| Extrusion is the traditional manufacturing process for propellants. For good quality propellants the flow process of the raw materials is essential. So in the present study we have used Solidworks to establish the3D cylindrical channel models of the mono-perforated grain and multi-perforated grain, the process of propellant extrusion is simulated by POLYFLOW, and the flow process of the raw materials. Generally in extrusion process, mainly four factors affect the velocity and the pressure in the flow channel. They are the viscosity of the materials, the relaxation time of the materials, the inlet volume rate of materials and, the length of forming section. In the present study we have analyzed each factor independently. Results show that the flow rate in the channel increases gradually, the flow rate of the materials in the forming section is greater than it in the compression section, and becomes lower when near the wall; the pressure is substantially unchanged in the compression section and reduces gradually at the end of the compression section. In the extrusion process of the cylindrical mono-perforated grain, the pressure in the flow channel is dropping with the decrease of viscosity of the material, the pressure in the flow channel rising with the increase of relaxation time of the material and maintaining constant average flow rate. This indicates the pressure in the flow channel is directly proportional to the viscosity and relaxation time of the material. The pressure in the flow channel is also proportional to the length of the forming section. Due to this, we have also study the influence of forming section length on the pressure in the flow channel. It is found that when the length of forming section is30mm, the outlet rates simulated are homogeneous, and this length is considered as the best one. The result in this dissertation is feasible for process control, parameters determination and security analysis in propellant production process. |
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