Experimental Characterization of Low NO_x Micromix Prototype Combustors for Industrial Gas Turbine Applications

The use of renewable discontinuous energy sources, such as wind- or solar-energy, raises the question of ensuring the continuous demand for energy. For future energy storage scenarios, hydrogen combustion systems play an important role. This offers new opportunities for alternative combustion processes with regard to efficient, safe and low NO_x combustion of hydrogen. In addition hydrogen combustion technology will be in need of gas turbine technology for future IGCC power plant concepts. Against the background of ensuring a secure and low NO_x combustion of hydrogen, the micromix burning principle is developed since years and was first investigated for the use in aircraft jet engines to significantly reduce NO_x-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 NO_x-emissions due to a very short residence time of reactants in the flame region of the micro-flames. The paper presents an experimental in depth analysis of the combustion principle with regards to low NO_x-emissions for higher energy densities. Therefore several geometric variations were investigated and the burning principle was scaled and tested for higher energy densities up to 15 MW/(m²bar). For the different geometries and energy densities, combustion stability, flame anchoring behavior and associated NO_x-emissions are tested under preheated atmospheric conditions. The experimental results show the successful scaling of the micromix principle for high energy densities. The general mapping of the test burners demonstrates a wide operating range. Flow phenomena influencing the flame lifting and flame anchoring position with respect to the resulting NO_x-emission are analyzed. The investigations highlight further potential for NO_x-reduction in industrial gas turbine applications.