Characterization of the hydrogen-dry-low-Nox-micromix-combustion-principle for hydrogen-methane fuel mixtures

Beckmann, N 2019, Characterization of the hydrogen-dry-low-Nox-micromix-combustion-principle for hydrogen-methane fuel mixtures, Doctor of Philosophy (PhD), Engineering, RMIT University.


Document type: Thesis
Collection: Theses

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Title Characterization of the hydrogen-dry-low-Nox-micromix-combustion-principle for hydrogen-methane fuel mixtures
Author(s) Beckmann, N
Year 2019
Abstract With the prospective abatement of fossil energy carriers, gas turbines operated with hydrogen and hydrogen-rich fuel mixtures pave the way for CO2-free energy production in the future. Low emission gas turbines operated with hydrogen and methane, generated with excess renewable energy by power-to-gas applications, facilitate a direct energy recovery while preserving most of the existing natural gas infrastructure. However, the challenging properties of hydrogen make changes to the gas turbine combustor necessary to enable low emission and flexible-fuel operation.

Against this background, the Dry-Low-NOx-Micromix (MMX) combustion technology has been developed at Aachen University of Applied Sciences (AcUAS) for hydrogen-rich fuels. The diffusion combustion process is based on the phenomenon of jet-in-crossflow-mixing and achieves dry low NOx emissions by miniaturization of the injection dimensions without dilution. In recent projects at AcUAS, the MMX combustion principle has been optimized for hydrogen and hydrogen-rich syngas (H2/CO) combustion.

Based on this work, the MMX combustion principle is characterized and optimized for low NOx combustion with variable fuel mixtures of hydrogen and methane in the framework of this thesis. Hence, a viable bridge technology for near-future hydrogen-enriched methane or natural gas combustion is proposed.

The scientific approach presented in this thesis combines low-pressure combustor testing with numerical analyses carried out with the commercial CFD-code Star-CCM+. Initially, the design process that takes into account the challenging fuel characteristics of variable H2/CH4 mixtures is presented. With a first combustor prototype capable of burning a variety of H2/CH4 fuel mixtures between 100% hydrogen and 100% methane, a fundamental characterization of the combustion principle under flexible-fuel operation is conducted.

During a subsequent 2-step optimization study the combustion characteristics are successively enhanced, with particular focus on low NOx emissions at overload conditions and on high combustion efficiencies for methane-rich fuel mixtures and at lean off-design operation. In this process, the dominant influence of the jet-in-crossflow momentum flux ratio as a central design parameter for guaranteeing low NOx emissions is established. With the final combustor geometry, an optimum concerning fuel flexibility, pressure loss, combustion efficiency, and NOx emissions is found that generates less than 1.8 ppm NOx (corrected to 15 vol.% O2) at the design point with a combustion efficiency exceeding 98% over the entire operating range.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Engineering
Subjects Energy Generation, Conversion and Storage Engineering
Keyword(s) Hydrogen
Methane
Gas turbine
Low NOx
Low emission
CFD
Non premixed
Combustion
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Created: Thu, 12 Dec 2019, 10:29:39 EST by Adam Rivett
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