Experimental and numerical investigations of the dry-low-NOx hydrogen micromix combustion chamber of an industrial gas turbine

Combined with the use of renewable energy sources for its production, hydrogen represents a possible alternative gas turbine fuel within future low emission power generation. Due to the large difference in the physical properties of hydrogen compared to other fuels such as natural gas, well established gas turbine combustion systems cannot be directly applied for dry-low-NOx (DLN) hydrogen combustion. Thus, the development of DLN combustion technologies is an essential and challenging task for the future of hydrogen fuelled gas turbines. The DLN micromix combustion principle for hydrogen fuel has been developed to significantly reduce NOx emissions. This combustion principle is based on cross-flow mixing of air and gaseous hydrogen which reacts in multiple miniaturized diffusion-type flames. The major advantages of this combustion principle are the inherent safety against flash-back and the low NOx emissions due to a very short residence time of reactants in the flame region of the micro-flames. The micromix combustion technology has been already proven experimentally and numerically for pure hydrogen fuel operation at different energy density levels. The aim of the present study is to apply and compare different combustion models for the characterization of the micromix flame structure, its interaction with the flow field and its NOx emissions. The study reveals great potential for the successful application of numerical flow simulation to predict flame structure and NOx emission level of micromix hydrogen combustion, help understanding the flow phenomena related with the micromixing, reaction zone and NOx formation and support further optimization of the burner performance