Development of an additively manufactured research burner for increased energy efficiency

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In view of global warming, carbon-free energy sources are of utmost importance for the reduction of CO2 emissions into the atmosphere. Alternatives to carbon-containing fuels, such as alcohols, are ammonia (NH3) and/or hydrogen (H2), both of which are carbon free. Thus, a combination of these gaseous fuels, or their addition to either conventional or synthetic atomized liquid fuels, may lead to a great improvement of carbon-reduced or even carbon-free energy sources. The very complex combined combustion of these fuel systems is the background for this investigation. In this context, a high-temperature and corrosion resistant, additively manufactured and smart burner is developed to increase energy efficiency and to reduce pollutant formation. Additive Manufacturing (AM) enables the generation of unique components with a high degree of design freedom and the possibility to realize complex (internal) geometries. Here, the advantages of AM are ideally exploited by integrated functional designs, such as curved media feeding channels, open porous structures, and the direct manufacturing of assembly groups with integrated sensors. The material of choice is a Nickel base alloy (MAR-M247), which is a proven material for high temperature relevant applications. From a combustion perspective, the present project focuses on the addition of ammonia and/or hydrogen to liquid bio-alcohols, such as methanol, ethanol, or n-butanol, in order to reduce the CO2 emissions. The carbon-free fuels may be injected as gases or liquids (at reduced temperatures) or be dissolved in the liquid fuel in the additively manufactured burner. The latter method requires profound knowledge of the solubility of hydrogen and ammonia in biofuels, as well as the atomization and evaporation characteristics of the liquid. The projected burner is extremely flexible and allows for the injection of the premixed gaseous fuels or of the ammonia with the oxidizer so that different combustion regimes including premixed, partially premixed, and non-premixed combustion coexist. These options ensure an extremely high flexibility of the fuels as well as their injection. A variable ring to inject the ammonia directly into the hot flame zone enables the improvement of the poor combustion properties of the ammonia with respect to the ignition and the flame speed. The combination of modeling, simulations, and experiments of the processes near the injector, along with contributions from additively manufactured burner technology, provide excellent knowledge gains in reducing global warming in an ideally carbon-free energy transportation sector.