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Modeling High Explosive Reaction Networks

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Modeling High Explosive Reaction Networks Powered By Docstoc
					     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
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
Illustrations of the proposed facility
    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
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
Basic research initiatives

Detonation of     Solid dynamics   Compressible
high explosives                    turbulence




Computational                      Computation of
  Science                             material
                                     properties
What are High Explosives?
                                                 CH 3


•   Most familiar one is TNT              O 2N          NO 2



•   Produce a great deal of energy, gas
•   CnH2nO2nN2n  n CO + n H2O + n N2
                                                 NO 2

•   Oxygen balanced: no reactant O2
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
Reaction Networks for High Explosives
                                                                                      HCN
                                                                      +H
                   +OH                        +HCN                                          +H2
        HCN                        CN                      C2N2

                                                                           +H
                                                                                      HCN
                              +CN

                  +H                         +N2O
                                                                           +NO
                  +OH                         +OH
   HCN                         CN                              NCO                     N2O


                             +OH                                             +NO              +OH
       +OH


                  HOCN                        HNCO                     NH2                        N2
                              +H                          +H                         +NO
                                                     +M
             +O
                                                                +H
             +O                         +H                      +OH                        +NO
 HCN                     NCO                         NH                          N                      N2

                                        +H                     +OH
                                                                                                   +N
                        +H
         HNCO                       NH2                         HNO                    NO
                                                                             +M
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
RDX Decomposition Steps
             NO 2
                                           N
             N

                                     N             N
         N          N          O2N                       NO 2
   O2N                  NO 2



             N                             N



         N          N                N             N
   O2N                  NO 2   O2N                       NO 2



             N
                                     H2C       N

         N          N            2 H2C         N       NO 2
   O2N                  NO 2
HMX Decomposition Steps
                              NO 2

                          N                                          N
    O2N                                            O2N
            N                                            N

                                N                                            N
                                         NO 2                                     NO 2
                  N                                            N

            O2N                                          O2N

                          N                                          N
    O2N                                            O2N
            N                                            N

                                N                                            N
                                         NO 2                                     NO 2
                  N                                            N

            O2N                                          O2N



                                N
      O2N                                                      H2C       N
                N


                                     N
                                                         3 H2C           N       NO 2
                                            NO 2
                      N

                O2N
New Species Required in Mechanism
                                                                 NO 2
            NO 2
                                                             N
                                       O2N
            N
                               RDX
                                               N
                                                                                   HMX
                                                                   N
        N          N                                                        NO 2
                                                     N
O 2N                   NO 2

                                               O2N
                                                                   N
             N                           O2N
                                                   N                               HMXR
                               RDXR                                     N
        N          N                                                           NO 2
 O 2N                   NO 2                             N

                                                   O2N
                                                                   N
             N                           O2N
                               RDXRO               N
                                                                                   HMXRO
                                                                        N
        N          N                                                           NO 2
 O 2N                   NO 2                             N

                                                   O2N
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:
           Cp
                 a1  a2T  a3T 2  a4T 3  a5T 4
            R
           S                    a       a       a
               a1 ln T  a2T  3 T 2  4 T 3  5 T 4  a7
           R                     2       3       4
           H            a     a       a       a       a
                a1  2 T  3 T 2  4 T 3  5 T 4  6
           RT           2      3       4       5      T
Heat Capacity Fit
Entropy Fit
Enthalpy Fit
Testing the Mechanism

• CV Calculations
   – T = 1500 K
   – P = 1-100000 atm
• Species Profiles
• Induction Times
RDX/HMX Induction Times vs. Pressure
RDX Combustion, P = 1000 atm
HMX Combustion, P = 1000 atm
Validation: Nitromethane

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

• TATB and PETN Decomposition Steps
            NH 2
                                                     O2N
     O 2N
                   NO 2
                                                           O



                              O2N
     H2N           NH 2                                        O
                                        O

            NO 2                                                   NO 2
                                                 O

                                        O2N


• F-containing species important in binder
                                    F


                          F
                                            Cl
                              F


   – Same fraction of F and Cl as binder
   – Explore reactions of intermediates
        Important Unimolecular PETN Reactions
                  NO2
                                                      O.
                  O
                                                                                                  CH2                                CH2
                                                                        + NO2
                                                            O                                                                                          + NO2
                                      O
                        O
O                                                               NO2
                                                O
                            NO2       NO2                                                 O             O                     O            O.
          O
NO2                                                                                O2N                           NO2   O2N
                                                NO2
          NO2

                  O.

                                                C
                                                                                                   CH2
                                                            O         H2C      O
                                      O                                                                                                          CH2
                        O
O                                               O               NO2
                                      NO2                                                                                     O                        H2 C    O
          O                 NO2
NO2                                             NO2                                           O             O.          O2N
          NO2                                                                       O2N




                                                      CH2
              C                                                                                                  CH2

                            O                                          + NO3              O                                                            + NO3
    O                                                                                                                             H2 C          CH2
                                NO2                                                 O2N
              O
    NO2                                         O           O
              NO2                         O2N                     NO2
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:
        p  A(1  wR1 / V )e R1V  B(1  wR2 / V )e R2V  wE / V
                 Value                Fit #1   Fit #2
                 A (GPa)              1032.2   617
                 B (GPa)              90.57    16.93
                 R1                   6.0      4.4
                 R2                   2.6      1.2
                 w                    0.57     0.25
                 Eo (GPa cm3/cm3 g)   10.8     10.1

				
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posted:5/28/2012
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