The Response of a Large-Caliber Granular Charge in Confinement to an In-Bed Thermal Initiation

Studies have been conducted to experimentally characterize the ignition and early-time combustion processes in a large-caliber propellant charge confined in a closed chamber and initiated by an in-bed hot ignition source. The experiments involve firings of live propellant charges contained in optically clear well-instrumented plastic chambers. There is a perforation through the chamber wall aligned with the ignition source. The studies simulate the circumstance when charge ignition occurs by a hot fragment which has penetrated the chamber wall and has rested inside the propellant bed. Results show that an in-house developed igniter composed of thermite powder (Al-Fe2O3) surrounded by ball powder contained in a cloth tube, initiated by electrical matches, is capable of providing proper ignition stimulus to the propellant charge. A perforation in the chamber wall, created by the penetration of a hot fragment, has a strong effect on the ignition process. Confinement of the charge is also an important factor in accelerating the ignition process. There is a large gradient in pressure and temperature from the ignition site to the chamber ends. The original document contains color images.