Experimental study on the ignition and combustion characteristics of a magnesium particle in water vapor

Magnesium is of interest for underwater propulsion due to the superior ignition behavior of magnesium particles and the highly exothermic Mg-water reaction. In this work, the ignition and combustion characteristics of an individual millimeter-sized magnesium particle in water vapor were studied. In order to build an atmosphere of water vapor, an experiment system was established and validated by the experiments of magnesium particle in air. The ignition and combustion of a single magnesium particle were accomplished in a combustor filled with water vapor. The surface changes of the particle during the ignition and a steady-state vapor phase combustion were observed. Based on the data obtained, ignition mechanism was analyzed and ignition temperature was determined. The steady-state combustion of the sample was controlled by diffusion in gas phase, and a one-dimensional, spherically symmetric quasi-steady model was adopted to describe the process. The dependence of burning time on the diameter was investigated, and the conclusion that burning time is proportional to the square of the metal sample diameter was drawn.