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Modeling High Explosive Reaction Networks

Modeling High Explosive Reaction Networks. Richard P. Muller 1 , Joe Shepherd 2 , William A. Goddard, III 1 1 Materials and Process Simulation Center, Caltech and 2 Graduate Aeronautical Laboratory, Caltech. What is ASCI?. DoE Project to Improve Simulation Science Stockpile Stewardship

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Modeling High Explosive Reaction Networks

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  1. Modeling High Explosive Reaction Networks Richard P. Muller1, Joe Shepherd2, William A. Goddard, III1 1 Materials and Process Simulation Center, Caltech and 2 Graduate Aeronautical Laboratory, Caltech

  2. What is ASCI? • DoE Project to Improve Simulation Science • Stockpile Stewardship • 3 National Laboratories (LANL, LLNL, SNL) • 5 Level One University Centers (Caltech, Stanford, Utah, Illinois, Chicago) • More Level-2 and Level-3 Centers

  3. Illustrations of the proposed facility

  4. Overview of virtual facility (VTF) • Computational Engines • Eulerian AMR solvers • Lagrangian solver for high fidelity solid dynamics • Fluid-solid coupling • Turbulence model development • PRISM • High resolution compressible CFD • Materials properties computations • Materials properties data base • Facilities for high performance computing • Facilities for high performance graphics • Python scripting interface drives all simulations

  5. ASCI Projects at the MSC • High Explosives: • Equations of State for Reactants and Products • Reaction Networks • Solids • Equations of State for Ta, Fe • Methodology • Improved parallelization for QM • Improved parallelization for MD • Interface to mesoscale

  6. Detonation of high explosives Solid dynamics Compressible turbulence Basic research initiatives Computational Science Computation of material properties

  7. What are High Explosives? • Most familiar one is TNT • Produce a great deal of energy, gas • CnH2nO2nN2n n CO + n H2O + n N2 • Oxygen balanced: no reactant O2

  8. High Explosives - Objectives • To make significant improvements in the state of the art in simulations of the detonation of high explosives • Three tracks • First principles • EOS of explosives, binders • Reaction networks • Reactive hydrodynamics using reduced reaction networks • Evolutionary • Extend existing engineering models • Incorporate into high resolution computations using AMR • Integrated simulation • Integration into framework for simulation • Model problem: corner turning problem or cylinder test

  9. +H +N2O +NO +OH +OH HCN CN NCO N2O +OH +NO +OH +OH +M HOCN HNCO NH2 N2 +O +H +H +NO +H +O +H +OH +NO HCN NCO NH N N2 +H +OH +N +H HCN HNCO NH2 HNO NO +H +M +OH +HCN +H2 HCN CN C2N2 +H HCN +CN Reaction Networks for High Explosives

  10. Additions to HE Reaction Kinetics • GRI Mechanism • Right physics for small (C2NO2) species, but no HMX, RDX, TATB • Include Melius (1990) Nitromethane Mechanism • Add in Yetter (Princeton) RDX Decomposition Pathways • Comb. Sci. Tech., 1997, 124, pp. 25-82 • Determine analogous HMX Pathways • Compute themochemical properties for all new species • Final mechanism: • 68 species • 423 reactions

  11. RDX Decomposition Steps

  12. HMX Decomposition Steps

  13. New Species Required in Mechanism HMX RDX HMXR RDXR HMXRO RDXRO

  14. Fit NASA Parameters to QM Calculations • Obtain thermochemistry from QM • Get QM structure at B3LYP/6-31G** level • Compute/scale frequencies • Obtain Cp, S, H from 300 - 6300 K • Fit to NASA standard form for thermochemical data:

  15. Heat Capacity Fit

  16. Entropy Fit

  17. Enthalpy Fit

  18. Testing the Mechanism • CV Calculations • T = 1500 K • P = 1-100000 atm • Species Profiles • Induction Times

  19. RDX/HMX Induction Times vs. Pressure

  20. RDX Combustion, P = 1000 atm

  21. HMX Combustion, P = 1000 atm

  22. Validation: Nitromethane • Nitromethane (CH3-NO2): liquid high explosive • Extensively studied • Compare to shock-tube data (Guirguis, 1985)

  23. Validation: Nitromethane

  24. Next HE Species • TATB and PETN Decomposition Steps • F-containing species important in binder • Same fraction of F and Cl as binder • Explore reactions of intermediates

  25. Important Unimolecular PETN Reactions

  26. Other Important Issues • Ideal gas law poor approximation • Underestimates volume • Overestimates density, reaction rates, factor of 15 (?) • Put JWL EOS in CV simulation: • Tarver [J. Appl. Phys. 81, 7193 (1997)] values:

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