Optimization of a cyclonic combustion chamber for the thermochemical conversion of alternative fuels

This work provides an insight into the influence of the design parameters, specifically the configuration of the outlet section, on the fluid dynamic field and residence times distribution of a cyclonic flow burner, designed to operate under Moderate or Intense Low oxygen Dilution (MILD) combustion conditions with alternative energy carriers. The investigated geometric parameters play a key role in determining the velocity pattern and mixing process of the reactant mixture, fluids residence time distribution and burned gas internal recirculation, by influencing the oxidation process efficiency and pollutant emissions. These latter characteristics are essential in the framework of the recent global energy transition toward renewable sources. Indeed, the intermittency of renewables sources requires the development of specific processes and technologies able to mitigate their inherent variability. Among them, chemical storage ensures large storage capacity for long period and with high efficiency, ensuring easy and safe transportation and storage. In this context, bio-derived alcohols and free carbon fuels such as ammonia and hydrogen have been identified as alternative energy carriers to efficiently storage the renewable energy. Nevertheless, the exploitation of these molecules poses some relevant challenges. The most considerable obstacles are related to the variable composition of the bio-derived products and the consequent lower heating value with respect to traditional hydrocarbon fuels. These aspects greatly limit the technologies capable of employing such energy carriers. Therefore, it is necessary to identify innovative thermochemical conversion technologies highly flexible with respect to the type and composition of the fuel, which ensure reduced pollutant emissions and the stability of the oxidation process for each required operational condition. In this respect, MILD combustion represents an efficient technology matching these issues. In this context, the obtained results allow to identify the appropriate design features of a cyclonic flow burner in order to ensure the complete conversion of the inlet charge and the effective process stabilization.