1. MU Gas-Condensed Phase Interactions: Flame- Surface Heat Exchange John E. Adams, Tamas Szabo, and Ali Siavosh-Haghighi Department of Chemistry University of Missouri-Columbia Columbia, MO 65211-7600 MURI Review, Picatinny Arsenal, October 27, 2004

2. MU Context: Burning Rates Continuum modeling of two-phase and three- phase combustion processes –One-dimensional –Homogeneous –Conserve mass, atomic species, energy within each phase –Match species, energy fluxes at interfaces –Surface regression through single-component evaporation –Multi-ingredient mixtures treated using a phenomenological pyrolysis law (CYCLOPS code)

3. MU Simplifications, Difficiencies Multi-component evaporation –Adsorbed/absorbed combustion products –Products of condensed-phase reactions Liquid-phase diffusion Real gases Complex liquid-phase behavior in a mixture Direct gas-surface reactions Missing experimental data

4. MU Simulations Gas-liquid surface collisions –Equilibrate liquid sample –Create interface(s) by expanding the simulation cell Analysis –Energy transfer to the surface –Trapping of colliding species –Evaporation at the liquid surface –T s dependences

5. MU Structureless Model System Lennard-Jones potential model –Generalizable via corresponding states “Light” gas, “heavy” surface species (ratio = 0.35) Hot gas, “cold” surface

6. MU Surface Contours

7. MU Final Energies (E i = 92 kJ/mol)

8. MU T s -Dependence of E f

9. MU T s -Dependence of Trapping

10. MU Real Energetic Material: Nitromethane Prototypical CHNO material Potential model from Agrawal, Rice, and Thompson Structureless impinging species (2/3 of CH 3 NO 2 mass) High-energy incident species, T s = 360 K

11. MU Surface Contour

12. MU Final Energies (E i = 92 kJ/mol,  i = 55°)

13. MU Next Steps Extend database of vapor densities as a function of T Evaluate dependence of energy transfer and trapping on the inclusion of internal degrees of freedom Describe system in terms of reactive potentials Investigate dynamics in the presence of temperature gradients