Experimental and Computational Determination of Detonation Velocities

Transcription

1 Experimental and Computational Determination of Detonation Velocities Susanne Scheutzow LMU Munich, Department of Chemistry and Biochemistry, Energetic Materials Research,

2 Overview - Definition - Theory - Determination of the detonation velocity - Experiment - Experimental and computed values of EXPLO5 -Conclusion Flinders University,

3 p 1 Definition: Detonation is defined as a process of Taylor wave R CJ supersonic propagation of a chemical p 0 reaction through an explosive material. The chemical reaction occurs in a thin chemical reaction zone under the action of a shock wave. Detonation products chemical reaction zone unreacted explosive Champan-Jouguet plane shock front Figure 1. Detonation process Flinders University,

4 Theory: Pressure 1 Adiabatic shock of explosive 2 Adiabatic shock of detonation products 3 Rayleigh Line ρ 0 D = ρ ( D W ) p = ρ DW 0 p e e0 = ( p + p )( V V ) q p 2 CJ point 1 ln p γ = lnv S V p = p V S V p p = p V V 0 0 p 0 3 v 1 v 2 v 0 specific Volume Figure 2. Steady state model of detonation D = Detonation velocity W = Mass velocity q = Heat of detonation e = Internal energy V = Specific volume (V=1/ρ) γ = Polytropic exponent Flinders University,

5 Determination of the Detonation Velocity: - Time interval needed for the detonation wave to travel through a known distance - Measurement equipment should provide: - suitable velocity probes for detection - measurement of very short time intervals - Depending on the equipment, two methods can be used: - optical methods with high speed cameras - electrical methods with different types of velocity probes Flinders University,

6 Electrical Determination of the Detonation Velocity: - Velocity probes technique using EXPLOMENT-fo Up to 6 optical fibers - 5 independent timers - Optical fiber, 1 mm diameter, PE jacket overall thickness 2.2 mm explosive confinement (e.g. Cu tube) D D (a) optical fibers fiber jacket (b) Figure 3. Optical fibers Flinders University,

7 Technical Specification: - Max. distance between main unit and probes: up to 80 m - Max. distance between two neighboring probes: 10 m - Time accuracy: ± 0.1 µs - Velocity accuracy: better than 0.2 % - Detonating velocity range: up to m/s - Time interval measurement: 0.1 µs - 10 s Figure 4. Optical fibers Flinders University,

8 Experimental Part: Detonator: detonator -Ag 2 C 2 AgNO 3 Impact: 100 J, Friction: 5 N, ESD: 4 mj - PETN Impact: 3 J, Friction: 60 N, ESD: 190 mj explosive Cu tube (confined) 2 caliber optical fibers Figure 5. Set up for VOD Flinders University,

9 Experimental Part / Detonation Chamber KV 250: - Steel detonation chamber - Detonation: 250 g TNT - Performance tests: Additional measurement of detonation pressure, heat flow, mass velocity of detonation products, propagation of the shock wave using high speed cameras - Sensitivity tests: Slow cook-off test, critical diameter test - Stability test: Large scale long term stability Figure 6. Detonation chamber Flinders University,

10 Experimental Part / Set up: Figure 7. Set up Flinders University,

11 Experimental Part / VOD: Figure 8. Measurement equipment Flinders University,

12 Experimental Part / Set up: Figure 9. Set up Flinders University,

13 Experimental Part: Figure 10. High speed measurement, 4000 fps/0.5 ms Flinders University,

14 Flinders University,

15 Comparison of Detonation Velocities: Explosive Measured [m/s] a (Density [g/cm 3 ]) Calculated [m/s] Explo5 Time [µs] (Distance [mm]) Literature (Density [g/cm 3 ]) Picric acid 5130 (0.9) (20) 7400 (1.76) (TNF) 5263 (0.9) 3.8 (20) 4615 (0.9) 5.2 (24) 4181 (1.0) (23) 7000 (1.3) (21) HMX 6000 (1.0) (21) 9100 (1.95) 6250 (1.1) (20) 9523 (1.3) (20) RDX 7600 (1.0) (19) 8700 (1.89) 4617 (1.0) 4.5 (20) a ) ± 4 % error Flinders University,

16 Comparison of Detonation Velocities: Explosive Measured [m/s] a (Density [g/cm 3 ]) Calculated [m/s] Explo5 Time [µs] (Distance [mm]) Literature (Density [g/cm 3 ]) TNT 1919 (1.0) (19) 6930 (1.61) 2777 (1.0) 7.2 (20) 9130 (1.6) (21) PETN 7741 (0.9) (24) 8260 (1.76) 2238 (0.9) 20.1 (45) 8333 (1.2) (20) 7213 (1.3) (44) NGA (0.6) (23) 8895 (1.79) 8333 (0.8) (20) 6250 (1.0) (35) NGA (1.0) (20) 8750 (1.79) a ) ± 3 % error Flinders University,

17 NGA-1 Synthesis, Structure, Chemical and Energetic Characterization of 1,3-Dinitramino-2-nitroxy-propane, Thomas M. Klapötke, Alexander Penger, Susanne Scheutzow, Lukáš Vejs, ZAAC 2008, in press. Flinders University,

18 Conclusion: - Theory of error according to Gauss for picric acid, HMX, RDX: ± 4 % for VOD - Theory of error according to Gauss for TNT, PETN, NGA-1, NGA-2: ± 3 % for VOD - Problems encountered: - Measurement of experimental densities inaccurate (cf. EXPLO5 calculations) - Amount of booster affects measurement of VOD - Probes or optical fibers may tear apart thus giving a higher VOD or error - Solutions found: - Tamping with plasticine - Longer optical fibers Flinders University,

19 Acknowledgement Research group of Prof. Dr. T. M. Klapötke Prof. Dr. K. Karaghiosoff, Dr. B. Krumm, Xaver Steemann M.Sc., Alexander Penger, M.Sc., Stefan Huber Dr. Gary Chen, Pyros ARDEC, Picatinny Arsenal, NJ William H. Ruppert, Hughes Associates Inc.: Logistics & Advice Collaborations Dr. Betsy M. Rice, ARL, Aberdeen, MD: Theory Dr. Mark S. Johnson, ARL, Aberdeen, MD: Microtoxicity Dr. Gerhard Holl and Dr. Gerhard Heeb, WIWEB, Swisttal: Support, advise and many discussions Dr. Muhamed Suceska, Brodarski Institute, Zagreb, Croatia: development of EXPLO5 code Dr. Miloslav Krupka, OZM Research, Czech Republic: Development of new testing and evaluation methods for energetic materials Flinders University,

20 Thanks for your attention Flinders University,

21 Flinders University,

22 Flinders University,