S. A. Gubin

Determination of the limits of applicability of the chemical equilibrium model to the detonation products of gas mixtures

The applicability of the model of a chemically equilibrium mixture to describing the evolution of the composition of the detonation products during their expansion in three typical problems involving oxygen- and air-based combustible mixtures is examined. For the detonation products of oxygen-based mixtures, the model of a chemical equilibrium mixture provides a good agreement with the kinetic calculations for all practically important initial conditions for these problems. For air-based mixtures, initial conditions at which such an agreement is observed are determined.

Changes in the product composition during the detonation of an unconfined volume of a combustible mixture

For a model problem the solution to which describes the main features of changes in the parameters of the medium in the detonation of an unconfined gas mixture charge of in the air, direct numerical simulation, without of simplifying assumptions on changes in the composition of the mixture, was performed to study changes in the composition of the detonation products, determine the limits of applicability of the chemical equilibrium mixture model, and verify a previously obtained sufficient condition of applicability of the chemical equilibrium mixture model. The results of determining the limits of applicability of the chemical equilibrium mixture model previously obtained using an approximate method were confirmed.

An efficient approximate method for solving the problem of the establishment of chemical equilibrium in the products of explosion of gas mixtures

A method for calculating the changing composition of the explosion products in the case where the chemical equilibrium is absent but the bimolecular reactions are in quasi-equilibrium is developed. At each time step of numerical integration, the change in the total number of molecules in the system is calculated using a single differential equation written based on the selected kinetic mechanism. Then, the mixture composition is calculated under the assumption that the entropy of the mixture reaches its maximum value at a given internal energy, mass density, and molar mass. It is shown that the proposed method can be used to calculate the characteristics of explosive transformation processes after the induction period.

Equation of state of a supercritical fluid based on the Ornstein-Zernike equation

A numerical modeling of the thermodynamic properties of a fluid is performed using the method of integral equations. The predictions are compared with the results of MC and MD simulations. The problem of stability of the numerical solution is examined. The methods for correcting the correlation functions and for estimating their uncertainties are proposed.

Thermodynamic modelling of detonation H-N-O high explosives

The multiphase model of a detonation products based on the equations of state (EOS) of chemically reacting H-N-O systems which is used in the thermodynamic TDS code is presented. This model is applicable over a wide range of temperatures and density. This model consists of theoretically reasonable EOS for a multicomponent gas (fluid) phase. The calculations of detonation based on the presented model to be in good agreement with experimental data.

Application of a theoretical equation-of-state model for calculating the thermodynamic parameters of NH3-H2 binary mixtures based on a modified Exp-6 intermolecular interaction potential

The thermodynamic properties of pure ammonia and a NH3-H2 two-component mixture are calculated. The calculations are performed within the framework of the previously developed model of the equation-of-state (EOS) of a two-component mixture, which is also applicable to one-component gases. The model is based on a modified Buckingham’s Exp-6 potential for the polar ammonia molecule with allowance for dipole interactions. Comparison of the results of calculations within the framework of our EOS model and analytical EOS models proposed by other authors with the experimental data and the results of Monte Carlo simulations demonstrate that the proposed EOS model is a reliable tool for calculating the thermodynamic parameters of binary mixtures over a wide range of temperatures and pressures.

The multicomponent self-consistent Ornstein—Zernike application for CO2, N2, O2 shock Hugoniots simulation

A multicomponent equation of state with wide range of applicability is required to simulate shock waves in CxNyOz mixtures. This problem demands fine molecular interaction model due to competition between repulsion and attraction forces during shock compression process. A self-consistent Ornstein-Zernike application (SCOZA) based on distribution function integral equation theory can be used for it. The hypernetted-chain/soft core mean spherical approximation (HMSA) for SCOZA has been successfully applied to dense fluid systems with ambidextrous interactions. However, it was not designed to simulate mixtures, such as shock products of CxNyOz system. The convenient way to simulate multicomponent systems is the van der Waals one-fluid model (vdWlf). It has been shown, that vdWlf is not good enough for CO2 shock products at pressures higher, than 50 GPa. The multicomponent HMSA closure application based on partial version of the virial theorem has been offered in this paper. It is verified by molecular Monte-Carlo simulation at pressures up to 160 GPa with accuracy about 1–2%.