An Experimental Study of Lean Blowout With Hydrogen-Enriched Fuels

J. Eng. Gas Turbines Power  -- April 2012 --  Volume 134,  Issue 4

An Experimental Study of Lean Blowout With Hydrogen-Enriched Fuels

Shengrong Zhu and Sumanta Acharya

Turbine Innovation and Energy Research (TIER) Center, Department of Mechanical Engineering, Louisiana State University, Baton Rouge, LA 70803

Abstract

Lean premixed combustion is widely used to achieve a better compromise between nitric oxide (NOx) emissions and combustion efficiency (related to CO levels). However, combustor operation near the lean blowout (LBO) limit can render the flame unstable and lead to oscillations, flashback, or extinction, limiting the potential range of lean combustion application.

Researchers studied combustion of pure methane and blended methane-hydrogen with hydrogen-levels up to 80% by volume in a swirl stabilized premixed combustor. Results indicate that there is a single-ringed structure of internal recirculation zone (IRZ) in the non-reacting flow. In the reacting flows, there is a more complex flow pattern with a two-celled IRZ structure in which the axial velocity near the center-axis is oriented downstream. As the equivalence ratio decreases, the width of IRZ decreases in methane flames while it increases in hydrogen-enriched flames, and the flame shape changes from conical to an elongated columnar shape, especially in hydrogen-enriched flames. There are two different modes of vortex breakdown observed, spiral mode in methane flames and bubble mode in hydrogen-enriched flames. Differences between the behavior of the methane-only and hydrogen-enriched flames lead to different behavior of the flame as it approaches the lean blowout.

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