Blast Characteristics

Blast Characteristics Accurate calculation of the magnitude of the blast wave from an exploding pressure vessel is not possible, but it may be estimated from several approximate methods that are available. 

For these and other purposes, blast-modeling methods are needed in order to quantify the potential explosive power of the fuel present in a particular setting. The potential explosive power of a vapor cloud can be expressed as an equivalent explosive charge whose blast characteristics, that is, the distribution of the blast-wave properties in the environment of the charge, are known. 

One of the complicating factors in the use of a TNT-blast model for vapor cloud explosion blast modeling is the effect of distance on the TNT equivalency observed in actual incidents. Properly speaking, TNT blast characteristics do not correspond with gas explosion blast. That is, far-field gas explosion blast effects must be represented by much heavier TNT charges than intermediate distances. 

Vapor cloud explosion blast models presented so far have not addressed a major feature of gas explosions, namely, variability in blast strength. Furthermore, TNT blast characteristics do not correspond well to those of gas-explosion blasts, as evidenced by the influence of distance on TNT equivalency observed in vapor cloud explosion blasts. 

TNT-equi valency methods express explosive potential of a vapor cloud in terms of a charge of TNT. TNT-blast characteristics are well known fiom empirical data both in the form of blast parameters (side-on peak overpressure and positive-phase duration) and of corresponding damage potential. Because the value of TNT-equiva-lency used for blast modeling is directly related to damage patterns observed in major vapor cloud explosion incidents, the TNT-blast model is attractive if overall damage potential of a vapor cloud is the only concern. 

Blystyfnat or Blytrinitroresorcinat (Lead Styphnate). Used as a cover charge for Pb Azide, as a primary initiator in bridge-wire detonators, and in various priming compns required to have certain blast characteristics... 

For optimizing pressure wave propagation FAE are ignited similar to nuclear-weapons in a defined distance above ground zero. So they often produce an atomic-mushroom-like smoke signature and blast characteristics making them look like mini Nukes . 

As a rule, fundamental investigations of combustion, combustion-detonation transition and detonation processes are conducted under spatially uniform conditions of combustible mixture pressure and temperature. Such research helps to find the main blast characteristics, to study chemical kinetic properties of combustible mixtures and to predict combustion development when zones of local pre-pressure and heatup of fuel are not observed. 

Contrary to the aforesaid, in the 52.9% H2 mixture, the blast wave attenuation was not recorded which can be explained by the excessive delay in fuel burning resulting from the expansion of the unbumed hydrogen together with the burn products. The blast characteristics data obtained in [1] for detonation should be supplemented with results from [4, 7, 8]. 

D.J. Lewis (a) Unconfined vapor cloud explosions. Progr. Energy Comb. Sci. 6(2), 151-165 (1980) (b) Estimating damage from aerial explosion type incidents. Problems with detailed assessment and an approximate method. Paper at Euromech-139, Aberysthwith, 1981 (c) Condensed phase explosions and their blast characteristics. Paper at Euromech-139, Aberysthwith, 1981... 

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