Analysis Of The Extrusion Process Of Porous Propellant And Improved Design Of The Die

As extrusion has been widely used in propellant production,the process parameters are important for the quality of propellant.The time of extrusion has an effect on the usage of propellant doughs,the temperature of extrusion influences the flow rate of it.At the same time,the structure of the molding dies,especially the spacing of needles greatly affects the propellant web size.In order to find the relationship between the three parameters and the production process of propellant,the extrusion process of the porous propellant will be studied and the extrusion dies will be improved.After carrying out the fitting analysis based on the data of shear viscosity,shear rate and temperature,the Bird-Carreau model is chosen as the rheological model.The three-dimension models of dies used for propellants of different web size will be built by Proe software.Firstly,the Fluent software is used to simulate the transient extrusion process of propellants.The analysis of the pressure changes of some point in the propellant flow channel with extrusion time,indicates that it takes six seconds for the flow field to settle down.Compared to the initial flow field,the pressure,velocity and shear rate are more well-distributed in the steady flow field.Secondly,based on the fact that the state of propellant doughs will change at 80?,the heating temperature range is chosen from 80? to 95?.The simulation analysis of conjugate heat transfer between the module and propellant doughs,illustrates the pressure distribution in the flow channel of propellant doughs and the maximum deformation of needle frame.In addition,a series of extrusion tests are conducted to analyze the pressure in extrusion entrance and the offset distance of propellant web size.The multiple result of the two analytical methods comes into a conclusion that 95? is the best heating temperature for extrusion process.Finally,the properties and mechanics of selected needle materials are checked and it turns out the mould steel satisfies the strength requirements in the extrusion process.A quality evaluation system of the propellant web size is established.Based on the offset distance of propellant web size,the method combining numerical simulation and trial and error provides a reference to adjust the spacing of needles of the model of 21/19,so as to improve the structure of the mould.Finally the two test results are evaluated,it indicates that the quality of the propellants gained by the improved spacing of needles proves to be better and meets the demands of production requirements.