Design And Study On Co-rotating Twin-screw Extrusion Device For Solid Propellant

As the main power source of solid rocket engines and missile weapons,solid propellant plays an important role in aerospace and military fields and has a wide range of applications.With the rapid development of military technology,the demand for solid propellant for rocket engines has increased rapidly.At present,the propellant used in large rocket engines was mixed with intermittent device and processes,which requires more than ten pots or even dozens,time up to several days,and the consistency of propellant performance was difficult to meet the requirements.In developed countries,the use of twin-screw extrusion process to produce a variety of energetic materials such as solid propellants and explosives has been continuously and automated,significantly shortening the production cycle and improving the efficiency and safety of mixing.Therefore,this paper takes the solid propellant co-rotating twin-screw extruder as the research object,and studies the safety of the continuous mixing process and the mixing effect of the propellant.Based on the characteristics of solid propellant,this paper studies and designs the main device for continuous mixing of solid propellant,namely solid propellant co-rotating twin-screw extruder.The key structure and parameters of the barrel and twin screw that make up the extrusion device are determined.As an important part of the extrusion device,the twin-screw plays a key role in safety and mixing.To ensure the safety of mixing,it was determined that the minimum clearance between the screw and the barrel,and between the screw and the screw should not be less than 0.94 mm.In order to study the safety and mixing effect of propellant solid propellant mixing,twelve kinds of screw elements were designed according to the screw geometry.The non-isothermal numerical simulation of the flow field of the screw element was carried out by using POLYFLOW,and the pressure field,viscous heat generation field,temperature field,shear stress field,weighted average shear rate,cumulative residence time and average backflow coefficient were analyzed.A comprehensive evaluation method was established,and screw elements with excellent safety and mixing performance were selected.The screw mixing sections were combined with the preferred screw elements,and six screw combination configurations were designed.By simulation calculation,screw combination configuration excellent in safety and mixing performance were preferred.Under the premise of determining the screw configuration,the mixing clearance and process parameters were important links to ensure the safety of the mixing process and the mixing effect of the solid propellant.Therefore,the preferred screw combination configuration of the needle was used to study the effects of mixing clearance and process parameters on the safety of the mixing process and the mixing performance of the solid propellant.The simulation results of the screw element and screw combination configuration show that the reverse SE30L/50 element has the worst safety;the SE element has lower safety with the increase of the lead,but the mixing performance was improved,the KB element decreases with the misalignment angle.The number of kneading discs increases,the safety was improved,but the mixing performance was degraded.By comprehensive evaluation of the screw elements,SE30L/50 and KB 135/5/50 elements were not recommended.It is recommended to use KB45/5/50,SE30/50,KB45/.10/50,KB60/5/50 four elements.By analyzing and comparing the six combined configurations,the combination of Z1 and Z5 screw configurations have good safety and mixing performance,and were recommended.The simulation results of mixing clearance and process parameters show that the mixing clearance was increased,the safety was improved,and the mixing performance of the solid propellant worse.It was recommended to use the mixing clearance of 1.60mm.Under the premise of ensuring safety,the mixing clearance can be appropriately reduced.The increase in feed rate has little effect on safety,but it will make the mixing performance of the solid propellant worse.Therefore,when the process parameters are adjusted,a lower feed amount should be set for mixing.When the feeding amount is constant,the screw speed increases,the mixing performance becomes better,but the screw speed was too low and too high,and the safety was reduced.Therefore,when the process parameters are adjusted,the screw speed should be matched with the feeding amount to ensure safety.Under the premise,the screw speed can be appropriately increased.When the temperature of the barrel was increased,the temperature of the solid propellant was obviously increased,the safety was lowered,the dispersive mixing performance of the solid propellant was obviously worsed,and the distribution mixing effect was less changed.Therefore,under the premise of ensuring good fluidity of the solid propellant,the barrel temperature can be appropriately reduced.