundary layer perturbation mechanism includes an air/inert injection system, the air/inert injection system including an inlet for receiving an amount of air/inert and an outlet for releasing the amount of air/inert.
4. The turbomachine according to claim 3, wherein the outlet is positioned in the pre-mixer.
5. The turbomachine according to claim 4, wherein the outlet is positioned adjacent the exit plane.
6. The turbomachine according to claim 2, wherein the boundary layer perturbation system includes a mechanical member mounted in the pre-mixer.
7. The turbomachine according to claim 6, wherein the mechanical member comprises at least one protrusion mounted in the pre-mixer, the at least one protrusion modifying the flow pattern of the fuel-air mixture.
8. The turbomachine according to claim 7, wherein the at least one protrusion is mounted adjacent the exit plane.
9. The turbomachine according to claim 1, wherein the combustion dynamics reduction system comprises an acoustic wave introduction system, the acoustic wave introduction system including an acoustic driver operatively connected to the at least one pre-mixer.
10. The turbomachine according to claim 9, wherein the combustion dynamics reduction system includes a fluid introduction system, the fluid introduction system being operatively connected to the at least one pre-mixer.
11. A method of reducing combustion dynamics in a turbomachine comprising:
- directing a fuel-air mixture through a pre-mixer into a combustion chamber, the pre-mixer; and
- reducing combustion dynamics by disrupting a flow pattern of the fuel-air mixture within the at least one pre-mixer.
12. The method of claim 11, wherein reducing combustion dynamics comprises perturbing a boundary layer of the fuel-air mixture passing from the pre-mixer.
13. The method of claim 12, wherein perturbing a boundary layer of the fuel-air mixture comprises injecting air into the fuel-air mixture at an exit plane of the pre-mixer.
14. The method of claim 12, wherein perturbing a boundary layer of the fuel-air mixture comprises passing the fuel-air mixture over at least one mechanical member arranged in the pre-mixer.
15. The method of claim 14, wherein passing the fuel-air mixture over at least one mechanical member arranged in the pre-mixer comprises passing the fuel-air mixture over at least one protrusion mounted in the pre-mixer, the at least one protrusion modifying a flow pattern of the fuel-air mixture.
16. The method of claim 15, wherein passing the fuel-air mixture over at least one protrusion comprises passing the fuel-air mixture over the at least one protrusion arranged at an exit plane of the pre-mixer.
17. The method of claim 11, wherein reducing combustion dynamics comprises perturbing a base portion of a flame at an exit plane of the pre-mixer.
18. The method of claim 17, wherein perturbing the base portion of the flame comprises introducing an acoustic wave into the pre-mixer.
19. The method of claim 18, wherein introducing the acoustic wave into the pre-mixer comprises varying a frequency of the acoustic wave.
20. The method of claim 18, further comprising:
- introducing a fluid into the pre-mixing to further perturb the base portion of the flame.
Type: Application
Filed: Jan 28, 2013
Publication Date: May 30, 2013
Applicant: GENERAL ELECTRIC COMPANY (Schenectady, NY)
Inventors: Kapil Kumar Singh (Rexford, NY), Vasanth Srinivasa Kothnur (Clifton Park, NY), Fei Han (Clifton Park, NY)
Application Number: 13/751,301
International Classification: F23R 3/28 (20060101);