Study Of The Reaction Mechanism Of Water Jets Impacting Solid Propellants At Low Pressure

There have been many accidents in the clean-up of HTPB composite solid propellant（referred to as HTPB propellant）by high-pressure water jet technology,and the existing experimental means are difficult to observe and record the reaction process,making the research process extremely challenging.In this paper,a water jet impacting solid propellant at low pressure is used as the background,and a HTPB propellant is selected as the object of study.Numerical simulations of the water jet impacting solid propellant are carried out using molecular dynamics simulation methods to investigate the interaction and reaction behaviour within the solid propellant at different water jet impact velocities.Based on the components in the HTPB propellant,the energy calculations of water molecules impacting HMX clusters,water molecules impacting Al clusters and HTPB/AP co-blended system were simulated respectively,and the results of reaction product information,reaction temperature change and component binding energy size change were obtained,which reveal the complexity and diversity of the reaction mechanism of water jet low pressure impacting solid propellant and provide reference for the safe treatment of solid propellant.（1）In the simulation of water molecules impacting HMX clusters,the maximum reaction temperature of the impacted HMX clusters can reach about 490 K when the speed of water molecules is 100 m·s-1,and the maximum temperature of the system can reach about 560 K when the speed is 300 m·s-1.In addition,the volume of the HMX clusters affects the temperature rise of the system,when the impact speed of the water molecules is certain,the larger the volume of the HMX clusters,the faster the temperature rise,the impact of the HMX molecules lead to chemical bond breakage,exothermic reaction.The reaction process appears C₄N₈O₇H₇and other carbon-containing compounds as well as the free state of H and O,etc.（2）The aluminium-water reaction releases a large amount of energy and the high speed impact of the water jet makes the aluminium-water reaction more violent and generates higher temperatures.The impact velocity of the water molecules largely determines whether the reaction is more complete.The greater the impact velocity,the greater the impact on the destruction of the oxide layer on the surface of the aluminium cluster,which in turn makes the reaction more violent and the greater the variety of reactants.As the aluminium clusters are flushed out,the aluminium water reacts fully and H₂,H₃O⁺and other substances are produced during the reaction.When the aluminium clusters are fully reacted,a large amount of hydrogen is produced,increasing the number of water molecules to around 4000 during the simulation,and the amount of H₂produced increases significantly.（3）When the HTPB composite solid propellant is subjected to water jet impact,the binding energy of the HTPB/AP molecular system in the propellant shows a complex variation in the temperature range of 600K to 1000K.As the temperature rises,the binding energy of the HTPB and AP system decreases and an exothermic reaction occurs,releasing more heat from the whole system and easily causing the propellant to burn and burst.