CHARACTERIZATION OF COMBUSTION PROCESSES IN A WINDOWED FLASH TUBE OF AN M1020 IGNITION CARTRIDGE FOR 120-MM MORTAR

摘要

Understanding the ignition/combustion processes of pyrotechnic pellets and the product-gas pressurization and venting behavior inside the flash tube of an ignition cartridge is very useful for supporting model formulation and design improvements for mortar propulsion systems. This study provides the simultaneous visual records and pressurization data inside of the flash tube for characterizing the mass and energy fluxes discharged from the vent holes. Both black powder and MRBPS pellets were studied, showing no pellet fragmentation during the period of flash tube action. A windowed flash-tube test rig was designed and tested to simulate the actual flash tube combustion event with recorded pressure-time traces closely comparable to those from actual flash tube experiments. A high-speed video camera was used to capture the combustion and gas-dynamic behavior of products generated from pyrotechnic pellets. Observations included changes in the luminosity of product gases as they are compressed, as well as turbulent eddies in the downstream portion of the flash tube away from the primer end, indicating strong effect of pressure-wave induced gas accumulation. MRBPS pellets produced much higher peak pressures due to its generation of higher percentage of gas-phase combustion products. They also exhibited greater reproducibility than black powder pellets. Using the current vent hole pattern design, the discharge of product gases and particles from the flash tube into the granular bed is highly non-uniform and modification of the hole pattern should be considered.