Flame behaviors and severity parameters of hexogen cloud explosion in the combustion chamber

Hexogen (RDX) is a typical explosive raw material commonly used. The energy output of explosive dust explosion is higher than that of general industrial dust. Therefore, research on the energetic dust explosion is vital for military and disaster prevention. In this study, a two-dimensional semi-constrained combustor was established to numerically study the effects of inflow velocity, initial combustor temperature, and dust concentration on RDX dust explosion in a flowing state. The results show that the explosion process of flowing RDX dust in the combustion chamber has a critical initiation temperature that increases from 900 K to 3500 K with an increase in inflow velocity (50–150 m/s) at a dust concentration of 900 g/m³. Meanwhile, the explosion initiation time and initiation location of RDX dust delay with airflow velocity. At higher initial combustor temperature and transient dust concentration, the explosion flame surface transforms from a ‘plane’ to a ‘finger’ shape and then propagates to both sides. However, the flame spreads forward in a single direction at a low dust concentration (300 g/m³). As the initial temperature of the combustion chamber rises, the explosion initiation time and location decrease. At RDX dust concentrations of 300–1500 g/m³, the explosion overpressure rises significantly from 0.476 to 3.37 MPa, while the flame temperature increases slightly from 4000 to 4300 K, indicating the sensitivity of explosion overpressure to dust concentration is higher than that of flame temperature.