Effect of flash-tube vent-hole patterns on the combustion product discharge rate

Understanding the ignition/combustion processes of pyrotechnic pellets and the product-gas pressurization and venting behavior from the flash tube of an ignition cartridge is very useful for supporting model formulation and design improvements of mortar propulsion systems. Results of the existing flash tube design show a highly transient and spatially non-uniform pressurization process produced by the combustion of pyrotechnic pellets. The non-uniform discharge of combustion products to the granular propellant bed can induce significant pressure wave phenomena in the projectile and mortar tube. This study examines the effect of flash-tube vent-hole size patterns in an effort to achieve a more uniform discharge of products. Results show that one can achieve a more uniform discharge mass flow rate into the granular bed by using non-uniform vent-hole sizes along the flash tube. This implies that an improved design of the flash tube could have the potential for significantly reduced pressure waves in the ignition cartridge of the 120-mm mortar system.