Simulation Of Droplet Formation And Solidification Process Of Spherical HMX Prepared By Microflow Control

Octogen(HMX)is currently the single substance explosive with the best comprehensive military performance.Due to its high sensitivity,it was limited.Spheroidization can effectively reduce its sensitivity.However,existing preparation methods have shortcomings such as high solvent consumption,uncontrolled preparation process,complex equipment,and poor safety.Using microfluidic technology to prepare spherical HMX single substance explosives can be used as a new preparation method.Due to the impact of external temperature,channel size,channel material properties and other factors on its production process,frequent chip replacement can also increase costs.Therefore,this article proposes to use the relevant simulation of two-phase flow,laminar flow,and dilute material transfer modules in COMSOL Multiphysics 5.6 software.By simulating and analyzing the formation process and solidification process of HMX droplets produced by microfluidic control.Guiding the construction of a microfluidic device,the feasibility of the simulation results was verified.The main research contents are as follows:(1)The HMX droplet generation process under the flow focused structure and coaxial copolymer structure chip was simulated.The physical factors such as viscosity,density,and interfacial tension of the HMX solution were set to ensure that the inner and outer pipe diameters under the flow focusing structure and coaxial copolymerization structure remained unchanged.The effects of the contact angle between the HMX solution and the glass tube wall and the two-phase flow rate ratio on droplet formation were studied.The results show that the change of continuous phase flow rate is directly proportional to the formation rate of HMX droplets and inversely proportional to the particle size of HMX droplets.The change of flow rate of the dispersed phase is proportional to the formation rate of HMX droplets and the particle size of HMX droplets.The formation of HMX droplets is closely related to the flow rate ratio of the continuous phase and the dispersed phase.The upper limit of the critical condition for the formation of droplets with coaxial copolymerization structure is that the flow rate ratio of the continuous phase and the dispersed phase is 24:1,and the lower limit is 20:65.The upper limit of the critical condition for the formation of droplets in the flow focusing structure is that the flow velocity ratio between the continuous phase and the dispersed phase is 78:1,and the lower limit is 10:11.(2)Simulate the resulting HMX droplet curing process.The output environment of HMX droplets is set,the principle of solvent exchange is used,the internal and external concentration difference is set for the solvent in the HMX droplet,and the solvent exchange process is replaced by a certain concentration solvent diffusion method,and the curing process of HMX droplets is studied.The results show that the volume reduction rate of HMX droplets is 30.38%,the area reduction rate in the two-dimensional section is 4.7282%,and the movement rate in the output environment of HMX droplets is 9.541 μm/s.(3)Construction of a microfluidic device for the preparation of spherical HMX.A microfluidic system with a coaxial copolymerization structure was designed for the preparation of HMX liquid droplets.The results showed that,based on the results of the above simulation,three batches of HMX microspheres with different particle sizes were successfully prepared by controlling the flow rate ratio of the continuous phase to the dispersed phase,and tested by scanning,XRD,and particle size distribution.The results were consistent with the rules which found in the above simulation research,verifying the simulation results.