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TECHNICAL PAPERS: Gas Turbines: Combustion and Fuels

Lean Blowout Limits and NOx Emissions of Turbulent, Lean Premixed, Hydrogen-Enriched Methane/Air Flames at High Pressure

[+] Author and Article Information
P. Griebel1

Combustion Research, Paul Scherrer Institut (PSI), 5232 Villigen PSI, Switzerlandpeter.griebel@psi.ch

E. Boschek, P. Jansohn

Combustion Research, Paul Scherrer Institut (PSI), 5232 Villigen PSI, Switzerland

1

Corresponding Author. Currently at the German Aerospace Center (DLR), Institute of Combustion Technology, Pfaffenwaldring 38-40, 70569 Stuttgart, Germany.

J. Eng. Gas Turbines Power 129(2), 404-410 (Aug 15, 2006) (7 pages) doi:10.1115/1.2436568 History: Received July 03, 2006; Revised August 15, 2006

Flame stability is a crucial issue in low NOx combustion systems operating at extremely lean conditions. Hydrogen enrichment seems to be a promising option to extend lean blowout limits (LBO) of natural gas combustion. This experimental study addresses flame stability enhancement and NOx reduction in turbulent, high-pressure, lean premixed methane/air flames in a generic combustor capable of a wide range of operating conditions. Lean blowout limits and NOx emissions are presented for pressures up to 14bar, bulk velocities in the range of 32–80ms, two different preheating temperatures (673K, 773K), and a range of fuel mixtures from pure methane to 20% H280%CH4 by volume. The influence of turbulence on LBO limits is also discussed. In addition to the investigation of perfectly premixed H2-enriched flames, LBO and NOx are also discussed for hydrogen piloting. Experiments have revealed that a mixture of 20% hydrogen and 80% methane, by volume, can typically extend the lean blowout limit by 10% compared to pure methane. The flame temperature at LBO is 60K lower resulting in the reduction of NOx concentration by 35%(0.50.3ppm15%O2).

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

High-pressure combustor with OH chemiluminescence detector

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Figure 2

Hydrogen piloting

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Figure 3

Time history of the OH chemiluminescence signal during lean blowout

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Figure 4

LBO limits of the velocity variation for two different inlet temperatures (673K, 773K) and different CH4∕H2 mixtures (5bar, 40m∕s, grid g365,xg10)

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Figure 5

Effect of H2 enrichment on LBO limits for two different inlet temperatures (673K, 773K) and pressures of 5bar and 14bar (40m∕s, grid g365,xg10)

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Figure 6

Effect of turbulence intensity on LBO limits (673K, 5bar, grids g365,xg10 and g350,xg30)

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Figure 7

Effect of LBO extension due to H2 enrichment on NOx, CO, and exhaust gas temperature (673K, 5bar, 40m∕s, grid g365,xg10)

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Figure 8

Pressure influence on NOx for pure methane and methane/hydrogen flames and two different equivalence ratios (673K, 40m∕s, grid g365,xg10)

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Figure 9

Influence of preheating on NOx, CO, and exhaust gas temperature for pure methane and methane/hydrogen flames (5bar, 40m∕s, grid g365,xg10)

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Figure 10

Comparison of LBO limits for H2 addition premixed versus piloting (673K, 5bar, 40m∕s, grid g365,xg10)

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Figure 11

Typical flame shape of premixing and H2 piloting (673K, 5bar, 40m∕s, Φ=0.5, grid g365,xg10)

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Figure 12

Comparison of NOx emissions for H2 addition premixed versus piloting (OH chemiluminescence, 673K, 5bar, 40m∕s, grid g365,xg10)

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