Time-resolved temperature measurements for inert and reactive particles in explosive atmospheres

The current study extends the understanding of the dynamics of the ignition process of fuel-air mixtures caused by laser-irradiated particles via the quantification of the particle heating process. Temperature measurements have been conducted under different irradiance in order to investigate the relationship between the absorption-emission properties of inert and reactive particles using emission spectroscopy. Temporal temperature information has been obtained at different boundary conditions for a range of carbon based powders including carbon blacks and graphites, as well as silicon carbide powders of different sizes. The particle size was found to have a significant impact on the heating process. Specifically, finer particles led to enhanced heating rates due to the reduced mass and thermal capacity, and the rate increase with irradiance for both inert and reactive particles was also quantified. The particle surface temperatures necessary to cause ignition of a surrounding charge were obtained and two different ignition regimes were observed. For non-reactive particles, the surface temperature plays the major role and for silicon carbide particles the ignition temperature was found to be 1200 +/- 200 K. By contrast, results obtained with reactive powders that feature similar times to ignition suggest that the temperature is not the only ignition criterion. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.