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Gas Turbines: Combustion, Fuels, and Emissions

Characterization of the Acoustic Interactions in a Two-Stage Multi-Injection Combustor Fed With Liquid Fuel

[+] Author and Article Information
Theodore Providakis, Laurent Zimmer, Philippe Scouflaire

Sébastien Ducruix

 CNRS, UPR 288 - Laboratoire EM2C 92290 Châtenay-Malabry, France; Ecole Centrale Paris 92290 Châtenay-Malabry, Francesebastien.ducruix@ecp.fr

J. Eng. Gas Turbines Power 134(11), 111503 (Sep 24, 2012) (8 pages) doi:10.1115/1.4007200 History: Received June 27, 2012; Revised July 11, 2012; Published September 24, 2012; Online September 24, 2012

Burners operating in lean premixed prevaporized (LPP) regimes are considered as good candidates to reduce pollutant emissions from gas turbines. Lean combustion regimes result in lower burnt gas temperatures and therefore a reduction on the NOx emissions, one of the main pollutant species. However, these burners usually show strong flame dynamics, making them prone to various stabilization problems (combustion instabilities, flashback, flame extinction). To face this issue, multi-injection staged combustion can be envisaged. Staging procedures enable fuel distribution control, while multipoint injections can lead to a fast and efficient mixing. A laboratory-scale staged multipoint combustor is developed in the present study, in the framework of LPP combustion, with an injection device close to the industrial one. Using a staging procedure between the primary pilot stage and the secondary multipoint one, droplet and velocity field distributions can be varied in the spray that is formed at the entrance of the combustion chamber. The resulting spray and flame are characterized using OH-planar laser induced fluorescence, high speed particle image velocimetry, and phase Doppler anemometry measurements. Three staging values, corresponding to three different flame stabilization processes, are analyzed, while power is kept constant. It is shown that mean values are strongly influenced by the fuel distribution and the flame position. Using adequate postprocessing, the interaction between the acoustic field and the droplet behavior is characterized. Spectral analysis reveals a strong acoustic-flame coupling leading to a low frequency oscillation of both the velocity field and the spray droplet distribution. In addition, acoustic measurements in the feeding line show that a strong oscillation of the acoustic field leads to a change in fuel injection, and hence droplet behavior.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic view of the injection device. Flow from left to right.

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Figure 2

Experimental setup. Flow from left to right.

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Figure 3

Averaged OH* chemiluminescence for the three operating points. Intensity scale has been normalized by the maximum of the OP20 intensity value. Flow from left to right.

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Figure 4

Average droplet velocity magnitude (top) and OH-PLIF (bottom) fields for the three operating conditions. Contour lines of the velocity magnitude are superimposed on the OH fields. Flow from left to right.

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Figure 5

PSD of the acoustic pressure (from microphones M2, M3 and M4), heat release rate (OH* chemiluminescence), and droplet axial velocity (PDA) for OP60- case. Log scales are used.

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Figure 6

Evolution of the PSD peak amplitude for the acoustic instability in the combustion chamber (left) and in the multipoint feeding line (right) as a function of the staging factor

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Figure 7

Fluctuations of the phase averaged acoustic pressure pΦ′, normalized heat release rate q̃Φ, and axial velocity VxΦ′. For OP60-, fac  = 300 Hz and for OP60+ and OP20 , fac  = 330 Hz.

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