Deflagration characteristics of freely propagating flames in magnesium hydride dust clouds

The flame propagation processes of MgH2 dust clouds with four different particle sizes were recorded by a high -speed camera. The dynamic flame temperature distributions of MgH2 dust clouds were reconstructed by the two-color pyrometer technique, and the chemical composition of solid combustion residues were analyzed. The experimental results showed that the average flame propagation velocities of 23 mu m, 40 mu m, 60 mu m and 103 mu m MgH2 dust clouds in the stable propagation stage were 3.7 m/s, 2.8 m/s, 2.1 m/s and 0.9 m/s, respectively. The dust clouds with smaller particle sizes had faster flame propagation velocity and stronger oscillation intensity, and their flame temperature distributions were more even and the temperature gradients were smaller. The flame structures of MgH2 dust clouds were significantly affected by the particle sinking velocity, and the combustion processes were accompanied by micro -explosion of particles. The falling velocities of 23 mu m and 40 mu m MgH2 particles were 2.24 cm/s and 6.71 cm/s, respectively. While the falling velocities of 60 mu m and 103 mu m MgH2 particles were as high as 15.07 cm/s and 44.42 cm/s, respectively, leading to a more rapid downward development and irregular shape of the flame. Furthermore, the dehydrogenation reaction had a significant effect on the combustion performance of MgH2 dust. The combustion of H2 enhanced the ignition and combustion characteristics of MgH2 dust, resulting in a much higher explosion power than the pure Mg dust. The micro -structure characteristics and combustion residues composition analysis of MgH2 dust indicated that the combustion control mechanism of MgH2 dust flame was mainly the heterogeneous reaction, which was affected by the dehydrogenation reaction. (c) 2023 China Ordnance Society. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY -NC -ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).