PhD defense: Quentin CAZÈRES – “Analysis and reduction of chemical kinetics for combustion applications”
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Combustion of fossil fuels has been used for decades for all kinds of purposes, from generating electricity to make air planes fly but they are also the main source of pollution leading to climate change. New sustainable, less polluting fuels must be studied in order to diminish as much as possible the human impact on the planet. Combustion is a very complex process combining fluid dynamics, thermodynamics and chemistry with hundreds of species involved. In order to be able to use all the tools the numerical simulation has to offer with increasing complexity, from canonical cases to 3D Large Eddy Simulations (LES) with two-phase flows, analyzing the relevant chemical pathways and reducing the reaction mechanisms describing this chemistry is necessary. Analytically Reduced Chemistry (ARC) is a way of reducing the size and the complexity of chemical mechanisms where only the species and reactions relevant to given conditions are kept while keeping a physically coherent mechanism. ARC lies among several methodologies for the reduction of kinetics but with the increasing complexity of the fuels and configurations that need to be studied in the future years, it is now more and more interesting.
The first objective of this work is to develop a fully automatic procedure for developing ARC mechanisms that do not require and expert knowledge on kinetics and can be adapted to any kind of conditions to be as versatile as possible. This objective has been fulfilled by the creation of the code ARCANE and the second objective was to assess its performances in two different configurations.
The first configuration consists in the combustion of premixed hydrogen-enriched methane/air in a swirled combustor with 2 levels of enrichment in the solver AVBP. The ARC mechanism has been derived with the prediction of NOx and the addition of the chemiluminescent species OH∗. The fully automatic reduction of this mechanism is proven to capture well the experimental results and the effect of the enrichment level on the flame structure. The presence of OH∗ in the mechanism allows for more direct comparison with experiments and is the start of a discussion about the actual identification of the flame structure. Numerical simulation is also used in this case for the prediction of the NOx emissions and how it is affected by the hydrogen enrichment.
The second configuration consists in the reduction of 3 aviation fuels (conventional kerosene, sustainable aviation fuel (SAF) and high-aromatic content kerosene) described by 3-components surrogates. The reduction of each fuel is then used in canonical configurations of liquid droplets combustion. The discrete evaporation model implemented in AVBP allows to observe the effects of the preferential evaporation on the flame structure. Finally, the different fuels are compared to one another to identify their particularities and assess the benefits of the multi-component approach.
Keywords : chemical kinetics, ARC, combustion, hydrogen, kerosene, multi-component
|Politecnico Di Milano
|Laboratoire Réactions et Génie des Procédés