engleski

Prediction of explosives performance by thermochemical calculations: Effect of equation of state

Thanks to progress in computers and numerical techniques, numerical modeling has become powerful tool in solving various problems in the field of energetic materials - from molecular modeling and geometry optimization, to performance and effect prediction. Thermochemical calculation, which is an important part of the modeling, solves thermodynamic equations between products species to find chemical equilibrium at a specified pressure and temperature, and combining with the Chapman-Jouguet detonation theory to calculate detonation properties of an energetic material. Thermochemical equilibrium codes (such are Cheetah, TDS, EXPLO5, etc.) are almost routinely used today to predict performance indicators of energetic materials, such as detonation velocity and pressure, specific impulse, force, etc., knowing only chemical formula, heat of formation, and density of an explosive. The biggest challenges of thermochemical calculation include mathematical description of the equilibrium state in reaction products as a multicomponent and multiphase reactive system, accurate description of the state of reaction products at extremely unusual p, V, T states, and evaluation of thermodynamic functions of reaction products at such state. The accuracy of prediction of explosive’s performance by thermochemical calculation depends mostly on the ability of an equation of state (EOS) used in the calculation to describe accurately the state of detonation/combustion products within rather wide range of pressures (i.e. density) and temperatures – from several tenths of GPa and several thousands of K to the atmospheric pressure and temperature. Various EOS have been proposed until now, ranging from semi-empirical BKW (Becker-Kistiakowsky-Wilson), to more fundamental fluid EOS such as JCZ3 (Jacobs-Cowperthwaite-Zwisler) and EXP6(Fried and Howard) EOSs, which account for the contributions to the pressure arising from intermolecular forces This talk will provide background of thermochemical calculations, reactive chemical equilibrium problem, and most frequently used EOSs of condensed and gaseous detonation products ; discuss challenges and key issues related to accuracy, shortcomings and limitations of individual EOSs ; and point out some research directions toward improving accuracy of thermochemical calculations.

thermochemical calculation; detonation; BKW EOS; JCZ3 EOS

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