Numerical simulations of TiO[formula omitted] production in a laminar coflow H[formula omitted]/Ar/TTIP diffusion flame: Comparison with experiments and parametric sensitivity study

Abstract

Metal-oxide nanoparticles are paving the way for the development of new materials, and flame spray pyrolysis (FSP) systems are gaining attention for their large-scale production. On an industrial level, precise control of particle characteristics is needed while guaranteeing an almost zero-emission process. In this context, computational fluid dynamic (CFD) simulations of nanoparticle production in flames are sought to optimize the design of FSP systems. In this work, numerical simulations of TiO nanoparticles production from Titanium(IV) isopropoxide (TTIP) are performed for a laminar coflow H/Ar flame as a first step towards this objective. To lower the CPU cost for 2-D simulations, reduced descriptions for the gas phase and for nanoparticles are considered. For H combustion, a 10-species kinetic mechanism is retained. Five different submechanisms are tested for the description of TTIP conversion into Ti(OH), considered as the TiO precursor. The description of the solid phase relies on a classical three-equation monodisperse formulation. The objective of this work is not to validate the considered CFD strategy, for which a more extensive database would be required, but to identify the most relevant processes for flame synthesis in a diffusion flame by performing a parametric sensitivity study. The originality of this investigation relies on the study of particle characteristics along an H laminar flame in a non-premixed configuration. Thus, the focus of the parametric study is on the effect on nanoparticle characteristics of: (1) diffusion processes of gaseous phase and nanoparticles; (2) aerosol processes. Numerical results are compared to experimental data in terms of conversion rate, volume fraction, and primary particle diameter along the flame height. Trends from the literature on the effect of aerosol process parameters are retrieved. Results highlight the key role of diffusion processes on nanoparticle production in non-premixed flames and the need for future improvements of TTIP conversion kinetics.