Experimental and numerical study of a HMDSO-seeded premixed laminar low-pressure flame for SiO2 nanoparticle synthesis

Silicon dioxide nanoparticles are generated in a lean hydrogen/oxygen flat flame doped with small amounts of hexamethyldisiloxane (HMDSO) stabilized by a water-cooled sintered bronze matrix. The burner is housed in an optically-accessible low-pressure (3 kPa) chamber. Temperature fields were determined via multi-line laser-induced fluorescence (LIF) using added NO as target species. Gas-phase silicon oxide (SiO) was detected via laser-induced fluorescence (LIF) by exciting the weakly temperature-dependent rovibrational Q(11)(32) transition in the A-X (0,0) vibronic band system at 235.087 nm. Semi-quantitative concentration profiles as a function of height-above-burner (HAB) were obtained after exploiting the measured temperature fields and correcting measured LIF intensities for the temperature-dependence of the ground-state population and collisional quenching using measured effective fluorescence lifetimes. Particle sizes were determined as a function of HAB via molecular-beam sampling with subsequent particle mass spectrometry (PMS). The experimental data were used to develop a simple kinetics model of HMDSO combustion and SiO2 particle precursor formation with subsequent nucleation and particle growth in the H-2/O-2 flame. The model was incorporated in a CFD simulation to account for facility effects that arise from modified flow fields and heat transfer between the flame and the reactor chamber. (C) 2016 by The Combustion Institute. Published by Elsevier Inc.