Nonideal thermoequilibrium calculations using a large product species data base

Abstract

Thermochemical data fits for approximately 900 gaseous and 600 condensed species found in the JANAF tables (Chase et al. 1985) have been completed for use with the TIGER non-ideal thermoequilibrium code (Cowperthwaite and Zwisler 1973). The TIGER code has been modified to allow systems containing up to 400 gaseous and 100 condensed constituents composed of up to 50 elements. Gaseous covolumes have been estimated following the procedure outlined by Mader (1979) using estimates of van der Waals radii for 48 elements and three-dimensional molecular mechanics. Molecular structures for all gaseous components were explicitly defined in terms of atomic coordinates in Å (Hobbs and Baer 1992a). The Becker-Kistiakowsky-Wilson equation of state (BKW-EOS) has been calibrated near C-J states using detonation temperatures measured in liquid and solid explosives and a large product species data base. Detonation temperatures for liquid and solid explosives were predicted adequately with a single set of BKW parameters. Values for the empirical BKW constants α,β, κ, and θ were 0.5, 0.174, 11.85, and 5160, respectively. Values for the covolume factors, κ_i, were assumed to be invariant. The liquid explosives included mixtures of hydrazine nitrate with hydrazine, hydrazine hydrate, and water; mixtures of tetranitromethane with nitromethane; liquid isomers ethylnitrate and 2-nitroethanol; and nitroglycerine. The solid explosives included HMX, RDX, PETN, Tetryl, and TNT. Color contour plots of HMX equilibrium products as well as thermodynamic variables are shown in pressure and temperature space. Similar plots for a pyrotechnic reaction composed of TiH₂ and KClO₄ are also reported. Calculations for a typical HMX-based propellant are also discussed.