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.

Tomographic imaging using multi-simultaneous measurements (TIMes) for flame emission reconstructions.

The method of tomographic imaging using multi-simultaneous measurements (TIMes) for flame emission reconstructions is presented. Measurements of the peak natural CH* chemiluminescence in the flame and luminescence from different vaporised alkali metal salts that were seeded in a multi-annulus burner were used. An array of 29 CCD cameras around the Cambridge-Sandia burner was deployed, with 3 sets of cameras each measuring a different colour channel using bandpass optical filters. The three-dimensional instantaneous and time-averaged fields of the individual measured channels were reconstructed and superimposed for two new operating conditions, with differing cold flow Reynolds numbers. The contour of the reconstructed flame front followed the interface between the burnt side of the flame, where the alkali salt luminescence appears, and the cold gas region. The increased mixing between different reconstructed channels in the downstream direction that is promoted by the higher levels of turbulence in the larger Reynolds number case was clearly demonstrated. The TIMes method enabled combustion zones originating from different streams and the flame front to be distinguished and their overlap regions to be identified, in the entire volume.