Direct spray combustion in a tubular flame burner toward fine particle synthesis

Abstract

A tubular flame burner equipped with a two-fluid nozzle for liquid precursor injection was developed and applied to the synthesis of fine particles. A tubular flame was established based on the axial spray of ethanol as a liquid fuel from the two-fluid nozzle. As the axial spray mixture from this nozzle merged with the tangential methane/air mixture from the tubular flame burner, a single flame front was established at the base of the burner. The flame structure was assessed by fabricating an optically accessible burner from quartz and OH*, CH* and C2* emissions were investigated using a spectrometer and ICCD camera. The results show that a lifted flame was formed when the tubular flame was outside the flammable range, whereas a stabilized flame was obtained with the tubular flame in the flammable range. These results indicate that flame stability was primarily determined by the tubular flame. Optimal particle synthesis also required the tubular flame to be in the flammable range. Gas phase temperature measurements indicated that the main flame could be well-stabilized while maintaining a high-temperature environment by using a fuel-lean tubular flame, even in conjunction with the direct injection of liquid fuels. Using this flame system, both titania (TiO2) and silica (SiO2) nanoparticles could be synthesized.