Investigating spray flames for nanoparticle synthesis via tomographic imaging using multi-simultaneous measurements (TIMes) of emission

Abstract

Tomographic imaging using multi-simultaneous measurements (TIMes) of spontaneous light emission was performed on various operating conditions of the SpraySyn burner to analyse the flame morphology and its potential impact on spray flame pyrolysis. Concurrent instantaneous and time-averaged three-dimensional measurements of CH* chemiluminescence (flame front indicator) and atomic Na emission from NaCl dissolved in the injected combustible liquid (related to hot burnt products of the spray flame) were reconstructed employing a 29-camera setup. Overlapping regions of CH* and Na are presented using isosurface visualisation, local correlation coefficient fields and joint probability distributions. The instantaneous results reveal the complex nature of the reacting flow and regions of interaction between the flame front with the hot gases that originate from the spray stream. The averaged reconstructions show that the spray flames tested are slightly asymmetric near the burner exit but develop into symmetric bell-shaped distributions at downstream locations. The changes in the flame structure for different operating conditions are analysed in light of previous studies, helping in the better understanding of the nanoparticle synthesis process. Furthermore, the importance of using measurements from two views for significantly improved alignment of the burner based on the originally proposed procedure are discussed in light of the reconstructions. This is an important aspect since the SpraySyn is intended for use as a well-defined standardised burner for nanoparticle synthesis, which is being investigated numerically and experimentally across different research groups.

Combustion, Chemistry, and Carbon Neutrality

“…Species detected, e.g., by LIF, include Fe, FeO, SiO, AlO, TiO, and others . Laser methods can be difficult to apply in dense media with spray and particle clouds, but techniques such as LII, LIBS, and line-of-sight attenuation can be valuable for analyzing the process development and/or materials properties in situ . ,,,, Further diagnostic approaches include tomographic imaging with multiple simultaneous emission measurements, wide-angle light scattering for in situ determination of droplet and particle size distributions, and mass spectrometry to probe the particle growth. , To improve the understanding of flame synthesis reaction systems further, specific aspects have been investigated in depth, for example by studying atomization, droplet formation, and droplet–gas phase interactions, or by modeling the dynamics of SiO 2 nanoparticle synthesis using Reynolds-averaged Navier–Stokes (RANS) or large eddy simulation (LES). , …”

Direct numerical simulation of SpraySyn burner: Impact of liquid solvent

“…Unfortunately, such precursors are only available for a limited number of elements and are often based on metal chlorides, metal organics, or organometallics that are very expensive and/or toxic. 5 Hence, the focus is currently extended toward nanoparticle synthesis from spray flames, [6][7][8][9][10][11][12][13][14] allowing to overcome most of the problems listed above.…”