Study On The Thermal Stability And Numerical Simulation For Series Of Pyrotechnic Composition With Strontium Nitrate

The accidents of pyrotechnic composition occur frequently, and have caused huge casualties and property loss during its use, storage, transportation and processing. How to reduce accidents and enhance the safety of pyrotechnic composition has become a hot issue in the research area of pyrotechnic composition.Based on the summary of the parameters and methods for evaluating the thermal stability of engertic materials, the thermal decomposition behavior for series of pyrotechnic composition with strontium nitrate is studied by SETARAM thermal analyzer. Activation energy for three kinds of red pyrotechnic composition is calculated by Kissinger method. The values of E for them are 264kJ?mol-1, 149kJ?mol-1 and 423kJ?mol-1 respectively. Then the critical temperature of thermal explosion(Tb) is dertermined. The values of Tb for three kinds of red pyrotechnic composition are 494℃, 456℃and 466℃ respectively. The results show that the thermal stability of Sr(NO3)2/Mg-Al pyrotechnic composition is the best, and the thermal stability of Sr(NO3)2/SrCO3/KClO4/Mg-Al pyrotechnic composition is poor.Under the different humidity level, the thermal decomposition behaviors for series of pyrotechnic composition with strontium nitrate are studied by SETARAM. The results show that the exothermic peak temperature decrease with the increase of humidity. According to the experiment data of thermal analyses under different humidity level, the relationship between temperature and mass loss is obtained. The higher the humidity is, the more mass of pyrotechnic composition lose. The mass loss of pyrotechnic composition increase as the temperature is raised. The thermal stability of pyrotechnic composition is the worst under the combinative effect of high temperature and high humidity.The results for the influence of moisture content on the thermal decomposition behavior of pyrotechnic composition show that the thermal stability for series of pyrotechnic composition with strontium nitrate increased slightly when the moisture content lower than 1%. And the combustion performance will be affected when the the moisture content greater than 1%. In order to improve the hygroscopicity for series of pyrotechnic composition with strontium nitrate, the strontium nitrate is coated. After coating strontium nitrate, the hygroscopicity of pyrotechnic composition is obviously decreased, and its thermal stability increase with different degree.The three-dimensional models of naked grain and paper packing grain are established by ANSYS software. The heated process of naked grain under different ambient temperature is studied, and the ignition temperature of the red pyrotechnic composition is 731 K, which is consistent with the calculated value from experiment data.The influence of packaging condition(without of package and steel package), size and increasing rate of temperature on the heated process of pyrotechnic composition is investigated. As the ambient temperature rises, the ignition delay period is shortened, and the ignition positions of paper packing grain with different size(120mm×60mm, 160mm×80mm and 200mm×100mm) is 14 mm, 28 mm and 54 mm repectively to the top of center of grain. In the same ambient temperature, the ignition position is 60 mm to the top of center of paper packing grain, and 18 mm for steel packing grain. The ignition temperature of pyrotechnic composition is not affected by packaging condition and size. In the same conditions, the SADT of paper packing grain is lower. With the increase of size, its SADT decrease, ignition delay period shorten, and the ignition position shift from center to the top of the grain. When the ambient humidity increased with 0.3K?min-1 and 5K?min-1, the ignition position of the paper packing grain is in its corner.In this paper, the heated processes of monocular fireworks with different charge are simulated. The simulation results show that the ignition temperature of black pyrotechnic composition is lower than the ignition temperature of red pyrotechnic composition. The ignition delay period for monocular firework of single charge with black pyrotechnic composition is 212 s, which is below the ignition delay period for monocular firework of layered charge. The heated process of 4×4 combinatorial fireworks is simulated. In the condition of ambient temperature of 500 K, the four corner monocular fireworks of 4×4 combinatorial fireworks are firstly ignited, and its SADT is 434 K. The SADT is below the SADT of monocular firework of layered charge. The ignition delay period for 4×4 combinatorial fireworks is 1218 s, which is lower than the value of monocular firework with simplified model.The innovation points of this paper include the influence of combinative effect of temperature and humidity on the series of pyrotechnic composition with strontium nitrate is firstly investigated. The ignition position, ignition delay period and SADT of combinatorial fireworks are also firstly determined by numerical simulation method.