Molecular Dynamics Simulation Study On Pyrolysis Of NEPE High Energy Propellant

As a relatively high performance propellant,NEPE solid propellant is often used in rockets and missiles.The exploration of its mechanical properties,which directly affect the power of rockets,is essential.In this paper,a more reasonable core-shell nanoparticle model(Al/Al2O3/HMX/NEPE)is constructed using a molecular dynamics(ReaxFF-MD)simulation method based on the reaction force field,A more detailed molecular dynamics simulation is carried out using LAMMPS software to study and analyze the reaction mechanism of high-temperature pyrolysis,meanwhile,we also explore the effect of pressure on the combustion characteristics of NEPE solid propellant.The effect of pressure on the combustion characteristics of NEPE solid propellant was also explored.Through tracing the pyrolysis process and species evolution,the high-temperature pyrolysis reaction mechanism of the model was studied and analyzed,and the influence of pyrolysis mechanism and pressure on the combustion characteristics of NEPE solid propellant was further obtained.The overall oxidation process can be roughly divided into three stages:(1)pyrolytic warming stage(0-200 ps):the system temperature rises rapidly,the binder sublimates and breaks away from the nanospheres;(2)rapid reaction stage(200-400 ps):the temperature rises slowly,accompanied by the generation of a large number of intermediate products;(3)stable reaction stage(400-1200 ps):the system temperature rises smoothly and it was oxidised to small molecule products,such as H2,N2,etc.Due to the large amount of N2 and H2O produced in the high temperature pyrolysis system,the rapid accumulation of gases generates a large amount of heat,resulting in a rise in system temperature.From the study of different pressure systems,the oxidation process can also be divided into three segments:(1)component pyrolysis segment:the conversion of solid-phase macromolecules into gas-phase small molecules;(2)complex reversible reaction segment:the intermediates of the components after pyrolysis undergo complex reversible reactions and in dynamic equilibrium;(3)key exothermic segment:the key exothermic reactions continue,releasing a large amount of heat and causing the system temperature to the temperature of the system rises.Under different pressure regimes,the evolution of key species over time follows the same trend,rising at a certain rate and then gradually decreasing to zero,while the higher the pressure,the earlier the intermediate product reaches the inflection point and the longer the intermediate product exists in the system.The results of this paper will be useful for the formulation design of NEPE solid propellant,and it will help to improve the combustion performance,enhance the strength of China in solid rockets and missiles,which is of great value to reduce the gap between China and foreign military power.