Experimental and Numerical Characterization of the Dry Low NOx Micromix Hydrogen Combustion Principle at Increased Energy Density for Industrial Hydrogen Gas Turbine Applications

Abstract

In the future low pollution power generation can be achieved by application of hydrogen as a possible alternative gas turbine fuel if the hydrogen is produced by renewable energy sources such as wind energy or biomass. The utilization of existing IGCC power plant technology with the combination of low cost coal as a bridge to renewable energy sources such as biomass can support the international effort to reduce the environmental impact of electricity generation. Against this background the dry low NOx Micromix combustion principle for hydrogen is developed for years to significantly reduce NOx emissions. This combustion principle is based on cross-flow mixing of air and gaseous hydrogen and burns in multiple miniaturized diffusion-type flames. The two advantages of this principle are the inherent safety against flash-back and the low NOx concentrations due to a very short residence time of reactants in the flame region of the micro-flames. The paper presents experimental results showing the significant reduction of NOx emissions at high equivalence ratios and at simultaneously increased energy density under preheated atmospheric conditions. Furthermore the paper presents the feasibility of enlarged Micromix hydrogen injectors reducing the number of required injectors of a full-scale Micromix combustion chamber while maintaining the thermal energy output with significantly low NOx formation. The experimental investigations are accompanied by 3D numerical reacting flow simulations based on a simplified hydrogen combustion model. Comparison with experimental results shows good agreement with respect to flame structure, shape and anchoring position. Thus, the experimental and numerical results highlight further potential of the Micromix combustion principle for low NOx combustion of hydrogen in industrial gas turbine applications.