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A field explosion test of hydrogen-air mixtures

No. 120039. A field explosion test of hydrogen-air mixtures. Wakabayashi, K., Mogi, T., Kim, D., Abe, T., Ishikawa, K., Kuroda, E., Matsumura, T., Nakayama, Y., Horiguchi, S., Oya, M. and Fujiwara, S. Research Center for Explosion Safety,

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A field explosion test of hydrogen-air mixtures

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  1. No. 120039 A field explosion test of hydrogen-air mixtures Wakabayashi, K., Mogi, T., Kim, D., Abe, T., Ishikawa, K., Kuroda, E., Matsumura, T., Nakayama, Y., Horiguchi, S., Oya, M. and Fujiwara, S. Research Center for Explosion Safety, National Institute of Advanced Industrial Science and Technology (AIST) this talk 1. Introduction 2. Purpose 3. Explosion test ignited by explosives 4. Explosion test ignited by electric spark 5. Conclusion

  2. Introduction Hydrogen is widely expected to become a new clean source of energy for the next generation, hence the considerable focus on basic technology and equipment relating to the utilization, manufacturing, transportation, storage and supply of this substance. Hydrogen station

  3. Introduction Before now, many research results concerning the explosion of hydrogen-air mixtures were reported, and attempts were made to conduct a quantitative evaluation of the explosion strength and the explosion-safety [1-2], although experimental data of explosion of hydrogen-air mixtures with a volume of several hundred cubic meter (m3) are relatively scarce at present [3]. However, since hydrogen is categorized as a high risk gas easy to explode, it is important to take sufficient measures to guard against the explosion risk and thus supply hydrogen to the public safely. [1] Mizuta, Y. et al., The effect of the mixture composition on the explosion behaviour of hydrogen/air mixture, Proceedings of Kayakugakkai, 11-12 Nov. 2004, Matsuyama, Japan. [2] Saitoh, H, et al., A field experiment of hydrogen-air deflagration, Sci. Tech. Energetic Materials, 65, No. 4, 2004, pp. 140-146. [3] Groethe, M. et al., Hydrogen Deflagrations at Large Scale, Proceedings of 15th World Hydrogen Energy Conference, 27 June-2 July 2004, Yokohama, Japan.

  4. Purpose To evaluate the strength of explosion of the hydrogen-air mixtures initiated by explosives or electric-spark and the scale-effect of the explosion strength.

  5. Layout of the test site Setup for measuring instruments 100 m

  6. Blast measurement details ・Piezoelectric pressure sensor HM102A12 (sensitivity = 3.6 mV/Pa, linearity = 1 % full scale, resonant frequency > 500 kHz) HM102A07 (sensitivity = 14.5 mV/Pa, linearity = 1 % full scale, resonant frequency > 250 kHz) with signal conditioner (PCB Piezotronic, Inc) ・flush-mounted to a sharp-edged stainless steel disk ・located 1 m above the ground ・grease on sensor-surface to reduce the effect of radiation heat ・measurement position 10, 18, 30, 49 and 81 m from the firing position Experimental setup of pressure measurement ・Digitizer: LTT-480 (Lab. Technique Tasler Co., Ltd.) ・Digital delay pulse generator:BNC555(Berkeley Nucleonics Co., Ltd.)

  7. Test with 31 m3 tent by explosives ignition ・Cylindrical shape Diameter: 3.4 m Height: 3.4 m covered by a thin plastic sheet (0.05 - 0.3 mmt) ・Hydrogen concentration 52.9 vol.% (detonation velocity max) 28.7 vol.% (flame propagation velocity max) 21 vol. % (a lean mixture) two motorized fans, two hydrogen sensors ・Explosives for ignition: Composition C-4, 0.1 kg (initiation energy: approximately 625 kJ [4]) Experimental setup of tent [4] Swisdak, M. M. Jr., NSWC Technical Report, Explosion effect and properties part1-explosions in air, 1975, NAVAL SURFACE WEAPONS CENTER.

  8. Results (Test with 31 m3 tent by explosives ignition) Typical result of high-speed photography (52.9 % hydrogen by volume) 1000 fps 1 ms exposure 10000 fps 20 ms exposure

  9. TNT Results (Test with 31 m3 tent by explosives ignition) Blast wave histories with different concentrations measured at 10.6 m away from the firing position ･overpressure (Ps): amplitude of blast wave ・impulse (I): integration of positive phase of blast wave

  10. Results (Test with 31 m3 tent by explosives ignition) Scaled overpressure and impulse at different concentrations Where, R0= (E/p0)1/3, I; impulse, p0; the ambient pressure, C0; the speed of sound. E; energy of the hydrogen-air mixture, which is calculated based on the volume of hydrogen and air inside the tent (including energy of booster). [7] Nakayama,Y. et al., Kogyo Kayaku, 50, No. 2, 1987, pp. 88-92. [8] Kingery, C.N., and Pannill, B.F., BRL Memorandum Report No. 1518, 1964.

  11. Results (Test with 31 m3 tent by explosives ignition) High-speed photography images obtained during the explosion test with a mixture at 52.9 % hydrogen by volume 128 ms 428 ms 728 ms almost same value of C-J detonation velocity Propagation velocity of emission: 2170 m/s

  12. Test by electric spark ignition ・Rectangular shape covered by a thin plastic sheet (0.3 mmt) ・Hydrogen concentration 29.5 % by volume two motorized fans two hydrogen sensors ・Electric spark for ignition Experimental setup of tent

  13. Results (Test by electric spark ignition) Visualized by the flame reaction of NaCl aqueous solution Typical result of high-speed photography 1000 fps 1 ms exposure 3000 fps 100 ms exposure

  14. Results (Test by electric spark ignition) Blast wave histories with different volumes at same scaled distance (R/R0=0.6)

  15. Results (Test by electric spark ignition) Blast wave histories with different volumes at same scaled distance (R/R0=0.6) [3] Groethe, M., Colton, J., Chiba, S. and Sato, Y., Hydrogen Deflagrations at Large Scale, Proceedings of 15th World Hydrogen Energy Conference, 27 June-2 July 2004, Yokohama, Japan. [7] Nakayama,Y. et al., Explosions of composite propellants by ultra-high pressure initiation (2)TNT equivalences, Kogyo Kayaku, 50, No. 2, 1987, pp. 88-92.

  16. Conclusions We performed a field explosion test with a tent filled with various hydrogen-air mixtures and the overpressure of blast waves was measured using piezoelectric pressure sensors. The shape of pressure-time histories of blast waves depends on the difference in ignition method used (electric-spark or explosives). In the case of explosive ignition, it showed that the amplitude of the overpressure depends on the concentration of hydrogen. Overpressure also increased in accordance with an increased concentration of hydrogen. In the case of electric-spark ignition, the scaled overpressure was 10 times smaller than that of the explosives ignition. However, the scaled impulse was same order. Therefore, it seems reasonable to conclude that the scale-effect of the peak pressure and that of the impulse are different. From the viewpoint of the explosion-safety, it would be important to evaluate the strength of blast wave by the impulse.

  17. Acknowledgements This study is part of the research for a program on “Development for Safe Utilization and Infrastructure of Hydrogen”, conducted by the New Energy and Industrial Technology Development Organization (NEDO) and the Agency of National Resources and Energy in the Ministry of Economy, Trade and Industry (METI) of Japan.

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