The Simulation Study Of In-line Charge Firing Of A Certain Fuze And Its Insensitive Modification

The response of a fuze in cookoff environment is studied with insensitive munition technology,in order to improve the fuze safety under thermal stimuli through structural improvement.The Frank-Kamenetskii zero-order reaction model,which is based on the assumption of thermal explosion theory of explosives,is employed.The critical ignition temperature of JO-9159 in static detonation is calculated under certain ambient temperature.And the relationship between explosion time and heating rate is obtained when the energetic material is subjected to linear heating.The test methods of fast and slow cook-off in NATO standard are introduced.In order to analyze the thermal response of the charge within fuze under cook-off,the FLUENT software is used for numerical simulation,and the law of response is obtained.It is shown that the numerical simulation agrees reasonably well with reference test,which proves that the employed numerical model is credible.With the increase of heating rate,the temperature of shell at reaction increases,however,the ignition temperature decreases,and the explosion time shortens.Through comparing theoretical calculation and simulated explosion time of JO-9159 under different heating rates,it is concluded that the larger the heating rate,the smaller the error between theoretical result and the simulation result.At different heating rates,uneven heating source has little effect on the ignition of the explosive within fuze.When the projectile body is added outside the fuze body,the shell temperature at reaction and ignition temperature increases,and the explosion time is extended.In order to study the influence of shell material,explosive charge,heat-insulating material and pressure-relief structure on thermal vulnerability of fuze,various numerical simulations of fuze under cook-off is conducted using FLUENT software,and the influence of improved fuze structure on its safety is obtained.According to the simulation results,when the shell of fuze is composite material,such as Kevlar,the explosion time is extended.When the fuze is filled with insensitive explosives,and the explosion time at reaction is extended.When the fuze is filled with composite charge,where the outer layer is JB-9014 and the inner is JO-9159,the explosion time is between that using JB-9014 and JO-9159.It is found that the best insulation material is silicon aerogels.As the thickness of the insulation material increases,the explosion time of charge within fuze is extended gradually.The effect of the heat insulation material positioned outside of the fuze body is better than that positioned outside of the booster.When pressure relief hole is located at the bottom of the fuze body and air is filled in the hole,the explosion time is longer than that without pressure relief hole when the charge reacts.With the increase of the diameter of pressure relief hole,the explosion time increase.When pressure relief hole is located at the bottom of fuze body and filled with fusible alloy material,thermal vulnerability of the fuze is further reduced under cook-off.