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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Experimental Investigation of the Nonlinear Response of Swirl-Stabilized Flames to Equivalence Ratio Oscillations

[+] Author and Article Information
Kyu Tae Kim, Bryan D. Quay, Domenic Santavicca

Center for Advanced Power Generation, Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802

Jong Guen Lee1

Center for Advanced Power Generation, Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802jxl145@psu.edu

1

Corresponding author.

J. Eng. Gas Turbines Power 133(2), 021502 (Oct 27, 2010) (8 pages) doi:10.1115/1.4001999 History: Received April 12, 2010; Revised April 19, 2010; Published October 27, 2010; Online October 27, 2010

The nonlinear response of a swirl-stabilized flame to equivalence ratio oscillations was experimentally investigated in an atmospheric-pressure, high-temperature, lean-premixed model gas turbine combustor. To generate high-amplitude equivalence ratio oscillations, fuel was modulated using a siren-type modulating device. The mixture ratio oscillations at the inlet of the combustion chamber were measured by the infrared absorption technique, and the flame’s response, i.e., the fluctuation in the flame’s rate of heat release, was estimated by CH chemiluminescence emission intensity. Phase-resolved CH chemiluminescence images were taken to characterize the dynamic response of the flame. Results show that the amplitude and frequency dependence of the flame’s response to equivalence ratio oscillations is qualitatively consistent with the flame’s response to inlet velocity oscillations. The underlying physics of the nonlinear response of the flame to equivalence ratio oscillations, however, is associated with the intrinsically nonlinear dependence of the heat of reaction and burning velocity on the equivalence ratio. It was found that combustion cannot be sustained under conditions of high-amplitude equivalence ratio oscillations. Lean blowoff occurs when the normalized amplitude of the equivalence ratio oscillation exceeds a threshold value. The threshold value is dependent on the mean equivalence ratio and modulation frequency.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Mechanism of the flame response to (a) velocity perturbations and (b) equivalence ratio perturbations (12)

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Figure 2

Schematic of a swirl-stabilized, lean-premixed, gas turbine combustor. Dimensions in millimeters. (a) Side view (mixing section and quartz combustor section), (b) schematic drawing of experimental setup for equivalence ratio measurements.

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Figure 3

(a) Normalized CH∗ chemiluminescence intensity and (b) phase of the flame transfer function at a modulation frequency of 100 Hz. Inlet conditions: Tin=200°C, Vmean=60 m/s, and Φmean=0.60.

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Figure 4

Instantaneous CH∗ chemiluminescence image at a modulation frequency of 100 Hz and Φ′/Φmean=4.3%. Inlet conditions: Tin=200°C, Vmean=60 m/s, and Φmean=0.55.

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Figure 5

(a) Normalized CH∗ chemiluminescence intensity and (b) phase of the flame transfer function at a modulation frequency of 150 Hz. Inlet conditions: Tin=200°C, Vmean=60 m/s, and Φmean=0.60.

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Figure 6

Dependence of the normalized CH∗ chemiluminescence intensity fluctuation on the modulation frequency. Inlet conditions: Tin=200°C, Vmean=60 m/s, and Φmean=0.60.

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Figure 7

Dependence of the response of a flame upon mean equivalence ratio at a modulation frequency of 100 Hz. Inlet conditions: Tin=200°C, Vmean=60 m/s, and Φmean=0.60,0.65.

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Figure 8

Dependence of the response of a flame upon mean equivalence ratio at a modulation frequency of 150 Hz. Inlet conditions: Tin=200°C, Vmean=60 m/s, and Φmean=0.60,0.65.

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Figure 9

(a) Gain and (b) phase of the flame transfer function in frequency domain. Inlet conditions: Tin=200°C, Vmean=60 m/s, Φmean=0.60, and Φ′/Φmean=1%.

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Figure 10

Phase-resolved CH∗ chemiluminescence imaging during a period of oscillation at a modulation frequency of 200 Hz and amplitudes of (a) Φ′/Φmean=2.2% and (b) Φ′/Φmean=3.2%. Inlet conditions: Tin=200°C, Vmean=60 m/s, and Φmean=0.60.

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Figure 11

Time signal of CH∗ chemiluminescence intensity at a modulation frequency of 200 Hz and amplitude of Φ′/Φmean=2.2%. Inlet conditions: Tin=200°C, Vmean=60 m/s, and Φmean=0.60.

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