Zero-carbon combustion of aluminum powder fuel using an axial-tangential swirl burner

Aluminum, due to its affordability, abundance, high reactivity, and energy density, is one of the most promising energy carriers in a zero-carbon society. This study developed a screw powder feeder for precise aluminum delivery at 30–148 mg/s and a lab-scale innovative axial-tangential swirl burner for the self-sustained combustion of dense powder flows. Particle Image Velocimetry (PIV) was performed in cold flows to map the axial-tangential swirl flow field, which may impact the mixing of particles and oxidizers. Following a well-designed ignition procedure using methane, the axial-tangential swirl burner facilitated long-term stable combustion of aluminum particles in O₂/N₂ flows, with oxygen mole fractions ranging from 16 % to 100 %. This indicates that stable combustion in air yielded approximately 1–5 kW output. Oxygen concentration and particle mass flow rate influenced burning rates of the aluminum powder jet as a diffusion group flame, which sometimes caused oscillations at the flame root. Additionally, spectral fitting indicated that the surface temperatures of the condensed phase reached 2930–3431 K under oxygen concentrations of 20–100 %. Ultimately, combustion products were collected using a steel plate placed at the quartz glass tube outlet. Abundant nano-sized alumina particles were observed via scanning electron microscopy (SEM) imaging.