The interaction between particle clustering and iron particle cloud combustion in homogeneous isotropic turbulence

A pseudo spectral multi-phase solver in combination with a point particle iron reaction model is used, capturing mass, heat and momentum transfer between the phases. We investigate the combustion of 10 µm-sized iron particles with air, in homogeneous isotropic turbulence (HIT) at Stokes number one, varying the equivalence ratios from lean ($\phi=0.1$) to fuel-rich ($\phi=2$).

At the start, the particles are homogeneously distributed with a temperature below particle ignition temperature. Particle clusters form through turbulence and ignite. While in the very lean regime ($\phi<0.25$) the $\mathrm{O_2}$ diffusion through the particle boundary layer limits the conversion of $\mathrm{Fe}$ to $\mathrm{FeO}$, for $\phi>0.5$, the oxygen depletion in clusters slows down the overall oxidation progress, and the conversion is limited by the transport of oxygen from regions devoid of particles into clusters.