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Volume 36 (1987)
- Issue 1_2 Pages 1-
Volume 36, Issue 1_2
Displaying 1-3 of 3 articles from this issue
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Toshisuke HIRANO, Takashi TSURUDA, Tetsuhiko HISANO, Ritsu DOBASHI, Ke ...1987 Volume 36 Issue 1_2 Pages 1-8
Published: 1987
Released on J-STAGE: June 04, 2012
JOURNAL FREE ACCESSTo explore the mechanisms of gas explosion-fire transition, the process of ignition of solid combustibles during a gas explosion was studied using a small rectangular combustion chamber of 8.5cm × 12cm × 9cm with a circular fragile part of tracing paper of 3cm in diameter on a side wall. The test piece of a solid combustible used in the experiments was a 2.5cm × 2.5cm square sheet of paraffin paper, which was placed in the combustion chamber filled with a methane-air mixture. The mixture was ignited by an electric spark at the center of the combustion chamber and subsequently a premixed flame propagated across the test piece. The pressure variation was recorded by using a pressure transducer, and the weight difference of the test piece before and after each experimental run was examined. The behavior of the test piece during the flame propagation and the subsequent outflow and inflow of gas through the opening yielded by breaking the fragile part was observed by high speed schlieren photography.
By comparing the recorded pressure variation and aspect of the test piece after each experimental run, it was found that the possibility of ignition was larger near the opening or at a lower flame velocity. This result indicates that the possibility of ignition depends mainly on the heat transfer to the test piece, especially the exposure period of test piece to the burnt gas. However, ignition did not occur during the exposure period but occurred after the air inflow started. This fact implies that ignition does not occur until the flammable gas generated by pyrolysis reaction mixes with the air inflow to yield a flammable mixture above the ignition temperature. Thus, it is assumed that the combustible mixture of air and pyrolysis gas ignited. Based on these results, the following processes for gas explosion-fire transition were inferred: heat transfer to solid combustibles; air inflow; mixing of the pyrolysis gas with air; ignite. The possibility of ignition depends largely on these phenomena.View full abstractDownload PDF (907K) -
Yoshimasa INOUE, Fujiroku YOSHIZAWA, Takehiro MATSUNAGA, Yoshiaki KANE ...1987 Volume 36 Issue 1_2 Pages 9-18
Published: 1987
Released on J-STAGE: June 04, 2012
JOURNAL FREE ACCESSA drop ball impact method have been applied for determining the sensitivity of oxidizer - red phosphorus contact mixtures. The direct impact of a sample by the ball gave lower 50% explosion height than other methods using indirect impact through a steel cylinder or striker etc. The energy (E50) of 50% explosion probability for the sensitive composition was expressed by the E50 for direct drop ball method and listed in the table.
Bromates, chlorates, or chlorites gave extremely sensitive contact mixtures with red phosphorus. Especially, silver chlorate - red phosphorus mixture showed the most sensitive in this work. The experimental of a series of metal peroxides - red phosphorus mixtures distinguished two distinct groups of different sensitivity. The mixture of sodium or potassium peroxide with red phosphorus was very highly sensitive, the second group included Zn, Ba, Ca, Sr, or Mg peroxide were observed forming less sensitive mixture and the energy (E50) of impact explosion was 0.32-0.88 J. The mixture of perchlorates or iodates with red phosphorus gave comparable sensitivity to the explosives alone, namely, Pb(N3)2, DDNP, PETN, RDX, or HMX etc.
The E50 was compared with the specified quantities of hazardous materials by the Japanese Fire Prevention Law and with the packing group of dangerous goods recommended by the United Nations.View full abstractDownload PDF (641K) -
Toshisuke HIRANO, Ichiroh NAKAYA1987 Volume 36 Issue 1_2 Pages 19-31
Published: 1987
Released on J-STAGE: June 04, 2012
JOURNAL FREE ACCESSThe requirements for fire retardant chemicals were discussed and the needs of studies to explore the fire retardation mechanisms are pointed out. Further, a survey of current understanding of fire retardation mechanisms is made.View full abstractDownload PDF (1201K)
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