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

# Characterization of Forced Flame Response of Swirl-Stabilized Turbulent Lean-Premixed Flames in a Gas Turbine Combustor

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

Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802

Jong Guen Lee1

Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802jxl145@psu.edu

1

Corresponding author.

J. Eng. Gas Turbines Power 132(4), 041502 (Jan 19, 2010) (8 pages) doi:10.1115/1.3204532 History: Received March 21, 2009; Revised March 30, 2009; Published January 19, 2010; Online January 19, 2010

## Abstract

Flame transfer function measurements of turbulent premixed flames are made in a model lean-premixed, swirl-stabilized, gas turbine combustor. $OH∗$, $CH∗$, and $CO2∗$ chemiluminescence emissions are measured to determine heat release oscillation from a whole flame, and the two-microphone technique is used to measure inlet velocity fluctuation. 2D $CH∗$ chemiluminescence imaging is used to characterize the flame shape: the flame length $(LCH∗ max)$ and flame angle $(α)$. Using $H2$-natural gas composite fuels, $XH2=0.00–0.60$, a very short flame is obtained and hydrogen enrichment of natural gas is found to have a significant impact on the flame structure and flame attachment points. For a pure natural gas flame, the flames exhibit a “V” structure, whereas $H2$-enriched natural gas flames have an “M” structure. Results show that the gain of M flames is much smaller than that of V flames. Similar to results of analytic and experimental investigations on the flame transfer function of laminar premixed flames, it shows that the dynamics of a turbulent premixed flame is governed by three relevant parameters: the Strouhal number $(St=LCH∗ max/Lconv)$, the flame length $(LCH∗ max)$, and the flame angle $(α)$. Two flames with the same flame shape exhibit very similar forced responses, regardless of their inlet flow conditions. This is significant because the forced flame response of a highly turbulent, practical gas turbine combustor can be quantitatively generalized using the nondimensional parameters, which collapse all relevant input conditions into the flame shape and the Strouhal number.

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## Figures

Figure 5

Coordinates of maximum CH∗ chemiluminescence intensity locations and the flame angle (α) versus the flame length (LCH∗ max)

Figure 6

Comparison of gain of flames A and B: f=100 and 250 Hz

Figure 7

Comparison of gain of flames C and D: f=175 and 200 Hz

Figure 11

Dependence of phase difference and gain of FTF on Strouhal number (St). Operating conditions: Tin=200°C; Vmean=60, 70, and 80 m/s; Φ=0.55, 0.60, 0.65, 0.70, and premixed; and XH2=0.00, 0.15, and 0.30.

Figure 10

Dependence of (a) maximum gain, (b) damping coefficient (ξ), and (c) convection time delay (τ) upon the flame length (LCH∗ max). Operating conditions: Tin=200°C; Vmean=60, 70, and 80 m/s; Φ=0.55, 0.60, 0.65, 0.70, and premixed; and XH2=0.00, 0.15, and 0.30.

Figure 9

Empirical fits (second-order oscillator model) of gain of FTF and maximum values of gain versus LCH∗ max. Operating conditions: Tin=200°C; Vmean=60, 70, and 80 m/s; Φ=0.55, 0.60, 0.65, 0.70, and premixed; and XH2=0.00, 0.15, and 0.30.

Figure 8

Gain and phase difference of FTF versus forcing frequency at V′/Vmean=0.100. Operating conditions: Tin=200°C; Vmean=60 m/s; Φ=0.60 and premixed; and XH2=0.00 and 0.15.

Figure 4

Dependence of the flame length (LCH∗ max) upon H2 mole fraction for Vmean=90 m/s

Figure 3

Line-of-sight integrated flame images for XH2=0.00, 0.15, 0.30, 0.45, and 0.60 from top to bottom. Operating conditions: Tin=200°C, Vmean=60 m/s, and Φ=0.60.

Figure 2

Deconvoluted stable flame images (CH∗ chemiluminescence). Operating conditions: Tin=200°C; Vmean=60 m/s; Φ=0.55, 0.60, 0.65, 0.70, and premixed; and XH2=0.00, 0.15, 0.30, 0.45, and 0.60.

Figure 1

Schematic of a swirl-stabilized, lean-premixed, gas turbine combustor. Dimensions in millimeters.

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