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research-article

The effect of fuel staging on the structure and instability characteristics of swirl-stabilized flames in a lean premixed multi-nozzle can combustor

[+] Author and Article Information
Janith Samarasinghe

Center for Combustion, Power and Propulsion, The Pennsylvania State University, University Park, PA 16802; GE Global Research, 1 Research Circle, Niskayuna, NY 12309
janith.samarasinghe@ge.com

Wyatt Culler

Center for Combustion, Power and Propulsion, The Pennsylvania State University, University Park, PA 16802
wrc5047@psu.edu

Bryan D. Quay

Center for Combustion, Power and Propulsion, The Pennsylvania State University, University Park, PA 16802
bdq100@psu.edu

Domenic Santavicca

Center for Combustion, Power and Propulsion, The Pennsylvania State University, University Park, PA 16802
das8@psu.edu

Jacqueline O'Connor

Center for Combustion, Power and Propulsion, The Pennsylvania State University, University Park, PA 16802
jxo22@engr.psu.edu

1Corresponding author.

ASME doi:10.1115/1.4037461 History: Received July 01, 2017; Revised July 03, 2017

Abstract

Fuel staging is a commonly used strategy in the operation of gas turbine engines. In multi-nozzle combustor configurations, this is achieved by varying fuel flow rate to different nozzles. The effect of fuel staging on flame structure and self-excited instabilities is investigated in a research can combustor employing five swirl-stabilized, lean-premixed nozzles. At an operating condition where all nozzles are fueled equally and the combustor undergoes a self-excited instability, fuel staging successfully suppresses the instability: both when overall equivalence ratio is increased by staging as well as when overall equivalence ratio is kept constant while staging. Increased fuel staging changes the distribution of time-averaged heat release rate in the regions where adjacent flames interact and reduces the amplitudes of heat release rate fluctuations in those regions. Increased fuel staging also causes a breakup in the monotonic phase behavior that is characteristic of convective disturbances that travel along a flame. In particular, heat release rate fluctuations in the middle flame and flame-flame interaction region are out-of-phase with those in the outer flames, resulting in a cancellation of the global heat release rate oscillations. The Rayleigh integral distribution within the combustor shows that during a self-excited instability, the regions of highest heat release rate fluctuation are in phase-with the combustor pressure fluctuation. When staging fuel is introduced, these regions fluctuate out-of-phase with the pressure fluctuation, further illustrating that fuel staging suppresses instabilities through a phase cancellation mechanism.

Copyright (c) 2017 by ASME
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