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

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.