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

Experimental Analysis of Soot Formation and Oxidation in a Gas Turbine Model Combustor Using Laser Diagnostics

[+] Author and Article Information
Klaus Peter Geigle

German Aerospace Center (DLR),  Institute of Combustion Technology, Pfaffenwaldring 38-40, D-70569 Stuttgart, Germanyklauspeter.geigle@dlr.de

Jochen Zerbs, Markus Köhler, Michael Stöhr, Wolfgang Meier

German Aerospace Center (DLR),  Institute of Combustion Technology, Pfaffenwaldring 38-40, D-70569 Stuttgart, Germany

J. Eng. Gas Turbines Power 133(12), 121503 (Sep 12, 2011) (9 pages) doi:10.1115/1.4004154 History: Received April 14, 2011; Revised April 17, 2011; Published September 12, 2011; Online September 12, 2011

Sooting ethylene/air flames were investigated experimentally in a dual swirl gas turbine model combustor with good optical access at atmospheric pressure. The goals of the investigations were a detailed characterization of the soot formation and oxidation processes under gas turbine relevant conditions and the establishment of a data base for the validation of numerical combustion simulations. The flow field was measured by stereoscopic particle image velocimetry, the soot volume fractions by laser-induced incandescence, the heat release by OH chemiluminescence imaging and the temperatures by coherent anti-Stokes Raman scattering. Two flames are compared: a fuel-rich partially premixed flame with moderate soot concentrations and a second one with the same parameters but additional injection of secondary air. Instantaneous as well as average distributions of the measured quantities are presented and discussed. The measured soot distributions exhibit a high temporal and spatial dynamic. This behavior correlates with broad temperature probability density functions. With injection of secondary air downstream of the flame zone the distributions change drastically. The data set, including PDFs of soot concentration, temperature and flow velocity, is unique in combining different laser diagnostics with a combustor exhibiting a more challenging geometry than existing validation experiments.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Aero-engine nozzle modified for gaseous fuel (right). The gaseous fuel is released in a location equal to the metal ring conventionally providing the film atomization (left).

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Figure 2

Burner configuration of dual swirl burner

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Figure 3

Mean flow fields measured in the gas film nozzle and visualized as vector plot for the in-plane components while the out-of-plane component is color-coded according to the color bar. (Left image pair) without oxidation air and (right image pair) pair with oxidation air. For each image pair, the left one corresponds to the central plane (r = 0) and the right one to the offset plane (r = 25 mm). The reference vector in the bottom left corner corresponds to a velocity of 10 m/s.

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Figure 4

Single shot stream lines visualizing in-plane motion only, as measured by PIV, with oxidation air at r = 25 mm. The instantaneous flow clearly deviates from the average flow field (Fig. 3 (right)). Velocity maxima vary between 34 and 41 m/s in this selection.

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Figure 5

Averaged OH chemiluminescence in the gas film nozzle with oxidation air. (left) OH chemiluminescence image corrected for chip sensitivity. (right) After Abel deconvolution. The dimension of the images is (horizontal × vertical) 80.6 × 76.9 mm2 .

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Figure 6

Averaged soot volume fractions measured in the gas film nozzle. Left image pair without oxidation air, right image pair with oxidation air, within those pairs: left: plane at r = 0, right: plane at r = 25 mm. The dimension of the images is 81.2 × 111.1 mm2 .

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Figure 7

Representative set of LII single shot images from the flame without oxidation air. The peak soot volume fraction is 0.4 ppm; the upper image contains the highest soot levels in the full sequence. The statistics below indicate the frequency of detecting certain intensities in a tiny rectangle through the full sequence (upper) and the single pixel intensity probability evaluated for 20 images (lower).

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Figure 8

Temperature statistics are available for all measurement locations shown in Fig. 9 indicated in the pdfs are the mean and most probable (mp) temperatures as well as the range covering the most probable 90% of all instantaneous temperatures. Total number of analyzed laser pulses is 1200; the measurement locations for the displayed histograms are at height 15 mm (left) and 65 mm (right) on burner axis.

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Figure 9

Temperature profiles measured by CARS for operation with oxidation air. Temperatures are plotted as vertical profiles (left) for different radial position r, and as horizontal profile at h = 25 mm (right). The squares display the mean temperature, the circles the most probable temperature and the lines indicate the range of the temperature pdf in which 90% of all measurements lie.

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