Comments on criteria for direct initiation of detonation

• Published in: Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences Vol. 357; no. 1764; pp. 3503 - 3521
• Main Authors: Lee, J. H. S., Higgins, A. J.
• Format: Journal Article
• Language: English
• Published: The Royal Society 01-12-1999
• Subjects: Blast Wave; Blasts; Cell Size; Chapman-Jouguet Detonation; Chemical energy; Combustion; Curvature; Detonation; Energy; Explosion; Explosives; Initiation; Initiation of Explosions; Pressure pulses; Shock fronts; Shock waves
• ISSN: 1364-503X; 1471-2962
• DOI: 10.1098/rsta.1999.0506

The current status of the direct initiation problem, where a powerful source drives a blast wave into an explosive gaseous mixture to generate a Chapman-Jouguet (CJ) detonation, is critically assessed. The current theories which are most successful in estimating the critical energy required for initiation are semiempirical in nature, in that they involve an experimentally determined length-scale (typically cell size) to characterize the explosive mixture. The eventual analytic theory of initiation should be based exclusively on the constitutive properties of the explosive. To date, attempts at a comprehensive theory of initiation have invoked quenching of the reaction front by curvature or unsteadiness of the blast wave. Simple analytic models of initiation as well as numerical simulations and experiments, however, all indicate that initiation near the critical regime is the result of a reacceleration of the blast wave from a sub-CJ minimum. Hence, the criterion for initiation must take into account the amplification of the blast wave due to coherent coupling with the chemical energy release. The effect of 'hot spots' is also shown to have a pronounced effect in reducing the critical energy required for initiation. These results suggest directions which future investigations can pursue toward a rigorous theory of direct initiation.