Blast Processes in Liquid Combustible Mixture Bubbles

7 Blast Processes in Liquid + Combustible Mixture Bubbles 

In fact, the experimental data [29, 30] revealed that the liquid layer filled with bubbles containing combustible mixtures carmot be considered as a blast protective medium. The blast inhibiting character depends on the mixture composition, i.e., its heat production capability, reactivity, the liquid viscosity and volume concentration of bubbles containing the combustible mixture. 

The dangerous potential of two-phase systems (bubbles with combustible gas mixture-i-liquid) to maintain explosive mode propagation is manifest when the system is subjected to a blast wave with a significant amplitude. Thus, the explosion propagates through the water filled with bubbles containing 2H2 + O2 stoichiometric mixture when the system is subjected to a blast load of AF = 50-60 MPa. As this takes place, the bubble volume concentration should not be less than shown in Fig. 5.21. An increase in the liquid viscosity causes a decrease in the blast load that promotes the bubble detonation. A six-time increase in the liquid viscosity in comparison to water, results in nearly twice the decrease in the critical blast pressure. 

The aforementioned information shows that rather strict conditions are required for bubble detonation ignition in a HOM bubbles -i- liquid system. However, the bubble detonation probability should be taken into consideration when designing blast protective devices or analyzing blast accidents. 

The experiments [26] conducted for various combustion regimes of H2 + N2 + O2 mixtures in water-mechanical foams at water concentration of 10 kg/m have shown that even weak ignition of 2H2 + O2 contained in the foam cells initiates blast propagation with a 2,500 m/s velocity and a front pressure of 1.0-1.5 MPa. When the mixture is diluted to 2H2 + O2 + N2, the explosive front velocity reduces to 800-500 m/s. The velocity reduction has been recorded with the same mixture composition but with reduced the bubble size, i.e. with an increase of the heat transfer surface. 

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