Numerical Simulation Research On The Single-screw Extrusion Process Of Propellant Substitute

The screw extrusion is one of the most important processes for solid propellant plasticization and molding. However, current research on the process of the screw extrusion is much inadequate, especially on the rheological parameters of the propellant material, which affects the process safety greatly. In this paper, the CFD software, POLYFLOW, and the numerical simulation method were adopted to investigate the rheological parameters of material of the screw extrusion process, which provides a scientific and effective reference to the technological process control and safety analysis.Firstly, according to the rheology state of a propellant in the screw extrusion process, the applicable numerical model was established by the use of the material parameters similar to the propellant. By modeling and analyzing on the ANSYS WORKBENCH simulation platform, the safety parameters distribution of propellant substitute, such as temperature, pressure, viscosity, shear rate, shear stress and viscous heating were attained, which all these parameters were under the condition of stable operation in the screw. The simulation results show that the material has relatively high pressure temperature and viscous heating and relatively small viscosity at the screw edge, where mixing and plasticizing severely, and where needs focus on the security control.Secondly, the variation in materials parameters of temperature, pressure, viscosity, shear stress and viscous heating under different rotation speed and inner surface temperature of screw was simulated by changing the screw practical process parameters (the screw rotation speed, the inner surface temperature and etc.). The results show that the screw rotation speed can be improved to increase the temperature and shear stress of materials, making mixed plasticizing better. The increase of inner surface temperature of screw can improve the temperature and liquidity of the material, which is conducive to the plasticizing. However, it is necessary to well control the upper limit of the rotation speed and the temperature to ensure the production safety.Finally, by comparing the axial pressure distribution curve and the viscous heating curve under different speed, and also different temperature of the material in the extruder by some existing literature with the simulated curves here, they show fairly good consistency. All the research shows that using POLYFLOW to simulate the rheological parameters of material of the screw extrusion process is feasible. This paper provides an effective method for the security analysis of screw extrusion process by numerical simulation.