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

Experimental Study on Laser-Induced Ignition of Swirl-Stabilized Kerosene Flames

[+] Author and Article Information
Klaus G. Moesl1

Lehrstuhl für Thermodynamik, Technische Unversität München, D-85748 Garching, Germanymoesl@td.mw.tum.de

Klaus G. Vollmer, Thomas Sattelmayer

Lehrstuhl für Thermodynamik, Technische Unversität München, D-85748 Garching, Germany

Johannes Eckstein, Herbert Kopecek

Alternative Energy and Environmental Technologies, Global Research Center, General Electric, D-85748 Garching, Germany

1

Corresponding author.

J. Eng. Gas Turbines Power 131(2), 021501 (Dec 22, 2008) (8 pages) doi:10.1115/1.2981181 History: Received March 28, 2008; Revised April 28, 2008; Published December 22, 2008

Conventional ignition systems of aeroengines are an integral part of the combustion chamber’s structure. Due to this hardware-related constraint, the ignition spark has to be generated in the quench zone of the combustion chamber, which is far from the optimum regarding thermo- and aerodynamics. An improved ignitability of the fuel-air mixture can be found in the central zone of the combustor, where higher local equivalence ratios prevail and where mixing is favorable for a smooth ignition. It would be a major advancement in aeroengine design to position the ignition kernel in these zones. A laser system is able to ignite the fuel-air mixture at almost any location inside of the combustion chamber. Commercial laser systems are under development, which can replace conventional spark plugs in internal combustion engines and gas turbines. This study was conducted to evaluate the applicability of laser ignition in liquid-fueled aeroengines. Ignition tests were performed with premixed natural gas and kerosene to evaluate the different approaches of laser and spark plug ignition. The experiments were carried out on a generic test rig with a well-investigated swirler, allowing sufficient operational flexibility for parametric testing. The possibility of the free choice of the laser’s focal point is the main advantage of laser-induced ignition. Placing the ignition kernel at the spray cone’s shear layer or at favorable locations in the recirculation zone could significantly increase the ignitability of the system. Consequently, the laser ignition of atomized kerosene was successfully tested down to a global equivalence ratio of 0.23. Furthermore, the laser outperformed the spark plug at ignition locations below axial distances of 50 mm from the spray nozzle.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Test rig for the measurement campaign

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Figure 2

Sectional view of the combustion chamber

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Figure 3

Installation of the laser head above the combustion chamber

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Figure 4

Sectional view of the electrode igniter. The drawing displays the vertical displacement capability of the system by showing two pairs of electrodes although only one pair was used for the ignition tests at a time.

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Figure 5

Ignition kernel of the laser (left plot) and the spark plug ignition (right plot)

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Figure 6

Lean ignition limits of the different ignition systems for technically premixed natural gas. The plot shows ignition locations close to the upper wall as well as in the center of the combustion chamber.

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Figure 7

Procedure for the kerosene spray ignition experiments

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Figure 8

Example of an ignition map for kerosene spray combustion (ṁair=14.0 g/s, Φglobal=0.40, D32=43.8 μm, S=0.55, and Tpre=300 K). The tested ignition locations are marked by circles. Filled (blue) circles indicate successful ignitions by laser, resulting in the cross-hatched area. The (pink) shaded area displays successful ignitions by using the electrode igniter as a laser substitute. The background shows the numerical result for the axial velocity component of the combustor flow field.

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Figure 9

Variation of the kerosene spray angle (ṁair=14.0 g/s, Φglobal=0.47, and Tpre=300 K). These results were obtained by using the electrode igniter (EEI=100 mJ).

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Figure 10

Variation of the air mass flow ṁair (Φglobal=0.40, D32=43.8 μm, and Tpre=300 K). These results were obtained by using the electrode igniter (EEI=100 mJ).

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Figure 11

Variation of the global equivalence ratio Φ (ṁair=14.0 g/s, D32=43.8 μm, and Tpre=300 K). These results were obtained by using the electrode igniter (EEI=100 mJ).

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Figure 12

Variation of the Sauter mean diameter D32 (ṁair=14.0 g/s, Φglobal=0.47, and Tpre=300 K). These results were obtained by using the electrode igniter (EEI=100 mJ).

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Figure 13

Variation of the ignition energy (ṁair=14.0 g/s, Φglobal=0.40, D32=43.8 μm, and Tpre=300 K). These results were obtained by using the electrode igniter.

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Figure 14

Variation of the combustion air temperature Tpre (ṁair=14.0 g/s, Φglobal=0.40, and D32=43.8 μm). These results were obtained by using laser-induced ignition (Elaser=60 mJ).

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Figure 15

Variation of the vertical ignition plane (i.e., z-axis offset), (ṁair=14.0 g/s, Φglobal=0.50, D32=34.5 μm, and Tpre=300 K). These results were obtained by using the electrode igniter.

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