Abstract
To study the influence of tubular shell materials on the combustion of thermite, numerical simulations and experimental comparisons of the combustion efficiencies of thermite with PVC and stainless-steel shell materials were carried out. The thermal conductivity coefficient and heat radiation correlation coefficient of a shell material directly affect heat transfer during a heat-transfer process, that is, the lower the thermal conductivity and the higher the heat radiation reflectance coefficient, the lower the heat flux through the material and the less heat is lost. The experimental results show that compared with the stainless-steel tube material, the temperature distribution of thermite is more concentrated and the effect of melting through a steel target plate is more apparent when PVC is used as the shell material. The simulation results show that thermite in the PVC shell can produce a higher temperature, reaching 2200 °C at the loading port and 1700 °C on the steel target plate, which is maintained for 0.9 s. However, the corresponding maximum temperatures for the stainless-steel shell are only 2000 °C and 1500 °C, not yet reaching the melting point of the steel plate. The simulation results are consistent with the experimental phenomena. This work is of great significance for improving the design of thermite shells, enhancing performance, and guiding future combustion process research.
Highlights
Thermite, an energetic material with excellent combustion performance, releases lots of heat during the burning process[1,2,3] and can produce large amounts of energy
The formula shows that the total amount of heat transfer affecting the entire process mainly depends on the heat transfer coefficient (k), which is related to the thermal conductivity of a material (l) during heat conduction and the convective heat transfer coefficient (h) during convective heat transfer in this model
The red metal of the stainless-steel pipe body can still be seen, the thermite with PVC material shows almost no remaining effects. The reason for this is that the thermal conductivity of the stainless-steel material is much higher than that of the PVC material, and the heat radiation absorption ratio is high and the re ection ratio is low; under high-temperature conditions, heat and temperature are quickly transferred to the entire pipe body, rather than being lost, resulting in a bright red phenomenon being seen
Summary
Thermite, an energetic material with excellent combustion performance, releases lots of heat during the burning process[1,2,3] and can produce large amounts of energy. Gibson and Lowell et al.[18] examined the relationship between the ignition temperature and the thickness of the Al2O3 lm on the surface of the Al component in an Al/Fe3O4 system and concluded from experiments that the ignition temperature had a positive correlation with the thickness of the oxide lm; this laid a certain foundation for studying the effects of the degree of Al oxidation on thermite These studies theoretically analyzed how to improve the combustion effect based on the ignition mechanism. The effects of the shell materials on the combustion performance were discussed
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