A statistical mechanical theory of chemically reacting multiphase mixtures: application to the detonation properties of PETN

• Published in: The Journal of chemical physics 1984-08, Vol.81 (3), p.1251-1263
• Main Author: REE, F. H
• Format: Article
• Language: English
• Subjects: Chemistry; Combustion. Flame; Exact sciences and technology; General and physical chemistry
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.447811

We present a new statistical mechanical theory of multiphase, multicomponent systems. It is based on Ross’s modification of the Mansoori–Canfield–Rasaiah–Stell hard-sphere variational theory and the improved one-fluid van der Waals mixture model. Next, the new theory and exponential-6 potentials that accurately reproduce shock wave data of major detonation-product species are used to compute the detonation properties of PETN (pentaerythritol tetranitrate). The results show satisfactory agreement with the experimental Chapman–Jouguet (CJ) data at initial densities ( ρ0) between 0.25 and 1.77 g/cm3. Small (≂9%) deviations which occur between the experimental and the theoretical CJ pressures at high ρ0 (>1.55 g/cm3) are attributed to time-dependent processes associated with formation of solid carbon which is theoretically present in detonation products. We suggest that some CJ pressure experiments might have finished too soon to experimentally observe late-time reactions involved in formation of solid carbon. However, a more definitive conclusion must await further effort to reduce experimental and theoretical uncertainties in the CJ pressure. We have also compared the theoretical CJ expansion adiabat at ρ0=1.77 g/cm3. The present theory predicts that both the adiabatic gamma −(∂ ln P/∂ ln V)s and the Grüneisen gamma exhibit peaks, along the CJ adiabat, at the density range where carbon atoms in gaseous detonation products start to condense. Comparison of our calculations with other theoretical EOS models is also discussed.