Multiscale Modeling of TiO2 Nanoparticle Production in Flame Reactors: Effect of Chemical Mechanism

For titanium dioxide (TiO2) nanoparticles manufactured in flame reactors, the precursor is injected into a pre-existing flame, exposing it to a high-temperature gas phase, leading to nucleation and particle growth. Predictive modeling of this chemical process requires simultaneous development of detailed chemical mechanisms describing gas-phase combustion and particle evolution, as well as advanced computational tools for describing the turbulent flow field and its interactions with the chemical processes. Here, a multiscale computational tool for flame-based TiO2 nanoparticle synthesis is developed and a flamelet model representing detailed chemistry for particle nucleation is proposed. The effect of different chemical mechanisms (i.e., one-step, detailed, flamelet) on the prediction of nanoparticle nucleation is investigated using a plug-flow reactor and a partially stirred tank reactor to model the flow field. These simulations demonstrate that particle nucleation occurs much later in the flame with detailed titanium oxidation chemistry, compared to one-step chemistry. Finally, a large-eddy simulation tool is developed to study the effect of precursor injection configuration on nanoparticle formation in turbulent flames.