In-situ quantification of spatiotemporally resolved particle concentration in iron powder combustion using holographic imaging

Abstract

In-situ quantification of particle concentration during the combustion of solid fuel powders is of importance for analyzing their combustion behaviors. Digital holography (DH) is applied here for studying iron powder combustion at high concentration. The performance of DH as a function of particle concentration is thoroughly studied with synthetic holograms. The detection efficiency is found to be ~85% when detecting dense particle fields (x × y × z = 5 × 5 × 10 mm3, 800 particles). Furthermore, calibration experiments are conducted to investigate the measurement accuracy of DH in combustion environments, in which a global depth-shift ~0.4 mm is observed. Finally, the spatial-temporal evolutions of the concentration in iron powder flames are systematically explored and analyzed. The statistical results indicate that the hot gas flow considerably changes the particle's spatial distribution and thereby affects the local concentration. Based on the reconstructed flame structure, three distinct stages of the iron powder flame along the reaction flow stream are identified.