Flame propagation and particle participation behavior of ethanol vapor-induced explosions in non-uniform RDX dust systems with suspended and deposited particles

During RDX production, filtration, drying, and transport, volatile solvents such as ethanol may form a combustible vapor environment, while RDX particles coexist as suspended dust and particles accumulated near the bottom. During accidental explosions, the participation sequence of these particles and the effect of ignition location on explosion severity remain unclear. A gas-solid two-phase reactive flow model of a 5 L cylindrical vessel was developed using OpenFOAM's reactingParcelFoam and validated against ethanol/air and RDX dust explosion experiments. Central and bottom ignition cases were simulated to examine suspended particles, deposited particles, and their coexistence. Under central ignition at 500 J, suspended particles enhanced early flame propagation, with 0.01 and 0.02 g/L concentrations increasing the maximum pressure rise rate by 44% and 60%, and advancing peak time by 22% and 24%. Deposited particles, distant from the ignition source, contributed mainly in mid-to-late stages. Bottom ignition directly affected the near-bottom accumulated particles, converting their role from delayed responders to near-source enhancers; at 0.04, 0.08, and 0.16 g/L, peak pressure rose by 8.9%, 16.5%, and 24.1%. For the coexistence case (0.02 g/L suspended and 0.08 g/L deposited), the maximum pressure rise rate under bottom ignition reached 0.0305 MPa·ms⁻¹, while the peak pressure increased by 20.6% and the time to peak pressure was shortened by 69% relative to the pure-ethanol bottom-ignition case. These results indicate that ignition location strongly affects the participation timing of deposited RDX particles and the resulting explosion pressure response.