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

Flow Field and Combustion Characterization of Premixed Gas Turbine Flames by Planar Laser Techniques

[+] Author and Article Information
Ulrich Stopper

German Aerospace Center, Institute of Combustion Technology, Pfaffenwaldring 38-40, D-70569 Stuttgart, Germanyulrich.stopper@dlr.de

Manfred Aigner, Wolfgang Meier, Rajesh Sadanandan, Michael Stöhr

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

Ik Soo Kim

Siemens Industrial Turbomachinery Ltd., P.O. Box 1, Waterside South, Lincoln LN5 7FD, UK

J. Eng. Gas Turbines Power 131(2), 021504 (Dec 30, 2008) (8 pages) doi:10.1115/1.2969093 History: Received April 10, 2008; Revised April 14, 2008; Published December 30, 2008

Abstract

Lean premixed natural gas/air flames produced by an industrial gas turbine burner were analyzed using laser diagnostic methods. For this purpose, the burner was equipped with an optical combustion chamber and operated with preheated air at various thermal powers $P$, equivalence ratios $Φ$, and pressures up to $p=6 bars$. For the visualization of the flame emissions $OH∗$ chemiluminescence imaging was applied. Absolute flow velocities were measured using particle image velocimetry (PIV), and the reaction zones as well as regions of burnt gas were characterized by planar laser-induced fluorescence (PLIF) of OH. Using these techniques, the combustion behavior was characterized in detail. The mean flow field could be divided into different regimes: the inflow, a central and an outer recirculation zone, and the outgoing exhaust flow. Single-shot PIV images demonstrated that the instantaneous flow field was composed of small and medium sized vortices, mainly located along the shear layers. The chemiluminescence images reflected the regions of heat release. From the PLIF images it was seen that the primary reactions are located in the shear layers between the inflow and the recirculation zones and that the appearance of the reaction zones changed with flame parameters.

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Figures

Figure 1

Cut-away drawing of the combustor. The preheated air is seeded with TiO2 particles for PIV measurements. A swirl burner mixes the air with natural gas. Each window consists of two quartz plates with a cooling air flowing in between.

Figure 2

Experimental setup for the imaging of the OH PLIF and the OH∗ chemiluminescence. One ICCD camera images the fluorescence, while the other one records the laser intensity profile.

Figure 3

Experimental setup for the PIV. An additional ICCD camera observes the OH∗ chemiluminescence. The video camera is used for control purposes only.

Figure 4

Streamline plots of three successive instantaneous PIV measurements at p=3 bars, Δp=1%, and Φ=0.59. The size of the burner nozzle is indicated by two marks on the left side of each image. The PIV repetition rate was 5 Hz. Arrows indicate the local flow direction.

Figure 5

Instantaneous distribution of the OH∗ chemiluminescence (line-of-sight) at p=4 bars. The white ellipse represents the burner nozzle.

Figure 6

Single-shot OH PLIF mappings at (a) p=1.5 bars, Δp=1.1%, and Φ=0.53 and (b) p=4 bars, Δp=3%, and Φ=0.50

Figure 7

The absolute gradient of the OH PLIF intensity gives an impression of the instantaneous shape of the flame front. Collage of two measurements with shifted laser sheet positions at different points in time (p=4 bars).

Figure 8

Mean flow field (sum of correlation) at p=4 bars, Δp=1%, and Φ=0.56. Background: contour plot of the corresponding mean OH∗ density.

Figure 9

The inflow region can be clearly distinguished from the recirculation zones by mapping the averaged flow direction

Figure 10

Radial distribution of the axial component of the flow velocity averaged over an axial range of 7–16 mm downstream of the burner exit

Figure 11

Mapping of the standard deviation of the flow velocity at p=3 bars, Δp=1%, and Φ=0.59

Figure 12

Line-of-sight mappings of the mean OH∗ chemiluminescence distribution for different pressure drops over the burner at p=4 bars and Φ≈0.50. The burner nozzle is marked with a white ellipse.

Figure 13

The radial OH∗ distribution is influenced by the pressure. The shaded range cannot be analyzed due to deconvolution artifacts. R is the burner nozzle radius. Inset: Abel-inverted OH∗ chemiluminescence. The marked zones were analyzed for the graphs.

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