Research On Large Co-rotating Twin-screw Extrusion Device For Energetic Materials

Solid propellants are energetic composite materials with specific properties.As an important part of the power of the Long March series of launch vehicles,solid propellants are continuously expanding their production needs.Therefore,it is urgent to increase research efforts on large twin-screw extruders for energetic materials.Based on the twin-screw numerical simulation and experimental prototype substitution experiments,this article conducts research on large twin-screw extruders based on the ideas of experimental prototype design simulation-experimental prototype experimental verification-similar amplification-large twin-screw extruder design simulation,and explore the safety and mixing performance of experimental prototypes and large twin-screw extruder during the mixing process.The main research contents of this article are as follows:(1)In order to ensure the safety and mixing performance during the screw mixing process,the functional sections of the screw of the twin-screw extrusion experimental prototype were designed,and the main parameters of the experimental prototype screw were determined.According to the each functional section of the screw,the SE element and KB element used in the mixing exhaust metering section of the experimental prototype were designed,and these two screw elements were used to form four different screw configurations.To explore the safety and mixing performance of the four screw configurations,the flow fields of the four screw configurations were numerically simulated.The pressure,maximum shear stress,maximum viscous power dissipation,weighted average shear stress,cumulative maximum shear stress,average reflow coefficient,and cumulative residence time of the flow field in the mixing process were obtained.On this basis,the T2 screw configuration with excellent safety and mixing performance is selected for subsequent substitute material experimental research.(2)Using the method of combining simulation analysis and experimental research to study the influence of screw speed on the mixing exhaust metering field,the average reflux coefficient and the cumulative residence time were used to evaluate the simulation results,and the test AL content method was used to evaluate the quality of extruded samples for substitute experiment.The results of simulation anALysis and experimentAL research showed that the distribution-mixing performance relationship of the slurry in three different screw speed flow channels was:30 rpm>40 rpm>20 rpm.(3)To achieve similar amplification from the experimentAL prototype to the large twin-screw extruder,a similar model of large twin-screw extruder was established through geometric similar amplification,volume similar amplification and constant shear rate similar amplification.The screw configuration,screw clearance and the main parameters of screw of amplified large twin-screw extruder were obtained.In order to explore the safety and mixing performance of the mainframe after amplification,the isothermal numerical simulation was carried out on the three-dimensional modeling and meshing of the large twin-screw extruder,and on the basis of this,it was compared with the numerical simulation results of the experimental prototype.The results show that the similarly amplified mainframe has considerable safety performance and distributed mixing performance compared with the experimental prototype,and the dispersion mixing performance of the mainframe was significantly better than the experimental prototype.(4)In order to explore the degree of influence of process parameters on the safety and mixing performance of the screw mixing process,section screw configuration after the mainframe amplification is selected,select the screw configuration of the mixing exhaust metering section enlarged by the large twin-screw extruder,combined with numerical simulation methods,and orthogonal experiments are used to explore.In the orthogonal test,the screw gap,screw speed and feed rate are selected as the test factors.Each factor selected corresponds to 3 levels,and the L9(33)orthogonal table is used.The results show that the degree of influence of three factors on screw safety and mixing performance:screw speed>screw clearance>feeding amount,screw speed has the greatest influence on screw safety and mixing performance.