Benoît Fiorina (Centrale Supélec)

Modeling turbulent decarbonized combustion

Benoît Fiorina

Université Paris-Saclay, CNRS, CentraleSupélec, Laboratoire EM2C, 91190, Gif-sur-Yvette, France.

Hydrocarbon combustion, involved in 80% of the worldwide primary energy consumption, produces most anthropogenic CO2 emissions. Electrification will however not entirely replace combustion in the short term for two main reasons: first, batteries exhibit an energy density about 50-100 lower than hydrocarbon fuels. Combustion will, therefore, still be required to power long-distance transport vehicles, such as boats, trucks, or aircraft. Second, many industrial sectors, such as steel, cement, glass, and aluminum, require high temperature (more than 500°C) heat sources that can hardly be delivered without a combustion process.

Developing and optimizing new energy systems that integrate carbon-neutral fuels such as biofuels, e-fuel, hydrogen or ammonia constitutes a relevant energy scenario to limit global warming. Combustion engineers need reliable numerical tools for designing future combustion chambers. Advanced modeling of combustion phenomena is required for optimizing the injection system, the combustion chamber geometry, the wall heat transfers but also the pollutant formation. Simulations are also needed to challenge solutions to stabilize low-temperature flames.

The scientific challenges are to model the complex interactions between combustion chemistry and the turbulence of the flow at an affordable computational cost, compatible with industrial constraints. The first difficulty is that the kinetics of combustion involves hundreds of chemical species that react through thousands of elementary reactions. To save computing time, the detailed mechanisms that describe this complex chemistry are reduced before being used in CFD codes. The second issue is related to the modeling of the turbulence / chemistry coupling which is not fully resolved in simulations.

This presentation aims to establish a brief state-of-the-art of both kinetic reduction methods and turbulent combustion models suitable for simulating emerging combustion technologies. The discussion focuses on large eddy simulation (LES) formalism, especially relevant to capture unsteady interactions between chemistry and turbulence. The new scientific challenges appearing with in the introduction of carbon neutral fuel will be highlighted.