System and method for reducing combustion dynamics in a turbomachine

Abstract

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.

Description

BACKGROUND OF THE INVENTION[0001]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.[0002]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) ...

AI Technical Summary

Benefits of technology

[0006]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.

Problems solved by technology

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.

More specifically, fluctuations in fuel-air ratio are known to cause combustion dynamics that lead to 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.

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