Impact of atomization on particle synthesis in spray flames

  Copyright: © WSA Influence of atomization on particle synthesis in spray flames

The spray flame synthesis of nanoparticles is significantly influenced by the atomization of the precursor solutions. The characteristic droplet and gas phase in the vicinity of the nozzle is an essential input condition for the formation of local synthesis conditions in the flame along the trajectories of particles during their formation. Thus, any change of the atomization will directly affect the particle properties. In this context, the nozzle design represents an essential degree of freedom, which can be used to gain a better understanding of the coupling of spray flame and particle formation mechanisms and, on this basis, to enable a targeted manipulation of particle properties in the long term.

The high importance of the nozzle geometry for spray flame synthesis was demonstrated by work in the first phase of the current project. It was revealed that an unsuitable atomization can lead to undesired flame pulsations. Since such pulsations prevent a rigorous investigation of the influence of spray characteristics on the process chain of particle formation, an adapted atomizer design was developed which significantly reduces flame pulsations. On this basis and with the help of numerical and experimental investigations, it was shown qualitatively and quantitatively that the particle size distribution can be significantly affected by the selected atomizer design. However, further research is needed to clarify whether and under which conditions a direct correlation between spray characteristics and particle properties exists. Furthermore, it is unknown how the responsible individual mechanisms of particle formation are influenced by the nozzle-dependent local synthesis conditions along the trajectory.

Based on this knowledge, this research project aims to provide a fundamental understanding of the influence of local synthesis conditions on spray flame mechanisms by means of a targeted variation of spray characteristics and high-resolution experimental and numerical methods. In this context, we will quantify how and to what extent the formation of local reaction and synthesis conditions is affected by individual nozzle-dependent atomization processes and subsequent droplet-flame interactions. On this basis, a fundamental understanding of the mutual sensitivity of particle formation mechanisms and spray flame mechanisms will be achieved. New atomizer designs will be introduced and used, which allow a systematic variation of the relevant spray flame mechanisms by a specific manipulation of the spray characteristics.