A non-premixed porous media burner for clean and highly-flexible H₂/CH₄ combustion

Hydrogen is an important energy vector as it can store intermittently produced electrical energy from renewable sources like solar, wind or nuclear through electrolysis and thermolysis. To advance the technology for hydrogen utilization for heat production, porous media burners (PMB), a type of heat-recirculating burner, are demonstrated in this study. These burners recirculate a fraction of the heat produced during the combustion process back towards the fresh reactants through conduction and radiation in the solid matrix, leading to higher flame speeds and extended flammability range. This allows PMBs to operate at ultra-lean conditions, which is necessary to alleviate pollutant emissions, especially for hydrogen, which is prone to high thermal NO_x emission due to its high flame temperature. The PMB presented in this work was optimized for high fuel-flexibility, and has been shown to operate over a range of fuels like hydrogen, methane and ammonia (shown in previous studies) without any significant design changes. This study also discusses the design of a fuel injector for PMB through additive manufacturing, which allows to operate the PMB in a non-premixed configuration, which is essential due to safety hazards associated with hydrogen. The performance of the non-premixed PMB is compared to the premixed PMB in terms of stability maps, emissions and the axial temperature profiles for different fuel blends of hydrogen and methane.