The Experimental And Theory Research On Explosion Suppression In Flammable System

In this thesis, the experimental investigations, theoretical analysis and numerical simulations are carried out to study explosion suppressions in flammable gas. The studies are focused on mechanism of explosion suppression by inert dust cloud, and some ideas or approaches are put forward to industry explosion hazards mitigation and control. In different scale detonation-tubes, explosions are more or less suppressed by inert dust cloud and passive or active water mists, and characteristics of corresponding flow-field and relevant parameters are obtained experimentally. The results indicate that suppressant of NH4H2PO4 and NaHCO3 are more efficient than inert rock dust because of its reactivity. For inert suppressant, only if the particle concentration is larger than a critical value, can explosion be suppressed completely, otherwise, it may become strong again after passing through the dusty flow or will propagate steadily at a lower velocity. Especially, the critical curve is provided by the large-scale experimental data for explosion suppression by active mists, and it is important for engineering practice of explosion mitigation. Based on two-fluid model, coupling with 2-reaction and 19-reaction mechanism for H2/O2 /N2 and CH4/O2/N2, respectively, the model for explosion suppression by inert dust particles is established.,A numerical technique is developed to integrate the governing equations based on non-steady two-phase reacting flow with very disparate characteristic time. The explosion induced by a uniform hot reactive gas pocket and its suppression by inert dust particle cloud, are one- or two-dimensionally simulated numerically. It is shown that the transition process from accelerating combustion to detonation occurs only for suitable initial temperature of hot gas to establish a temperature gradient in cold reactive gas. Explosions are generally suppressed by inert particle cloud, i.e. the velocity of Shockwave and flame is reduced somewhat, because momentum and energy exchanging between gas and particle. Small particle have a stronger effect on explosion suppression than large ones. These results are consistent with experiment quantitatively or qualitatively. It is worth to mentioned that concentration of OH and H and O radical is found to be critical for explosion suppression, and more work is needed to understand the influence of free radicals on it.