1 / 24

IGNITION OF ALUMINUM PARTICLE CLOUDS BEHIND REFLECTED SHOCK WAVES

IGNITION OF ALUMINUM PARTICLE CLOUDS BEHIND REFLECTED SHOCK WAVES. Kaushik Balakrishnan 1 , Allen L. Kuhl 2 , John B. Bell 1 , Vincent E. Beckner 1 1 Lawrence Berkeley National Laboratory 2 Lawrence Livermore National laboratory. ICDERS 2011, #329.

myrna
Download Presentation

IGNITION OF ALUMINUM PARTICLE CLOUDS BEHIND REFLECTED SHOCK WAVES

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. IGNITION OF ALUMINUM PARTICLE CLOUDS BEHIND REFLECTED SHOCK WAVES Kaushik Balakrishnan1, Allen L. Kuhl2, John B. Bell1, Vincent E. Beckner1 1 Lawrence Berkeley National Laboratory 2 Lawrence Livermore National laboratory ICDERS 2011, #329 Supported by U.S. Department of Energy and Defense Threat Reduction Agency

  2. INTRODUCTION • Al combustion is of interest • High energy content (7.4 Kcal/g) • Al added to explosives and propellants • Simulation of Al dispersion/combustion is challenging in explosion/shock flow fields • Ignition/burn models • Turbulent flow field • Two-phase modeling • Use of experimental data in models • Empirical ignition model

  3. IGNITION BY REFLECTED SHOCK WAVE • Boiko et al.’s experiments (Russia) • Krier/Glumac experiments (Univ. Illinois)

  4. IGNITION BY REFLECTED SHOCK WAVE wake RM • Wake convected into the particle cloud • Reflected shock interaction with particle cloud: Richtmyer-Meshkov instability • Clockwise/counter-clockwise vorticity • Particle cloud convolutes

  5. FORMULATION GAS PHASE CONTINUITY MOMENTUM ENERGY SPECIES PARTICLE PHASE CONTINUITY MOMENTUM ENERGY &

  6. FORMULATION: THERMODYNAMICS • Equation of state • Le Chatelier diagram (Kuhl, 2006) • Thermodynamic states computed using CHEETAH code • Thermodynamic equilibrium assumed for reactants and products • Quadratic curve-fits • uk(T) = akT2 + bkT + ck • K =fuel, oxidizer or products

  7. NUMERICAL METHODS - AMR • GAS PHASE: Higher-order Godunov method of Colella & Glaz, 1985; Bell et al., 1989 • PARTICLE PHASE: Godunov method of Collins et al., 1994 • ADAPTIVE MESH REFINEMENT (AMR) of Bell et al., 1989 • IMPLICIT LARGE-EDDY SIMULATION (ILES) • MASSIVELY PARALLEL SIMULATIONS (~1024 processors)

  8. EMPIRICAL IGNITION MODEL • INDUCTION PATAMETER f(x,t) • Experiments of Boiko et al., 1989 • Spherical Al particles and flakes • Gas temperature: 1700-2100 K • 1: Al spheres; 2: Al-Fe spheres; 3: Al flakes • A = 6.25x107 flakes; A = 4x107 spheres • E = 60 Kcal/mol

  9. EMPIRICAL IGNITION MODEL • Kuhl & Boiko curve-fit, ICT 41, 2010 • Tg < 2000 K • Roberts et al., 1993 experiment • Tg > 2000 K

  10. EMPIRICAL IGNITION MODEL • Boiko et al. experiments, 1989 reveal a cutoff particle cloud concentration is required to sustain burning μc(); μc()= ; b = 20 g/m3 • Gurevich et al. experiments, 1970 • Tign function of dp, λ and Cox • ∙∙exp(-0.85)

  11. SUMMARY: IGNITION MODEL • Additional equation for induction parameter, f(x,t) based on experimental data for ignition time delay • Particle size and gas temperature • Tign from Gurevich’s experiments • Accounts for particle size, oxidizer concentration and gas thermal conductivity • DEFINE:Ignition occurs if f > 1 and Tsolid > Tign • Cloud concentration included • μc() • Khasainov’s model used in the present study • Zhang’s model can be explored in future Initial: f = 0 Pre-ignition: 0<f<1 Ignition: f>1

  12. SIMULATION CONFIGURATION • Spherical Al particle cloud in shock tube; air everywhere • 3.2m x 0.4m x 0.4m; left: inflow; walls everywhere else • Shock wave initialized at x = 0.5m; 0.1 bar and 293 K for x>0.5m • 5 cm particle cloud (4-6 µm Al flakes) injected at x=2.75 m at 2.25 msec • 512x64x64 with 3 levels of refinement (ratio=2); ∆x3≈0.78 mm

  13. DIFFERENT SIMULATION CASES EFFECT OF INITIAL CLOUD DENSITY AND SHOCK MACH NUMBER

  14. RESULTS: log(ρs) • M = 4; ρs = 200 g/m3 • M = 4; ρs = 50 g/m3

  15. MOVIE: M = 4; ρs = 200 g/m3

  16. VORTICITY: M = 4; ρs = 200 g/m3 2.83 ms 3.52 ms 4.28 ms 5.37 ms • Vorticity due to wake: 1.2x105 sec-1 • Due to reflected shock: 4x104 sec-1 • Vorticity dependent on ρs and M

  17. MASS OF Al BURNED • Burning trend depends on ρs • 90% Al by mass burns • Present ignition model accounts for ρs • Wake-induced convolution/elongation of cloud for higher ρs • Increases surface area of cloud; hence more burning

  18. BURNING REGIONS Tg 200 g/m3 50 g/m3 Yair

  19. EFFECT OF M (ρs = 100 g/m3) • Higher M results in higher Tg behind reflected shock • Ignition occurs earlier • More Al by mass burns

  20. MASS AVERAGED Tsolid, K

  21. MASS WEIGHTED f • fMW = • Quantifies global cloud burning trend • ρs: peak and subsequent decay dependent on ρs • M: Earlier ignition for higher M • SIMILAR TO EXPERIMENTAL PHOTO-DIODE SIGNALS • ~250 µs burn time for 4-6 µm Al particles

  22. CONCLUSIONS • A new empirical Al ignition model is proposed • Ignition time based on Boiko et al.’s experiments • Ignition temperature based on Gurevich et al.’s experiments • Cloud concentration effect • RESULTS • ~90% Al (by mass) burns • Cloud density and M have profound effect • Mass-weighted f introduced

  23. RESULTS FROM A COMPANION PAPER • Shock Dispersed Fuel (SDF) charges • Investigate Al burning, mixing, vorticity, dissociation and ionization effects

  24. THANK YOU

More Related