Explosion limitExplosion pressure Burgess-Wheeler law Gas explosion Deflagration index a b s t r a c tThe explosion properties of alkane/nitrous oxide mixtures were investigated and were compared with those of the corresponding alkane/oxygen and alkane/air mixtures. The explosion properties were characterized by three parameters: the explosion limit, explosion pressure, and deflagration index. For the same alkane, the order of the lower explosion limits (LELs) of the mixtures was found to be alkane/oxygen ≈ alkane/air > alkane/nitrous oxide. In addition, the mixtures containing nitrous oxide tended to exhibit higher explosion pressures than the corresponding mixtures containing oxygen under fuel-lean conditions. The Burgess-Wheeler law was also observed to hold for the mixtures containing nitrous oxide.

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Despite unexpected explosion accidents caused by nitrous oxide have occurred, few systematic studies have been reported on explosion characteristics of flammable gases in nitrous oxide atmosphere compared to those in air or oxygen. The objective of this paper is to characterize explosion properties of mixtures of n-pentane, diethyl ether, diethylamine, or n-butyraldehyde with nitrous oxide and nitrogen using three parameters: explosion limit, peak explosion pressure, and time to the peak explosion pressure. Then, similar mixtures of n-pentane, diethyl ether, diethylamine, or n-butyraldehyde with oxygen and nitrogen were prepared to compare their explosion characteristics with the mixtures containing nitrous oxide. The explosion experiments were performed in a cylindrical vessel at atmospheric pressure and room temperature. The measurements showed that explosion ranges of the mixtures containing nitrous oxide were narrow compared to those of the mixtures containing oxygen. On the other hand, the maximum explosion pressures of the mixtures containing nitrous oxide were higher than those of the mixtures containing oxygen. Moreover, our experiments revealed that these mixtures differed in equivalence ratios at which the maximum explosion pressures were observed: the pressures of the mixtures containing nitrous oxide were observed at stoichiometry; in contrast, those of the mixtures containing oxygen were found at fuel-rich area. Chemical equilibrium calculations confirmed these behaviors.

This article reports experimental investigation of flame suppression ability of metallocenes. In this study, chromocene (CrCp2), manganocene (MnCp2), ferrocene (FeCp2), cobaltcene (CoCp2), and nickelocene (NiCp2) are used. The experiments are conducted by combusting a filter paper on which the metallocene is absorbed, by thermogravimetric measurement for metallocene/cellulose systems, and by burning a solution of the metallocene in n-pentane. Their suppression abilities are characterized with three parameters: extinction limit; activation energy of degradation; and burning rate of the liquid fuel. These experiments confirm that: (i) the metallocenes offer better flame suppression ability compared to ammonium dihydrogen phosphate, which is a conventional fire extinguishing agent; (ii) the metallocenes can exhibit the suppression effect not in solid phase but in gas phase; (iii) the suppression ability is in order of CrCp2 > MnCp2 > FeCp2 > CoCp2 > NiCp2, i.e., the metallocenes are arranged in order of the atomic number of their central metal. Although the metallocenes (except FeCp2) are chemically unstable, they are expected to be an excellent flame suppressant.

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