A-STEAM
Aluminum-steam combustion for green energy

Metal fuels are emerging as a zero-carbon, high-energy density replacement for fossil fuels due to their availability and recyclability using renewable energy. Aluminum powder has been investigated mostly in air as an additive in solid rocket engines. Combustion in pressurized steam is a new concept for on-demand production of high-temperature heat and hydrogen. In A-STEAM we combine simulations, modeling and experiments to investigate the fundamental properties of pressurized aluminum-steam flames: from single particles to turbulent flames with millions of particles.

CC BY 4.0
CC BY 4.0

Recent feasibility studies, such as Shkolnikov et al. (2011), Trowell et al. (2020), suggest that aluminum has a high potential as a renewable energy carrier, especially when combusted at high temperatures in steam, e.g., Ersoy et al. (2022). The overall process yield of hydrogen/heat and nanoparticle emissions are closely linked to chemistry and physical transport processes at the particle scale.

Quantitative understanding of the dynamics of multi-phase and multi-scale aluminum-steam flames, driven by microscopic transport processes, phase changes, as well as homogeneous and heterogeneous chemical reactions at the particle level, is largely lacking. In A-STEAM we unravel the fundamental properties of pressurized aluminum-steam flames for the entire scientific chain, from single particles to turbulent flames with millions of particles, through a well-orchestrated combination of high-fidelity simulations, advanced modeling, and tailored experiments.

Combining numerical studies and experiments

We combine and develop our unique computational capabilities in fully resolved direct numerical simulations (FR-DNS) at the particle level, novel particle-in-cell (PIC) models considering particle-attached/particle-detached flames and Al2O3 nanoparticle formation, carrier-phase DNS (CP-DNS), and large eddy simulations(LES) of turbulent confined flames. By combining numerical studies and tailored experiments we will be able to quantify physicochemical processes in Al-steam combustion, bridging the gap between single particles and turbulent flames.

Our numerical-experimental database of reference Al-steam flames, together with science-based best practice guidelines for future Al burners, will also empower the broader metal fuel research community and guide future system design and implementation of this carbon-free technology.

Powder for power

Metal powders are recyclable, zero-carbon, high-energy density carriers of renewable energy. In metal powder combustion the flame dynamics is governed by single particle combustion– a flame within a flame, so to speak.

Combustion with oxygen leads to very high flame temperatures above the aluminum boiling temperature. Most of the aluminum evaporates and burns in a detached gaseous flame. Alumina (Al2O3) immediately nucleates, leading to abundant production of nanoparticles and limiting the use of aluminum as recyclable metal fuel. Switching to steam as oxidizer drastically changes the combustion process. The particle-detached gaseous flame transitions to a surface-attached flame in which heterogeneous oxidation to alumina occurs. This effect becomes even stronger under high pressure. Alumina does not dissolve but accumulates in oxide lobes.

Illustration of nanoparticle formation during aluminum particle combustion in O2/air (left) and steam (right)
CC BY 4.0
Illustration of nanoparticle formation during aluminum particle combustion in O2/air (left) and steam (right)
CC BY 4.0

Research areas

Single particle

With simulations and experiments we link the single-particle ignition, oxide lobe formation, and attachted and detached flames to the physical and chemical processes on the particle scale.

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Particle clusters

With numerical simulations we investigate different regimes of particle group combustion and flame propagation. In aluminum-steam flames, those regimes are mostly unexplored but essential to understand flame stabilization at the system level.

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Turbulent flames

We use advanced 3D recuurence CFD and experiments to study turbulent aluminum-steam flames, which are crucial in understanding particle cloud combustion for future aluminum-based energy converters.

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Nanoparticle formation

In A-STEAM we use simulations and experiments to understand the formation and dynamics of alumina nanoparticles so that their detrimental effects on aluminum combustion efficiency can be limited.

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