UDC

536.46

Authors

V.V. Aksenov*, V.M. Yulkova*
*Northern (Arctic) Federal University named after M.V. Lomonosov
Corresponding author: Vasiliy Aksenov, address: Naberezhnaya Severnoy Dviny, 22, Arkhangelsk, 163002, Russian Federation; e-mail: vasvikaks@gmail.com

Abstract

The paper investigates experimentally and analytically the ignition process of dispersed magnesium in water vapor. In the experiment under controlled conditions of temperature and consumption of the oxidant (water vapor) the critical ignition temperatures of dispersed metal (fine magnesium cutting of 0.07 mm thick) existed. Its combustion limit was determined by a sharp increase of the ignition delay time near the critical temperature. Analytically the critical kindling temperatures of magnesium in water vapor were calculated on the basis of a mathematical model, according to which the dispersed magnesium was considered as an assembly of particles, uniformly distributed in the gas volume and represented a system with the volume source of heat. Their power level depended on the metal particles concentration and sizes. It was assumed that those particles were involved in the convective and radiative heat transfer with the environment in the presence of a chemical reaction of magnesium interaction with water vapor on their surface. Based on the known kinetics, determining the rate of the metal interaction with a gaseous oxidizer, the used mathematical model allowed us to make the quantitative calculations of critical kindling temperatures of the dispersed metal or macrokinetic constants by well-known experimental critical temperatures. The dispersed magnesium combustion in the water vapor is heterogenetic. If the intensity of the internal heat transfer between the dispersed magnesium and water vapor in the gasdispersed system is much less than the intensity of the system heat exchange with the environment, the equation defining the critical conditions of ignition of dispersed magnesium in water vapor enters the equation defining the critical ignition conditions of an individual sample in the oxidizer.

Keywords

ignition, induction time, dispersed magnesium, gaseous oxidizer

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