Thermal Response Characteristics of a Modular Charge Under Different Heating Rates

ABSTRACT This research investigates the heat transfer behavior and thermal reliability of a complex‐structure modular charge under thermal environments. A two‐dimensional transient cook‐off model is developed, incorporating a single‐step reaction mechanism for the combustible casing and a two‐step reaction mechanism for the multi‐perforated propellant. The model is validated through a miniature cook‐off test, where the predicted auto‐ignition delay times and temperature thresholds show good agreement with experimental results. On this basis, the cook‐off response of the modular charge is modelled under different heating rates. The results emphasize the role of both heat transfer from the external environment and the exothermic decomposition of energetic materials, which promote the charge initiation. As heating progresses, a feedback loop where propellant temperature rises, accelerating decomposition and releasing additional heat, triggers a cook‐off event. Given the cylindrical shape of the energetic component, the cook‐off location is a double annular ignition zone symmetrically distributed along the axial centerline. As the heating rate increases, the response region migrates both diagonally upward and outward, exhibiting an outward expansion trend. Under the relatively fast cook‐off conditions, auto‐ignition zones move to propellant regions adjacent to the inner wall corners of the casing. With changing heating rate, the auto‐ignition delay times under both relatively fast heating (1–10 K/min) and slow heating (1.8–7.2 K/h) show a power‐law trend. In all cases, the environmental heating rates considered show relatively limited influence on the modular charge's auto‐ignition temperature threshold.