INFLUENCE OF ATOMIZATION AND SPRAY PARAMETERS ON THE FLAME SPRAY PROCESS FOR NANOPARTICLE PRODUCTION

Within the Flame Spray Pyrolysis (FSP) process for nanoparticle production, the effects of the liquid atomization process and the spray properties on the spray flame structure were studied by means of experiments and numerical simulations. The influence of precursor concentration variations on the spray droplet size distribution was studied for two different FSP nozzles. The resulting spray has been characterized in terms of drop sizes and velocities by means of Laser Diffraction and Particle Image Velocimetry. A mathematical model was carried out considering two-way coupling between the gas phase and the droplets. For the combustion model, the eddy dissipation concept model was employed, taking into account the effects of the vaporization of the droplets, chemical reaction mechanisms, and the chemistry-turbulence interaction. Experimental and numerical results are compared to validate the model and to study the potential influence of significant spray parameters on the FSP process. With increasing fuel/precursor viscosity from 0.55 x 10(-3) Pa.s to 3.72 x 10(-3) Pa.s an increase of 48% in the Sauter Mean Diameter (SMD) has been found. Furthermore, a bimodal droplet size distribution was found for the larger fuel/precursor viscosities. Large droplets may directly affect the flame structure and morphology while leaving the flame without complete evaporation and subsequent reaction thus influencing the resulting particle size distribution.