Model and simulation of extrusion forming process of double-layer seven hole propellant

In order to investigate the effects of extrusion conditions on the extrusion pressure, flow velocity distribution, shear rate, and extrudate deformation of double-layer seven-hole gun propellant during the extrusion process, a dual layer seven-hole gun propellant inner channel model was established, and three-dimensional numerical simulations were conducted on the flow of propellant under different mold parameters using polyflow software. The results shown that: With the increase of the thickness ratio of the inner and outer layers, the flow velocity of the propellant gradually decreases, the flow velocity stability is better, the extrusion pressure gradient of the propellant gradually decreases, the peak shear rate gradually decreases, and the extrudate deformation becomes more and more serious; With the increase of the length of the extrusion section, the flow rate curve of the propellant is basically unchanged, the position of the maximum flow rate changes, the pressure difference at the entrance is obvious, the peak position of the shear rate changes, and the thickness of the external combustion layer becomes thinner after extrusion;With the increase of the shrinkage angle, the flow rate of the propellant, the extrusion pressure, the shear rate and the extrudate deformation do not change significantly. This has a great significance in guiding the process preparation of multi-layer variable burning rate propellant and mold design.