Preparation Of Variable Burning Rate Propellant With Core-shell Structure Based On Microfluidic Technology

Modern warfare continues to develop in the direction of long-range attack and efficient damage.The best way to improve the power of barrel weapons is to increase the initial velocity of the projectile.The variable burning rate propellant achieve a gradual release of energy when the propellant burns without increasing the pressure,so as to improve the projectile velocity.The variable burning rate propellant has become a bright spot in the field of propellant research.According to theoretical calculations in the literature,the core-shell structure variable burning rate spherical propellant can not only increase the loading density,but also achieve incremental energy release,which is an ideal type of change.and the variable burning rate propellant has not yet been reported on its preparation method.In this paper,microfluidic technology is used to prepare core-shell structure variable burning rate propellant.The main research contents are as follows:(1)Construction of a double co-flow microfluidic system suitable for the preparation of core-shell structure dropletsA double co-flow microfluidic system is designed to prepare oil-in-water oil-in-oil droplets.The double co-flow microfluidic system consists of three parts:a microfluidic chip,and the channel inner diameter is 0.41 mm:0.84 mm,the channel cross-sectional area ratio is 1:1;the transportation system,the constant flow pump and two injection pumps realize the precise transportation of the continuous phase and the dispersed phase,and the 1.5 mm inner diameter PTFE tube is connected to the chip to ensure stable droplet formation;a collection device for the dispersed phase.(2)Performance study of 3-methyl 4-nitrofuroxan(NMFO)as a curing agent for shell droplets The processing properties,rheological properties,thermal properties and mechanical properties of nitrocellulose-based composites with different NMFO additions were studied.The results show that the addition of NMFO can greatly improve the processing properties,rheological properties and mechanical properties of nitrocellulose.The processing viscosity of the composite material with the addition of 30%NMFO decreases,the impact strength is twice that of the raw nitrocellulose,reaching 55.6 Mpa,and the tensile elongation reaches11.6%,which is basically compounded with NC-NG with 40%NG addition.The mechanical properties of the materials are comparable.(3)Preparation and characterization of variable burning rate propellant with core-shell structureThe viscosity changes of the core-shell disperse phase fluid was studied.The effect on droplet formation was explored by adjusting the flow rate ratio and the number of capillaries.Scanning electron microscopy(SEM)and three-dimensional optical microscope were used to investigate the surface of the core-shell structure variable burning rate propellant.The morphology was characterized.The core-shell structure variable burning rate spherical propellant was prepared with a flow rate ratio of 1:25.The particle size distribution range is narrow,between 270?m and 310?m.The closed explosive test was carried out under the condition of a packing density of?=0.12 g/cm~3.The results show that the combustion of the core-shell structure variable burning rate propellant has a certain degree of combustion gradual increase,which improves the energy utilization rate.The method has the advantages of simple process,uniform particle size and controllable size of the prepared core-shell structure variable burning rate spherical propellant,which lays a foundation for its application.