Measurement and Modelling of Pyrotechnic Time Delay Burning Rates: Application and Prediction of a Fast Burning Delay Composition

Abstract

A predictive numerical model was implemented for a time delay based on the Si + Pb 3 O 4 system. The reaction kinetic parameters were estimated by comparing predicted surface temperature profiles with experimental data acquired with an infrared camera. Fair agreement between the modelled and measured burning rates was achieved. The burning rate is predicted to increase by 9.4 % for every 50 8C increase in ambient temperature. The core diameter was found to have a slightly larger impact on the burning rate than the wall thickness. The effect of using different wall thickness materials was evaluated and indicated that the burning rate is significantly influenced by the wall material when the thermal conductivity is increased and the volumetric heat capacity is reduced. The shape of the combustion front was found to widen with a long tail for materials with a low thermal conductivity and a narrower combustion front with a short tail for materials with high thermal conductivity. Preheating occurred for pyrolytic graphite-and diamond-based elements but no radial combustion was observed. The external heat transfer parameters (convection and radiation) did not affect the burning rate of the fast delay composition. It is concluded that the ambient temperature, volume fraction solids, molar heat of reaction, core and outer diameter are the factors that most significantly influence the burning rate of the Si + Pb 3 O 4 composition in long cylindrical elements.

Modeling of the explosion of pyroxylin or combustion of the pyrotechnic composition

“…The solid residue usually for pyroxylin is equal to from 0.1 to 0.5% by weight of the charge [17][18][19]. The specific heat of combustion of pyroxylin q = 2,5 MJ/kg, the combustion temperature is T = 2500 K, temperature of NC (normal conditions, the environment) T'=293,16, and P 2 = 101 kPa, R = 8.314 J/(kmol•K) -the universal gas constant [5,9,[20][21][22][23][24][25][26][27].…”

“…chem. (Online) International Journal of Biology and Chemistry 12, № 2, 105 (2019)Then the equation of balance taking into account the potential energy, the equation (34) the specific heat of combustion.Substitute the formula(24) in the (35) and obtain: m 1 it is possible to express via a ratio:m 3 =k*m 1(37)…”

A Benchmark Study of Burning Rate of Selected Thermites through an Original Gasless Theoretical Model

“…The Al/Pb 3 O 4 is an uncommon nanothermite mixture as it contains lead; however, some sectors such as mining continue to use this oxide [46,63]. The heat of reaction is remarkably high, but the vaporization temperature that limits the overall system temperature during combustion is the lowest of all considered aluminothermites, 1808 K, corresponding to the vaporization of PbO.…”

A Predictive Numerical Model of the Burning Rate of Pb3O4−Si Delay Composition

“…For pyrotechnic systems, Shidlovsky [17] suggested that the burning rate and ambient temperature have an exponential relationship. However, Montgomery et al [12] proposed that the combustion rate increases linearly with the environment temperature. In this study, the relationship between the burning rate and ambient temperature of the Pb 3 O 4 ÀSi delay composition was reached when the silicon content was varied from 10 % to 50 %.…”

“…High and low adiabatic reaction temperatures have been calculated for various Pb 3 O 4 ÀSi compositions [10,11]. Montgomery et al studied the influence of volume fraction solids, core and outer diameter temperatures, and the heat of reaction on the burning rate [12]. Ambient temperature and constituent content are two dominant factors affecting the burning rate.…”