Modeling of single droplet combustion phenomena in the flame spray pyrolysis process

Flame Spray Pyrolysis (FSP) is a powerful technique for synthesizing nanoparticles through combustion of exothermic liquid precursor-solvent solutions in a high-temperature flame. This study presents a comprehensive theoretical and experimental investigation of single droplet combustion (SDC) as a model system for understanding key processes in FSP. A one-dimensional, multicomponent droplet combustion model is developed, accounting for variable gas-phase transport properties as well as detailed heat and mass transfer in the liquid phase. To address the limitations of the classical d 2 -law, a variable transport property formulation is introduced for the gas phase. The model is validated against in-house experiments on pure fuel droplets (xylene and 2-EHA) under different gas Lewis numbers, and further extended to precursor-laden droplets containing Tin(II) 2-ethylhexanoate. Parametric studies varying liquid phase Lewis numbers, Arrhenius number, and Damköhler number are conducted to assess their impact on evaporation dynamics, precursor decomposition, flame structure, and microexplosion behavior. Simulations reveal that accumulation of precursor and its decomposition products near the droplet surface accelerates heating and vapor pressure buildup, triggering microexplosions. The model successfully reproduces key experimental trends, providing new insights into the coupled thermal, chemical, and transport mechanisms that drive nanoparticle formation in FSP.