Physics of aluminum single-particle ignition and combustion

Our aim is to link the single-particle ignition, oxide lobe formation, and attached and detached flames to the physical and chemical processes on the particle scale, which are essential as they determine particle conversion yields of hydrogen and heat at the system scale. High-fidelity FR-DNS coupled with VoF will be appropriately developed for Al-steam combustion.

This will, for the first time, enable quantification of the formation and dynamics of the oxide lobe on the parent particle. The temporal and spatial resolution required in FR-DNS is governed by chemistry and its interaction with transport and will be determined by grid studies. Simulations will unravel the unknown interplay of chemical reactions and oxide lobe dynamics for homogeneous (particle-detached) and het- erogeneous (particle-attached) Al-steam flames. In-situ high-resolution optical diagnostics will provide data for comparison on the particle velocity (PTV/PIV, DBI) and temperature (pyrometry), ig- nition, and combustion dynamics (AlO-LIF). Only the knowledge gained from simulations validated against experiments at different pressures makes it possible to develop novel models urgently needed for large-scale simulations. Implementing the pressure-dependent interactions between oxide lobe forma- tion, homogeneous and heterogeneous Al reactions in a PIC model and its coupling with an improved flamelet model for the particle boundary layer flame will allow for unprecedented CP-DNS and LES.

Evolution of a single micrometer-sized aluminum particle in steam, from ignition to burnout. Processes at highly varying scales are depicted: the particle-attached flame on the surface (heterogeneous reactions), evaporation, the particle-detached near-particle flame (homogeneous reactions) with nucleation of nanoparticles and their condensation on the oxide lobes, lobe growth, and full-particle encapsulation. Length and time scales of transport, chemistry, and particle oxidation are indicated.
CC BY 4.0
Evolution of a single micrometer-sized aluminum particle in steam, from ignition to burnout. Processes at highly varying scales are depicted: the particle-attached flame on the surface (heterogeneous reactions), evaporation, the particle-detached near-particle flame (homogeneous reactions) with nucleation of nanoparticles and their condensation on the oxide lobes, lobe growth, and full-particle encapsulation. Length and time scales of transport, chemistry, and particle oxidation are indicated.
CC BY 4.0