The auto-ignition behaviors and risk assessments of double-base propellant containing different 1,1-diamino-2,2-dinitroethene particle sizes under rapid heating

An experimental investigation into auto-ignition behaviors and safety assessments of double-base propellant containing different 1,1-diamino-2,2-dinitroethene (FOX-7) particle sizes under high initial temperature condition has been carried out by using a rapid compression machine (RCM). The typical ignition and non-ignition cases upon heating by quasi-isentropic compression were identified through high-speed imaging and pressure evolution recording. The effects of FOX-7 particle size in three mixture samples on the auto-ignition and safety were analyzed in terms of critical ignition threshold, ignition delay times defined by high-speed images (IDT_I) and pressure evolution (IDT_P), and burning duration. Results show that the critical ignition temperature for each mixture decreases with increasing the pressure. At the same conditions, the Mix1 samples (with the largest particle size disparity) have the highest reactivity, which indicates that they are most easily excited to auto-ignition; while the Mix2 samples (with the smallest particle size disparity) have the lowest reactivity, elucidating that they are the insensitive to stimulus. In addition, the ignition models for three mixtures have been proposed to reveal the mechanisms of different FOX-7 particle sizes on auto-ignition behaviors at 2.0 MPa and 755.0 K.