Study on the Influence of Air Gap on the Thermal Response Violence of Pressed Polymer Bonded Explosive Charge in Slow Cook-Off Experiment

To study the slow cook-off response characteristics of the charges with HMX-based pressed thermobaric explosives influenced by charge air gap, experiments considering different clearance ratio were carried out. The corresponding thermal reaction process was simulated by a commercial software Fluent developed by America ANSYS Inc. The results indicated that the clearance ratio had a significant influence on the response violence of the charge. The response violence was burn or combustion while charge side clearance was less than 12.11%, but the response state turned out to be deflagration or explosion when the charge side clearance became larger. With a fixed charge condition, the critical charge side clearance ratio was approximately between 12.11 and 17.35%. The numerical simulation results indicated that the initial high temperature zone was located in the edges of the explosive columns in contact with the shell, which could shift toward to the center of the charge according to the increase of the clearance ratio. The shift process strongly depended on the contact conditions. The safety of pressed charge can be optimized by eliminating charge clearance.